test: Cover visitDifferences node skipping

visitDifferences() is reached in production only through a file-static
populateFetchPack() in LedgerMaster.cpp, so the private hasLeafNode()
and hasInnerNode() it consults were untested. Four cases pin both
answers: only the nodes on a missing item's path, nothing against an
identical map, every node against a null map, and a callback stop.

The first case uses 64 shared items, so the shared leaves build inner
nodes of their own and whole matching subtrees exist to skip. A
finalize() helper seals each map first, since visitDifferences() returns
early while the root hash is zero, and getHash() is what seals it, by
unsharing such a map. Each call is wrapped in ASSERT_NO_FATAL_FAILURE,
which carries a gtest ASSERT_ failure out of a helper to its caller.

.cspell.config.yaml

@@ -103,6 +103,7 @@ words:
   - dearmor
   - decryptor
   - dedented
+  - dedup
   - deleteme
   - demultiplexer
   - deserializaton
@@ -344,6 +345,7 @@ words:
   - unambiguity
   - unauthorizes
   - unauthorizing
+  - undeserializable
   - unergonomic
   - unfetched
   - unfindable

.github/scripts/levelization/results/ordering.txt

@@ -62,6 +62,7 @@ libxrpl.tx > xrpl.protocol
 libxrpl.tx > xrpl.server
 libxrpl.tx > xrpl.tx
 test.app > test.jtx
+test.app > tests.libxrpl
 test.app > test.unit_test
 test.app > xrpl.basics
 test.app > xrpl.config

.github/workflows/reusable-clang-tidy.yml

@@ -123,13 +123,19 @@ jobs:
 
       - name: Fix style
         if: ${{ steps.files_changed.outcome != 'success' }}
+        # pre-commit installs every hook's environment, even for hooks that match
+        # no files, and node-based hooks need libatomic, which this image lacks.
+        # Exit code 1 just means hooks modified files or found issues.
+        env:
+          SKIP: prettier,cspell
         run: |
-          pre-commit run --all-files || true
+          git add --update
+          pre-commit run || [ $? -eq 1 ]
 
       - name: Generate git diff
         if: ${{ steps.files_changed.outcome != 'success' }}
         run: |
-          git diff | tee "${DIFF_FILE}"
+          git diff HEAD | tee "${DIFF_FILE}"
 
       - name: Upload clang-tidy diff output
         if: ${{ github.event.repository.visibility == 'public' && steps.files_changed.outcome != 'success' }}

.github/workflows/reusable-package-test-install.yml

@@ -95,11 +95,15 @@ jobs:
           apt-get update -qq
           apt-get install -y "./${PACKAGE}"
 
+      # Rocky Linux and AlmaLinux pick a mirror from a mirrorlist, and now and
+      # then get one that serves the repository metadata at a few hundred kB/s,
+      # which alone outlasts the job's timeout. dnf only abandons a mirror below
+      # 1000 B/s for 30 s, so raise that floor to fail over to the next one fast.
       - name: Install the RPM
         if: ${{ inputs.package_type == 'rpm' }}
         env:
           PACKAGE: ${{ steps.find.outputs.package }}
-        run: dnf install -y "./${PACKAGE}"
+        run: dnf install -y --setopt=minrate=1M --setopt=timeout=10 "./${PACKAGE}"
 
       - name: Run xrpld
         run: xrpld --version

API-CHANGELOG.md

@@ -35,6 +35,8 @@ Version 3.5.0 is not yet released.
 
 - `channel_authorize`: The `channel_id` field now returns an `invalidParams` error if the value is not a string. [#7582](https://github.com/XRPLF/rippled/pull/7582)
 - `channel_verify`: The `channel_id` and `signature` fields now return an `invalidParams` error if the value is not a string. [#7582](https://github.com/XRPLF/rippled/pull/7582)
+- `account_currencies`, `account_nfts`, `account_offers`: A request with more than one problem may now report a different one of them. An invalid `ledger_hash` or `ledger_index` is reported before an invalid or missing `account`. An invalid `limit` or `marker` is reported before `lgrNotFound` or `actNotFound`, and for `account_offers` also before `actMalformed`. A request with a single problem returns the same error as before. [#8561](https://github.com/XRPLF/rippled/pull/8561)
+- `deposit_authorized`: A `credentials` entry that is all zeros (for example `"0"` or 64 `0` characters) now returns a `badCredentials` error instead of looking up a credential that can never exist.
 
 ### Bugfixes in 3.5.0
 

BUILD.md

@@ -2,33 +2,12 @@
 | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | These instructions assume you have a C++ development environment ready with Git, Python, Conan, CMake, and a C++ compiler. For help setting one up on Linux, macOS, or Windows, [see this guide](./docs/build/environment.md).<br><br>These instructions also assume a basic familiarity with Conan and CMake. If you are unfamiliar with Conan, you can read our [crash course](./docs/build/conan.md) or the official [Getting Started][conan-getting-started] walkthrough. |
 
-## Minimum Requirements
+## Supported platforms
 
-For the hardware needed to run a node, see
-[System Requirements](https://xrpl.org/system-requirements.html).
-
-For the software needed to build xrpld, see the
-[environment setup guide](./docs/build/environment.md).
-
-## Operating Systems
-
-### Linux
-
-The Ubuntu Linux distribution has received the highest level of quality
-assurance, testing, and support. We also support Red Hat and use Debian
-internally.
-Our Linux CI tooling is distro-independent and uses a Nix-based environment, so it should be possible to build on other Linux distributions as well, although we have not tested them.
-
-### macOS
-
-Many `xrpld` engineers use macOS for development.
-The minimum supported version is macOS 15 (Sequoia).
-CI testing is done in macOS 26 (Tahoe), but the build defaults `CMAKE_OSX_DEPLOYMENT_TARGET` to 15.
-
-### Windows
-
-Windows is used by some engineers for development only, and is not recommended
-for production use.
+Building and testing are supported on Linux, macOS, and (best effort) Windows;
+see [Supported development platforms](./docs/build/environment.md#supported-development-platforms).
+Running `xrpld` is officially supported on Linux only;
+see [Requirements](./docs/install.md#requirements).
 
 ## Steps
 

CMakeLists.txt

@@ -42,7 +42,7 @@ if(is_gcc)
     # GCC-specific fixes
     add_compile_options(-Wno-unknown-pragmas -Wno-subobject-linkage)
     # -Wno-subobject-linkage can be removed when we upgrade GCC version to at least 13.3
-elseif(is_clang)
+elseif(is_any_clang)
     # Clang-specific fixes
     add_compile_options(-Wno-unknown-warning-option) # Ignore unknown warning options
 elseif(is_msvc)

CONTRIBUTING.md

@@ -332,7 +332,7 @@ This ensures that configuration changes don't introduce new warnings across the
 
 ### Installing clang-tidy
 
-See the [environment setup guide](./docs/build/environment.md#clang-tidy) for how to get clang-tidy.
+The [Nix development shell](./docs/build/nix.md) provides `clang-tidy` at the [tested version](./docs/build/environment.md#tested-compiler-versions).
 
 ### Running clang-tidy locally
 

RELEASING.md

@@ -34,7 +34,7 @@ so tools can filter them and protection rules can target `release/*` and `stagin
 - **Branches only move forward.**
   `develop`, `staging/X.Y.x`, and `release/X.Y.x` are never rewritten.
 - **Cherry-picking only goes from `develop` to a staging branch**,
-  for fixes that must get into a release after the code freeze
+  for fixes that must get into a release after the [code freeze](#release-candidates)
   (see [Emergency Fixes From `develop`](#emergency-fixes-from-develop)).
 - **Security fixes are prepared privately and published with the release that contains them**,
   so vulnerabilities are not disclosed prematurely.
@@ -49,6 +49,7 @@ develop                            staging/X.Y.x & release/X.Y.x
    │
    ├── Tag: X.Y.0-b1
    ├── Tag: X.Y.0-bN
+   │  (2 weeks before rc1: freeze on large changes starts)
    ├── Tag: X.Y.0-rc1 ───────────────┐ (branches created)
    │                                 │
    │  (development continues)        ├── Fixes
@@ -75,16 +76,20 @@ develop                            staging/X.Y.x & release/X.Y.x
 3. **Branches:** `staging/X.Y.x` and `release/X.Y.x` are created from `develop`
    at the commit tagged `X.Y.0-rc1`.
    The first RC also kicks off the QE process.
-4. **Code freeze:** No new features or unrelated changes are pulled from `develop`
-   into `staging/X.Y.x` or `release/X.Y.x`.
-   Only critical stabilization fixes go into the line.
-5. **No large changes on `develop`:** Until `X.Y.0` is [merged back](#merging-back-into-develop),
-   large changes (e.g., big refactors, moving or renaming many files, mass reformatting)
-   are not merged into `develop`,
-   so that fixes on the line and the merge back don't run into conflicts.
+
+### Freeze on Large Changes
+
+From two weeks before `X.Y.0-rc1` until `X.Y.0` is [merged back](#merging-back-into-develop),
+large changes (e.g., big refactors, moving or renaming many files, mass reformatting)
+are not merged into `develop`.
 
 ### Release Candidates
 
+After branching, the line is in code freeze:
+no new features or unrelated changes are pulled from `develop`
+into `staging/X.Y.x` or `release/X.Y.x`.
+Only critical stabilization fixes go into the line.
+
 1. Fixes are developed against `staging/X.Y.x`.
 2. When ready, a new RC is created on `staging/X.Y.x`,
    and `release/X.Y.x` is fast-forwarded to it.
@@ -106,7 +111,8 @@ one right after the other.
 2. `release/X.Y.x` is fast-forwarded to `staging/X.Y.x`,
    and the release is tagged on it.
 3. The release is immediately [merged back into `develop`](#merging-back-into-develop).
-   For a major-minor release, this lifts the freeze on large changes in `develop`.
+   For a major-minor release, this lifts the [freeze on large changes](#freeze-on-large-changes)
+   in `develop`.
 
 ### Merging Back Into `develop`
 
@@ -127,7 +133,7 @@ After the merge, `git log develop..<tag>` must be empty.
 ### Emergency Fixes From `develop`
 
 If a commit was merged to `develop`
-and needs to be included in a release after the code freeze:
+and needs to be included in a release after the [code freeze](#release-candidates):
 
 1. Create a PR that cherry-picks the commit onto `staging/X.Y.x`.
 2. Leave `develop` as it is, with no reverts.

cfg/xrpld-example.cfg

@@ -1360,6 +1360,39 @@
 #       Example:
 #           owner_reserve = 200000      # 0.2 XRP
 #
+#   gas_limit = <gas>
+#
+#       The gas limit is the maximum amount of gas that can be
+#       consumed by a single transaction. The gas limit is used to prevent
+#       transactions from consuming too many resources.
+#
+#       If this parameter is unspecified, xrpld will use an internal
+#       default. Don't change this without understanding the consequences.
+#
+#       Example:
+#           gas_limit = 1000000      # 1 million gas
+#
+#   bytecode_size_limit = <bytes>
+#
+#       The bytecode size limit is the maximum size of a WASM extension in
+#       bytes. The size limit is used to prevent extensions from consuming
+#       too many resources.
+#
+#       If this parameter is unspecified, xrpld will use an internal
+#       default. Don't change this without understanding the consequences.
+#
+#       Example:
+#           bytecode_size_limit = 100000      # 100 kb
+#
+#   gas_price = <micro-drops>
+#
+#       The gas price is the conversion between WASM gas and its price in drops.
+#
+#       If this parameter is unspecified, xrpld will use an internal
+#       default. Don't change this without understanding the consequences.
+#
+#       Example:
+#           gas_price = 1000000      # 1 drop per gas
 #-------------------------------------------------------------------------------
 #
 # 9. Misc Settings

cmake/CompilationEnv.cmake

@@ -9,13 +9,21 @@ include_guard(GLOBAL)
 # --------------------------------------------------------------------
 # Compiler detection (C++)
 # --------------------------------------------------------------------
-set(is_clang FALSE)
+# is_any_clang is true for both LLVM Clang and AppleClang. Their version numbers
+# and feature sets differ, so use is_llvm_clang or is_apple_clang when it matters.
+set(is_any_clang FALSE)
+set(is_llvm_clang FALSE)
+set(is_apple_clang FALSE)
 set(is_gcc FALSE)
 set(is_msvc FALSE)
 set(is_xcode FALSE)
 
-if(CMAKE_CXX_COMPILER_ID MATCHES ".*Clang") # Clang or AppleClang
-    set(is_clang TRUE)
+if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    set(is_any_clang TRUE)
+    set(is_llvm_clang TRUE)
+elseif(CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
+    set(is_any_clang TRUE)
+    set(is_apple_clang TRUE)
 elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     set(is_gcc TRUE)
 elseif(MSVC)

cmake/XrplCompiler.cmake

@@ -130,7 +130,7 @@ else()
         INTERFACE
             -Wall
             -Wdeprecated
-            $<$<BOOL:${is_clang}>:-Wno-deprecated-declarations>
+            $<$<BOOL:${is_any_clang}>:-Wno-deprecated-declarations>
             $<$<BOOL:${wextra}>:-Wextra
             -Wno-unused-parameter>
             $<$<BOOL:${werr}>:-Werror>
@@ -177,7 +177,7 @@ else()
     if(
         is_nix_compiler
         AND is_linux
-        AND is_clang
+        AND is_any_clang
         AND CMAKE_CXX_FLAGS MATCHES "stdlib=libstdc"
     )
         string(
@@ -204,7 +204,10 @@ if(voidstar)
             "Antithesis instrumentation requires Linux, aborting..."
         )
     elseif(
-        NOT (is_clang AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 16.0)
+        NOT (
+            is_llvm_clang
+            AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 16.0
+        )
     )
         message(
             FATAL_ERROR

cmake/XrplCore.cmake

@@ -296,7 +296,13 @@ if(xrpld)
         OUT_VAR rpcspec_instantiations
         VALUE_TYPE "::json::Value"
         VIEW_HEADER "xrpld/rpc/detail/JsonObjectView.hpp"
-        HANDLERS book_changes ledger transaction_entry
+        HANDLERS
+            account_currencies
+            account_nfts
+            account_offers
+            book_changes
+            ledger
+            transaction_entry
     )
     target_sources(xrpld PRIVATE ${rpcspec_instantiations})
 

cmake/XrplSanitizers.cmake

@@ -58,7 +58,7 @@ target_link_options(common INTERFACE ${sanitizers_linker_flags})
 # This module appends -fsanitize-ignorelist=<path> for Clang builds.
 # The ignorelist path contains CMAKE_SOURCE_DIR, so it must be set here, rather than in the Conan profile.
 # GCC does not support -fsanitize-ignorelist.
-if(is_clang)
+if(is_any_clang)
     set(ignorelist_path
         "${CMAKE_SOURCE_DIR}/sanitizers/suppressions/sanitizer-ignorelist.txt"
     )

cmake/XrplSanity.cmake

@@ -23,11 +23,8 @@ if(NOT is_multiconfig)
     endif()
 endif()
 
-if(is_clang) # both Clang and AppleClang
-    if(
-        "${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang"
-        AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 16.0
-    )
+if(is_llvm_clang)
+    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 16.0)
         message(FATAL_ERROR "This project requires clang 16 or later")
     endif()
 elseif(is_gcc)

cmake/XrplSettings.cmake

@@ -62,11 +62,11 @@ if(unity)
     set(CMAKE_UNITY_BUILD ON CACHE BOOL "Do a unity build")
 endif()
 
-if(is_clang AND is_linux)
+if(is_llvm_clang AND is_linux)
     option(voidstar "Enable Antithesis instrumentation." OFF)
 endif()
 
-if(is_gcc OR is_clang)
+if(is_gcc OR is_any_clang)
     include(ProcessorCount)
     ProcessorCount(PROCESSOR_COUNT)
 
@@ -125,7 +125,7 @@ else()
     set(use_mold OFF CACHE BOOL "mold linker, linux only" FORCE)
 endif()
 
-if(is_clang)
+if(is_any_clang)
     option(use_lld "enables detection of lld linker" ON)
 else()
     set(use_lld OFF CACHE BOOL "try lld linker, clang only" FORCE)

cmake/scripts/codegen/requirements.in

@@ -7,7 +7,7 @@
 pcpp>=1.30
 
 # Parser combinator library - used to parse the macro DSL
-pyparsing>=3.0.0
+pyparsing>=3.3.3
 
 # Template engine - used to generate C++ code from templates
 Mako>=1.4.2

cmake/scripts/codegen/requirements.txt

@@ -99,7 +99,7 @@ pcpp==1.30 \
     --hash=sha256:05fe08292b6da57f385001c891a87f40d6aa7f46787b03e8ba326d20a3297c6e \
     --hash=sha256:5af9fbce55f136d7931ae915fae03c34030a3b36c496e72d9636cedc8e2543a1
     # via -r requirements.in
-pyparsing==3.3.2 \
-    --hash=sha256:850ba148bd908d7e2411587e247a1e4f0327839c40e2e5e6d05a007ecc69911d \
-    --hash=sha256:c777f4d763f140633dcb6d8a3eda953bf7a214dc4eff598413c070bcdc117cbc
+pyparsing==3.3.3 \
+    --hash=sha256:928ae7e20211f3b6f3915a72f06a0cfd29ab9d24279dd6346b6b1a7146397d36 \
+    --hash=sha256:ece8c00a69cf01b45d0b1dedabb469c90d8caf996d4fda40f147627a122849a4
     # via -r requirements.in

conan.lock

@@ -3,7 +3,7 @@
     "requires": [
         "zlib/1.3.2#1cb806da49011867778ffb6ac7190fcb%1782392402.122708",
         "xxhash/0.8.3#681d36a0a6111fc56e5e45ea182c19cc%1782392402.420688",
-        "xrpl-rpc-spec/0.1.21#d536f87a2ae7d313452746cfa3ac4404%1790869005.122975",
+        "xrpl-rpc-spec/0.1.23#56e8946f5b3fb949a3732e1a51135ca2%1790977482.197086",
         "sqlite3/3.53.0#324ada52333108388a9a6108bfa96734%1782392403.185447",
         "soci/4.0.3#e726491a03468795453f7c83fc924a96%1782392402.679521",
         "snappy/1.1.10#968fef506ff261592ec30c574d4a7809%1782307151.633168",

conanfile.py

@@ -40,7 +40,7 @@ class Xrpl(ConanFile):
         "nudb/2.0.9",
         "openssl/3.6.3",
         "soci/4.0.3",
-        "xrpl-rpc-spec/0.1.21",
+        "xrpl-rpc-spec/0.1.23",
         "zlib/1.3.2",
     ]
 

docs/build/environment.md

@@ -4,6 +4,18 @@ This document explains how to set one up.
 
 [BUILD.md]: ../../BUILD.md
 
+## Supported development platforms
+
+- **Linux**: the [Nix development shell](./nix.md),
+  which provides the same toolchain CI uses on any distribution.
+- **macOS** 15 (Sequoia) or newer: the [Nix development shell](./nix.md),
+  or the system [Apple Clang](#macos-apple-clang).
+  CI runs on macOS 26 (Tahoe), but the build defaults `CMAKE_OSX_DEPLOYMENT_TARGET` to 15.
+- **Windows**: best effort, see [Windows](#windows).
+
+For the platforms supported for running `xrpld`,
+see [Requirements](../install.md#requirements).
+
 ## Tested compiler versions
 
 `xrpld` is built in the **C++23** dialect by default, so your toolchain has to
@@ -35,20 +47,16 @@ compiler building. Treat support for anything outside the table as best-effort.
 
 ## Required tools
 
-Besides a compiler, building `xrpld` requires:
-
-| Tool                                        | Minimum version |
-| ------------------------------------------- | --------------- |
-| [Git](https://git-scm.com/downloads)        | any recent      |
-| [Python](https://www.python.org/downloads/) | 3.11            |
-| [Conan](https://conan.io/downloads.html)    | 2.17            |
-| [CMake](https://cmake.org/download/)        | 3.16            |
+Besides a compiler, building `xrpld` requires
+[Git](https://git-scm.com/downloads),
+[Python](https://www.python.org/downloads/),
+[Conan](https://conan.io/downloads.html),
+and [CMake](https://cmake.org/download/).
+Building with `-Drust=ON` additionally requires a Rust toolchain,
+see [Rust](#rust).
 
 On Linux and macOS, the [Nix development shell](./nix.md) provides all of them
-(see below). On Windows they have to be installed manually.
-
-Building with `-Drust=ON` additionally requires a Rust toolchain, see
-[Rust](#rust). A default build does not, so it is not in the table above.
+at the versions CI uses, recorded in [`nix/check-tools/`](../../nix/check-tools).
 
 Once they are in place, verify that everything is installed and runnable with:
 
@@ -58,60 +66,19 @@ Once they are in place, verify that everything is installed and runnable with:
 
 ## Linux and macOS
 
-The **recommended way** to get a development environment on Linux and macOS is
-the Nix development shell. It provides the exact tooling used in CI — `git`,
-`python`, `conan`, `cmake`, `clang-tidy`, `clang-format`, and everything else —
-with a single command and without installing anything system-wide:
+Use the [Nix development shell](./nix.md):
+it provides the compiler and every tool CI uses,
+without installing anything system-wide.
 
-```bash
-nix --experimental-features 'nix-command flakes' develop
-```
+### macOS: Apple Clang
 
-On **Linux**, Nix also provides the compiler (GCC); on **macOS**, it provides
-Clang. If you instead opt to use your system-wide Apple Clang (via
-`nix develop .#apple-clang`), you need to manage its version yourself (see
-below).
-
-See [Using the Nix development shell](./nix.md) for installation and usage
-details, including how to select a different compiler and why we recommend Nix
-over a hand-maintained environment.
-
-### macOS: managing the Apple Clang version
-
-If you use your system-wide Apple Clang on macOS (via `nix develop .#apple-clang`),
-the compiler version is whatever your installed Xcode (or Command Line Tools)
-provides. The following command should return a version greater than or equal to
-the [tested one](#tested-compiler-versions):
-
-```bash
-clang --version
-```
-
-If you develop other applications using Xcode, you might be consistently
-updating to the newest version of Apple Clang, which will likely cause issues
-building xrpld. You may want to install and pin a specific version of Xcode:
-
-1. **Download Xcode**
-   - Visit [Apple Developer Downloads](https://developer.apple.com/download/more/)
-   - Sign in with your Apple Developer account
-   - Search for an Xcode version that includes the expected Apple Clang version
-   - Download the `.xip` file
-
-2. **Install and configure Xcode**
-
-   ```bash
-   # Extract the .xip file and rename for version management
-   # Example: Xcode_16.2.app
-
-   # Move to Applications directory
-   sudo mv Xcode_16.2.app /Applications/
-
-   # Set as default toolchain (persistent)
-   sudo xcode-select -s /Applications/Xcode_16.2.app/Contents/Developer
-
-   # Set as environment variable (temporary)
-   export DEVELOPER_DIR=/Applications/Xcode_16.2.app/Contents/Developer
-   ```
+You can also build with the system Apple Clang,
+installing the other [required tools](#required-tools) any way you like
+(or getting them from `nix develop .#apple-clang`).
+Its version is whatever your installed Xcode (or Command Line Tools) provides,
+so check that `clang --version` is at least the [tested one](#tested-compiler-versions).
+If several Xcode versions are installed,
+select one with `sudo xcode-select -s <path>` or the `DEVELOPER_DIR` environment variable.
 
 ## Windows
 
@@ -123,8 +90,7 @@ manually:
   "x64 Native Tools Command Prompt". CI configures CMake with the
   `Visual Studio 18 2026` generator.
 - [Git for Windows](https://git-scm.com/download/win)
-- Python, Conan, and CMake, at the versions listed in
-  [Required tools](#required-tools).
+- recent releases of Python, Conan, and CMake
 - a [Rust toolchain](https://rustup.rs) — only needed to build with
   `-Drust=ON`, see [Rust](#rust)
 
@@ -145,16 +111,5 @@ version.
 Everything else the Rust build needs on the CMake side comes from Conan along
 with the rest of the dependencies, so there is nothing further to install.
 
-## Clang-tidy
-
-`clang-tidy` is required to run static analysis checks locally (see
-[CONTRIBUTING.md](../../CONTRIBUTING.md)). It is not required to build the
-project. The version this project uses is listed in
-[Tested compiler versions](#tested-compiler-versions).
-
-On Linux and macOS, the [Nix development shell](./nix.md) provides that exact
-version out of the box — run it via `run-clang-tidy`. No separate installation
-is needed.
-
 [cpp23-support]: https://en.cppreference.com/w/cpp/compiler_support/23
 [packages.nix]: ../../nix/packages.nix

docs/build/nix.md

@@ -9,9 +9,7 @@ This guide explains how to use Nix to set up a reproducible development environm
 - **Reproducible environment**: Everyone gets the same versions of tools and compilers
 - **Matches CI**: The Linux CI runs in Docker images built from this exact Nix environment, and CI builds some macOS configurations in it as well
 - **No system pollution**: Dependencies are isolated and don't affect your system packages
-- **Consistent compilers**: The GCC and Clang shells use the same versions as CI
 - **Quick setup**: Get started with a single command
-- **Works on Linux and macOS**: Consistent experience across platforms
 
