diff --git a/.gitignore b/.gitignore
index c5af8eb7b4..5b21076af3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -72,11 +72,16 @@ DerivedData
 /.zed/
 
 # AI tools.
+# Shared/committable AI agent config (AGENTS.md, CLAUDE.md, GEMINI.md, .claude/settings.json,
+# tool-specific rules files, etc.) should be checked in — see CONTRIBUTING.md. Only the
+# personal/local variants below are ignored.
 /.agent
 /.agents
 /.augment
-/.claude
-/CLAUDE.md
+/.claude/settings.local.json
+AGENTS.override.md
+CLAUDE.local.md
+GEMINI.local.md
 
 # Python
 __pycache__
diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 0000000000..85bf9befb2
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,42 @@
+# AGENTS.md
+
+This file provides guidance to AI coding agents (Claude Code, and other AGENTS.md-compatible tools) when working with code in this repository.
+
+## Build
+
+Required on Linux/macOS: use the Nix devshell, which sets up the compiler, Conan, ccache, and (optionally) Rust automatically.
+
+```bash
+nix develop
+```
+
+For alternate devshell variants (specific compiler, no-compiler, coverage), see [docs/build/nix.md](./docs/build/nix.md). For the manual build steps, CMake options, and protocol codegen commands, see [BUILD.md](./BUILD.md) (`## Steps`, `## Options`, `## Code generation`).
+
+Rust crate tests (independent of the CMake build): `cargo test --manifest-path crates/Cargo.toml --workspace` (CI uses `cargo nextest`).
+
+## Testing
+
+Unit tests are a custom framework built into the `xrpld` binary itself (not Boost.Test/GTest/Catch); see [CONTRIBUTING.md](./CONTRIBUTING.md#unit-tests) for the basic invocation. Notes not covered there:
+
+- A suite's `--unittest` name is built from the arguments to its `BEAST_DEFINE_TESTSUITE`/`BEAST_DEFINE_TESTSUITE_PRIO` macro (usually at the bottom of the test file), in reverse order and joined with `.`: `BEAST_DEFINE_TESTSUITE(Credentials, app, xrpl)` → `xrpl.app.Credentials`.
+- `--unittest-arg` does nothing — don't use it.
+- Tests that run offline in under a minute should be automatic `--unittest` suites; anything else is a manual/integration test.
+- New tests should be written using `gtest` under `src/tests/` unless that isn't possible, in which case fall back to the legacy Beast framework under `src/test/`. `tests/` (top-level) holds integration tests exercised against `libxrpl`/`xrpld`.
+
+## Lint/Format
+
+See [CONTRIBUTING.md](./CONTRIBUTING.md#pre-commit-hooks) for `pre-commit` setup and [CONTRIBUTING.md](./CONTRIBUTING.md#clang-tidy) for `clang-tidy` (opt-in, needs local `clang-tidy` and generated headers).
+
+## Code Style
+
+New file placement and header levelization: see [CONTRIBUTING.md](./CONTRIBUTING.md#before-making-a-pull-request). Braces, whitespace, member order, and other conventions: see [docs/CodingStyle.md](./docs/CodingStyle.md). `XRPL_ASSERT`/`UNREACHABLE` contracts: see [CONTRIBUTING.md](./CONTRIBUTING.md#contracts-and-instrumentation). Commit messages: see [CONTRIBUTING.md](./CONTRIBUTING.md#good-commit-messages).
+
+## Architecture
+
+Paths below reflect the current layout; update this section if modularization moves a subsystem to a different directory.
+
+- `include/xrpl/` + `src/libxrpl/` — the core protocol library: ledger, shamap, consensus, crypto, json, resource, nodestore, rdb, peerfinder, and `tx/` (transaction application: `Transactor.cpp`, `applySteps.cpp`, invariants, payment paths). `tx/transactors/` has one file per transaction type, grouped by subsystem: `escrow/`, `vault/`, `lending/`, `sponsor/`, `nft/`, `token/` (MPT), `payment_channel/`, `permissioned_domain/`, `dex/`, `oracle/`, `did/`, `credentials/`, `bridge/`, `check/`, `delegate/`, `account/`, `system/`. Any change to transaction-processing behavior must be gated behind an Amendment.
+- `src/xrpld/` — the server application built on top of `libxrpl`: `app`, `core`, `overlay` (P2P networking), `peerfinder`, `perflog`, `rpc`, `shamap`. `main` builds an `ApplicationImp` implementing `Application`; most components hold a reference to it (`app_`), giving broad cross-component access — expect to trace call chains through `Application&`.
+- `src/test/` — unit tests mirroring the subsystems above, plus `jtx/` (the transaction-building test DSL — e.g. `jtx/escrow.h`, `jtx/vault.h`, `jtx/sponsor.h`, `jtx/permissioned_dex.h`) and `unit_test/` (the custom test framework itself, derived from Beast).
+- `src/tests/` — unit tests for `libxrpl` written in `gtest`, gradually replacing the `src/test` equivalents.
+- `crates/` — a Rust workspace (only built with `-Dxrpld -Drust=ON`) bridged into C++ via `cxxbridge`/the `cxx` crate; currently just a `hello_world` interop scaffold. Requires the Rust toolchain pinned in `rust-toolchain.toml` (the Nix devshell provides it automatically).
diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 120000
index 0000000000..47dc3e3d86
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1 @@
+AGENTS.md
\ No newline at end of file
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 35309a9824..1035124f31 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -59,6 +59,17 @@ to an existing XLS. Neither change will be released (in an amendment's
 case, marked as `Supported::yes`) until the corresponding XLS's status
 is `Final`.
 
