Fix shared_ptr reference cycle causing ASAN leaks in CoroTaskRunner

After a coroutine completes, the frame remains alive holding a captured
shared_ptr<CoroTaskRunner> back to its owner. This creates an unreachable
cycle: runner -> task_ -> frame -> shared_ptr<runner>.

Break the cycle in resume() by destroying the coroutine frame (task_ = {})
and the stored callable when the coroutine is done. Also fix runnable() to
handle the null-handle state after cleanup.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.clang-tidy

@@ -1,105 +1,143 @@
 ---
 Checks: "-*,
-  bugprone-argument-comment
+  bugprone-argument-comment,
+  bugprone-assert-side-effect,
+  bugprone-bad-signal-to-kill-thread,
+  bugprone-bool-pointer-implicit-conversion,
+  bugprone-casting-through-void,
+  bugprone-chained-comparison,
+  bugprone-compare-pointer-to-member-virtual-function,
+  bugprone-copy-constructor-init,
+  bugprone-dangling-handle,
+  bugprone-dynamic-static-initializers,
+  bugprone-fold-init-type,
+  bugprone-forward-declaration-namespace,
+  bugprone-inaccurate-erase,
+  bugprone-incorrect-enable-if,
+  bugprone-incorrect-roundings,
+  bugprone-infinite-loop,
+  bugprone-integer-division,
+  bugprone-lambda-function-name,
+  bugprone-macro-parentheses,
+  bugprone-macro-repeated-side-effects,
+  bugprone-misplaced-operator-in-strlen-in-alloc,
+  bugprone-misplaced-pointer-arithmetic-in-alloc,
+  bugprone-misplaced-widening-cast,
+  bugprone-multi-level-implicit-pointer-conversion,
+  bugprone-multiple-new-in-one-expression,
+  bugprone-multiple-statement-macro,
+  bugprone-no-escape,
+  bugprone-non-zero-enum-to-bool-conversion,
+  bugprone-parent-virtual-call,
+  bugprone-posix-return,
+  bugprone-redundant-branch-condition,
+  bugprone-shared-ptr-array-mismatch,
+  bugprone-signal-handler,
+  bugprone-signed-char-misuse,
+  bugprone-sizeof-container,
+  bugprone-spuriously-wake-up-functions,
+  bugprone-standalone-empty,
+  bugprone-string-constructor,
+  bugprone-string-integer-assignment,
+  bugprone-string-literal-with-embedded-nul,
+  bugprone-stringview-nullptr,
+  bugprone-suspicious-enum-usage,
+  bugprone-suspicious-include,
+  bugprone-suspicious-memory-comparison,
+  bugprone-suspicious-memset-usage,
+  bugprone-suspicious-realloc-usage,
+  bugprone-suspicious-semicolon,
+  bugprone-suspicious-string-compare,
+  bugprone-swapped-arguments,
+  bugprone-terminating-continue,
+  bugprone-throw-keyword-missing,
+  bugprone-undefined-memory-manipulation,
+  bugprone-undelegated-constructor,
+  bugprone-unhandled-exception-at-new,
+  bugprone-unique-ptr-array-mismatch,
+  bugprone-unsafe-functions,
+  bugprone-virtual-near-miss,
+  cppcoreguidelines-no-suspend-with-lock,
+  cppcoreguidelines-virtual-class-destructor,
+  hicpp-ignored-remove-result,
+  misc-definitions-in-headers,
+  misc-header-include-cycle,
+  misc-misplaced-const,
+  misc-static-assert,
+  misc-throw-by-value-catch-by-reference,
+  misc-unused-alias-decls,
+  misc-unused-using-decls,
+  readability-duplicate-include,
+  readability-enum-initial-value,
+  readability-misleading-indentation,
+  readability-non-const-parameter,
+  readability-redundant-declaration,
+  readability-reference-to-constructed-temporary,
+  modernize-deprecated-headers,
+  modernize-make-shared,
+  modernize-make-unique,
+  performance-implicit-conversion-in-loop,
+  performance-move-constructor-init,
+  performance-trivially-destructible
   "
-# bugprone-assert-side-effect,
-# bugprone-bad-signal-to-kill-thread,
-# bugprone-bool-pointer-implicit-conversion,
-# bugprone-casting-through-void,
-# bugprone-chained-comparison,
-# bugprone-compare-pointer-to-member-virtual-function,
-# bugprone-copy-constructor-init,
-# bugprone-crtp-constructor-accessibility,
-# bugprone-dangling-handle,
-# bugprone-dynamic-static-initializers,
+# ---
+# checks that have some issues that need to be resolved:
+#
 # bugprone-empty-catch,
-# bugprone-fold-init-type,
-# bugprone-forward-declaration-namespace,
-# bugprone-inaccurate-erase,
+# bugprone-crtp-constructor-accessibility,
 # bugprone-inc-dec-in-conditions,
-# bugprone-incorrect-enable-if,
-# bugprone-incorrect-roundings,
-# bugprone-infinite-loop,
-# bugprone-integer-division,
-# bugprone-lambda-function-name,
-# bugprone-macro-parentheses,
-# bugprone-macro-repeated-side-effects,
-# bugprone-misplaced-operator-in-strlen-in-alloc,
-# bugprone-misplaced-pointer-arithmetic-in-alloc,
-# bugprone-misplaced-widening-cast,
-# bugprone-move-forwarding-reference,
-# bugprone-multi-level-implicit-pointer-conversion,
-# bugprone-multiple-new-in-one-expression,
-# bugprone-multiple-statement-macro,
-# bugprone-no-escape,
-# bugprone-non-zero-enum-to-bool-conversion,
-# bugprone-optional-value-conversion,
-# bugprone-parent-virtual-call,
-# bugprone-pointer-arithmetic-on-polymorphic-object,
-# bugprone-posix-return,
-# bugprone-redundant-branch-condition,
 # bugprone-reserved-identifier,
-# bugprone-return-const-ref-from-parameter,
-# bugprone-shared-ptr-array-mismatch,
-# bugprone-signal-handler,
-# bugprone-signed-char-misuse,
-# bugprone-sizeof-container,
-# bugprone-sizeof-expression,
-# bugprone-spuriously-wake-up-functions,
-# bugprone-standalone-empty,
-# bugprone-string-constructor,
-# bugprone-string-integer-assignment,
-# bugprone-string-literal-with-embedded-nul,
-# bugprone-stringview-nullptr,
-# bugprone-suspicious-enum-usage,
-# bugprone-suspicious-include,
-# bugprone-suspicious-memory-comparison,
-# bugprone-suspicious-memset-usage,
-# bugprone-suspicious-missing-comma,
-# bugprone-suspicious-realloc-usage,
-# bugprone-suspicious-semicolon,
-# bugprone-suspicious-string-compare,
-# bugprone-suspicious-stringview-data-usage,
-# bugprone-swapped-arguments,
-# bugprone-switch-missing-default-case,
-# bugprone-terminating-continue,
-# bugprone-throw-keyword-missing,
-# bugprone-too-small-loop-variable,
-# bugprone-undefined-memory-manipulation,
-# bugprone-undelegated-constructor,
-# bugprone-unhandled-exception-at-new,
-# bugprone-unhandled-self-assignment,
-# bugprone-unique-ptr-array-mismatch,
-# bugprone-unsafe-functions,
+# bugprone-move-forwarding-reference,
 # bugprone-unused-local-non-trivial-variable,
-# bugprone-unused-raii,
+# bugprone-return-const-ref-from-parameter,
+# bugprone-switch-missing-default-case,
+# bugprone-sizeof-expression,
+# bugprone-suspicious-stringview-data-usage,
+# bugprone-suspicious-missing-comma,
+# bugprone-pointer-arithmetic-on-polymorphic-object,
+# bugprone-optional-value-conversion,
+# bugprone-too-small-loop-variable,
 # bugprone-unused-return-value,
 # bugprone-use-after-move,
-# bugprone-virtual-near-miss,
-# cppcoreguidelines-init-variables,
+# bugprone-unhandled-self-assignment,
+# bugprone-unused-raii,
+#
 # cppcoreguidelines-misleading-capture-default-by-value,
-# cppcoreguidelines-no-suspend-with-lock,
+# cppcoreguidelines-init-variables,
 # cppcoreguidelines-pro-type-member-init,
 # cppcoreguidelines-pro-type-static-cast-downcast,
-# cppcoreguidelines-rvalue-reference-param-not-moved,
 # cppcoreguidelines-use-default-member-init,
-# cppcoreguidelines-virtual-class-destructor,
-# hicpp-ignored-remove-result,
+# cppcoreguidelines-rvalue-reference-param-not-moved,
+#
 # llvm-namespace-comment,
 # misc-const-correctness,
-# misc-definitions-in-headers,
-# misc-header-include-cycle,
 # misc-include-cleaner,
-# misc-misplaced-const,
 # misc-redundant-expression,
-# misc-static-assert,
-# misc-throw-by-value-catch-by-reference,
-# misc-unused-alias-decls,
-# misc-unused-using-decls,
+#
+# readability-avoid-nested-conditional-operator,
+# readability-avoid-return-with-void-value,
+# readability-braces-around-statements,
+# readability-container-contains,
+# readability-container-size-empty,
+# readability-convert-member-functions-to-static,
+# readability-const-return-type,
+# readability-else-after-return,
+# readability-implicit-bool-conversion,
+# readability-inconsistent-declaration-parameter-name,
+# readability-identifier-naming,
+# readability-make-member-function-const,
+# readability-math-missing-parentheses,
+# readability-redundant-inline-specifier,
+# readability-redundant-member-init,
+# readability-redundant-casting,
+# readability-redundant-string-init,
+# readability-simplify-boolean-expr,
+# readability-static-definition-in-anonymous-namespace,
+# readability-suspicious-call-argument,
+# readability-use-std-min-max,
+# readability-static-accessed-through-instance,
+#
 # modernize-concat-nested-namespaces,
-# modernize-deprecated-headers,
-# modernize-make-shared,
-# modernize-make-unique,
 # modernize-pass-by-value,
 # modernize-type-traits,
 # modernize-use-designated-initializers,
@@ -111,79 +149,50 @@ Checks: "-*,
 # modernize-use-starts-ends-with,
 # modernize-use-std-numbers,
 # modernize-use-using,
+#
 # performance-faster-string-find,
 # performance-for-range-copy,
-# performance-implicit-conversion-in-loop,
 # performance-inefficient-vector-operation,
 # performance-move-const-arg,
-# performance-move-constructor-init,
 # performance-no-automatic-move,
-# performance-trivially-destructible,
-# readability-avoid-nested-conditional-operator,
-# readability-avoid-return-with-void-value,
-# readability-braces-around-statements,
-# readability-const-return-type,
-# readability-container-contains,
-# readability-container-size-empty,
-# readability-convert-member-functions-to-static,
-# readability-duplicate-include,
-# readability-else-after-return,
-# readability-enum-initial-value,
-# readability-implicit-bool-conversion,
-# readability-inconsistent-declaration-parameter-name,
-# readability-identifier-naming,
-# readability-make-member-function-const,
-# readability-math-missing-parentheses,
-# readability-misleading-indentation,
-# readability-non-const-parameter,
-# readability-redundant-casting,
-# readability-redundant-declaration,
-# readability-redundant-inline-specifier,
-# readability-redundant-member-init,
-# readability-redundant-string-init,
-# readability-reference-to-constructed-temporary,
-# readability-simplify-boolean-expr,
-# readability-static-accessed-through-instance,
-# readability-static-definition-in-anonymous-namespace,
-# readability-suspicious-call-argument,
-# readability-use-std-min-max
+# ---
 #
-# CheckOptions:
-#   readability-braces-around-statements.ShortStatementLines: 2
-#   readability-identifier-naming.MacroDefinitionCase: UPPER_CASE
-#   readability-identifier-naming.ClassCase: CamelCase
-#   readability-identifier-naming.StructCase: CamelCase
-#   readability-identifier-naming.UnionCase: CamelCase
-#   readability-identifier-naming.EnumCase: CamelCase
-#   readability-identifier-naming.EnumConstantCase: CamelCase
-#   readability-identifier-naming.ScopedEnumConstantCase: CamelCase
-#   readability-identifier-naming.GlobalConstantCase: UPPER_CASE
-#   readability-identifier-naming.GlobalConstantPrefix: "k"
-#   readability-identifier-naming.GlobalVariableCase: CamelCase
-#   readability-identifier-naming.GlobalVariablePrefix: "g"
-#   readability-identifier-naming.ConstexprFunctionCase: camelBack
-#   readability-identifier-naming.ConstexprMethodCase: camelBack
-#   readability-identifier-naming.ClassMethodCase: camelBack
-#   readability-identifier-naming.ClassMemberCase: camelBack
-#   readability-identifier-naming.ClassConstantCase: UPPER_CASE
-#   readability-identifier-naming.ClassConstantPrefix: "k"
-#   readability-identifier-naming.StaticConstantCase: UPPER_CASE
-#   readability-identifier-naming.StaticConstantPrefix: "k"
-#   readability-identifier-naming.StaticVariableCase: UPPER_CASE
-#   readability-identifier-naming.StaticVariablePrefix: "k"
-#   readability-identifier-naming.ConstexprVariableCase: UPPER_CASE
-#   readability-identifier-naming.ConstexprVariablePrefix: "k"
-#   readability-identifier-naming.LocalConstantCase: camelBack
-#   readability-identifier-naming.LocalVariableCase: camelBack
-#   readability-identifier-naming.TemplateParameterCase: CamelCase
-#   readability-identifier-naming.ParameterCase: camelBack
-#   readability-identifier-naming.FunctionCase: camelBack
-#   readability-identifier-naming.MemberCase: camelBack
-#   readability-identifier-naming.PrivateMemberSuffix: _
-#   readability-identifier-naming.ProtectedMemberSuffix: _
-#   readability-identifier-naming.PublicMemberSuffix: ""
-#   readability-identifier-naming.FunctionIgnoredRegexp: ".*tag_invoke.*"
-#   bugprone-unsafe-functions.ReportMoreUnsafeFunctions: true
+CheckOptions:
+  #   readability-braces-around-statements.ShortStatementLines: 2
+  #   readability-identifier-naming.MacroDefinitionCase: UPPER_CASE
+  #   readability-identifier-naming.ClassCase: CamelCase
+  #   readability-identifier-naming.StructCase: CamelCase
+  #   readability-identifier-naming.UnionCase: CamelCase
+  #   readability-identifier-naming.EnumCase: CamelCase
+  #   readability-identifier-naming.EnumConstantCase: CamelCase
+  #   readability-identifier-naming.ScopedEnumConstantCase: CamelCase
+  #   readability-identifier-naming.GlobalConstantCase: UPPER_CASE
+  #   readability-identifier-naming.GlobalConstantPrefix: "k"
+  #   readability-identifier-naming.GlobalVariableCase: CamelCase
+  #   readability-identifier-naming.GlobalVariablePrefix: "g"
+  #   readability-identifier-naming.ConstexprFunctionCase: camelBack
+  #   readability-identifier-naming.ConstexprMethodCase: camelBack
+  #   readability-identifier-naming.ClassMethodCase: camelBack
+  #   readability-identifier-naming.ClassMemberCase: camelBack
+  #   readability-identifier-naming.ClassConstantCase: UPPER_CASE
+  #   readability-identifier-naming.ClassConstantPrefix: "k"
+  #   readability-identifier-naming.StaticConstantCase: UPPER_CASE
+  #   readability-identifier-naming.StaticConstantPrefix: "k"
+  #   readability-identifier-naming.StaticVariableCase: UPPER_CASE
+  #   readability-identifier-naming.StaticVariablePrefix: "k"
+  #   readability-identifier-naming.ConstexprVariableCase: UPPER_CASE
+  #   readability-identifier-naming.ConstexprVariablePrefix: "k"
+  #   readability-identifier-naming.LocalConstantCase: camelBack
+  #   readability-identifier-naming.LocalVariableCase: camelBack
+  #   readability-identifier-naming.TemplateParameterCase: CamelCase
+  #   readability-identifier-naming.ParameterCase: camelBack
+  #   readability-identifier-naming.FunctionCase: camelBack
+  #   readability-identifier-naming.MemberCase: camelBack
+  #   readability-identifier-naming.PrivateMemberSuffix: _
+  #   readability-identifier-naming.ProtectedMemberSuffix: _
+  #   readability-identifier-naming.PublicMemberSuffix: ""
+  #   readability-identifier-naming.FunctionIgnoredRegexp: ".*tag_invoke.*"
+  bugprone-unsafe-functions.ReportMoreUnsafeFunctions: true
 #   bugprone-unused-return-value.CheckedReturnTypes: ::std::error_code;::std::error_condition;::std::errc
 #   misc-include-cleaner.IgnoreHeaders: '.*/(detail|impl)/.*;.*(expected|unexpected).*;.*ranges_lower_bound\.h;time.h;stdlib.h;__chrono/.*;fmt/chrono.h;boost/uuid/uuid_hash.hpp'
 #