 ## Install Nix
 
@@ -27,13 +25,8 @@ From the root of the xrpld repository, enter the default development shell:
 nix --experimental-features 'nix-command flakes' develop
 ```
 
-This will:
-
-- Download and set up all required development tools (CMake, Ninja, Conan, etc.)
-- Configure the appropriate compiler for your platform:
-  - **Linux**: GCC (provided by Nix)
-  - **macOS**: Clang (provided by Nix)
-
+This downloads and sets up all required development tools (CMake, Ninja, Conan, etc.)
+and the compiler for your platform (see [Platform notes](#platform-notes)).
 The first time you run this command, it will take a few minutes to download and build the environment. Subsequent runs will be much faster.
 
 ### Platform notes

docs/install.md

@@ -10,6 +10,19 @@ and DNF on Red Hat-based distributions such as RHEL, AlmaLinux, and Rocky Linux,
 where `yum` is a symlink to `dnf`.
 To build from source instead, see [BUILD.md](../BUILD.md).
 
+## Requirements
+
+Linux is the only operating system officially supported for running `xrpld`;
+macOS and Windows builds are for development only.
+
+Any x86-64 Linux distribution with APT or DNF and glibc 2.31 or newer should work
+(see [How libc is handled](../nix/docker/README.md#how-libc-is-handled)).
+CI tests the packages on Debian 11–13, Ubuntu 20.04–26.04,
+RHEL (UBI) 9–10, AlmaLinux 9–10, and Rocky Linux 9–10.
+
+For the hardware needed to run a node,
+see [System Requirements](https://xrpl.org/system-requirements.html).
+
 ## Release channels
 
 Packages are published to four channels:

include/xrpl/basics/IntrusivePointer.h

@@ -86,12 +86,15 @@ public:
         requires std::convertible_to<TT*, T*>
     SharedIntrusive(SharedIntrusive<TT> const& rhs);
 
-    SharedIntrusive(SharedIntrusive&& rhs);
+    // noexcept so move_if_noexcept moves rather than copies, which NodePathStack's path_ vector
+    // relies on when it relocates. The body is a std::exchange on a raw pointer, which is what
+    // makes the noexcept honest.
+    SharedIntrusive(SharedIntrusive&& rhs) noexcept;
 
     template <class TT>
         requires std::convertible_to<TT*, T*>
-    SharedIntrusive(
-        SharedIntrusive<TT>&& rhs);  // NOLINT(cppcoreguidelines-rvalue-reference-param-not-moved)
+    // NOLINTNEXTLINE(cppcoreguidelines-rvalue-reference-param-not-moved)
+    SharedIntrusive(SharedIntrusive<TT>&& rhs) noexcept;
 
     SharedIntrusive&
     operator=(SharedIntrusive const& rhs);
@@ -529,6 +532,22 @@ staticPointerCast(TT const& v)
     return SharedPtr<T>(StaticCastTagSharedIntrusive{}, v);
 }
 
+/**
+ * Statically cast an intrusive pointer, moving out of it.
+ *
+ * Spelling the parameter as `SharedIntrusive<TT>&&` binds rvalues only and
+ * leaves lvalues to the `const&` overload above.
+ *
+ * @param v the pointer to cast, left empty afterwards.
+ * @return a pointer of the requested type to the same object.
+ */
+template <class T, class TT>
+[[nodiscard]] SharedPtr<T>
+staticPointerCast(SharedIntrusive<TT>&& v)
+{
+    return SharedPtr<T>(StaticCastTagSharedIntrusive{}, std::move(v));
+}
+
 template <class T, class TT>
 SharedPtr<T>
 dynamicPointerCast(TT const& v)

include/xrpl/basics/IntrusivePointer.ipp

@@ -47,7 +47,7 @@ SharedIntrusive<T>::SharedIntrusive(SharedIntrusive<TT> const& rhs)
 }
 
 template <class T>
-SharedIntrusive<T>::SharedIntrusive(SharedIntrusive&& rhs)
+SharedIntrusive<T>::SharedIntrusive(SharedIntrusive&& rhs) noexcept
     : ptr_{std::move(rhs).unsafeExchange(nullptr)}
 {
 }
@@ -55,7 +55,7 @@ SharedIntrusive<T>::SharedIntrusive(SharedIntrusive&& rhs)
 template <class T>
 template <class TT>
     requires std::convertible_to<TT*, T*>
-SharedIntrusive<T>::SharedIntrusive(SharedIntrusive<TT>&& rhs)
+SharedIntrusive<T>::SharedIntrusive(SharedIntrusive<TT>&& rhs) noexcept
     : ptr_{std::move(rhs).unsafeExchange(nullptr)}
 {
 }

include/xrpl/basics/KeyCache.h

@@ -1,10 +1,15 @@
 #pragma once
 
 #include <xrpl/basics/TaggedCache.h>
-#include <xrpl/basics/base_uint.h>
 
 namespace xrpl {
 
-using KeyCache = TaggedCache<UInt256, int, true>;
+/**
+ * TaggedCache in key-only mode, holding no value per key.
+ *
+ * @tparam Key the key type to remember.
+ */
+template <class Key>
+using KeyCache = TaggedCache<Key, int, true>;
 
 }  // namespace xrpl

include/xrpl/basics/MathUtilities.h

@@ -39,6 +39,31 @@ checkedSub(std::int64_t a, std::int64_t b) noexcept
     return a - b;
 }
 
+/**
+ * Multiply two signed 64-bit integers, returning std::nullopt when the exact
+ * mathematical product is not representable in std::int64_t.
+ */
+[[nodiscard]] constexpr std::optional<std::int64_t>
+checkedMul(std::int64_t a, std::int64_t b) noexcept
+{
+    using L = std::numeric_limits<std::int64_t>;
+
+    if (a == 0 || b == 0)
+        return 0;
+
+    if (a > 0)
+    {
+        if (b > 0 ? a > L::max() / b : b < L::min() / a)
+            return std::nullopt;
+    }
+    else if (b > 0 ? a < L::min() / b : b < L::max() / a)
+    {
+        return std::nullopt;
+    }
+
+    return a * b;
+}
+
 static_assert(checkedAdd(0, 0) == 0);
 static_assert(checkedAdd(1, -1) == 0);
 static_assert(checkedAdd(-5, 2) == -3);
@@ -81,6 +106,53 @@ static_assert(
     !checkedSub(std::numeric_limits<std::int64_t>::min(), std::numeric_limits<std::int64_t>::max())
          .has_value());
 
+static_assert(checkedMul(0, std::numeric_limits<std::int64_t>::min()) == 0);
+static_assert(checkedMul(std::numeric_limits<std::int64_t>::min(), 0) == 0);
+static_assert(checkedMul(-1, -1) == 1);
+// a > 0, b > 0
+static_assert(
+    checkedMul(std::numeric_limits<std::int64_t>::max(), 1) ==
+    std::numeric_limits<std::int64_t>::max());
+static_assert(
+    checkedMul(std::numeric_limits<std::int64_t>::max() / 2, 2) ==
+    std::numeric_limits<std::int64_t>::max() - 1);
+static_assert(!checkedMul((std::numeric_limits<std::int64_t>::max() / 2) + 1, 2).has_value());
+static_assert(!checkedMul(2, (std::numeric_limits<std::int64_t>::max() / 2) + 1).has_value());
+// a > 0, b < 0
+static_assert(
+    checkedMul(std::numeric_limits<std::int64_t>::max(), -1) ==
+    -std::numeric_limits<std::int64_t>::max());
+static_assert(
+    checkedMul((std::numeric_limits<std::int64_t>::max() / 2) + 1, -2) ==
+    std::numeric_limits<std::int64_t>::min());
+static_assert(!checkedMul((std::numeric_limits<std::int64_t>::max() / 2) + 2, -2).has_value());
+static_assert(
+    checkedMul(1, std::numeric_limits<std::int64_t>::min()) ==
+    std::numeric_limits<std::int64_t>::min());
+static_assert(
+    checkedMul(2, std::numeric_limits<std::int64_t>::min() / 2) ==
+    std::numeric_limits<std::int64_t>::min());
+static_assert(!checkedMul(2, (std::numeric_limits<std::int64_t>::min() / 2) - 1).has_value());
+// a < 0, b > 0
+static_assert(
+    checkedMul(std::numeric_limits<std::int64_t>::min(), 1) ==
+    std::numeric_limits<std::int64_t>::min());
+static_assert(
+    checkedMul(std::numeric_limits<std::int64_t>::min() / 2, 2) ==
+    std::numeric_limits<std::int64_t>::min());
+static_assert(!checkedMul((std::numeric_limits<std::int64_t>::min() / 2) - 1, 2).has_value());
+static_assert(!checkedMul(std::numeric_limits<std::int64_t>::min(), 2).has_value());
+// a < 0, b < 0
+static_assert(
+    checkedMul(-(std::numeric_limits<std::int64_t>::max() / 2), -2) ==
+    std::numeric_limits<std::int64_t>::max() - 1);
+static_assert(!checkedMul(std::numeric_limits<std::int64_t>::min() / 2, -2).has_value());
+static_assert(
+    checkedMul(-1, -std::numeric_limits<std::int64_t>::max()) ==
+    std::numeric_limits<std::int64_t>::max());
+static_assert(!checkedMul(std::numeric_limits<std::int64_t>::min(), -1).has_value());
+static_assert(!checkedMul(-1, std::numeric_limits<std::int64_t>::min()).has_value());
+
 /**
  * Calculate one number divided by another number in percentage.
  * The result is rounded up to the next integer, and capped in the range [0,100]

include/xrpl/basics/TaggedCache.h

@@ -153,6 +153,24 @@ private:
         Policy policy,
         Callback&& replaceCallback = nullptr);
 
+    /**
+     * canonicalizeImpl variant for callers that already hold `mutex_`.
+     *
+     * The unnamed `scoped_lock<MutexType> const&` parameter is proof of
+     * ownership; this overload does not acquire the lock. Use it from other
+     * methods (e.g. fetchAndModify) that need to compose canonicalize with
+     * additional work under a single critical section, without relying on
+     * recursive-mutex re-entry.
+     */
+    template <class Policy, class Callback = std::nullptr_t>
+    bool
+    canonicalizeImpl(
+        std::scoped_lock<MutexType> const&,
+        key_type const& key,
+        CanonicalizeClientPointerType<Policy> data,
+        Policy policy,
+        Callback&& replaceCallback = nullptr);
+
 public:
     /**
      * Replace aliased objects with originals.
@@ -239,9 +257,6 @@ public:
     bool
     retrieve(key_type const& key, T& data);
 
-    MutexType&
-    peekMutex();
-
     std::vector<key_type>
     getKeys() const;
 
@@ -263,6 +278,22 @@ public:
     fetch(key_type const& digest, Handler const& h);
     // End CachedSLEs functions.
 
+    /**
+     * Fetch or create an entry and execute a callback while holding the lock.
+     *
+     * The entry for the given key is fetched from the cache or created if it
+     * doesn't exist. The callback is then invoked with a reference to the
+     * entry while the cache mutex is still held, allowing safe modification
+     * of the cached object.
+     *
+     * @param key The key to fetch or create
+     * @param callback Function to call with the entry under lock.
+     *                 Signature: void(T&)
+     */
+    template <class Callback>
+    void
+    fetchAndModify(key_type const& key, Callback&& callback);
+
 private:
     SharedPointerType
     initialFetch(key_type const& key, std::scoped_lock<MutexType> const& l);

include/xrpl/basics/TaggedCache.ipp

@@ -4,6 +4,7 @@
 #include <xrpl/basics/Log.h>  // IWYU pragma: keep
 #include <xrpl/basics/TaggedCache.h>
 #include <xrpl/basics/scope.h>
+#include <xrpl/beast/utility/instrumentation.h>
 
 #include <algorithm>
 
@@ -335,6 +336,29 @@ template <class Policy, class Callback>
 inline bool
 TaggedCache<Key, T, IsKeyCache, SharedWeakUnionPointer, SharedPointerType, Hash, KeyEqual, Mutex>::
     canonicalizeImpl(
+        key_type const& key,
+        CanonicalizeClientPointerType<Policy> data,
+        Policy policy,
+        Callback&& replaceCallback)
+{
+    std::scoped_lock<MutexType> const lock(mutex_);
+    return canonicalizeImpl(lock, key, data, policy, std::forward<Callback>(replaceCallback));
+}
+
+template <
+    class Key,
+    class T,
+    bool IsKeyCache,
+    class SharedWeakUnionPointer,
+    class SharedPointerType,
+    class Hash,
+    class KeyEqual,
+    class Mutex>
+template <class Policy, class Callback>
+inline bool
+TaggedCache<Key, T, IsKeyCache, SharedWeakUnionPointer, SharedPointerType, Hash, KeyEqual, Mutex>::
+    canonicalizeImpl(
+        std::scoped_lock<MutexType> const&,
         key_type const& key,
         CanonicalizeClientPointerType<Policy> data,
         [[maybe_unused]] Policy policy,
@@ -354,8 +378,6 @@ TaggedCache<Key, T, IsKeyCache, SharedWeakUnionPointer, SharedPointerType, Hash,
     // passing a const argument is a compile error.
     constexpr bool replaceCached = std::is_same_v<Policy, detail::ReplaceCached>;
 
-    std::scoped_lock const lock(mutex_);
-
     auto const cit = cache_.find(key);
 
     if (cit == cache_.end())
@@ -572,22 +594,6 @@ TaggedCache<Key, T, IsKeyCache, SharedWeakUnionPointer, SharedPointerType, Hash,
     return true;
 }
 
-template <
-    class Key,
-    class T,
-    bool IsKeyCache,
-    class SharedWeakUnionPointer,
-    class SharedPointerType,
-    class Hash,
-    class KeyEqual,
-    class Mutex>
-inline auto
-TaggedCache<Key, T, IsKeyCache, SharedWeakUnionPointer, SharedPointerType, Hash, KeyEqual, Mutex>::
-    peekMutex() -> MutexType&
-{
-    return mutex_;
-}
-
 template <
     class Key,
     class T,
@@ -700,6 +706,49 @@ TaggedCache<Key, T, IsKeyCache, SharedWeakUnionPointer, SharedPointerType, Hash,
 }
 // End CachedSLEs functions.
 
+template <
+    class Key,
+    class T,
+    bool IsKeyCache,
+    class SharedWeakUnionPointer,
+    class SharedPointerType,
+    class Hash,
+    class KeyEqual,
+    class Mutex>
+template <class Callback>
+inline void
+TaggedCache<Key, T, IsKeyCache, SharedWeakUnionPointer, SharedPointerType, Hash, KeyEqual, Mutex>::
+    fetchAndModify(key_type const& key, Callback&& callback)
+{
+    static_assert(
+        !IsKeyCache, "fetchAndModify is only supported for value caches, not key-only caches");
+    static_assert(
+        std::is_same_v<std::shared_ptr<T>, SharedPointerType> ||
+            std::is_same_v<intr_ptr::SharedPtr<T>, SharedPointerType>,
+        "fetchAndModify requires std::shared_ptr<T> or intr_ptr::SharedPtr<T>");
+
+    std::scoped_lock<MutexType> const lock(mutex_);
+
+    // Same pointer-type dispatch as insert(): the placeholder must have exactly
+    // SharedPointerType so canonicalizeImpl can write the cached pointer back.
+    SharedPointerType entry = [] {
+        if constexpr (std::is_same_v<std::shared_ptr<T>, SharedPointerType>)
+        {
+            return std::make_shared<T>();
+        }
+        else
+        {
+            return intr_ptr::makeShared<T>();
+        }
+    }();
+    canonicalizeImpl(lock, key, entry, detail::ReplaceClient{});
+
+    ALWAYS(
+        entry != nullptr, "xrpl::TaggedCache::fetchAndModify : entry present after canonicalize");
+
+    callback(*entry);
+}
+
 template <
     class Key,
     class T,

include/xrpl/config/Constants.h

@@ -94,6 +94,7 @@ struct Keys
     static constexpr auto kBbtOptions = "bbt_options";
     static constexpr auto kBgThreads = "bg_threads";
     static constexpr auto kBlockSize = "block_size";
+    static constexpr auto kBytecodeSizeLimit = "bytecode_size_limit";
     static constexpr auto kCacheAge = "cache_age";
     static constexpr auto kCacheMb = "cache_mb";
     static constexpr auto kCacheSize = "cache_size";
@@ -108,6 +109,8 @@ struct Keys
     static constexpr auto kFileSizeMult = "file_size_mult";
     static constexpr auto kFilterBits = "filter_bits";
     static constexpr auto kFilterFull = "filter_full";
+    static constexpr auto kGasLimit = "gas_limit";
+    static constexpr auto kGasPrice = "gas_price";
     static constexpr auto kHardSet = "hard_set";
     static constexpr auto kHighThreads = "high_threads";
     static constexpr auto kHoldTime = "hold_time";

include/xrpl/ledger/Ledger.h

@@ -105,6 +105,16 @@ public:
         std::vector<UInt256> const& amendments,
         Family& family);
 
+    /**
+     * Create a ledger from a header whose maps are filled in afterwards.
+     *
+     * Both maps start Synching against the hashes the header carries, which are
+     * input rather than derived, so setImmutable() leaves them alone.
+     *
+     * @param info The header to build from.
+     * @param rules The rules in force.
+     * @param family The SHAMap family the maps belong to.
+     */
     Ledger(LedgerHeader const& info, Rules rules, Family& family);
 
     /**
@@ -257,38 +267,74 @@ public:
         header_.validated = true;
     }
 
-    void
+    /**
+     * Mark this ledger as accepted and attempt to make it immutable.
+     *
+     * The close-time fields are recorded first, since the ledger hash covers
+     * them.
+     *
+     * @param closeTime The consensus-agreed close time.
+     * @param closeResolution The close time resolution.
+     * @param correctCloseTime Whether consensus agreed on the close time. If
+     *        false, kSLcfNoConsensusTime is recorded in closeFlags instead.
+     * @return What setImmutable() returned.
+     */
+    [[nodiscard]] bool
     setAccepted(
         NetClock::time_point closeTime,
         NetClock::duration closeResolution,
         bool correctCloseTime);
 
-    void
+    /**
+     * Mark this ledger as immutable, so it can no longer be modified.
+     *
+     * Only a map syncing against hashes from outside can be found unsound (see
+     * SHAMap::addKnownNode), so a caller whose ledger was built or loaded
+     * locally treats a false return as a broken internal invariant.
+     *
+     * @param rehash Whether to recompute the ledger hash from the header
+     *        fields. The transaction and account hashes are recomputed from the
+     *        maps too, but only the first time and only if the header did not
+     *        supply them.
+     * @return false if either map is Invalid, leaving the immutable flag as it
+     *         was and the header untouched. The ledger must then be discarded
+     *         rather than retried, since one map may already be immutable.
+     */
+    [[nodiscard]] bool
     setImmutable(bool rehash = true);
 
+    /**
+     * @return Whether both maps have been settled, so the ledger can no longer
+     *         change.
+     */
     bool
     isImmutable() const
     {
         return immutable_;
     }
 
-    /*  Mark this ledger as "should be full".
+    /**
+     * @return Whether both maps can still be the maps the header names. See
+     *         SHAMap::isValid().
+     */
+    [[nodiscard]] bool
+    mapsValid() const
+    {
+        return txMap_.isValid() && stateMap_.isValid();
+    }
 
-        "Full" is metadata property of the ledger, it indicates
-        that the local server wants all the corresponding nodes
-        in durable storage.
-
-        This is marked `const` because it reflects metadata
-        and not data that is in common with other nodes on the
-        network.
-    */
+    /**
+     * Mark this ledger as "should be full", indicating that the local server
+     * wants all the corresponding nodes in durable storage.
+     *
+     * Const because it reflects metadata, not data this ledger shares with
+     * other nodes on the network.
+     */
     void
     setFull() const
     {
-        txMap_.setFull();
-        txMap_.setLedgerSeq(header_.seq);
-        stateMap_.setFull();
-        stateMap_.setLedgerSeq(header_.seq);
+        txMap_.setFull(header_.seq);
+        stateMap_.setFull(header_.seq);
     }
 
     void
@@ -418,8 +464,33 @@ private:
     static std::pair<std::shared_ptr<STTx const>, std::shared_ptr<STObject const>>
     deserializeTxPlusMeta(SHAMapItem const& item);
 
+    /**
+     * Make both maps immutable.
+     *
+     * Each map is settled on its own, so neither is left mid-sync because the
+     * other refused.
+     *
+     * @return Whether both maps are immutable.
+     */
+    [[nodiscard]] bool
+    setMapsImmutable()
+    {
+        bool const txImmutable = txMap_.setImmutable();
+        bool const stateImmutable = stateMap_.setImmutable();
+        return txImmutable && stateImmutable;
+    }
+
     bool immutable_;
 
+    /**
+     * Whether the header supplied the transaction and account hashes, so they
+     * must not be derived from the maps.
+     *
+     * True only for a ledger built from a header, which stays verified against
+     * the hash it was asked for. Fixed at construction, unlike immutable_.
+     */
+    bool const mapHashesFromHeader_ = false;
+
     // A SHAMap containing the transactions associated with this ledger.
     SHAMap mutable txMap_;
 

include/xrpl/ledger/View.h

@@ -265,6 +265,13 @@ canWithdraw(
 [[nodiscard]] TER
 canWithdraw(ReadView const& view, STTx const& tx);
 
+/**
+ * Pays out a withdrawal from a vault or loan broker pseudo-account.
+ *
+ * `sourceAmount` leaves `sourceAcct` and `destinationAmount` reaches `dstAcct`.
+ * The two differ only when the withdrawal carries a transfer fee; the
+ * difference is the fee and is settled through the issuer.
+ */
 [[nodiscard]] TER
 doWithdraw(
     ApplyViewContext ctx,
@@ -272,7 +279,8 @@ doWithdraw(
     AccountID const& dstAcct,
     AccountID const& sourceAcct,
     XRPAmount priorBalance,
-    STAmount const& amount,
+    STAmount const& destinationAmount,
+    STAmount const& sourceAmount,
     beast::Journal j);
 
 /**

include/xrpl/ledger/helpers/AMMHelpers.h

@@ -2,7 +2,6 @@
 
 #include <xrpl/basics/Log.h>
 #include <xrpl/basics/Number.h>
-#include <xrpl/basics/contract.h>
 #include <xrpl/beast/utility/Journal.h>
 #include <xrpl/beast/utility/Zero.h>
 #include <xrpl/ledger/ApplyView.h>
@@ -29,7 +28,6 @@
 #include <expected>
 #include <functional>
 #include <optional>
-#include <stdexcept>
 #include <tuple>
 #include <utility>
 
@@ -313,11 +311,11 @@ getAMMOfferStartWithTakerPays(
  * is equal to LOB quality (in this case AMM offer quality is
  * better than LOB quality) or AMM offer is equal to LOB quality
  * (in this case SPQ is better than LOB quality).
- * Pre-amendment code calculates takerPays first. If takerGets is the
- * economically coarser integral side, it is rounded down, which results in
- * worse offer quality than LOB quality, and the offer might fail to generate.
- * Post-amendment code calculates the economically coarser integral offer side
- * first. The result is rounded down, which makes the offer quality better.
+ * The economically coarser integral offer side is calculated first. The
+ * result is rounded down, which makes the offer quality better. Calculating
+ * takerPays first instead would round down takerGets when that is the coarser
+ * side, giving worse quality than LOB quality, and the offer might fail to
+ * generate.
  *   It might not be possible to match either SPQ or AMM offer to LOB
  * quality. This generally happens at higher fees.
  * @param pool AMM pool balances
@@ -331,69 +329,8 @@ changeSpotPriceQuality(
     TAmounts<TIn, TOut> const& pool,
     Quality const& quality,
     std::uint16_t tfee,
-    Rules const& rules,
     beast::Journal j)
 {
-    if (!rules.enabled(fixAMMv1_1))
-    {
-        // Finds takerPays (i) and takerGets (o) such that given pool
-        // composition poolGets(I) and poolPays(O): (O - o) / (I + i) = quality.
-        // Where takerGets is calculated as the swapAssetIn (see below).
-        // The above equation produces the quadratic equation:
-        // i^2*(1-fee) + i*I*(2-fee) + I^2 - I*O/quality,
-        // which is solved for i, and o is found with swapAssetIn().
-        auto const f = feeMult(tfee);  // 1 - fee
-        auto const& a = f;
-        auto const b = pool.in * (1 + f);
-        Number const c = pool.in * pool.in - pool.in * pool.out * quality.rate();
-        auto const res = b * b - 4 * a * c;
-        if (res < 0)
-        {
-            return std::nullopt;  // LCOV_EXCL_LINE
-        }
-        if (auto const nTakerPaysPropose = (-b + root2(res)) / (2 * a); nTakerPaysPropose > 0)
-        {
-            auto const nTakerPays = [&] {
-                // The fee might make the AMM offer quality less than CLOB
-                // quality. Therefore, AMM offer has to satisfy this constraint:
-                // o / i >= q. Substituting o with swapAssetIn() gives: i <= O /
-                // q - I / (1 - fee).
-                auto const nTakerPaysConstraint = pool.out * quality.rate() - pool.in / f;
-                if (nTakerPaysPropose > nTakerPaysConstraint)
-                    return nTakerPaysConstraint;
-                return nTakerPaysPropose;
-            }();
-            if (nTakerPays <= 0)
-            {
-                JLOG(j.trace()) << "changeSpotPriceQuality calc failed: " << to_string(pool.in)
-                                << " " << to_string(pool.out) << " " << quality << " " << tfee;
-                return std::nullopt;
-            }
-            auto const takerPays =
-                toAmount<TIn>(getAsset(pool.in), nTakerPays, Number::RoundingMode::Upward);
-            // should not fail
-            auto amounts = TAmounts<TIn, TOut>{takerPays, swapAssetIn(pool, takerPays, tfee)};
-            if (Quality{amounts} < quality &&
-                !withinRelativeDistance(Quality{amounts}, quality, Number(1, -7)))
-            {
-                JLOG(j.error()) << "changeSpotPriceQuality failed: " << to_string(pool.in) << " "
-                                << to_string(pool.out) << " "
-                                << " " << quality << " " << tfee << " " << to_string(amounts.in)
-                                << " " << to_string(amounts.out);
-                Throw<std::runtime_error>("changeSpotPriceQuality failed");
-            }
-
-            JLOG(j.trace()) << "changeSpotPriceQuality succeeded: " << to_string(pool.in) << " "
-                            << to_string(pool.out) << " "
-                            << " " << quality << " " << tfee << " " << to_string(amounts.in) << " "
-                            << to_string(amounts.out);
-            return amounts;
-        }
-        JLOG(j.trace()) << "changeSpotPriceQuality calc failed: " << to_string(pool.in) << " "
-                        << to_string(pool.out) << " " << quality << " " << tfee;
-        return std::nullopt;
-    }
-
     auto amounts = [&] {
         bool const inIntegral = getAsset(pool.in).integral();
         bool const outIntegral = getAsset(pool.out).integral();
@@ -459,57 +396,49 @@ template <typename TIn, typename TOut>
 TOut
 swapAssetIn(TAmounts<TIn, TOut> const& pool, TIn const& assetIn, std::uint16_t tfee)
 {
-    if (auto const& rules = getCurrentTransactionRules(); rules && rules->enabled(fixAMMv1_1))
-    {
-        // set rounding to always favor the amm. Clip to zero.
-        // calculate:
-        // pool.out -
-        // (pool.in * pool.out) / (pool.in + assetIn * feeMult(tfee)),
-        // and explicitly set the rounding modes
-        // Favoring the amm means we should:
-        // minimize:
-        // pool.out -
-        // (pool.in * pool.out) / (pool.in + assetIn * feeMult(tfee)),
-        // maximize:
-        // (pool.in * pool.out) / (pool.in + assetIn * feeMult(tfee)),
-        // (pool.in * pool.out)
-        // minimize:
-        // (pool.in + assetIn * feeMult(tfee)),
-        // minimize:
-        // assetIn * feeMult(tfee)
-        // feeMult is: (1-fee), fee is tfee/100000
-        // minimize:
-        // 1-fee
-        // maximize:
-        // fee
-        SaveNumberRoundMode const _{Number::getround()};
+    // set rounding to always favor the amm. Clip to zero.
+    // calculate:
+    // pool.out -
+    // (pool.in * pool.out) / (pool.in + assetIn * feeMult(tfee)),
+    // and explicitly set the rounding modes
+    // Favoring the amm means we should:
+    // minimize:
+    // pool.out -
+    // (pool.in * pool.out) / (pool.in + assetIn * feeMult(tfee)),
+    // maximize:
+    // (pool.in * pool.out) / (pool.in + assetIn * feeMult(tfee)),
+    // (pool.in * pool.out)
+    // minimize:
+    // (pool.in + assetIn * feeMult(tfee)),
+    // minimize:
+    // assetIn * feeMult(tfee)
+    // feeMult is: (1-fee), fee is tfee/100000
+    // minimize:
+    // 1-fee
+    // maximize:
+    // fee
+    SaveNumberRoundMode const _{Number::getround()};
 
-        Number::setround(Number::RoundingMode::Upward);
-        auto const numerator = pool.in * pool.out;
-        auto const fee = getFee(tfee);
+    Number::setround(Number::RoundingMode::Upward);
+    auto const numerator = pool.in * pool.out;
+    auto const fee = getFee(tfee);
 
-        Number::setround(Number::RoundingMode::Downward);
-        auto const denom = pool.in + assetIn * (1 - fee);
+    Number::setround(Number::RoundingMode::Downward);
+    auto const denom = pool.in + assetIn * (1 - fee);
 
-        if (denom.signum() <= 0)
-            return toAmount<TOut>(getAsset(pool.out), 0);
+    if (denom.signum() <= 0)
+        return toAmount<TOut>(getAsset(pool.out), 0);
 
-        Number::setround(Number::RoundingMode::Upward);
-        auto const ratio = numerator / denom;
+    Number::setround(Number::RoundingMode::Upward);
+    auto const ratio = numerator / denom;
 
-        Number::setround(Number::RoundingMode::Downward);
-        auto const swapOut = pool.out - ratio;
+    Number::setround(Number::RoundingMode::Downward);
+    auto const swapOut = pool.out - ratio;
 
-        if (swapOut.signum() < 0)
-            return toAmount<TOut>(getAsset(pool.out), 0);
+    if (swapOut.signum() < 0)
+        return toAmount<TOut>(getAsset(pool.out), 0);
 
-        return toAmount<TOut>(getAsset(pool.out), swapOut, Number::RoundingMode::Downward);
-    }
-
-    return toAmount<TOut>(
-        getAsset(pool.out),
-        pool.out - (pool.in * pool.out) / (pool.in + assetIn * feeMult(tfee)),
-        Number::RoundingMode::Downward);
+    return toAmount<TOut>(getAsset(pool.out), swapOut, Number::RoundingMode::Downward);
 }
 
 /**
@@ -526,57 +455,49 @@ template <typename TIn, typename TOut>
 TIn
 swapAssetOut(TAmounts<TIn, TOut> const& pool, TOut const& assetOut, std::uint16_t tfee)
 {
-    if (auto const& rules = getCurrentTransactionRules(); rules && rules->enabled(fixAMMv1_1))
+    // set rounding to always favor the amm. Clip to zero.
+    // calculate:
+    // ((pool.in * pool.out) / (pool.out - assetOut) - pool.in) /
+    // (1-tfee/100000)
+    // maximize:
+    // ((pool.in * pool.out) / (pool.out - assetOut) - pool.in)
+    // maximize:
+    // (pool.in * pool.out) / (pool.out - assetOut)
+    // maximize:
+    // (pool.in * pool.out)
+    // minimize
+    // (pool.out - assetOut)
+    // minimize:
+    // (1-tfee/100000)
+    // maximize:
+    // tfee/100000
+
+    SaveNumberRoundMode const _{Number::getround()};
+
+    Number::setround(Number::RoundingMode::Upward);
+    auto const numerator = pool.in * pool.out;
+
+    Number::setround(Number::RoundingMode::Downward);
+    auto const denom = pool.out - assetOut;
+    if (denom.signum() <= 0)
     {
-        // set rounding to always favor the amm. Clip to zero.
-        // calculate:
-        // ((pool.in * pool.out) / (pool.out - assetOut) - pool.in) /
-        // (1-tfee/100000)
-        // maximize:
-        // ((pool.in * pool.out) / (pool.out - assetOut) - pool.in)
-        // maximize:
-        // (pool.in * pool.out) / (pool.out - assetOut)
-        // maximize:
-        // (pool.in * pool.out)
-        // minimize
-        // (pool.out - assetOut)
-        // minimize:
-        // (1-tfee/100000)
-        // maximize:
-        // tfee/100000
-
-        SaveNumberRoundMode const _{Number::getround()};
-
-        Number::setround(Number::RoundingMode::Upward);
-        auto const numerator = pool.in * pool.out;
-
-        Number::setround(Number::RoundingMode::Downward);
-        auto const denom = pool.out - assetOut;
-        if (denom.signum() <= 0)
-        {
-            return toMaxAmount<TIn>(getAsset(pool.in));
-        }
-
-        Number::setround(Number::RoundingMode::Upward);
-        auto const ratio = numerator / denom;
-        auto const numerator2 = ratio - pool.in;
-        auto const fee = getFee(tfee);
-
-        Number::setround(Number::RoundingMode::Downward);
-        auto const feeMult = 1 - fee;
-
-        Number::setround(Number::RoundingMode::Upward);
-        auto const swapIn = numerator2 / feeMult;
-        if (swapIn.signum() < 0)
-            return toAmount<TIn>(getAsset(pool.in), 0);
-
-        return toAmount<TIn>(getAsset(pool.in), swapIn, Number::RoundingMode::Upward);
+        return toMaxAmount<TIn>(getAsset(pool.in));
     }
 
-    return toAmount<TIn>(
-        getAsset(pool.in),
-        ((pool.in * pool.out) / (pool.out - assetOut) - pool.in) / feeMult(tfee),
-        Number::RoundingMode::Upward);
+    Number::setround(Number::RoundingMode::Upward);
+    auto const ratio = numerator / denom;
+    auto const numerator2 = ratio - pool.in;
+    auto const fee = getFee(tfee);
+
+    Number::setround(Number::RoundingMode::Downward);
+    auto const feeMult = 1 - fee;
+
+    Number::setround(Number::RoundingMode::Upward);
+    auto const swapIn = numerator2 / feeMult;
+    if (swapIn.signum() < 0)
+        return toAmount<TIn>(getAsset(pool.in), 0);
+
+    return toAmount<TIn>(getAsset(pool.in), swapIn, Number::RoundingMode::Upward);
 }
 
 /**

include/xrpl/ledger/helpers/LendingHelpers.h

@@ -7,10 +7,10 @@
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/ReadView.h>
+#include <xrpl/ledger/helpers/VaultHelpers.h>
 #include <xrpl/protocol/AccountID.h>
 #include <xrpl/protocol/Asset.h>
 #include <xrpl/protocol/LedgerFormats.h>  // IWYU pragma: keep
-#include <xrpl/protocol/Protocol.h>
 #include <xrpl/protocol/Rules.h>
 #include <xrpl/protocol/SField.h>
 #include <xrpl/protocol/STAmount.h>
@@ -31,9 +31,9 @@ namespace xrpl {
 /**
  * Broker cover preclaim precision guard (fixCleanup3_2_0).
  *
- * Prevents a "silent sub-ULP no-op" where a deposit, withdrawal, or clawback
- * amount is so small that it rounds to zero at `sfCoverAvailable`'s scale.
- * Without this guard, both the pseudo trust-line and `sfCoverAvailable` would
+ * Prevents a silent sub-ULP no-op where a deposit, withdrawal, or clawback
+ * amount is so small that it rounds to zero at sfCoverAvailable's scale.
+ * Without this guard, both the pseudo trust-line and sfCoverAvailable would
  * identically absorb the rounded zero, resulting in a successful transaction
  * (tesSUCCESS) where no funds actually moved.
  *
@@ -44,8 +44,8 @@ namespace xrpl {
  * @param j          Journal for logging.
  * @param logPrefix  Transactor name for log diagnostics.
  *
- * @return `tecPRECISION_LOSS` if the request rounds to zero at cover scale.
- * `tesSUCCESS` if the amendment is disabled or the request is safely supra-ULP.
+ * @return tecPRECISION_LOSS if the request rounds to zero at cover scale.
+ * tesSUCCESS if the amendment is disabled or the request is safely supra-ULP.
  */
 [[nodiscard]] TER
 canApplyToBrokerCover(
@@ -56,6 +56,82 @@ canApplyToBrokerCover(
     beast::Journal j,
     std::string_view logPrefix);
 
+namespace detail {
+
+/**
+ * Return a LoanBroker's posterior live cover exponent after applying an
+ * unrounded delta.
+ */
+[[nodiscard]] int
+getPosteriorBrokerCoverScale(SLE::ConstRef vault, SLE::ConstRef broker, Number const& delta);
+
+/**
+ * Round a cover outflow delta (cover withdraw, cover clawback, the
+ * broker-side decrease of a default's cover credit) at the LoanBroker's
+ * posterior live exponent. Safe to round the delta directly for an outflow:
+ * amount on the posterior grid of CoverAvailable always leaves CoverAvailable
+ * minus amount representable, since the posterior grid is exactly the grid
+ * CoverAvailable itself will canonicalize to after the subtraction.
+ */
+[[nodiscard]] STAmount
+roundToPosteriorBrokerCoverScale(
+    SLE::ConstRef vault,
+    SLE::ConstRef broker,
+    STAmount const& delta,
+    Number::RoundingMode roundingMode);
+
+}  // namespace detail
+
+/**
+ * Round a cover debit (cover withdraw, cover clawback, the broker-side
+ * decrease of a default's cover credit): amount is the non-negative
+ * magnitude leaving CoverAvailable. Negates so the posterior is computed for
+ * CoverAvailable minus amount, then negates the result back to a
+ * non-negative magnitude, per roundToPosteriorBrokerCoverScale's outflow
+ * rationale above. Magnitude in, magnitude out -- unlike the vault-side
+ * outflow dispatcher (clampVaultOutflow), which takes and returns a negative
+ * delta; callers on each side already hold the value in that side's native
+ * form.
+ */
+[[nodiscard]] STAmount
+debitToPosteriorBrokerCoverScale(
+    SLE::ConstRef vault,
+    SLE::ConstRef broker,
+    STAmount const& amount,
+    Number::RoundingMode roundingMode);
+
+/**
+ * Round a cover inflow (cover deposit, LoanPay's fee redirect into cover)
+ * into CoverAvailable by flooring the sum rather than the delta:
+ * credit = floor16(CoverAvailable + raw) - CoverAvailable, never finer
+ * than the Vault's base exponent (-Scale). See
+ * creditToPosteriorAvailableScale's doc for why the sum, not the delta,
+ * must be floored; the same reasoning applies to CoverAvailable.
+ */
+[[nodiscard]] STAmount
+creditToPosteriorBrokerCoverScale(
+    SLE::ConstRef vault,
+    SLE::ConstRef broker,
+    Number const& raw,
+    Number::RoundingMode roundingMode);
+
+/**
+ * Check whether amount is an admissible optional cover inflow.
+ *
+ * Legacy and CashBasis Vaults always succeed. A LoanBroker attached to a
+ * FixedPrecision Vault must remain at the Vault's base scale after applying
+ * the rounded amount, and its posterior CoverAvailable must stay within the
+ * Open zone.
+ *
+ * LoanPay's fee redirect into cover is a mandatory inflow and does not call
+ * this check, so it can push CoverAvailable past the Open zone limit this
+ * check enforces. Once that happens, every subsequent LoanBrokerCoverDeposit
+ * returns tecLIMIT_EXCEEDED until the owner withdraws cover back under the
+ * limit; LoanBrokerCoverWithdraw and LoanBrokerCoverClawback are unaffected.
+ */
+[[nodiscard]] TER
+checkOptionalBrokerCoverInflow(SLE::ConstRef vault, SLE::ConstRef broker, STAmount const& amount);
+
 // Lending protocol has dependencies, so capture them here.
 bool
 checkLendingProtocolDependencies(Rules const& rules, STTx const& tx);
@@ -64,13 +140,13 @@ checkLendingProtocolDependencies(Rules const& rules, STTx const& tx);
  * The accounts and asset that LoanManage::defaultLoan's fixCleanup3_4_0
  * freeze/lock exemption applies to.
  *
- * `defaultLoan` moves funds from the LoanBroker pseudo-account to the Vault
- * pseudo-account via `accountSend`. Since neither is the vault asset's
+ * defaultLoan moves funds from the LoanBroker pseudo-account to the Vault
+ * pseudo-account via accountSend. Since neither is the vault asset's
  * issuer, this is a third-party transfer that transits through the issuer in
  * two hops (broker -> issuer, issuer -> vault; see
- * `directSendNoLimitIOU`/`directSendNoLimitMPT`), so the exemption must cover
+ * directSendNoLimitIOU/directSendNoLimitMPT), so the exemption must cover
  * both the issuer/broker and issuer/vault pairs, not a direct broker/vault
- * pair. `asset` scopes it further to the vault's own currency/MPT issuance,
+ * pair. asset scopes it further to the vault's own currency/MPT issuance,
  * so an unrelated one the same accounts happen to hold is still protected.
  */
 struct LoanDefaultFreezeExemptAccounts
@@ -88,10 +164,10 @@ struct LoanDefaultFreezeExemptAccounts
  * @param view Ledger view used to resolve the Loan -> LoanBroker -> Vault
  * chain.
  * @param tx The transaction under invariant review.
- * @return The exempt accounts and asset if `tx` is a `ttLOAN_MANAGE`
- * transaction with the `tfLoanDefault` flag set, `fixCleanup3_4_0` is
+ * @return The exempt accounts and asset if tx is a ttLOAN_MANAGE
+ * transaction with the tfLoanDefault flag set, fixCleanup3_4_0 is
  * enabled, and the loan/broker/vault objects it references can all be
- * resolved; `std::nullopt` otherwise.
+ * resolved; std::nullopt otherwise.
  */
 [[nodiscard]] std::optional<LoanDefaultFreezeExemptAccounts>
 getLoanDefaultFreezeExemptAccounts(ReadView const& view, STTx const& tx);
@@ -254,28 +330,38 @@ adjustImpreciseNumber(
         value = 0;
 }
 
-inline int
-getAssetsTotalScale(SLE::ConstRef vaultSle)
-{
-    if (!vaultSle)
-        return Number::kMinExponent - 1;  // LCOV_EXCL_LINE
-    return scale(vaultSle->at(sfAssetsTotal), vaultSle->at(sfAsset));
-}
+/**
+ * Apply a signed delta to a LoanBroker's DebtTotal: on FixedPrecision Vaults,
+ * add the exact delta (DebtTotal moves by exactly the same amount as the
+ * Vault's AssetsDeployed, never re-rounded); on Legacy/CashBasis Vaults,
+ * round through adjustImpreciseNumber at vaultScale. Shared by LoanSet
+ * (origination) and LoanPay (payment, where delta is negative).
+ *
+ * @param brokerSle The LoanBroker whose DebtTotal is adjusted.
+ * @param vaultSle The LoanBroker's Vault.
+ * @param delta The signed change to DebtTotal.
+ * @param vaultScale The Vault scale the caller captured before changing
+ *        AssetsTotal. Legacy/CashBasis round DebtTotal at that scale, not at
+ *        the scale after this transaction's AssetsTotal change. Unused on
+ *        FixedPrecision Vaults.
+ */
+void
+adjustBrokerDebtTotal(
+    SLE::Ref brokerSle,
+    SLE::ConstRef vaultSle,
+    Number const& delta,
+    int vaultScale);
 
-// Compute the minimum required broker cover, rounded consistently.
-// DebtTotal is a broker-level aggregate maintained at vault scale, so the
-// rounding must also use vault scale — never an individual loan's scale.
-inline Number
-minimumBrokerCover(Number const& debtTotal, TenthBips32 coverRateMinimum, SLE::ConstRef vaultSle)
-{
-    XRPL_ASSERT(
-        vaultSle && vaultSle->getType() == ltVAULT, "xrpl::minimumBrokerCover : valid Vault sle");
-    NumberRoundModeGuard const mg(Number::RoundingMode::Upward);
-    return roundToAsset(
-        vaultSle->at(sfAsset),
-        tenthBipsOfValue(debtTotal, coverRateMinimum),
-        getAssetsTotalScale(vaultSle));
-}
+/**
+ * Minimum required broker cover, rounded up.
+ *
+ * DebtTotal is a broker-level aggregate, never rounded at an individual
+ * loan's scale. Legacy and CashBasis Vaults round at the live AssetsTotal
+ * exponent. FixedPrecision Vaults round at the Vault's base exponent
+ * (-Scale, or 0 for integral assets).
+ */
+Number
+minimumBrokerCover(Number const& debtTotal, TenthBips32 coverRateMinimum, SLE::ConstRef vaultSle);
 
 TER
 checkLoanGuards(
@@ -379,10 +465,10 @@ loanPaymentDeltas(LoanPaymentParts const& parts);
 
 }  // namespace cash_basis
 
-// Public dispatchers: pick cash_basis:: if featureLendingProtocolV1_1 is
-// enabled AND the Vault's LEVersion (VaultHelpers::getVaultVersion) is
-// VaultVersion::CashBasis, else instant_recognition::. These are the only entry points
-// transactors call.
+// Public dispatchers: pick cash_basis:: if the Vault's LEVersion
+// (VaultHelpers::getVaultVersion) is CashBasis or later (CashBasis or
+// FixedPrecision), else instant_recognition::. These are the only entry
+// points transactors call.
 AccountingDeltas
 loanOriginationDeltas(
     SLE::ConstRef vaultSle,

include/xrpl/ledger/helpers/MPTokenHelpers.h

@@ -312,12 +312,22 @@ checkCreateMPT(
 //
 //------------------------------------------------------------------------------
 
-// MaximumAmount doesn't exceed 2**63-1
+/**
+ * MaximumAmount doesn't exceed 2**63-1
+ */
 std::int64_t
 maxMPTAmount(SLE const& sleIssuance);
 
-// OutstandingAmount may overflow and available amount might be negative.
-// But available amount is always <= |MaximumAmount - OutstandingAmount|.
+/**
+ * std::nullopt if the issuance doesn't exist.
+ */
+std::optional<std::int64_t>
+maxMPTAmount(ReadView const& view, MPTID const& mptID);
+
+/**
+ * OutstandingAmount may overflow and available amount might be negative.
+ * But available amount is always <= |MaximumAmount - OutstandingAmount|.
+ */
 std::int64_t
 availableMPTAmount(SLE const& sleIssuance);
 
@@ -331,7 +341,12 @@ availableMPTAmount(ReadView const& view, MPTID const& mptID);
  * directSendNoFee transactions that bypass the payment engine.
  * 2.  **accountSend & Payment Engine (Overflow: Yes):** A temporary overflow
  * check when `OutstandingAmount > UINT64_MAX`. This higher threshold is used
- * for `accountSend` and payments processed via the payment engine.
+ * for `accountSend` and payments processed via the payment engine, whose
+ * reverse pass may issue before it redeems.
+ *
+ * In both cases a single `sendAmount > MaximumAmount` is rejected. Such a send
+ * can never settle: redemptions within the transaction are bounded by the
+ * outstanding amount, so the final OutstandingAmount would exceed the cap.
  */
 bool
 isMPTOverflow(
@@ -353,6 +368,12 @@ issuerFundsToSelfIssue(ReadView const& view, MPTIssue const& issue);
 /**
  * Facilitate tracking of MPT sold by an issuer owning MPT sell offer.
  * See ApplyView::issuerSelfDebitHookMPT().
+ *
+ * `amount` may be 0. BookStep removes an offer whose fee-adjusted funded
+ * output is 0, but other clips (for example MaximumAmount via limitStepIn)
+ * can still consume a zero slice of a funded remainder. The hook must
+ * accept 0: first call still snapshots origBalance; a zero debit adds
+ * nothing to selfDebit.
  */
 void
 issuerSelfDebitHookMPT(ApplyView& view, MPTIssue const& issue, std::uint64_t amount);

include/xrpl/ledger/helpers/ProposalHelpers.h

@@ -1,10 +1,17 @@
 #pragma once
 
+#include <xrpl/beast/utility/Journal.h>
+#include <xrpl/ledger/ApplyView.h>
+#include <xrpl/ledger/ReadView.h>
 #include <xrpl/protocol/SField.h>
+#include <xrpl/protocol/STLedgerEntry.h>
 #include <xrpl/protocol/STObject.h>
+#include <xrpl/protocol/STTx.h>
+#include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/TxFormats.h>
 
 #include <cstdint>
+#include <optional>
 
 namespace xrpl::proposal {
 
@@ -30,31 +37,22 @@ proposalOwnerCount(STObject const& proposedTx)
                                                                 : kProposalOwnerCount;
 }
 
-/**
- * Whether the proposed transaction is itself a proposal transaction, which
- * would nest one proposal inside another.
- *
- * TODO: cover ttTRANSACTION_PROPOSAL_SIGN and ttTRANSACTION_PROPOSAL_CANCEL
- * once those transactions exist.
- */
-inline bool
-isProposalTx(STObject const& proposedTx)
-{
-    return proposedTx.getFieldU16(sfTransactionType) == ttTRANSACTION_PROPOSAL_CREATE;
-}
-
 /**
  * Whether the proposed transaction is independently submittable through the
- * ordinary multi-sign path: not a nested proposal, not a pseudo-transaction,
- * not itself flagged as someone else's inner batch transaction, and — if it
- * is a Batch — none of its own inner transactions is a nested proposal or a
- * pseudo-transaction either. A Batch inner transaction cannot itself be
- * pseudo (preflight0 rejects the pseudo/tfInnerBatchTxn combination
- * generically), but that guard lives outside this feature, so it is checked
- * again here rather than relied upon.
+ * ordinary multi-sign path: not a proposal transaction itself, not a
+ * pseudo-transaction, not itself flagged as someone else's inner batch
+ * transaction, and — if it is a Batch — every one of its own inner
+ * transactions carries a TransactionType and is neither a proposal, a
+ * pseudo-transaction, nor a nested Batch. A Batch inner transaction cannot
+ * lack a TransactionType, be pseudo, or be a nested Batch (STTx construction
+ * rejects a typeless inner and an inner Batch, and preflight0 rejects the
+ * pseudo/tfInnerBatchTxn combination), but those guards live outside this
+ * feature, so they are checked again here rather than relied upon.
+ *
