feat: replace github actions cache with s3

Replaces actions/cache with custom S3-based caching to avoid upcoming
GitHub Actions cache eviction policy changes.

Changes:
- New S3 cache actions (xahau-ga-cache-restore/save)
- zstd compression (ccache: clang=323/gcc=609 MB, Conan: clang=1.1/gcc=1.9 GB)
- Immutability (first-write-wins)
- Bootstrap mode (creates empty dir if no cache)

Cache clearing tag:
- [ci-ga-clear-cache] - Clear all caches for this job
- [ci-ga-clear-cache:ccache] - Clear only ccache
- [ci-ga-clear-cache:conan] - Clear only conan

Configuration ordering fixes:
- ccache config applied AFTER cache restore (prevents stale cached config)
- Conan profile created AFTER cache restore (prevents stale cached profile)

ccache improvements:
- Single cache directory (~/.ccache)
- Wrapper toolchain (enables ccache without affecting Conan builds)
- Verbose build output (-v flag)
- Fixes #620

Conan improvements:
- Removed branch comparison logic for cache saves
- Cache keys don't include branch names, comparison was ineffective
- Fixes #618

Breaking changes:
- Workflows must pass AWS credentials (aws-access-key-id, aws-secret-access-key)

S3 setup:
- Bucket: xahaud-github-actions-cache-niq (us-east-1)
- Credentials already configured in GitHub secrets

.github/actions/xahau-configure-ccache/action.yml

@@ -1,63 +0,0 @@
-name: 'Configure ccache'
-description: 'Sets up ccache with consistent configuration'
-
-inputs:
-  max_size:
-    description: 'Maximum cache size'
-    required: false
-    default: '2G'
-  hash_dir:
-    description: 'Whether to include directory paths in hash'
-    required: false
-    default: 'true'
-  compiler_check:
-    description: 'How to check compiler for changes'
-    required: false
-    default: 'content'
-  is_main_branch:
-    description: 'Whether the current branch is the main branch'
-    required: false
-    default: 'false'
-  main_cache_dir:
-    description: 'Path to the main branch cache directory'
-    required: false
-    default: '~/.ccache-main'
-  current_cache_dir:
-    description: 'Path to the current branch cache directory'
-    required: false
-    default: '~/.ccache-current'
-
-runs:
-  using: 'composite'
-  steps:
-    - name: Configure ccache
-      shell: bash
-      run: |
-        # Create cache directories
-        mkdir -p ${{ inputs.main_cache_dir }} ${{ inputs.current_cache_dir }}
-        
-        # Set compiler check globally
-        ccache -o compiler_check=${{ inputs.compiler_check }}
-        
-        # Use a single config file location
-        mkdir -p ~/.ccache
-        export CONF_PATH="$HOME/.ccache/ccache.conf"
-        
-        # Apply common settings
-        echo "max_size = ${{ inputs.max_size }}" > "$CONF_PATH"
-        echo "hash_dir = ${{ inputs.hash_dir }}" >> "$CONF_PATH"
-        echo "compiler_check = ${{ inputs.compiler_check }}" >> "$CONF_PATH"
-        
-        if [ "${{ inputs.is_main_branch }}" == "true" ]; then
-          # Main branch: use main branch cache
-          ccache --set-config=cache_dir="${{ inputs.main_cache_dir }}"
-          echo "CCACHE_DIR=${{ inputs.main_cache_dir }}" >> $GITHUB_ENV
-        else
-          # Feature branch: use current branch cache with main as secondary
-          ccache --set-config=cache_dir="${{ inputs.current_cache_dir }}"
-          ccache --set-config=secondary_storage="file:${{ inputs.main_cache_dir }}"
-          echo "CCACHE_DIR=${{ inputs.current_cache_dir }}" >> $GITHUB_ENV
-        fi
-        
-        ccache -p # Print config for verification
-        ccache -z # Zero statistics before the build

.github/actions/xahau-ga-build/action.yml

@@ -47,6 +47,24 @@ inputs:
     description: 'GCC version to use for Clang toolchain (e.g. 11, 13)'
     required: false
     default: ''
+  ccache_max_size:
+    description: 'Maximum ccache size'
+    required: false
+    default: '2G'
+  ccache_hash_dir:
+    description: 'Whether to include directory paths in hash'
+    required: false
+    default: 'true'
+  ccache_compiler_check:
+    description: 'How to check compiler for changes'
+    required: false
+    default: 'content'
+  aws-access-key-id:
+    description: 'AWS Access Key ID for S3 cache storage'
+    required: true
+  aws-secret-access-key:
+    description: 'AWS Secret Access Key for S3 cache storage'
+    required: true
 
 runs:
   using: 'composite'
@@ -59,28 +77,44 @@ runs:
         SAFE_BRANCH=$(echo "${{ github.ref_name }}" | tr -c 'a-zA-Z0-9_.-' '-')
         echo "name=${SAFE_BRANCH}" >> $GITHUB_OUTPUT
 