.github/workflows/reusable-build-test-config.yml

@@ -101,7 +101,7 @@ jobs:
     steps:
       - name: Cleanup workspace (macOS and Windows)
         if: ${{ runner.os == 'macOS' || runner.os == 'Windows' }}
-        uses: XRPLF/actions/cleanup-workspace@cf0433aa74563aead044a1e395610c96d65a37cf
+        uses: XRPLF/actions/cleanup-workspace@c7d9ce5ebb03c752a354889ecd870cadfc2b1cd4
 
       - name: Checkout repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
@@ -229,8 +229,21 @@ jobs:
         env:
           BUILD_NPROC: ${{ steps.nproc.outputs.nproc }}
         run: |
-          ./xrpld --unittest --unittest-jobs "${BUILD_NPROC}"
+          set -o pipefail
+          ./xrpld --unittest --unittest-jobs "${BUILD_NPROC}" 2>&1 | tee unittest.log
 
+      - name: Show test failure summary
+        if: ${{ failure() && !inputs.build_only }}
+        working-directory: ${{ runner.os == 'Windows' && format('{0}/{1}', env.BUILD_DIR, inputs.build_type) || env.BUILD_DIR }}
+        run: |
+          if [ ! -f unittest.log ]; then
+            echo "unittest.log not found; embedded tests may not have run."
+            exit 0
+          fi
+
+          if ! grep -E "failed" unittest.log; then
+            echo "Log present but no failure lines found in unittest.log."
+          fi
       - name: Debug failure (Linux)
         if: ${{ failure() && runner.os == 'Linux' && !inputs.build_only }}
         run: |

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

@@ -78,9 +78,9 @@ jobs:
         id: run_clang_tidy
         continue-on-error: true
         env:
-          FILES: ${{ inputs.files }}
+          TARGETS: ${{ inputs.files != '' && inputs.files || 'src tests' }}
         run: |
-          run-clang-tidy -j ${{ steps.nproc.outputs.nproc }} -p "$BUILD_DIR" $FILES 2>&1 | tee clang-tidy-output.txt
+          run-clang-tidy -j ${{ steps.nproc.outputs.nproc }} -p "${BUILD_DIR}" ${TARGETS} 2>&1 | tee clang-tidy-output.txt
 
       - name: Upload clang-tidy output
         if: steps.run_clang_tidy.outcome != 'success'

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

@@ -22,7 +22,8 @@ jobs:
     if: ${{ inputs.check_only_changed }}
     runs-on: ubuntu-latest
     outputs:
-      any_changed: ${{ steps.changed_files.outputs.any_changed }}
+      clang_tidy_config_changed: ${{ steps.changed_clang_tidy.outputs.any_changed }}
+      any_cpp_changed: ${{ steps.changed_files.outputs.any_changed }}
       all_changed_files: ${{ steps.changed_files.outputs.all_changed_files }}
     steps:
       - name: Checkout repository
@@ -38,10 +39,17 @@ jobs:
             **/*.ipp
           separator: " "
 
+      - name: Get changed clang-tidy configuration
+        id: changed_clang_tidy
+        uses: tj-actions/changed-files@7dee1b0c1557f278e5c7dc244927139d78c0e22a # v47.0.4
+        with:
+          files: |
+            .clang-tidy
+
   run-clang-tidy:
     needs: [determine-files]
-    if: ${{ always() && !cancelled() && (!inputs.check_only_changed || needs.determine-files.outputs.any_changed == 'true') }}
+    if: ${{ always() && !cancelled() && (!inputs.check_only_changed || needs.determine-files.outputs.any_cpp_changed == 'true' || needs.determine-files.outputs.clang_tidy_config_changed == 'true') }}
     uses: ./.github/workflows/reusable-clang-tidy-files.yml
     with:
-      files: ${{ inputs.check_only_changed && needs.determine-files.outputs.all_changed_files || '' }}
+      files: ${{ (needs.determine-files.outputs.clang_tidy_config_changed == 'true' && '') || (inputs.check_only_changed && needs.determine-files.outputs.all_changed_files || '') }}
       create_issue_on_failure: ${{ inputs.create_issue_on_failure }}

.github/workflows/upload-conan-deps.yml

@@ -64,7 +64,7 @@ jobs:
     steps:
       - name: Cleanup workspace (macOS and Windows)
         if: ${{ runner.os == 'macOS' || runner.os == 'Windows' }}
-        uses: XRPLF/actions/cleanup-workspace@cf0433aa74563aead044a1e395610c96d65a37cf
+        uses: XRPLF/actions/cleanup-workspace@c7d9ce5ebb03c752a354889ecd870cadfc2b1cd4
 