+ * TODO: cover ttTRANSACTION_PROPOSAL_SIGN once that transaction exists.
  */
 bool
-isValidProposal(STObject const& proposedTx);
+isValidProposalTxnType(STObject const& proposedTx);
 
 /**
  * Whether the proposed transaction carries any signature field.
@@ -84,4 +82,93 @@ hasEmptySigningPubKey(STObject const& proposedTx)
         proposedTx.getFieldVL(sfSigningPubKey).empty();
 }
 
+/**
+ * Whether the proposal is terminal (On-Chain Cosigner spec §4.5). A terminal proposal
+ * stops accepting signatures and anyone may delete it. An already signed
+ * payload can still execute after Expiration, because the Ticket reservation
+ * compares payloads only; a passed LastLedgerSequence does stop it.
+ *
+ * A proposal is terminal when either:
+ * - its Expiration has passed (the parent ledger closed at or after it), or
+ * - the proposed transaction carries a LastLedgerSequence and the current
+ *   ledger sequence is strictly greater than it. This mirrors the ordinary
+ *   transactor's tefMAX_LEDGER rule: at view.seq() == LastLedgerSequence the
+ *   payload can still be submitted in the current ledger, so the proposal is
+ *   still live.
+ *
+ * @param view The ledger the deciding transaction is being applied to.
+ * @param expiration The proposal's Expiration field.
+ * @param proposedTx The proposal's ProposedTransaction field.
+ */
+bool
+isTerminal(
+    ReadView const& view,
+    std::optional<std::uint32_t> expiration,
+    STObject const& proposedTx);
+
+/**
+ * Delete a TransactionProposal ledger entry.
+ *
+ * Removes the entry from its Owner's directory, releases the reserve the
+ * proposal holds against the Owner, and erases the entry. Shared by every
+ * deletion path the spec defines (On-Chain Cosigner spec §4.5): automatic cleanup when the
+ * proposed transaction's TicketSequence is consumed, and the
+ * TransactionProposalCancel / TransactionProposalSign cleanup paths once
+ * those transactions exist.
+ *
+ * The release goes through decreaseOwnerCountForObject, so it follows the
+ * sfSponsor an entry created with reserve sponsorship carries: the reserve is
+ * returned to whoever was holding it, the Owner or that sponsor.
+ *
+ * @param view The apply view for making changes
+ * @param sleProposal The TransactionProposal ledger entry to delete
+ * @param j Journal for logging
+ * @return tesSUCCESS, tecINTERNAL for an invalid entry, or tefBAD_LEDGER if
+ *         the ledger contradicts the entry
+ */
+TER
+deleteProposal(ApplyView& view, SLE::pointer const& sleProposal, beast::Journal j);
+
+/**
+ * Whether tx carries the same payload as a proposal's stored
+ * ProposedTransaction (On-Chain Cosigner spec §4.2.1).
+ *
+ * The payload is the signing payload: the fields the collected signatures
+ * commit to. Compared is every field except those flagged kNotSigning
+ * (TxnSignature, Signers, BatchSigners, CounterpartySignature,
+ * SponsorSignature, Signature, MasterSignature) and SigningPubKey, which is
+ * stored empty and filled only if the target signs with its own key. So the
+ * completed transaction matches no matter which mix of collected or
+ * off-ledger signatures it carries, and any change to a non-signature field
+ * results in a false-return value.
+ *
+ * Signature (PaymentChannelClaim and the XChain attestation transactions)
+ * is deliberately not compared: it is outside the account's own TxnSignature
+ * even for an ordinary submission, so a proposal cannot bind it more tightly
+ * than the signatures it collects do, and those transactors still validate a
+ * substituted value exactly as they would for an ordinary submission.
+ * MasterSignature appears in no transaction format.
+ *
+ * @param proposedTx The proposal's ProposedTransaction field.
+ * @param tx The transaction to compare, typically an STTx.
+ */
+bool
+payloadMatches(STObject const& proposedTx, STObject const& tx);
+
+/**
+ * Whether tx may consume its Ticket.
+ *
+ * While a proposal keyed to the Ticket exists, the target's Ticket is
+ * reserved: only the proposal's own proposed transaction may spend it
+ * (On-Chain Cosigner spec §4.2.1), so that unrelated target-account activity cannot
+ * invalidate the proposal while signatures are being collected.
+ * TransactionProposalCancel is not allowed through: it deletes the
+ * reservation without consuming the ticket.
+ *
+ * @param view The ledger containing the Ticket and any reservation.
+ * @param tx The transaction attempting to consume that ticket.
+ */
+bool
+canConsumeTicket(ReadView const& view, STTx const& tx);
+
 }  // namespace xrpl::proposal

include/xrpl/ledger/helpers/TokenHelpers.h

@@ -316,6 +316,20 @@ transferRate(ReadView const& view, Asset const& asset);
 [[nodiscard]] Rate
 transferRate(ReadView const& view, STAmount const& amount);
 
+/**
+ * Returns the amount a sender must part with for `amount` to reach the
+ * receiver once the issuer takes the transfer fee. Rounds up.
+ */
+[[nodiscard]] STAmount
+addTransferFee(STAmount const& amount, Rate const& rate);
+
+/**
+ * Returns the amount a receiver gets when `amount` leaves the sender and the
+ * issuer takes the transfer fee. Rounds down.
+ */
+[[nodiscard]] STAmount
+subtractTransferFee(STAmount const& amount, Rate const& rate);
+
 //------------------------------------------------------------------------------
 //
 // Holding operations (Asset-based dispatchers)

include/xrpl/ledger/helpers/VaultHelpers.h

@@ -14,6 +14,7 @@
 #include <cstdint>
 #include <expected>
 #include <optional>
+#include <string_view>
 
 namespace xrpl {
 
@@ -80,6 +81,21 @@ struct VaultBalanceChange
 [[nodiscard]] TER
 adjustVaultBalances(SLE::Ref vault, VaultBalanceChange const& change, beast::Journal j);
 
+/**
+ * @brief Apply a signed cash movement to a Vault of any version. FixedPrecision
+ * Vaults go through adjustVaultBalances; Legacy and CashBasis Vaults add the
+ * amount to both AssetsTotal and AssetsAvailable.
+ *
+ * @param vault The vault SLE.
+ * @param delta Signed change to AssetsAvailable; the exact amount moved on the
+ *              Vault pseudo-account.
+ * @param j Journal passed through to adjustVaultBalances.
+ *
+ * @return tesSUCCESS, or the adjustVaultBalances error for FixedPrecision Vaults.
+ */
+[[nodiscard]] TER
+adjustVaultCash(SLE::Ref vault, STAmount const& delta, beast::Journal j);
+
 /**
  * Return the Vault's current live exponent.
  *
@@ -148,18 +164,20 @@ posteriorAssetScale(
 
 /**
  * Shared core of creditToPosteriorAvailableScale and
- * creditToPosteriorBrokerCoverScale: floors reference + raw at scale and
- * returns the difference from reference, so the delta applied is exactly
- * what moves reference onto the floored sum. See
- * creditToPosteriorAvailableScale's doc for why the sum, not raw alone,
- * must be floored. raw is the exact amount; it is not rounded on its own
- * before being added to reference.
+ * creditToPosteriorBrokerCoverScale: floors reference + raw at the sum's
+ * own live scale (never finer than baseScale) and returns the difference
+ * from reference, so the delta applied is exactly what moves reference onto
+ * the floored sum. See creditToPosteriorAvailableScale's doc for why the
+ * sum, not raw alone, must be floored. raw is the exact amount; it is not
+ * rounded on its own before being added to reference. The sum and its scale
+ * are computed once, in roundingMode, so a Downward credit is always
+ * between zero and raw.
  */
 [[nodiscard]] STAmount
 creditToPosteriorScale(
     Asset const& asset,
     Number const& reference,
-    int atScale,
+    int baseScale,
     Number const& raw,
     Number::RoundingMode roundingMode);
 
@@ -333,6 +351,18 @@ vaultBaseScale(Asset const& asset, std::uint8_t scale);
 [[nodiscard]] bool
 isOnVaultBaseGrid(Asset const& asset, Number const& value, int baseScale);
 
+/**
+ * Checks that a requested AssetsMaximum is exactly representable on the
+ * Vault's base grid, otherwise associateAsset would silently round the cap
+ * the owner asked for. Used by VaultSet::preclaim on an existing Vault.
+ *
+ * @param vault The vault ledger entry.
+ * @param amount The requested AssetsMaximum.
+ * @return tesSUCCESS, or tecPRECISION_LOSS if amount is not representable.
+ */
+[[nodiscard]] TER
+checkAssetsMaximum(SLE::ConstRef vault, Number const& amount);
+
 /**
  * Controls whether to truncate shares instead of rounding.
  */
@@ -360,35 +390,24 @@ enum class WaiveUnrealizedLoss : bool { No = false, Yes = true };
 assetsTotalForWithdrawal(SLE::ConstRef vault, WaiveUnrealizedLoss waive);
 
 /**
- * Returns true if debiting amount from total (the current value of a
- * vault's sfAssetsTotal or sfAssetsAvailable) would canonicalize to the
- * same STAmount value. This happens when amount is non-zero but too small
- * to change the stored total at STAmount's precision. Shares would still
- * move, so the ValidVault invariant would fail after apply; callers use
- * this to reject the transaction upfront instead.
- *
- * @param asset The vault's underlying asset, used to canonicalize both
- *              sides the same way the ledger will when the field is stored.
- * @param total The field's current value.
- * @param amount The amount to debit. Zero always returns false; that case
- *               is rejected separately.
- */
-[[nodiscard]] bool
-debitIsNonZeroDust(Asset const& asset, Number const& total, Number const& amount);
-
-/**
- * Returns the reference balance a cash outflow's dust check
- * (debitIsNonZeroDust) should compare against: FixedPrecision Vaults use
- * AssetsAvailable, the balance the cash actually leaves; Legacy/CashBasis
- * Vaults use the given AssetsTotal. Shared by VaultWithdraw and
- * VaultClawback.
+ * Reject a cash outflow that is dust (see debitIsNonZeroDust) or whose check
+ * overflows Number, which is easy to hit with a large Scale.
  *
  * @param vault The vault SLE.
- * @param assetsTotal The vault's current AssetsTotal, as already read by the
- *                     caller.
+ * @param amount The amount to debit.
+ * @param j Journal for the debug log.
+ * @param name Transaction name used as the log prefix.
+ *
+ * @return tesSUCCESS; tecPRECISION_LOSS if amount is dust; tecPATH_DRY if the
+ *         check overflows. Overflow means the transaction cannot apply, but
+ *         ledger state is still consistent.
  */
-[[nodiscard]] Number
-vaultDebitDustReference(SLE::ConstRef vault, Number const& assetsTotal);
+[[nodiscard]] TER
+checkDebitNotDust(
+    SLE::ConstRef vault,
+    Number const& amount,
+    beast::Journal j,
+    std::string_view name);
 
 /**
  * From the perspective of a vault, return the number of shares to demand from
@@ -483,8 +502,9 @@ decodeVaultVersion(std::optional<std::uint8_t> leVersion);
  *
  * @param rules The active ledger rules.
  *
- * @return VaultVersion::FixedPrecision once featureLendingProtocolV1_2,
- * fixCleanup3_2_0 and fixCleanup3_4_0 are all enabled; VaultVersion::CashBasis
+ * @return VaultVersion::FixedPrecision once featureLendingProtocolV1_1,
+ * featureLendingProtocolV1_2 and fixCleanup3_4_0 are all enabled;
+ * VaultVersion::CashBasis
  * once featureLendingProtocolV1_1 is enabled; VaultVersion::Legacy otherwise.
  */
 [[nodiscard]] VaultVersion

include/xrpl/protocol/ConfidentialTransfer.h

@@ -348,16 +348,19 @@ isAuditorMirrorCurrent(SLE const& issuance, SLE const& mptoken);
 areMirrorsCurrent(SLE const& issuance, SLE const& mptoken);
 
 /**
- * @brief Set the holder's issuer mirror epoch to match the issuance's current issuer key epoch.
+ * @brief Set the holder's issuer mirror epoch, and the issuer mirror key, to match the issuance's
+ * current key.
  *
  * Call this after writing the issuer mirror ciphertext under the issuance's
  * currently registered issuer key, so that the mirror reads as current afterwards.
+ * Also records sfIssuerMirrorEncryptionKey as the issuance's current issuer key
+ * (both fields stay absent at epoch 0, where the original issuer key applies).
  *
  * @param issuance The MPTokenIssuance ledger object.
  * @param mptoken  The holder's MPToken ledger entry to update.
  */
 void
-setIssuerMirrorEpoch(SLE const& issuance, SLE& mptoken);
+setIssuerMirrorCurrent(SLE const& issuance, SLE& mptoken);
 
 /**
  * @brief Set the holder's auditor mirror epoch to match the issuance's current auditor key epoch.
@@ -372,16 +375,18 @@ void
 setAuditorMirrorEpoch(SLE const& issuance, SLE& mptoken);
 
 /**
- * @brief Set the holder's MPToken mirror epochs to match the issuance's current key epochs.
+ * @brief Set the holder's MPToken mirror epochs, and the issuer mirror key, to match the issuance's
+ * current keys.
  *
  * Call this after writing mirror ciphertexts under the issuance's currently
- * registered keys, so that the mirrors read as current afterwards.
+ * registered keys, so that the mirrors read as current afterwards. Also records
+ * sfIssuerMirrorEncryptionKey via setIssuerMirrorCurrent.
  *
  * @param issuance The MPTokenIssuance ledger object.
  * @param mptoken  The holder's MPToken ledger entry to update.
  */
 void
-setMirrorEpochs(SLE const& issuance, SLE& mptoken);
+setMirrorsCurrent(SLE const& issuance, SLE& mptoken);
 
 /**
  * @brief Verifies revealed amount encryptions for all recipients.

include/xrpl/protocol/Fees.h

@@ -10,6 +10,25 @@ namespace xrpl {
 // This was the reference fee units used in the old fee calculation.
 inline constexpr std::uint32_t kFeeUnitsDeprecated = 10;
 
+// Number of micro-drops in one drop.
+inline constexpr std::uint32_t microDropsPerDrop{1'000'000};
+
+/**
+ * Hard protocol bounds on the Feature Extension fee settings. A voted value
+ * can never fall outside these, so `preflight`, which has no view, may bound
+ * against them. Gas and bytecode limits are capped; gas price has a floor
+ * (zero would make WASM execution effectively free).
+ */
+inline constexpr std::uint32_t kMaxGasLimit{2'000'000};
+inline constexpr std::uint32_t kMaxBytecodeSizeLimit{200'000};
+inline constexpr std::uint32_t kMinGasPrice{1};
+
+// The following default values of fee settings will seed into FeeSettings
+// and write to the ledger on featureSmartEscrow activation.
+inline constexpr std::uint32_t kDefaultGasLimit{1'000'000};
+inline constexpr std::uint32_t kDefaultBytecodeSizeLimit{100'000};
+inline constexpr std::uint32_t kDefaultGasPrice{1'000'000};
+
 /**
  * Reflects the fee settings for a particular ledger.
  *
@@ -33,13 +52,47 @@ struct Fees
      */
     XRPAmount increment{0};
 
+    /**
+     * @brief Gas limit for Feature Extensions (instructions).
+     *
+     * This and the one below default to the protocol values rather than 0,
+     * because an explicit 0 is the voted kill switch.
+     */
+    std::uint32_t gasLimit{kDefaultGasLimit};
+
+    /**
+     * @brief Bytecode size limit for Feature Extensions (bytes).
+     */
+    std::uint32_t bytecodeSizeLimit{kDefaultBytecodeSizeLimit};
+
+    /**
+     * @brief Price of WASM gas (micro-drops).
+     */
+    std::uint32_t gasPrice{kDefaultGasPrice};
+
     explicit Fees() = default;
     Fees(Fees const&) = default;
     Fees&
     operator=(Fees const&) = default;
 
     Fees(XRPAmount base, XRPAmount reserve, XRPAmount increment)
-        : base(base), reserve(reserve), increment(increment)
+        : base{base}, reserve{reserve}, increment{increment}
+    {
+    }
+
+    Fees(
+        XRPAmount base,
+        XRPAmount reserve,
+        XRPAmount increment,
+        std::uint32_t gasLimit,
+        std::uint32_t bytecodeSizeLimit,
+        std::uint32_t gasPrice)
+        : base{base}
+        , reserve{reserve}
+        , increment{increment}
+        , gasLimit{gasLimit}
+        , bytecodeSizeLimit{bytecodeSizeLimit}
+        , gasPrice{gasPrice}
     {
     }
 

include/xrpl/protocol/Protocol.h

@@ -317,12 +317,12 @@ constexpr std::uint8_t kVaultDefaultIouScale = 6;
  * Chosen so 1 IOU can always convert to shares:
  * 10^19 > maxMPTokenAmount (2^64-1) > 10^18.
  */
-constexpr std::uint8_t kVaultMaximumIouScale = 18;
+constexpr std::uint8_t kLegacyVaultMaximumIouScale = 18;
 
 /**
  * Maximum Scale for a Vault created under featureLendingProtocolV1_2.
  */
-constexpr std::uint8_t kVaultMaximumFixedPrecisionIouScale = 10;
+constexpr std::uint8_t kFixedPrecisionVaultMaximumIouScale = 10;
 
 /**
  * Vault ledger-entry schema versions, persisted as sfLEVersion.

include/xrpl/protocol/STAmount.h

@@ -696,6 +696,16 @@ divRound(STAmount const& v1, STAmount const& v2, Asset const& asset, bool roundU
 STAmount
 divRoundStrict(STAmount const& v1, STAmount const& v2, Asset const& asset, bool roundUp);
 
+/**
+ * Returns amt * num / den, rounded in the requested direction.
+ *
+ * Dispatches to the XRPAmount, IOUAmount or MPTAmount overload. XRP and MPT
+ * results are exact; an IOU result is rounded to the 16-digit mantissa in the
+ * requested direction. Only Upward and Downward are supported.
+ */
+[[nodiscard]] STAmount
+mulRatio(STAmount const& amt, std::uint32_t num, std::uint32_t den, Number::RoundingMode rounding);
+
 // Someone is offering X for Y, what is the rate?
 // Rate: smaller is better, the taker wants the most out: in/out
 // VFALCO TODO Return a Quality object

include/xrpl/protocol/TER.h

@@ -231,6 +231,8 @@ enum TERcodes : TERUnderlyingType {
     terNO_DELEGATE_PERMISSION,  // Delegate does not have permission
     terLOCKED,                  // MPT is locked
     terNO_PERMISSION,           // No permission but retry
+    terTICKET_RESERVED,         // Ticket is reserved and cannot be consumed
+                                // until the reservation is released
 };
 
 //------------------------------------------------------------------------------

include/xrpl/protocol/XRPAmount.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <xrpl/basics/MathUtilities.h>
 #include <xrpl/basics/Number.h>
 #include <xrpl/basics/contract.h>
 #include <xrpl/beast/utility/Zero.h>
@@ -69,7 +70,13 @@ public:
     constexpr XRPAmount
     operator*(value_type const& rhs) const
     {
-        return XRPAmount{drops_ * rhs};
+        if (auto const result = checkedMul(drops_, rhs))
+            return XRPAmount{*result};
+        // Not reached in constant evaluation: an overflowing constant
+        // expression fails to compile instead.
+        XRPAmount product{*this};
+        product *= rhs;
+        return product;
     }
 
     friend constexpr XRPAmount
@@ -82,37 +89,23 @@ public:
     XRPAmount&
     operator+=(XRPAmount const& other)
     {
-        drops_ += other.drops();
-        return *this;
+        return *this += other.drops();
     }
 
     XRPAmount&
     operator-=(XRPAmount const& other)
     {
-        drops_ -= other.drops();
-        return *this;
+        return *this -= other.drops();
     }
 
     XRPAmount&
-    operator+=(value_type const& rhs)
-    {
-        drops_ += rhs;
-        return *this;
-    }
+    operator+=(value_type const& rhs);
 
     XRPAmount&
-    operator-=(value_type const& rhs)
-    {
-        drops_ -= rhs;
-        return *this;
-    }
+    operator-=(value_type const& rhs);
 
     XRPAmount&
-    operator*=(value_type const& rhs)
-    {
-        drops_ *= rhs;
-        return *this;
-    }
+    operator*=(value_type const& rhs);
 
     XRPAmount
     operator-() const

include/xrpl/protocol/detail/features.macro

@@ -61,7 +61,6 @@ XRPL_FIX    (InnerObjTemplate2,          Supported::Yes, VoteBehavior::DefaultNo
 XRPL_FIX    (EnforceNFTokenTrustline,    Supported::Yes, VoteBehavior::DefaultNo)
 XRPL_FIX    (ReducedOffersV2,            Supported::Yes, VoteBehavior::DefaultNo)
 XRPL_FEATURE(NFTokenMintOffer,           Supported::Yes, VoteBehavior::DefaultNo)
-XRPL_FIX    (AMMv1_1,                    Supported::Yes, VoteBehavior::DefaultNo)
 XRPL_FIX    (PreviousTxnID,              Supported::Yes, VoteBehavior::DefaultNo)
 XRPL_FIX    (XChainRewardRounding,       Supported::Yes, VoteBehavior::DefaultNo)
 XRPL_FIX    (EmptyDID,                   Supported::Yes, VoteBehavior::DefaultNo)
@@ -107,6 +106,7 @@ XRPL_RETIRE_FIX(1623)
 XRPL_RETIRE_FIX(1781)
 XRPL_RETIRE_FIX(AmendmentMajorityCalc)
 XRPL_RETIRE_FIX(AMMOverflowOffer)
+XRPL_RETIRE_FIX(AMMv1_1)
 XRPL_RETIRE_FIX(CheckThreading)
 XRPL_RETIRE_FIX(DisallowIncomingV1)
 XRPL_RETIRE_FIX(InnerObjTemplate)

include/xrpl/protocol/detail/ledger_entries.macro

@@ -417,6 +417,7 @@ LEDGER_ENTRY(ltMPTOKEN_ISSUANCE, 0x007e, MPTokenIssuance, mpt_issuance, ({
     {sfAuditorEncryptionKey,     SoeOptional},
     {sfIssuerKeyEpoch,           SoeOptional},
     {sfAuditorKeyEpoch,          SoeOptional},
+    {sfInitialIssuerEncryptionKey, SoeOptional},
     {sfConfidentialOutstandingAmount, SoeDefault},
 }))
 
@@ -438,6 +439,7 @@ LEDGER_ENTRY(ltMPTOKEN, 0x007f, MPToken, mptoken, ({
     {sfAuditorEncryptedBalance,     SoeOptional},
     {sfIssuerKeyMirrorEpoch,        SoeOptional},
     {sfAuditorKeyMirrorEpoch,       SoeOptional},
+    {sfIssuerMirrorEncryptionKey,   SoeOptional},
     {sfHolderEncryptionKey,         SoeOptional},
     {sfRecoveryKey,                 SoeOptional},
 }))

include/xrpl/protocol/detail/sfields.macro

@@ -333,6 +333,8 @@ TYPED_SFIELD(sfAmountCommitment,            VL,     45)
 TYPED_SFIELD(sfBalanceCommitment,           VL,     46)
 TYPED_SFIELD(sfBytecode,                    VL,     47)
 TYPED_SFIELD(sfRecoveryKey,                 VL,     48)
+TYPED_SFIELD(sfInitialIssuerEncryptionKey,  VL,     49)
+TYPED_SFIELD(sfIssuerMirrorEncryptionKey,   VL,     50)
 
 // account (common)
 TYPED_SFIELD(sfAccount,                  ACCOUNT,    1)

include/xrpl/protocol/detail/transactions.macro

@@ -1175,6 +1175,20 @@ TRANSACTION(ttTRANSACTION_PROPOSAL_CREATE, 95, TransactionProposalCreate,
     {sfExpiration, SoeRequired},
 }))
 
+// ttTRANSACTION_PROPOSAL_SIGN arrives in a later PR and takes the next unassigned type.
+
+/** This transaction deletes a TransactionProposal, releasing its owner's
+    reserve. While the proposal is live only its Owner or its target account
+    may cancel; once it is terminal anyone may (On-Chain Cosigner spec §7). */
+#if TRANSACTION_INCLUDE
+#   include <xrpl/tx/transactors/proposal/TransactionProposalCancel.h>
+#endif
+TRANSACTION(ttTRANSACTION_PROPOSAL_CANCEL, 94, TransactionProposalCancel,
+    ({.amendment = featureCosign}),
+    ({
+    {sfProposalID, SoeRequired},
+}))
+
 /** This system-generated transaction type is used to update the status of the various amendments.
 
     For details, see: https://xrpl.org/amendments.html

include/xrpl/protocol/jss.h

@@ -252,6 +252,9 @@ JSS(expected_date);                  // out: any (warnings)
 JSS(expected_date_UTC);              // out: any (warnings)
 JSS(expected_ledger_size);           // out: TxQ
 JSS(expiration);                     // out: AccountOffers, AccountChannels, ValidatorList, amm_info
+JSS(gas_limit);                      // out: NetworkOPs
+JSS(bytecode_size_limit);            // out: NetworkOPs
+JSS(gas_price);                      // out: NetworkOPs
 JSS(fail_hard);                      // in: Sign, Submit
 JSS(failed);                         // out: InboundLedger
 JSS(feature);                        // in: Feature

include/xrpl/protocol_autogen/ledger_entries/MPToken.h

@@ -316,6 +316,30 @@ public:
         return this->sle_->isFieldPresent(sfAuditorKeyMirrorEpoch);
     }
 
+    /**
+     * @brief Get sfIssuerMirrorEncryptionKey (SoeOptional)
+     * @return The field value, or std::nullopt if not present.
+     */
+    [[nodiscard]]
+    protocol_autogen::Optional<SF_VL::type::value_type>
+    getIssuerMirrorEncryptionKey() const
+    {
+        if (hasIssuerMirrorEncryptionKey())
+            return this->sle_->at(sfIssuerMirrorEncryptionKey);
+        return std::nullopt;
+    }
+
+    /**
+     * @brief Check if sfIssuerMirrorEncryptionKey is present.
+     * @return True if the field is present, false otherwise.
+     */
+    [[nodiscard]]
+    bool
+    hasIssuerMirrorEncryptionKey() const
+    {
+        return this->sle_->isFieldPresent(sfIssuerMirrorEncryptionKey);
+    }
+
     /**
      * @brief Get sfHolderEncryptionKey (SoeOptional)
      * @return The field value, or std::nullopt if not present.
@@ -565,6 +589,17 @@ public:
         return *this;
     }
 
+    /**
+     * @brief Set sfIssuerMirrorEncryptionKey (SoeOptional)
+     * @return Reference to this builder for method chaining.
+     */
+    MPTokenBuilder&
+    setIssuerMirrorEncryptionKey(std::decay_t<typename SF_VL::type::value_type> const& value)
+    {
+        object_[sfIssuerMirrorEncryptionKey] = value;
+        return *this;
+    }
+
     /**
      * @brief Set sfHolderEncryptionKey (SoeOptional)
      * @return Reference to this builder for method chaining.

include/xrpl/protocol_autogen/ledger_entries/MPTokenIssuance.h

@@ -399,6 +399,30 @@ public:
         return this->sle_->isFieldPresent(sfAuditorKeyEpoch);
     }
 
+    /**
+     * @brief Get sfInitialIssuerEncryptionKey (SoeOptional)
+     * @return The field value, or std::nullopt if not present.
+     */
+    [[nodiscard]]
+    protocol_autogen::Optional<SF_VL::type::value_type>
+    getInitialIssuerEncryptionKey() const
+    {
+        if (hasInitialIssuerEncryptionKey())
+            return this->sle_->at(sfInitialIssuerEncryptionKey);
+        return std::nullopt;
+    }
+
+    /**
+     * @brief Check if sfInitialIssuerEncryptionKey is present.
+     * @return True if the field is present, false otherwise.
+     */
+    [[nodiscard]]
+    bool
+    hasInitialIssuerEncryptionKey() const
+    {
+        return this->sle_->isFieldPresent(sfInitialIssuerEncryptionKey);
+    }
+
     /**
      * @brief Get sfConfidentialOutstandingAmount (SoeDefault)
      * @return The field value, or std::nullopt if not present.
@@ -670,6 +694,17 @@ public:
         return *this;
     }
 
+    /**
+     * @brief Set sfInitialIssuerEncryptionKey (SoeOptional)
+     * @return Reference to this builder for method chaining.
+     */
+    MPTokenIssuanceBuilder&
+    setInitialIssuerEncryptionKey(std::decay_t<typename SF_VL::type::value_type> const& value)
+    {
+        object_[sfInitialIssuerEncryptionKey] = value;
+        return *this;
+    }
+
     /**
      * @brief Set sfConfidentialOutstandingAmount (SoeDefault)
      * @return Reference to this builder for method chaining.

include/xrpl/protocol_autogen/transactions/TransactionProposalCancel.h

@@ -0,0 +1,131 @@
+// This file is auto-generated. Do not edit.
+#pragma once
+
+#include <xrpl/protocol/STTx.h>
+#include <xrpl/protocol/STParsedJSON.h>
+#include <xrpl/protocol/jss.h>
+#include <xrpl/protocol_autogen/TransactionBase.h>
+#include <xrpl/protocol_autogen/TransactionBuilderBase.h>
+#include <xrpl/json/json_value.h>
+
+#include <stdexcept>
+#include <optional>
+
+namespace xrpl::transactions {
+
+class TransactionProposalCancelBuilder;
+
+/**
+ * @brief Transaction: TransactionProposalCancel
+ *
+ * Type: ttTRANSACTION_PROPOSAL_CANCEL (94)
+ * Delegable: Delegation::NotDelegable
+ * Amendment: featureCosign
+ * Privileges: Privilege::NoPriv
+ *
+ * Immutable wrapper around STTx providing type-safe field access.
+ * Use TransactionProposalCancelBuilder to construct new transactions.
+ */
+class TransactionProposalCancel : public TransactionBase
+{
+public:
+    static constexpr xrpl::TxType txType = ttTRANSACTION_PROPOSAL_CANCEL;
+
+    /**
+     * @brief Construct a TransactionProposalCancel transaction wrapper from an existing STTx object.
+     * @throws std::runtime_error if the transaction type doesn't match.
+     */
+    explicit TransactionProposalCancel(std::shared_ptr<STTx const> tx)
+        : TransactionBase(std::move(tx))
+    {
+        // Verify transaction type
+        if (tx_->getTxnType() != txType)
+        {
+            throw std::runtime_error("Invalid transaction type for TransactionProposalCancel");
+        }
+    }
+
+    // Transaction-specific field getters
+
+    /**
+     * @brief Get sfProposalID (SoeRequired)
+     * @return The field value.
+     */
+    [[nodiscard]]
+    SF_UINT256::type::value_type
+    getProposalID() const
+    {
+        return this->tx_->at(sfProposalID);
+    }
+};
+
+/**
+ * @brief Builder for TransactionProposalCancel transactions.
+ *
+ * Provides a fluent interface for constructing transactions with method chaining.
+ * Uses STObject internally for flexible transaction construction.
+ * Inherits common field setters from TransactionBuilderBase.
+ */
+class TransactionProposalCancelBuilder : public TransactionBuilderBase<TransactionProposalCancelBuilder>
+{
+public:
+    /**
+     * @brief Construct a new TransactionProposalCancelBuilder with required fields.
+     * @param account The account initiating the transaction.
+     * @param proposalID The sfProposalID field value.
+     * @param sequence Optional sequence number for the transaction.
+     * @param fee Optional fee for the transaction.
+     */
+    TransactionProposalCancelBuilder(SF_ACCOUNT::type::value_type account,
+                     std::decay_t<typename SF_UINT256::type::value_type> const& proposalID,                    std::optional<SF_UINT32::type::value_type> sequence = std::nullopt,
+                    std::optional<SF_AMOUNT::type::value_type> fee = std::nullopt
+)
+        : TransactionBuilderBase<TransactionProposalCancelBuilder>(ttTRANSACTION_PROPOSAL_CANCEL, account, sequence, fee)
+    {
+        setProposalID(proposalID);
+    }
+
+    /**
+     * @brief Construct a TransactionProposalCancelBuilder from an existing STTx object.
+     * @param tx The existing transaction to copy from.
+     * @throws std::runtime_error if the transaction type doesn't match.
+     */
+    TransactionProposalCancelBuilder(std::shared_ptr<STTx const> tx)
+    {
+        if (tx->getTxnType() != ttTRANSACTION_PROPOSAL_CANCEL)
+        {
+            throw std::runtime_error("Invalid transaction type for TransactionProposalCancelBuilder");
+        }
+        object_ = *tx;
+    }
+
+    /**
+     * @brief Transaction-specific field setters
+     */
+
+    /**
+     * @brief Set sfProposalID (SoeRequired)
+     * @return Reference to this builder for method chaining.
+     */
+    TransactionProposalCancelBuilder&
+    setProposalID(std::decay_t<typename SF_UINT256::type::value_type> const& value)
+    {
+        object_[sfProposalID] = value;
+        return *this;
+    }
+
+    /**
+     * @brief Build and return the TransactionProposalCancel wrapper.
+     * @param publicKey The public key for signing.
+     * @param secretKey The secret key for signing.
+     * @return The constructed transaction wrapper.
+     */
+    TransactionProposalCancel
+    build(PublicKey const& publicKey, SecretKey const& secretKey)
+    {
+        sign(publicKey, secretKey);
+        return TransactionProposalCancel{std::make_shared<STTx>(std::move(object_))};
+    }
+};
+
+}  // namespace xrpl::transactions

include/xrpl/shamap/FullBelowCache.h

@@ -3,9 +3,12 @@
 #include <xrpl/basics/KeyCache.h>
 #include <xrpl/basics/TaggedCache.h>
 #include <xrpl/basics/base_uint.h>
+#include <xrpl/basics/partitioned_unordered_map.h>
+#include <xrpl/beast/hash/hash_append.h>
 #include <xrpl/beast/insight/Collector.h>
 #include <xrpl/beast/insight/NullCollector.h>
 #include <xrpl/beast/utility/Journal.h>
+#include <xrpl/shamap/SHAMapNodeID.h>
 
 #include <atomic>
 #include <chrono>
@@ -15,6 +18,112 @@
 
 namespace xrpl {
 
+/**
+ * Names a subtree whose descendants are all resident, by hash and by position.
+ *
+ * A node's hash covers its children but neither its depth nor its path, and one
+ * cache answers for every map built from a NodeFamily, so the position is what
+ * makes a hit answer for the position asked about and no other. The depth is
+ * kept beside the id because SHAMapNodeID masks its id to its own depth, so an
+ * all-zero id belongs to the root and to every all-zero prefix alike.
+ *
+ * Held as two fields rather than as a SHAMapNodeID, which is a CountedObject:
+ * one per entry would report the cache's population as live node IDs in the
+ * get_counts RPC, and would put an atomic increment on every temporary key a
+ * lookup builds.
+ */
+struct FullBelowKey
+{
+    /**
+     * The hash of the subtree.
+     */
+    UInt256 hash;
+
+    /**
+     * The masked id of the node the subtree was completed at.
+     */
+    UInt256 position;
+
+    /**
+     * The depth of that node.
+     */
+    std::uint32_t depth{0};
+
+    /**
+     * @param subtreeHash The hash of the subtree whose descendants are all
+     *        resident.
+     * @param nodeID The node the subtree was completed at.
+     */
+    FullBelowKey(UInt256 const& subtreeHash, SHAMapNodeID const& nodeID)
+        : hash(subtreeHash)
+        , position(nodeID.getNodeID())
+        , depth(static_cast<std::uint32_t>(nodeID.getDepth()))
+    {
+    }
+
+    /**
+     * The same key, named by the node above the position and the branch taken.
+     *
+     * Produces the fields the constructor above would for that child's own node
+     * ID, so the two forms name one entry.
+     *
+     * @param subtreeHash The hash of the subtree that is fully resident.
+     * @param parentID The node above the one the subtree was completed at.
+     * @param branch The branch of that node leading to it.
+     */
+    FullBelowKey(UInt256 const& subtreeHash, SHAMapNodeID const& parentID, unsigned int branch)
+        : hash(subtreeHash)
+        , position(childNodeID(parentID.getNodeID(), parentID.getDepth(), branch))
+        , depth(static_cast<std::uint32_t>(parentID.getDepth() + 1))
+    {
+    }
+
+    [[nodiscard]] bool
+    operator==(FullBelowKey const& other) const = default;
+};
+
+// The per-entry cost of this cache is computed from these sizes, so pin the layout that arithmetic
+// assumes: the three fields sit back to back with no padding.
+static_assert(
+    sizeof(FullBelowKey) == (2 * sizeof(UInt256)) + sizeof(std::uint32_t),
+    "FullBelowKey must stay free of padding");
+static_assert(
+    alignof(FullBelowKey) == alignof(std::uint32_t),
+    "FullBelowKey's lack of padding rests on its alignment");
+
+/**
+ * Feed a key to a hasher, field by field.
+ *
+ * Written out rather than hashed in one call over the object's bytes, since
+ * beast::IsUniquelyRepresented is opt-in per type and has no case for a
+ * user-defined struct, whatever its layout.
+ *
+ * @param h The hasher to feed.
+ * @param key The key to hash.
+ */
+template <class Hasher>
+void
+hash_append(Hasher& h, FullBelowKey const& key) noexcept
+{
+    using beast::hash_append;
+    hash_append(h, key.hash, key.position, key.depth);
+}
+
+/**
+ * Choose which partition of the cache's map a key lives in.
+ *
+ * Taken from the subtree hash, which is already uniformly distributed.
+ *
+ * @param key The key to place.
+ * @return The value PartitionedUnorderedMap reduces by its partition count.
+ */
+template <>
+inline std::size_t
+extract(FullBelowKey const& key)
+{
+    return extract(key.hash);
+}
+
 namespace detail {
 
 /**
@@ -24,12 +133,12 @@ namespace detail {
 class BasicFullBelowCache
 {
 private:
-    using CacheType = KeyCache;
+    using CacheType = KeyCache<FullBelowKey>;
 
 public:
     static constexpr auto kDefaultCacheTargetSize = 0;
 
-    using key_type = UInt256;
+    using key_type = FullBelowKey;
     using ClockType = CacheType::ClockType;
 
     /**
@@ -86,13 +195,15 @@ public:
      * Refresh the last access time of an item, if it exists.
      * Thread safety:
      *     Safe to call from any thread.
-     * @param key The key to refresh.
-     * @return `true` If the key exists.
+     * @param hash The hash of the subtree to ask about.
+     * @param parentID The node above the position to ask about it at.
+     * @param branch The branch of that node leading to that position.
+     * @return `true` If that subtree is recorded as resident at that position.
      */
     bool
-    touchIfExists(key_type const& key)
+    touchIfExists(UInt256 const& hash, SHAMapNodeID const& parentID, unsigned int branch)
     {
-        return cache_.touchIfExists(key);
+        return cache_.touchIfExists(key_type{hash, parentID, branch});
     }
 
     /**
@@ -101,12 +212,13 @@ public:
      * be refreshed.
      * Thread safety:
      *     Safe to call from any thread.
-     * @param key The key to insert.
+     * @param hash The hash of the subtree whose descendants are all resident.
+     * @param nodeID The node that subtree was completed at.
      */
     void
-    insert(key_type const& key)
+    insert(UInt256 const& hash, SHAMapNodeID const& nodeID)
     {
-        cache_.insert(key);
+        cache_.insert(key_type{hash, nodeID});
     }
 
     /**

include/xrpl/shamap/README.md

@@ -278,11 +278,14 @@ This cache remembers which trie keys have all of their children resident in a
 when creating the missing nodes list. Missing nodes are those nodes that a
 `SHAMap` refers to but that are not stored in the local database.
 
-As a depth-first walk of a `SHAMap` is performed, if an inner node answers true to
-`isFullBelow()` then it is known that none of this node's children are missing
-nodes, and thus that subtree does not need to be walked. These nodes are stored
-in the FullBelowCache. Subsequent walks check the FullBelowCache first when
-encountering a node, and ignore that subtree if found.
+As a depth-first walk of a `SHAMap` completes an inner node, meaning none of the
+nodes below it are missing, the node's hash and position are stored in the
+FullBelowCache. Subsequent walks check the FullBelowCache when encountering a
+child, and skip that subtree if found. The entry is keyed by position as well as
+hash, since a hash commits to a node's contents rather than its place, and the
+same node object is shared by hash between maps and positions. For the same
+reason the inner node's own `isFullBelow()` flag is written and read for a
+walk's root alone, where the position is fixed.
 
 ## `SHAMapTreeNode`
 

include/xrpl/shamap/SHAMap.h

@@ -2,6 +2,7 @@
 
 #include <xrpl/basics/Blob.h>
 #include <xrpl/basics/IntrusivePointer.h>
+#include <xrpl/basics/Log.h>
 #include <xrpl/basics/SHAMapHash.h>
 #include <xrpl/basics/base_uint.h>
 #include <xrpl/beast/utility/Journal.h>
@@ -17,6 +18,7 @@
 #include <xrpl/shamap/SHAMapNodeID.h>
 #include <xrpl/shamap/SHAMapTreeNode.h>
 
+#include <atomic>
 #include <condition_variable>
 #include <cstddef>
 #include <cstdint>
@@ -30,6 +32,7 @@
 #include <set>
 #include <stack>
 #include <tuple>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -40,7 +43,7 @@ class SHAMapSyncFilter;
 /**
  * Describes the current state of a given SHAMap
  */
-enum class SHAMapState {
+enum class SHAMapState : std::uint8_t {
     /**
      * The map is in flux and objects can be added and removed.
      *
@@ -71,20 +74,21 @@ enum class SHAMapState {
 };
 
 /**
- * A SHAMap is both a radix tree with a fan-out of 16 and a Merkle tree.
+ * A SHAMap is both a trie with a fan-out of 16 and a Merkle tree.
  *
- * A radix tree is a tree with two properties:
+ * A trie holds a key in the position of its nodes: the path from the root down
+ * to a node spells out the prefix every key below it shares (the "prefix
+ * property"). A SHAMap spends one nibble of the 256-bit key per level, so an
+ * inner node has at most 16 children and a leaf sits at depth 64 at the
+ * deepest. A leaf also carries its own full key, so a reader can check that it
+ * was reached through the branches that key names.
  *
- *   1. The key for a node is represented by the node's position in the tree
- *      (the "prefix property").
- *   2. A node with only one child is merged with that child
- *      (the "merge property")
+ * An insert creates an inner node at every nibble two keys share, and a delete
+ * collapses a chain that reduces to one leaf. Every edge spans exactly one
+ * nibble, so a path has one entry per level and 65 entries at the most, and a
+ * path's length names each node's depth. Traversal relies on that.
  *
- * These properties result in a significantly smaller memory footprint for
- * a radix tree.
- *
- * A fan-out of 16 means that each node in the tree has at most 16
- * children. See https://en.wikipedia.org/wiki/Radix_tree
+ * See https://en.wikipedia.org/wiki/Trie
  *
  * A Merkle tree is a tree where each non-leaf node is labelled with the hash
  * of the combined labels of its children nodes.
@@ -120,21 +124,43 @@ private:
      */
     std::uint32_t cowid_ = 1;
 
+    // ledgerSeq_, state_ and full_ are touched on the nodestore fetch path and on a
+    // getMissingNodes() walk, neither of which may block, so pin them lock-free.
+    static_assert(std::atomic<std::uint32_t>::is_always_lock_free);
+    static_assert(std::atomic<SHAMapState>::is_always_lock_free);
+    static_assert(std::atomic<bool>::is_always_lock_free);
+
     /**
      * The sequence of the ledger that this map references, if any.
+     *
+     * Written by Ledger::setFull() and by InboundLedger, and read on a
+     * nodestore reader thread. Relaxed both ways, since it is only a lookup
+     * hint for a store keyed by hash.
      */
-    std::uint32_t ledgerSeq_ = 0;
+    std::atomic<std::uint32_t> ledgerSeq_ = 0;
 
     SHAMapTreeNodePtr root_;
-    mutable SHAMapState state_;
+
+    /**
+     * The map's state. Atomic because a getMissingNodes() walk writes it with
+     * the acquisition's lock released. Mutable because a const descend() can
+     * record the Invalid verdict.
+     */
+    mutable std::atomic<SHAMapState> state_;
     SHAMapType const type_;
-    bool backed_ = true;         // Map is backed by the database
-    mutable bool full_ = false;  // Map is believed complete in database
+    bool backed_ = true;  // Map is backed by the database
+
+    /**
+     * Map is believed complete in database.
+     *
+     * Atomic because finishFetch() clears it on any nodestore reader thread,
+     * several of which can run at once.
+     */
+    mutable std::atomic<bool> full_ = false;
 
 public:
     /**
-     * Number of children each non-leaf node has (the 'radix tree' part of the
-     * map)
+     * Number of children each non-leaf node has, which is the trie's fan-out
      */
     static constexpr unsigned int kBranchFactor = SHAMapInnerNode::kBranchFactor;
 
@@ -143,6 +169,18 @@ public:
      */
     static constexpr unsigned int kLeafDepth = 64;
 
+    /**
+     * Whether only a leaf may occupy a position at `depth`.
+     *
+     * @param depth the depth to judge.
+     * @return whether that depth is at or past kLeafDepth.
+     */
+    [[nodiscard]] static constexpr bool
+    isLeafDepth(unsigned int depth)
+    {
+        return depth >= kLeafDepth;
+    }
+
     using DeltaItem =
         std::pair<boost::intrusive_ptr<SHAMapItem const>, boost::intrusive_ptr<SHAMapItem const>>;
     using Delta = std::map<UInt256, DeltaItem>;
@@ -152,7 +190,14 @@ public:
     SHAMap&
     operator=(SHAMap const&) = delete;
 
-    // Take a snapshot of the given map:
+    /**
+     * Take a snapshot of the given map.
+     *
+     * @param other The map to snapshot. An Invalid source yields an Invalid
+     *        snapshot.
+     * @param isMutable Whether the snapshot may be modified. Ignored when other
+     *        is Invalid.
+     */
     SHAMap(SHAMap const& other, bool isMutable);
 
     // build new map
@@ -190,17 +235,33 @@ public:
 
     //--------------------------------------------------------------------------
 
-    // Returns a new map that's a snapshot of this one.
-    // Handles copy on write for mutable snapshots.
+    /**
+     * Return a new map that is a snapshot of this one.
+     *
+     * Handles copy on write for mutable snapshots. An invalid map yields an
+     * invalid snapshot.
+     *
+     * @param isMutable Whether the snapshot may be modified.
+     * @return The snapshot.
+     */
     std::shared_ptr<SHAMap>
     snapShot(bool isMutable) const;
 
-    /*  Mark this SHAMap as "should be full", indicating
-        that the local server wants all the corresponding nodes
-        in durable storage.
-    */
+    /**
+     * Mark this map as "should be full": the local server wants every node
+     * it references in durable storage, so a nodestore miss is a gap to report.
+     *
+     * Publishes the ledger sequence before the flag. The sequence store is
+     * relaxed and the flag store is release, and finishFetch() reads the
+     * sequence only after acquiring the flag, so the one miss that withdraws
+     * the flag always reports the sequence stored here. Keeping both stores in
+     * one place is what makes that order impossible to get wrong.
+     *
+     * @param ledgerSeq Sequence of the ledger this map belongs to, which the
+     *        gap report names.
+     */
     void
-    setFull();
+    setFull(std::uint32_t ledgerSeq);
 
     void
     setLedgerSeq(std::uint32_t lseq);
@@ -243,9 +304,11 @@ public:
     /**
      * Find the first item after the given item.
      *
-     * @param id the identifier of the item.
-     *
-     * @note The item does not need to exist.
+     * @param id the identifier of the item, which need not exist in the map.
+     * @return an iterator at the first item with a greater key, or end() if the
+     *         map holds no greater key.
+     * @throws SHAMapMissingNode if the map cannot be walked. end() is the
+     *         separate answer that the map holds no greater key.
      */
     ConstIterator
     upperBound(UInt256 const& id) const;
@@ -253,9 +316,11 @@ public:
     /**
      * Find the object with the greatest object id smaller than the input id.
      *
-     * @param id the identifier of the item.
-     *
-     * @note The item does not need to exist.
+     * @param id the identifier of the item, which need not exist in the map.
+     * @return an iterator at the last item with a smaller key, or end() if the
+     *         map holds no smaller key.
+     * @throws SHAMapMissingNode if the map cannot be walked. end() is the
+     *         separate answer that the map holds no smaller key.
      */
     ConstIterator
     lowerBound(UInt256 const& id) const;
@@ -296,9 +361,13 @@ public:
      * concurrency, to discover nodes referenced in the
      * SHAMap but not available locally.
      *
+     * Only a leaf may occupy a position at or beyond kLeafDepth. A map that
+     * breaks that is marked Invalid and the traversal is abandoned, so callers
+     * ask isValid() to tell an empty result from a satisfied map.
+     *
      * @param maxNodes The maximum number of found nodes to return