+## AI coding agents
+
+[`AGENTS.md`](./AGENTS.md) (and its `CLAUDE.md` symlink, for Claude Code) holds shared, checked-in guidance for AI coding agents working in this repository — build/test/lint commands and architecture notes. Additional `AGENTS.md` files may exist in subdirectories to give agents context specific to that part of the codebase; whenever you add one, also add a `CLAUDE.md` symlink pointing to it (`ln -s AGENTS.md CLAUDE.md`) so Claude Code picks it up too.
+
+If you want to give an agent personal instructions that shouldn't be shared with other contributors (e.g. your own workflow preferences), those are gitignored, not checked in:
+
+- `CLAUDE.local.md` — read by Claude Code alongside `CLAUDE.md`.
+- `AGENTS.override.md` — read by AGENTS.md-compatible tools that support a personal override file layered on top of `AGENTS.md`.
+
+Likewise, `.claude/settings.local.json` is for personal, untracked Claude Code settings, while `.claude/settings.json` is shared.
+
 ## Before making a pull request
 
 (Or marking a draft pull request as ready.)
@@ -82,7 +93,7 @@ If you create new source files, they must be organized as follows:
   under `include/xrpl`, and source (`.cpp`) files must go under
   `src/libxrpl`.
 - All other non-test files must go under `src/xrpld`.
-- All test source files must go under `src/test`.
+- New test source files should use `gtest` and go under `src/tests`, unless that isn't possible, in which case they should use our legacy test framework and go under `src/test`.
 - All benchmark source files must go under `src/benchmarks`.
 
 The source must be formatted according to the style guide below. The easiest
diff --git a/src/libxrpl/tx/AGENTS.md b/src/libxrpl/tx/AGENTS.md
new file mode 100644
index 0000000000..e2261fc1ad
--- /dev/null
+++ b/src/libxrpl/tx/AGENTS.md
@@ -0,0 +1,5 @@
+# AGENTS.md — tx
+
+See the repo-level [AGENTS.md](../../../AGENTS.md) for general build/test/style guidance.
+
+Any change to transaction-processing behavior must be gated behind an amendment. New amendments (and fixes, i.e. `fix*` amendments) are added to [`include/xrpl/protocol/detail/features.macro`](../../../include/xrpl/protocol/detail/features.macro), as an `XRPL_FEATURE(...)` or `XRPL_FIX(...)` entry added to the top of the list (the list is kept in reverse chronological order). Once the pre-amendment code path for a retired amendment is removed, move its entry to `XRPL_RETIRE_FEATURE(...)`/`XRPL_RETIRE_FIX(...)` instead of deleting it.
diff --git a/src/libxrpl/tx/CLAUDE.md b/src/libxrpl/tx/CLAUDE.md
new file mode 120000
index 0000000000..47dc3e3d86
--- /dev/null
+++ b/src/libxrpl/tx/CLAUDE.md
@@ -0,0 +1 @@
+AGENTS.md
\ No newline at end of file
diff --git a/src/xrpld/rpc/AGENTS.md b/src/xrpld/rpc/AGENTS.md
new file mode 100644
index 0000000000..14fdd7a03e
--- /dev/null
+++ b/src/xrpld/rpc/AGENTS.md
@@ -0,0 +1,5 @@
+# AGENTS.md — rpc
+
+See the repo-level [AGENTS.md](../../../AGENTS.md) for general build/test/style guidance.
+
+Any change to a public RPC method's behavior (new/changed/removed fields, parameters, or error conditions) needs a corresponding entry in [`API-CHANGELOG.md`](../../../API-CHANGELOG.md), under the `## Unreleased` section (`### Additions`, `### Deprecations`, etc. as appropriate).
diff --git a/src/xrpld/rpc/CLAUDE.md b/src/xrpld/rpc/CLAUDE.md
new file mode 120000
index 0000000000..47dc3e3d86
--- /dev/null
+++ b/src/xrpld/rpc/CLAUDE.md
@@ -0,0 +1 @@
+AGENTS.md
\ No newline at end of file