       - name: Checkout repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2

CONTRIBUTING.md

@@ -251,6 +251,29 @@ pip3 install pre-commit
 pre-commit install
 ```
 
+## Clang-tidy
+
+All code must pass `clang-tidy` checks according to the settings in [`.clang-tidy`](./.clang-tidy).
+
+There is a Continuous Integration job that runs clang-tidy on pull requests. The CI will check:
+
+- All changed C++ files (`.cpp`, `.h`, `.ipp`) when only code files are modified
+- **All files in the repository** when the `.clang-tidy` configuration file is changed
+
+This ensures that configuration changes don't introduce new warnings across the codebase.
+
+### Running clang-tidy locally
+
+Before running clang-tidy, you must build the project to generate required files (particularly protobuf headers). Refer to [`BUILD.md`](./BUILD.md) for build instructions.
+
+Then run clang-tidy on your local changes:
+
+```
+run-clang-tidy -p build src tests
+```
+
+This will check all source files in the `src` and `tests` directories using the compile commands from your `build` directory.
+
 ## Contracts and instrumentation
 
 We are using [Antithesis](https://antithesis.com/) for continuous fuzzing,

cspell.config.yaml

@@ -71,6 +71,7 @@ words:
   - coldwallet
   - compr
   - conanfile
+  - cppcoro
   - conanrun
   - confs
   - connectability
@@ -101,9 +102,11 @@ words:
   - Falco
   - finalizers
   - firewalled
+  - fcontext
   - fmtdur
   - fsanitize
   - funclets
+  - gantt
   - gcov
   - gcovr
   - ghead
@@ -185,6 +188,7 @@ words:
   - ostr
   - pargs
   - partitioner
+  - pratik
   - paychan
   - paychans
   - permdex
@@ -206,6 +210,7 @@ words:
   - queuable
   - Raphson
   - replayer
+  - repost
   - rerere
   - retriable
   - RIPD
@@ -236,6 +241,7 @@ words:
   - soci
   - socidb
   - sslws
+  - stackful
   - statsd
   - STATSDCOLLECTOR
   - stissue

include/xrpl/core/CoroTask.h

@@ -0,0 +1,687 @@
+#pragma once
+
+#include <coroutine>
+#include <exception>
+#include <utility>
+#include <variant>
+
+namespace xrpl {
+
+template <typename T = void>
+class CoroTask;
+
+/**
+ * CoroTask<void> -- coroutine return type for void-returning coroutines.
+ *
+ * Class / Dependency Diagram
+ * ==========================
+ *
+ *   CoroTask<void>
+ *   +-----------------------------------------------+
+ *   | - handle_ : Handle (coroutine_handle<promise>) |
+ *   +-----------------------------------------------+
+ *   | + handle(), done()                             |
+ *   | + await_ready/suspend/resume  (Awaiter iface)  |
+ *   +-----------------------------------------------+
+ *            |  owns
+ *            v
+ *   promise_type
+ *   +-----------------------------------------------+
+ *   | - exception_    : std::exception_ptr           |
+ *   | - continuation_ : std::coroutine_handle<>      |
+ *   +-----------------------------------------------+
+ *   | + get_return_object() -> CoroTask              |
+ *   | + initial_suspend()   -> suspend_always (lazy) |
+ *   | + final_suspend()     -> FinalAwaiter          |
+ *   | + return_void()                                |
+ *   | + unhandled_exception()                        |
+ *   +-----------------------------------------------+
+ *            |  returns at final_suspend
+ *            v
+ *   FinalAwaiter
+ *   +-----------------------------------------------+
+ *   | await_suspend(h):                              |
+ *   |   if continuation_ set -> symmetric transfer   |
+ *   |   else                 -> noop_coroutine        |
+ *   +-----------------------------------------------+
+ *
+ * Design Notes
+ * ------------
+ * - Lazy start: initial_suspend returns suspend_always, so the coroutine
+ *   body does not execute until the handle is explicitly resumed.
+ * - Symmetric transfer: await_suspend returns a coroutine_handle instead
+ *   of void/bool, allowing the scheduler to jump directly to the next
+ *   coroutine without growing the call stack.
+ * - Continuation chaining: when one CoroTask is co_await-ed inside
+ *   another, the caller's handle is stored as continuation_ so
+ *   FinalAwaiter can resume it when this task finishes.
+ * - Move-only: the handle is exclusively owned; copy is deleted.
+ *
+ * Usage Examples
+ * ==============
+ *
+ * 1. Basic void coroutine (the most common case in rippled):
+ *
+ *      CoroTask<void> doWork(std::shared_ptr<CoroTaskRunner> runner) {
+ *          // do something
+ *          co_await runner->suspend();   // yield control
+ *          // resumed later via runner->post() or runner->resume()
+ *          co_return;
+ *      }
+ *
+ * 2. co_await-ing one CoroTask<void> from another (chaining):
+ *
+ *      CoroTask<void> inner() {
+ *          // ...
+ *          co_return;
+ *      }
+ *      CoroTask<void> outer() {
+ *          co_await inner();   // continuation_ links outer -> inner
+ *          co_return;          // FinalAwaiter resumes outer
+ *      }
+ *
+ * 3. Exceptions propagate through co_await:
+ *
+ *      CoroTask<void> failing() {
+ *          throw std::runtime_error("oops");
+ *          co_return;
+ *      }
+ *      CoroTask<void> caller() {
+ *          try { co_await failing(); }
+ *          catch (std::runtime_error const&) { // caught here }
+ *      }
+ *
+ * Caveats / Pitfalls
+ * ==================
+ *
+ * BUG-RISK: Dangling references in coroutine parameters.
+ *   Coroutine parameters are copied into the frame, but references
+ *   are NOT -- they are stored as-is. If the referent goes out of scope
+ *   before the coroutine finishes, you get use-after-free.
+ *
+ *      // BROKEN -- local dies before coroutine runs:
+ *      CoroTask<void> bad(int& ref) { co_return; }
+ *      void launch() {
+ *          int local = 42;
+ *          auto task = bad(local);  // frame stores &local
+ *      }  // local destroyed; frame holds dangling ref
+ *
+ *      // FIX -- pass by value, or ensure lifetime via shared_ptr.
+ *
+ * BUG-RISK: GCC 14 corrupts reference captures in coroutine lambdas.
+ *   When a lambda that returns CoroTask captures by reference ([&]),
+ *   GCC 14 may generate a corrupted coroutine frame. Always capture
+ *   by explicit pointer-to-value instead:
+ *
+ *      // BROKEN on GCC 14:
+ *      jq.postCoroTask(t, n, [&](auto) -> CoroTask<void> { ... });
+ *
+ *      // FIX -- capture pointers explicitly:
+ *      jq.postCoroTask(t, n, [ptr = &val](auto) -> CoroTask<void> { ... });
+ *
+ * BUG-RISK: Resuming a destroyed or completed CoroTask.
+ *   Calling handle().resume() after the coroutine has already run to
+ *   completion (done() == true) is undefined behavior. The CoroTaskRunner
+ *   guards against this with an XRPL_ASSERT, but standalone usage of
+ *   CoroTask must check done() before resuming.
+ *
+ * BUG-RISK: Moving a CoroTask that is being awaited.
+ *   If task A is co_await-ed by task B (so A.continuation_ == B), moving
+ *   or destroying A will invalidate the continuation link. Never move
+ *   or reassign a CoroTask while it is mid-execution or being awaited.
+ *
+ * LIMITATION: CoroTask is fire-and-forget for the top-level owner.
+ *   There is no built-in notification when the coroutine finishes.
+ *   The caller must use external synchronization (e.g. CoroTaskRunner::join
+ *   or a gate/condition_variable) to know when it is done.
+ *
+ * LIMITATION: No cancellation token.
+ *   There is no way to cancel a suspended CoroTask from outside. The
+ *   coroutine body must cooperatively check a flag (e.g. jq_.isStopping())
+ *   after each co_await and co_return early if needed.
+ *
+ * LIMITATION: Stackless -- cannot suspend from nested non-coroutine calls.
+ *   If a coroutine calls a regular function that wants to "yield", it
+ *   cannot. Only the immediate coroutine body can use co_await.
+ *   This is acceptable for rippled because all yield() sites are shallow.
+ */
+template <>
+class CoroTask<void>
+{
+public:
+    struct promise_type;
+    using Handle = std::coroutine_handle<promise_type>;
+
+    /**
+     * Coroutine promise. Compiler uses this to manage coroutine state.
+     * Stores the exception (if any) and the continuation handle for
+     * symmetric transfer back to the awaiting coroutine.
+     */
+    struct promise_type
+    {
+        // Captured exception from the coroutine body, rethrown in
+        // await_resume() when this task is co_await-ed by a caller.
+        std::exception_ptr exception_;
+
+        // Handle to the coroutine that is co_await-ing this task.
+        // Set by await_suspend(). FinalAwaiter uses it for symmetric
+        // transfer back to the caller. Null if this is a top-level task.
+        std::coroutine_handle<> continuation_;
+
+        /**
+         * Create the CoroTask return object.
+         * Called by the compiler at coroutine creation.
+         */
+        CoroTask
+        get_return_object()
+        {
+            return CoroTask{Handle::from_promise(*this)};
+        }
+
+        /**
+         * Lazy start. The coroutine body does not execute until the
+         * handle is explicitly resumed (e.g. by CoroTaskRunner::resume).
+         */
+        std::suspend_always
+        initial_suspend() noexcept
+        {
+            return {};
+        }
+
+        /**
+         * Awaiter returned by final_suspend(). Uses symmetric transfer:
+         * if a continuation exists, transfers control directly to it
+         * (tail-call, no stack growth). Otherwise returns noop_coroutine
+         * so the coroutine frame stays alive for the owner to destroy.
+         */
+        struct FinalAwaiter
+        {
+            /**
+             * Always false. We need await_suspend to run for
+             * symmetric transfer.
+             */
+            bool
+            await_ready() noexcept
+            {
+                return false;
+            }
+
+            /**
+             * Symmetric transfer: returns the continuation handle so
+             * the compiler emits a tail-call instead of a nested resume.
+             * If no continuation is set, returns noop_coroutine to
+             * suspend at final_suspend without destroying the frame.
+             *
+             * @param h Handle to this completing coroutine
+             *
+             * @return Continuation handle, or noop_coroutine
+             */
+            std::coroutine_handle<>
+            await_suspend(Handle h) noexcept
+            {
+                if (auto cont = h.promise().continuation_)
+                    return cont;
+                return std::noop_coroutine();
+            }
+
+            void
+            await_resume() noexcept
+            {
+            }
+        };
+
+        /**
+         * Returns FinalAwaiter for symmetric transfer at coroutine end.
+         */
+        FinalAwaiter
+        final_suspend() noexcept
+        {
+            return {};
+        }
+
+        /**
+         * Called by the compiler for `co_return;` (void coroutine).
+         */
+        void
+        return_void()
+        {
+        }
+
+        /**
+         * Called by the compiler when an exception escapes the coroutine
+         * body. Captures it for later rethrowing in await_resume().
+         */
+        void
+        unhandled_exception()
+        {
+            exception_ = std::current_exception();
+        }
+    };
+
+    /**
+     * Default constructor. Creates an empty (null handle) task.
+     */
+    CoroTask() = default;
+
+    /**
+     * Takes ownership of a compiler-generated coroutine handle.
+     *
+     * @param h Coroutine handle to own
+     */
+    explicit CoroTask(Handle h) : handle_(h)
+    {
+    }
+
+    /**
+     * Destroys the coroutine frame if this task owns one.
+     */
+    ~CoroTask()
+    {
+        if (handle_)
+            handle_.destroy();
+    }
+
+    /**
+     * Move constructor. Transfers handle ownership, leaves other empty.
+     */
+    CoroTask(CoroTask&& other) noexcept : handle_(std::exchange(other.handle_, {}))
+    {
+    }
+
+    /**
+     * Move assignment. Destroys current frame (if any), takes other's.
+     */
+    CoroTask&
+    operator=(CoroTask&& other) noexcept
+    {
+        if (this != &other)
+        {
+            if (handle_)
+                handle_.destroy();
+            handle_ = std::exchange(other.handle_, {});
+        }
+        return *this;
+    }
+
+    CoroTask(CoroTask const&) = delete;
+    CoroTask&
+    operator=(CoroTask const&) = delete;
+
+    /**
+     * @return The underlying coroutine_handle
+     */
+    Handle
+    handle() const
+    {
+        return handle_;
+    }
+
+    /**
+     * @return true if the coroutine has run to completion (or thrown)
+     */
+    bool
+    done() const
+    {
+        return handle_ && handle_.done();
+    }
+
+    // -- Awaiter interface: allows `co_await someCoroTask;` --
+
+    /**
+     * Always false. This task is lazy, so co_await always suspends
+     * the caller to set up the continuation link.
+     */
+    bool
+    await_ready() const noexcept
+    {
+        return false;
+    }
+
+    /**
+     * Stores the caller's handle as our continuation, then returns
+     * our handle for symmetric transfer (caller suspends, we resume).
+     *
+     * @param caller Handle of the coroutine doing co_await on us
+     *
+     * @return Our handle for symmetric transfer
+     */
+    std::coroutine_handle<>
+    await_suspend(std::coroutine_handle<> caller) noexcept
+    {
+        handle_.promise().continuation_ = caller;
+        return handle_;  // Symmetric transfer
+    }
+
+    /**
+     * Called when the caller resumes after co_await. Rethrows any
+     * exception captured by unhandled_exception().
+     */
+    void
+    await_resume()
+    {
+        if (auto& ep = handle_.promise().exception_)
+            std::rethrow_exception(ep);
+    }
+
+private:
+    // Exclusively-owned coroutine handle. Null after move or default
+    // construction. Destroyed in the destructor.
+    Handle handle_;
+};
+
+/**
+ * CoroTask<T> -- coroutine return type for value-returning coroutines.
+ *
+ * Class / Dependency Diagram
+ * ==========================
+ *
+ *   CoroTask<T>
+ *   +-----------------------------------------------+
+ *   | - handle_ : Handle (coroutine_handle<promise>) |
+ *   +-----------------------------------------------+
+ *   | + handle(), done()                             |
+ *   | + await_ready/suspend/resume  (Awaiter iface)  |
+ *   +-----------------------------------------------+
+ *            |  owns
+ *            v
+ *   promise_type
+ *   +-----------------------------------------------+
+ *   | - result_       : variant<monostate, T,        |
+ *   |                           exception_ptr>       |
