feat(wip): experiment overlayfs

.github/workflows/build-in-docker.yml.disabled

@@ -0,0 +1,95 @@
+name: Build using Docker
+
+on:
+  push:
+    branches: ["dev", "candidate", "release", "jshooks"]
+  pull_request:
+    branches: ["dev", "candidate", "release", "jshooks"]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  DEBUG_BUILD_CONTAINERS_AFTER_CLEANUP: 1
+
+jobs:
+  checkout:
+    runs-on: [self-hosted, vanity]
+    outputs:
+      checkout_path: ${{ steps.vars.outputs.checkout_path }}
+    steps:
+      - name: Prepare checkout path
+        id: vars
+        run: |
+          SAFE_BRANCH=$(echo "${{ github.ref_name }}" | sed -e 's/[^a-zA-Z0-9._-]/-/g')
+          CHECKOUT_PATH="${SAFE_BRANCH}-${{ github.sha }}"
+          echo "checkout_path=${CHECKOUT_PATH}" >> "$GITHUB_OUTPUT"
+
+      - uses: actions/checkout@v4
+        with:
+          path: ${{ steps.vars.outputs.checkout_path }}
+          clean: true
+          fetch-depth: 2 # Only get the last 2 commits, to avoid fetching all history
+
+  build:
+    runs-on: [self-hosted, vanity]
+    needs: [checkout]
+    defaults:
+      run:
+        working-directory: ${{ needs.checkout.outputs.checkout_path }}
+    steps:
+      - name: Set Cleanup Script Path
+        run: |
+          echo "JOB_CLEANUP_SCRIPT=$(mktemp)" >> $GITHUB_ENV
+
+      - name: Build using Docker
+        run: /bin/bash release-builder.sh
+
+      - name: Stop Container (Cleanup)
+        if: always()
+        run: |
+          echo "Running cleanup script: $JOB_CLEANUP_SCRIPT"
+          /bin/bash -e -x "$JOB_CLEANUP_SCRIPT"
+          CLEANUP_EXIT_CODE=$?
+
+          if [[ "$CLEANUP_EXIT_CODE" -eq 0 ]]; then
+            echo "Cleanup script succeeded."
+            rm -f "$JOB_CLEANUP_SCRIPT"
+            echo "Cleanup script removed."
+          else
+            echo "⚠️ Cleanup script failed! Keeping for debugging: $JOB_CLEANUP_SCRIPT"
+          fi
+
+          if [[ "${DEBUG_BUILD_CONTAINERS_AFTER_CLEANUP}" == "1" ]]; then
+            echo "🔍 Checking for leftover containers..."
+            BUILD_CONTAINERS=$(docker ps --format '{{.Names}}' | grep '^xahaud_cached_builder' || echo "")
+
+            if [[ -n "$BUILD_CONTAINERS" ]]; then
+              echo "⚠️ WARNING: Some build containers are still running"
+              echo "$BUILD_CONTAINERS"
+            else
+              echo "✅ No build containers found"
+            fi
+          fi
+
+  tests:
+    runs-on: [self-hosted, vanity]
+    needs: [build, checkout]
+    defaults:
+      run:
+        working-directory: ${{ needs.checkout.outputs.checkout_path }}
+    steps:
+      - name: Unit tests
+        run: /bin/bash docker-unit-tests.sh
+
+  cleanup:
+    runs-on: [self-hosted, vanity]
+    needs: [tests, checkout]
+    if: always()
+    steps:
+      - name: Cleanup workspace
+        run: |
+          CHECKOUT_PATH="${{ needs.checkout.outputs.checkout_path }}"
+          echo "Cleaning workspace for ${CHECKOUT_PATH}"
+          rm -rf "${{ github.workspace }}/${CHECKOUT_PATH}"

.github/workflows/clang-format.yml.disabled

@@ -0,0 +1,72 @@
+name: clang-format
+
+on: [push, pull_request]
+
+jobs:
+  check:
+    runs-on: ubuntu-22.04
+    env:
+      CLANG_VERSION: 10
+    steps:
+    - uses: actions/checkout@v3
+    # - name: Install clang-format
+    #   run: |
+    #     codename=$( lsb_release --codename --short )
+    #     sudo tee /etc/apt/sources.list.d/llvm.list >/dev/null <<EOF
+    #     deb http://apt.llvm.org/${codename}/ llvm-toolchain-${codename}-${CLANG_VERSION} main
+    #     deb-src http://apt.llvm.org/${codename}/ llvm-toolchain-${codename}-${CLANG_VERSION} main
+    #     EOF