-    - name: Restore ccache directory for default branch
+    - name: Restore ccache directory
       if: inputs.ccache_enabled == 'true'
       id: ccache-restore
-      uses: actions/cache/restore@v4
+      uses: ./.github/actions/xahau-ga-cache-restore
       with:
-        path: ~/.ccache-main
-        key: ${{ runner.os }}-ccache-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.configuration }}-${{ inputs.main_branch }}
-        restore-keys: |
-          ${{ runner.os }}-ccache-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.configuration }}-
-          ${{ runner.os }}-ccache-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-
-
-    - name: Restore ccache directory for current branch
-      if: inputs.ccache_enabled == 'true' && steps.safe-branch.outputs.name != inputs.main_branch
-      id: ccache-restore-current-branch
-      uses: actions/cache/restore@v4
-      with:
-        path: ~/.ccache-current
+        path: ~/.ccache
         key: ${{ runner.os }}-ccache-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.configuration }}-${{ steps.safe-branch.outputs.name }}
         restore-keys: |
           ${{ runner.os }}-ccache-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.configuration }}-${{ inputs.main_branch }}
           ${{ runner.os }}-ccache-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.configuration }}-
           ${{ runner.os }}-ccache-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-
+        aws-access-key-id: ${{ inputs.aws-access-key-id }}
+        aws-secret-access-key: ${{ inputs.aws-secret-access-key }}
+
+    - name: Configure ccache
+      if: inputs.ccache_enabled == 'true'
+      shell: bash
+      run: |
+        # Use ccache's default cache_dir (~/.ccache) - don't override it
+        # This avoids tilde expansion issues when setting it explicitly
+
+        # Create cache directory using ccache's default
+        mkdir -p ~/.ccache
+
+        # Configure ccache settings (but NOT cache_dir - use default)
+        # This overwrites any cached config to ensure fresh configuration
+        ccache --set-config=max_size=${{ inputs.ccache_max_size }}
+        ccache --set-config=hash_dir=${{ inputs.ccache_hash_dir }}
+        ccache --set-config=compiler_check=${{ inputs.ccache_compiler_check }}
+
+        # Note: Not setting CCACHE_DIR - let ccache use its default (~/.ccache)
+
+        # Print config for verification
+        echo "=== ccache configuration ==="
+        ccache -p
+
+        # Zero statistics before the build
+        ccache -z
 
     - name: Configure project
       shell: bash
@@ -96,14 +130,27 @@ runs:
         if [ -n "${{ inputs.cxx }}" ]; then
           export CXX="${{ inputs.cxx }}"
         fi
-        
-        
-        # Configure ccache launcher args
-        CCACHE_ARGS=""
+
+        # Create wrapper toolchain that overlays ccache on top of Conan's toolchain
+        # This enables ccache for the main app build without affecting Conan dependency builds
         if [ "${{ inputs.ccache_enabled }}" = "true" ]; then
-          CCACHE_ARGS="-DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache"
+          cat > wrapper_toolchain.cmake <<'EOF'
+        # Include Conan's generated toolchain first (sets compiler, flags, etc.)
+        # Note: CMAKE_CURRENT_LIST_DIR is the directory containing this wrapper (.build/)
+        include(${CMAKE_CURRENT_LIST_DIR}/build/generators/conan_toolchain.cmake)
+
+        # Overlay ccache configuration for main application build
+        # This does NOT affect Conan dependency builds (already completed)
+        set(CMAKE_C_COMPILER_LAUNCHER ccache CACHE STRING "C compiler launcher" FORCE)
+        set(CMAKE_CXX_COMPILER_LAUNCHER ccache CACHE STRING "C++ compiler launcher" FORCE)
+        EOF
+          TOOLCHAIN_FILE="wrapper_toolchain.cmake"
+          echo "✅ Created wrapper toolchain with ccache enabled"
+        else
+          TOOLCHAIN_FILE="build/generators/conan_toolchain.cmake"
+          echo "ℹ️  Using Conan toolchain directly (ccache disabled)"
         fi
-        
+
         # Configure C++ standard library if specified
         # libstdcxx used for clang-14/16 to work around missing lexicographical_compare_three_way in libc++
         # libcxx can be used with clang-17+ which has full C++20 support
@@ -143,32 +190,44 @@ runs:
         # So we get: .build/build/generators/ with our non-standard folder name
         cmake .. \
           -G "${{ inputs.generator }}" \
-          $CCACHE_ARGS \
           ${CMAKE_CXX_FLAGS:+-DCMAKE_CXX_FLAGS="$CMAKE_CXX_FLAGS"} \
-          -DCMAKE_TOOLCHAIN_FILE:FILEPATH=build/generators/conan_toolchain.cmake \
+          -DCMAKE_TOOLCHAIN_FILE:FILEPATH=${TOOLCHAIN_FILE} \
           -DCMAKE_BUILD_TYPE=${{ inputs.configuration }}
 