+ *   | - continuation_ : std::coroutine_handle<>      |
+ *   +-----------------------------------------------+
+ *   | + get_return_object() -> CoroTask              |
+ *   | + initial_suspend()   -> suspend_always (lazy) |
+ *   | + final_suspend()     -> FinalAwaiter          |
+ *   | + return_value(T)     -> stores in result_[1]  |
+ *   | + unhandled_exception -> stores in result_[2]  |
+ *   +-----------------------------------------------+
+ *            |  returns at final_suspend
+ *            v
+ *   FinalAwaiter  (same symmetric-transfer pattern as CoroTask<void>)
+ *
+ * Value Extraction
+ * ----------------
+ * await_resume() inspects the variant:
+ *   - index 2 (exception_ptr) -> rethrow
+ *   - index 1 (T)             -> return value via move
+ *
+ * Usage Examples
+ * ==============
+ *
+ * 1. Simple value return:
+ *
+ *      CoroTask<int> computeAnswer() { co_return 42; }
+ *
+ *      CoroTask<void> caller() {
+ *          int v = co_await computeAnswer();  // v == 42
+ *      }
+ *
+ * 2. Chaining value-returning coroutines:
+ *
+ *      CoroTask<int> add(int a, int b) { co_return a + b; }
+ *      CoroTask<int> doubleSum(int a, int b) {
+ *          int s = co_await add(a, b);
+ *          co_return s * 2;
+ *      }
+ *
+ * 3. Exception propagation from inner to outer:
+ *
+ *      CoroTask<int> failing() {
+ *          throw std::runtime_error("bad");
+ *          co_return 0;  // never reached
+ *      }
+ *      CoroTask<void> caller() {
+ *          try {
+ *              int v = co_await failing();  // throws here
+ *          } catch (std::runtime_error const& e) {
+ *              // e.what() == "bad"
+ *          }
+ *      }
+ *
+ * Caveats / Pitfalls (in addition to CoroTask<void> caveats above)
+ * ================================================================
+ *
+ * BUG-RISK: await_resume() moves the value out of the variant.
+ *   Calling co_await on the same CoroTask<T> instance twice is undefined
+ *   behavior -- the second call will see a moved-from T. CoroTask is
+ *   single-shot: one co_return, one co_await.
+ *
+ * BUG-RISK: T must be move-constructible.
+ *   return_value(T) takes by value and moves into the variant.
+ *   Types that are not movable cannot be used as T.
+ *
+ * LIMITATION: No co_yield support.
+ *   CoroTask<T> only supports a single co_return. It does not implement
+ *   yield_value(), so using co_yield inside a CoroTask<T> coroutine is a
+ *   compile error. For streaming values, a different return type
+ *   (e.g. Generator<T>) would be needed.
+ *
+ * LIMITATION: Result is only accessible via co_await.
+ *   There is no .get() or .result() method. The value can only be
+ *   extracted by co_await-ing the CoroTask<T> from inside another
+ *   coroutine. For extracting results in non-coroutine code, pass a
+ *   pointer to the caller and write through it (as the tests do).
+ */
+template <typename T>
+class CoroTask
+{
+public:
+    struct promise_type;
+    using Handle = std::coroutine_handle<promise_type>;
+
+    /**
+     * Coroutine promise for value-returning coroutines.
+     * Stores the result as a variant: monostate (not yet set),
+     * T (co_return value), or exception_ptr (unhandled exception).
+     */
+    struct promise_type
+    {
+        // Tri-state result:
+        //   index 0 (monostate) -- coroutine has not yet completed
+        //   index 1 (T)         -- co_return value stored here
+        //   index 2 (exception) -- unhandled exception captured here
+        std::variant<std::monostate, T, std::exception_ptr> result_;
+
+        // Handle to the coroutine co_await-ing this task. Used by
+        // FinalAwaiter for symmetric transfer. Null for top-level tasks.
+        std::coroutine_handle<> continuation_;
+
+        /**
+         * Create the CoroTask return object.
+         * Called by the compiler at coroutine creation.
+         */
+        CoroTask
+        get_return_object()
+        {
+            return CoroTask{Handle::from_promise(*this)};
+        }
+
+        /**
+         * Lazy start. Coroutine body does not run until explicitly resumed.
+         */
+        std::suspend_always
+        initial_suspend() noexcept
+        {
+            return {};
+        }
+
+        /**
+         * Symmetric-transfer awaiter at coroutine completion.
+         * Same pattern as CoroTask<void>::FinalAwaiter.
+         */
+        struct FinalAwaiter
+        {
+            bool
+            await_ready() noexcept
+            {
+                return false;
+            }
+
+            /**
+             * Returns continuation for symmetric transfer, or
+             * noop_coroutine if this is a top-level task.
+             *
+             * @param h Handle to this completing coroutine
+             *
+             * @return Continuation handle, or noop_coroutine
+             */
+            std::coroutine_handle<>
+            await_suspend(Handle h) noexcept
+            {
+                if (auto cont = h.promise().continuation_)
+                    return cont;
+                return std::noop_coroutine();
+            }
+
+            void
+            await_resume() noexcept
+            {
+            }
+        };
+
+        FinalAwaiter
+        final_suspend() noexcept
+        {
+            return {};
+        }
+
+        /**
+         * Called by the compiler for `co_return value;`.
+         * Moves the value into result_ at index 1.
+         *
+         * @param value The value to store
+         */
+        void
+        return_value(T value)
+        {
+            result_.template emplace<1>(std::move(value));
+        }
+
+        /**
+         * Captures unhandled exceptions at index 2 of result_.
+         * Rethrown later in await_resume().
+         */
+        void
+        unhandled_exception()
+        {
+            result_.template emplace<2>(std::current_exception());
+        }
+    };
+
+    /**
+     * Default constructor. Creates an empty (null handle) task.
+     */
+    CoroTask() = default;
+
+    /**
+     * Takes ownership of a compiler-generated coroutine handle.
+     *
+     * @param h Coroutine handle to own
+     */
+    explicit CoroTask(Handle h) : handle_(h)
+    {
+    }
+
+    /**
+     * Destroys the coroutine frame if this task owns one.
+     */
+    ~CoroTask()
+    {
+        if (handle_)
+            handle_.destroy();
+    }
+
+    /**
+     * Move constructor. Transfers handle ownership, leaves other empty.
+     */
+    CoroTask(CoroTask&& other) noexcept : handle_(std::exchange(other.handle_, {}))
+    {
+    }
+
+    /**
+     * Move assignment. Destroys current frame (if any), takes other's.
+     */
+    CoroTask&
+    operator=(CoroTask&& other) noexcept
+    {
+        if (this != &other)
+        {
+            if (handle_)
+                handle_.destroy();
+            handle_ = std::exchange(other.handle_, {});
+        }
+        return *this;
+    }
+
+    CoroTask(CoroTask const&) = delete;
+    CoroTask&
+    operator=(CoroTask const&) = delete;
+
+    /**
+     * @return The underlying coroutine_handle
+     */
+    Handle
+    handle() const
+    {
+        return handle_;
+    }
+
+    /**
+     * @return true if the coroutine has run to completion (or thrown)
+     */
+    bool
+    done() const
+    {
+        return handle_ && handle_.done();
+    }
+
+    // -- Awaiter interface: allows `T val = co_await someCoroTask;` --
+
+    /**
+     * Always false. co_await always suspends to set up continuation.
+     */
+    bool
+    await_ready() const noexcept
+    {
+        return false;
+    }
+
+    /**
+     * Stores caller as continuation, returns our handle for
+     * symmetric transfer.
+     *
+     * @param caller Handle of the coroutine doing co_await on us
+     *
+     * @return Our handle for symmetric transfer
+     */
+    std::coroutine_handle<>
+    await_suspend(std::coroutine_handle<> caller) noexcept
+    {
+        handle_.promise().continuation_ = caller;
+        return handle_;
+    }
+
+    /**
+     * Extracts the result: rethrows if exception, otherwise moves
+     * the T value out of the variant. Single-shot: calling twice
+     * on the same task is undefined (moved-from T).
+     *
+     * @return The co_return-ed value
+     */
+    T
+    await_resume()
+    {
+        auto& result = handle_.promise().result_;
+        if (auto* ep = std::get_if<2>(&result))
+            std::rethrow_exception(*ep);
+        return std::get<1>(std::move(result));
+    }
+
+private:
+    // Exclusively-owned coroutine handle. Null after move or default
+    // construction. Destroyed in the destructor.
+    Handle handle_;
+};
+
+}  // namespace xrpl

include/xrpl/core/CoroTaskRunner.ipp

@@ -0,0 +1,318 @@
+#pragma once
+
+/**
+ * @file CoroTaskRunner.ipp
+ *
+ * CoroTaskRunner inline implementation.
+ *
+ * This file contains the business logic for managing C++20 coroutines
+ * on the JobQueue. It is included at the bottom of JobQueue.h.
+ *
+ * Data Flow: suspend / post / resume cycle
+ * =========================================
+ *
+ *         coroutine body                 CoroTaskRunner              JobQueue
+ *         --------------                 --------------              --------
+ *              |
+ *    co_await runner->suspend()
+ *              |
+ *              +--- await_suspend ------> onSuspend()
+ *              |                            ++nSuspend_ ------------> nSuspend_
+ *              |                          [coroutine is now suspended]
+ *              |
+ *              .    (externally or by JobQueueAwaiter)
+ *              .
+ *              +--- (caller calls) -----> post()
+ *              |                            running_ = true
+ *              |                            addJob(resume) ----------> job enqueued
+ *              |                                                        |
+ *              |                                                      [worker picks up]
+ *              |                                                        |
+ *              +--- <----- resume() <-----------------------------------+
+ *              |             --nSuspend_ ------> nSuspend_
+ *              |             swap in LocalValues (lvs_)
+ *              |             task_.handle().resume()
+ *              |                |
+ *              |    [coroutine body continues here]
+ *              |                |
+ *              |             swap out LocalValues
+ *              |             running_ = false
+ *              |             cv_.notify_all()
+ *              v
+ *
+ * Thread Safety
+ * =============
+ * - mutex_     : guards task_.handle().resume() so that post()-before-suspend
+ *                races cannot resume the coroutine while it is still running.
+ *                (See the race condition discussion in JobQueue.h)
+ * - mutex_run_ : guards running_ flag; used by join() to wait for completion.
+ * - jq_.m_mutex: guards nSuspend_ increments/decrements.
+ *
+ * Common Mistakes When Modifying This File
+ * =========================================
+ *
+ * 1. Changing lock ordering.
+ *    resume() acquires locks in this order: mutex_run_ -> jq_.m_mutex -> mutex_.
+ *    Acquiring them in a different order WILL deadlock. Any new code path
+ *    that touches these mutexes must follow the same order.
+ *
+ * 2. Removing the shared_from_this() capture in post().
+ *    The lambda passed to addJob captures [this, sp = shared_from_this()].
+ *    If you remove sp, 'this' can be destroyed before the job runs,
+ *    causing use-after-free. The sp capture is load-bearing.
+ *
+ * 3. Forgetting to decrement nSuspend_ on a new code path.
+ *    Every ++nSuspend_ must have a matching --nSuspend_. If you add a new
+ *    suspension path (e.g. a new awaiter) and forget to decrement on resume
+ *    or on failure, JobQueue::stop() will hang.
+ *
+ * 4. Calling task_.handle().resume() without holding mutex_.
+ *    This allows a race where the coroutine runs on two threads
+ *    simultaneously. Always hold mutex_ around resume().
+ *
+ * 5. Swapping LocalValues outside of the mutex_ critical section.
+ *    The swap-in and swap-out of LocalValues must bracket the resume()
+ *    call. If you move the swap-out before the lock_guard(mutex_) is
+ *    released, you break LocalValue isolation for any code that runs
+ *    after the coroutine suspends but before the lock is dropped.
+ */
+//
+
+namespace xrpl {
+
+/**
+ * Construct a CoroTaskRunner. Sets running_ to false; does not
+ * create the coroutine. Call init() afterwards.
+ *
+ * @param jq   The JobQueue this coroutine will run on
+ * @param type Job type for scheduling priority
+ * @param name Human-readable name for logging
+ */
+inline JobQueue::CoroTaskRunner::CoroTaskRunner(
+    create_t,
+    JobQueue& jq,
+    JobType type,
+    std::string const& name)
+    : jq_(jq), type_(type), name_(name), running_(false)
+{
+}
+
+/**
+ * Initialize with a coroutine-returning callable.
+ * Stores the callable on the heap (FuncStore) so it outlives the
+ * coroutine frame. Coroutine frames store a reference to the
+ * callable's implicit object parameter (the lambda). If the callable
+ * is a temporary, that reference dangles after the caller returns.
+ * Keeping the callable alive here ensures the coroutine's captures
+ * remain valid.
+ *
+ * @param f Callable: CoroTask<void>(shared_ptr<CoroTaskRunner>)
+ */
+template <class F>
+void
+JobQueue::CoroTaskRunner::init(F&& f)
+{
+    using Fn = std::decay_t<F>;
+    auto store = std::make_unique<FuncStore<Fn>>(std::forward<F>(f));
+    task_ = store->func(shared_from_this());
+    storedFunc_ = std::move(store);
+}
+
+/**
+ * Destructor. Asserts (debug) that the coroutine has finished
+ * or expectEarlyExit() was called.
+ */
+inline JobQueue::CoroTaskRunner::~CoroTaskRunner()
+{
+#ifndef NDEBUG
+    XRPL_ASSERT(finished_, "xrpl::JobQueue::CoroTaskRunner::~CoroTaskRunner : is finished");
+#endif
+}
+
+/**
+ * Increment the JobQueue's suspended-coroutine count (nSuspend_).
+ */
+inline void
+JobQueue::CoroTaskRunner::onSuspend()
+{
+    std::lock_guard lock(jq_.m_mutex);
+    ++jq_.nSuspend_;
+}
+
+/**
+ * Decrement nSuspend_ without resuming.
+ */
+inline void
+JobQueue::CoroTaskRunner::onUndoSuspend()
+{
+    std::lock_guard lock(jq_.m_mutex);
+    --jq_.nSuspend_;
+}
+
+/**
+ * Return a SuspendAwaiter whose await_suspend() increments nSuspend_
+ * before the coroutine actually suspends. The caller must later call
+ * post() or resume() to continue execution.
+ *
+ * @return Awaiter for use with `co_await runner->suspend()`
+ */
+inline auto
+JobQueue::CoroTaskRunner::suspend()
+{
+    /**