+    #     wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add
+    #     sudo apt-get update -y
+    #     sudo apt-get install -y clang-format-${CLANG_VERSION}
+
+    # Temporary fix until this commit is merged
+    # https://github.com/XRPLF/rippled/commit/552377c76f55b403a1c876df873a23d780fcc81c
+    - name: Download and install clang-format
+      run: |
+        sudo apt-get update -y
+        sudo apt-get install -y libtinfo5
+        curl -LO https://github.com/llvm/llvm-project/releases/download/llvmorg-10.0.1/clang+llvm-10.0.1-x86_64-linux-gnu-ubuntu-16.04.tar.xz
+        tar -xf clang+llvm-10.0.1-x86_64-linux-gnu-ubuntu-16.04.tar.xz
+        sudo mv clang+llvm-10.0.1-x86_64-linux-gnu-ubuntu-16.04 /opt/clang-10
+        sudo ln -s /opt/clang-10/bin/clang-format /usr/local/bin/clang-format-10
+    - name: Format src/ripple
+      run: find src/ripple -type f \( -name '*.cpp' -o -name '*.h' -o -name '*.ipp' \) -print0 | xargs -0 clang-format-${CLANG_VERSION} -i
+    - name: Format src/test
+      run: find src/test -type f \( -name '*.cpp' -o -name '*.h' -o -name '*.ipp' \) -print0 | xargs -0 clang-format-${CLANG_VERSION} -i
+    - name: Check for differences
+      id: assert
+      run: |
+        set -o pipefail
+        git diff --exit-code | tee "clang-format.patch"
+    - name: Upload patch
+      if: failure() && steps.assert.outcome == 'failure'
+      uses: actions/upload-artifact@v4
+      continue-on-error: true
+      with:
+        name: clang-format.patch
+        if-no-files-found: ignore
+        path: clang-format.patch
+    - name: What happened?
+      if: failure() && steps.assert.outcome == 'failure'
+      env:
+        PREAMBLE: |
+          If you are reading this, you are looking at a failed Github Actions
+          job.  That means you pushed one or more files that did not conform
+          to the formatting specified in .clang-format. That may be because
+          you neglected to run 'git clang-format' or 'clang-format' before
+          committing, or that your version of clang-format has an
+          incompatibility with the one on this
+          machine, which is:
+        SUGGESTION: |
+
+          To fix it, you can do one of two things:
+          1. Download and apply the patch generated as an artifact of this
+             job to your repo, commit, and push.
+          2. Run 'git-clang-format --extensions c,cpp,h,cxx,ipp dev'
+             in your repo, commit, and push.
+      run: |
+        echo "${PREAMBLE}"
+        clang-format-${CLANG_VERSION} --version
+        echo "${SUGGESTION}"
+        exit 1

.github/workflows/levelization.yml.disabled

@@ -0,0 +1,49 @@
+name: levelization
+
+on: [push, pull_request]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    env:
+      CLANG_VERSION: 10
+    steps:
+    - uses: actions/checkout@v3
+    - name: Check levelization
+      run: Builds/levelization/levelization.sh
+    - name: Check for differences
+      id: assert
+      run: |
+        set -o pipefail
+        git diff --exit-code | tee "levelization.patch"
+    - name: Upload patch
+      if: failure() && steps.assert.outcome == 'failure'
+      uses: actions/upload-artifact@v4
+      continue-on-error: true
+      with:
+        name: levelization.patch
+        if-no-files-found: ignore
+        path: levelization.patch
+    - name: What happened?
+      if: failure() && steps.assert.outcome == 'failure'
+      env:
+        MESSAGE: |
+          If you are reading this, you are looking at a failed Github
+          Actions job. That means you changed the dependency relationships
+          between the modules in rippled. That may be an improvement or a
+          regression. This check doesn't judge.