      * @param filter The filter to use when retrieving nodes
-     * @param return The nodes known to be missing
+     * @return The nodes known to be missing, or empty if the map is Invalid
      */
     std::vector<std::pair<SHAMapNodeID, UInt256>>
     getMissingNodes(int maxNodes, SHAMapSyncFilter const* filter);
@@ -341,6 +410,9 @@ public:
      * This function is used when receiving the root node of a SHAMap from a peer during ledger
      * synchronization. The node must already have been deserialized.
      *
+     * A root offered under a hash the map does not hold names another tree and
+     * is reported as invalid data. A root matching that hash is a duplicate.
+     *
      * @param hash The expected hash of the root node.
      * @param rootNode A deserialized root node to add.
      * @param filter Optional sync filter to track received nodes.
@@ -360,14 +432,26 @@ public:
      * is inserted at the position specified by nodeID. The node must already have been
      * deserialized.
      *
+     * A node that no valid tree can hold makes the map Invalid, which is
+     * terminal. An acquisition reaching that verdict gives up.
+     *
      * @param nodeID The position in the tree where this node belongs.
      * @param treeNode A deserialized tree node to add.
      * @param filter Optional sync filter to track received nodes.
      * @return Status indicating whether the node was useful, duplicate, or invalid.
      *
-     * @note This function expects the treeNode to be a valid, deserialized SHAMapTreeNode. The
-     *       caller is responsible for deserialization and basic validation before calling this
-     *       function. This also means that the nodeID must be consistent with the node's content.
+     * @note The caller is responsible for deserialization. The position is
+     *       checked here, in three steps that share two verdicts. A node
+     *       the descent reaches at a position other than the one nodeID
+     *       claims is refused with invalid(), and the map stays valid, since
+     *       only the label was wrong. A leaf that hash-verified at the
+     *       position nodeID claims, but whose own key does not lie under
+     *       nodeID, condemns the map and returns mapInvalidated(). A node the
+     *       descent itself condemns on the way, resolved from the local store
+     *       or the filter rather than supplied by the caller, leaves the map
+     *       Invalid and returns invalid(), since that verdict is not the
+     *       caller's doing. Any map outside Synching, including one already
+     *       condemned, returns duplicate().
      */
     SHAMapAddNode
     addKnownNode(
@@ -375,16 +459,57 @@ public:
         SHAMapTreeNodePtr treeNode,
         SHAMapSyncFilter const* filter);
 
-    // status functions
-    void
+    /**
+     * Mark this map as immutable, so it can no longer be modified.
+     *
+     * @return false if the map is Invalid and was left unchanged, true
+     *         otherwise.
+     */
+    [[nodiscard]] bool
     setImmutable();
-    bool
+
+    /**
+     * @return Whether the map is being synced against a hash it was given, so
+     *         its hash is fixed while nodes may still be added.
+     */
+    [[nodiscard]] bool
     isSynching() const;
+
+    /**
+     * @return Whether the map is settled, with its hash and nodes fixed.
+     */
+    [[nodiscard]] bool
+    isImmutable() const;
+
+    /**
+     * Mark this map as syncing, fixing its hash while still allowing missing
+     * nodes to be added.
+     *
+     * The map must be freshly constructed. The body asserts that the map is not
+     * Invalid, so a caller that ignores the precondition stops a build with
+     * assertions enabled.
+     */
     void
     setSynching();
+
+    /**
+     * Mark this map as no longer syncing, so it can be modified again.
+     *
+     * Moves only a Synching map. An Immutable map stays settled, a Modifying
+     * map has nothing to clear, and Invalid is terminal.
+     */
     void
     clearSynching();
-    bool
+
+    /**
+     * Whether the map can still be the map it claims to be.
+     *
+     * A map that is merely missing nodes is valid, and stays valid until
+     * something proves the tree it is syncing against cannot exist.
+     *
+     * @return Whether the map has not been proven impossible.
+     */
+    [[nodiscard]] bool
     isValid() const;
 
     // caution: otherMap must be accessed only by this function
@@ -421,109 +546,362 @@ public:
 
 private:
     /**
-     * A path from the root of the map down to some node, pairing each node with the ID naming its
-     * position.
+     * Whether placing `node` one level below `parentDepth` leaves it no room.
      *
-     * The two halves of an entry must agree, and the only way to get that wrong is to compute an ID
-     * from the wrong branch. So this type does not accept an ID at all: every push takes the branch
-     * being descended and derives the ID itself, so a node and its ID cannot disagree. Reads are
-     * exposed through the same accessors a std::stack would offer.
+     * Only a leaf may sit at kLeafDepth, and only a parent above kLeafDepth has
+     * a nibble left to record the branch taken. Both bounds are needed, since a
+     * leaf one level above kLeafDepth is allowed. Position is judged separately,
+     * by the walk that keeps a path.
+     *
+     * The conjunct order is load bearing: the depth is tested first, so the
+     * virtual isInner() call runs only at the one level where the bound
+     * applies.
+     *
+     * @param parentDepth the depth of the node being descended from.
+     * @param node the node about to be placed one level below it.
+     * @return whether that placement is past the deepest level this kind of
+     *         node may occupy.
+     */
+    [[nodiscard]] static bool
+    pastLeafDepth(unsigned int parentDepth, SHAMapTreeNode const& node)
+    {
+        return isLeafDepth(parentDepth + 1u) && (node.isInner() || isLeafDepth(parentDepth));
+    }
+
+    /**
+     * A root-down path of nodes through the map.
+     *
+     * Entry `i` is the node at depth `i`, since every edge spans one nibble
+     * (see the class docstring). Only the node is stored. A caller that needs a
+     * position reads a depth and takes the nibbles from its own key.
      */
     class NodePathStack
     {
     public:
+        /**
+         * @return whether the path holds no node at all.
+         */
         [[nodiscard]] bool
         empty() const
         {
-            return stack_.empty();
+            return path_.empty();
         }
 
+        /**
+         * @return how many nodes the path holds, one more than the last node's
+         *         depth.
+         */
         [[nodiscard]] std::size_t
         size() const
         {
-            return stack_.size();
+            return path_.size();
         }
 
-        [[nodiscard]] std::pair<SHAMapTreeNodePtr, SHAMapNodeID> const&
+        /**
+         * The node at the end of the path.
+         *
+         * @return a reference into the path, which a later push may invalidate
+         *         by reallocating, so a caller that pushes must ask again. An
+         *         empty path yields a null node the caller can test.
+         */
+        [[nodiscard]] SHAMapTreeNodePtr const&
         top() const
         {
-            XRPL_ASSERT(!stack_.empty(), "xrpl::SHAMap::NodePathStack::top : non-empty stack");
-            return stack_.top();
+            if (path_.empty())
+            {
+                // LCOV_EXCL_START
+                UNREACHABLE("xrpl::SHAMap::NodePathStack::top : empty stack");
+                static SHAMapTreeNodePtr const kEmpty;
+                return kEmpty;
+                // LCOV_EXCL_STOP
+            }
+            return path_.back();
         }
 
+        /**
+         * The depth of the node at the end of the path.
+         *
+         * @return the depth, which is the entry's own index. Zero on an empty
+         *         path.
+         */
+        [[nodiscard]] unsigned int
+        topDepth() const
+        {
+            if (path_.empty())
+            {
+                // LCOV_EXCL_START
+                UNREACHABLE("xrpl::SHAMap::NodePathStack::topDepth : empty stack");
+                return 0;
+                // LCOV_EXCL_STOP
+            }
+            return static_cast<unsigned int>(path_.size() - 1);
+        }
+
+        /**
+         * Shorten the path by one node. An empty path is left as it is.
+         */
         void
         pop()
         {
-            XRPL_ASSERT(!stack_.empty(), "xrpl::SHAMap::NodePathStack::pop : non-empty stack");
-            stack_.pop();
+            if (path_.empty())
+            {
+                // LCOV_EXCL_START
+                UNREACHABLE("xrpl::SHAMap::NodePathStack::pop : empty stack");
+                return;
+                // LCOV_EXCL_STOP
+            }
+            path_.pop_back();
         }
 
+        /**
+         * Discard the whole path.
+         */
         void
         clear()
         {
-            stack_ = {};
+            path_.clear();
+            pathKey_ = UInt256{};
         }
 
         /**
-         * Start a path at the root of the map, whose ID is the zero-depth ID by definition.
-         */
-        void
-        pushRoot(SHAMapTreeNodePtr node)
-        {
-            XRPL_ASSERT(stack_.empty(), "xrpl::SHAMap::NodePathStack::pushRoot : empty stack");
-            stack_.emplace(std::move(node), SHAMapNodeID{});
-        }
-
-        /**
-         * Extend the path to the child of the current node reached by `branch`.
+         * Shorten the path by one node and hand that node to the caller.
          *
-         * A node keeps the depth it was reached at, never a normalized kLeafDepth. Only a leaf may
-         * sit at kLeafDepth, since an inner node there would have no branch left to select.
-         */
-        void
-        pushChild(SHAMapTreeNodePtr node, unsigned int branch)
-        {
-            XRPL_ASSERT(node, "xrpl::SHAMap::NodePathStack::pushChild : non-null node input");
-            XRPL_ASSERT(
-                !stack_.empty(), "xrpl::SHAMap::NodePathStack::pushChild : non-empty stack");
-            auto const childID = stack_.top().second.getChildNodeID(branch);
-            XRPL_ASSERT_IF(
-                node->isInner(),
-                childID.getDepth() < kLeafDepth,
-                "xrpl::SHAMap::NodePathStack::pushChild : inner node above leaf depth");
-            XRPL_ASSERT_IF(
-                node->isLeaf(),
-                childID.isPrefixOf(leafKey(*node)),
-                "xrpl::SHAMap::NodePathStack::pushChild : leaf key below branch");
-            stack_.emplace(std::move(node), childID);
-        }
-
-        /**
-         * Extend the path to a node lying on the path to `target`.
+         * Moves the node out, transferring the existing reference.
          *
-         * For nodes not reached by descending a known branch: the walk tracks only the key it is
-         * heading for, or the node is newly created. Either way `target` selects the branch.
+         * @return the node that was at the end of the path, or an empty
+         *         pointer if there was none.
          */
-        void
-        pushNode(SHAMapTreeNodePtr node, UInt256 const& target)
+        [[nodiscard]] SHAMapTreeNodePtr
+        releaseNode()
         {
-            if (stack_.empty())
+            if (path_.empty())
             {
-                pushRoot(std::move(node));
+                // LCOV_EXCL_START
+                UNREACHABLE("xrpl::SHAMap::NodePathStack::releaseNode : empty stack");
+                return {};
+                // LCOV_EXCL_STOP
+            }
+            auto node = std::move(path_.back());
+            path_.pop_back();
+            return node;
+        }
+
+        /**
+         * Shorten the path by one node and hand it over as a `Node`.
+         *
+         * @tparam Node SHAMapInnerNode or SHAMapLeafNode.
+         * @return the node that was at the end of the path, or an empty pointer
+         *         if the path was empty or that node is not a `Node`. The path
+         *         is shortened either way.
+         */
+        template <class Node>
+        [[nodiscard]] intr_ptr::SharedPtr<Node>
+        releaseNodeAs()
+        {
+            static_assert(
+                std::is_same_v<Node, SHAMapInnerNode> || std::is_same_v<Node, SHAMapLeafNode>,
+                "releaseNodeAs serves the two concrete node kinds");
+
+            auto node = releaseNode();
+            if (!node)
+            {
+                // The other half of releaseNode()'s empty-path contract, asserted there by the
+                // UNREACHABLE in its own LCOV_EXCL block.
+                return {};  // LCOV_EXCL_LINE
+            }
+
+            if constexpr (std::is_same_v<Node, SHAMapInnerNode>)
+            {
+                // A leaf sits only at the end of a path, which both callers asking for an inner
+                // node have released first. The other half of the contract their own UNREACHABLEs
+                // assert, in SHAMap::dirtyUp and SHAMap::delItem.
+                if (!node->isInner())
+                    return {};  // LCOV_EXCL_LINE
             }
             else
             {
-                pushChild(std::move(node), selectBranch(stack_.top().second, target));
+                if (!node->isLeaf())
+                    return {};
             }
+
+            return intr_ptr::staticPointerCast<Node>(std::move(node));
+        }
+
+        /**
+         * Start a path at the root of the map, which sits at depth zero by
+         * definition.
+         *
+         * @return false, leaving the path unchanged, if a path was already
+         *         started.
+         */
+        [[nodiscard]] bool
+        pushRoot(SHAMapTreeNodePtr node)
+        {
+            if (!path_.empty())
+            {
+                // LCOV_EXCL_START
+                UNREACHABLE("xrpl::SHAMap::NodePathStack::pushRoot : non-empty stack");
+                return false;
+                // LCOV_EXCL_STOP
+            }
+            // Reserved here rather than in the constructor, to keep SHAMap::end()
+            // allocation-free. A path holds at most kLeafDepth + 1 entries, so no push on a path
+            // started here reallocates. A copy is not given that room, so top()'s invalidation
+            // rule still holds.
+            path_.reserve(kLeafDepth + 1u);
+            path_.push_back(std::move(node));
+            return true;
+        }
+
+        /**
+         * Extend the path to the child of the node at its end reached by
+         * `branch`.
+         *
+         * Only a leaf may sit at kLeafDepth, since an inner node there would
+         * have no branch left to select.
+         *
+         * @param node the child to append.
+         * @param branch the branch of the current node that `node` was reached
+         *               through, which serves to judge the node offered.
+         * @return false if there is no node to descend from or to push, no
+         *         branch of that number, no room left below for the kind of
+         *         node offered, or a leaf whose own key does not select
+         *         `branch`. The path keeps its nodes.
+         */
+        [[nodiscard]] bool
+        pushChild(SHAMapTreeNodePtr node, unsigned int branch)
+        {
+            if (path_.empty() || !node || branch >= kBranchFactor)
+            {
+                // LCOV_EXCL_START
+                UNREACHABLE("xrpl::SHAMap::NodePathStack::pushChild : no child to push");
+                return false;
+                // LCOV_EXCL_STOP
+            }
+
+            // A node must have room below it at the depth it is offered for. Reachable, since a
+            // node resolved by hash carries no position of its own.
+            auto const parentDepth = topDepth();
+            bool const tooDeep = pastLeafDepth(parentDepth, *node);
+            SOMETIMES(tooDeep, "xrpl::SHAMap::NodePathStack::pushChild : child past leaf depth");
+            if (tooDeep)
+            {
+                return false;
+            }
+
+            // A leaf's key must agree with every branch recorded above it, which the chain in
+            // `pathKey_` supplies. A path's length gives only the depths.
+            pathKey_ = childNodeID(pathKey_, parentDepth, branch);
+
+            // The test takes the depth and the two keys, so no SHAMapNodeID is built: it
+            // is a CountedObject, and one per push would report as a live node ID.
+            bool const misplaced =
+                node->isLeaf() && !samePositionAtDepth(parentDepth + 1u, pathKey_, leafKey(*node));
+            SOMETIMES(
+                misplaced, "xrpl::SHAMap::NodePathStack::pushChild : leaf key outside branch");
+            if (misplaced)
+            {
+                return false;
+            }
+
+            path_.push_back(std::move(node));
+            return true;
+        }
+
+        /**
+         * Extend the path by one node lying on the way to `target`, starting
+         * it if it is empty.
+         *
+         * For nodes not reached by descending a known branch: the walk tracks
+         * only the key it is heading for, or the node is newly created. Either
+         * way `target` names the branch.
+         *
+         * @param node the node to append.
+         * @param target the key the walk is heading for.
+         * @return whatever pushRoot or pushChild returned.
+         */
+        [[nodiscard]] bool
+        pushNode(SHAMapTreeNodePtr node, UInt256 const& target)
+        {
+            if (path_.empty())
+            {
+                return pushRoot(std::move(node));
+            }
+            return pushChild(std::move(node), selectBranch(topDepth(), target));
         }
 
     private:
-        std::stack<std::pair<SHAMapTreeNodePtr, SHAMapNodeID>> stack_;
+        // path_[i] holds the node at depth i, by construction: pushRoot starts at depth 0 and
+        // pushChild only ever appends one level.
+        std::vector<SHAMapTreeNodePtr> path_;
+
+        // The branches descended, one nibble per level: nibble i is the branch taken from depth i.
+        // Nibbles below the path's end are stale after a pop, so every read masks at the path's
+        // own depth. childNodeID clears a nibble before writing it, so re-descending overwrites.
+        UInt256 pathKey_;
     };
 
     using DeltaRef =
         std::pair<boost::intrusive_ptr<SHAMapItem const>, boost::intrusive_ptr<SHAMapItem const>>;
 
+    /**
+     * The sequence of the ledger this map references, read atomically.
+     *
+     * @return The sequence, or zero if the map references no ledger.
+     */
+    [[nodiscard]] std::uint32_t
+    ledgerSeq() const;
+
+    /**
+     * The current state, read atomically.
+     *
+     * Orders state_ alone. The tree's nodes carry no ordering guarantees.
+     *
+     * @return The state as of the call, which a concurrent walk may already
+     *         have moved past.
+     */
+    [[nodiscard]] SHAMapState
+    state() const;
+
+    /**
+     * Record that the map is provably not the one it claims to be.
+     *
+     * Cannot fail, since Invalid outranks every other state. Const because a
+     * const descend() can reach this verdict while resolving a node.
+     */
+    void
+    setInvalid() const;
+
+    /**
+     * Condemn the map, naming in the log the node whose position proves it.
+     *
+     * Const, because a read path can reach this verdict. See setInvalid().
+     *
+     * @param node the node that cannot sit where it was offered.
+     * @param hash the hash it was resolved under.
+     * @param position the place in the tree it was offered for.
+     */
+    void
+    condemn(SHAMapTreeNode const& node, SHAMapHash const& hash, SHAMapNodeID const& position) const;
+
+    /**
+     * Move the map to a new state, atomically.
+     *
+     * With clearSynching(), the only writer of state_ past construction.
+     * Invalid is always stored, and every other transition is refused once
+     * the map is Invalid, which is what makes that verdict terminal.
+     * clearSynching() is narrower and moves only Synching.
+     *
+     * Const to let setInvalid() be const. state_ is mutable, which makes that
+     * legal.
+     *
+     * @param desired The state to move to.
+     * @return false if the map is Invalid and the requested state is not,
+     *         leaving it unchanged. True otherwise.
+     */
+    bool
+    trySetState(SHAMapState desired) const;
+
     // tree node cache operations
     SHAMapTreeNodePtr
     cacheLookup(SHAMapHash const& hash) const;
@@ -550,9 +928,13 @@ private:
     dirtyUp(NodePathStack& stack, UInt256 const& target, SHAMapTreeNodePtr terminal);
 
     /**
-     * Walk towards the specified id, returning the node.  Caller must check
-     *  if the return is nullptr, and if not, if the node->peekItem()->key() ==
-     * id
+     * Walk towards the specified id, returning the node.
+     *
+     * @param id the key to walk towards, which need not be in the map.
+     * @param stack records the path walked, or nullptr to skip recording it.
+     * @return the leaf the walk ended on, or nullptr if it ended on an inner
+     *         node or was refused. A returned leaf need not hold `id`, so
+     *         callers compare its key themselves.
      */
     SHAMapLeafNode*
     walkTowardsKey(UInt256 const& id, NodePathStack* stack = nullptr) const;
@@ -564,10 +946,16 @@ private:
 
     /**
      * Unshare the node, allowing it to be modified
+     *
+     * @param node the node to unshare.
+     * @param depth the depth the node sits at, which says whether it is the
+     *        root. A clone of the root has to be adopted as the new root. A
+     *        clone of any other node is hooked up by the caller.
+     * @return the node, cloned if it was shared.
      */
     template <class Node>
-    intr_ptr::SharedPtr<Node>
-    unshareNode(intr_ptr::SharedPtr<Node>, SHAMapNodeID const& nodeID);
+    [[nodiscard]] intr_ptr::SharedPtr<Node>
+    unshareNode(intr_ptr::SharedPtr<Node> node, unsigned int depth);
 
     /**
      * prepare a node to be modified before flushing
@@ -588,8 +976,13 @@ private:
     /**
      * Returns the first or last item at or below the node already on top of `stack`, extending
      * `stack` with the path walked to reach it.
+     *
+     * @param stack the path to extend, whose last node the search starts from.
+     * @param direction whether to take the lowest or the highest branch at
+     *                  each level.
+     * @return the leaf found, or nullptr if no leaf lies below that node.
      */
-    SHAMapLeafNode*
+    [[nodiscard]] SHAMapLeafNode*
     belowHelper(NodePathStack& stack, BelowDirection direction) const;
 
     /**
@@ -603,7 +996,7 @@ private:
      * @param direction First to search upwards from `id`, Last to search downwards.
      * @return An iterator to the item found, or end() if no item lies on that side of `id`.
      */
-    ConstIterator
+    [[nodiscard]] ConstIterator
     boundHelper(UInt256 const& id, BelowDirection direction) const;
 
     // Simple descent
@@ -628,6 +1021,22 @@ private:
         bool& pending,
         DescendCallback&&) const;
 
+    /**
+     * Resolve the child of `parent` on `branch`, judging where it lands.
+     *
+     * Const, yet it records the Invalid verdict through setInvalid(). A new
+     * caller must therefore be a path that may reach that verdict. Today
+     * addKnownNode() is the only one.
+     *
+     * @param parent the inner node to descend from.
+     * @param parentID the position of `parent`.
+     * @param branch the branch of `parent` to resolve, which the caller has
+     *               already bounded.
+     * @param filter an alternate source of nodes, or null for the store alone.
+     * @return the child and the child's position. A null child where the branch
+     *         could not be resolved, or where what came back does not belong at
+     *         that position, in which case the map is left Invalid.
+     */
     std::pair<SHAMapTreeNode*, SHAMapNodeID>
     descend(
         SHAMapInnerNode* parent,
@@ -728,10 +1137,29 @@ private:
     };
 
     // getMissingNodes helper functions
+
+    /**
+     * Examine the remaining branches of one inner node, recording or
+     * requesting what is missing.
+     *
+     * @param mn the walk's shared state, which collects the missing nodes.
+     * @param node the walk's current position, updated to the node to process
+     *             next.
+     */
     void
-    gmnProcessNodes(MissingNodes&, MissingNodes::StackEntry& node);
-    static void
-    gmnProcessDeferredReads(MissingNodes&);
+    gmnProcessNodes(MissingNodes& mn, MissingNodes::StackEntry& node);
+
+    /**
+     * Wait for every read this pass posted, then hook up or record what each
+     * one resolved.
+     *
+     * Drains all of them even after judging the map, since an outstanding read
+     * holds a pointer to `mn`.
+     *
+     * @param mn the walk's shared state, holding the posted reads.
+     */
+    void
+    gmnProcessDeferredReads(MissingNodes& mn);
 
     // fetch from DB helper function
     SHAMapTreeNodePtr
@@ -739,46 +1167,119 @@ private:
 };
 
 inline void
-SHAMap::setFull()
+SHAMap::setFull(std::uint32_t ledgerSeq)
 {
-    full_ = true;
+    ledgerSeq_.store(ledgerSeq, std::memory_order_relaxed);
+    full_.store(true, std::memory_order_release);
 }
 
 inline void
 SHAMap::setLedgerSeq(std::uint32_t lseq)
 {
-    ledgerSeq_ = lseq;
+    ledgerSeq_.store(lseq, std::memory_order_relaxed);
 }
 
-inline void
+inline std::uint32_t
+SHAMap::ledgerSeq() const
+{
+    return ledgerSeq_.load(std::memory_order_relaxed);
+}
+
+inline SHAMapState
+SHAMap::state() const
+{
+    return state_.load(std::memory_order_acquire);
+}
+
+inline bool
+SHAMap::trySetState(SHAMapState desired) const
+{
+    // Invalid is stored outright: that verdict outranks a concurrent transition.
+    if (desired == SHAMapState::Invalid)
+    {
+        state_.store(SHAMapState::Invalid, std::memory_order_release);
+        return true;
+    }
+
+    // A failed exchange both reports the state and refreshes expected, so no load is needed
+    // ahead of the loop.
+    auto expected = SHAMapState::Modifying;
+    while (expected != SHAMapState::Invalid)
+    {
+        if (state_.compare_exchange_weak(
+                expected, desired, std::memory_order_acq_rel, std::memory_order_acquire))
+        {
+            return true;
+        }
+    }
+    return false;
+}
+
+inline bool
 SHAMap::setImmutable()
 {
-    XRPL_ASSERT(state_ != SHAMapState::Invalid, "xrpl::SHAMap::setImmutable : state is valid");
-    state_ = SHAMapState::Immutable;
+    SOMETIMES(!isValid(), "xrpl::SHAMap::setImmutable : map is invalid");
+    return trySetState(SHAMapState::Immutable);
 }
 
 inline bool
 SHAMap::isSynching() const
 {
-    return state_ == SHAMapState::Synching;
+    return state() == SHAMapState::Synching;
+}
+
+inline bool
+SHAMap::isImmutable() const
+{
+    return state() == SHAMapState::Immutable;
 }
 
 inline void
 SHAMap::setSynching()
 {
-    state_ = SHAMapState::Synching;
+    // Guarded, so this is not a way out of Invalid.
+    if (!trySetState(SHAMapState::Synching))
+    {
+        // Only ever called on a freshly constructed map.
+        // LCOV_EXCL_START
+        UNREACHABLE("xrpl::SHAMap::setSynching : map is invalid");
+        // LCOV_EXCL_STOP
+    }
 }
 
 inline void
 SHAMap::clearSynching()
 {
-    state_ = SHAMapState::Modifying;
+    // Only Synching moves. A walk can end after the ledger settled, and then the map stays
+    // Immutable; a Modifying map has nothing to clear; an invalid map stays invalid. Only that
+    // last refusal is logged, since a concurrent walk is what produces it.
+    auto expected = SHAMapState::Synching;
+    if (state_.compare_exchange_strong(
+            expected, SHAMapState::Modifying, std::memory_order_acq_rel, std::memory_order_acquire))
+    {
+        return;
+    }
+
+    bool const invalid = expected == SHAMapState::Invalid;
+    SOMETIMES(invalid, "xrpl::SHAMap::clearSynching : map is invalid");
+    if (invalid)
+    {
+        JLOG(journal_.warn()) << "Refused to clear synching on an invalid map, root hash "
+                              << root_->getHash();
+    }
 }
 
 inline bool
 SHAMap::isValid() const
 {
-    return state_ != SHAMapState::Invalid;
+    return state() != SHAMapState::Invalid;
+}
+
+inline void
+SHAMap::setInvalid() const
+{
+    // Through trySetState() like every other transition, so state_ has one writer funnel.
+    trySetState(SHAMapState::Invalid);
 }
 
 inline void

include/xrpl/shamap/SHAMapAddNode.h

@@ -12,6 +12,10 @@ private:
     int bad_;
     int duplicate_;
 
+    // Whether a node in the batch proved the map impossible. A fact about the batch rather than
+    // about the map, so a caller can tell this batch's doing from a concurrent walk's verdict.
+    bool invalidatedMap_;
+
 public:
     SHAMapAddNode();
 
@@ -96,6 +100,26 @@ public:
     static SHAMapAddNode
     invalid();
 
+    /**
+     * @return A verdict recording one invalid node that proved the map
+     *         impossible.
+     */
+    static SHAMapAddNode
+    mapInvalidated();
+
+    /**
+     * Whether a node in the batch proved the map impossible.
+     *
+     * Reports what the batch did rather than what the map now holds, so a
+     * verdict another thread's walk reached is not read as this batch's. The
+     * two differ: SHAMap::setInvalid() is written with no lock held, by a
+     * getMissingNodes() walk its caller runs lock-free.
+     *
+     * @return Whether a node in the batch invalidated the map.
+     */
+    [[nodiscard]] bool
+    invalidatedMap() const;
+
     /**
      * Clear every count back to zero.
      */
@@ -121,15 +145,15 @@ public:
     operator+=(SHAMapAddNode const& n);
 
 private:
-    SHAMapAddNode(int good, int bad, int duplicate);
+    SHAMapAddNode(int good, int bad, int duplicate, bool invalidatedMap = false);
 };
 
-inline SHAMapAddNode::SHAMapAddNode() : good_(0), bad_(0), duplicate_(0)
+inline SHAMapAddNode::SHAMapAddNode() : good_(0), bad_(0), duplicate_(0), invalidatedMap_(false)
 {
 }
 
-inline SHAMapAddNode::SHAMapAddNode(int good, int bad, int duplicate)
-    : good_(good), bad_(bad), duplicate_(duplicate)
+inline SHAMapAddNode::SHAMapAddNode(int good, int bad, int duplicate, bool invalidatedMap)
+    : good_(good), bad_(bad), duplicate_(duplicate), invalidatedMap_(invalidatedMap)
 {
 }
 
@@ -187,6 +211,12 @@ SHAMapAddNode::isUseful() const
     return good_ > 0;
 }
 
+inline bool
+SHAMapAddNode::invalidatedMap() const
+{
+    return invalidatedMap_;
+}
+
 inline SHAMapAddNode
 SHAMapAddNode::duplicate()
 {
@@ -205,10 +235,17 @@ SHAMapAddNode::invalid()
     return SHAMapAddNode(0, 1, 0);
 }
 
+inline SHAMapAddNode
+SHAMapAddNode::mapInvalidated()
+{
+    return SHAMapAddNode(0, 1, 0, true);
+}
+
 inline void
 SHAMapAddNode::reset()
 {
     good_ = bad_ = duplicate_ = 0;
+    invalidatedMap_ = false;
 }
 
 inline std::string
@@ -246,6 +283,9 @@ SHAMapAddNode::operator+=(SHAMapAddNode const& n)
     bad_ += n.bad_;
     duplicate_ += n.duplicate_;
 
+    // Or-ed, not summed: one node in the batch having proved the map impossible is the whole fact.
+    invalidatedMap_ = invalidatedMap_ || n.invalidatedMap_;
+
     return *this;
 }
 

include/xrpl/shamap/SHAMapInnerNode.h

@@ -19,7 +19,8 @@ class SHAMapInnerNode final : public SHAMapTreeNode, public CountedObject<SHAMap
 {
 public:
     /**
-     * Each inner node has 16 children (the 'radix tree' part of the map)
+     * Children per inner node: one branch per value of the key nibble that a
+     * node's depth selects.
      */
     static constexpr unsigned int kBranchFactor = 16;
 
@@ -31,7 +32,25 @@ private:
      */
     TaggedPointer hashesAndChildren_;
 
-    std::uint32_t fullBelowGen_ = 0;
+    // Pin that wrapping fullBelowGen_ in an atomic keeps the packed layout, and that the load
+    // isFullBelow() does once per node of every walk stays lock-free.
+    static_assert(std::atomic<std::uint32_t>::is_always_lock_free);
+    static_assert(sizeof(std::atomic<std::uint32_t>) == sizeof(std::uint32_t));
+    static_assert(alignof(std::atomic<std::uint32_t>) == alignof(std::uint32_t));
+
+    /**
+     * The generation in which a walk found every node below this one resident,
+     * with this node as the walk's root. The node object is shared by hash
+     * between maps and positions, and a hash commits to a node's contents
+     * rather than its place, so the flag is written and read for the root
+     * position only; below the root, the position-keyed FullBelowCache is the
+     * memo. Written from more than one thread, since canonicalization shares a
+     * node between maps and a walk can run with the acquisition lock released
+     * (see SHAMap::state_). Relaxed both ways, since a generation is only
+     * compared for equality and the children it vouches for are published
+     * through lock_.
+     */
+    std::atomic<std::uint32_t> fullBelowGen_ = 0;
     std::uint16_t isBranch_ = 0;
 
     /**
@@ -148,10 +167,23 @@ public:
     SHAMapTreeNodePtr
     canonicalizeChild(unsigned int branch, SHAMapTreeNodePtr node);
 
-    // sync functions
+    /**
+     * Whether a walk rooted at this node found every node below it resident.
+     *
+     * Meaningful only for the node a walk starts at; see fullBelowGen_.
+     *
+     * @param generation The FullBelowCache generation the asking walk runs in.
+     * @return True if a walk rooted here completed in that generation.
+     */
     bool
     isFullBelow(std::uint32_t generation) const;
 
+    /**
+     * Record that a walk rooted at this node found every node below it
+     * resident.
+     *
+     * @param gen The FullBelowCache generation the completing walk ran in.
+     */
     void
     setFullBelowGen(std::uint32_t gen);
 
@@ -204,13 +236,13 @@ SHAMapInnerNode::getBranchCount() const
 inline bool
 SHAMapInnerNode::isFullBelow(std::uint32_t generation) const
 {
-    return fullBelowGen_ == generation;
+    return fullBelowGen_.load(std::memory_order_relaxed) == generation;
 }
 
 inline void
 SHAMapInnerNode::setFullBelowGen(std::uint32_t gen)
 {
-    fullBelowGen_ = gen;
+    fullBelowGen_.store(gen, std::memory_order_relaxed);
 }
 
 }  // namespace xrpl

include/xrpl/shamap/SHAMapLeafNode.h

@@ -75,4 +75,41 @@ leafKey(SHAMapTreeNode const& node)
     return safeDowncast<SHAMapLeafNode const&>(node).peekItem()->key();
 }
 
+/**
+ * Whether a node may occupy a position in a SHAMap.
+ *
+ * A leaf's own key names its position. An inner node carries no key, so every
+ * position agrees with it and a caller's own depth rules are what bound it.
+ *
+ * @param nodeID the position the node is claimed to occupy.
+ * @param node the node to judge.
+ * @return whether the node's own key agrees with that position.
+ */
+[[nodiscard]] inline bool
+belongsAt(SHAMapNodeID const& nodeID, SHAMapTreeNode const& node)
+{
+    return !node.isLeaf() || nodeID.isPrefixOf(leafKey(node));
+}
+
+/**
+ * Whether a node may occupy the child position a branch leads to.
+ *
+ * The overload above, asked about a child without building the child's id.
+ *
+ * @param parentID the position of the node above, whose depth must be below
+ *                 SHAMap::kLeafDepth.
+ * @param branch the branch of that node leading to the position judged.
+ * @param node the node to judge.
+ * @return whether the node's own key agrees with that position.
+ */
+[[nodiscard]] inline bool
+belongsAt(SHAMapNodeID const& parentID, unsigned int branch, SHAMapTreeNode const& node)
+{
+    if (!node.isLeaf())
+        return true;
+
+    auto const& key = leafKey(node);
+    return parentID.isPrefixOf(key) && selectBranch(parentID, key) == branch;
+}
+
 }  // namespace xrpl

include/xrpl/shamap/SHAMapNodeID.h

@@ -123,6 +123,38 @@ operator<<(std::ostream& out, SHAMapNodeID const& node)
     return out << to_string(node);
 }
 
+/**
+ * Returns the id of the child a parent's branch leads to
+ *
+ * A child's id is its parent's with the nibble at the parent's own depth set to
+ * the branch taken. Every other nibble is copied through, so a masked parent
+ * gives a masked child. The write counterpart of selectBranch.
+ *
+ * @param parentID the id of the parent. The nibble at parentDepth is
+ *                 overwritten rather than merged, so an id already carrying one
+ *                 there is accepted.
+ * @param parentDepth the depth of the parent, below SHAMap::kLeafDepth.
+ * @param branch the branch of the parent leading to the child.
+ * @return that child's id, whose depth is parentDepth + 1.
+ */
+[[nodiscard]] UInt256
+childNodeID(UInt256 const& parentID, unsigned int parentDepth, unsigned int branch);
+
+/**
+ * Whether two keys name the same position at a given depth
+ *
+ * Both sides are masked, so either may carry bits below `depth`.
+ * SHAMapNodeID::isPrefixOf is the stricter form.
+ *
+ * @param depth how many leading nibbles name the position, at most
+ *              SHAMap::kLeafDepth. A greater depth is clamped to it.
+ * @param lhs one of the keys.
+ * @param rhs the other key.
+ * @return whether the two agree on those nibbles.
+ */
+[[nodiscard]] bool
+samePositionAtDepth(unsigned int depth, UInt256 const& lhs, UInt256 const& rhs);
+
 /**
  * Return an object representing a serialized SHAMap Node ID
  *
@@ -144,9 +176,26 @@ deserializeSHAMapNodeID(std::string_view s)
 /** @} */
 
 /**
- * Returns the branch that would contain the given hash
+ * Returns the branch at the given depth that would contain the given hash
+ *
+ * @param depth the depth of the node whose branch to select.
+ * @param hash the key whose nibble at that depth names the branch.
+ * @return the branch containing the hash.
  */
 [[nodiscard]] unsigned int
-selectBranch(SHAMapNodeID const& id, UInt256 const& hash);
+selectBranch(unsigned int depth, UInt256 const& hash);
+
+/**
+ * Returns the branch that would contain the given hash
+ *
+ * @param id the node whose depth to read.
+ * @param hash the key whose nibble at that depth names the branch.
+ * @return the branch containing the hash.
+ */
+[[nodiscard]] inline unsigned int
+selectBranch(SHAMapNodeID const& id, UInt256 const& hash)
+{
+    return selectBranch(id.getDepth(), hash);
+}
 
 }  // namespace xrpl

include/xrpl/tx/Transactor.h

@@ -375,6 +375,22 @@ public:
     /////////////////////////////////////////////////////
 
     // Interface used by AccountDelete
+    /**
+     * This method removes one Ticket ledger-object from the ledger. AccountDelete uses it to
+     * clean up Ticket objects en masse.
+     *
+     * This method reduces the TicketCount and the OwnerCount of the Owner AccountRoot object. If
+     * a TransactionProposal reserved this Ticket, that proposal is deleted as well: once the
+     * Ticket is gone, its proposed transaction can never be applied (tefNO_TICKET).
+     *
+     * @param view         the apply view for making changes.
+     * @param account      the account which owns the Ticket object.
+     * @param ticketIndex  ticketIndex is used to construct the ledger-entry ID of Ticket object.
+     * @param j            the journal reference used to log messages.
+     *
+     * @return the final TER after all invariant checks. `tefBAD_LEDGER` is returned if Ticket,
+     * Owner AccountRoot is not found in the apply-view ledger.
+     */
     static TER
     ticketDelete(
         ApplyView& view,

include/xrpl/tx/invariants/InvariantCheck.h

@@ -1,7 +1,9 @@
 #pragma once
 
+#include <xrpl/basics/base_uint.h>
 #include <xrpl/beast/utility/Journal.h>
 #include <xrpl/ledger/ReadView.h>
+#include <xrpl/protocol/AccountID.h>
 #include <xrpl/protocol/STLedgerEntry.h>
 #include <xrpl/protocol/STTx.h>
 #include <xrpl/protocol/TER.h>
@@ -21,6 +23,7 @@
 #include <boost/multiprecision/cpp_int.hpp>
 
 #include <cstdint>
+#include <map>
 #include <set>
 #include <string>
 #include <tuple>
@@ -363,11 +366,27 @@ public:
  * unique to pseudo-accounts. Check that all pseudo-accounts are following the
  * rules, and that only pseudo-accounts look like pseudo-accounts.
  *
+ * Post-fixCleanup3_5_0, a pseudo-account also owns only entries that belong
+ * to its own AMM, Vault or LoanBroker:
+ * - AMM: its AMM entry, its holdings of the two pool assets, and the trust
+ *   lines of its LP token,
+ * - Vault: its share MPTokenIssuance, its holding of the vault asset, and the
+ *   LoanBrokers operating on this vault,
+ * - LoanBroker: its Loans and its holding of the vault asset (the cover).
+ *
+ * A pseudo-account cannot sign transactions, so it could never accept or
+ * remove any other object linked into its owner directory. Such an object
+ * would pin the directory and block deletion of the owning object.
  */
 class ValidPseudoAccounts
 {
     std::vector<std::string> errors_;
 
+    // Entries newly linked into owner directories, keyed by the directory
+    // owner. Whether an owner is a pseudo-account is decided in finalize,
+    // where the view is available.
+    std::map<AccountID, std::vector<uint256>> ownerDirAdditions_;
+
 public:
     void
     visitEntry(bool, SLE::ConstRef, SLE::ConstRef);

include/xrpl/tx/invariants/VaultInvariant.h

@@ -8,6 +8,7 @@
 #include <xrpl/protocol/AccountID.h>
 #include <xrpl/protocol/Asset.h>
 #include <xrpl/protocol/MPTIssue.h>
+#include <xrpl/protocol/Protocol.h>
 #include <xrpl/protocol/Rules.h>
 #include <xrpl/protocol/STLedgerEntry.h>
 #include <xrpl/protocol/STTx.h>
@@ -29,7 +30,7 @@ namespace xrpl {
  * - vault must have MPTokenIssuance for shares
  * - vault without shares outstanding must have no shares
  * - loss unrealized does not exceed the difference between assets total and
- *   assets available
+ *   assets available (Legacy/CashBasis), or AssetsDeployed (FixedPrecision)
  * - assets available do not exceed assets total
  * - vault deposit increases assets and share issuance, and adds to:
  *   total assets, assets available, shares outstanding
@@ -46,6 +47,14 @@ namespace xrpl {
  * - vault withdrawal may not succeed when the vault phase is Investment
  * - closed-ended loan origination (ttLOAN_SET) may only succeed when the
  *   vault phase is Investment
+ * - FixedPrecision only: AssetsDeployed is non-negative and exactly
+ *   representable at the asset's precision; AssetsDeployed changes only for
+ *   ttLOAN_SET, ttLOAN_PAY and ttLOAN_MANAGE; AssetsDeployed is zero right
+ *   after ttVAULT_CREATE and whenever shares outstanding return to zero; the
+ *   stored AssetsTotal cache equals AssetsAvailable + AssetsDeployed, rounded
+ *   Downward to the asset's precision
+ * - FixedPrecision only: YieldUnrealized is non-negative; YieldUnrealized
+ *   changes only for ttLOAN_SET, ttLOAN_PAY and ttLOAN_MANAGE
  *
  * Immutability of VaultKind, SubscriptionDate and RedemptionDate is enforced
  * by NoModifiedUnmodifiableFields (see InvariantCheck.cpp). From
@@ -68,6 +77,9 @@ class ValidVault
         Number assetsAvailable = 0;
         Number assetsMaximum = 0;
         Number lossUnrealized = 0;
+        Number assetsDeployed = 0;
+        Number yieldUnrealized = 0;
+        VaultVersion version = VaultVersion::Legacy;
         std::optional<std::uint8_t> vaultKind;
         std::optional<std::uint32_t> subscriptionDate;
         std::optional<std::uint32_t> redemptionDate;
@@ -217,6 +229,39 @@ private:
     [[nodiscard]] bool
     finalizeLoanSet(ReadView const& view, beast::Journal const& j) const;
 
+    /**
+     * @brief Check that a vault's AssetsTotal and AssetsAvailable deltas add
+     *        up against the real transfer, for deposit/withdraw/clawback.
+     *
+     * Shared body of the ttVAULT_DEPOSIT, ttVAULT_WITHDRAW and
+     * ttVAULT_CLAWBACK "assets outstanding"/"assets available" add-up checks,
+     * which differ only in the rounded/exact deltas plugged in and the verb
+     * used in the log message.
+     *
+     * @param afterVault Snapshot of the vault after the transaction.
+     * @param beforeVault Snapshot of the vault before the transaction.
+     * @param vaultAsset The vault's underlying asset.
+     * @param fix340Enabled Whether fixCleanup3_4_0 is enabled.
+     * @param minScale The posterior scale computed by computeVaultMinScale.
+     * @param roundedVaultDelta The real transfer's delta, rounded to minScale.
+     * @param exactVaultDelta The real transfer's exact (unrounded) delta.
+     * @param verb The transaction name used in the log message ("deposit",
+     *             "withdrawal" or "clawback").
+     * @param j Journal for logging.
+     * @return false if either add-up check fails.
+     */
+    [[nodiscard]] static bool
+    checkTotalsAddUp(
+        Vault const& afterVault,
+        Vault const& beforeVault,
+        Asset const& vaultAsset,
+        bool fix340Enabled,
+        std::int32_t minScale,
+        Number const& roundedVaultDelta,
+        Number const& exactVaultDelta,
+        char const* verb,
+        beast::Journal const& j);
+
 public:
     // Compute the coarsest scale required to represent all numbers
     [[nodiscard]] static std::int32_t

include/xrpl/tx/transactors/lending/LoanManage.h

@@ -5,6 +5,7 @@
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/ReadView.h>
 #include <xrpl/protocol/Asset.h>
+#include <xrpl/protocol/STAmount.h>
 #include <xrpl/protocol/STTx.h>
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/XRPAmount.h>
@@ -45,9 +46,29 @@ public:
         SLE::Ref loanSle,
         SLE::Ref brokerSle,
         SLE::Ref vaultSle,
-        Asset const& vaultAsset,
         beast::Journal j);
 
+    /**
+     * @brief Compute the First-Loss Capital cover amount for a defaulted Loan on a FixedPrecision
+     * Vault, capped at the LoanBroker's CoverAvailable and floored so that AssetsAvailable + cover
+     * is exactly on its posterior grid.
+     *
+     * The LoanBroker absorbs the rounding. When CoverAvailable - cover needs finer digits than the
+     * broker's posterior grid, it rounds to nearest, as the broker's trust line does, so
+     * CoverAvailable can move by up to half a posterior ulp more or less than the cover. When the