+     * Custom awaiter for suspend(). Always suspends (await_ready
+     * returns false) and increments nSuspend_ in await_suspend().
+     */
+    struct SuspendAwaiter
+    {
+        CoroTaskRunner& runner_;  // The runner that owns this coroutine.
+
+        /**
+         * Always returns false so the coroutine suspends.
+         */
+        bool
+        await_ready() const noexcept
+        {
+            return false;
+        }
+
+        /**
+         * Called when the coroutine suspends. Increments nSuspend_
+         * so the JobQueue knows a coroutine is waiting.
+         */
+        void
+        await_suspend(std::coroutine_handle<>) const
+        {
+            runner_.onSuspend();
+        }
+
+        void
+        await_resume() const noexcept
+        {
+        }
+    };
+    return SuspendAwaiter{*this};
+}
+
+/**
+ * Schedule coroutine resumption as a job on the JobQueue.
+ * A shared_ptr capture (sp) prevents this CoroTaskRunner from being
+ * destroyed while the job is queued but not yet executed.
+ *
+ * @return false if the JobQueue rejected the job (shutting down)
+ */
+inline bool
+JobQueue::CoroTaskRunner::post()
+{
+    {
+        std::lock_guard lk(mutex_run_);
+        running_ = true;
+    }
+
+    // sp prevents 'this' from being destroyed while the job is pending
+    if (jq_.addJob(type_, name_, [this, sp = shared_from_this()]() { resume(); }))
+    {
+        return true;
+    }
+
+    // The coroutine will not run. Clean up running_.
+    std::lock_guard lk(mutex_run_);
+    running_ = false;
+    cv_.notify_all();
+    return false;
+}
+
+/**
+ * Resume the coroutine on the current thread.
+ *
+ * Steps:
+ *   1. Set running_ = true (under mutex_run_)
+ *   2. Decrement nSuspend_ (under jq_.m_mutex)
+ *   3. Swap in this coroutine's LocalValues for thread-local isolation
+ *   4. Resume the coroutine handle (under mutex_)
+ *   5. Swap out LocalValues, restoring the thread's previous state
+ *   6. Set running_ = false and notify join() waiters
+ */
+inline void
+JobQueue::CoroTaskRunner::resume()
+{
+    {
+        std::lock_guard lk(mutex_run_);
+        running_ = true;
+    }
+    {
+        std::lock_guard lock(jq_.m_mutex);
+        --jq_.nSuspend_;
+    }
+    auto saved = detail::getLocalValues().release();
+    detail::getLocalValues().reset(&lvs_);
+    std::lock_guard lock(mutex_);
+    XRPL_ASSERT(!task_.done(), "xrpl::JobQueue::CoroTaskRunner::resume : task is not done");
+    task_.handle().resume();
+    detail::getLocalValues().release();
+    detail::getLocalValues().reset(saved);
+    if (task_.done())
+    {
+#ifndef NDEBUG
+        finished_ = true;
+#endif
+        // Destroy the coroutine frame to break the shared_ptr cycle:
+        // frame -> lambda captures shared_ptr<CoroTaskRunner> -> this.
+        // Also release the heap-stored callable (no longer needed).
+        task_ = {};
+        storedFunc_.reset();
+    }
+    std::lock_guard lk(mutex_run_);
+    running_ = false;
+    cv_.notify_all();
+}
+
+/**
+ * @return true if the coroutine has not yet run to completion
+ */
+inline bool
+JobQueue::CoroTaskRunner::runnable() const
+{
+    // After normal completion, task_ is reset to break the shared_ptr cycle
+    // (handle_ becomes null). A null handle means the coroutine is done.
+    return task_.handle() && !task_.done();
+}
+
+/**
+ * Handle early termination when the coroutine never ran (e.g. JobQueue
+ * is stopping). Decrements nSuspend_ and destroys the coroutine frame
+ * to break the shared_ptr cycle: frame -> lambda -> runner -> frame.
+ */
+inline void
+JobQueue::CoroTaskRunner::expectEarlyExit()
+{
+#ifndef NDEBUG
+    if (!finished_)
+#endif
+    {
+        std::lock_guard lock(jq_.m_mutex);
+        --jq_.nSuspend_;
+#ifndef NDEBUG
+        finished_ = true;
+#endif
+    }
+    // Destroy the coroutine frame to break a potential shared_ptr cycle.
+    // The coroutine is at initial_suspend and never ran user code, so
+    // destroying it is safe. Without this, the frame holds a shared_ptr
+    // back to this CoroTaskRunner, creating an unreachable reference cycle.
+    task_ = {};
+    storedFunc_.reset();
+}
+
+/**
+ * Block until the coroutine finishes its current execution slice.
+ * Uses cv_ + mutex_run_ to wait until running_ == false.
+ */
+inline void
+JobQueue::CoroTaskRunner::join()
+{
+    std::unique_lock<std::mutex> lk(mutex_run_);
+    cv_.wait(lk, [this]() { return running_ == false; });
+}
+
+}  // namespace xrpl

include/xrpl/core/JobQueue.h

@@ -2,6 +2,7 @@
 
 #include <xrpl/basics/LocalValue.h>
 #include <xrpl/core/ClosureCounter.h>
+#include <xrpl/core/CoroTask.h>
 #include <xrpl/core/JobTypeData.h>
 #include <xrpl/core/JobTypes.h>
 #include <xrpl/core/detail/Workers.h>
@@ -9,6 +10,7 @@
 
 #include <boost/coroutine/all.hpp>
 
+#include <coroutine>
 #include <set>
 
 namespace xrpl {
@@ -119,6 +121,386 @@ public:
         join();
     };
 
+    /** C++20 coroutine lifecycle manager. Replaces Coro for new code.
+     *
+     *  Class / Inheritance / Dependency Diagram
+     *  =========================================
+     *
+     *  std::enable_shared_from_this<CoroTaskRunner>
+     *            ^
+     *            | (public inheritance)
+     *            |
+     *  CoroTaskRunner
+     *  +---------------------------------------------------+
+     *  | - lvs_         : detail::LocalValues               |
+     *  | - jq_          : JobQueue&                         |
+     *  | - type_        : JobType                           |
+     *  | - name_        : std::string                       |
+     *  | - running_     : bool                              |
+     *  | - mutex_       : std::mutex      (coroutine guard) |
+     *  | - mutex_run_   : std::mutex      (join guard)      |
+     *  | - cv_          : condition_variable                 |
+     *  | - task_        : CoroTask<void>                    |
+     *  | - storedFunc_  : unique_ptr<FuncBase> (type-erased)|
+     *  +---------------------------------------------------+
+     *  | + init(F&&)         : set up coroutine callable    |
+     *  | + onSuspend()       : ++jq_.nSuspend_              |
+     *  | + onUndoSuspend()   : --jq_.nSuspend_              |
+     *  | + suspend()         : returns SuspendAwaiter       |
+     *  | + post()            : schedule resume on JobQueue  |
+     *  | + resume()          : resume coroutine on caller   |
+     *  | + runnable()        : !task_.done()                |
+     *  | + expectEarlyExit() : teardown for failed post     |
+     *  | + join()            : block until not running       |
+     *  +---------------------------------------------------+
+     *          |                          |
+     *          | owns                     | references
+     *          v                          v
+     *    CoroTask<void>             JobQueue
+     *    (coroutine frame)          (thread pool + nSuspend_)
+     *
+     *    FuncBase / FuncStore<F>    (type-erased heap storage
+     *                                for the coroutine lambda)
+     *
+     *  Coroutine Lifecycle (Control Flow)
+     *  ===================================
+     *
+     *  Caller thread              JobQueue worker thread
+     *  -------------              ----------------------
+     *  postCoroTask(f)
+     *    |
+     *    +-- make_shared<CoroTaskRunner>
+     *    +-- init(f)
+     *    |     +-- store lambda on heap (FuncStore)
+     *    |     +-- task_ = f(shared_from_this())
+     *    |           [coroutine created, suspended at initial_suspend]
+     *    +-- ++nSuspend_  (lazy start counts as suspended)
+     *    +-- post()
+     *    |     +-- addJob(type_, [resume]{})
+     *    |                                    resume()
+     *    |                                      |
+     *    |                                      +-- running_ = true
+     *    |                                      +-- --nSuspend_
+     *    |                                      +-- swap in LocalValues
+     *    |                                      +-- task_.handle().resume()
+     *    |                                      |     [coroutine body runs]
+     *    |                                      |     ...
+     *    |                                      |     co_await suspend()
+     *    |                                      |       +-- ++nSuspend_
+     *    |                                      |       [coroutine suspends]
+     *    |                                      +-- swap out LocalValues
+     *    |                                      +-- running_ = false
+     *    |                                      +-- cv_.notify_all()
+     *    |
+     *  post()  <-- called externally or by JobQueueAwaiter
+     *    +-- addJob(type_, [resume]{})
+     *                                         resume()
+     *                                           |
+     *                                           +-- [coroutine body continues]
+     *                                           +-- co_return
+     *                                           +-- running_ = false
+     *                                           +-- cv_.notify_all()
+     *  join()
+     *    +-- cv_.wait([]{!running_})
+     *    +-- [done]
+     *
+     *  Usage Examples
+     *  ==============
+     *
+     *  1. Fire-and-forget coroutine (most common pattern):
+     *
+     *      jq.postCoroTask(jtCLIENT, "MyWork",
+     *          [](auto runner) -> CoroTask<void> {
+     *              doSomeWork();
+     *              co_await runner->suspend();  // yield to other jobs
+     *              doMoreWork();
+     *              co_return;
+     *          });
+     *
+     *  2. Manually controlling suspend / resume (external trigger):
+     *
+     *      auto runner = jq.postCoroTask(jtCLIENT, "ExtTrigger",
+     *          [&result](auto runner) -> CoroTask<void> {
+     *              startAsyncOperation(callback);
+     *              co_await runner->suspend();
+     *              // callback called runner->post() to get here
+     *              result = collectResult();
+     *              co_return;
+     *          });
+     *      // ... later, from the callback:
+     *      runner->post();   // reschedule the coroutine on the JobQueue
+     *
+     *  3. Using JobQueueAwaiter for automatic suspend + repost:
+     *
+     *      jq.postCoroTask(jtCLIENT, "AutoRepost",
+     *          [](auto runner) -> CoroTask<void> {
+     *              step1();
+     *              co_await JobQueueAwaiter{runner};  // yield + auto-repost
+     *              step2();
+     *              co_await JobQueueAwaiter{runner};
+     *              step3();
+     *              co_return;
+     *          });
+     *
+     *  4. Checking shutdown after co_await (cooperative cancellation):
+     *
+     *      jq.postCoroTask(jtCLIENT, "Cancellable",
+     *          [&jq](auto runner) -> CoroTask<void> {
+     *              while (moreWork()) {
+     *                  co_await JobQueueAwaiter{runner};
+     *                  if (jq.isStopping())
+     *                      co_return;  // bail out cleanly
+     *                  processNextItem();
+     *              }
+     *              co_return;
+     *          });
+     *
+     *  Caveats / Pitfalls
+     *  ==================
+     *
+     *  BUG-RISK: Calling suspend() without a matching post()/resume().
+     *    After co_await runner->suspend(), the coroutine is parked and
+     *    nSuspend_ is incremented.  If nothing ever calls post() or
+     *    resume(), the coroutine is leaked and JobQueue::stop() will
+     *    hang forever waiting for nSuspend_ to reach zero.
+     *
+     *  BUG-RISK: Calling post() on an already-running coroutine.
+     *    post() schedules a resume() job.  If the coroutine has not
+     *    actually suspended yet (no co_await executed), the resume job
+     *    will try to call handle().resume() while the coroutine is still
+     *    running on another thread.  This is UB.  The mutex_ prevents
+     *    data corruption but the logic is wrong — always co_await
+     *    suspend() before calling post().  (The test testIncorrectOrder
+     *    shows this works only because mutex_ serializes the calls.)
+     *
+     *  BUG-RISK: Dropping the shared_ptr<CoroTaskRunner> before join().
+     *    The CoroTaskRunner destructor asserts (!finished_ is false).
+     *    If you let the last shared_ptr die while the coroutine is still
+     *    running or suspended, you get an assertion failure in debug and
+     *    UB in release.  Always call join() or expectEarlyExit() first.
+     *
+     *  BUG-RISK: Lambda captures outliving the coroutine frame.
+     *    The lambda passed to postCoroTask is heap-allocated (FuncStore)
+     *    to prevent dangling.  But objects captured by pointer still need
+     *    their own lifetime management.  If you capture a raw pointer to
+     *    a stack variable, and the stack frame exits before the coroutine
+     *    finishes, the pointer dangles.  Use shared_ptr or ensure the
+     *    pointed-to object outlives the coroutine.
+     *
+     *  BUG-RISK: Forgetting co_return in a void coroutine.
+     *    If the coroutine body falls off the end without co_return,
+     *    the compiler may silently treat it as co_return (per standard),
+     *    but some compilers warn.  Always write explicit co_return.
+     *
+     *  LIMITATION: CoroTaskRunner only supports CoroTask<void>.
+     *    The task_ member is CoroTask<void>.  To return values from
+     *    the top-level coroutine, write through a captured pointer
+     *    (as the tests demonstrate), or co_await inner CoroTask<T>
+     *    coroutines that return values.
+     *
+     *  LIMITATION: One coroutine per CoroTaskRunner.
+     *    init() must be called exactly once.  You cannot reuse a
+     *    CoroTaskRunner to run a second coroutine.  Create a new one
+     *    via postCoroTask() instead.
+     *
+     *  LIMITATION: No timeout on join().
+     *    join() blocks indefinitely.  If the coroutine is suspended
+     *    and never posted, join() will deadlock.  Use timed waits
+     *    on the gate pattern (condition_variable + wait_for) in tests.
+     */
+    class CoroTaskRunner : public std::enable_shared_from_this<CoroTaskRunner>
+    {
+    private:
+        // Per-coroutine thread-local storage. Swapped in before resume()
+        // and swapped out after, so each coroutine sees its own LocalValue
+        // state regardless of which worker thread executes it.
+        detail::LocalValues lvs_;
+
+        // Back-reference to the owning JobQueue. Used to post jobs,
+        // increment/decrement nSuspend_, and acquire jq_.m_mutex.