+
+          A rule of thumb, though, is that if your changes caused
+          something to be removed from loops.txt, that's probably an
+          improvement. If something was added, it's probably a regression.
+
+          To fix it, you can do one of two things:
+          1. Download and apply the patch generated as an artifact of this
+             job to your repo, commit, and push.
+          2. Run './Builds/levelization/levelization.sh' in your repo,
+             commit, and push.
+
+          See Builds/levelization/README.md for more info.
+      run: |
+        echo "${MESSAGE}"
+        exit 1

.github/workflows/test-overlayfs-delta.yml

@@ -0,0 +1,129 @@
+name: Test OverlayFS Delta Extraction
+
+on:
+  push:
+    branches: ["*"]
+  workflow_dispatch:
+
+jobs:
+  test-overlayfs:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Setup OverlayFS layers
+        run: |
+          echo "=== Creating directory structure ==="
+          mkdir -p /tmp/test/{base,delta,upper,work,merged}
+
+          echo "=== Creating base layer files ==="
+          echo "base file 1" > /tmp/test/base/file1.txt
+          echo "base file 2" > /tmp/test/base/file2.txt
+          echo "base file 3" > /tmp/test/base/file3.txt
+          mkdir -p /tmp/test/base/subdir
+          echo "base subdir file" > /tmp/test/base/subdir/file.txt
+
+          echo "=== Base layer contents ==="
+          find /tmp/test/base -type f -exec sh -c 'echo "{}:"; cat "{}"' \;
+
+          echo "=== Mounting OverlayFS ==="
+          sudo mount -t overlay overlay \
+            -o lowerdir=/tmp/test/base,upperdir=/tmp/test/upper,workdir=/tmp/test/work \
+            /tmp/test/merged
+
+          echo "=== Mounted successfully ==="
+          mount | grep overlay
+
+      - name: Verify merged view shows base files
+        run: |
+          echo "=== Contents of /merged (should show base files) ==="
+          ls -R /tmp/test/merged
+          find /tmp/test/merged -type f -exec sh -c 'echo "{}:"; cat "{}"' \;
+
+      - name: Make changes via merged layer
+        run: |
+          echo "=== Making changes via /merged ==="
+
+          # Overwrite existing file
+          echo "MODIFIED file 2" > /tmp/test/merged/file2.txt
+          echo "Modified file2.txt"
+
+          # Create new file
+          echo "NEW file 4" > /tmp/test/merged/file4.txt
+          echo "Created new file4.txt"
+
+          # Create new directory with file
+          mkdir -p /tmp/test/merged/newdir
+          echo "NEW file in new dir" > /tmp/test/merged/newdir/newfile.txt
+          echo "Created newdir/newfile.txt"
+
+          # Add file to existing directory
+          echo "NEW file in existing subdir" > /tmp/test/merged/subdir/newfile.txt
+          echo "Created subdir/newfile.txt"
+
+          echo "=== Changes complete ==="
+
+      - name: Show the delta (upperdir)
+        run: |
+          echo "========================================"
+          echo "THE DELTA (only changes in /upper):"
+          echo "========================================"
+
+          if [ -z "$(ls -A /tmp/test/upper)" ]; then
+            echo "Upper directory is empty - no changes detected"
+          else
+            echo "Upper directory structure:"
+            ls -R /tmp/test/upper
+            echo ""
+            echo "Upper directory files with content:"
+            find /tmp/test/upper -type f -exec sh -c 'echo "---"; echo "FILE: {}"; cat "{}"; echo ""' \;
+
+            echo "========================================"
+            echo "SIZE OF DELTA:"
+            du -sh /tmp/test/upper
+            echo "========================================"
+          fi
+
+      - name: Compare base vs upper vs merged
+        run: |
+          echo "========================================"
+          echo "COMPARISON:"
+          echo "========================================"
+
+          echo "BASE layer (original, untouched):"
+          ls -la /tmp/test/base/
+          echo ""
+
+          echo "UPPER layer (DELTA - only changes):"
+          ls -la /tmp/test/upper/
+          echo ""
+
+          echo "MERGED layer (unified view = base + upper):"
+          ls -la /tmp/test/merged/
+          echo ""
+
+          echo "========================================"
+          echo "PROOF: Upper dir contains ONLY the delta!"