+     * two grids differ, no cover is exact on both sides; the Vault side is kept exact.
+     *
+     * The one exception: when AssetsAvailable has digits finer than the 16-digit cover can carry,
+     * no cover cancels them, and the balance writer rounds AssetsAvailable + cover to nearest,
+     * by at most half a posterior ulp. VaultDeposit and LoanPay credits have the same limit.
+     * @param loanSle The Loan being defaulted.
+     * @param brokerSle The Loan's LoanBroker.
+     * @param vaultSle The LoanBroker's Vault.
+     * @return The cover amount, in the Vault's Asset.
+     */
+    static STAmount
+    calculateDefaultCover(SLE::Ref loanSle, SLE::Ref brokerSle, SLE::Ref vaultSle);
+
     /**
      * Helper function that might be needed by other transactors
      */

include/xrpl/tx/transactors/proposal/TransactionProposalCancel.h

@@ -0,0 +1,44 @@
+#pragma once
+
+#include <xrpl/beast/utility/Journal.h>
+#include <xrpl/ledger/ReadView.h>
+#include <xrpl/protocol/STLedgerEntry.h>
+#include <xrpl/protocol/STTx.h>
+#include <xrpl/protocol/TER.h>
+#include <xrpl/protocol/XRPAmount.h>
+#include <xrpl/tx/ApplyContext.h>
+#include <xrpl/tx/Transactor.h>
+
+namespace xrpl {
+
+class TransactionProposalCancel : public Transactor
+{
+public:
+    static constexpr auto kConsequencesFactory = ConsequencesFactoryType::Normal;
+
+    explicit TransactionProposalCancel(ApplyContext& ctx) : Transactor(ctx)
+    {
+    }
+
+    static NotTEC
+    preflight(PreflightContext const& ctx);
+
+    static TER
+    preclaim(PreclaimContext const& ctx);
+
+    TER
+    doApply() override;
+
+    void
+    visitInvariantEntry(bool isDelete, SLE::ConstRef before, SLE::ConstRef after) override;
+
+    [[nodiscard]] bool
+    finalizeInvariants(
+        STTx const& tx,
+        TER result,
+        XRPAmount fee,
+        ReadView const& view,
+        beast::Journal const& j) override;
+};
+
+}  // namespace xrpl

include/xrpl/tx/transactors/system/Change.h

@@ -52,6 +52,13 @@ private:
     TER
     applyFee();
 
+    /**
+     * Write the default Feature Extension fee settings into FeeSettings on
+     * `featureSmartEscrow` activation.
+     */
+    void
+    initializeVMFees();
+
     TER
     applyUNLModify();
 };

src/libxrpl/ledger/Ledger.cpp

@@ -200,11 +200,23 @@ Ledger::Ledger(
                 sle->at(sfReserveIncrement) = *f;
             sle->at(sfReferenceFeeUnits) = kFeeUnitsDeprecated;
         }
+        if (std::ranges::find(amendments, featureSmartEscrow) != amendments.end())
+        {
+            sle->at(sfGasLimit) = fees.gasLimit;
+            sle->at(sfBytecodeSizeLimit) = fees.bytecodeSizeLimit;
+            sle->at(sfGasPrice) = fees.gasPrice;
+        }
         rawInsert(sle);
     }
 
     stateMap_.flushDirty(NodeObjectType::AccountNode);
-    setImmutable();
+    // Built locally. See Ledger::setImmutable().
+    if (!setImmutable())
+    {
+        // LCOV_EXCL_START
+        logicError("Ledger::Ledger(CreateGenesisT, ...): genesis ledger map is invalid");
+        // LCOV_EXCL_STOP
+    }
 }
 
 Ledger::Ledger(
@@ -215,7 +227,7 @@ Ledger::Ledger(
     Fees const& fees,
     Family& family,
     beast::Journal j)
-    : immutable_(true)
+    : immutable_(false)
     , txMap_(SHAMapType::TRANSACTION, info.txHash, family)
     , stateMap_(SHAMapType::STATE, info.accountHash, family)
     , fees_(fees)
@@ -238,8 +250,20 @@ Ledger::Ledger(
         JLOG(j.warn()) << "Don't have state data root for ledger" << header_.seq;
     }
 
-    txMap_.setImmutable();
-    stateMap_.setImmutable();
+    // Loaded locally. See Ledger::setImmutable().
+    if (setMapsImmutable())
+    {
+        immutable_ = true;
+    }
+    else
+    {
+        // LCOV_EXCL_START
+        JLOG(j.error()) << "Invalid map for ledger " << header_.seq;
+        UNREACHABLE("xrpl::Ledger::Ledger(LedgerHeader const&, ...) : map is invalid");
+        // Treat it as a damaged ledger: the code below recomputes the hash and re-acquires.
+        loaded = false;
+        // LCOV_EXCL_STOP
+    }
 
     if (!setup())
         loaded = false;
@@ -281,7 +305,8 @@ Ledger::Ledger(Ledger const& prevLedger, NetClock::time_point closeTime)
 }
 
 Ledger::Ledger(LedgerHeader const& info, Rules rules, Family& family)
-    : immutable_(true)
+    : immutable_(false)
+    , mapHashesFromHeader_(true)
     , txMap_(SHAMapType::TRANSACTION, info.txHash, family)
     , stateMap_(SHAMapType::STATE, info.accountHash, family)
     , rules_(std::move(rules))
@@ -310,27 +335,48 @@ Ledger::Ledger(
     setup();
 }
 
-void
+bool
 Ledger::setImmutable(bool rehash)
 {
-    // Force update, since this is the only
-    // place the hash transitions to valid
-    if (!immutable_ && rehash)
+    // An immutable ledger is treated as persistable, so an invalid map must never become
+    // immutable. The validity test runs before anything is written, so a refusal leaves
+    // the header as it was.
+    if (!mapsValid())
+        return false;
+
+    // Read now but written to the header below: getHash() can unshare a dirty tree, so it must run
+    // while the map is still mutable, while the header may only be written once both maps are
+    // settled. Skipped when the ledger is already immutable or when the header supplied these.
+    bool const deriveMapHashes = !immutable_ && !mapHashesFromHeader_ && rehash;
+    UInt256 const txHash = deriveMapHashes ? txMap_.getHash().asUInt256() : UInt256{};
+    UInt256 const accountHash = deriveMapHashes ? stateMap_.getHash().asUInt256() : UInt256{};
+
+    // A concurrent walk can invalidate a map between the check above and here (see
+    // SHAMap::state_), so the result is checked. That narrows the window rather than closing it,
+    // since setInvalid() outranks Immutable.
+    bool const bothImmutable = setMapsImmutable();
+    SOMETIMES(!bothImmutable, "xrpl::Ledger::setImmutable : map invalidated while going immutable");
+    if (!bothImmutable)
+        return false;  // LCOV_EXCL_LINE: only the walk named above reaches this, so no test does
+
+    // Written only now, so failing the check above leaves the header describing what the ledger was
+    // built from. Forced, since this is the only place the hash transitions to valid.
+    if (deriveMapHashes)
     {
-        header_.txHash = txMap_.getHash().asUInt256();
-        header_.accountHash = stateMap_.getHash().asUInt256();
+        header_.txHash = txHash;
+        header_.accountHash = accountHash;
     }
 
     if (rehash)
         header_.hash = calculateLedgerHash(header_);
 
+    // Set last, so isImmutable() reports only a ledger whose maps are both immutable.
     immutable_ = true;
-    txMap_.setImmutable();
-    stateMap_.setImmutable();
     setup();
+    return true;
 }
 
-void
+bool
 Ledger::setAccepted(
     NetClock::time_point closeTime,
     NetClock::duration closeResolution,
@@ -342,7 +388,17 @@ Ledger::setAccepted(
     header_.closeTime = closeTime;
     header_.closeTimeResolution = closeResolution;
     header_.closeFlags = correctCloseTime ? 0 : kSLcfNoConsensusTime;
-    setImmutable();
+    // Built locally. See Ledger::setImmutable().
+    if (!setImmutable())
+    {
+        // LCOV_EXCL_START
+        JLOG(j_.error()) << "Invalid map for accepted ledger " << header_.seq;
+        UNREACHABLE("xrpl::Ledger::setAccepted : map is invalid");
+        return false;
+        // LCOV_EXCL_STOP
+    }
+
+    return true;
 }
 
 bool
@@ -566,6 +622,7 @@ Ledger::setup()
         {
             bool oldFees = false;
             bool newFees = false;
+            bool extensionFees = false;
             {
                 auto const baseFee = sle->at(~sfBaseFee);
                 auto const reserveBase = sle->at(~sfReserveBase);
@@ -600,6 +657,20 @@ Ledger::setup()
                 assign(fees_.increment, reserveIncrementXRP);
                 newFees = baseFeeXRP || reserveBaseXRP || reserveIncrementXRP;
             }
+            {
+                auto const gasLimit = sle->at(~sfGasLimit);
+                auto const bytecodeSizeLimit = sle->at(~sfBytecodeSizeLimit);
+                auto const gasPrice = sle->at(~sfGasPrice);
+
+                // An absent field resolves to the protocol constant.
+                if (rules_.enabled(featureSmartEscrow))
+                {
+                    fees_.gasLimit = gasLimit.value_or(kDefaultGasLimit);
+                    fees_.bytecodeSizeLimit = bytecodeSizeLimit.value_or(kDefaultBytecodeSizeLimit);
+                    fees_.gasPrice = gasPrice.value_or(kDefaultGasPrice);
+                }
+                extensionFees = gasLimit || bytecodeSizeLimit || gasPrice;
+            }
             if (oldFees && newFees)
             {
                 // Should be all of one or the other, but not both
@@ -610,6 +681,12 @@ Ledger::setup()
                 // Can't populate the new fees before the amendment is enabled
                 ret = false;
             }
+            if (!rules_.enabled(featureSmartEscrow) && extensionFees)
+            {
+                // Can't populate the extension fees before the amendment is
+                // enabled
+                ret = false;
+            }
         }
     }
     catch (SHAMapMissingNode const&)

src/libxrpl/ledger/PaymentSandbox.cpp

@@ -435,8 +435,6 @@ PaymentSandbox::issuerSelfDebitHookMPT(
     std::uint64_t amount,
     std::int64_t origBalance)
 {
-    XRPL_ASSERT(amount > 0, "PaymentSandbox::issuerSelfDebitHookMPT: amount must be > 0");
-
     tab_.issuerSelfDebitMPT(issue, amount, origBalance);
 }
 

src/libxrpl/ledger/View.cpp

@@ -511,9 +511,14 @@ doWithdraw(
     AccountID const& dstAcct,
     AccountID const& sourceAcct,
     XRPAmount priorBalance,
-    STAmount const& amount,
+    STAmount const& destinationAmount,
+    STAmount const& sourceAmount,
     beast::Journal j)
 {
+    XRPL_ASSERT(
+        destinationAmount.asset() == sourceAmount.asset(),
+        "xrpl::doWithdraw : delivered and source amounts use the same asset");
+
     auto const dstSle = ctx.view.read(keylet::account(dstAcct));
 
     // Create a trust line or MPToken for a self-destination only when there
@@ -523,9 +528,10 @@ doWithdraw(
     // create+delete MPTokens in the same transaction.
     if (dstAcct == senderAcct)
     {
-        if (amount > beast::kZero || !ctx.view.rules().enabled(fixCleanup3_4_0))
+        if (destinationAmount > beast::kZero || !ctx.view.rules().enabled(fixCleanup3_4_0))
         {
-            if (auto const ter = addEmptyHolding(ctx, senderAcct, priorBalance, amount.asset(), j);
+            if (auto const ter =
+                    addEmptyHolding(ctx, senderAcct, priorBalance, destinationAmount.asset(), j);
                 !isTesSuccess(ter) && ter != tecDUPLICATE)
                 return ter;
         }
@@ -540,17 +546,33 @@ doWithdraw(
     if (accountHolds(
             ctx.view,
             sourceAcct,
-            amount.asset(),
+            destinationAmount.asset(),
             FreezeHandling::IgnoreFreeze,
             AuthHandling::IgnoreAuth,
-            j) < amount)
+            j) < sourceAmount)
     {
         // LCOV_EXCL_START
-        JLOG(j.error()) << "doWithdraw: negative balance of broker cover assets.";
+        JLOG(j.error()) << "doWithdraw: source account holds fewer assets than the withdrawal.";
         return tefINTERNAL;
         // LCOV_EXCL_STOP
     }
 
+    // A transfer fee applies. Redeem the gross amount with the issuer, then
+    // issue the net amount to the destination.
+    if (sourceAmount != destinationAmount)
+    {
+        auto const issuer = destinationAmount.getIssuer();
+        XRPL_ASSERT(
+            !destinationAmount.native() && sourceAcct != issuer && dstAcct != issuer,
+            "xrpl::doWithdraw : transfer fee applies between token holders");
+
+        if (auto const ter = directSendNoFee(ctx.view, sourceAcct, issuer, sourceAmount, false, j);
+            !isTesSuccess(ter))
+            return ter;  // LCOV_EXCL_LINE
+
+        return directSendNoFee(ctx.view, issuer, dstAcct, destinationAmount, false, j);
+    }
+
     // A reserve sponsor only covers tx.Account's own objects, so resolve the
     // sponsor against the destination. accountSend can auto-create a holding
     // for dstAcct; keying on the destination ensures a third-party destination's
@@ -562,7 +584,7 @@ doWithdraw(
     // Move the funds directly from the broker's pseudo-account to the
     // dstAcct
     return accountSend(
-        ctx.view, sourceAcct, dstAcct, amount, j, *sponsorSle, WaiveTransferFee::Yes);
+        ctx.view, sourceAcct, dstAcct, destinationAmount, j, *sponsorSle, WaiveTransferFee::Yes);
 }
 
 TER

src/libxrpl/ledger/helpers/AMMHelpers.cpp

@@ -213,49 +213,19 @@ adjustAmountsByLPTokens(
 
     if (lpTokensActual < lpTokens)
     {
-        bool const ammRoundingEnabled = [&] {
-            if (auto const& rules = getCurrentTransactionRules();
-                rules && rules->enabled(fixAMMv1_1))
-                return true;
-            return false;
-        }();
-
         // Equal trade
         if (amount2)
         {
             Number const fr = lpTokensActual / lpTokens;
             auto const amountActual = toSTAmount(amount.asset(), fr * amount);
             auto const amount2Actual = toSTAmount(amount2->asset(), fr * *amount2);
-            if (!ammRoundingEnabled)
-            {
-                return std::make_tuple(
-                    amountActual < amount ? amountActual : amount,
-                    amount2Actual < amount2 ? amount2Actual : amount2,
-                    lpTokensActual);
-            }
-
             return std::make_tuple(amountActual, amount2Actual, lpTokensActual);
         }
 
         // Single trade
-        auto const amountActual = [&] {
-            if (isDeposit == IsDeposit::Yes)
-            {
-                return ammAssetIn(amountBalance, lptAMMBalance, lpTokensActual, tfee);
-            }
-            if (!ammRoundingEnabled)
-            {
-                return ammAssetOut(amountBalance, lptAMMBalance, lpTokens, tfee);
-            }
-
-            return ammAssetOut(amountBalance, lptAMMBalance, lpTokensActual, tfee);
-        }();
-        if (!ammRoundingEnabled)
-        {
-            return amountActual < amount
-                ? std::make_tuple(amountActual, std::nullopt, lpTokensActual)
-                : std::make_tuple(amount, std::nullopt, lpTokensActual);
-        }
+        auto const amountActual = isDeposit == IsDeposit::Yes
+            ? ammAssetIn(amountBalance, lptAMMBalance, lpTokensActual, tfee)
+            : ammAssetOut(amountBalance, lptAMMBalance, lpTokensActual, tfee);
 
         return std::make_tuple(amountActual, std::nullopt, lpTokensActual);
     }
@@ -980,7 +950,7 @@ verifyAndAdjustLPTokenBalance(
         }
         else
         {
-            return std::unexpected<TER>(tecAMM_INVALID_TOKENS);
+            return std::unexpected<TER>(tecAMM_INVALID_TOKENS);  // LCOV_EXCL_LINE
         }
     }
     return true;

src/libxrpl/ledger/helpers/LendingHelpers.cpp

@@ -66,6 +66,161 @@ canApplyToBrokerCover(
     return tesSUCCESS;
 }
 
+namespace detail {
+
+[[nodiscard]] int
+getPosteriorBrokerCoverScale(SLE::ConstRef vault, SLE::ConstRef broker, Number const& delta)
+{
+    XRPL_ASSERT(
+        vault && vault->getType() == ltVAULT,
+        "xrpl::detail::getPosteriorBrokerCoverScale : valid Vault sle");
+    XRPL_ASSERT(
+        broker && broker->getType() == ltLOAN_BROKER,
+        "xrpl::detail::getPosteriorBrokerCoverScale : valid LoanBroker sle");
+
+    return posteriorAssetScale(
+        getVaultVersion(vault),
+        vault->at(sfAsset),
+        getVaultBaseScale(vault),
+        broker->at(sfCoverAvailable),
+        delta);
+}
+
+[[nodiscard]] STAmount
+roundToPosteriorBrokerCoverScale(
+    SLE::ConstRef vault,
+    SLE::ConstRef broker,
+    STAmount const& delta,
+    Number::RoundingMode roundingMode)
+{
+    XRPL_ASSERT(
+        vault && vault->getType() == ltVAULT,
+        "xrpl::detail::roundToPosteriorBrokerCoverScale : valid Vault sle");
+    XRPL_ASSERT(
+        broker && broker->getType() == ltLOAN_BROKER,
+        "xrpl::detail::roundToPosteriorBrokerCoverScale : valid LoanBroker sle");
+    XRPL_ASSERT(
+        delta.asset() == vault->at(sfAsset),
+        "xrpl::detail::roundToPosteriorBrokerCoverScale : delta and Vault asset match");
+    if (delta.integral())
+        return delta;
+    return roundToScale(delta, getPosteriorBrokerCoverScale(vault, broker, delta), roundingMode);
+}
+
+}  // namespace detail
+
+[[nodiscard]] STAmount
+creditToPosteriorBrokerCoverScale(
+    SLE::ConstRef vault,
+    SLE::ConstRef broker,
+    Number const& raw,
+    Number::RoundingMode roundingMode)
+{
+    XRPL_ASSERT(
+        vault && vault->getType() == ltVAULT,
+        "xrpl::creditToPosteriorBrokerCoverScale : valid Vault sle");
+    XRPL_ASSERT(
+        broker && broker->getType() == ltLOAN_BROKER,
+        "xrpl::creditToPosteriorBrokerCoverScale : valid LoanBroker sle");
+    Asset const asset = vault->at(sfAsset);
+    if (asset.integral())
+    {
+        NumberRoundModeGuard const rg(roundingMode);
+        return STAmount{asset, raw};
+    }
+
+    Number const reference = broker->at(sfCoverAvailable);
+    return detail::creditToPosteriorScale(
+        asset, reference, getVaultBaseScale(vault), raw, roundingMode);
+}
+
+[[nodiscard]] STAmount
+debitToPosteriorBrokerCoverScale(
+    SLE::ConstRef vault,
+    SLE::ConstRef broker,
+    STAmount const& amount,
+    Number::RoundingMode roundingMode)
+{
+    XRPL_ASSERT(
+        vault && vault->getType() == ltVAULT,
+        "xrpl::debitToPosteriorBrokerCoverScale : valid Vault sle");
+    XRPL_ASSERT(
+        broker && broker->getType() == ltLOAN_BROKER,
+        "xrpl::debitToPosteriorBrokerCoverScale : valid LoanBroker sle");
+    XRPL_ASSERT(
+        amount.asset() == vault->at(sfAsset),
+        "xrpl::debitToPosteriorBrokerCoverScale : amount and Vault asset match");
+    XRPL_ASSERT(!amount.negative(), "xrpl::debitToPosteriorBrokerCoverScale : non-negative amount");
+    return -detail::roundToPosteriorBrokerCoverScale(vault, broker, -amount, roundingMode);
+}
+
+[[nodiscard]] TER
+checkOptionalBrokerCoverInflow(SLE::ConstRef vault, SLE::ConstRef broker, STAmount const& amount)
+{
+    XRPL_ASSERT(
+        vault && vault->getType() == ltVAULT,
+        "xrpl::checkOptionalBrokerCoverInflow : valid Vault sle");
+    XRPL_ASSERT(
+        broker && broker->getType() == ltLOAN_BROKER,
+        "xrpl::checkOptionalBrokerCoverInflow : valid LoanBroker sle");
+    XRPL_ASSERT(
+        amount.asset() == vault->at(sfAsset),
+        "xrpl::checkOptionalBrokerCoverInflow : amount and Vault asset match");
+    XRPL_ASSERT(!amount.negative(), "xrpl::checkOptionalBrokerCoverInflow : non-negative amount");
+    if (getVaultVersion(vault) != VaultVersion::FixedPrecision)
+        return tesSUCCESS;
+
+    // amount is the effective credit (already floored on the posterior
+    // CoverAvailable grid by creditToPosteriorBrokerCoverScale); rounding it
+    // again as a standalone delta could hide a crossing.
+    STAmount const& rounded = amount;
+    int const baseScale = getVaultBaseScale(vault);
+    // Keep this explicit even though the Open-limit capacity check below rejects
+    // every coarsening transition too. The protocol defines both conditions
+    // independently.
+    if (detail::getPosteriorBrokerCoverScale(vault, broker, rounded) != baseScale)
+        return tecLIMIT_EXCEEDED;
+
+    Number const posterior = [&] {
+        NumberRoundModeGuard const rg(Number::RoundingMode::TowardsZero);
+        return broker->at(sfCoverAvailable) + rounded;
+    }();
+    if (posterior > getVaultOpenLimit(vault))
+        return tecLIMIT_EXCEEDED;
+    return tesSUCCESS;
+}
+
+void
+adjustBrokerDebtTotal(
+    SLE::Ref brokerSle,
+    SLE::ConstRef vaultSle,
+    Number const& delta,
+    int vaultScale)
+{
+    // On FixedPrecision Vaults, LoanSet adds principal to DebtTotal exactly, LoanPay and default
+    // subtract exact amounts. Thus DebtTotal must not be rounded coarser than the base scale.
+    if (getVaultVersion(vaultSle) == VaultVersion::FixedPrecision)
+    {
+        brokerSle->at(sfDebtTotal) += delta;
+    }
+    else
+    {
+        adjustImpreciseNumber(brokerSle->at(sfDebtTotal), delta, vaultSle->at(sfAsset), vaultScale);
+    }
+}
+
+Number
+minimumBrokerCover(Number const& debtTotal, TenthBips32 coverRateMinimum, SLE::ConstRef vaultSle)
+{
+    XRPL_ASSERT(
+        vaultSle && vaultSle->getType() == ltVAULT, "xrpl::minimumBrokerCover : valid Vault sle");
+    NumberRoundModeGuard const mg(Number::RoundingMode::Upward);
+    return roundToAsset(
+        vaultSle->at(sfAsset),
+        tenthBipsOfValue(debtTotal, coverRateMinimum),
+        getVaultBaseScale(vaultSle));
+}
+
 bool
 checkLendingProtocolDependencies(Rules const& rules, STTx const& tx)
 {
@@ -250,14 +405,13 @@ loanPaymentDeltas(LoanPaymentParts const& parts)
 
 namespace {
 
-// Cash-basis accounting applies only when featureLendingProtocolV1_1 is
-// enabled AND the specific Vault was created under it (LEVersion ==
-// VaultVersion::CashBasis). Vaults created before activation keep instant
-// interest recognition forever, even after the amendment later turns on.
+// Cash-basis accounting applies to Vaults created under
+// featureLendingProtocolV1_1 or a later version. Vaults created before
+// activation keep instant interest recognition forever.
 bool
 cashBasisEnabled(SLE::ConstRef vaultSle)
 {
-    return getVaultVersion(vaultSle) == VaultVersion::CashBasis;
+    return getVaultVersion(vaultSle) >= VaultVersion::CashBasis;
 }
 
 }  // namespace

src/libxrpl/ledger/helpers/MPTokenHelpers.cpp

@@ -1047,6 +1047,14 @@ maxMPTAmount(SLE const& sleIssuance)
     return sleIssuance[~sfMaximumAmount].value_or(kMaxMpTokenAmount);
 }
 
+std::optional<std::int64_t>
+maxMPTAmount(ReadView const& view, MPTID const& mptID)
+{
+    if (auto const sle = view.read(keylet::mptokenIssuance(mptID)))
+        return maxMPTAmount(*sle);
+    return std::nullopt;
+}
+
 std::int64_t
 availableMPTAmount(SLE const& sleIssuance)
 {

src/libxrpl/ledger/helpers/ProposalHelpers.cpp

@@ -1,18 +1,51 @@
 #include <xrpl/ledger/helpers/ProposalHelpers.h>
 
+#include <xrpl/basics/Log.h>
+#include <xrpl/basics/Slice.h>
+#include <xrpl/beast/utility/Journal.h>
+#include <xrpl/beast/utility/instrumentation.h>
+#include <xrpl/ledger/ApplyView.h>
+#include <xrpl/ledger/ReadView.h>
+#include <xrpl/ledger/View.h>
+#include <xrpl/ledger/helpers/AccountRootHelpers.h>
+#include <xrpl/protocol/AccountID.h>
+#include <xrpl/protocol/Indexes.h>
+#include <xrpl/protocol/Keylet.h>
+#include <xrpl/protocol/LedgerFormats.h>
 #include <xrpl/protocol/SField.h>
 #include <xrpl/protocol/STArray.h>
+#include <xrpl/protocol/STLedgerEntry.h>
 #include <xrpl/protocol/STObject.h>
 #include <xrpl/protocol/STTx.h>
+#include <xrpl/protocol/Serializer.h>
+#include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/TxFlags.h>
 #include <xrpl/protocol/TxFormats.h>
 
+#include <algorithm>
+#include <array>
+#include <cstdint>
+#include <optional>
+
 namespace xrpl::proposal {
 
+namespace {
+
+// Proposals do not nest, so a proposed transaction may carry none of these
+// types, neither as its own payload nor as a Batch inner transaction.
+constexpr auto kProposalTxTypes = std::to_array<TxType>({
+    ttTRANSACTION_PROPOSAL_CREATE,
+    ttTRANSACTION_PROPOSAL_CANCEL,
+});
+
+}  // namespace
+
 bool
-isValidProposal(STObject const& proposedTx)
+isValidProposalTxnType(STObject const& proposedTx)
 {
-    if (isProposalTx(proposedTx))
+    auto const type = proposedTx.getFieldU16(sfTransactionType);
+
+    if (std::ranges::find(kProposalTxTypes, type) != kProposalTxTypes.end())
         return false;
 
     if (isPseudoTx(proposedTx))
@@ -22,13 +55,24 @@ isValidProposal(STObject const& proposedTx)
         (proposedTx.getFieldU32(sfFlags) & tfInnerBatchTxn) != 0u)
         return false;
 
-    if (proposedTx.getFieldU16(sfTransactionType) == ttBATCH &&
-        proposedTx.isFieldPresent(sfRawTransactions))
+    if (type == ttBATCH && proposedTx.isFieldPresent(sfRawTransactions))
     {
         STArray const& innerTxns = proposedTx.getFieldArray(sfRawTransactions);
         for (STObject const& inner : innerTxns)
         {
-            if (isProposalTx(inner) || isPseudoTx(inner))
+            // The only production caller reaches this walk through STTx
+            // construction, which rejects a typeless inner first, so this is
+            // re-checked rather than relied upon.
+            if (!inner.isFieldPresent(sfTransactionType))
+                return false;
+
+            auto const innerType = inner.getFieldU16(sfTransactionType);
+
+            // A nested Batch is rejected alongside nested proposals and
+            // pseudo-transactions: STTx construction forbids inner Batches, so
+            // a proposal must not be able to store one either.
+            if (std::ranges::find(kProposalTxTypes, innerType) != kProposalTxTypes.end() ||
+                innerType == ttBATCH || isPseudoTx(inner))
                 return false;
         }
     }
@@ -36,4 +80,112 @@ isValidProposal(STObject const& proposedTx)
     return true;
 }
 
+bool
+isTerminal(
+    ReadView const& view,
+    std::optional<std::uint32_t> expiration,
+    STObject const& proposedTx)
+{
+    if (hasExpired(view, expiration))
+        return true;
+
+    // Mirror the ordinary transactor's tefMAX_LEDGER rule: view.seq() > bound.
+    // At view.seq() == bound the payload can still be submitted, so the
+    // proposal is still live (On-Chain Cosigner spec §4.5).
+    return proposedTx.isFieldPresent(sfLastLedgerSequence) &&
+        view.seq() > proposedTx.getFieldU32(sfLastLedgerSequence);
+}
+
+TER
+deleteProposal(ApplyView& view, SLE::pointer const& sleProposal, beast::Journal j)
+{
+    if (!sleProposal || sleProposal->getType() != ltTRANSACTION_PROPOSAL ||
+        !view.exists(Keylet{ltTRANSACTION_PROPOSAL, sleProposal->key()}))
+    {
+        // LCOV_EXCL_START
+        JLOG(j.fatal()) << "Invalid TransactionProposal deletion.";
+        return tecINTERNAL;
+        // LCOV_EXCL_STOP
+    }
+
+    AccountID const owner = sleProposal->getAccountID(sfOwner);
+
+    std::uint64_t const page{(*sleProposal)[sfOwnerNode]};
+    if (!view.dirRemove(keylet::ownerDir(owner), page, sleProposal->key(), true))
+    {
+        // LCOV_EXCL_START
+        JLOG(j.fatal()) << "Unable to delete TransactionProposal from owner.";
+        return tefBAD_LEDGER;
+        // LCOV_EXCL_STOP
+    }
+
+    auto const sleOwner = view.peek(keylet::account(owner));
+    if (!sleOwner)
+    {
+        // LCOV_EXCL_START
+        JLOG(j.fatal()) << "Could not find TransactionProposal owner account root.";
+        return tefBAD_LEDGER;
+        // LCOV_EXCL_STOP
+    }
+
+    // Release the reserve against the Owner or, if the entry carries a
+    // reserve sponsor, against that sponsor.
+    decreaseOwnerCountForObject(
+        view,
+        sleOwner,
+        sleProposal,
+        proposalOwnerCount(sleProposal->getFieldObject(sfProposedTransaction)),
+        j);
+
+    view.erase(sleProposal);
+    return tesSUCCESS;
+}
+
+bool
+payloadMatches(STObject const& proposedTx, STObject const& tx)
+{
+    XRPL_ASSERT(
+        proposedTx.isFieldPresent(sfTransactionType) && tx.isFieldPresent(sfTransactionType),
+        "xrpl::proposal::payloadMatches : transaction-shaped inputs");
+
+    // The signing-payload serialization omits every kNotSigning field: the
+    // signature containers a proposal lets evolve (TxnSignature, Signers,
+    // BatchSigners, CounterpartySignature, SponsorSignature) plus Signature
+    // and MasterSignature, which the account's own signature does not cover
+    // either (see the header). What remains is the field set fixed at
+    // creation — except SigningPubKey, which signing payloads include but
+    // which is also mutable here (stored empty, filled if the target signs
+    // with its own key). Neutralize it on both sides before comparing.
+    auto const payloadBytes = [](STObject const& obj) {
+        STObject copy{obj};
+        copy.setFieldVL(sfSigningPubKey, Slice{});
+        Serializer s;
+        copy.addWithoutSigningFields(s);
+        return s.getData();
+    };
+
+    return payloadBytes(proposedTx) == payloadBytes(tx);
+}
+
+bool
+canConsumeTicket(ReadView const& view, STTx const& tx)
+{
+    auto const seqProx = tx.getSeqProxy();
+    if (!seqProx.isTicket())
+    {
+        // The caller only reaches here for a Ticket-based transaction.
+        // LCOV_EXCL_START
+        UNREACHABLE("xrpl::proposal::canConsumeTicket : tx spends a Sequence");
+        return false;
+        // LCOV_EXCL_STOP
+    }
+
+    auto const sleProposal =
+        view.read(keylet::txProposal(tx.getAccountID(sfAccount), seqProx.value()));
+    if (!sleProposal)
+        return true;
+
+    return payloadMatches(sleProposal->getFieldObject(sfProposedTransaction), tx);
+}
+
 }  // namespace xrpl::proposal

src/libxrpl/ledger/helpers/TokenHelpers.cpp

@@ -2,6 +2,7 @@
 
 #include <xrpl/basics/Log.h>
 #include <xrpl/basics/MathUtilities.h>
+#include <xrpl/basics/Number.h>
 #include <xrpl/beast/utility/Journal.h>
 #include <xrpl/beast/utility/Zero.h>
 #include <xrpl/beast/utility/instrumentation.h>
@@ -551,6 +552,22 @@ transferRate(ReadView const& view, STAmount const& amount)
     return transferRate(view, amount.asset());
 }
 
+STAmount
+addTransferFee(STAmount const& amount, Rate const& rate)
+{
+    if (rate == kParityRate)
+        return amount;
+    return mulRatio(amount, rate.value, QUALITY_ONE, Number::RoundingMode::Upward);
+}
+
+STAmount
+subtractTransferFee(STAmount const& amount, Rate const& rate)
+{
+    if (rate == kParityRate)
+        return amount;
+    return mulRatio(amount, QUALITY_ONE, rate.value, Number::RoundingMode::Downward);
+}
+
 //------------------------------------------------------------------------------
 //
 // Holding operations
@@ -973,19 +990,11 @@ accountSendIOU(
     SLE::Ref sponsorSle,
     WaiveTransferFee waiveFee)
 {
-    if (view.rules().enabled(fixAMMv1_1))
-    {
-        if (saAmount < beast::kZero || saAmount.holds<MPTIssue>())
-        {
-            return tecINTERNAL;  // LCOV_EXCL_LINE
-        }
-    }
-    else
+    if (saAmount < beast::kZero || saAmount.holds<MPTIssue>())
     {
         // LCOV_EXCL_START
-        XRPL_ASSERT(
-            saAmount >= beast::kZero && !saAmount.holds<MPTIssue>(),
-            "xrpl::accountSendIOU : minimum amount and not MPT");
+        JLOG(j.fatal()) << "accountSendIOU: negative amount or invalid asset";
+        return tecINTERNAL;
         // LCOV_EXCL_STOP
     }
 
@@ -1355,9 +1364,8 @@ directSendNoLimitMPT(
         {
             // Number math loses precision on large MPT amounts, which can
             // overcharge the sender. MPTs are integral, so compute the cost
-            // exactly and round it up, matching the payment engine.
-            auto const cost = mulRatio(saAmount.mpt(), rate.value, QUALITY_ONE, true);
-            saActual = STAmount(saAmount.asset(), cost.value());
+            // exactly, matching the payment engine.
+            saActual = addTransferFee(saAmount, rate);
         }
         else
         {
@@ -1482,9 +1490,8 @@ directSendNoLimitMultiMPT(
             {
                 // Number math loses precision on large MPT amounts, which can
                 // overcharge the sender. MPTs are integral, so compute the
-                // cost exactly and round it up, matching the payment engine.
-                auto const cost = mulRatio(amount.mpt(), rate.value, QUALITY_ONE, true);
-                actualSend = STAmount(amount.asset(), cost.value());
+                // cost exactly, matching the payment engine.
+                actualSend = addTransferFee(amount, rate);
             }
             else
             {

src/libxrpl/ledger/helpers/VaultHelpers.cpp

@@ -25,6 +25,8 @@
 #include <cstdint>
 #include <expected>
 #include <optional>
+#include <stdexcept>
+#include <string_view>
 #include <utility>
 
 namespace xrpl {
@@ -46,7 +48,7 @@ fixedBaseScale(SLE::ConstRef vault)
 }
 
 // Thin, vault-specific wrapper over posteriorAssetScale: used by
-// getPosteriorVaultScale and creditToPosteriorAvailableScale.
+// getPosteriorVaultScale and the cash outflow rounding below.
 [[nodiscard]] int
 posteriorScale(SLE::ConstRef vault, Number const& reference, Number const& delta)
 {
@@ -134,6 +136,18 @@ syncAssetsTotal(SLE::Ref vault)
     vault->at(sfAssetsTotal) = STAmount{asset, getAssetsTotal(vault)};
 }
 
+[[nodiscard]] bool
+debitIsNonZeroDust(SLE::ConstRef vault, Number const& amount)
+{
+    if (amount == 0)
+        return false;
+
+    auto const total = getVaultVersion(vault) == VaultVersion::FixedPrecision
+        ? vault->at(sfAssetsAvailable)
+        : getAssetsTotal(vault);
+    auto const asset = vault->at(sfAsset);
+    return STAmount{asset, total - amount} == STAmount{asset, total};
+}
 }  // namespace
 
 namespace detail {
@@ -181,11 +195,11 @@ posteriorAssetScale(
 creditToPosteriorScale(
     Asset const& asset,
     Number const& reference,
-    int atScale,
+    int baseScale,
     Number const& raw,
     Number::RoundingMode roundingMode)
 {
-    // Floor the SUM (reference + raw), not just raw, at atScale. See
+    // Floor the SUM (reference + raw), not just raw. See
     // creditToPosteriorAvailableScale's doc: a delta floored on its own grid
     // can still leave a 17-digit sum once the reference has crossed a power
     // of ten.
@@ -194,9 +208,21 @@ creditToPosteriorScale(
     // than Number holds (the sum is on the posterior grid, the reference on
     // the finer one). Compute both under roundingMode, not the caller's
     // ambient mode, so the credit this returns never exceeds raw.
+    //
+    // Take the grid from this same sum. A sum just under a power of ten that
+    // rounds up to it in another mode would pick the coarser grid, and
+    // flooring the unrounded sum on it would land below reference.
     NumberRoundModeGuard const rg(roundingMode);
-    Number const flooredSum = roundToAsset(asset, reference + raw, atScale, roundingMode);
-    return STAmount{asset, flooredSum - reference};
+    Number const sum = reference + raw;
+    int const atScale = liveScale(sum, asset, baseScale);
+    Number const flooredSum = roundToAsset(asset, sum, atScale, roundingMode);
+    STAmount const credit{asset, flooredSum - reference};
+    XRPL_ASSERT_PARTS(
+        roundingMode != Number::RoundingMode::Downward ||
+            (credit >= beast::kZero && Number(credit) <= raw),
+        "xrpl::detail::creditToPosteriorScale",
+        "credit is between zero and raw");
+    return credit;
 }
 
 [[nodiscard]] int
@@ -302,6 +328,17 @@ adjustVaultBalances(SLE::Ref vault, VaultBalanceChange const& change, beast::Jou
     return tesSUCCESS;
 }
 
+[[nodiscard]] TER
+adjustVaultCash(SLE::Ref vault, STAmount const& delta, beast::Journal j)
+{
+    if (getVaultVersion(vault) == VaultVersion::FixedPrecision)
+        return adjustVaultBalances(vault, {.cash = delta}, j);
+
+    vault->at(sfAssetsTotal) += delta;
+    vault->at(sfAssetsAvailable) += delta;
+    return tesSUCCESS;
+}
+
 [[nodiscard]] int
 getVaultScale(SLE::ConstRef vault)
 {
@@ -374,8 +411,8 @@ creditToPosteriorAvailableScale(
     }
 
     Number const reference = vault->at(sfAssetsAvailable);
-    int const scale = posteriorScale(vault, reference, raw);
-    return detail::creditToPosteriorScale(asset, reference, scale, raw, roundingMode);
+    return detail::creditToPosteriorScale(
+        asset, reference, fixedBaseScale(vault), raw, roundingMode);
 }
 
 [[nodiscard]] Number
@@ -428,6 +465,36 @@ vaultOpenZoneCapacity(SLE::ConstRef vault, Number const& roundedAmount)
     return getAssetsTotal(vault) + vault->at(sfYieldUnrealized) + roundedAmount;
 }
 
+[[nodiscard]] TER
+checkDebitNotDust(
+    SLE::ConstRef vault,
+    Number const& amount,
+    beast::Journal j,
+    std::string_view name)
+{
+    try
+    {
+        if (debitIsNonZeroDust(vault, amount))
+        {
+            JLOG(j.debug()) << name << ": amount too small to change stored vault balance";
+            return tecPRECISION_LOSS;
+        }
+    }
+    // LCOV_EXCL_START
+    catch (std::overflow_error const&)
+    {
+        // It's easy to hit this exception from Number with large enough Scale
+        // so we avoid spamming the log and only use debug here.
+        JLOG(j.debug())  //
+            << name << ": overflow error with"
+            << " scale=" << (int)vault->at(sfScale)  //
+            << ", assetsTotal=" << vault->at(sfAssetsTotal) << ", amount=" << amount;
+        return tecPATH_DRY;
+    }
+    // LCOV_EXCL_STOP
+    return tesSUCCESS;
+}
+
 [[nodiscard]] std::optional<STAmount>
 assetsToSharesDeposit(SLE::ConstRef vault, SLE::ConstRef issuance, STAmount const& assets)
 {
@@ -575,6 +642,14 @@ isOnVaultBaseGrid(Asset const& asset, Number const& value, int baseScale)
         roundToAsset(asset, value, baseScale, Number::RoundingMode::TowardsZero) == value;
 }
 
+[[nodiscard]] TER
+checkAssetsMaximum(SLE::ConstRef vault, Number const& amount)
+{
+    return isOnVaultBaseGrid(vault->at(sfAsset), amount, getVaultBaseScale(vault))
+        ? TER{tesSUCCESS}
+        : TER{tecPRECISION_LOSS};
+}
+
 [[nodiscard]] Number
 assetsTotalForWithdrawal(SLE::ConstRef vault, WaiveUnrealizedLoss waive)
 {
@@ -584,22 +659,6 @@ assetsTotalForWithdrawal(SLE::ConstRef vault, WaiveUnrealizedLoss waive)
     return assetTotal;
 }
 
-[[nodiscard]] bool
-debitIsNonZeroDust(Asset const& asset, Number const& total, Number const& amount)
-{
-    if (amount == 0)
-        return false;
-    return STAmount{asset, total - amount} == STAmount{asset, total};
-}
-
-[[nodiscard]] Number
-vaultDebitDustReference(SLE::ConstRef vault, Number const& assetsTotal)
-{
-    return getVaultVersion(vault) == VaultVersion::FixedPrecision
-        ? Number(vault->at(sfAssetsAvailable))
-        : assetsTotal;
-}
-
 [[nodiscard]] std::optional<STAmount>
 assetsToSharesWithdraw(
     SLE::ConstRef vault,
@@ -695,9 +754,10 @@ getVaultVersion(SLE::ConstRef vault)
 [[nodiscard]] VaultVersion
 getVaultDefaultVersion(Rules const& rules)
 {
-    // FixedPrecision requires both cleanups, so a FixedPrecision Vault always
-    // sees them enabled.
-    if (rules.enabled(featureLendingProtocolV1_2) && rules.enabled(fixCleanup3_2_0) &&
+    // FixedPrecision requires featureLendingProtocolV1_1 (closed-ended Vaults and
+    // cash-basis accounting) and fixCleanup3_4_0, so a FixedPrecision Vault always
+    // sees both enabled. fixCleanup3_2_0 is already enabled on the network.
+    if (rules.enabled(featureLendingProtocolV1_1) && rules.enabled(featureLendingProtocolV1_2) &&
         rules.enabled(fixCleanup3_4_0))
         return VaultVersion::FixedPrecision;
     if (rules.enabled(featureLendingProtocolV1_1))

src/libxrpl/protocol/ConfidentialTransfer.cpp

@@ -435,18 +435,25 @@ areMirrorsCurrent(SLE const& issuance, SLE const& mptoken)
 }
 
 void
-setIssuerMirrorEpoch(SLE const& issuance, SLE& mptoken)
+setIssuerMirrorCurrent(SLE const& issuance, SLE& mptoken)
 {
     XRPL_ASSERT(
         issuance.getType() == ltMPTOKEN_ISSUANCE,
-        "xrpl::setIssuerMirrorEpoch : issuance MPTokenIssuance object");
+        "xrpl::setIssuerMirrorCurrent : issuance MPTokenIssuance object");
     XRPL_ASSERT(
-        mptoken.getType() == ltMPTOKEN, "xrpl::setIssuerMirrorEpoch : mptoken MPToken object");
+        mptoken.getType() == ltMPTOKEN, "xrpl::setIssuerMirrorCurrent : mptoken MPToken object");
 
     // Unlike the auditor mirror, the issuer mirror is not optional: every
     // confidential MPToken carries one, so there is no existence check here.
+    //
+    // Record the key and epoch under which the mirror is now encrypted. Both fields remain absent
+    // at epoch 0: such mirrors use the original issuer key. The original key is stored in
+    // sfInitialIssuerEncryptionKey after the first rotation.
     if (auto const epoch = issuance[~sfIssuerKeyEpoch].value_or(0); epoch != 0)
+    {
         mptoken[sfIssuerKeyMirrorEpoch] = epoch;
+        mptoken[sfIssuerMirrorEncryptionKey] = issuance[sfIssuerEncryptionKey];
+    }
 }
 
 void
@@ -466,9 +473,9 @@ setAuditorMirrorEpoch(SLE const& issuance, SLE& mptoken)
 }
 
 void
-setMirrorEpochs(SLE const& issuance, SLE& mptoken)
+setMirrorsCurrent(SLE const& issuance, SLE& mptoken)
 {
-    setIssuerMirrorEpoch(issuance, mptoken);
+    setIssuerMirrorCurrent(issuance, mptoken);
     setAuditorMirrorEpoch(issuance, mptoken);
 }
 

src/libxrpl/protocol/MPTAmount.cpp

@@ -1,10 +1,24 @@
 #include <xrpl/protocol/MPTAmount.h>
 
+#include <xrpl/basics/MathUtilities.h>
+#include <xrpl/basics/contract.h>
+#include <xrpl/protocol/Feature.h>
+#include <xrpl/protocol/Rules.h>
+
+#include <stdexcept>
+
 namespace xrpl {
 
 MPTAmount&
 MPTAmount::operator+=(MPTAmount const& other)
 {
+    if (auto const result = checkedAdd(value_, other.value()))
+    {
+        value_ = *result;
+        return *this;
+    }
+    if (isFeatureEnabled(fixCleanup3_5_0, /*resultIfNoRules*/ true))
+        Throw<std::overflow_error>("MPTAmount::operator+= overflow");
     value_ += other.value();
     return *this;
 }
@@ -12,6 +26,13 @@ MPTAmount::operator+=(MPTAmount const& other)
 MPTAmount&
 MPTAmount::operator-=(MPTAmount const& other)
 {
+    if (auto const result = checkedSub(value_, other.value()))
+    {
+        value_ = *result;
+        return *this;
+    }
+    if (isFeatureEnabled(fixCleanup3_5_0, /*resultIfNoRules*/ true))
+        Throw<std::overflow_error>("MPTAmount::operator-= overflow");
     value_ -= other.value();
     return *this;
 }

src/libxrpl/protocol/Quality.cpp

@@ -3,10 +3,14 @@
 #include <xrpl/beast/utility/Zero.h>  // IWYU pragma: keep
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/protocol/Asset.h>
+#include <xrpl/protocol/Feature.h>
+#include <xrpl/protocol/Rules.h>
 #include <xrpl/protocol/STAmount.h>
 
 #include <cstdint>
 #include <limits>  // IWYU pragma: keep
+#include <optional>
+#include <stdexcept>
 
 namespace xrpl {
 
@@ -81,13 +85,46 @@ Quality::ceilInStrict(Amounts const& amount, STAmount const& limit, bool roundUp
     return ceilInImpl<divRoundStrict>(amount, limit, roundUp, *this);
 }
 
+// Returns std::nullopt if a native result can't be represented, instead of
+// throwing. Pathfinding runs without transaction
+// rules, so default to the fixed behavior there to match transactions once the
+// amendment is enabled.
+template <STAmount (*MulRoundFunc)(STAmount const&, STAmount const&, Asset const&, bool)>
+static std::optional<STAmount>
+tryMulRound(STAmount const& v1, STAmount const& v2, Asset const& asset, bool roundUp)
+{
+    try
+    {
+        return MulRoundFunc(v1, v2, asset, roundUp);
+    }
+    catch (std::overflow_error const&)
+    {
+        // std::overflow_error is a std::runtime_error, so it must be caught
+        // first to keep the handler below from swallowing it. It means the
+        // computation itself overflowed, not that the result is out of range.
+        // Callers handle it, e.g. BookStep removes the offer.
+        throw;
+    }
+    catch (std::runtime_error const&)
+    {
+        if (!asset.native() || !isFeatureEnabled(fixCleanup3_5_0, /*resultIfNoRules*/ true))
+            throw;
+        return std::nullopt;
+    }
+}
+
 template <STAmount (*MulRoundFunc)(STAmount const&, STAmount const&, Asset const&, bool)>
 static Amounts
 ceilOutImpl(Amounts const& amount, STAmount const& limit, bool roundUp, Quality const& quality)
 {
     if (amount.out > limit)
     {
-        Amounts result(MulRoundFunc(limit, quality.rate(), amount.in.asset(), roundUp), limit);
+        // An unrepresentable XRP product is larger than amount.in, so the
+        // clamp below would return amount.in anyway.
+        Amounts result(
+            tryMulRound<MulRoundFunc>(limit, quality.rate(), amount.in.asset(), roundUp)
+                .value_or(amount.in),
+            limit);
         // Clamp in
         if (result.in > amount.in)
             result.in = amount.in;

src/libxrpl/protocol/STAmount.cpp

@@ -1,6 +1,7 @@
 #include <xrpl/protocol/STAmount.h>
 
 #include <xrpl/basics/Log.h>
+#include <xrpl/basics/MathUtilities.h>
 #include <xrpl/basics/Number.h>
 #include <xrpl/basics/contract.h>
 #include <xrpl/basics/safe_cast.h>
@@ -384,10 +385,11 @@ operator+(STAmount const& v1, STAmount const& v2)
         return {v1.getFName(), v1.asset(), v2.mantissa(), v2.exponent(), v2.negative()};
     }
 
+    // XRPAmount and MPTAmount check for int64 overflow under fixCleanup3_5_0.
     if (v1.native())
-        return {v1.getFName(), getSNValue(v1) + getSNValue(v2)};
+        return {v1.getFName(), (v1.xrp() + v2.xrp()).drops()};
     if (v1.holds<MPTIssue>())
-        return {v1.asset_, v1.mpt().value() + v2.mpt().value()};
+        return {v1.asset_, (v1.mpt() + v2.mpt()).value()};
 
     auto x = v1;
     x = v1.iou() + v2.iou();
@@ -490,16 +492,7 @@ canAdd(STAmount const& a, STAmount const& b)
 
     // XRP case (overflow & underflow check)
     if (isXRP(a) && isXRP(b))
-    {
-        XRPAmount const aVal = a.xrp();
-        XRPAmount const bVal = b.xrp();
-
-        return !(
-            (bVal > XRPAmount{0} &&
-             aVal > XRPAmount{std::numeric_limits<XRPAmount::value_type>::max()} - bVal) ||
-            (bVal < XRPAmount{0} &&
-             aVal < XRPAmount{std::numeric_limits<XRPAmount::value_type>::min()} - bVal));
-    }
+        return checkedAdd(a.xrp().drops(), b.xrp().drops()).has_value();
 
     // IOU case (precision check)
     auto const ret = std::visit(
@@ -516,15 +509,7 @@ canAdd(STAmount const& a, STAmount const& b)
 
             // MPT (overflow & underflow check)
             if constexpr (kIsMptissueV<TIss1> && kIsMptissueV<TIss2>)
-            {
-                MPTAmount const aVal = a.mpt();
-                MPTAmount const bVal = b.mpt();
-                return !(
-                    (bVal > MPTAmount{0} &&
-                     aVal > MPTAmount{std::numeric_limits<MPTAmount::value_type>::max()} - bVal) ||
-                    (bVal < MPTAmount{0} &&
-                     aVal < MPTAmount{std::numeric_limits<MPTAmount::value_type>::min()} - bVal));
-            }
+                return checkedAdd(a.mpt().value(), b.mpt().value()).has_value();