+        JobQueue& jq_;
+
+        // Job type passed to addJob() when posting this coroutine.
+        JobType type_;
+
+        // Human-readable name for this coroutine job (for logging).
+        std::string name_;
+
+        // True while the coroutine is actively executing on a thread.
+        // Guarded by mutex_run_. join() blocks until this is false.
+        bool running_;
+
+        // Guards task_.handle().resume() to prevent the coroutine from
+        // running on two threads simultaneously. Handles the race where
+        // post() enqueues a resume before the coroutine has actually
+        // suspended (post-before-suspend pattern).
+        std::mutex mutex_;
+
+        // Guards running_ flag. Used with cv_ for join() to wait
+        // until the coroutine finishes its current execution slice.
+        std::mutex mutex_run_;
+
+        // Notified when running_ transitions to false, allowing
+        // join() waiters to wake up.
+        std::condition_variable cv_;
+
+        // The coroutine handle wrapper. Owns the coroutine frame.
+        // Set by init(), reset to empty by expectEarlyExit() on
+        // early termination.
+        CoroTask<void> task_;
+
+        /**
+         * Type-erased base for heap-stored callables.
+         * Prevents the coroutine lambda from being destroyed before
+         * the coroutine frame is done with it.
+         *
+         * @see FuncStore
+         */
+        struct FuncBase
+        {
+            virtual ~FuncBase() = default;
+        };
+
+        /**
+         * Concrete type-erased storage for a callable of type F.
+         * The coroutine frame stores a reference to the lambda's implicit
+         * object parameter. If the lambda is a temporary, that reference
+         * dangles after the call returns. FuncStore keeps it alive on
+         * the heap for the lifetime of the CoroTaskRunner.
+         */
+        template <class F>
+        struct FuncStore : FuncBase
+        {
+            F func;  // The stored callable (coroutine lambda).
+            explicit FuncStore(F&& f) : func(std::move(f))
+            {
+            }
+        };
+
+        // Heap-allocated callable storage. Set by init(), ensures the
+        // lambda outlives the coroutine frame that references it.
+        std::unique_ptr<FuncBase> storedFunc_;
+
+#ifndef NDEBUG
+        // Debug-only flag. True once the coroutine has completed or
+        // expectEarlyExit() was called. Asserted in the destructor
+        // to catch leaked runners.
+        bool finished_ = false;
+#endif
+
+    public:
+        /**
+         * Tag type for private construction. Prevents external code
+         * from constructing CoroTaskRunner directly. Use postCoroTask().
+         */
+        struct create_t
+        {
+            explicit create_t() = default;
+        };
+
+        /**
+         * Construct a CoroTaskRunner. Private by convention (create_t tag).
+         *
+         * @param jq   The JobQueue this coroutine will run on
+         * @param type Job type for scheduling priority
+         * @param name Human-readable name for logging
+         */
+        CoroTaskRunner(create_t, JobQueue&, JobType, std::string const&);
+
+        CoroTaskRunner(CoroTaskRunner const&) = delete;
+        CoroTaskRunner&
+        operator=(CoroTaskRunner const&) = delete;
+
+        /**
+         * Destructor. Asserts (debug) that the coroutine has finished
+         * or expectEarlyExit() was called.
+         */
+        ~CoroTaskRunner();
+
+        /**
+         * Initialize with a coroutine-returning callable.
+         * Must be called exactly once, after the object is managed by
+         * shared_ptr (because init uses shared_from_this internally).
+         * This is handled automatically by postCoroTask().
+         *
+         * @param f Callable: CoroTask<void>(shared_ptr<CoroTaskRunner>)
+         */
+        template <class F>
+        void
+        init(F&& f);
+
+        /**
+         * Increment the JobQueue's suspended-coroutine count (nSuspend_).
+         * Called when the coroutine is about to suspend. Every call
+         * must be balanced by a corresponding decrement (via resume()
+         * or onUndoSuspend()), or JobQueue::stop() will hang.
+         */
+        void
+        onSuspend();
+
+        /**
+         * Decrement nSuspend_ without resuming.
+         * Used to undo onSuspend() when a scheduled post() fails
+         * (e.g. JobQueue is stopping).
+         */
+        void
+        onUndoSuspend();
+
+        /**
+         * Suspend the coroutine.
+         * The awaiter's await_suspend() increments nSuspend_ before the
+         * coroutine actually suspends. The caller must later call post()
+         * or resume() to continue execution.
+         *
+         * @return An awaiter for use with `co_await runner->suspend()`
+         */
+        auto
+        suspend();
+
+        /**
+         * Schedule coroutine resumption as a job on the JobQueue.
+         * Captures shared_from_this() to prevent this runner from being
+         * destroyed while the job is queued.
+         *
+         * @return true if the job was accepted; false if the JobQueue
+         *         is stopping (caller must handle cleanup)
+         */
+        bool
+        post();
+
+        /**
+         * Resume the coroutine on the current thread.
+         * Decrements nSuspend_, swaps in LocalValues, resumes the
+         * coroutine handle, swaps out LocalValues, and notifies join()
+         * waiters. Lock ordering: mutex_run_ -> jq_.m_mutex -> mutex_.
+         */
+        void
+        resume();
+
+        /**
+         * @return true if the coroutine has not yet run to completion
+         */
+        bool
+        runnable() const;
+
+        /**
+         * Handle early termination when the coroutine never ran.
+         * Decrements nSuspend_ and destroys the coroutine frame to
+         * break the shared_ptr cycle (frame -> lambda -> runner -> frame).
+         * Called by postCoroTask() when post() fails.
+         */
+        void
+        expectEarlyExit();
+
+        /**
+         * Block until the coroutine finishes its current execution slice.
+         * Uses cv_ + mutex_run_ to wait until running_ == false.
+         * Warning: deadlocks if the coroutine is suspended and never posted.
+         */
+        void
+        join();
+    };
+
     using JobFunction = std::function<void()>;
 
     JobQueue(
@@ -165,6 +547,19 @@ public:
     std::shared_ptr<Coro>
     postCoro(JobType t, std::string const& name, F&& f);
 
+    /** Creates a C++20 coroutine and adds a job to the queue to run it.
+
+        @param t The type of job.
+        @param name Name of the job.
+        @param f Callable with signature
+            CoroTask<void>(std::shared_ptr<CoroTaskRunner>).
+
+        @return shared_ptr to posted CoroTaskRunner. nullptr if not successful.
+    */
+    template <class F>
+    std::shared_ptr<CoroTaskRunner>
+    postCoroTask(JobType t, std::string const& name, F&& f);
+
     /** Jobs waiting at this priority.
      */
     int
@@ -379,6 +774,7 @@ private:
 }  // namespace xrpl
 
 #include <xrpl/core/Coro.ipp>
+#include <xrpl/core/CoroTaskRunner.ipp>
 
 namespace xrpl {
 
@@ -401,4 +797,54 @@ JobQueue::postCoro(JobType t, std::string const& name, F&& f)
     return coro;
 }
 
+// postCoroTask — entry point for launching a C++20 coroutine on the JobQueue.
+//
+// Control Flow
+// ============
+//
+//   postCoroTask(t, name, f)
+//     |
+//     +-- 1. Create CoroTaskRunner (shared_ptr, ref-counted)
+//     |
+//     +-- 2. runner->init(f)
+//     |        +-- Heap-allocate the lambda (FuncStore) to prevent
+//     |        |   dangling captures in the coroutine frame
+//     |        +-- task_ = f(shared_from_this())
+//     |              [coroutine created but NOT started — lazy initial_suspend]
+//     |
+//     +-- 3. ++nSuspend_   (mirrors Boost Coro ctor's implicit yield)
+//     |        The coroutine is "suspended" from the JobQueue's perspective
+//     |        even though it hasn't run yet — this keeps the JQ shutdown
+//     |        logic correct (it waits for nSuspend_ to reach 0).
+//     |
+//     +-- 4. runner->post()
+//     |        +-- success: job queued, worker will call resume()
+//     |        |            return runner to caller
+//     |        +-- failure: JQ is stopping
+//     |              +-- runner->expectEarlyExit()
+//     |              |     --nSuspend_, destroy coroutine frame
+//     |              +-- return nullptr
+//
+template <class F>
+std::shared_ptr<JobQueue::CoroTaskRunner>
+JobQueue::postCoroTask(JobType t, std::string const& name, F&& f)
+{
+    auto runner = std::make_shared<CoroTaskRunner>(CoroTaskRunner::create_t{}, *this, t, name);
+    runner->init(std::forward<F>(f));
+
+    // Account for the initial suspension (lazy start).
+    // Mirrors the yield() in the Boost Coro constructor.
+    {
+        std::lock_guard lock(m_mutex);
+        ++nSuspend_;
+    }
+
+    if (!runner->post())
+    {
+        runner->expectEarlyExit();
+        runner.reset();
+    }
+    return runner;
+}
+
 }  // namespace xrpl

include/xrpl/core/JobQueueAwaiter.h

@@ -0,0 +1,174 @@
+#pragma once
+
+#include <xrpl/core/JobQueue.h>
+
+#include <coroutine>
+#include <memory>
+
+namespace xrpl {
+
+/**
+ * Awaiter that suspends and immediately reschedules on the JobQueue.
+ * Equivalent to calling yield() followed by post() in the old Coro API.
+ *
+ * Usage:
+ *     co_await JobQueueAwaiter{runner};
+ *
+ * What it waits for: The coroutine is re-queued as a job and resumes
+ * when a worker thread picks it up.
+ *
+ * Which thread resumes: A JobQueue worker thread.
+ *
+ * What await_resume() returns: void.
+ *
+ * Dependency Diagram
+ * ==================
+ *
+ *   JobQueueAwaiter
+ *   +----------------------------------------------+
+ *   | + runner : shared_ptr<CoroTaskRunner>         |
+ *   +----------------------------------------------+
+ *   | + await_ready()   -> false (always suspend)   |
+ *   | + await_suspend() -> bool (suspend or cancel) |
+ *   | + await_resume()  -> void                     |
+ *   +----------------------------------------------+
+ *          |                         |
+ *          | uses                    | uses
+ *          v                         v
+ *   CoroTaskRunner              JobQueue
+ *   .onSuspend()                (via runner->post() -> addJob)
+ *   .onUndoSuspend()
+ *   .post()
+ *
+ * Control Flow (await_suspend)
+ * ============================
+ *
+ *   co_await JobQueueAwaiter{runner}
+ *     |
+ *     +-- await_ready() -> false
+ *     +-- await_suspend(handle)
+ *           |
+ *           +-- runner->onSuspend()     // ++nSuspend_
+ *           +-- runner->post()          // addJob to JobQueue
+ *           |     |
+ *           |     +-- success? return true   // coroutine stays suspended
+ *           |     |                          // worker thread will call resume()
+ *           |     +-- failure? (JQ stopping)
+ *           |           +-- runner->onUndoSuspend()  // --nSuspend_
+ *           |           +-- return false   // coroutine continues immediately
+ *           |                              // so it can clean up and co_return
+ *
+ * Usage Examples
+ * ==============
+ *
+ * 1. Yield and auto-repost (most common -- replaces yield() + post()):
+ *
+ *     CoroTask<void> handler(auto runner) {
+ *         doPartA();
+ *         co_await JobQueueAwaiter{runner};  // yield + repost
+ *         doPartB();                         // runs on a worker thread
+ *         co_return;
+ *     }
+ *
+ * 2. Multiple yield points in a loop:
+ *
+ *     CoroTask<void> batchProcessor(auto runner) {
+ *         for (auto& item : items) {
+ *             process(item);
+ *             co_await JobQueueAwaiter{runner};  // let other jobs run
+ *         }
+ *         co_return;
+ *     }
+ *
+ * 3. Graceful shutdown -- checking after resume:
+ *
+ *     CoroTask<void> longTask(auto runner, JobQueue& jq) {
+ *         while (hasWork()) {
+ *             co_await JobQueueAwaiter{runner};
+ *             // If JQ is stopping, await_suspend returns false and
+ *             // the coroutine continues immediately without re-queuing.
+ *             // Always check isStopping() to decide whether to proceed:
+ *             if (jq.isStopping())
+ *                 co_return;
+ *             doNextChunk();
+ *         }
+ *         co_return;
+ *     }
+ *
+ * Caveats / Pitfalls
+ * ==================
+ *
+ * BUG-RISK: Using a stale or null runner.
+ *   The runner shared_ptr must be valid and point to the CoroTaskRunner
+ *   that owns the coroutine currently executing. Passing a runner from
+ *   a different coroutine, or a default-constructed shared_ptr, is UB.
+ *
+ * BUG-RISK: Assuming resume happens on the same thread.
+ *   After co_await JobQueueAwaiter, the coroutine resumes on whatever
+ *   worker thread picks up the job. Do not rely on thread-local state
+ *   unless it is managed through LocalValue (which CoroTaskRunner
+ *   automatically swaps in/out).
+ *
+ * BUG-RISK: Ignoring the shutdown path.
+ *   When the JobQueue is stopping, post() fails and await_suspend()
+ *   returns false (coroutine does NOT actually suspend). The coroutine
+ *   body continues immediately on the same thread. If your code after
+ *   co_await assumes it was re-queued and is running on a worker thread,
+ *   that assumption breaks during shutdown. Always handle the "JQ is
+ *   stopping" case, either by checking jq.isStopping() or by letting
+ *   the coroutine fall through to co_return naturally.
+ *
+ * DIFFERENCE from runner->suspend() + runner->post():
+ *   JobQueueAwaiter combines both in one atomic operation. With the
+ *   manual suspend()/post() pattern, there is a window between the
+ *   two calls where an external event could race. JobQueueAwaiter
+ *   removes that window -- onSuspend() and post() happen within the
+ *   same await_suspend() call while the coroutine is guaranteed to
+ *   be suspended. Prefer JobQueueAwaiter unless you need an external
+ *   party to decide *when* to call post().
+ */
+struct JobQueueAwaiter
+{
+    // The CoroTaskRunner that owns the currently executing coroutine.
+    std::shared_ptr<JobQueue::CoroTaskRunner> runner;
+
+    /**
+     * Always returns false so the coroutine suspends.
+     */
+    bool
+    await_ready() const noexcept
+    {
+        return false;
+    }
+
+    /**
+     * Increment nSuspend (equivalent to yield()) and schedule resume
+     * on the JobQueue (equivalent to post()). If the JobQueue is