+          echo "========================================"
+
+      - name: Simulate tarball creation (what we'd upload)
+        run: |
+          echo "=== Creating tarball of delta ==="
+          tar -czf /tmp/delta.tar.gz -C /tmp/test/upper .
+
+          echo "Delta tarball size:"
+          ls -lh /tmp/delta.tar.gz
+
+          echo ""
+          echo "Delta tarball contents:"
+          tar -tzf /tmp/delta.tar.gz
+
+          echo ""
+          echo "========================================"
+          echo "This is what we'd upload to S3/rsync!"
+          echo "Only ~few KB instead of entire cache!"
+          echo "========================================"
+
+      - name: Cleanup
+        if: always()
+        run: |
+          echo "=== Unmounting OverlayFS ==="
+          sudo umount /tmp/test/merged || true

.github/workflows/verify-generated-headers.yml.disabled

@@ -0,0 +1,36 @@
+name: Verify Generated Hook Headers
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  verify-generated-headers:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - target: hook/error.h
+            generator: ./hook/generate_error.sh
+          - target: hook/extern.h
+            generator: ./hook/generate_extern.sh
+          - target: hook/sfcodes.h
+            generator: bash ./hook/generate_sfcodes.sh
+          - target: hook/tts.h
+            generator: ./hook/generate_tts.sh
+    runs-on: ubuntu-latest
+    name: ${{ matrix.target }}
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Verify ${{ matrix.target }}
+        run: |
+          set -euo pipefail
+          chmod +x hook/generate_*.sh || true
+
+          tmp=$(mktemp)
+          trap 'rm -f "$tmp"' EXIT
+
+          ${{ matrix.generator }} > "$tmp"
+          diff -u ${{ matrix.target }} "$tmp"

.github/workflows/xahau-ga-macos.yml.disabled

@@ -0,0 +1,149 @@
+name: MacOS - GA Runner
+
+on:
+  push:
+    branches: ["dev", "candidate", "release"]
+  pull_request:
+    branches: ["dev", "candidate", "release"]
+  schedule:
+    - cron: '0 0 * * *'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    strategy:
+      matrix:
+        generator:
+          - Ninja
+        configuration:
+          - Debug
+    runs-on: macos-15
+    env:
+      build_dir: .build
+      # Bump this number to invalidate all caches globally.
+      CACHE_VERSION: 1
+      MAIN_BRANCH_NAME: dev
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install Conan
+        run: |
+          brew install conan
+          # Verify Conan 2 is installed
+          conan --version
+
+      - name: Install Coreutils
+        run: |
+          brew install coreutils
+          echo "Num proc: $(nproc)"
+
+      - name: Install Ninja
+        if: matrix.generator == 'Ninja'
+        run: brew install ninja
+
+      - name: Install Python
+        run: |
+          if which python3 > /dev/null 2>&1; then
+              echo "Python 3 executable exists"
+              python3 --version
+          else
+              brew install python@3.12
+          fi
+          # Create 'python' symlink if it doesn't exist (for tools expecting 'python')
+          if ! which python > /dev/null 2>&1; then
+              sudo ln -sf $(which python3) /usr/local/bin/python
+          fi
+
+      - name: Install CMake
+        run: |
+          # Install CMake 3.x to match local dev environments
+          # With Conan 2 and the policy args passed to CMake, newer versions
+          # can have issues with dependencies that require cmake_minimum_required < 3.5
+          brew uninstall cmake --ignore-dependencies 2>/dev/null || true
+
+          # Download and install CMake 3.31.7 directly
+          curl -L https://github.com/Kitware/CMake/releases/download/v3.31.7/cmake-3.31.7-macos-universal.tar.gz -o cmake.tar.gz
+          tar -xzf cmake.tar.gz
+
+          # Move the entire CMake.app to /Applications
+          sudo mv cmake-3.31.7-macos-universal/CMake.app /Applications/
+
+          echo "/Applications/CMake.app/Contents/bin" >> $GITHUB_PATH
+          /Applications/CMake.app/Contents/bin/cmake --version
+
+      - name: Install ccache
+        run: brew install ccache
+
+      - name: Configure ccache