             return std::nullopt;
         },
         a.asset().value(),
@@ -575,11 +560,7 @@ canSubtract(STAmount const& a, STAmount const& b)
             return false;
 
         // Check for overflow
-        if (bVal < XRPAmount{0} &&
-            aVal > XRPAmount{std::numeric_limits<XRPAmount::value_type>::max()} + bVal)
-            return false;
-
-        return true;
+        return checkedSub(aVal.drops(), bVal.drops()).has_value();
     }
 
     // IOU case (no underflow)
@@ -602,10 +583,7 @@ canSubtract(STAmount const& a, STAmount const& b)
                     return false;
 
                 // Overflow check
-                if (bVal < MPTAmount{0} &&
-                    aVal > MPTAmount{std::numeric_limits<MPTAmount::value_type>::max()} + bVal)
-                    return false;
-                return true;
+                return checkedSub(aVal.value(), bVal.value()).has_value();
             }
             return std::nullopt;
         },
@@ -1247,6 +1225,19 @@ divide(STAmount const& num, STAmount const& den, Asset const& asset)
     if (num == beast::kZero)
         return {asset};
 
+    // The legacy path below assumes 16-digit mantissas. An MPT mantissa is
+    // the raw 63-bit value and is never scaled down, so an MPT numerator can
+    // overflow the quotient and an MPT denominator shortens it, moving the +5
+    // nudge into a significant digit. Use Number arithmetic under
+    // MPTokensV2 whenever an MPT is involved, as mulRound/divRound do. Pin
+    // the rounding mode so the result does not depend on the caller's.
+    if (isFeatureEnabled(featureMPTokensV2, /*resultIfNoRules*/ true) &&
+        (asset.holds<MPTIssue>() || num.holds<MPTIssue>() || den.holds<MPTIssue>()))
+    {
+        NumberRoundModeGuard const rg(Number::RoundingMode::ToNearest);
+        return STAmount{asset, Number{num} / Number{den}};
+    }
+
     std::uint64_t numVal = num.mantissa();
     std::uint64_t denVal = den.mantissa();
     int numOffset = num.exponent();
@@ -1276,11 +1267,21 @@ divide(STAmount const& num, STAmount const& den, Asset const& asset)
     // numerator by 10^17 (the product is in the range of
     // 10^32 to 10^33) followed by a division, so the result
     // is in the range of 10^16 to 10^15.
-    return STAmount(
-        asset,
-        muldiv(numVal, kTenTO17, denVal) + 5,
-        numOffset - denOffset - 17,
-        num.negative() != den.negative());
+    std::uint64_t quotient = muldiv(numVal, kTenTO17, denVal);
+    int offset = numOffset - denOffset - 17;
+
+    // An integral (XRP) numerator is not scaled down to 16 digits, so the
+    // quotient can land in [2^63, 2^64). The STAmount constructor reads
+    // that as a negative IOU mantissa, and the +5 can wrap. Drop a digit
+    // first; the result is canonicalized to 16 digits anyway.
+    if (quotient > static_cast<std::uint64_t>(std::numeric_limits<std::int64_t>::max()) - 5 &&
+        isFeatureEnabled(featureMPTokensV2, /*resultIfNoRules*/ true))
+    {
+        quotient /= 10;
+        ++offset;
+    }
+
+    return STAmount(asset, quotient + 5, offset, num.negative() != den.negative());
 }
 
 STAmount
@@ -1486,28 +1487,28 @@ roundNumberResult(
     // and for materializing the final integral amount.
     NumberRoundModeGuard const finalRound(roundMode(resultNegative, roundUp));
     auto result = STAmount{asset, number};
+    // An integral result can't underflow: when roundUp is set, roundMode()
+    // above selects Upward, and materializing a Number into an integral
+    // STAmount honors that mode (Number::operator rep()), so any positive
+    // value rounds up to at least 1.
     [[maybe_unused]] bool const nonzeroPositiveRoundUp =
         roundUp && !resultNegative && number != beast::kZero;
     ALWAYS(
-        !nonzeroPositiveRoundUp || result != beast::kZero,
-        "xrpl::roundNumberResult : positive rounded-up MPT result is representable");
+        !nonzeroPositiveRoundUp || !asset.integral() || result != beast::kZero,
+        "xrpl::roundNumberResult : positive rounded-up integral result is representable");
 
     if (roundUp && !resultNegative && !result)
     {
-        // Intended to preserve existing mulRound/divRound behavior for a
-        // positive result too small to represent in the target asset.
-        //
-        // Unreachable in practice: when roundUp is set, roundMode() above
-        // selects Upward, and materializing a Number into an STAmount honors
-        // that mode (Number::operator rep()), so any positive value rounds up
-        // to at least the smallest representable unit. Hence, a positive result
-        // is never !result here; the only zero case is a zero operand, which
-        // the mulRound/divRound callers handle before reaching this function.
-        // LCOV_EXCL_START
+        // Preserve existing mulRound/divRound behavior for a positive result
+        // too small to represent in the target asset. An IOU result with an
+        // MPT operand (e.g. 1 MPT / 1e95) below the smallest IOU is flushed to
+        // zero by IOUAmount normalization regardless of the rounding mode, so
+        // snap it up to the smallest positive IOU. The only zero case for an
+        // integral result is a zero operand, which the mulRound/divRound
+        // callers handle before reaching this function.
         if (asset.integral())
-            return STAmount{asset, 1};
+            return STAmount{asset, 1};  // LCOV_EXCL_LINE
         return STAmount{asset, STAmount::kMinValue, STAmount::kMinOffset, false};
-        // LCOV_EXCL_STOP
     }
 
     return result;
@@ -1556,11 +1557,19 @@ mulRoundImpl(STAmount const& v1, STAmount const& v2, Asset const& asset, bool ro
 
     bool const resultNegative = v1.negative() != v2.negative();
 
-    if (asset.holds<MPTIssue>() && isFeatureEnabled(featureMPTokensV2, false))
+    // The legacy path below assumes 16-digit mantissas. An MPT mantissa is the
+    // raw 63-bit balance, so any MPT operand (not just an MPT result) can
+    // overflow it: a large MPT amount times an IOU-shaped rate into an XRP or
+    // IOU result is the offer-crossing remainder and partial-fill case. Use
+    // Number arithmetic under MPTokensV2 whenever an MPT is involved.
+    //
+    // Outside a transaction (no current rules, e.g. pathfinding) default to
+    // the Number path: an MPT operand can only reach here through MPT
+    // offers or AMMs, which require MPTokensV2, so this keeps RPC quotes on
+    // the same arithmetic as the transaction they describe.
+    if (isFeatureEnabled(featureMPTokensV2, /*resultIfNoRules*/ true) &&
+        (asset.holds<MPTIssue>() || v1.holds<MPTIssue>() || v2.holds<MPTIssue>()))
     {
-        // MPT DEX can combine 63-bit MPT amounts with IOU-shaped transfer
-        // rates. Use Number arithmetic under MPTokensV2 so the rounded
-        // operation is not limited by the legacy uint64_t scaled mantissa.
         Number result;
         {
             NumberRoundModeGuard const operationRound(roundMode(resultNegative, roundUp));
@@ -1658,9 +1667,12 @@ divRoundImpl(STAmount const& num, STAmount const& den, Asset const& asset, bool
 
     bool const resultNegative = (num.negative() != den.negative());
 
+    // See mulRoundImpl: any MPT operand, not just an MPT result, and the
+    // Number path when there are no current rules.
     // fixCleanup3_5_0: the legacy path below overflows on large MPT amounts.
-    if (asset.holds<MPTIssue>() &&
-        (isFeatureEnabled(featureMPTokensV2, true) || isFeatureEnabled(fixCleanup3_5_0, true)))
+    auto const enabled = isFeatureEnabled(featureMPTokensV2, /*resultIfNoRules*/ true) ||
+        isFeatureEnabled(fixCleanup3_5_0, /*resultIfNoRules*/ true);
+    if ((asset.holds<MPTIssue>() || num.holds<MPTIssue>() || den.holds<MPTIssue>()) && enabled)
     {
         // Match the multiply path above: Number performs the rounded
         // operation, then STAmount materializes the final MPT amount using the
@@ -1751,6 +1763,24 @@ divRoundStrict(STAmount const& num, STAmount const& den, Asset const& asset, boo
     return divRoundImpl<NumberRoundModeGuard>(num, den, asset, roundUp);
 }
 
+STAmount
+mulRatio(STAmount const& amt, std::uint32_t num, std::uint32_t den, Number::RoundingMode rounding)
+{
+    XRPL_ASSERT(
+        rounding == Number::RoundingMode::Upward || rounding == Number::RoundingMode::Downward,
+        "xrpl::mulRatio(STAmount) : rounding is Upward or Downward");
+    bool const roundUp = rounding == Number::RoundingMode::Upward;
+    return amt.asset().visit(
+        [&](Issue const& issue) -> STAmount {
+            if (amt.native())
+                return mulRatio(amt.xrp(), num, den, roundUp);
+            return {mulRatio(amt.iou(), num, den, roundUp), issue};
+        },
+        [&](MPTIssue const& issue) -> STAmount {
+            return {mulRatio(amt.mpt(), num, den, roundUp), issue};
+        });
+}
+
 [[nodiscard]] bool
 STAmount::isZeroAtScale(int scale) const
 {

src/libxrpl/protocol/TER.cpp

@@ -228,6 +228,7 @@ transResults()
         MAKE_ERROR(terNO_DELEGATE_PERMISSION, "Delegated account lacks permission to perform this transaction."),
         MAKE_ERROR(terLOCKED,                 "Fund is locked."),
         MAKE_ERROR(terNO_PERMISSION,          "No permission to perform requested operation."),
+        MAKE_ERROR(terTICKET_RESERVED,        "Ticket is reserved."),
 
         MAKE_ERROR(tesSUCCESS,                "The transaction was applied. Only final in a validated ledger."),
     };

src/libxrpl/protocol/XRPAmount.cpp

@@ -0,0 +1,54 @@
+#include <xrpl/protocol/XRPAmount.h>
+
+#include <xrpl/basics/MathUtilities.h>
+#include <xrpl/basics/contract.h>
+#include <xrpl/protocol/Feature.h>
+#include <xrpl/protocol/Rules.h>
+
+#include <stdexcept>
+
+namespace xrpl {
+
+XRPAmount&
+XRPAmount::operator+=(value_type const& rhs)
+{
+    if (auto const result = checkedAdd(drops_, rhs))
+    {
+        drops_ = *result;
+        return *this;
+    }
+    if (isFeatureEnabled(fixCleanup3_5_0, /*resultIfNoRules*/ true))
+        Throw<std::overflow_error>("XRPAmount::operator+= overflow");
+    drops_ += rhs;
+    return *this;
+}
+
+XRPAmount&
+XRPAmount::operator-=(value_type const& rhs)
+{
+    if (auto const result = checkedSub(drops_, rhs))
+    {
+        drops_ = *result;
+        return *this;
+    }
+    if (isFeatureEnabled(fixCleanup3_5_0, /*resultIfNoRules*/ true))
+        Throw<std::overflow_error>("XRPAmount::operator-= overflow");
+    drops_ -= rhs;
+    return *this;
+}
+
+XRPAmount&
+XRPAmount::operator*=(value_type const& rhs)
+{
+    if (auto const result = checkedMul(drops_, rhs))
+    {
+        drops_ = *result;
+        return *this;
+    }
+    if (isFeatureEnabled(fixCleanup3_5_0, /*resultIfNoRules*/ true))
+        Throw<std::overflow_error>("XRPAmount::operator*= overflow");
+    drops_ *= rhs;
+    return *this;
+}
+
+}  // namespace xrpl

src/libxrpl/shamap/SHAMap.cpp

@@ -26,6 +26,7 @@
 
 #include <boost/smart_ptr/intrusive_ptr.hpp>
 
+#include <atomic>
 #include <cstdint>
 #include <exception>
 #include <functional>
@@ -77,14 +78,23 @@ SHAMap::SHAMap(SHAMap const& other, bool isMutable)
     : f_(other.f_)
     , journal_(other.f_.journal())
     , cowid_(other.cowid_ + 1)
-    , ledgerSeq_(other.ledgerSeq_)
+    , ledgerSeq_(other.ledgerSeq())
     , root_(other.root_)
-    , state_(isMutable ? SHAMapState::Modifying : SHAMapState::Immutable)
     , type_(other.type_)
     , backed_(other.backed_)
 {
+    // A snapshot shares the source's root, so Invalid carries over. Read once into a local, since
+    // the source's state can change while this runs.
+    auto const otherState = other.state();
+    auto const ownState = [&] {
+        if (otherState == SHAMapState::Invalid)
+            return SHAMapState::Invalid;
+        return isMutable ? SHAMapState::Modifying : SHAMapState::Immutable;
+    }();
+    state_.store(ownState, std::memory_order_release);
+
     // If either map may change, they cannot share nodes
-    if ((state_ != SHAMapState::Immutable) || (other.state_ != SHAMapState::Immutable))
+    if ((ownState != SHAMapState::Immutable) || (otherState != SHAMapState::Immutable))
     {
         unshare();
     }
@@ -96,6 +106,18 @@ SHAMap::snapShot(bool isMutable) const
     return std::make_shared<SHAMap>(*this, isMutable);
 }
 
+void
+SHAMap::condemn(SHAMapTreeNode const& node, SHAMapHash const& hash, SHAMapNodeID const& position)
+    const
+{
+    // journal_ is shared by every map built from one Family, so name which map this is. The root
+    // node's own hash, since getHash() unshares the tree on a zero hash.
+    JLOG(journal_.warn()) << (node.isLeaf() ? "Leaf " : "Inner node ") << hash << " cannot sit at "
+                          << position << ", so the map with root hash " << root_->getHash()
+                          << " is invalid";
+    setInvalid();
+}
+
 void
 SHAMap::dirtyUp(NodePathStack& stack, UInt256 const& target, SHAMapTreeNodePtr child)
 {
@@ -105,20 +127,25 @@ SHAMap::dirtyUp(NodePathStack& stack, UInt256 const& target, SHAMapTreeNodePtr c
     // child can be an inner node or a leaf
 
     XRPL_ASSERT(
-        (state_ != SHAMapState::Synching) && (state_ != SHAMapState::Immutable),
+        (state() != SHAMapState::Synching) && (state() != SHAMapState::Immutable),
         "xrpl::SHAMap::dirtyUp : valid state");
     XRPL_ASSERT(child && (child->cowid() == cowid_), "xrpl::SHAMap::dirtyUp : valid child input");
 
     while (!stack.empty())
     {
-        auto node = intr_ptr::dynamicPointerCast<SHAMapInnerNode>(stack.top().first);
-        SHAMapNodeID const nodeID = stack.top().second;
-        stack.pop();
-        XRPL_ASSERT(node, "xrpl::SHAMap::dirtyUp : non-null node");
+        auto const depth = stack.topDepth();
+        auto node = stack.releaseNodeAs<SHAMapInnerNode>();
+        if (!node)
+        {
+            // LCOV_EXCL_START
+            UNREACHABLE("xrpl::SHAMap::dirtyUp : node is not inner");
+            Throw<SHAMapMissingNode>(type_, target);
+            // LCOV_EXCL_STOP
+        }
 
-        auto const branch = selectBranch(nodeID, target);
+        auto const branch = selectBranch(depth, target);
 
-        node = unshareNode(std::move(node), nodeID);
+        node = unshareNode(std::move(node), depth);
         node->setChild(branch, std::move(child));
 
         child = std::move(node);
@@ -128,32 +155,62 @@ SHAMap::dirtyUp(NodePathStack& stack, UInt256 const& target, SHAMapTreeNodePtr c
 SHAMapLeafNode*
 SHAMap::walkTowardsKey(UInt256 const& id, NodePathStack* stack) const
 {
-    XRPL_ASSERT(
-        stack == nullptr || stack->empty(), "xrpl::SHAMap::walkTowardsKey : empty stack input");
-    auto inNode = root_;
-    SHAMapNodeID nodeID;
+    if (stack != nullptr && !stack->empty())
+    {
+        // The path must start at the root, so a non-empty one is cleared rather than appended to.
+        // LCOV_EXCL_START
+        UNREACHABLE("xrpl::SHAMap::walkTowardsKey : non-empty stack input");
+        stack->clear();
+        return nullptr;
+        // LCOV_EXCL_STOP
+    }
 
-    // Every node on this walk lies on the path to `id`, so the stack can derive each ID from the
-    // branch `id` selects at the node above it.
-    auto const pushCurrent = [&] {
-        if (stack != nullptr)
-            stack->pushNode(inNode, id);
+    auto inNode = root_;
+    unsigned int noStackDepth = 0;
+
+    // Returns false when the path could not be extended, which is separate from `id` being absent
+    // (see pushChild). The path is cleared, so a caller reads an empty path as a refusal.
+    auto const pushCurrent = [&] -> bool {
+        if (stack == nullptr || stack->pushNode(inNode, id))
+        {
+            return true;
+        }
+        stack->clear();
+        return false;
     };
 
     while (inNode->isInner())
     {
-        pushCurrent();
+        if (!pushCurrent())
+        {
+            return nullptr;
+        }
 
         auto& inner = safeDowncast<SHAMapInnerNode&>(*inNode);
-        auto const branch = selectBranch(nodeID, id);
+        auto const depth = stack != nullptr ? stack->topDepth() : noStackDepth;
+        auto const branch = selectBranch(depth, id);
         if (inner.isEmptyBranch(branch))
             return nullptr;
 
         inNode = descendThrow(inner, branch);
-        nodeID = nodeID.getChildNodeID(branch);
+        if (stack == nullptr)
+        {
+            // The same depth bound pushChild applies, so both modes refuse at the same depth. A
+            // node resolved from the local store still has its position and type to be judged.
+            bool const tooDeep = pastLeafDepth(depth, *inNode);
+            SOMETIMES(tooDeep, "xrpl::SHAMap::walkTowardsKey : child too deep");
+            if (tooDeep)
+            {
+                return nullptr;
+            }
+            ++noStackDepth;
+        }
     }
 
-    pushCurrent();
+    if (!pushCurrent())
+    {
+        return nullptr;
+    }
     return safeDowncast<SHAMapLeafNode*>(inNode.get());
 }
 
@@ -170,7 +227,7 @@ SHAMapTreeNodePtr
 SHAMap::fetchNodeFromDB(SHAMapHash const& hash) const
 {
     XRPL_ASSERT(backed_, "xrpl::SHAMap::fetchNodeFromDB : is backed");
-    auto const obj = f_.db().fetchNodeObject(hash.asUInt256(), ledgerSeq_);
+    auto const obj = f_.db().fetchNodeObject(hash.asUInt256(), ledgerSeq());
     return finishFetch(hash, obj);
 }
 
@@ -183,10 +240,17 @@ SHAMap::finishFetch(SHAMapHash const& hash, std::shared_ptr<NodeObject> const& o
     {
         if (!object)
         {
-            if (full_)
+            // A missing node disproves full_, so withdraw it and report the gap. The exchange
+            // makes exactly one reader report it, and its acquire pairs with the release store in
+            // setFull(). It needs no release: the only other reader of full_ is this same path,
+            // and a reader that loses the exchange does nothing with what the winner did. The load
+            // ahead of it is relaxed, since all it decides is whether to try the exchange: a stale
+            // true costs one exchange that loses, and a stale false means another reader won, or
+            // setFull() is not visible yet and the gap goes unreported.
+            if (full_.load(std::memory_order_relaxed) &&
+                full_.exchange(false, std::memory_order_acquire))
             {
-                full_ = false;
-                f_.missingNodeAcquireBySeq(ledgerSeq_, hash.asUInt256());
+                f_.missingNodeAcquireBySeq(ledgerSeq(), hash.asUInt256());
             }
             return {};
         }
@@ -219,7 +283,7 @@ SHAMap::checkFilter(SHAMapHash const& hash, SHAMapSyncFilter const* filter) cons
             auto node = SHAMapTreeNode::makeFromPrefix(makeSlice(*nodeData), hash);
             if (node)
             {
-                filter->gotNode(true, hash, ledgerSeq_, std::move(*nodeData), node->getType());
+                filter->gotNode(true, hash, ledgerSeq(), std::move(*nodeData), node->getType());
                 if (backed_)
                     canonicalize(hash, node);
             }
@@ -357,12 +421,23 @@ SHAMap::descend(
         !parent->isEmptyBranch(branch), "xrpl::SHAMap::descend : parent branch is non-empty");
 
     SHAMapTreeNode* child = parent->getChildPointer(branch);  // NOLINT(misc-const-correctness)
+    auto const childID = parentID.getChildNodeID(branch);
 
     if (child == nullptr)
     {
         auto const& childHash = parent->getChildHash(branch);
         SHAMapTreeNodePtr childNode = fetchNodeNT(childHash, filter);
 
+        if (childNode &&
+            (!belongsAt(childID, *childNode) || pastLeafDepth(parentID.getDepth(), *childNode)))
+        {
+            // A hash covers a node's contents, not its position, so position is judged before
+            // canonicalizeChild hooks the node in. The verdict lands on the map, since resolving
+            // the same blob again gives the same node.
+            condemn(*childNode, childHash, childID);
+            return std::make_pair(nullptr, childID);
+        }
+
         if (childNode)
         {
             childNode = parent->canonicalizeChild(branch, std::move(childNode));
@@ -370,7 +445,7 @@ SHAMap::descend(
         }
     }
 
-    return std::make_pair(child, parentID.getChildNodeID(branch));
+    return std::make_pair(child, childID);
 }
 
 SHAMapTreeNode*
@@ -399,7 +474,7 @@ SHAMap::descendAsync(
         {
             f_.db().asyncFetch(
                 hash.asUInt256(),
-                ledgerSeq_,
+                ledgerSeq(),
                 [this, hash, cb{std::move(callback)}](std::shared_ptr<NodeObject> const& object) {
                     auto const node = finishFetch(hash, object);
                     cb(node, hash);
@@ -417,16 +492,16 @@ SHAMap::descendAsync(
 
 template <class Node>
 intr_ptr::SharedPtr<Node>
-SHAMap::unshareNode(intr_ptr::SharedPtr<Node> node, SHAMapNodeID const& nodeID)
+SHAMap::unshareNode(intr_ptr::SharedPtr<Node> node, unsigned int depth)
 {
     // make sure the node is suitable for the intended operation (copy on write)
     XRPL_ASSERT(node->cowid() <= cowid_, "xrpl::SHAMap::unshareNode : node valid for cowid");
     if (node->cowid() != cowid_)
     {
         // have a CoW
-        XRPL_ASSERT(state_ != SHAMapState::Immutable, "xrpl::SHAMap::unshareNode : not immutable");
+        XRPL_ASSERT(state() != SHAMapState::Immutable, "xrpl::SHAMap::unshareNode : not immutable");
         node = intr_ptr::staticPointerCast<Node>(node->clone(cowid_));
-        if (nodeID.isRoot())
+        if (depth == 0)
             root_ = node;
     }
     return node;
@@ -436,14 +511,19 @@ SHAMapLeafNode*
 SHAMap::belowHelper(NodePathStack& stack, BelowDirection direction) const
 {
     XRPL_ASSERT(!stack.empty(), "xrpl::SHAMap::belowHelper : non-empty stack input");
-    if (auto const& top = stack.top().first; top->isLeaf())
+    if (stack.empty())
+    {
+        // LCOV_EXCL_START
+        return nullptr;
+        // LCOV_EXCL_STOP
+    }
+    if (auto const& top = stack.top(); top->isLeaf())
         return safeDowncast<SHAMapLeafNode*>(top.get());
 
-    // The stack owns the node/ID pairing, so descending is only ever "push the branch we took".
-    // `scanned` counts how many branches of the current node we have examined; the branch we look
-    // at is derived from it, so no index ever goes out of range. `inner` tracks the node on top of
-    // the stack, which keeps it alive, so it only needs recomputing after a push.
-    auto* inner = safeDowncast<SHAMapInnerNode*>(stack.top().first.get());
+    // `scanned` counts the branches of the current node already examined, and the branch looked at
+    // is derived from it, so the index stays inside the fan-out. `inner` points at the top of the
+    // path, which keeps it alive, so it only needs recomputing after a push.
+    auto* inner = safeDowncast<SHAMapInnerNode*>(stack.top().get());
     for (auto scanned = 0u; scanned < kBranchFactor;)
     {
         auto const childBranch =
@@ -455,9 +535,20 @@ SHAMap::belowHelper(NodePathStack& stack, BelowDirection direction) const
             continue;
         }
 
-        stack.pushChild(descendThrow(*inner, childBranch), childBranch);
+        auto const parentDepth = stack.topDepth();
+        auto descended = descendThrow(*inner, childBranch);
+        if (!stack.pushChild(std::move(descended), childBranch))
+        {
+            // Throwing rather than returning nullptr keeps nullptr meaning a subtree with no leaf
+            // below it, which begin() and an iterator increment both rely on. Every caller here is
+            // a const read on a shared snapshot, so the verdict is left to the acquisition path
+            // (see SHAMap::descend and gmnProcessNodes).
+            JLOG(journal_.warn()) << "Cannot walk below depth " << parentDepth << " at branch "
+                                  << childBranch;
+            Throw<SHAMapMissingNode>(type_, inner->getChildHash(childBranch));
+        }
 
-        auto const& child = stack.top().first;
+        auto const& child = stack.top();
         if (child->isLeaf())
             return safeDowncast<SHAMapLeafNode*>(child.get());
 
@@ -512,7 +603,12 @@ SHAMapLeafNode const*
 SHAMap::peekFirstItem(NodePathStack& stack) const
 {
     XRPL_ASSERT(stack.empty(), "xrpl::SHAMap::peekFirstItem : empty stack input");
-    stack.pushRoot(root_);
+    if (!stack.pushRoot(root_))
+    {
+        // LCOV_EXCL_START
+        return nullptr;
+        // LCOV_EXCL_STOP
+    }
     SHAMapLeafNode const* node = belowHelper(stack, BelowDirection::First);
     if (node == nullptr)
     {
@@ -526,18 +622,28 @@ SHAMapLeafNode const*
 SHAMap::peekNextItem(UInt256 const& id, NodePathStack& stack) const
 {
     XRPL_ASSERT(!stack.empty(), "xrpl::SHAMap::peekNextItem : non-empty stack input");
-    XRPL_ASSERT(stack.top().first->isLeaf(), "xrpl::SHAMap::peekNextItem : stack starts with leaf");
+    if (stack.empty())
+    {
+        // LCOV_EXCL_START
+        return nullptr;
+        // LCOV_EXCL_STOP
+    }
+    XRPL_ASSERT(stack.top()->isLeaf(), "xrpl::SHAMap::peekNextItem : stack starts with leaf");
     stack.pop();
     while (!stack.empty())
     {
-        auto const [node, nodeID] = stack.top();
+        auto const& node = stack.top();
         XRPL_ASSERT(!node->isLeaf(), "xrpl::SHAMap::peekNextItem : another node is not leaf");
         auto& inner = safeDowncast<SHAMapInnerNode&>(*node);
-        for (auto i = selectBranch(nodeID, id) + 1; i < kBranchFactor; ++i)
+        for (auto i = selectBranch(stack.topDepth(), id) + 1; i < kBranchFactor; ++i)
         {
             if (!inner.isEmptyBranch(i))
             {
-                stack.pushChild(descendThrow(inner, i), i);
+                auto child = descendThrow(inner, i);
+                if (!stack.pushChild(std::move(child), i))
+                {
+                    Throw<SHAMapMissingNode>(type_, id);
+                }
                 auto leaf = belowHelper(stack, BelowDirection::First);
                 if (leaf == nullptr)
                     Throw<SHAMapMissingNode>(type_, id);
@@ -581,9 +687,15 @@ SHAMap::boundHelper(UInt256 const& id, BelowDirection direction) const
 
     NodePathStack stack;
     walkTowardsKey(id, &stack);
+
+    // An empty path means the walk refused a node. An empty map still leaves its root on the path,
+    // and end() would claim no key lies on the requested side of `id`, so a refusal throws.
+    if (stack.empty())
+        Throw<SHAMapMissingNode>(type_, id);
+
     while (!stack.empty())
     {
-        auto const [node, nodeID] = stack.top();
+        auto const& node = stack.top();
         if (node->isLeaf())
         {
             auto const& item = safeDowncast<SHAMapLeafNode const&>(*node).peekItem();
@@ -593,7 +705,7 @@ SHAMap::boundHelper(UInt256 const& id, BelowDirection direction) const
         else
         {
             auto& inner = safeDowncast<SHAMapInnerNode&>(*node);
-            auto const taken = selectBranch(nodeID, id);
+            auto const taken = selectBranch(stack.topDepth(), id);
             auto const remaining = searchingForward ? (kBranchFactor - 1u - taken) : taken;
 
             for (auto scanned = 0u; scanned < remaining; ++scanned)
@@ -603,7 +715,11 @@ SHAMap::boundHelper(UInt256 const& id, BelowDirection direction) const
                 if (inner.isEmptyBranch(branch))
                     continue;
 
-                stack.pushChild(descendThrow(inner, branch), branch);
+                auto child = descendThrow(inner, branch);
+                if (!stack.pushChild(std::move(child), branch))
+                {
+                    Throw<SHAMapMissingNode>(type_, id);
+                }
                 auto const leaf = belowHelper(stack, direction);
                 if (leaf == nullptr)
                     Throw<SHAMapMissingNode>(type_, id);
@@ -637,7 +753,7 @@ bool
 SHAMap::delItem(UInt256 const& id)
 {
     // delete the item with this ID
-    XRPL_ASSERT(state_ != SHAMapState::Immutable, "xrpl::SHAMap::delItem : not immutable");
+    XRPL_ASSERT(state() != SHAMapState::Immutable, "xrpl::SHAMap::delItem : not immutable");
 
     NodePathStack stack;
     walkTowardsKey(id, &stack);
@@ -645,10 +761,12 @@ SHAMap::delItem(UInt256 const& id)
     if (stack.empty())
         Throw<SHAMapMissingNode>(type_, id);
 
-    auto const leaf = intr_ptr::dynamicPointerCast<SHAMapLeafNode>(stack.top().first);
-    stack.pop();
+    // An absent id leaves an inner node on top, which is the "not found" answer.
+    auto const leaf = stack.releaseNodeAs<SHAMapLeafNode>();
+    if (!leaf)
+        return false;
 
-    if (!leaf || (leaf->peekItem()->key() != id))
+    if (leaf->peekItem()->key() != id)
         return false;
 
     SHAMapNodeType const type = leaf->getType();
@@ -658,19 +776,25 @@ SHAMap::delItem(UInt256 const& id)
 
     while (!stack.empty())
     {
-        auto node = intr_ptr::staticPointerCast<SHAMapInnerNode>(stack.top().first);
-        SHAMapNodeID const nodeID = stack.top().second;
-        stack.pop();
+        auto const depth = stack.topDepth();
+        auto node = stack.releaseNodeAs<SHAMapInnerNode>();
+        if (!node)
+        {
+            // LCOV_EXCL_START
+            UNREACHABLE("xrpl::SHAMap::delItem : node is not inner");
+            Throw<SHAMapMissingNode>(type_, id);
+            // LCOV_EXCL_STOP
+        }
 
-        node = unshareNode(std::move(node), nodeID);
+        node = unshareNode(std::move(node), depth);
         node->setChild(
-            selectBranch(nodeID, id), std::move(prevNode));  // NOLINT(bugprone-use-after-move)
+            selectBranch(depth, id), std::move(prevNode));  // NOLINT(bugprone-use-after-move)
 
         XRPL_ASSERT(
             not prevNode,  // NOLINT(bugprone-use-after-move)
             "xrpl::SHAMap::delItem : prevNode should be nullptr after std::move");
 
-        if (!nodeID.isRoot())
+        if (depth != 0)
         {
             // we may have made this a node with 1 or 0 children
             // And, if so, we need to remove this branch
@@ -719,7 +843,7 @@ SHAMap::delItem(UInt256 const& id)
 bool
 SHAMap::addGiveItem(SHAMapNodeType type, boost::intrusive_ptr<SHAMapItem const> item)
 {
-    XRPL_ASSERT(state_ != SHAMapState::Immutable, "xrpl::SHAMap::addGiveItem : not immutable");
+    XRPL_ASSERT(state() != SHAMapState::Immutable, "xrpl::SHAMap::addGiveItem : not immutable");
     XRPL_ASSERT(type != SHAMapNodeType::TnInner, "xrpl::SHAMap::addGiveItem : valid type input");
 
     // add the specified item, does not update
@@ -731,8 +855,8 @@ SHAMap::addGiveItem(SHAMapNodeType type, boost::intrusive_ptr<SHAMapItem const>
     if (stack.empty())
         Throw<SHAMapMissingNode>(type_, tag);
 
-    auto [node, nodeID] = stack.top();
-    stack.pop();
+    auto depth = stack.topDepth();
+    auto node = stack.releaseNode();
 
     if (node->isLeaf())
     {
@@ -740,12 +864,12 @@ SHAMap::addGiveItem(SHAMapNodeType type, boost::intrusive_ptr<SHAMapItem const>
         if (leaf->peekItem()->key() == tag)
             return false;
     }
-    node = unshareNode(std::move(node), nodeID);
+    node = unshareNode(std::move(node), depth);
     if (node->isInner())
     {
         // easy case, we end on an inner node
         auto const inner = intr_ptr::staticPointerCast<SHAMapInnerNode>(node);
-        auto const branch = selectBranch(nodeID, tag);
+        auto const branch = selectBranch(depth, tag);
         XRPL_ASSERT(
             inner->isEmptyBranch(branch), "xrpl::SHAMap::addGiveItem : inner branch is empty");
         inner->setChild(branch, makeTypedLeaf(type, std::move(item), cowid_));
@@ -763,13 +887,20 @@ SHAMap::addGiveItem(SHAMapNodeType type, boost::intrusive_ptr<SHAMapItem const>
 
         auto b1 = 0u, b2 = 0u;
 
-        while ((b1 = selectBranch(nodeID, tag)) == (b2 = selectBranch(nodeID, otherItem->key())))
+        while ((b1 = selectBranch(depth, tag)) == (b2 = selectBranch(depth, otherItem->key())))
         {
-            stack.pushNode(node, tag);
+            if (!stack.pushNode(node, tag))
+            {
+                // The loop advances only while the two keys agree at the current nibble, and keys
+                // agreeing at every nibble are equal, which returned false above.
+                // LCOV_EXCL_START
+                Throw<SHAMapMissingNode>(type_, tag);
+                // LCOV_EXCL_STOP
+            }
 
             // we need a new inner node, since both go on same branch at this
             // level
-            nodeID = nodeID.getChildNodeID(b1);
+            ++depth;
             node = intr_ptr::makeShared<SHAMapInnerNode>(cowid_);
         }
 
@@ -810,7 +941,7 @@ SHAMap::updateGiveItem(SHAMapNodeType type, boost::intrusive_ptr<SHAMapItem cons
     // can't change the tag but can change the hash
     UInt256 const tag = item->key();
 
-    XRPL_ASSERT(state_ != SHAMapState::Immutable, "xrpl::SHAMap::updateGiveItem : not immutable");
+    XRPL_ASSERT(state() != SHAMapState::Immutable, "xrpl::SHAMap::updateGiveItem : not immutable");
 
     NodePathStack stack;
     walkTowardsKey(tag, &stack);
@@ -818,16 +949,19 @@ SHAMap::updateGiveItem(SHAMapNodeType type, boost::intrusive_ptr<SHAMapItem cons
     if (stack.empty())
         Throw<SHAMapMissingNode>(type_, tag);
 
-    auto node = intr_ptr::dynamicPointerCast<SHAMapLeafNode>(stack.top().first);
-    auto const nodeID = stack.top().second;
-    stack.pop();
+    auto const depth = stack.topDepth();
 
-    if (!node || (node->peekItem()->key() != tag))
+    // A tag absent from the map leaves an inner node on top, which the API permits.
+    auto node = stack.releaseNodeAs<SHAMapLeafNode>();
+    if (!node)
+    {
+        return false;
+    }
+
+    // Or the walk ended on a leaf holding some other key.
+    if (node->peekItem()->key() != tag)
     {
-        // LCOV_EXCL_START
-        UNREACHABLE("xrpl::SHAMap::updateGiveItem : invalid node");
         return false;
-        // LCOV_EXCL_STOP
     }
 
     if (node->getType() != type)
@@ -836,7 +970,7 @@ SHAMap::updateGiveItem(SHAMapNodeType type, boost::intrusive_ptr<SHAMapItem cons
         return false;
     }
 
-    node = unshareNode(std::move(node), nodeID);
+    node = unshareNode(std::move(node), depth);
 
     if (node->setItem(item))
         dirtyUp(stack, tag, node);
@@ -901,7 +1035,7 @@ SHAMap::writeNode(NodeObjectType t, SHAMapTreeNodePtr node) const
 
     Serializer s;
     node->serializeWithPrefix(s);
-    f_.db().store(t, std::move(s.modData()), node->getHash().asUInt256(), ledgerSeq_);
+    f_.db().store(t, std::move(s.modData()), node->getHash().asUInt256(), ledgerSeq());
     return node;
 }
 

src/libxrpl/shamap/SHAMapInnerNode.cpp

@@ -16,6 +16,7 @@
 #include <xrpl/shamap/detail/TaggedPointer.h>
 #include <xrpl/shamap/detail/TaggedPointer.ipp>
 
+#include <atomic>
 #include <cstddef>
 #include <cstdint>
 #include <mutex>
@@ -77,7 +78,9 @@ SHAMapInnerNode::clone(std::uint32_t cowid) const
     auto p = intr_ptr::makeShared<SHAMapInnerNode>(cowid, branchCount);
     p->hash_ = hash_;
     p->isBranch_ = isBranch_;
-    p->fullBelowGen_ = fullBelowGen_;
+    // Relaxed, as everywhere. p is not reachable by another thread until this returns.
+    p->fullBelowGen_.store(
+        fullBelowGen_.load(std::memory_order_relaxed), std::memory_order_relaxed);
     SHAMapHash* cloneHashes = nullptr;
     SHAMapHash* thisHashes = nullptr;
     SHAMapTreeNodePtr* cloneChildren = nullptr;

src/libxrpl/shamap/SHAMapNodeID.cpp

@@ -50,14 +50,31 @@ maskedToDepth(UInt256 const& key, unsigned int depth)
     return key & depthMask(depth);
 }
 
-// Whether `id` at `depth` is what `key` looks like once masked down to that depth, i.e.
-// whether an ID with this depth and id names a subtree that `key` falls under.
+// Whether `key` masked to `depth` equals `id`. Asymmetric: `id` is not masked, so this also
+// refuses an id carrying bits below its own depth.
 static bool
 isPrefixOfAtDepth(UInt256 const& id, unsigned int depth, UInt256 const& key)
 {
     return maskedToDepth(key, depth) == id;
 }
 
+bool
+samePositionAtDepth(unsigned int depth, UInt256 const& lhs, UInt256 const& rhs)
+{
+    // The mask is chosen here, so an out-of-range depth would index depthMask's table past its
+    // last entry. kLeafDepth itself is in range, unlike in selectBranch: the position at the leaf
+    // depth is the whole key. A public helper has to hold its own bound.
+    if (depth > SHAMap::kLeafDepth)
+    {
+        // LCOV_EXCL_START
+        UNREACHABLE("xrpl::samePositionAtDepth : depth within tree");
+        depth = SHAMap::kLeafDepth;
+        // LCOV_EXCL_STOP
+    }
+
+    return maskedToDepth(lhs, depth) == maskedToDepth(rhs, depth);
+}
+
 // canonicalize the hash to a node ID for this depth
 SHAMapNodeID::SHAMapNodeID(unsigned int depth, UInt256 const& hash) : id_(hash), depth_(depth)
 {
@@ -90,6 +107,31 @@ SHAMapNodeID::getRawString() const
     return s.getString();
 }
 
+[[nodiscard]] UInt256
+childNodeID(UInt256 const& parentID, unsigned int parentDepth, unsigned int branch)
+{
+    XRPL_ASSERT(branch < SHAMap::kBranchFactor, "xrpl::childNodeID : valid branch input");
+    XRPL_ASSERT(parentDepth < SHAMap::kLeafDepth, "xrpl::childNodeID : parent above leaf depth");
+
+    // Only a depth below kLeafDepth names a child nibble, so clamp to the last one that does.
+    auto const clamped = std::min(parentDepth, SHAMap::kLeafDepth - 1u);
+
+    // The nibble is cleared before the branch is written, so an id already carrying one there is
+    // overwritten rather than merged. The byte index and both nibble choices read `clamped`, so
+    // they cannot disagree.
+    UInt256 id = parentID;
+    auto& byte = *(id.begin() + (clamped / 2));
+    if ((clamped & 1) != 0u)
+    {
+        byte = static_cast<unsigned char>((byte & 0xF0u) | branch);
+    }
+    else
+    {
+        byte = static_cast<unsigned char>((byte & 0x0Fu) | (branch << 4));
+    }
+    return id;
+}
+
 SHAMapNodeID
 SHAMapNodeID::getChildNodeID(unsigned int branch) const
 {
@@ -107,15 +149,13 @@ SHAMapNodeID::getChildNodeID(unsigned int branch) const
     XRPL_ASSERT(
         depth_ <= SHAMap::kLeafDepth, "xrpl::SHAMapNodeID::getChildNodeID : maximum leaf depth");
 
-    if (depth_ >= SHAMap::kLeafDepth)
+    if (SHAMap::isLeafDepth(depth_))
         Throw<std::logic_error>(std::format("Request for child node ID of {}", to_string(*this)));
 
     if (!isPrefixOf(id_))
         Throw<std::logic_error>(std::format("Incorrect mask for {}", to_string(*this)));
 
-    SHAMapNodeID node{depth_ + 1, id_};
-    node.id_.begin()[depth_ / 2] |= ((depth_ & 1) != 0u) ? branch : (branch << 4);
-    return node;
+    return SHAMapNodeID{depth_ + 1, childNodeID(id_, depth_, branch)};
 }
 
 bool
@@ -145,16 +185,16 @@ deserializeSHAMapNodeID(void const* data, std::size_t size)
 }
 
 [[nodiscard]] unsigned int
-selectBranch(SHAMapNodeID const& id, UInt256 const& hash)
+selectBranch(unsigned int depth, UInt256 const& hash)
 {
-    XRPL_ASSERT(id.getDepth() < SHAMap::kLeafDepth, "xrpl::selectBranch : depth below leaf depth");
+    XRPL_ASSERT(depth < SHAMap::kLeafDepth, "xrpl::selectBranch : depth below leaf depth");
 
-    // A depth-64 ID has no nibble left to select. Callers must not ask, but clamp anyway to keep
-    // the read below the end of the 32-byte key.
-    auto const depth = std::min(id.getDepth(), SHAMap::kLeafDepth - 1u);
-    auto branch = static_cast<unsigned int>(*(hash.begin() + (depth / 2)));
+    // Only a depth below kLeafDepth has a nibble to select, so clamp to the last one that does.
+    auto const clamped = std::min(depth, SHAMap::kLeafDepth - 1u);
+    auto branch = static_cast<unsigned int>(*(hash.begin() + (clamped / 2)));
 
-    if ((depth & 1) != 0u)
+    // The byte index and the nibble choice both read `clamped`, so they cannot disagree.
+    if ((clamped & 1) != 0u)
     {
         branch &= 0xf;
     }

src/libxrpl/shamap/SHAMapSync.cpp

@@ -143,13 +143,10 @@ SHAMap::visitDifferences(
         if (!function(*node))
             return;
 
-        // Nibbles run out at kLeafDepth, so only a leaf belongs there. A well-formed map never
-        // holds an inner node at that depth: addKnownNode marks the map invalid rather than hooking
-        // one in, and fetch-pack data is hash-verified against a validated root, so reaching this
-        // means a defect or a corrupt store, not something a peer can provoke. Report the node
-        // anyway - the wire form carries no depth, and the recipient hooks blobs in by hash - but
-        // skip the children rather than letting getChildNodeID throw on them.
-        if (nodeID.getDepth() >= kLeafDepth)
+        // Only a leaf belongs at kLeafDepth. The node is still reported, since the wire form
+        // carries no depth and the recipient hooks blobs by hash. Its children are skipped, since
+        // getChildNodeID has no answer past kLeafDepth.
+        if (isLeafDepth(nodeID.getDepth()))
         {
             // LCOV_EXCL_START
             UNREACHABLE("xrpl::SHAMap::visitDifferences : inner node at leaf depth");
@@ -207,7 +204,12 @@ SHAMap::gmnProcessNodes(MissingNodes& mn, MissingNodes::StackEntry& se)
             // we already know this child node is missing
             fullBelow = false;
         }
-        else if (!backed_ || !f_.getFullBelowCache()->touchIfExists(childHash.asUInt256()))
+        // The cache key carries the child's position beside its hash, so a hit answers for this
+        // child at this position and no other. The depth test runs first, so a child at kLeafDepth
+        // is judged by the arm below rather than answered from the cache: only a leaf sits there.
+        else if (
+            !backed_ || isLeafDepth(nodeID.getDepth() + 1) ||
+            !f_.getFullBelowCache()->touchIfExists(childHash.asUInt256(), nodeID, branch))
         {
             bool pending = false;
             auto d = descendAsync(
@@ -238,7 +240,28 @@ SHAMap::gmnProcessNodes(MissingNodes& mn, MissingNodes::StackEntry& se)
                 if (--mn.max <= 0)
                     return;
             }
-            else if (d->isInner() && !safeDowncast<SHAMapInnerNode*>(d)->isFullBelow(mn.generation))
+            // Only a leaf has a position of its own to judge, so the type is tested first. The
+            // depth test bounds the branch this arm names, and the arm below bounds the descent.
+            else if (
+                d->isLeaf() && !isLeafDepth(nodeID.getDepth()) && !belongsAt(nodeID, branch, *d))
+            {
+                // The judgment SHAMap::descend makes, for the descendAsync path, which hooks what
+                // it resolves before this runs. `fullBelow` is cleared as on the missing path.
+                fullBelow = false;
+                condemn(*d, childHash, nodeID.getChildNodeID(branch));
+                return;
+            }
+            else if (pastLeafDepth(nodeID.getDepth(), *d))
+            {
+                // A node resolved locally never passes through addKnownNode(), so the walk judges
+                // it here. The bound also covers nodeID, which the descent below writes.
+                condemn(*d, childHash, nodeID.getChildNodeID(branch));
+                return;
+            }
+            // The node's own full-below flag is not read here. The node object is shared by hash
+            // across maps and positions, so a flag another walk set says nothing about this
+            // position, and the position-keyed cache above has already missed for it.
+            else if (d->isInner())
             {
                 mn.stack.push(se);
 
@@ -257,10 +280,14 @@ SHAMap::gmnProcessNodes(MissingNodes& mn, MissingNodes::StackEntry& se)
 
     if (fullBelow)
     {  // No partial node encountered below this node
-        node->setFullBelowGen(mn.generation);
+        // The node flag is written for the root alone, since the root position is the only one a
+        // shared node object can vouch for; see SHAMapInnerNode::fullBelowGen_.
+        if (nodeID.isRoot())
+            node->setFullBelowGen(mn.generation);
         if (backed_)
         {
-            f_.getFullBelowCache()->insert(node->getHash().asUInt256());
+            // Keyed by position as well as hash, so the entry answers only for this position.
+            f_.getFullBelowCache()->insert(node->getHash().asUInt256(), nodeID);
         }
     }
 
@@ -291,6 +318,25 @@ SHAMap::gmnProcessDeferredReads(MissingNodes& mn)
         auto nodePtr = std::get<3>(deferredNode);
         auto const& nodeHash = parent->getChildHash(branch);
 
+        // A deferred entry carries the position the walk held when it posted the read, so a branch
+        // below it is named here only where the tree has room for one.
+        if (nodePtr && nodePtr->isLeaf() && !isLeafDepth(parentID.getDepth()) &&
+            !belongsAt(parentID, branch, *nodePtr))
+        {
+            // The judgment the synchronous paths make, for a node an async read resolved. Skips
+            // rather than returns, since every posted read must be drained while `mn` is alive.
+            condemn(*nodePtr, nodeHash, parentID.getChildNodeID(branch));
+            continue;
+        }
+
+        // The depth bound gmnProcessNodes carries beside its leaf test, for a node an async read
+        // resolved. Skips for the same reason as above.
+        if (nodePtr && pastLeafDepth(parentID.getDepth(), *nodePtr))
+        {
+            condemn(*nodePtr, nodeHash, parentID.getChildNodeID(branch));
+            continue;
+        }
+
         if (nodePtr)
         {  // Got the node
             nodePtr = parent->canonicalizeChild(branch, std::move(nodePtr));
@@ -301,6 +347,8 @@ SHAMap::gmnProcessDeferredReads(MissingNodes& mn)
         }
         else if ((mn.max > 0) && mn.missingHashes.insert(nodeHash).second)
         {
+            // getChildNodeID() is safe here: gmnProcessNodes refuses to descend into an inner node
+            // at kLeafDepth, so a deferred parent sits at most one level above it.
             mn.missingNodes.emplace_back(parentID.getChildNodeID(branch), nodeHash.asUInt256());
             --mn.max;
         }
@@ -311,17 +359,20 @@ SHAMap::gmnProcessDeferredReads(MissingNodes& mn)
     mn.deferred = 0;
 }
 
-/**