+     * stopping, undoes the suspend count and returns false so the
+     * coroutine continues immediately and can clean up.
+     *
+     * @return true if coroutine should stay suspended (job posted);
+     *         false if coroutine should continue (JQ stopping)
+     */
+    bool
+    await_suspend(std::coroutine_handle<>)
+    {
+        runner->onSuspend();
+        if (!runner->post())
+        {
+            // JobQueue is stopping. Undo the suspend count and
+            // don't actually suspend — the coroutine continues
+            // immediately so it can clean up and co_return.
+            runner->onUndoSuspend();
+            return false;
+        }
+        return true;
+    }
+
+    void
+    await_resume() const noexcept
+    {
+    }
+};
+
+}  // namespace xrpl

include/xrpl/nodestore/Backend.h

@@ -77,16 +77,16 @@ public:
         If the object is not found or an error is encountered, the
         result will indicate the condition.
         @note This will be called concurrently.
-        @param key A pointer to the key data.
+        @param hash The hash of the object.
         @param pObject [out] The created object if successful.
         @return The result of the operation.
     */
     virtual Status
-    fetch(void const* key, std::shared_ptr<NodeObject>* pObject) = 0;
+    fetch(uint256 const& hash, std::shared_ptr<NodeObject>* pObject) = 0;
 
     /** Fetch a batch synchronously. */
     virtual std::pair<std::vector<std::shared_ptr<NodeObject>>, Status>
-    fetchBatch(std::vector<uint256 const*> const& hashes) = 0;
+    fetchBatch(std::vector<uint256> const& hashes) = 0;
 
     /** Store a single object.
         Depending on the implementation this may happen immediately

src/libxrpl/nodestore/DatabaseNodeImp.cpp

@@ -33,7 +33,7 @@ DatabaseNodeImp::fetchNodeObject(
 
     try
     {
-        status = backend_->fetch(hash.data(), &nodeObject);
+        status = backend_->fetch(hash, &nodeObject);
     }
     catch (std::exception const& e)
     {
@@ -68,18 +68,10 @@ DatabaseNodeImp::fetchBatch(std::vector<uint256> const& hashes)
     using namespace std::chrono;
     auto const before = steady_clock::now();
 
-    std::vector<uint256 const*> batch{};
-    batch.reserve(hashes.size());
-    for (size_t i = 0; i < hashes.size(); ++i)
-    {
-        auto const& hash = hashes[i];
-        batch.push_back(&hash);
-    }
-
     // Get the node objects that match the hashes from the backend. To protect
     // against the backends returning fewer or more results than expected, the
     // container is resized to the number of hashes.
-    auto results = backend_->fetchBatch(batch).first;
+    auto results = backend_->fetchBatch(hashes).first;
     XRPL_ASSERT(
         results.size() == hashes.size() || results.empty(),
         "number of output objects either matches number of input hashes or is empty");

src/libxrpl/nodestore/DatabaseRotatingImp.cpp

@@ -105,7 +105,7 @@ DatabaseRotatingImp::fetchNodeObject(
         std::shared_ptr<NodeObject> nodeObject;
         try
         {
-            status = backend->fetch(hash.data(), &nodeObject);
+            status = backend->fetch(hash, &nodeObject);
         }
         catch (std::exception const& e)
         {

src/libxrpl/nodestore/backend/MemoryFactory.cpp

@@ -116,10 +116,9 @@ public:
     //--------------------------------------------------------------------------
 
     Status
-    fetch(void const* key, std::shared_ptr<NodeObject>* pObject) override
+    fetch(uint256 const& hash, std::shared_ptr<NodeObject>* pObject) override
     {
         XRPL_ASSERT(db_, "xrpl::NodeStore::MemoryBackend::fetch : non-null database");
-        uint256 const hash(uint256::fromVoid(key));
 
         std::lock_guard _(db_->mutex);
 
@@ -134,14 +133,14 @@ public:
     }
 
     std::pair<std::vector<std::shared_ptr<NodeObject>>, Status>
-    fetchBatch(std::vector<uint256 const*> const& hashes) override
+    fetchBatch(std::vector<uint256> const& hashes) override
     {
         std::vector<std::shared_ptr<NodeObject>> results;
         results.reserve(hashes.size());
         for (auto const& h : hashes)
         {
             std::shared_ptr<NodeObject> nObj;
-            Status status = fetch(h->begin(), &nObj);
+            Status status = fetch(h, &nObj);
             if (status != ok)
                 results.push_back({});
             else

src/libxrpl/nodestore/backend/NuDBFactory.cpp

@@ -179,17 +179,17 @@ public:
     }
 
     Status
-    fetch(void const* key, std::shared_ptr<NodeObject>* pno) override
+    fetch(uint256 const& hash, std::shared_ptr<NodeObject>* pno) override
     {
         Status status;
         pno->reset();
         nudb::error_code ec;
         db_.fetch(
-            key,
-            [key, pno, &status](void const* data, std::size_t size) {
+            hash.data(),
+            [&hash, pno, &status](void const* data, std::size_t size) {
                 nudb::detail::buffer bf;
                 auto const result = nodeobject_decompress(data, size, bf);
-                DecodedBlob decoded(key, result.first, result.second);
+                DecodedBlob decoded(hash.data(), result.first, result.second);
                 if (!decoded.wasOk())
                 {
                     status = dataCorrupt;
@@ -207,14 +207,14 @@ public:
     }
 
     std::pair<std::vector<std::shared_ptr<NodeObject>>, Status>
-    fetchBatch(std::vector<uint256 const*> const& hashes) override
+    fetchBatch(std::vector<uint256> const& hashes) override
     {
         std::vector<std::shared_ptr<NodeObject>> results;
         results.reserve(hashes.size());
         for (auto const& h : hashes)
         {
             std::shared_ptr<NodeObject> nObj;
-            Status status = fetch(h->begin(), &nObj);
+            Status status = fetch(h, &nObj);
             if (status != ok)
                 results.push_back({});
             else

src/libxrpl/nodestore/backend/NullFactory.cpp

@@ -36,13 +36,13 @@ public:
     }
 
     Status
-    fetch(void const*, std::shared_ptr<NodeObject>*) override
+    fetch(uint256 const&, std::shared_ptr<NodeObject>*) override
     {
         return notFound;
     }
 
     std::pair<std::vector<std::shared_ptr<NodeObject>>, Status>
-    fetchBatch(std::vector<uint256 const*> const& hashes) override
+    fetchBatch(std::vector<uint256> const& hashes) override
     {
         return {};
     }

src/libxrpl/nodestore/backend/RocksDBFactory.cpp

@@ -244,7 +244,7 @@ public:
     //--------------------------------------------------------------------------
 
     Status
-    fetch(void const* key, std::shared_ptr<NodeObject>* pObject) override
+    fetch(uint256 const& hash, std::shared_ptr<NodeObject>* pObject) override
     {
         XRPL_ASSERT(m_db, "xrpl::NodeStore::RocksDBBackend::fetch : non-null database");
         pObject->reset();
@@ -252,7 +252,7 @@ public:
         Status status(ok);
 
         rocksdb::ReadOptions const options;
-        rocksdb::Slice const slice(static_cast<char const*>(key), m_keyBytes);
+        rocksdb::Slice const slice(std::bit_cast<char const*>(hash.data()), m_keyBytes);
 
         std::string string;
 
@@ -260,7 +260,7 @@ public:
 
         if (getStatus.ok())
         {
-            DecodedBlob decoded(key, string.data(), string.size());
+            DecodedBlob decoded(hash.data(), string.data(), string.size());
 
             if (decoded.wasOk())
             {
@@ -295,14 +295,14 @@ public:
     }
 
     std::pair<std::vector<std::shared_ptr<NodeObject>>, Status>
-    fetchBatch(std::vector<uint256 const*> const& hashes) override
+    fetchBatch(std::vector<uint256> const& hashes) override
     {
         std::vector<std::shared_ptr<NodeObject>> results;
         results.reserve(hashes.size());
         for (auto const& h : hashes)
         {
             std::shared_ptr<NodeObject> nObj;
-            Status status = fetch(h->begin(), &nObj);
+            Status status = fetch(h, &nObj);
             if (status != ok)
                 results.push_back({});
             else
@@ -332,9 +332,8 @@ public:
             EncodedBlob encoded(e);
 
             wb.Put(
-                rocksdb::Slice(reinterpret_cast<char const*>(encoded.getKey()), m_keyBytes),
-                rocksdb::Slice(
-                    reinterpret_cast<char const*>(encoded.getData()), encoded.getSize()));
+                rocksdb::Slice(std::bit_cast<char const*>(encoded.getKey()), m_keyBytes),
+                rocksdb::Slice(std::bit_cast<char const*>(encoded.getData()), encoded.getSize()));
         }
 
         rocksdb::WriteOptions const options;

src/test/app/Vault_test.cpp

@@ -5340,20 +5340,20 @@ class Vault_test : public beast::unit_test::suite
             env.close();
 
             // 2. Mantissa larger than uint64 max
+            env.set_parse_failure_expected(true);
             try
             {
                 tx[sfAssetsMaximum] = "18446744073709551617e5";  // uint64 max + 1
                 env(tx, THISLINE);
-                BEAST_EXPECT(false);
+                BEAST_EXPECTS(false, "Expected parse_error for mantissa larger than uint64 max");
             }
             catch (parse_error const& e)
             {
                 using namespace std::string_literals;
                 BEAST_EXPECT(
-                    e.what() ==
-                    "invalidParamsField 'tx_json.AssetsMaximum' has invalid "
-                    "data."s);
+                    e.what() == "invalidParamsField 'tx_json.AssetsMaximum' has invalid data."s);
             }
+            env.set_parse_failure_expected(false);
         }
     }
 

src/test/core/CoroTask_test.cpp

@@ -0,0 +1,537 @@
+#include <test/jtx.h>
+
+#include <xrpl/core/JobQueue.h>
+#include <xrpl/core/JobQueueAwaiter.h>
+
+#include <chrono>
+#include <mutex>
+
+namespace xrpl {
+namespace test {
+
+/**
+ * Test suite for the C++20 coroutine primitives: CoroTask, CoroTaskRunner,
+ * and JobQueueAwaiter.
+ *
+ * Dependency Diagram
+ * ==================
+ *
+ *   CoroTask_test
+ *   +-------------------------------------------------+
+ *   | + gate (inner class) : condition_variable helper |
+ *   +-------------------------------------------------+
+ *          |  uses
+ *          v
+ *   jtx::Env  -->  JobQueue::postCoroTask()
+ *                       |
+ *                       +-- CoroTaskRunner (suspend / post / resume)
+ *                       +-- CoroTask<void> / CoroTask<T>
+ *                       +-- JobQueueAwaiter
+ *
+ * Test Coverage Matrix
+ * ====================
+ *
+ *   Test                      | Primitives exercised
+ *   --------------------------+----------------------------------------------
+ *   testVoidCompletion        | CoroTask<void> basic lifecycle
+ *   testCorrectOrder          | suspend() -> join() -> post() -> complete
+ *   testIncorrectOrder        | post() before suspend() (race-safe path)
+ *   testJobQueueAwaiter       | JobQueueAwaiter suspend + auto-repost
+ *   testThreadSpecificStorage | LocalValue isolation across coroutines
+ *   testExceptionPropagation  | unhandled_exception() in promise_type
+ *   testMultipleYields        | N sequential suspend/resume cycles
+ *   testValueReturn           | CoroTask<T> co_return value
+ *   testValueException        | CoroTask<T> exception via co_await
+ *   testValueChaining         | nested CoroTask<T> -> CoroTask<T>
+ *   testShutdownRejection     | postCoroTask returns nullptr when stopping
+ */
+class CoroTask_test : public beast::unit_test::suite
+{
+public:
+    /**
+     * Simple one-shot gate for synchronizing between test thread
+     * and coroutine worker threads. signal() sets the flag;
+     * wait_for() blocks until signaled or timeout.
+     */
+    class gate
+    {
+    private:
+        std::condition_variable cv_;
+        std::mutex mutex_;
+        bool signaled_ = false;
+
+    public:
+        /**
+         * Block until signaled or timeout expires.
+         *
+         * @param rel_time Maximum duration to wait
+         *
+         * @return true if signaled before timeout
+         */
+        template <class Rep, class Period>
+        bool
+        wait_for(std::chrono::duration<Rep, Period> const& rel_time)
+        {
+            std::unique_lock<std::mutex> lk(mutex_);
+            auto b = cv_.wait_for(lk, rel_time, [this] { return signaled_; });
+            signaled_ = false;
+            return b;
+        }
+
+        /**
+         * Signal the gate, waking any waiting thread.
+         */
+        void
+        signal()
+        {
+            std::lock_guard lk(mutex_);
+            signaled_ = true;
+            cv_.notify_all();
+        }
+    };
+
+    // NOTE: All coroutine lambdas passed to postCoroTask use explicit
+    // pointer-by-value captures instead of [&] to work around a GCC 14
+    // bug where reference captures in coroutine lambdas are corrupted
+    // in the coroutine frame.
+
+    /**
+     * CoroTask<void> runs to completion and runner becomes non-runnable.
+     */
+    void
+    testVoidCompletion()
+    {
+        using namespace std::chrono_literals;
+        using namespace jtx;
+
+        testcase("void completion");
+
+        Env env(*this, envconfig([](std::unique_ptr<Config> cfg) {
+            cfg->FORCE_MULTI_THREAD = true;
+            return cfg;
+        }));
+
+        gate g;
+        auto runner = env.app().getJobQueue().postCoroTask(
+            jtCLIENT, "CoroTaskTest", [gp = &g](auto) -> CoroTask<void> {
+                gp->signal();
+                co_return;
+            });
+        BEAST_EXPECT(runner);
+        BEAST_EXPECT(g.wait_for(5s));
+        runner->join();
+        BEAST_EXPECT(!runner->runnable());
+    }
+
+    /**
+     * Correct order: suspend, join, post, complete.
+     * Mirrors existing Coroutine_test::correct_order.
+     */
+    void
+    testCorrectOrder()
+    {
+        using namespace std::chrono_literals;
+        using namespace jtx;
+
+        testcase("correct order");
+
+        Env env(*this, envconfig([](std::unique_ptr<Config> cfg) {
+            cfg->FORCE_MULTI_THREAD = true;
+            return cfg;
+        }));
+
+        gate g1, g2;
+        std::shared_ptr<JobQueue::CoroTaskRunner> r;
+        auto runner = env.app().getJobQueue().postCoroTask(
+            jtCLIENT,
+            "CoroTaskTest",
+            [rp = &r, g1p = &g1, g2p = &g2](auto runner) -> CoroTask<void> {
+                *rp = runner;
+                g1p->signal();
+                co_await runner->suspend();
+                g2p->signal();
+                co_return;
+            });
+        BEAST_EXPECT(runner);
+        BEAST_EXPECT(g1.wait_for(5s));
+        runner->join();
+        runner->post();