+        uses: ./.github/actions/xahau-configure-ccache
+        with:
+          max_size: 2G
+          hash_dir: true
+          compiler_check: content
+          is_main_branch: ${{ github.ref_name == env.MAIN_BRANCH_NAME }}
+
+      - name: Check environment
+        run: |
+          echo "PATH:"
+          echo "${PATH}" | tr ':' '\n'
+          which python && python --version || echo "Python not found"
+          which conan && conan --version || echo "Conan not found"
+          which cmake && cmake --version || echo "CMake not found"
+          clang --version
+          ccache --version
+          echo "---- Full Environment ----"
+          env
+
+      - name: Configure Conan
+        run: |
+          # Create the default profile directory if it doesn't exist
+          mkdir -p ~/.conan2/profiles
+
+          # Detect compiler version
+          COMPILER_VERSION=$(clang --version | grep -oE 'version [0-9]+' | grep -oE '[0-9]+')
+
+          # Create profile with our specific settings
+          cat > ~/.conan2/profiles/default <<EOF
+          [settings]
+          arch=armv8
+          build_type=Release
+          compiler=apple-clang
+          compiler.cppstd=20
+          compiler.libcxx=libc++
+          compiler.version=${COMPILER_VERSION}
+          os=Macos
+
+          [conf]
+          # Workaround for gRPC with newer Apple Clang
+          tools.build:cxxflags=["-Wno-missing-template-arg-list-after-template-kw"]
+          EOF
+
+          # Display profile for verification
+          conan profile show
+
+      - name: Install dependencies
+        uses: ./.github/actions/xahau-ga-dependencies
+        with:
+          configuration: ${{ matrix.configuration }}
+          build_dir: ${{ env.build_dir }}
+          compiler-id: clang
+          cache_version: ${{ env.CACHE_VERSION }}
+          main_branch: ${{ env.MAIN_BRANCH_NAME }}
+
+      - name: Build
+        uses: ./.github/actions/xahau-ga-build
+        with:
+          generator: ${{ matrix.generator }}
+          configuration: ${{ matrix.configuration }}
+          build_dir: ${{ env.build_dir }}
+          compiler-id: clang
+          cache_version: ${{ env.CACHE_VERSION }}
+          main_branch: ${{ env.MAIN_BRANCH_NAME }}
+
+      - name: Test
+        run: |
+          ${{ env.build_dir }}/rippled --unittest --unittest-jobs $(nproc)

.github/workflows/xahau-ga-nix.yml.disabled

@@ -0,0 +1,332 @@
+name: Nix - GA Runner
+
+on:
+  push:
+    branches: ["dev", "candidate", "release"]
+  pull_request:
+    branches: ["dev", "candidate", "release"]
+  schedule:
+    - cron: '0 0 * * *'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  matrix-setup:
+    runs-on: ubuntu-latest
+    container: python:3-slim
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    steps:
+      - name: Generate build matrix
+        id: set-matrix
+        shell: python
+        run: |
+          import json
+          import os
+          
+          # Full matrix with all 6 compiler configurations
+          # Each configuration includes all parameters needed by the build job
+          full_matrix = [
+              {
+                  "compiler_id": "gcc-11-libstdcxx",
+                  "compiler": "gcc",
+                  "cc": "gcc-11",
+                  "cxx": "g++-11",
+                  "compiler_version": 11,
+                  "stdlib": "libstdcxx",
+                  "configuration": "Debug"
+              },
+              {
+                  "compiler_id": "gcc-13-libstdcxx",
+                  "compiler": "gcc",
+                  "cc": "gcc-13",
+                  "cxx": "g++-13",
+                  "compiler_version": 13,
+                  "stdlib": "libstdcxx",
+                  "configuration": "Debug"
+              },
+              {
+                  "compiler_id": "clang-14-libstdcxx-gcc11",
+                  "compiler": "clang",
+                  "cc": "clang-14",
+                  "cxx": "clang++-14",
+                  "compiler_version": 14,
+                  "stdlib": "libstdcxx",
+                  "clang_gcc_toolchain": 11,
+                  "configuration": "Debug"
+              },
+              {