- * Get a list of node IDs and hashes for nodes that are part of this SHAMap
- * but not available locally.  The filter can hold alternate sources of
- * nodes that are not permanently stored locally
- */
 std::vector<std::pair<SHAMapNodeID, UInt256>>
 SHAMap::getMissingNodes(int max, SHAMapSyncFilter const* filter)
 {
     XRPL_ASSERT(root_->getHash().isNonZero(), "xrpl::SHAMap::getMissingNodes : nonzero root hash");
     XRPL_ASSERT(max > 0, "xrpl::SHAMap::getMissingNodes : valid max input");
 
+    if (!isValid())
+    {
+        // The root node's own hash, since getHash() unshares the tree on a zero hash.
+        JLOG(journal_.warn()) << "getMissingNodes called on an invalid map, root hash "
+                              << root_->getHash() << " seq " << ledgerSeq();
+        return {};
+    }
+
     MissingNodes mn(
         max,
         filter,
@@ -354,6 +405,11 @@ SHAMap::getMissingNodes(int max, SHAMapSyncFilter const* filter)
         {
             gmnProcessNodes(mn, pos);
 
+            // The walk just invalidated the map. The loop stops descending here but falls through
+            // to the drain below, since every posted read must be drained while `mn` is alive.
+            if (!isValid())
+                break;
+
             if (mn.max <= 0)
                 break;
 
@@ -383,6 +439,11 @@ SHAMap::getMissingNodes(int max, SHAMapSyncFilter const* filter)
         if (mn.deferred != 0)
             gmnProcessDeferredReads(mn);
 
+        // Reads are drained, so the map can be abandoned. What was collected belongs to a tree
+        // that cannot exist.
+        if (!isValid())
+            return {};
+
         if (mn.max <= 0)
             return std::move(mn.missingNodes);
 
@@ -391,12 +452,10 @@ SHAMap::getMissingNodes(int max, SHAMapSyncFilter const* filter)
 
             if (mn.stack.empty() && !mn.resumes.empty())
             {
-                // Recheck nodes we could not finish before
+                // Recheck nodes we could not finish before. A node's own full-below flag is not
+                // consulted: it is written for a root only, and a resumed node sits below one.
                 for (auto const& [innerNode, nodeId] : mn.resumes)
-                {
-                    if (!innerNode->isFullBelow(mn.generation))
-                        mn.stack.emplace(innerNode, nodeId, randInt(255), 0, true);
-                }
+                    mn.stack.emplace(innerNode, nodeId, randInt(255), 0, true);
 
                 mn.resumes.clear();
             }
@@ -416,6 +475,11 @@ SHAMap::getMissingNodes(int max, SHAMapSyncFilter const* filter)
 
     } while (node != nullptr);
 
+    // addKnownNode() on another thread can write the verdict after the loop's own test, so the map
+    // is judged once more before the result is returned.
+    if (!isValid())
+        return {};  // LCOV_EXCL_LINE: only that other thread reaches this, so no test does
+
     if (mn.missingNodes.empty())
         clearSynching();
 
@@ -527,11 +591,19 @@ SHAMap::addRootNode(
     XRPL_ASSERT(cowid_ >= 1, "xrpl::SHAMap::addRootNode : valid cowid");
     XRPL_ASSERT(rootNode, "xrpl::SHAMap::addRootNode : non-null root node");
 
-    // we already have a root_ node
+    // A map syncs against one hash and installs a root once, so a root already held is a duplicate
+    // only once it hashes to the hash asked for.
     if (root_->getHash().isNonZero())
     {
         JLOG(journal_.trace()) << "Got root node, already have one";
-        XRPL_ASSERT(root_->getHash() == hash, "xrpl::SHAMap::addRootNode : valid hash");
+
+        if (root_->getHash() != hash)
+        {
+            JLOG(journal_.warn()) << "Root node offered under hash " << hash
+                                  << ", but the map holds " << root_->getHash();
+            return SHAMapAddNode::invalid();
+        }
+
         return SHAMapAddNode::duplicate();
     }
 
@@ -555,7 +627,7 @@ SHAMap::addRootNode(
         Serializer s;
         root_->serializeWithPrefix(s);
         filter->gotNode(
-            false, root_->getHash(), ledgerSeq_, std::move(s.modData()), root_->getType());
+            false, root_->getHash(), ledgerSeq(), std::move(s.modData()), root_->getType());
     }
 
     return SHAMapAddNode::useful();
@@ -569,10 +641,6 @@ SHAMap::addKnownNode(
 {
     XRPL_ASSERT(!nodeID.isRoot(), "xrpl::SHAMap::addKnownNode : valid node");
     XRPL_ASSERT(treeNode, "xrpl::SHAMap::addKnownNode : non-null tree node");
-    XRPL_ASSERT_IF(
-        treeNode->isLeaf(),
-        nodeID.isPrefixOf(leafKey(*treeNode)),
-        "xrpl::SHAMap::addKnownNode : leaf position consistent with node ID");
 
     if (!isSynching())
     {
@@ -580,13 +648,13 @@ SHAMap::addKnownNode(
         return SHAMapAddNode::duplicate();
     }
 
-    auto const generation = f_.getFullBelowCache()->getGeneration();
     SHAMapNodeID currNodeID;
     auto currNode = root_.get();
 
-    while (currNode->isInner() &&
-           !safeDowncast<SHAMapInnerNode*>(currNode)->isFullBelow(generation) &&
-           (currNodeID.getDepth() < nodeID.getDepth()))
+    // The descent reads no node's own full-below flag: a node object is shared by hash across
+    // maps and positions, so that flag answers for the root position alone. The position-keyed
+    // cache lookup in the loop is the memo that answers for a position below it.
+    while (currNode->isInner() && (currNodeID.getDepth() < nodeID.getDepth()))
     {
         auto const branch = selectBranch(currNodeID, nodeID.getNodeID());
         auto inner = safeDowncast<SHAMapInnerNode*>(currNode);
@@ -598,7 +666,12 @@ SHAMap::addKnownNode(
         }
 
         auto childHash = inner->getChildHash(branch);
-        if (f_.getFullBelowCache()->touchIfExists(childHash.asUInt256()))
+
+        // The cache key carries the child's position beside its hash, so a hit answers for this
+        // child at this position and no other. The depth test runs first, so a node offered at
+        // kLeafDepth reaches the badDepth test below rather than being answered as a duplicate.
+        if (!isLeafDepth(currNodeID.getDepth() + 1) &&
+            f_.getFullBelowCache()->touchIfExists(childHash.asUInt256(), currNodeID, branch))
         {
             return SHAMapAddNode::duplicate();
         }
@@ -606,6 +679,14 @@ SHAMap::addKnownNode(
         auto prevNode = inner;
         std::tie(currNode, currNodeID) = descend(inner, currNodeID, branch, filter);
 
+        if (!isValid())
+        {
+            // descend condemned the map. `childHash` was read before that descent, so the
+            // comparison below would read a stale value.
+            JLOG(journal_.warn()) << "Node " << nodeID << " cannot be hooked into an invalid map";
+            return SHAMapAddNode::invalid();
+        }
+
         if (currNode != nullptr)
             continue;
 
@@ -616,25 +697,33 @@ SHAMap::addKnownNode(
             return SHAMapAddNode::invalid();
         }
 
-        // Inner nodes must be at a level strictly less than 64
-        // but leaf nodes (while notionally at level 64) can be
-        // at any depth up to and including 64:
-        if ((currNodeID.getDepth() > kLeafDepth) ||
-            (treeNode->isInner() && currNodeID.getDepth() == kLeafDepth))
+        // Every node from the root down hash-verified to get here, so the requested root hash
+        // itself commits to a shape no tree can have. The verdict belongs to that hash.
+        bool const badDepth = treeNode->isInner() && isLeafDepth(currNodeID.getDepth());
+        SOMETIMES(badDepth, "xrpl::SHAMap::addKnownNode : map is invalid");
+        if (badDepth)
         {
-            // Map is provably invalid
-            state_ = SHAMapState::Invalid;
-            return SHAMapAddNode::useful();
+            condemn(*treeNode, treeNode->getHash(), currNodeID);
+            return SHAMapAddNode::mapInvalidated();
         }
 
-        if (currNodeID != nodeID)
+        // The data hashes to the child at currNodeID but is labeled nodeID, so it is not the node
+        // asked for. Only the label is wrong, so the map stays sound.
+        bool const badPosition = (currNodeID != nodeID);
+        SOMETIMES(badPosition, "xrpl::SHAMap::addKnownNode : node ID does not match its position");
+        if (badPosition)
         {
-            // Either this node is broken or we didn't request it (yet)
-            JLOG(journal_.warn()) << "unable to hook node " << nodeID;
-            JLOG(journal_.info()) << " stuck at " << currNodeID;
-            JLOG(journal_.info()) << "got depth=" << nodeID.getDepth()
-                                  << ", walked to= " << currNodeID.getDepth();
-            return SHAMapAddNode::useful();
+            JLOG(journal_.warn()) << "Unable to hook node " << nodeID << ", stuck at "
+                                  << currNodeID;
+            return SHAMapAddNode::invalid();
+        }
+
+        // A leaf's own key names its position, and the hash test above ties this leaf to this
+        // parent, so the verdict belongs to the map. Below badPosition, since Invalid is terminal.
+        if (!belongsAt(nodeID, *treeNode))
+        {
+            condemn(*treeNode, treeNode->getHash(), nodeID);
+            return SHAMapAddNode::mapInvalidated();
         }
 
         if (backed_)
@@ -647,7 +736,7 @@ SHAMap::addKnownNode(
             Serializer s;
             treeNode->serializeWithPrefix(s);
             filter->gotNode(
-                false, childHash, ledgerSeq_, std::move(s.modData()), treeNode->getType());
+                false, childHash, ledgerSeq(), std::move(s.modData()), treeNode->getType());
         }
 
         return SHAMapAddNode::useful();
@@ -766,7 +855,7 @@ SHAMap::hasLeafNode(UInt256 const& tag, SHAMapHash const& targetNodeHash) const
         // Same kLeafDepth hazard as in visitDifferences above. That guard bounds the caller's own
         // traversal, not the map queried here, and the loop below descends from this map's root
         // independently, so this check is what keeps a malformed map from reaching getChildNodeID.
-        if (nodeID.getDepth() >= kLeafDepth)
+        if (isLeafDepth(nodeID.getDepth()))
         {
             // LCOV_EXCL_START
             UNREACHABLE("xrpl::SHAMap::hasLeafNode : inner node at leaf depth");
@@ -802,7 +891,7 @@ SHAMap::getProofPath(UInt256 const& key) const
         return {};
     }
 
-    if (auto const& node = stack.top().first; !node || node->isInner() ||
+    if (auto const& node = stack.top(); !node || node->isInner() ||
         intr_ptr::staticPointerCast<SHAMapLeafNode>(node)->peekItem()->key() != key)
     {
         JLOG(journal_.debug()) << "no path to " << key;
@@ -814,7 +903,7 @@ SHAMap::getProofPath(UInt256 const& key) const
     while (!stack.empty())
     {
         Serializer s;
-        stack.top().first->serializeForWire(s);
+        stack.top()->serializeForWire(s);
         path.emplace_back(std::move(s.modData()));
         stack.pop();
     }
@@ -849,8 +938,8 @@ SHAMap::verifyProofPath(UInt256 const& rootHash, UInt256 const& key, std::vector
                 // there. These nodes come off the wire, so a peer can still claim an inner one;
                 // reject it rather than passing this depth to selectBranch.
                 SOMETIMES(
-                    depth >= kLeafDepth, "xrpl::SHAMap::verifyProofPath : inner at leaf depth");
-                if (depth >= kLeafDepth)
+                    isLeafDepth(depth), "xrpl::SHAMap::verifyProofPath : inner at leaf depth");
+                if (isLeafDepth(depth))
                     return false;
 
                 auto const nodeId = SHAMapNodeID::createID(depth, key);
@@ -859,10 +948,9 @@ SHAMap::verifyProofPath(UInt256 const& rootHash, UInt256 const& key, std::vector
             }
             else
             {
-                // The hash chain up to rootHash only proves this leaf sits where the path claims,
-                // not that it is the leaf for `key`: a peer could substitute any other leaf whose
-                // subtree hashes to the same value at every level above it. Checking the terminal
-                // leaf's own key is what ties the proof to `key` specifically.
+                // The hash chain up to rootHash proves this leaf sits where the path claims. Any
+                // leaf whose subtree hashes the same at every level above satisfies that chain, so
+                // the terminal leaf's own key is what ties the proof to `key`.
                 if (leafKey(*node) != key)
                     return false;
 

src/libxrpl/tx/Transactor.cpp

@@ -16,6 +16,7 @@
 #include <xrpl/ledger/helpers/DelegateHelpers.h>
 #include <xrpl/ledger/helpers/NFTokenHelpers.h>
 #include <xrpl/ledger/helpers/OfferHelpers.h>
+#include <xrpl/ledger/helpers/ProposalHelpers.h>
 #include <xrpl/ledger/helpers/RippleStateHelpers.h>
 #include <xrpl/ledger/helpers/SponsorHelpers.h>
 #include <xrpl/protocol/AccountID.h>
@@ -327,10 +328,9 @@ Transactor::preflight2(PreflightContext const& ctx)
 
     auto const sigValid = checkValidity(ctx.registry.get().getHashRouter(), ctx.tx, ctx.rules);
     if (sigValid.first == Validity::SigBad)
-    {  // LCOV_EXCL_START
+    {
         JLOG(ctx.j.debug()) << "preflight2: bad signature. " << sigValid.second;
         return temINVALID;
-        // LCOV_EXCL_STOP
     }
 
     // Do not add any checks after this point that are relevant for
@@ -755,6 +755,19 @@ Transactor::checkSeqProxy(ReadView const& view, STTx const& tx, beast::Journal j
                             << "a_seq=" << aSeq << " t_seq=" << tSeqProx;
             return tefNO_TICKET;
         }
+
+        // While a TransactionProposal keyed to this Ticket exists, the
+        // Ticket is reserved: only the proposal's own proposed transaction
+        // may consume it, so unrelated activity cannot invalidate the
+        // proposal while signatures are being collected (On-Chain Cosigner spec §4.2.1).
+        // Cancelling the proposal frees the Ticket, so this is a retry, not
+        // a final failure. No proposal can exist before the Cosign amendment,
+        // so the gate only makes that dependency explicit.
+        if (view.rules().enabled(featureCosign) && !proposal::canConsumeTicket(view, tx))
+        {
+            JLOG(j.trace()) << "applyTransaction: ticket " << tSeqProx << " is reserved";
+            return terTICKET_RESERVED;
+        }
     }
 
     return tesSUCCESS;
@@ -866,8 +879,28 @@ Transactor::ticketDelete(
     // Update the Ticket owner's reserve.
     decreaseOwnerCountForObject(view, sleAccount, sleTicket, 1, j);
 
+    std::uint32_t const ticketSeq{(*sleTicket)[sfTicketSequence]};
+
     // Remove Ticket from ledger.
     view.erase(sleTicket);
+
+    // Once the Ticket is gone, a TransactionProposal keyed to it can never
+    // execute: its proposed transaction would fail with tefNO_TICKET. Clean
+    // up the stale proposal and release its Owner's reserve (On-Chain Cosigner spec §4.5).
+    // The reservation check in checkSeqProxy means this is reached only by
+    // the proposal's own proposed transaction executing (or failing with a
+    // claimed-fee tec), or by AccountDelete sweeping the target account's
+    // Tickets. No proposal can exist before the Cosign amendment, so the gate
+    // only makes that dependency explicit.
+    if (view.rules().enabled(featureCosign))
+    {
+        if (auto const sleProposal = view.peek(keylet::txProposal(account, ticketSeq)))
+        {
+            if (TER const ter = proposal::deleteProposal(view, sleProposal, j); !isTesSuccess(ter))
+                return ter;  // LCOV_EXCL_LINE
+        }
+    }
+
     return tesSUCCESS;
 }
 

src/libxrpl/tx/invariants/InvariantCheck.cpp

@@ -9,6 +9,7 @@
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/ledger/helpers/TokenHelpers.h>
 #include <xrpl/protocol/AccountID.h>
+#include <xrpl/protocol/Asset.h>
 #include <xrpl/protocol/Feature.h>
 #include <xrpl/protocol/Indexes.h>
 #include <xrpl/protocol/Issue.h>
@@ -22,6 +23,7 @@
 #include <xrpl/protocol/STLedgerEntry.h>
 #include <xrpl/protocol/STNumber.h>  // IWYU pragma: keep
 #include <xrpl/protocol/STTx.h>
+#include <xrpl/protocol/STVector256.h>
 #include <xrpl/protocol/SystemParameters.h>
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/TxFormats.h>
@@ -1010,6 +1012,78 @@ ValidClawback::finalize(
 
 //------------------------------------------------------------------------------
 
+// Whether `entry` is the trust line or MPToken through which `account` holds
+// `asset`. XRP has no such entry.
+static bool
+isHolding(SLE const& entry, Asset const& asset, AccountID const& account)
+{
+    return asset.visit(
+        [&](Issue const& issue) {
+            return !isXRP(issue) && keylet::trustLine(account, issue).check(entry);
+        },
+        [&](MPTIssue const& issue) {
+            return keylet::mptoken(issue.getMptID(), account).check(entry);
+        });
+}
+
+// Whether `entry`, linked into the owner directory of `pseudo`, belongs to the
+// AMM, Vault or LoanBroker that the pseudo-account was created for.
+static bool
+isOwnedByPseudoAccount(ReadView const& view, SLE const& pseudo, SLE const& entry)
+{
+    auto const pseudoAcctID = pseudo[sfAccount];
+
+    if (pseudo.isFieldPresent(sfAMMID))
+    {
+        if (entry.getType() == ltAMM)
+            return entry.key() == pseudo[sfAMMID];
+
+        auto const amm = view.read(keylet::amm(pseudo[sfAMMID]));
+        if (!amm)
+            return false;  // LCOV_EXCL_LINE
+        if (isHolding(entry, (*amm)[sfAsset], pseudoAcctID) ||
+            isHolding(entry, (*amm)[sfAsset2], pseudoAcctID))
+            return true;
+
+        // The AMM issues LP tokens, so each liquidity provider's trust line
+        // links into its directory.
+        if (entry.getType() != ltRIPPLE_STATE)
+            return false;
+        auto const low = entry[sfLowLimit].getIssuer();
+        auto const high = entry[sfHighLimit].getIssuer();
+        auto const lpCurrency = (*amm)[sfLPTokenBalance].get<Issue>().currency;
+        return (low == pseudoAcctID || high == pseudoAcctID) &&
+            entry.key() == keylet::trustLine(low, high, lpCurrency).key;
+    }
+
+    if (pseudo.isFieldPresent(sfVaultID))
+    {
+        if (entry.getType() == ltLOAN_BROKER)
+            return entry[sfVaultID] == pseudo[sfVaultID];
+
+        auto const vault = view.read(keylet::vault(pseudo[sfVaultID]));
+        if (!vault)
+            return false;  // LCOV_EXCL_LINE
+        return keylet::mptokenIssuance((*vault)[sfShareMPTID]).check(entry) ||
+            isHolding(entry, (*vault)[sfAsset], pseudoAcctID);
+    }
+
+    if (pseudo.isFieldPresent(sfLoanBrokerID))
+    {
+        if (entry.getType() == ltLOAN)
+            return entry[sfLoanBrokerID] == pseudo[sfLoanBrokerID];
+
+        auto const broker = view.read(keylet::loanBroker(pseudo[sfLoanBrokerID]));
+        if (!broker)
+            return false;  // LCOV_EXCL_LINE
+        auto const vault = view.read(keylet::vault((*broker)[sfVaultID]));
+        return vault && isHolding(entry, (*vault)[sfAsset], pseudoAcctID);
+    }
+
+    // A new pseudo-account kind must say what it owns.
+    return false;  // LCOV_EXCL_LINE
+}
+
 void
 ValidPseudoAccounts::visitEntry(bool isDelete, SLE::ConstRef before, SLE::ConstRef after)
 {
@@ -1019,6 +1093,33 @@ ValidPseudoAccounts::visitEntry(bool isDelete, SLE::ConstRef before, SLE::ConstR
         return;
     }
 
+    // Only owner directory pages carry sfOwner; book directories don't.
+    if (after && after->getType() == ltDIR_NODE && after->isFieldPresent(sfOwner))
+    {
+        auto const& afterIndexes = after->getFieldV256(sfIndexes);
+        std::vector<uint256> added;
+        if (!before)
+        {
+            added.assign(afterIndexes.begin(), afterIndexes.end());
+        }
+        else
+        {
+            auto const& beforeIndexes = before->getFieldV256(sfIndexes);
+            for (auto const& index : afterIndexes)
+            {
+                if (!std::ranges::contains(beforeIndexes, index))
+                    added.push_back(index);
+            }
+        }
+
+        if (!added.empty())
+        {
+            auto& owned = ownerDirAdditions_[after->getAccountID(sfOwner)];
+            owned.insert(owned.end(), added.begin(), added.end());
+        }
+        return;
+    }
+
     if (after && after->getType() == ltACCOUNT_ROOT)
     {
         bool const isPseudo = [&] {
@@ -1100,6 +1201,39 @@ ValidPseudoAccounts::finalize(
         if (enforce)
             return false;
     }
+
+    // Pre-fixCleanup3_5_0: what a pseudo-account owns is not checked.
+    // Post-fixCleanup3_5_0: it may own only what belongs to its AMM, Vault or
+    // LoanBroker.
+    if (!view.rules().enabled(fixCleanup3_5_0))
+        return true;
+
+    for (auto const& [owner, indexes] : ownerDirAdditions_)
+    {
+        auto const root = view.read(keylet::account(owner));
+        if (!root || !isPseudoAccount(root))
+            continue;
+
+        for (auto const& index : indexes)
+        {
+            auto const sle = view.read(keylet::unchecked(index));
+            if (!sle)
+            {
+                JLOG(j.fatal()) << "Invariant failed: pseudo-account " << toBase58(owner)
+                                << " owner directory links a missing object " << to_string(index);
+                return false;
+            }
+
+            if (!isOwnedByPseudoAccount(view, *root, *sle))
+            {
+                JLOG(j.fatal()) << "Invariant failed: pseudo-account " << toBase58(owner)
+                                << " may not own " << ledgerEntryTypeName(*sle) << " "
+                                << to_string(index);
+                return false;
+            }
+        }
+    }
+
     return true;
 }
 

src/libxrpl/tx/invariants/LoanBrokerInvariant.cpp

@@ -5,8 +5,8 @@
 #include <xrpl/beast/utility/Journal.h>
 #include <xrpl/beast/utility/Zero.h>
 #include <xrpl/ledger/ReadView.h>
-#include <xrpl/ledger/helpers/LendingHelpers.h>
 #include <xrpl/ledger/helpers/TokenHelpers.h>
+#include <xrpl/ledger/helpers/VaultHelpers.h>
 #include <xrpl/protocol/Asset.h>
 #include <xrpl/protocol/Feature.h>
 #include <xrpl/protocol/Indexes.h>
@@ -160,7 +160,7 @@ ValidLoanBroker::finalize(
                     roundToAsset(
                         Asset{vault->at(sfAsset)},
                         debtTotal,
-                        getAssetsTotalScale(vault),
+                        getVaultScale(vault),
                         Number::RoundingMode::TowardsZero) != beast::kZero)
                 {
                     JLOG(j.fatal())

src/libxrpl/tx/invariants/MPTInvariant.cpp

@@ -339,6 +339,7 @@ ValidMPTIssuance::finalize(
                 // Cap on MPToken creates and deletes while featureLendingProtocol is enabled.
                 // - LoanSet: at most two creates and no deletes.
                 // - VaultWithdraw: at most one create and one delete.
+                // - LoanBrokerDelete (post-fixCleanup3_5_0): at most one create and one delete.
                 // - Other MayAuthorizeMpt types: created + deleted <= 1.
                 // - MustAuthorizeMpt still requires exactly one create or delete below.
                 auto const mptokensExceedAuthorizeCap = [&] {
@@ -351,6 +352,10 @@ ValidMPTIssuance::finalize(
                         if (txnType == ttVAULT_WITHDRAW)
                             return mptokensCreated_ > 1 || mptokensDeleted_ > 1;
                     }
+                    // The cover payout may create the owner's MPToken while the
+                    // pseudo-account's MPToken is deleted.
+                    if (rules.enabled(fixCleanup3_5_0) && txnType == ttLOAN_BROKER_DELETE)
+                        return mptokensCreated_ > 1 || mptokensDeleted_ > 1;
                     return (mptokensCreated_ + mptokensDeleted_) > 1;
                 };
                 if (mptokensExceedAuthorizeCap())
@@ -1018,24 +1023,25 @@ ValidMPTTransfer::finalize(
             continue;
         }
 
-        // These transactions are recovery/settlement paths. They may move an
-        // existing MPT position even after the issuer clears CanTransfer, so
-        // holders are not trapped in AMM, vault, or loan protocol accounts.
-        auto const waivesCanTransfer = txnType == ttAMM_WITHDRAW ||
-            (view.rules().enabled(fixCleanup3_2_0) &&
-             (txnType == ttVAULT_WITHDRAW || txnType == ttLOAN_BROKER_COVER_WITHDRAW ||
-              txnType == ttLOAN_PAY));
-        auto const canTransfer = sleIssuance->isFlag(lsfMPTCanTransfer) || waivesCanTransfer;
-        auto const canTrade = sleIssuance->isFlag(lsfMPTCanTrade);
-        auto const reqAuth = sleIssuance->isFlag(lsfMPTRequireAuth);
-
         // This issuance is the LoanManage default's own vault asset, so the
-        // broker/vault freeze exemption applies to it -- an unrelated MPT
-        // issuance the same accounts happen to hold is still caught.
+        // broker/vault freeze and CanTransfer exemptions apply to it -- an
+        // unrelated MPT the same accounts happen to hold is still caught.
         bool const isLoanDefaultAsset = loanDefaultAccounts &&
             loanDefaultAccounts->asset.holds<MPTIssue>() &&
             loanDefaultAccounts->asset.get<MPTIssue>().getMptID() == mptID;
 
+        // These transactions settle an existing MPT position out of a protocol
+        // account. They do not require CanTransfer.
+        auto const waivesCanTransfer = txnType == ttAMM_WITHDRAW ||
+            (view.rules().enabled(fixCleanup3_2_0) &&
+             (txnType == ttVAULT_WITHDRAW || txnType == ttLOAN_BROKER_COVER_WITHDRAW ||
+              txnType == ttLOAN_PAY)) ||
+            (view.rules().enabled(fixCleanup3_5_0) &&
+             (isLoanDefaultAsset || txnType == ttLOAN_BROKER_DELETE));
+        auto const canTransfer = sleIssuance->isFlag(lsfMPTCanTransfer) || waivesCanTransfer;
+        auto const canTrade = sleIssuance->isFlag(lsfMPTCanTrade);
+        auto const reqAuth = sleIssuance->isFlag(lsfMPTRequireAuth);
+
         for (auto const& [account, value] : values)
         {
             // Classify each account as a sender or receiver based on whether their MPTAmount

src/libxrpl/tx/invariants/VaultInvariant.cpp

@@ -7,12 +7,14 @@
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/ledger/ReadView.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
+#include <xrpl/ledger/helpers/TokenHelpers.h>
 #include <xrpl/ledger/helpers/VaultHelpers.h>
 #include <xrpl/protocol/Feature.h>
 #include <xrpl/protocol/Indexes.h>
 #include <xrpl/protocol/Issue.h>
 #include <xrpl/protocol/LedgerFormats.h>
 #include <xrpl/protocol/Protocol.h>
+#include <xrpl/protocol/Rate.h>
 #include <xrpl/protocol/SField.h>
 #include <xrpl/protocol/STAmount.h>
 #include <xrpl/protocol/STLedgerEntry.h>
@@ -63,6 +65,9 @@ ValidVault::Vault::make(SLE const& from)
     self.assetsAvailable = from.at(sfAssetsAvailable);
     self.assetsMaximum = from.at(sfAssetsMaximum);
     self.lossUnrealized = from.at(sfLossUnrealized);
+    self.assetsDeployed = from[~sfAssetsDeployed].value_or(Number{0});
+    self.yieldUnrealized = from[~sfYieldUnrealized].value_or(Number{0});
+    self.version = decodeVaultVersion(from[~sfLEVersion]);
     self.vaultKind = from[~sfVaultKind];
     self.subscriptionDate = from[~sfSubscriptionDate];
     self.redemptionDate = from[~sfRedemptionDate];
@@ -408,6 +413,70 @@ ValidVault::computeVaultMinScale(DeltaInfo const& vaultDelta, Rules const& rules
     return computeCoarsestScale({vaultDelta, totalDelta, availableDelta});
 }
 
+bool
+ValidVault::checkTotalsAddUp(
+    Vault const& afterVault,
+    Vault const& beforeVault,
+    Asset const& vaultAsset,
+    bool fix340Enabled,
+    std::int32_t minScale,
+    Number const& roundedVaultDelta,
+    Number const& exactVaultDelta,
+    char const* verb,
+    beast::Journal const& j)
+{
+    bool result = true;
+
+    // FixedPrecision: the stored AssetsTotal is a Downward-floored cache
+    // (AA + AD), not an exact running total, so comparing its delta against
+    // the real transfer can be off by more than one unit purely from
+    // independent floor-rounding of the two snapshots -- not an accounting
+    // bug. The stored-cache-equals-derived-total check elsewhere in finalize,
+    // plus the AssetsDeployed-only-changed-by-lending-transactors check,
+    // already cover AssetsTotal; only compare it here on Legacy/CashBasis,
+    // where AssetsTotal is written exactly alongside AA.
+    if (afterVault.version != VaultVersion::FixedPrecision)
+    {
+        auto const assetTotalDelta =
+            roundToAsset(vaultAsset, afterVault.assetsTotal - beforeVault.assetsTotal, minScale);
+        bool const totalAddsUp = fix340Enabled
+            ? agreesWithinOneUnit(assetTotalDelta, roundedVaultDelta, vaultAsset, minScale)
+            : assetTotalDelta == roundedVaultDelta;
+        if (!totalAddsUp)
+        {
+            JLOG(j.fatal()) << "Invariant failed: " << verb
+                            << " and assets outstanding must add up";
+            result = false;
+        }
+    }
+
+    auto const assetAvailableDelta = roundToAsset(
+        vaultAsset, afterVault.assetsAvailable - beforeVault.assetsAvailable, minScale);
+    // FixedPrecision: AssetsAvailable is the exact, single writer
+    // (adjustVaultBalances)-managed balance, so its delta must match the real
+    // transfer exactly, with no rounding tolerance -- compare the exact
+    // deltas, not the values rounded to the posterior AssetsTotal scale.
+    bool const availableAddsUp = [&] {
+        if (afterVault.version == VaultVersion::FixedPrecision)
+        {
+            return (afterVault.assetsAvailable - beforeVault.assetsAvailable) == exactVaultDelta;
+        }
+        if (fix340Enabled)
+        {
+            return agreesWithinOneUnit(
+                assetAvailableDelta, roundedVaultDelta, vaultAsset, minScale);
+        }
+        return assetAvailableDelta == roundedVaultDelta;
+    }();
+    if (!availableAddsUp)
+    {
+        JLOG(j.fatal()) << "Invariant failed: " << verb << " and assets available must add up";
+        result = false;
+    }
+
+    return result;
+}
+
 bool
 ValidVault::finalize(
     STTx const& tx,
@@ -418,6 +487,7 @@ ValidVault::finalize(
 {
     bool const enforce = view.rules().enabled(featureSingleAssetVault);
     bool const fix340Enabled = view.rules().enabled(fixCleanup3_4_0);
+    bool const fix350Enabled = view.rules().enabled(fixCleanup3_5_0);
 
     if (!isTesSuccess(ret))
         return true;  // Do not perform checks
@@ -585,6 +655,13 @@ ValidVault::finalize(
                                "vault must have no assets available";
             result = false;
         }
+        if (afterVault.version == VaultVersion::FixedPrecision &&
+            afterVault.assetsDeployed != kZero)
+        {
+            JLOG(j.fatal()) << "Invariant failed: updated zero sized "
+                               "vault must have no AssetsDeployed";
+            result = false;
+        }
     }
     else if (updatedShares->sharesTotal > updatedShares->sharesMaximum)
     {
@@ -609,6 +686,14 @@ ValidVault::finalize(
     else
     {
         bool const gapExceeded = [&] {
+            if (afterVault.version == VaultVersion::FixedPrecision)
+            {
+                // FixedPrecision: both LossUnrealized and AssetsDeployed are exact
+                // (never rounded), so compare them directly. AssetsTotal is
+                // just a rounded cache of AssetsAvailable + AssetsDeployed and
+                // is not the reference this check needs.
+                return afterVault.lossUnrealized > afterVault.assetsDeployed;
+            }
             if (!fix340Enabled)
             {
                 return afterVault.lossUnrealized >
@@ -631,6 +716,43 @@ ValidVault::finalize(
         }
     }
 
+    if (afterVault.version == VaultVersion::FixedPrecision)
+    {
+        if (afterVault.assetsDeployed < kZero)
+        {
+            JLOG(j.fatal()) << "Invariant failed: AssetsDeployed must not be negative";
+            result = false;
+        }
+        else if (
+            Number(STAmount{afterVault.asset, afterVault.assetsDeployed}) !=
+            afterVault.assetsDeployed)
+        {
+            JLOG(j.fatal())  //
+                << "Invariant failed: AssetsDeployed must be exactly representable "
+                   "at the vault asset's precision";
+            result = false;
+        }
+
+        Number const expectedAssetsTotal = [&] {
+            NumberRoundModeGuard const rg(Number::RoundingMode::Downward);
+            return Number(
+                STAmount{afterVault.asset, afterVault.assetsAvailable + afterVault.assetsDeployed});
+        }();
+        if (afterVault.assetsTotal != expectedAssetsTotal)
+        {
+            JLOG(j.fatal())  //
+                << "Invariant failed: stored AssetsTotal must equal AssetsAvailable "
+                   "plus AssetsDeployed, rounded Downward";
+            result = false;
+        }
+
+        if (afterVault.yieldUnrealized < kZero)
+        {
+            JLOG(j.fatal()) << "Invariant failed: YieldUnrealized must not be negative";
+            result = false;
+        }
+    }
+
     if (fix340Enabled && afterVault.lossUnrealized < kZero)
     {
         JLOG(j.fatal()) << "Invariant failed: loss unrealized must not be negative";
@@ -659,6 +781,18 @@ ValidVault::finalize(
         return !enforce;  // That's all we can do here
     }
 
+    // ttLOAN_SET, ttLOAN_PAY and ttLOAN_MANAGE are the only transactors allowed to
+    // write AssetsDeployed and YieldUnrealized; any new transactor that writes
+    // either field must be added to both allow-lists below.
+    if (afterVault.version == VaultVersion::FixedPrecision && !beforeVault_.empty() &&
+        afterVault.assetsDeployed != beforeVault_[0].assetsDeployed && txnType != ttLOAN_SET &&
+        txnType != ttLOAN_PAY && txnType != ttLOAN_MANAGE)
+    {
+        JLOG(j.fatal()) <<  //
+            "Invariant failed: vault transaction must not change AssetsDeployed";
+        result = false;
+    }
+
     if (!beforeVault_.empty() && afterVault.lossUnrealized != beforeVault_[0].lossUnrealized &&
         txnType != ttLOAN_MANAGE && txnType != ttLOAN_PAY)
     {
@@ -668,6 +802,16 @@ ValidVault::finalize(
         result = false;
     }
 
+    if (afterVault.version == VaultVersion::FixedPrecision && !beforeVault_.empty() &&
+        afterVault.yieldUnrealized != beforeVault_[0].yieldUnrealized && txnType != ttLOAN_SET &&
+        txnType != ttLOAN_PAY && txnType != ttLOAN_MANAGE)
+    {
+        JLOG(j.fatal()) <<  //
+            "Invariant failed: vault transaction must not change yield "
+            "unrealized";
+        result = false;
+    }
+
     // Immutability of VaultKind, SubscriptionDate and RedemptionDate is enforced by
     // NoModifiedUnmodifiableFields in InvariantCheck.cpp.
 
@@ -716,7 +860,9 @@ ValidVault::finalize(
                 }
 
                 if (afterVault.assetsAvailable != kZero || afterVault.assetsTotal != kZero ||
-                    afterVault.lossUnrealized != kZero || updatedShares->sharesTotal != 0)
+                    afterVault.lossUnrealized != kZero || updatedShares->sharesTotal != 0 ||
+                    (afterVault.version == VaultVersion::FixedPrecision &&
+                     (afterVault.assetsDeployed != kZero || afterVault.yieldUnrealized != kZero)))
                 {
                     JLOG(j.fatal())  //
                         << "Invariant failed: created vault must be empty";
@@ -880,7 +1026,17 @@ ValidVault::finalize(
                     result = false;
                 }
 
-                if (vaultDeltaAssets <= kZero)
+                // FixedPrecision: AssetsAvailable is exact and the pseudo-account
+                // delta is exact; rounding either one down to the posterior
+                // AssetsTotal scale before the sign check can turn a legitimate
+                // sub-unit deposit into a false zero. Compare the exact deltas
+                // instead; Legacy/CashBasis keep the rounded comparison.
+                bool const isFixedPrecision = afterVault.version == VaultVersion::FixedPrecision;
+                Number const exactVaultDeltaAssets = maybeVaultDeltaAssets->delta;
+                Number const signCheckDeltaAssets =
+                    isFixedPrecision ? exactVaultDeltaAssets : vaultDeltaAssets;
+
+                if (signCheckDeltaAssets <= kZero)
                 {
                     JLOG(j.fatal()) <<  //
                         "Invariant failed: deposit must increase vault balance";
@@ -976,29 +1132,17 @@ ValidVault::finalize(
                     result = false;
                 }
 
-                auto const assetTotalDelta = roundToAsset(
-                    vaultAsset, afterVault.assetsTotal - beforeVault.assetsTotal, minScale);
-                bool const totalAddsUp = fix340Enabled
-                    ? agreesWithinOneUnit(assetTotalDelta, vaultDeltaAssets, vaultAsset, minScale)
-                    : assetTotalDelta == vaultDeltaAssets;
-                if (!totalAddsUp)
-                {
-                    JLOG(j.fatal())
-                        << "Invariant failed: deposit and assets outstanding must add up";
+                if (!checkTotalsAddUp(
+                        afterVault,
+                        beforeVault,
+                        vaultAsset,
+                        fix340Enabled,
+                        minScale,
+                        vaultDeltaAssets,
+                        exactVaultDeltaAssets,
+                        "deposit",
+                        j))
                     result = false;
-                }
-
-                auto const assetAvailableDelta = roundToAsset(
-                    vaultAsset, afterVault.assetsAvailable - beforeVault.assetsAvailable, minScale);
-                bool const availableAddsUp = fix340Enabled
-                    ? agreesWithinOneUnit(
-                          assetAvailableDelta, vaultDeltaAssets, vaultAsset, minScale)
-                    : assetAvailableDelta == vaultDeltaAssets;
-                if (!availableAddsUp)
-                {
-                    JLOG(j.fatal()) << "Invariant failed: deposit and assets available must add up";
-                    result = false;
-                }
 
                 return result;
             }
@@ -1054,7 +1198,17 @@ ValidVault::finalize(
                 auto const vaultPseudoDeltaAssets =
                     roundToAsset(vaultAsset, vaultDeltaAssets.delta, minScale);
 
-                if (!zeroDeltaIsLegitimate && vaultPseudoDeltaAssets >= kZero)
+                // FixedPrecision: AssetsAvailable is exact and the pseudo-account
+                // delta is exact; rounding either one down to the posterior
+                // AssetsTotal scale before the sign check can turn a legitimate
+                // sub-unit withdrawal into a false zero and reject it. Compare
+                // the exact deltas instead; Legacy/CashBasis keep the rounded
+                // comparison.
+                bool const isFixedPrecision = afterVault.version == VaultVersion::FixedPrecision;
+                Number const signCheckDeltaAssets =
+                    isFixedPrecision ? vaultDeltaAssets.delta : vaultPseudoDeltaAssets;
+
+                if (!zeroDeltaIsLegitimate && signCheckDeltaAssets >= kZero)
                 {
                     JLOG(j.fatal()) << "Invariant failed: withdrawal must decrease vault balance";
                     result = false;
@@ -1144,6 +1298,18 @@ ValidVault::finalize(
 
                         auto const localPseudoDeltaAssets =
                             roundToAsset(vaultAsset, vaultPseudoDeltaAssets, localMinScale);
+                        auto const rate = transferRate(view, vaultAsset);
+                        bool const feeAdjustedWithdrawal = fix350Enabled && distinctDestination &&
+                            !vaultAsset.native() && tx[sfAccount] != vaultAsset.getIssuer() &&
+                            rate != kParityRate;
+                        auto expectedDestinationDelta = localPseudoDeltaAssets * -1;
+                        if (feeAdjustedWithdrawal)
+                        {
+                            expectedDestinationDelta =
+                                subtractTransferFee(
+                                    STAmount{vaultAsset, expectedDestinationDelta}, rate)
+                                    .value();
+                        }
                         // For IOU assets near a precision boundary the destination's STAmount
                         // exponent can shift, making part of the sent value unrepresentable at
                         // the receiver's new scale — that portion is irreversibly absorbed by the
@@ -1152,7 +1318,8 @@ ValidVault::finalize(
                         // the destination's scale.  Floor rounding is used so that values exactly
                         // at the step boundary are not mistakenly dismissed.  Any representable
                         // discrepancy indicates a real accounting bug and must be caught.
-                        auto const destroyedIsSubUlp = tolerateZeroDelta &&
+                        auto const destroyedIsSubUlp = !feeAdjustedWithdrawal &&
+                            tolerateZeroDelta &&
                             roundToAsset(
                                 vaultAsset,
                                 vaultDeltaAssets.delta * -1 - destinationDelta.delta,
@@ -1160,11 +1327,11 @@ ValidVault::finalize(
                                 Number::RoundingMode::Downward) == kZero;
                         bool const withdrawAddsUp = fix340Enabled
                             ? agreesWithinOneUnit(
-                                  localPseudoDeltaAssets * -1,
+                                  expectedDestinationDelta,
                                   roundedDestinationDelta,
                                   vaultAsset,
                                   localMinScale)
-                            : localPseudoDeltaAssets * -1 == roundedDestinationDelta;
+                            : expectedDestinationDelta == roundedDestinationDelta;
                         if (!destroyedIsSubUlp && !withdrawAddsUp)
                         {
                             JLOG(j.fatal()) << "Invariant failed: " <<  //
@@ -1205,33 +1372,17 @@ ValidVault::finalize(
                     result = false;
                 }
 
-                auto const assetTotalDelta = roundToAsset(
-                    vaultAsset, afterVault.assetsTotal - beforeVault.assetsTotal, minScale);
-                // Note, vaultBalance is negative (see check above)
-                bool const totalAddsUp = fix340Enabled
-                    ? agreesWithinOneUnit(
-                          assetTotalDelta, vaultPseudoDeltaAssets, vaultAsset, minScale)
-                    : assetTotalDelta == vaultPseudoDeltaAssets;
-                if (!totalAddsUp)
-                {
-                    JLOG(j.fatal())
-                        << "Invariant failed: withdrawal and assets outstanding must add up";
+                if (!checkTotalsAddUp(
+                        afterVault,
+                        beforeVault,
+                        vaultAsset,
+                        fix340Enabled,
+                        minScale,
+                        vaultPseudoDeltaAssets,
+                        vaultDeltaAssets.delta,
+                        "withdrawal",
+                        j))
                     result = false;
-                }
-
-                auto const assetAvailableDelta = roundToAsset(
-                    vaultAsset, afterVault.assetsAvailable - beforeVault.assetsAvailable, minScale);
-
-                bool const availableAddsUp = fix340Enabled
-                    ? agreesWithinOneUnit(
-                          assetAvailableDelta, vaultPseudoDeltaAssets, vaultAsset, minScale)
-                    : assetAvailableDelta == vaultPseudoDeltaAssets;
-                if (!availableAddsUp)
-                {
-                    JLOG(j.fatal())
-                        << "Invariant failed: withdrawal and assets available must add up";
-                    result = false;
-                }
 
                 return result;
             }
@@ -1263,39 +1414,33 @@ ValidVault::finalize(
                         computeVaultMinScale(*maybeVaultDeltaAssets, view.rules());
                     auto const vaultDeltaAssets =
                         roundToAsset(vaultAsset, maybeVaultDeltaAssets->delta, minScale);
-                    if (vaultDeltaAssets >= kZero)
+                    // FixedPrecision: AssetsAvailable is exact and the
+                    // pseudo-account delta is exact; rounding either one down
+                    // to the posterior AssetsTotal scale before the sign
+                    // check can turn a legitimate sub-unit clawback into a
+                    // false zero and reject it. Compare the exact deltas
+                    // instead; Legacy/CashBasis keep the rounded comparison.
+                    bool const isFixedPrecision =
+                        afterVault.version == VaultVersion::FixedPrecision;
+                    Number const signCheckDeltaAssets =
+                        isFixedPrecision ? maybeVaultDeltaAssets->delta : vaultDeltaAssets;
+                    if (signCheckDeltaAssets >= kZero)
                     {
                         JLOG(j.fatal()) << "Invariant failed: clawback must decrease vault balance";
                         result = false;
                     }
 
-                    auto const assetsTotalDelta = roundToAsset(
-                        vaultAsset, afterVault.assetsTotal - beforeVault.assetsTotal, minScale);
-                    bool const totalAddsUp = fix340Enabled
-                        ? agreesWithinOneUnit(
-                              assetsTotalDelta, vaultDeltaAssets, vaultAsset, minScale)
-                        : assetsTotalDelta == vaultDeltaAssets;
-                    if (!totalAddsUp)
-                    {
-                        JLOG(j.fatal()) <<  //
-                            "Invariant failed: clawback and assets outstanding must add up";
+                    if (!checkTotalsAddUp(
+                            afterVault,