+        BEAST_EXPECT(g2.wait_for(5s));
+        runner->join();
+    }
+
+    /**
+     * Incorrect order: post() before suspend(). Verifies the
+     * race-safe path. Mirrors Coroutine_test::incorrect_order.
+     */
+    void
+    testIncorrectOrder()
+    {
+        using namespace std::chrono_literals;
+        using namespace jtx;
+
+        testcase("incorrect order");
+
+        Env env(*this, envconfig([](std::unique_ptr<Config> cfg) {
+            cfg->FORCE_MULTI_THREAD = true;
+            return cfg;
+        }));
+
+        gate g;
+        env.app().getJobQueue().postCoroTask(
+            jtCLIENT, "CoroTaskTest", [gp = &g](auto runner) -> CoroTask<void> {
+                runner->post();
+                co_await runner->suspend();
+                gp->signal();
+                co_return;
+            });
+        BEAST_EXPECT(g.wait_for(5s));
+    }
+
+    /**
+     * JobQueueAwaiter suspend + auto-repost across multiple yield points.
+     */
+    void
+    testJobQueueAwaiter()
+    {
+        using namespace std::chrono_literals;
+        using namespace jtx;
+
+        testcase("JobQueueAwaiter");
+
+        Env env(*this, envconfig([](std::unique_ptr<Config> cfg) {
+            cfg->FORCE_MULTI_THREAD = true;
+            return cfg;
+        }));
+
+        gate g;
+        int step = 0;
+        env.app().getJobQueue().postCoroTask(
+            jtCLIENT, "CoroTaskTest", [sp = &step, gp = &g](auto runner) -> CoroTask<void> {
+                *sp = 1;
+                co_await JobQueueAwaiter{runner};
+                *sp = 2;
+                co_await JobQueueAwaiter{runner};
+                *sp = 3;
+                gp->signal();
+                co_return;
+            });
+        BEAST_EXPECT(g.wait_for(5s));
+        BEAST_EXPECT(step == 3);
+    }
+
+    /**
+     * Per-coroutine LocalValue isolation. Each coroutine sees its own
+     * copy of thread-local state. Mirrors Coroutine_test::thread_specific_storage.
+     */
+    void
+    testThreadSpecificStorage()
+    {
+        using namespace std::chrono_literals;
+        using namespace jtx;
+
+        testcase("thread specific storage");
+        Env env(*this);
+
+        auto& jq = env.app().getJobQueue();
+
+        static int const N = 4;
+        std::array<std::shared_ptr<JobQueue::CoroTaskRunner>, N> a;
+
+        LocalValue<int> lv(-1);
+        BEAST_EXPECT(*lv == -1);
+
+        gate g;
+        jq.addJob(jtCLIENT, "LocalValTest", [&]() {
+            this->BEAST_EXPECT(*lv == -1);
+            *lv = -2;
+            this->BEAST_EXPECT(*lv == -2);
+            g.signal();
+        });
+        BEAST_EXPECT(g.wait_for(5s));
+        BEAST_EXPECT(*lv == -1);
+
+        for (int i = 0; i < N; ++i)
+        {
+            jq.postCoroTask(
+                jtCLIENT,
+                "CoroTaskTest",
+                [this, ap = &a, gp = &g, lvp = &lv, id = i](auto runner) -> CoroTask<void> {
+                    (*ap)[id] = runner;
+                    gp->signal();
+                    co_await runner->suspend();
+
+                    this->BEAST_EXPECT(**lvp == -1);
+                    **lvp = id;
+                    this->BEAST_EXPECT(**lvp == id);
+                    gp->signal();
+                    co_await runner->suspend();
+
+                    this->BEAST_EXPECT(**lvp == id);
+                    co_return;
+                });
+            BEAST_EXPECT(g.wait_for(5s));
+            a[i]->join();
+        }
+        for (auto const& r : a)
+        {
+            r->post();
+            BEAST_EXPECT(g.wait_for(5s));
+            r->join();
+        }
+        for (auto const& r : a)
+        {
+            r->post();
+            r->join();
+        }
+
+        jq.addJob(jtCLIENT, "LocalValTest", [&]() {
+            this->BEAST_EXPECT(*lv == -2);
+            g.signal();
+        });
+        BEAST_EXPECT(g.wait_for(5s));
+        BEAST_EXPECT(*lv == -1);
+    }
+
+    /**
+     * Exception thrown in coroutine body is caught by
+     * promise_type::unhandled_exception(). Coroutine completes.
+     */
+    void
+    testExceptionPropagation()
+    {
+        using namespace std::chrono_literals;
+        using namespace jtx;
+
+        testcase("exception propagation");
+
+        Env env(*this, envconfig([](std::unique_ptr<Config> cfg) {
+            cfg->FORCE_MULTI_THREAD = true;
+            return cfg;
+        }));
+
+        gate g;
+        auto runner = env.app().getJobQueue().postCoroTask(
+            jtCLIENT, "CoroTaskTest", [gp = &g](auto) -> CoroTask<void> {
+                gp->signal();
+                throw std::runtime_error("test exception");
+                co_return;
+            });
+        BEAST_EXPECT(runner);
+        BEAST_EXPECT(g.wait_for(5s));
+        runner->join();
+        // The exception is caught by promise_type::unhandled_exception()
+        // and the coroutine is considered done
+        BEAST_EXPECT(!runner->runnable());
+    }
+
+    /**
+     * Multiple sequential suspend/resume cycles via co_await.
+     */
+    void
+    testMultipleYields()
+    {
+        using namespace std::chrono_literals;
+        using namespace jtx;
+
+        testcase("multiple yields");
+
+        Env env(*this, envconfig([](std::unique_ptr<Config> cfg) {
+            cfg->FORCE_MULTI_THREAD = true;
+            return cfg;
+        }));
+
+        gate g;
+        int counter = 0;
+        std::shared_ptr<JobQueue::CoroTaskRunner> r;
+        auto runner = env.app().getJobQueue().postCoroTask(
+            jtCLIENT,
+            "CoroTaskTest",
+            [rp = &r, cp = &counter, gp = &g](auto runner) -> CoroTask<void> {
+                *rp = runner;
+                ++(*cp);
+                gp->signal();
+                co_await runner->suspend();
+                ++(*cp);
+                gp->signal();
+                co_await runner->suspend();
+                ++(*cp);
+                gp->signal();
+                co_return;
+            });
+        BEAST_EXPECT(runner);
+
+        BEAST_EXPECT(g.wait_for(5s));
+        BEAST_EXPECT(counter == 1);
+        runner->join();
+
+        runner->post();
+        BEAST_EXPECT(g.wait_for(5s));
+        BEAST_EXPECT(counter == 2);
+        runner->join();
+
+        runner->post();
+        BEAST_EXPECT(g.wait_for(5s));
+        BEAST_EXPECT(counter == 3);
+        runner->join();
+        BEAST_EXPECT(!runner->runnable());
+    }
+
+    /**
+     * CoroTask<T> returns a value via co_return. Outer coroutine
+     * extracts it with co_await.
+     */
+    void
+    testValueReturn()
+    {
+        using namespace std::chrono_literals;
+        using namespace jtx;
+
+        testcase("value return");
+
+        Env env(*this, envconfig([](std::unique_ptr<Config> cfg) {
+            cfg->FORCE_MULTI_THREAD = true;
+            return cfg;
+        }));
+
+        gate g;
+        int result = 0;
+        auto runner = env.app().getJobQueue().postCoroTask(
+            jtCLIENT, "CoroTaskTest", [rp = &result, gp = &g](auto) -> CoroTask<void> {
+                auto inner = []() -> CoroTask<int> { co_return 42; };
+                *rp = co_await inner();
+                gp->signal();
+                co_return;
+            });
+        BEAST_EXPECT(runner);
+        BEAST_EXPECT(g.wait_for(5s));
+        runner->join();
+        BEAST_EXPECT(result == 42);
+        BEAST_EXPECT(!runner->runnable());
+    }
+
+    /**
+     * CoroTask<T> propagates exceptions from inner coroutines.
+     * Outer coroutine catches via try/catch around co_await.
+     */
+    void
+    testValueException()
+    {
+        using namespace std::chrono_literals;
+        using namespace jtx;
+
+        testcase("value exception");
+
+        Env env(*this, envconfig([](std::unique_ptr<Config> cfg) {
+            cfg->FORCE_MULTI_THREAD = true;
+            return cfg;
+        }));
+
+        gate g;
+        bool caught = false;
+        auto runner = env.app().getJobQueue().postCoroTask(
+            jtCLIENT, "CoroTaskTest", [cp = &caught, gp = &g](auto) -> CoroTask<void> {
+                auto inner = []() -> CoroTask<int> {
+                    throw std::runtime_error("inner error");
+                    co_return 0;
+                };
+                try
+                {
+                    co_await inner();
+                }
+                catch (std::runtime_error const& e)
+                {
+                    *cp = true;
+                }
+                gp->signal();
+                co_return;
+            });
+        BEAST_EXPECT(runner);
+        BEAST_EXPECT(g.wait_for(5s));
+        runner->join();
+        BEAST_EXPECT(caught);
+        BEAST_EXPECT(!runner->runnable());
+    }
+
+    /**
+     * CoroTask<T> chaining. Nested value-returning coroutines
+     * compose via co_await.
+     */
+    void
+    testValueChaining()
+    {
+        using namespace std::chrono_literals;
+        using namespace jtx;
+
+        testcase("value chaining");
+
+        Env env(*this, envconfig([](std::unique_ptr<Config> cfg) {
+            cfg->FORCE_MULTI_THREAD = true;
+            return cfg;
+        }));
+
+        gate g;
+        int result = 0;
+        auto runner = env.app().getJobQueue().postCoroTask(
+            jtCLIENT, "CoroTaskTest", [rp = &result, gp = &g](auto) -> CoroTask<void> {
+                auto add = [](int a, int b) -> CoroTask<int> { co_return a + b; };
+                auto mul = [add](int a, int b) -> CoroTask<int> {
+                    int sum = co_await add(a, b);
+                    co_return sum * 2;
+                };
+                *rp = co_await mul(3, 4);
+                gp->signal();
+                co_return;
+            });
+        BEAST_EXPECT(runner);
+        BEAST_EXPECT(g.wait_for(5s));
+        runner->join();
+        BEAST_EXPECT(result == 14);  // (3 + 4) * 2
+        BEAST_EXPECT(!runner->runnable());
+    }
+
+    /**
+     * postCoroTask returns nullptr when JobQueue is stopping.
+     */
+    void
+    testShutdownRejection()
+    {
+        using namespace std::chrono_literals;
+        using namespace jtx;
+
+        testcase("shutdown rejection");
+
+        Env env(*this, envconfig([](std::unique_ptr<Config> cfg) {
+            cfg->FORCE_MULTI_THREAD = true;
+            return cfg;
+        }));
+
+        // Stop the JobQueue
+        env.app().getJobQueue().stop();
+
+        auto runner = env.app().getJobQueue().postCoroTask(
+            jtCLIENT, "CoroTaskTest", [](auto) -> CoroTask<void> { co_return; });
+        BEAST_EXPECT(!runner);
+    }
+
+    void
+    run() override
+    {
+        testVoidCompletion();
+        testCorrectOrder();
+        testIncorrectOrder();
+        testJobQueueAwaiter();
+        testThreadSpecificStorage();
+        testExceptionPropagation();
+        testMultipleYields();
+        testValueReturn();
+        testValueException();
+        testValueChaining();
+        testShutdownRejection();
+    }
+};
+
+BEAST_DEFINE_TESTSUITE(CoroTask, core, xrpl);
+
+}  // namespace test
+}  // namespace xrpl

src/test/nodestore/TestBase.h

@@ -138,7 +138,7 @@ public:
         {
             std::shared_ptr<NodeObject> object;
 
-            Status const status = backend.fetch(batch[i]->getHash().cbegin(), &object);
+            Status const status = backend.fetch(batch[i]->getHash(), &object);
 
             BEAST_EXPECT(status == ok);
 
@@ -158,7 +158,7 @@ public:
         {
             std::shared_ptr<NodeObject> object;
 
-            Status const status = backend.fetch(batch[i]->getHash().cbegin(), &object);
+            Status const status = backend.fetch(batch[i]->getHash(), &object);
 
             BEAST_EXPECT(status == notFound);
         }

src/test/nodestore/Timing_test.cpp

@@ -314,7 +314,7 @@ public:
                     std::shared_ptr<NodeObject> obj;
                     std::shared_ptr<NodeObject> result;
                     obj = seq1_.obj(dist_(gen_));
-                    backend_.fetch(obj->getHash().data(), &result);
+                    backend_.fetch(obj->getHash(), &result);
                     suite_.expect(result && isSame(result, obj));
                 }
                 catch (std::exception const& e)
@@ -377,9 +377,9 @@ public:
             {
                 try
                 {
-                    auto const key = seq2_.key(i);
+                    auto const hash = seq2_.key(i);
                     std::shared_ptr<NodeObject> result;
-                    backend_.fetch(key.data(), &result);
+                    backend_.fetch(hash, &result);
                     suite_.expect(!result);
                 }
                 catch (std::exception const& e)
@@ -449,9 +449,9 @@ public:
                 {
                     if (rand_(gen_) < missingNodePercent)
                     {
-                        auto const key = seq2_.key(dist_(gen_));
+                        auto const hash = seq2_.key(dist_(gen_));
                         std::shared_ptr<NodeObject> result;
-                        backend_.fetch(key.data(), &result);
+                        backend_.fetch(hash, &result);
                         suite_.expect(!result);
                     }
                     else
@@ -459,7 +459,7 @@ public:
                         std::shared_ptr<NodeObject> obj;
                         std::shared_ptr<NodeObject> result;
                         obj = seq1_.obj(dist_(gen_));
-                        backend_.fetch(obj->getHash().data(), &result);
+                        backend_.fetch(obj->getHash(), &result);
                         suite_.expect(result && isSame(result, obj));
                     }
                 }
@@ -540,8 +540,7 @@ public:
                         std::shared_ptr<NodeObject> result;
                         auto const j = older_(gen_);
                         obj = seq1_.obj(j);
-                        std::shared_ptr<NodeObject> result1;
-                        backend_.fetch(obj->getHash().data(), &result);
+                        backend_.fetch(obj->getHash(), &result);
                         suite_.expect(result != nullptr);
                         suite_.expect(isSame(result, obj));
                     }
@@ -559,7 +558,7 @@ public:
                                 std::shared_ptr<NodeObject> result;
                                 auto const j = recent_(gen_);
                                 obj = seq1_.obj(j);
-                                backend_.fetch(obj->getHash().data(), &result);
+                                backend_.fetch(obj->getHash(), &result);
                                 suite_.expect(!result || isSame(result, obj));
                                 break;
                             }