+                  "compiler_id": "clang-16-libstdcxx-gcc13",
+                  "compiler": "clang",
+                  "cc": "clang-16",
+                  "cxx": "clang++-16",
+                  "compiler_version": 16,
+                  "stdlib": "libstdcxx",
+                  "clang_gcc_toolchain": 13,
+                  "configuration": "Debug"
+              },
+              {
+                  "compiler_id": "clang-17-libcxx",
+                  "compiler": "clang",
+                  "cc": "clang-17",
+                  "cxx": "clang++-17",
+                  "compiler_version": 17,
+                  "stdlib": "libcxx",
+                  "configuration": "Debug"
+              },
+              {
+                  # Clang 18 - testing if it's faster than Clang 17 with libc++
+                  # Requires patching Conan v1 settings.yml to add version 18
+                  "compiler_id": "clang-18-libcxx",
+                  "compiler": "clang",
+                  "cc": "clang-18",
+                  "cxx": "clang++-18",
+                  "compiler_version": 18,
+                  "stdlib": "libcxx",
+                  "configuration": "Debug"
+              }
+          ]
+          
+          # Minimal matrix for PRs and feature branches
+          minimal_matrix = [
+              full_matrix[1],  # gcc-13 (middle-ground gcc)
+              full_matrix[2]   # clang-14 (mature, stable clang)
+          ]
+          
+          # Determine which matrix to use based on the target branch
+          ref = "${{ github.ref }}"
+          base_ref = "${{ github.base_ref }}"  # For PRs, this is the target branch
+          event_name = "${{ github.event_name }}"
+          commit_message = """${{ github.event.head_commit.message }}"""
+          pr_title = """${{ github.event.pull_request.title }}"""
+          
+          # Debug logging
+          print(f"Event: {event_name}")
+          print(f"Ref: {ref}")
+          print(f"Base ref: {base_ref}")
+          print(f"PR title: {pr_title}")
+          print(f"Commit message: {commit_message}")
+          
+          # Check for override tags in commit message or PR title
+          force_full = "[ci-nix-full-matrix]" in commit_message or "[ci-nix-full-matrix]" in pr_title
+          print(f"Force full matrix: {force_full}")
+          
+          # Check if this is targeting a main branch
+          # For PRs: check base_ref (target branch)
+          # For pushes: check ref (current branch)
+          main_branches = ["refs/heads/dev", "refs/heads/release", "refs/heads/candidate"]
+          
+          if force_full:
+              # Override: always use full matrix if tag is present
+              use_full = True
+          elif event_name == "pull_request":
+              # For PRs, base_ref is just the branch name (e.g., "dev", not "refs/heads/dev")
+              # Check if the PR targets release or candidate (more critical branches)
+              use_full = base_ref in ["release", "candidate"]
+          else:
+              # For pushes, ref is the full reference (e.g., "refs/heads/dev")
+              use_full = ref in main_branches
+          
+          # Select the appropriate matrix
+          if use_full:
+              if force_full:
+                  print(f"Using FULL matrix (6 configs) - forced by [ci-nix-full-matrix] tag")
+              else:
+                  print(f"Using FULL matrix (6 configs) - targeting main branch")
+              matrix = full_matrix
+          else:
+              print(f"Using MINIMAL matrix (2 configs) - feature branch/PR")
+              matrix = minimal_matrix
+          
+          # Output the matrix as JSON
+          output = json.dumps({"include": matrix})
+          with open(os.environ['GITHUB_OUTPUT'], 'a') as f:
+              f.write(f"matrix={output}\n")
+
+  build:
+    needs: matrix-setup
+    runs-on: ubuntu-latest
+    outputs:
+      artifact_name: ${{ steps.set-artifact-name.outputs.artifact_name }}
+    strategy:
+      fail-fast: false
+      matrix: ${{ fromJSON(needs.matrix-setup.outputs.matrix) }}
+    env:
+      build_dir: .build
+      # Bump this number to invalidate all caches globally.