+                            beforeVault,
+                            vaultAsset,
+                            fix340Enabled,
+                            minScale,
+                            vaultDeltaAssets,
+                            maybeVaultDeltaAssets->delta,
+                            "clawback",
+                            j))
                         result = false;
-                    }
-
-                    auto const assetAvailableDelta = roundToAsset(
-                        vaultAsset,
-                        afterVault.assetsAvailable - beforeVault.assetsAvailable,
-                        minScale);
-                    bool const availableAddsUp = fix340Enabled
-                        ? agreesWithinOneUnit(
-                              assetAvailableDelta, vaultDeltaAssets, vaultAsset, minScale)
-                        : assetAvailableDelta == vaultDeltaAssets;
-                    if (!availableAddsUp)
-                    {
-                        JLOG(j.fatal()) <<  //
-                            "Invariant failed: clawback and assets available must add up";
-                        result = false;
-                    }
                 }
                 else if (!isVaultEmpty(beforeVault))
                 {

src/libxrpl/tx/paths/AMMLiquidity.cpp

@@ -177,7 +177,7 @@ AMMLiquidity<TIn, TOut>::getOffer(ReadView const& view, std::optional<Quality> c
                 return maxOffer(balances);
             }
             if (auto const amounts =
-                    changeSpotPriceQuality(balances, *clobQuality, tradingFee_, view.rules(), j_))
+                    changeSpotPriceQuality(balances, *clobQuality, tradingFee_, j_))
             {
                 return AMMOffer<TIn, TOut>(*this, *amounts, balances, Quality{*amounts});
             }

src/libxrpl/tx/paths/BookStep.cpp

@@ -24,7 +24,6 @@
 #include <xrpl/protocol/MPTIssue.h>
 #include <xrpl/protocol/Quality.h>
 #include <xrpl/protocol/Rate.h>
-#include <xrpl/protocol/Rules.h>
 #include <xrpl/protocol/SField.h>
 #include <xrpl/protocol/STAmount.h>
 #include <xrpl/protocol/TER.h>
@@ -83,6 +82,11 @@ protected:
     std::optional<AMMLiquidity<TIn, TOut>> ammLiquidity_;
     beast::Journal const j_;
     Asset const strandDeliver_;
+    // MaximumAmount of book_.in if it is an MPT. Taking an MPT offer has the
+    // issuer send TakerPays to the owner, and a send above the cap is rejected
+    // (isMPTOverflow). forEachOffer limits the offer's input to the cap so it
+    // fills partially instead of failing the strand.
+    std::optional<TIn> maxIn_;
 
     struct Cache
     {
@@ -106,6 +110,12 @@ private:
         , j_(ctx.j)
         , strandDeliver_(ctx.strandDeliver)
     {
+        if constexpr (std::is_same_v<TIn, MPTAmount>)
+        {
+            if (auto const max = maxMPTAmount(ctx.view, in.get<MPTIssue>().getMptID()))
+                maxIn_.emplace(*max);
+        }
+
         if (auto const ammSle = ctx.view.read(keylet::amm(in, out));
             ammSle && ammSle->getFieldAmount(sfLPTokenBalance) != beast::kZero)
         {
@@ -344,8 +354,7 @@ public:
         Quality const& ofrQ,
         DebtDirection prevStepDir,
         WaiveTransferFee waiveFee,
-        OfferType,
-        Rules const&) const
+        OfferType) const
     {
         // Charge the offer owner, not the sender
         // Charge a fee even if the owner is the same as the issuer
@@ -516,8 +525,7 @@ public:
         Quality const& ofrQ,
         DebtDirection prevStepDir,
         WaiveTransferFee waiveFee,
-        OfferType offerType,
-        Rules const& rules) const
+        OfferType offerType) const
     {
         // Offer x-ing does not charge a transfer fee when the offer's owner
         // is the same as the strand dst. It is important that
@@ -529,10 +537,6 @@ public:
         // Single path AMM offer has to factor in the transfer in rate
         // when calculating the upper bound quality and the quality function
         // because single path AMM's offer quality is not constant.
-        if (!rules.enabled(fixAMMv1_1))
-        {
-            return ofrQ;
-        }
         if (offerType == OfferType::Clob ||
             (this->ammLiquidity_ && this->ammLiquidity_->multiPath()))
         {
@@ -584,7 +588,7 @@ BookStep<TIn, TOut, TDerived>::qualityUpperBound(ReadView const& v, DebtDirectio
                                                                         : WaiveTransferFee::No;
 
     Quality const q = static_cast<TDerived const*>(this)->adjustQualityWithFees(
-        v, std::get<Quality>(*res), prevStepDir, waiveFee, std::get<OfferType>(*res), v.rules());
+        v, std::get<Quality>(*res), prevStepDir, waiveFee, std::get<OfferType>(*res));
     return {q, dir};
 }
 
@@ -603,7 +607,7 @@ BookStep<TIn, TOut, TDerived>::getQualityFunc(ReadView const& v, DebtDirection p
     {
         auto static const kQOne = Quality{STAmount::kURateOne};
         auto const q = static_cast<TDerived const*>(this)->adjustQualityWithFees(
-            v, kQOne, prevStepDir, WaiveTransferFee::Yes, OfferType::Amm, v.rules());
+            v, kQOne, prevStepDir, WaiveTransferFee::Yes, OfferType::Amm);
         if (q == kQOne)
             return {res, dir};
         QualityFunction qf{q, QualityFunction::CLOBLikeTag{}};
@@ -618,8 +622,7 @@ BookStep<TIn, TOut, TDerived>::getQualityFunc(ReadView const& v, DebtDirection p
                           // always has quality set
         prevStepDir,
         WaiveTransferFee::No,
-        OfferType::Clob,
-        v.rules());
+        OfferType::Clob);
     return {QualityFunction{q, QualityFunction::CLOBLikeTag{}}, dir};
 }
 
@@ -630,6 +633,38 @@ BookStep<TIn, TOut, TDerived>::offersUsed() const
     return offersUsed_;
 }
 
+// Limit the offer to the given input (net of the taker's transfer fee), and
+// the step output and owner's charge with it. The caller sets stpAmt.in.
+template <class TIn, class TOut, class Offer>
+static void
+limitOfferIn(
+    Offer const& offer,
+    TAmounts<TIn, TOut>& ofrAmt,
+    TAmounts<TIn, TOut>& stpAmt,
+    TOut& ownerGives,
+    std::uint32_t transferRateOut,
+    TIn const& inLmt)
+{
+    // It turns out we can prevent order book blocking by (strictly)
+    // rounding down the ceil_in() result.  By rounding down we guarantee
+    // that the quality of an offer left in the ledger is as good or
+    // better than the quality of the containing order book page.
+    //
+    // This adjustment changes transaction outcomes, so it must be made
+    // under an amendment.
+    ofrAmt = offer.limitIn(ofrAmt, inLmt, /* roundUp */ false);
+    stpAmt.out = ofrAmt.out;
+    // Round up for MPT output so the offer owner pays the full
+    // ceil(amount × rate) fee, matching direct Payment semantics.  IOU uses
+    // floating-point arithmetic so the floor/ceil distinction is sub-epsilon
+    // there; preserve the historical false to avoid changing IOU behavior.
+    ownerGives = mulRatio(
+        ofrAmt.out,
+        transferRateOut,
+        QUALITY_ONE,
+        /*roundUp*/ std::is_same_v<TOut, MPTAmount>);
+}
+
 // Adjust the offer amount and step amount subject to the given input limit
 template <class TIn, class TOut, class Offer>
 static void
@@ -646,24 +681,7 @@ limitStepIn(
     {
         stpAmt.in = limit;
         auto const inLmt = mulRatio(stpAmt.in, QUALITY_ONE, transferRateIn, /*roundUp*/ false);
-        // It turns out we can prevent order book blocking by (strictly)
-        // rounding down the ceil_in() result.  By rounding down we guarantee
-        // that the quality of an offer left in the ledger is as good or
-        // better than the quality of the containing order book page.
-        //
-        // This adjustment changes transaction outcomes, so it must be made
-        // under an amendment.
-        ofrAmt = offer.limitIn(ofrAmt, inLmt, /* roundUp */ false);
-        stpAmt.out = ofrAmt.out;
-        // Round up for MPT output so the offer owner pays the full
-        // ceil(amount × rate) fee, matching direct Payment semantics.  IOU uses
-        // floating-point arithmetic so the floor/ceil distinction is sub-epsilon
-        // there; preserve the historical false to avoid changing IOU behavior.
-        ownerGives = mulRatio(
-            ofrAmt.out,
-            transferRateOut,
-            QUALITY_ONE,
-            /*roundUp*/ std::is_same_v<TOut, MPTAmount>);
+        limitOfferIn(offer, ofrAmt, stpAmt, ownerGives, transferRateOut, inLmt);
     }
 }
 
@@ -785,29 +803,45 @@ BookStep<TIn, TOut, TDerived>::forEachOffer(
         auto ofrAmt = offer.amount();
         TAmounts stpAmt{ofrAmt.in, ofrAmt.out};
         auto ownerGives = ofrAmt.out;
+        // A bid above MaximumAmount is limited to it below (see maxIn_). Gross
+        // up no more than the cap: the whole bid may not fit once grossed up
+        // even though a fill at the cap does.
+        bool const capInMPT = prevStep_ && maxIn_ && offer.owner() != assetIn.getIssuer();
+        auto const amtIn = [&](TIn const& in) { return capInMPT && *maxIn_ < in ? *maxIn_ : in; };
         try
         {
             // All arithmetic in this block runs before the offer is consumed.
             // A crafted MPTokensV2 offer can overflow while transfer rates or
             // crossing limits are applied; remove that unusable offer instead
             // of letting it persist as a tecINTERNAL source.
-            stpAmt.in = mulRatio(ofrAmt.in, ofrInRate, QUALITY_ONE, /*roundUp*/ true);
+            stpAmt.in = mulRatio(amtIn(ofrAmt.in), ofrInRate, QUALITY_ONE, /*roundUp*/ true);
 
-            // owner pays the transfer fee.
-            ownerGives = mulRatio(
-                ofrAmt.out,
-                ofrOutRate,
-                QUALITY_ONE,
-                /*roundUp*/ std::is_same_v<TOut, MPTAmount>);
+            // owner pays the transfer fee. An MPT gross-up that doesn't fit in
+            // an MPT amount exceeds any owner's funds (an MPT issuer's funds
+            // are what it can still issue), so a large, partially funded offer
+            // is limited to its funds below instead of removed as an overflow.
+            std::optional<TOut> grossOut;
+            if constexpr (std::is_same_v<TOut, MPTAmount>)
+            {
+                grossOut = tryMulRatio(ofrAmt.out, ofrOutRate, QUALITY_ONE, /*roundUp*/ true);
+            }
+            else
+            {
+                grossOut = mulRatio(ofrAmt.out, ofrOutRate, QUALITY_ONE, /*roundUp*/ false);
+            }
+            if (grossOut)
+                ownerGives = *grossOut;
 
             auto const funds = offer.isFunded()
-                ? ownerGives  // Offer owner is issuer; they have unlimited funds
+                ? ownerGives  // Offer owner is IOU issuer; they have unlimited funds
                 : offers.ownerFunds();
 
-            // Only if CLOB offer
-            if (funds < ownerGives)
+            // Only a CLOB offer: an AMM offer is funded and its output rate is
+            // parity, so its gross-up always fits.
+            if (!grossOut || funds < ownerGives)
             {
-                // We already know offer.owner()!=offer.issueOut().account
+                // The owner isn't an IOU issuer (those are funded). An MPT
+                // issuer can be here: its funds are what it can still issue.
                 ownerGives = funds;
                 stpAmt.out = mulRatio(ownerGives, QUALITY_ONE, ofrOutRate, /*roundUp*/ false);
 
@@ -816,32 +850,85 @@ BookStep<TIn, TOut, TDerived>::forEachOffer(
                 // transaction outcomes, so it must be made under an amendment.
                 ofrAmt = offer.limitOut(ofrAmt, stpAmt.out, /*roundUp*/ false);
 
-                stpAmt.in = mulRatio(ofrAmt.in, ofrInRate, QUALITY_ONE, /*roundUp*/ true);
-            }
+                stpAmt.in = mulRatio(amtIn(ofrAmt.in), ofrInRate, QUALITY_ONE, /*roundUp*/ true);
 
-            // Limit offer's input if MPT, BookStep is the first step (an issuer
-            // is making a cross-currency payment), and this offer is not owned
-            // by the issuer. Otherwise, OutstandingAmount may overflow.
-            auto const& issuer = assetIn.getIssuer();
-            if (isAssetInMPT && !prevStep_ && offer.owner() != issuer)
-            {
-                // Funds available to issue
-                auto const available = toAmount<TIn>(accountFunds(
-                    sb,
-                    issuer,
-                    assetIn,  // STAmount{0}, but the default is not used
-                    FreezeHandling::IgnoreFreeze,
-                    AuthHandling::IgnoreAuth,
-                    j_));
-                if (stpAmt.in > available)
+                // Fee clip can floor in or out to 0. OfferStream is
+                // fee-blind, so it misses both: out==0 blocks the book;
+                // in==0 / out>0 consumes ownerGives for free. MPT at
+                // ordinary sizes; IOU only at the smallest out — V2
+                // because that IOU outcome changes.
+                if (sb.rules().enabled(featureMPTokensV2) &&
+                    (stpAmt.out <= beast::kZero || ofrAmt.in <= beast::kZero))
                 {
-                    limitStepIn(
-                        offer, ofrAmt, stpAmt, ownerGives, ofrInRate, ofrOutRate, available);
+                    removeOffer(
+                        "Removing offer whose fee-clipped amount rounds to "
+                        "zero");
+                    return true;
+                }
+
+                // out = floor(funds / rate), so out × rate <= funds and
+                // ceil(out × rate) <= funds since funds is an integer. Charge
+                // that instead of funds; charging all of funds would burn the
+                // fraction that can't be delivered. IOU keeps funds; the
+                // difference is sub-epsilon there.
+                if constexpr (std::is_same_v<TOut, MPTAmount>)
+                {
+                    ownerGives = mulRatio(stpAmt.out, ofrOutRate, QUALITY_ONE, /*roundUp*/ true);
                 }
             }
 
+            // Limit offer's input if MPT and the offer is not owned by the
+            // issuer (an issuer's send to itself is a no-op).
+            bool inLimited = false;
+            std::optional<TIn> limitIn;
+            auto const& issuer = assetIn.getIssuer();
+            if (isAssetInMPT && offer.owner() != issuer)
+            {
+                if (!prevStep_)
+                {
+                    // BookStep is the first step (an issuer is making a
+                    // cross-currency payment). Limit to the funds available to
+                    // issue, otherwise OutstandingAmount may overflow. This
+                    // limits the taker, not the offer: its remainder is still
+                    // funded by the owner, so the callback keeps it. With
+                    // nothing left to issue there is nothing to consume, so
+                    // stop before touching the offer.
+                    auto const available = toAmount<TIn>(accountFunds(
+                        sb,
+                        issuer,
+                        assetIn,  // STAmount{0}, but the default is not used
+                        FreezeHandling::IgnoreFreeze,
+                        AuthHandling::IgnoreAuth,
+                        j_));
+                    if (available <= beast::kZero)
+                        return false;
+                    if (stpAmt.in > available)
+                    {
+                        inLimited = true;
+                        limitIn = available;
+                    }
+                }
+                else if (maxIn_ && ofrAmt.in > *maxIn_)
+                {
+                    // Limit to MaximumAmount (see maxIn_). The remainder is
+                    // still funded, so the callback keeps the offer instead of
+                    // consuming it. stpAmt.in is already the grossed-up cap.
+                    inLimited = true;
+                    limitOfferIn(offer, ofrAmt, stpAmt, ownerGives, ofrOutRate, *maxIn_);
+                }
+            }
+            if (limitIn)
+                limitStepIn(offer, ofrAmt, stpAmt, ownerGives, ofrInRate, ofrOutRate, *limitIn);
+
+            // amtIn() grossed up no more than the cap, so the offer must have
+            // been limited to it above or the taker pays for less than is
+            // consumed.
+            XRPL_ASSERT(
+                !capInMPT || ofrAmt.in <= *maxIn_,
+                "xrpl::BookStep::forEachOffer : capped offer input is limited");
+
             offerAttempted = true;
-            return callback(offer, ofrAmt, stpAmt, ownerGives, ofrInRate, ofrOutRate);
+            return callback(offer, ofrAmt, stpAmt, ownerGives, ofrInRate, ofrOutRate, inLimited);
         }
         catch (std::overflow_error const&)
         {
@@ -876,7 +963,7 @@ BookStep<TIn, TOut, TDerived>::forEachOffer(
         // If offer crossing then use either LOB quality or nullopt
         // to prevent AMM being blocked by a lower quality LOB.
         auto const qualityThreshold = [&] -> std::optional<Quality> {
-            if (sb.rules().enabled(fixAMMv1_1) && lobQuality)
+            if (lobQuality)
                 return static_cast<TDerived const*>(this)->qualityThreshold(*lobQuality);
             return lobQuality;
         }();
@@ -1006,7 +1093,7 @@ BookStep<TIn, TOut, TDerived>::tip(ReadView const& view) const
     // as the result a LOB offer is partially crossed, and it might take a few
     // iterations to fully cross the offer.
     auto const qualityThreshold = [&] -> std::optional<Quality> {
-        if (view.rules().enabled(fixAMMv1_1) && lobQuality)
+        if (lobQuality)
             return static_cast<TDerived const*>(this)->qualityThreshold(*lobQuality);
         return std::nullopt;
     }();
@@ -1094,7 +1181,8 @@ BookStep<TIn, TOut, TDerived>::revImp(
                          TAmounts<TIn, TOut> const& stpAmt,
                          TOut const& ownerGives,
                          std::uint32_t transferRateIn,
-                         std::uint32_t transferRateOut) mutable -> bool {
+                         std::uint32_t transferRateOut,
+                         bool inLimited) mutable -> bool {
         if (remainingOut <= beast::kZero)
             return false;
 
@@ -1106,8 +1194,11 @@ BookStep<TIn, TOut, TDerived>::revImp(
             remainingOut = out - result.out;
             this->consumeOffer(sb, offer, ofrAmt, stpAmt, ownerGives);
             // return true b/c even if the payment is satisfied,
-            // we need to consume the offer
-            return true;
+            // we need to consume the offer. An offer limited by what the
+            // issuer can issue is not consumed, though: its remainder is still
+            // funded, and no more of that MPT can flow through this step
+            // anyway.
+            return !inLimited;
         }
 
         auto ofrAdjAmt = ofrAmt;
@@ -1210,7 +1301,8 @@ BookStep<TIn, TOut, TDerived>::fwdImp(
                          TAmounts<TIn, TOut> const& stpAmt,
                          TOut const& ownerGives,
                          std::uint32_t transferRateIn,
-                         std::uint32_t transferRateOut) mutable -> bool {
+                         std::uint32_t transferRateOut,
+                         bool inLimited) mutable -> bool {
         XRPL_ASSERT(cache_, "xrpl::BookStep::fwdImp::eachOffer : cache is set");
 
         if (remainingIn <= beast::kZero)
@@ -1240,8 +1332,10 @@ BookStep<TIn, TOut, TDerived>::fwdImp(
             savedInsAdj.insert(stpAmt.in);
             lastOut = savedOutsAdj.insert(stpAmt.out);
             resultAdj = TAmounts<TIn, TOut>(sum(savedInsAdj), sum(savedOutsAdj));
-            // consume the offer even if stepAmt.in == remainingIn
-            processMore = true;
+            // consume the offer even if stepAmt.in == remainingIn, unless it
+            // was limited by what the issuer can issue: its remainder is
+            // still funded and must stay on the book.
+            processMore = !inLimited;
         }
         else
         {

src/libxrpl/tx/paths/OfferStream.cpp

@@ -356,10 +356,10 @@ TOfferStreamBase<TIn, TOut>::step()
                 offer_ = TOffer<TIn, TOut>{};
                 continue;
             }
-            // The strict reduction only overflows for a crafted MPT offer, and
-            // MPT offers require featureMPTokensV2 (enforced at OfferCreate
-            // preflight). So the amendment is always enabled here and this
-            // legacy re-throw is unreachable in practice.
+            // The strict reduction only throws std::overflow_error for a
+            // crafted MPT offer, and MPT offers require featureMPTokensV2
+            // (enforced at OfferCreate preflight). So the amendment is always
+            // enabled here and this legacy re-throw is unreachable in practice.
             // LCOV_EXCL_START
             XRPL_ASSERT(
                 view_.rules().enabled(featureMPTokensV2),

src/libxrpl/tx/transactors/dex/AMMWithdraw.cpp

@@ -354,11 +354,8 @@ AMMWithdraw::applyGuts(Sandbox& sb)
 
     // Due to rounding, the LPTokenBalance of the last LP
     // might not match the LP's trustline balance
-    if (sb.rules().enabled(fixAMMv1_1))
-    {
-        if (auto const res = verifyAndAdjustLPTokenBalance(sb, lpTokens, ammSle, accountID_); !res)
-            return {res.error(), false};
-    }
+    if (auto const res = verifyAndAdjustLPTokenBalance(sb, lpTokens, ammSle, accountID_); !res)
+        return {res.error(), false};  // LCOV_EXCL_LINE
 
     auto const tfee = getTradingFee(ctx_.view(), *ammSle, accountID_);
 
@@ -591,7 +588,7 @@ AMMWithdraw::withdraw(
 
     // Should not happen since the only LP on last withdraw
     // has the balance set to the lp token trustline balance.
-    if (view.rules().enabled(fixAMMv1_1) && lpTokensWithdrawActual > lpTokensAMMBalance)
+    if (lpTokensWithdrawActual > lpTokensAMMBalance)
     {
         // LCOV_EXCL_START
         JLOG(journal.debug()) << "AMM Withdraw: failed to withdraw, unexpected LP tokens: "

src/libxrpl/tx/transactors/dex/OfferCreate.cpp

@@ -24,6 +24,7 @@
 #include <xrpl/protocol/Issue.h>
 #include <xrpl/protocol/Keylet.h>
 #include <xrpl/protocol/LedgerFormats.h>
+#include <xrpl/protocol/MPTAmount.h>
 #include <xrpl/protocol/MPTIssue.h>
 #include <xrpl/protocol/Protocol.h>
 #include <xrpl/protocol/Quality.h>
@@ -50,6 +51,7 @@
 #include <functional>
 #include <memory>
 #include <optional>
+#include <stdexcept>
 #include <tuple>
 #include <utility>
 
@@ -413,19 +415,47 @@ OfferCreate::flowCross(
         // offer taker.  Set sendMax to allow for the gateway's cut.
         Rate gatewayXferRate{QUALITY_ONE};
         STAmount sendMax = takerAmount.in;
+        // Payment flow code compares quality after the transfer rate is
+        // included, so the threshold is computed from the grossed-up input.
+        STAmount thresholdIn = sendMax;
         if (!sendMax.native() && (accountID_ != sendMax.getIssuer()))
         {
             gatewayXferRate = transferRate(psb, sendMax);
             if (gatewayXferRate.value != QUALITY_ONE)
             {
-                sendMax =
-                    multiplyRound(takerAmount.in, gatewayXferRate, takerAmount.in.asset(), true);
+                try
+                {
+                    sendMax = multiplyRound(
+                        takerAmount.in, gatewayXferRate, takerAmount.in.asset(), true);
+                    thresholdIn = sendMax;
+                }
+                catch (std::overflow_error const&)
+                {
+                    // Only an MPT amount can overflow here (IOU rescales and
+                    // XRP has no transfer rate), and MPT offers require
+                    // featureMPTokensV2 at preflight, so this legacy re-throw
+                    // is unreachable in practice.
+                    // LCOV_EXCL_START
+                    if (!takerAmount.in.holds<MPTIssue>() ||
+                        !psb.rules().enabled(featureMPTokensV2))
+                        throw;
+                    // LCOV_EXCL_STOP
+
+                    // The grossed-up MPT amount exceeds 2^63-1. The taker can't
+                    // send more than its balance anyway. The threshold only
+                    // needs the ratio, so compute it as an IOU, which can't
+                    // overflow.
+                    sendMax = inStartBalance;
+                    thresholdIn = multiplyRound(
+                        STAmount{noIssue(), takerAmount.in.mantissa()},
+                        gatewayXferRate,
+                        noIssue(),
+                        true);
+                }
             }
         }
 
-        // Payment flow code compares quality after the transfer rate is
-        // included.  Since transfer rate is incorporated compute threshold.
-        Quality threshold{takerAmount.out, sendMax};
+        Quality threshold{takerAmount.out, thresholdIn};
 
         // If we're creating a passive offer adjust the threshold so we only
         // cross offers that have a better quality than this one.
@@ -870,15 +900,32 @@ OfferCreate::applyGuts(Sandbox& sb, Sandbox& sbCancel)
         return {tesSUCCESS, true};
     }
 
+    // A taker redeeming an MPT into this offer pays the transfer fee, and
+    // BookStep grosses up TakerPays by the rate before anything else. If that
+    // doesn't fit in an MPT amount, every fee-paying taker overflows and
+    // BookStep removes the offer on the first attempt (the issuer pays no fee,
+    // but its send is bounded by what it can still issue). Conservative for a
+    // bid above MaximumAmount, which BookStep grosses up only to the cap.
+    // Checked on the remainder: it may fit even if the original amount didn't.
+    bool cannotRest = false;
+    if (mptV2 && saTakerPays.holds<MPTIssue>())
+    {
+        auto const rate = transferRate(sb, saTakerPays);
+        cannotRest = rate != kParityRate &&
+            !tryMulRatio(saTakerPays.mpt(), rate.value, QUALITY_ONE, /*roundUp*/ true);
+    }
+
     // The remainder rests at uRate, the original pre-crossing rate. A zero
     // rate (quality not representable) puts it in the directory whose index
     // equals getBookBase(book), and BookTip scans keys strictly greater, so it
-    // could never be crossed while holding the owner's reserve. Don't place
-    // it; anything that crossed is kept, and a fully crossed offer has already
-    // returned above. Gated to preserve pre-amendment behavior.
-    if (mptV2 && uRate == 0)
+    // could never be crossed while holding the owner's reserve. Likewise, a
+    // bid whose fee-grossed TakerPays doesn't fit would be removed by BookStep
+    // on the first take. Don't place it; anything that crossed is kept, and a
+    // fully crossed offer has already returned above. Gated to preserve
+    // pre-amendment behavior.
+    if ((mptV2 && uRate == 0) || cannotRest)
     {
-        JLOG(j_.debug()) << "Unrepresentable quality: remainder not placed";
+        JLOG(j_.debug()) << "Unrepresentable quality or fee: remainder not placed";
         if (!crossed)
             return {tecKILLED, false};
         return {tesSUCCESS, true};

src/libxrpl/tx/transactors/lending/LoanBrokerCoverClawback.cpp

@@ -8,6 +8,7 @@
 #include <xrpl/ledger/ReadView.h>
 #include <xrpl/ledger/helpers/LendingHelpers.h>
 #include <xrpl/ledger/helpers/TokenHelpers.h>
+#include <xrpl/ledger/helpers/VaultHelpers.h>
 #include <xrpl/protocol/AccountID.h>
 #include <xrpl/protocol/Asset.h>
 #include <xrpl/protocol/Concepts.h>
@@ -158,7 +159,7 @@ determineAsset(
 
 std::expected<STAmount, TER>
 determineClawAmount(
-    SLE const& sleBroker,
+    SLE::ConstRef sleBroker,
     Asset const& vaultAsset,
     std::optional<STAmount> const& amount,
     SLE::ConstRef vaultSle,
@@ -169,17 +170,19 @@ determineClawAmount(
             if (rules.enabled(fixCleanup3_2_0))
             {
                 return minimumBrokerCover(
-                    sleBroker[sfDebtTotal], TenthBips32(sleBroker[sfCoverRateMinimum]), vaultSle);
+                    sleBroker->at(sfDebtTotal),
+                    TenthBips32(sleBroker->at(sfCoverRateMinimum)),
+                    vaultSle);
             }
 
             // Always round the minimum required up
             NumberRoundModeGuard const mg(Number::RoundingMode::Upward);
             return tenthBipsOfValue(
-                sleBroker[sfDebtTotal], TenthBips32(sleBroker[sfCoverRateMinimum]));
+                sleBroker->at(sfDebtTotal), TenthBips32(sleBroker->at(sfCoverRateMinimum)));
         }();
         // The subtraction probably won't round, but round down if it does.
         NumberRoundModeGuard const mg(Number::RoundingMode::Downward);
-        return sleBroker[sfCoverAvailable] - minRequiredCover;
+        return sleBroker->at(sfCoverAvailable) - minRequiredCover;
     }();
     if (maxClawAmount <= beast::kZero)
         return std::unexpected(tecINSUFFICIENT_FUNDS);
@@ -187,12 +190,23 @@ determineClawAmount(
     // Use the vaultAsset here, because it will be the right type in all
     // circumstances. The amount may be an IOU indicating the pseudo-account's
     // asset, which is correct, but not what is needed here.
-    if (!amount || *amount == beast::kZero)
-        return STAmount{vaultAsset, maxClawAmount};
-    Number const magnitude{*amount};
-    if (magnitude > maxClawAmount)
-        return STAmount{vaultAsset, maxClawAmount};
-    return STAmount{vaultAsset, magnitude};
+    STAmount requested = [&] {
+        if (!amount || *amount == beast::kZero)
+            return STAmount{vaultAsset, maxClawAmount};
+        Number const magnitude{*amount};
+        if (magnitude > maxClawAmount)
+            return STAmount{vaultAsset, maxClawAmount};
+        return STAmount{vaultAsset, magnitude};
+    }();
+
+    if (getVaultVersion(vaultSle) != VaultVersion::FixedPrecision)
+        return requested;
+
+    STAmount rounded = debitToPosteriorBrokerCoverScale(
+        vaultSle, sleBroker, requested, Number::RoundingMode::TowardsZero);
+    if (rounded == beast::kZero)
+        return std::unexpected(tecPRECISION_LOSS);
+    return rounded;
 }
 
 template <ValidIssueType T>
@@ -294,17 +308,25 @@ LoanBrokerCoverClawback::preclaim(PreclaimContext const& ctx)
     }
 
     auto const findClawAmount =
-        determineClawAmount(*sleBroker, vaultAsset, amount, vault, ctx.view.rules());
+        determineClawAmount(sleBroker, vaultAsset, amount, vault, ctx.view.rules());
     if (!findClawAmount)
     {
-        JLOG(ctx.j.warn()) << "LoanBroker cover is already at minimum.";
+        JLOG(ctx.j.warn()) << "LoanBroker cover is already at minimum, or the claw amount "
+                              "rounds to zero: "
+                           << transToken(findClawAmount.error());
         return findClawAmount.error();
     }
     STAmount const& clawAmount = *findClawAmount;
 
-    if (auto const ret = canApplyToBrokerCover(
-            ctx.view, sleBroker, vaultAsset, clawAmount, ctx.j, "LoanBrokerCoverClawback"))
-        return ret;
+    // FixedPrecision outflows already rounded at the posterior exponent; the
+    // live CoverAvailable scale used by canApplyToBrokerCover would reject a
+    // re-fining clawback as sub-ULP.
+    if (getVaultVersion(vault) != VaultVersion::FixedPrecision)
+    {
+        if (auto const ret = canApplyToBrokerCover(
+                ctx.view, sleBroker, vaultAsset, clawAmount, ctx.j, "LoanBrokerCoverClawback"))
+            return ret;
+    }
 
     // Explicitly check the balance of the trust line / MPT to make sure the
     // balance is actually there. It should always match `sfCoverAvailable`, so
@@ -357,7 +379,7 @@ LoanBrokerCoverClawback::doApply()
     auto const vaultAsset = vault->at(sfAsset);
 
     auto const findClawAmount =
-        determineClawAmount(*sleBroker, vaultAsset, amount, vault, view().rules());
+        determineClawAmount(sleBroker, vaultAsset, amount, vault, view().rules());
     if (!findClawAmount)
         return tecINTERNAL;  // LCOV_EXCL_LINE
     STAmount const& clawAmount = *findClawAmount;

src/libxrpl/tx/transactors/lending/LoanBrokerCoverDeposit.cpp

@@ -5,8 +5,10 @@
 #include <xrpl/beast/utility/Zero.h>
 #include <xrpl/ledger/helpers/LendingHelpers.h>
 #include <xrpl/ledger/helpers/TokenHelpers.h>
+#include <xrpl/ledger/helpers/VaultHelpers.h>
 #include <xrpl/protocol/Feature.h>
 #include <xrpl/protocol/Indexes.h>
+#include <xrpl/protocol/Protocol.h>
 #include <xrpl/protocol/SField.h>
 #include <xrpl/protocol/STAmount.h>
 #include <xrpl/protocol/STLedgerEntry.h>
@@ -104,22 +106,35 @@ LoanBrokerCoverDeposit::preclaim(PreclaimContext const& ctx)
     // here in preclaim lets  us reject sub-cover-scale dust early with tecPRECISION_LOSS instead of
     // failing only in  doApply.
     auto const roundedAmount = [&] -> STAmount {
+        if (getVaultVersion(vault) == VaultVersion::FixedPrecision)
+        {
+            // Cover deposit is an inflow to CoverAvailable, so it must floor
+            // the sum, not just the delta.
+            return creditToPosteriorBrokerCoverScale(
+                vault, sleBroker, amount, Number::RoundingMode::Downward);
+        }
         if (!fix320Enabled)
-            return tx[sfAmount];
+            return STAmount{amount};
 
         return roundToScale(
-            tx[sfAmount],
+            amount,
             scale(sleBroker->at(sfCoverAvailable), vaultAsset),
             Number::RoundingMode::Downward);
     }();
 
-    if (fix320Enabled && roundedAmount == beast::kZero)
+    // fixCleanup3_2_0 is enabled on the network, so this also covers the
+    // FixedPrecision zero-credit case.
+    if (fix320Enabled && roundedAmount <= beast::kZero)
     {
-        JLOG(ctx.j.warn()) << "LoanBrokerCoverDeposit: deposit amount: " << tx[sfAmount]
-                           << " is zero at loan broker scale";
+        JLOG(ctx.j.warn()) << "LoanBrokerCoverDeposit: deposit amount: " << amount
+                           << " is zero or negative at loan broker scale";
         return tecPRECISION_LOSS;
     }
 
+    if (auto const ter = checkOptionalBrokerCoverInflow(vault, sleBroker, roundedAmount);
+        !isTesSuccess(ter))
+        return ter;
+
     if (accountHolds(
             ctx.view,
             account,
@@ -155,6 +170,13 @@ LoanBrokerCoverDeposit::doApply()
     // see the rationale comment in preclaim.
     bool const fix320Enabled = view().rules().enabled(fixCleanup3_2_0);
     auto const amount = [&] -> STAmount {
+        if (getVaultVersion(vault) == VaultVersion::FixedPrecision)
+        {
+            // Cover deposit is an inflow to CoverAvailable, so it must floor
+            // the sum, not just the delta.
+            return creditToPosteriorBrokerCoverScale(
+                vault, broker, tx[sfAmount], Number::RoundingMode::Downward);
+        }
         if (!fix320Enabled)
             return tx[sfAmount];
 
@@ -164,12 +186,12 @@ LoanBrokerCoverDeposit::doApply()
             Number::RoundingMode::Downward);
     }();
 
-    // We validated zero-amount in preclaim, if we ended up with zero now, fail hard.
-    if (amount == beast::kZero)
+    // We validated zero-or-negative amount in preclaim, if we ended up with one now, fail hard.
+    if (amount <= beast::kZero)
     {
         // LCOV_EXCL_START
         JLOG(j_.error()) << "LoanBrokerCoverDeposit: deposit amount: " << tx[sfAmount]
-                         << " is zero";
+                         << " is zero or negative";
         return tecINTERNAL;
         // LCOV_EXCL_STOP
     }

src/libxrpl/tx/transactors/lending/LoanBrokerCoverWithdraw.cpp

@@ -8,6 +8,7 @@
 #include <xrpl/ledger/helpers/CredentialHelpers.h>
 #include <xrpl/ledger/helpers/LendingHelpers.h>
 #include <xrpl/ledger/helpers/TokenHelpers.h>
+#include <xrpl/ledger/helpers/VaultHelpers.h>
 #include <xrpl/protocol/Feature.h>
 #include <xrpl/protocol/Indexes.h>
 #include <xrpl/protocol/Protocol.h>
@@ -103,10 +104,28 @@ LoanBrokerCoverWithdraw::preclaim(PreclaimContext const& ctx)
     if (amount.asset() != vaultAsset)
         return tecWRONG_ASSET;
 
-    // Helper handles both IOU and MPT correctly without explicit branching.
-    if (auto const ret = canApplyToBrokerCover(
-            ctx.view, sleBroker, vaultAsset, amount, ctx.j, "LoanBrokerCoverWithdraw"))
-        return ret;
+    STAmount roundedAmount{amount};
+    if (getVaultVersion(vault) == VaultVersion::FixedPrecision)
+    {
+        // FixedPrecision outflows are rounded at the posterior exponent here
+        // instead of going through canApplyToBrokerCover: the live
+        // CoverAvailable scale it uses would reject a re-fining withdrawal as
+        // sub-ULP.
+        roundedAmount = debitToPosteriorBrokerCoverScale(
+            vault, sleBroker, amount, Number::RoundingMode::TowardsZero);
+        if (roundedAmount == beast::kZero)
+        {
+            JLOG(ctx.j.warn()) << "LoanBrokerCoverWithdraw: withdraw amount: " << amount
+                               << " is zero at loan broker scale";
+            return tecPRECISION_LOSS;
+        }
+    }
+    else
+    {
+        if (auto const ret = canApplyToBrokerCover(
+                ctx.view, sleBroker, vaultAsset, roundedAmount, ctx.j, "LoanBrokerCoverWithdraw"))
+            return ret;
+    }
 
     // The broker's pseudo-account is the source of funds.
     auto const pseudoAccountID = sleBroker->at(sfAccount);
@@ -129,7 +148,15 @@ LoanBrokerCoverWithdraw::preclaim(PreclaimContext const& ctx)
     AuthType authType = AuthType::WeakAuth;
     if (account != dstAcct)
     {
-        if (auto const ret = canWithdraw(ctx.view, tx))
+        // Check the amount actually sent: on FixedPrecision it is the rounded
+        // amount, not sfAmount.
+        if (auto const ret = canWithdraw(
+                ctx.view,
+                account,
+                dstAcct,
+                roundedAmount,
+                tx.isFieldPresent(sfDestinationTag),
+                tx[~sfCredentialIDs]))
             return ret;
 
         // The destination account must have consented to receive the asset by
@@ -184,9 +211,9 @@ LoanBrokerCoverWithdraw::preclaim(PreclaimContext const& ctx)
             tenthBipsOfValue(currentDebtTotal, TenthBips32(sleBroker->at(sfCoverRateMinimum))),
             scale(currentDebtTotal, vaultAsset));
     }();
-    if (coverAvail < amount)
+    if (coverAvail < roundedAmount)
         return tecINSUFFICIENT_FUNDS;
-    if ((coverAvail - amount) < minimumCover)
+    if ((coverAvail - roundedAmount) < minimumCover)
         return tecINSUFFICIENT_FUNDS;
 
     auto const freezeHandling = fix330Enabled && dstAcct == vaultAsset.getIssuer()
@@ -199,7 +226,7 @@ LoanBrokerCoverWithdraw::preclaim(PreclaimContext const& ctx)
             vaultAsset,
             freezeHandling,
             AuthHandling::ZeroIfUnauthorized,
-            ctx.j) < amount)
+            ctx.j) < roundedAmount)
         return tecINSUFFICIENT_FUNDS;
 
     return tesSUCCESS;
@@ -211,7 +238,7 @@ LoanBrokerCoverWithdraw::doApply()
     auto const& tx = ctx_.tx;
 
     auto const brokerID = tx[sfLoanBrokerID];
-    auto const amount = tx[sfAmount];
+    auto const requestedAmount = tx[sfAmount];
     auto const dstAcct = tx[~sfDestination].value_or(accountID_);
 
     auto const broker = view().peek(keylet::loanBroker(brokerID));
@@ -223,6 +250,10 @@ LoanBrokerCoverWithdraw::doApply()
         return tecINTERNAL;  // LCOV_EXCL_LINE
 
     auto const vaultAsset = vault->at(sfAsset);
+    auto const amount = getVaultVersion(vault) == VaultVersion::FixedPrecision
+        ? debitToPosteriorBrokerCoverScale(
+              vault, broker, requestedAmount, Number::RoundingMode::TowardsZero)
+        : requestedAmount;
 
     auto const brokerPseudoID = *broker->at(sfAccount);
 
@@ -239,6 +270,7 @@ LoanBrokerCoverWithdraw::doApply()
         brokerPseudoID,
         preFeeBalance_,
         amount,
+        amount,
         j_);
 }
 

src/libxrpl/tx/transactors/lending/LoanBrokerDelete.cpp

@@ -6,6 +6,7 @@
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/ledger/helpers/LendingHelpers.h>
 #include <xrpl/ledger/helpers/TokenHelpers.h>
+#include <xrpl/ledger/helpers/VaultHelpers.h>
 #include <xrpl/protocol/Asset.h>
 #include <xrpl/protocol/Feature.h>
 #include <xrpl/protocol/Indexes.h>
@@ -77,7 +78,7 @@ LoanBrokerDelete::preclaim(PreclaimContext const& ctx)
     {
         // Any remaining debt should have been wiped out by the last Loan
         // Delete. This check is purely defensive.
-        auto const scale = getAssetsTotalScale(vault);
+        auto const scale = getVaultScale(vault);
 
         auto const rounded =
             roundToAsset(asset, debtTotal, scale, Number::RoundingMode::TowardsZero);
@@ -94,21 +95,38 @@ LoanBrokerDelete::preclaim(PreclaimContext const& ctx)
 
     auto const coverAvailable = STAmount{asset, sleBroker->at(sfCoverAvailable)};
     // If there are assets in the cover, broker will receive them on deletion.
-    // So we need to check if the broker owner is deep frozen for that asset.
     if (coverAvailable > beast::kZero)
     {
+        auto const brokerPseudo = sleBroker->at(sfAccount);
+
+        // Pre-fixCleanup3_5_0: only freeze checks apply to the cover payout.
+        // Post-fixCleanup3_5_0: apply the cover-withdraw transfer and authorization checks too.
+        if (ctx.view.rules().enabled(fixCleanup3_5_0))
+        {
+            // Like a cover withdrawal, the payout skips the lsfMPTCanTransfer check so that an
+            // issuer cannot trap the broker's cover.
+            if (auto const ret = canTransfer(
+                    ctx.view, asset, brokerPseudo, brokerOwner, WaiveMPTCanTransfer::Yes))
+                return ret;
+
+            if (auto const ret = requireAuth(ctx.view, asset, brokerOwner, AuthType::WeakAuth))
+                return ret;
+
+            if (!holdingExists(ctx.view, brokerOwner, asset))
+            {
+                if (auto const ret = canAddHolding(ctx.view, asset); !isTesSuccess(ret))
+                    return ret;
+            }
+        }
+
         if (auto const ret = checkDeepFrozen(ctx.view, brokerOwner, asset))
         {
             JLOG(ctx.j.warn()) << "Broker owner account is frozen.";
             return ret;
         }
-    }
 
-    if (ctx.view.rules().enabled(fixCleanup3_2_0))
-    {
-        if (coverAvailable > beast::kZero)
+        if (ctx.view.rules().enabled(fixCleanup3_2_0))
         {
-            auto const brokerPseudo = sleBroker->at(sfAccount);
             if (auto const ret = checkFrozen(ctx.view, brokerPseudo, asset))
             {
                 JLOG(ctx.j.warn()) << "Broker pseudo-account is frozen/locked.";
@@ -151,8 +169,36 @@ LoanBrokerDelete::doApply()
         return tefBAD_LEDGER;  // LCOV_EXCL_LINE
     }
 
+    auto const owner = view().peek(keylet::account(accountID_));
+    if (!owner)
+        return tefBAD_LEDGER;  // LCOV_EXCL_LINE
+
+    // Pre-fixCleanup3_5_0: the owner count drops after the pseudo-account is erased.
+    // Post-fixCleanup3_5_0: it drops first, so the owner's holding created below can use the
+    // reserve that the broker frees.
+    bool const fix350Enabled = view().rules().enabled(fixCleanup3_5_0);
+    if (fix350Enabled)
+    {
+        // Decreases the owner count by two: one for the LoanBroker object, and one
+        // for the pseudo-account.
+        decreaseOwnerCountForObject(view(), owner, broker, 2, j_);
+    }
+
     {
         auto const coverAvailable = STAmount{vaultAsset, broker->at(sfCoverAvailable)};
+
+        // Pre-fixCleanup3_5_0: the cover goes straight to accountSend, so an MPT payout to an
+        // owner with no MPToken fails with tecNO_AUTH.
+        // Post-fixCleanup3_5_0: a nonzero cover first gets the owner a holding if it has none, as a
+        // withdrawal to self does.
+        if (fix350Enabled && coverAvailable > beast::kZero &&
+            !holdingExists(view(), accountID_, vaultAsset))
+        {
+            if (auto const ter = addEmptyHolding(
+                    ctx_.getApplyViewContext(), accountID_, preFeeBalance_, vaultAsset, j_))
+                return ter;
+        }
+
         if (auto const ter = accountSend(
                 view(), brokerPseudoID, accountID_, coverAvailable, j_, {}, WaiveTransferFee::Yes))
             return ter;
@@ -185,15 +231,8 @@ LoanBrokerDelete::doApply()
 
     view().erase(brokerPseudoSLE);
 
-    {
-        auto const owner = view().peek(keylet::account(accountID_));
-        if (!owner)
-            return tefBAD_LEDGER;  // LCOV_EXCL_LINE
-
-        // Decreases the owner count by two: one for the LoanBroker object, and
-        // one for the pseudo-account.
+    if (!fix350Enabled)
         decreaseOwnerCountForObject(view(), owner, broker, 2, j_);
-    }
 
     view().erase(broker);
 

src/libxrpl/tx/transactors/lending/LoanBrokerSet.cpp

@@ -232,7 +232,9 @@ LoanBrokerSet::preclaim(PreclaimContext const& ctx)
     {
         if (auto const value = tx[field]; value &&
             ((fix350Enabled && !isRepresentable(asset, *value)) ||
-             STAmount{asset, *value} != *value))
+             STAmount{asset, *value} != *value ||
+             (getVaultVersion(sleVault) == VaultVersion::FixedPrecision &&
+              !isOnVaultBaseGrid(asset, *value, getVaultBaseScale(sleVault)))))
         {
             JLOG(ctx.j.warn()) << field.f->getName() << " (" << *value
                                << ") can not be represented as a(n) " << to_string(asset) << ".";

src/libxrpl/tx/transactors/lending/LoanDelete.cpp

@@ -6,6 +6,7 @@
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/ledger/helpers/LendingHelpers.h>
+#include <xrpl/ledger/helpers/VaultHelpers.h>
 #include <xrpl/protocol/Indexes.h>
 #include <xrpl/protocol/SField.h>
 #include <xrpl/protocol/STAmount.h>  // IWYU pragma: keep
@@ -120,7 +121,7 @@ LoanDelete::doApply()
                 roundToAsset(
                     vaultSle->at(sfAsset),
                     debtTotalProxy,
-                    getAssetsTotalScale(vaultSle),
+                    getVaultScale(vaultSle),
                     Number::RoundingMode::TowardsZero) == beast::kZero,
                 "xrpl::LoanDelete::doApply",
                 "last loan, remaining debt rounds to zero");