+      CACHE_VERSION: 2
+      MAIN_BRANCH_NAME: dev
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install build dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y ninja-build ${{ matrix.cc }} ${{ matrix.cxx }} ccache
+
+          # Install the specific GCC version needed for Clang
+          if [ -n "${{ matrix.clang_gcc_toolchain }}" ]; then
+            echo "=== Installing GCC ${{ matrix.clang_gcc_toolchain }} for Clang ==="
+            sudo apt-get install -y gcc-${{ matrix.clang_gcc_toolchain }} g++-${{ matrix.clang_gcc_toolchain }} libstdc++-${{ matrix.clang_gcc_toolchain }}-dev
+
+            echo "=== GCC versions available after installation ==="
+            ls -la /usr/lib/gcc/x86_64-linux-gnu/ | grep -E "^d"
+          fi
+
+          # For Clang < 16 with --gcc-toolchain, hide newer GCC versions
+          # This is needed because --gcc-toolchain still picks the highest version
+          #
+          # THE GREAT GCC HIDING TRICK (for Clang < 16):
+          # Clang versions before 16 don't have --gcc-install-dir, only --gcc-toolchain
+          # which is deprecated and still uses discovery heuristics that ALWAYS pick
+          # the highest version number. So we play a sneaky game...
+          #
+          # We rename newer GCC versions to very low integers (1, 2, 3...) which makes
+          # Clang think they're ancient GCC versions. Since 11 > 3 > 2 > 1, Clang will
+          # pick GCC 11 over our renamed versions. It's dumb but it works!
+          #
+          # Example: GCC 12→1, GCC 13→2, GCC 14→3, so Clang picks 11 (highest number)
+          if [ -n "${{ matrix.clang_gcc_toolchain }}" ] && [ "${{ matrix.compiler_version }}" -lt "16" ]; then
+            echo "=== Hiding GCC versions newer than ${{ matrix.clang_gcc_toolchain }} for Clang < 16 ==="
+            target_version=${{ matrix.clang_gcc_toolchain }}
+            counter=1  # Start with 1 - these will be seen as "GCC version 1, 2, 3" etc
+            for dir in /usr/lib/gcc/x86_64-linux-gnu/*/; do
+              if [ -d "$dir" ]; then
+                version=$(basename "$dir")
+                # Check if version is numeric and greater than target
+                if [[ "$version" =~ ^[0-9]+$ ]] && [ "$version" -gt "$target_version" ]; then
+                  echo "Hiding GCC $version -> renaming to $counter (will be seen as GCC version $counter)"
+                  # Safety check: ensure target doesn't already exist
+                  if [ ! -e "/usr/lib/gcc/x86_64-linux-gnu/$counter" ]; then
+                    sudo mv "$dir" "/usr/lib/gcc/x86_64-linux-gnu/$counter"
+                  else
+                    echo "ERROR: Cannot rename GCC $version - /usr/lib/gcc/x86_64-linux-gnu/$counter already exists"
+                    exit 1
+                  fi
+                  counter=$((counter + 1))
+                fi
+              fi
+            done
+          fi
+
+          # Verify what Clang will use
+          if [ -n "${{ matrix.clang_gcc_toolchain }}" ]; then
+            echo "=== Verifying GCC toolchain selection ==="
+            echo "Available GCC versions:"
+            ls -la /usr/lib/gcc/x86_64-linux-gnu/ | grep -E "^d.*[0-9]+$" || true
+
+            echo ""
+            echo "Clang's detected GCC installation:"
+            ${{ matrix.cxx }} -v -E -x c++ /dev/null -o /dev/null 2>&1 | grep "Found candidate GCC installation" || true
+          fi
+
+          # Install libc++ dev packages if using libc++ (not needed for libstdc++)
+          if [ "${{ matrix.stdlib }}" = "libcxx" ]; then
+            sudo apt-get install -y libc++-${{ matrix.compiler_version }}-dev libc++abi-${{ matrix.compiler_version }}-dev
+          fi
+
+          # Install Conan 2
+          pip install --upgrade "conan>=2.0,<3"
+
+      - name: Configure ccache
+        uses: ./.github/actions/xahau-configure-ccache
+        with:
+          max_size: 2G
+          hash_dir: true
+          compiler_check: content
+          is_main_branch: ${{ github.ref_name == env.MAIN_BRANCH_NAME }}
+
+      - name: Configure Conan
+        run: |
+          # Create the default profile directory if it doesn't exist
+          mkdir -p ~/.conan2/profiles
+
+          # Determine the correct libcxx based on stdlib parameter
+          if [ "${{ matrix.stdlib }}" = "libcxx" ]; then
+            LIBCXX="libc++"
+          else
+            LIBCXX="libstdc++11"
+          fi
+
+          # Create profile with our specific settings
+          cat > ~/.conan2/profiles/default <<EOF
+          [settings]
+          arch=x86_64
+          build_type=${{ matrix.configuration }}
+          compiler=${{ matrix.compiler }}
+          compiler.cppstd=20
+          compiler.libcxx=${LIBCXX}
+          compiler.version=${{ matrix.compiler_version }}
+          os=Linux
+
+          [buildenv]
+          CC=/usr/bin/${{ matrix.cc }}
+          CXX=/usr/bin/${{ matrix.cxx }}
+
+          [conf]
+          tools.build:compiler_executables={"c": "/usr/bin/${{ matrix.cc }}", "cpp": "/usr/bin/${{ matrix.cxx }}"}
+          EOF
+
+          # Display profile for verification
+          conan profile show
+
+      - name: Check environment
+        run: |
+          echo "PATH:"
+          echo "${PATH}" | tr ':' '\n'
+          which conan && conan --version || echo "Conan not found"
+          which cmake && cmake --version || echo "CMake not found"
+          which ${{ matrix.cc }} && ${{ matrix.cc }} --version || echo "${{ matrix.cc }} not found"
+          which ${{ matrix.cxx }} && ${{ matrix.cxx }} --version || echo "${{ matrix.cxx }} not found"
+          which ccache && ccache --version || echo "ccache not found"
+          echo "---- Full Environment ----"
+          env
+
+      - name: Install dependencies
+        uses: ./.github/actions/xahau-ga-dependencies
+        with:
+          configuration: ${{ matrix.configuration }}
+          build_dir: ${{ env.build_dir }}
+          compiler-id: ${{ matrix.compiler_id }}
+          cache_version: ${{ env.CACHE_VERSION }}
+          main_branch: ${{ env.MAIN_BRANCH_NAME }}
+          stdlib: ${{ matrix.stdlib }}
+
+      - name: Build
+        uses: ./.github/actions/xahau-ga-build
+        with:
+          generator: Ninja
+          configuration: ${{ matrix.configuration }}
+          build_dir: ${{ env.build_dir }}
+          cc: ${{ matrix.cc }}
+          cxx: ${{ matrix.cxx }}
+          compiler-id: ${{ matrix.compiler_id }}
+          cache_version: ${{ env.CACHE_VERSION }}
+          main_branch: ${{ env.MAIN_BRANCH_NAME }}
+          stdlib: ${{ matrix.stdlib }}
+          clang_gcc_toolchain: ${{ matrix.clang_gcc_toolchain || '' }}
+
+      - name: Set artifact name
+        id: set-artifact-name
+        run: |
+          ARTIFACT_NAME="build-output-nix-${{ github.run_id }}-${{ matrix.compiler }}-${{ matrix.configuration }}"
+          echo "artifact_name=${ARTIFACT_NAME}" >> "$GITHUB_OUTPUT"
+          echo "Using artifact name: ${ARTIFACT_NAME}"
+
+      - name: Debug build directory
+        run: |
+          echo "Checking build directory contents: ${{ env.build_dir }}"
+          ls -la ${{ env.build_dir }} || echo "Build directory not found or empty"
+
+      - name: Run tests
+        run: |
+          # Ensure the binary exists before trying to run
+          if [ -f "${{ env.build_dir }}/rippled" ]; then
+            ${{ env.build_dir }}/rippled --unittest --unittest-jobs $(nproc)
+          else
+             echo "Error: rippled executable not found in ${{ env.build_dir }}"
+             exit 1
+          fi