+    - name: Show ccache config before build
+      if: inputs.ccache_enabled == 'true'
+      shell: bash
+      run: |
+        echo "=========================================="
+        echo "ccache configuration before build"
+        echo "=========================================="
+        ccache -p
+        echo ""
+
     - name: Build project
       shell: bash
       run: |
         cd ${{ inputs.build_dir }}
-        cmake --build . --config ${{ inputs.configuration }} --parallel $(nproc)
+
+        # Check for verbose build flag in commit message
+        VERBOSE_FLAG=""
+        if echo "${XAHAU_GA_COMMIT_MSG}" | grep -q '\[ci-ga-cmake-verbose\]'; then
+          echo "🔊 [ci-ga-cmake-verbose] detected - enabling verbose output"
+          VERBOSE_FLAG="-- -v"
+        fi
+
+        cmake --build . --config ${{ inputs.configuration }} --parallel $(nproc) ${VERBOSE_FLAG}
 
     - name: Show ccache statistics
       if: inputs.ccache_enabled == 'true'
       shell: bash
       run: ccache -s
 
-    - name: Save ccache directory for default branch
-      if: always() && inputs.ccache_enabled == 'true' && steps.safe-branch.outputs.name == inputs.main_branch
-      uses: actions/cache/save@v4
+    - name: Save ccache directory
+      if: success() && inputs.ccache_enabled == 'true'
+      uses: ./.github/actions/xahau-ga-cache-save
       with:
-        path: ~/.ccache-main
-        key: ${{ steps.ccache-restore.outputs.cache-primary-key }}
-
-    - name: Save ccache directory for current branch
-      if: always() && inputs.ccache_enabled == 'true' && steps.safe-branch.outputs.name != inputs.main_branch
-      uses: actions/cache/save@v4
-      with:
-        path: ~/.ccache-current
-        key: ${{ steps.ccache-restore-current-branch.outputs.cache-primary-key }}
+        path: ~/.ccache
+        key: ${{ runner.os }}-ccache-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.configuration }}-${{ steps.safe-branch.outputs.name }}
+        aws-access-key-id: ${{ inputs.aws-access-key-id }}
+        aws-secret-access-key: ${{ inputs.aws-secret-access-key }}

.github/actions/xahau-ga-cache-restore/action.yml

@@ -0,0 +1,291 @@
+name: 'Xahau Cache Restore (S3)'
+bump: 1
+description: 'Drop-in replacement for actions/cache/restore using S3 storage'
+
+inputs:
+  path:
+    description: 'A list of files, directories, and wildcard patterns to cache (currently only single path supported)'
+    required: true
+  key:
+    description: 'An explicit key for restoring the cache'
+    required: true
+  restore-keys:
+    description: 'An ordered list of prefix-matched keys to use for restoring stale cache if no cache hit occurred for key'
+    required: false
+    default: ''
+  s3-bucket:
+    description: 'S3 bucket name for cache storage'
+    required: false
+    default: 'xahaud-github-actions-cache-niq'
+  s3-region:
+    description: 'S3 region'
+    required: false
+    default: 'us-east-1'
+  fail-on-cache-miss:
+    description: 'Fail the workflow if cache entry is not found'
+    required: false
+    default: 'false'
+  lookup-only:
+    description: 'Check if a cache entry exists for the given input(s) without downloading it'
+    required: false
+    default: 'false'
+  # Note: Composite actions can't access secrets.* directly - must be passed from workflow
+  aws-access-key-id:
+    description: 'AWS Access Key ID for S3 access'
+    required: true
+  aws-secret-access-key:
+    description: 'AWS Secret Access Key for S3 access'
+    required: true
+
+outputs:
+  cache-hit:
+    description: 'A boolean value to indicate an exact match was found for the primary key'
+    value: ${{ steps.restore-cache.outputs.cache-hit }}
+  cache-primary-key:
+    description: 'The key that was used to restore the cache (may be from restore-keys)'
+    value: ${{ steps.restore-cache.outputs.cache-primary-key }}
+  cache-matched-key:
+    description: 'The key that was used to restore the cache (exact or prefix match)'
+    value: ${{ steps.restore-cache.outputs.cache-matched-key }}
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Restore cache from S3
+      id: restore-cache
+      shell: bash
+      env:
+        AWS_ACCESS_KEY_ID: ${{ inputs.aws-access-key-id }}
+        AWS_SECRET_ACCESS_KEY: ${{ inputs.aws-secret-access-key }}
+        S3_BUCKET: ${{ inputs.s3-bucket }}
+        S3_REGION: ${{ inputs.s3-region }}
+        CACHE_KEY: ${{ inputs.key }}
+        RESTORE_KEYS: ${{ inputs.restore-keys }}
+        TARGET_PATH: ${{ inputs.path }}
+        FAIL_ON_MISS: ${{ inputs.fail-on-cache-miss }}
+        LOOKUP_ONLY: ${{ inputs.lookup-only }}
+      run: |
+        set -euo pipefail
+
+        echo "=========================================="
+        echo "Xahau Cache Restore (S3)"
+        echo "=========================================="
+        echo "Target path: ${TARGET_PATH}"
+        echo "Cache key: ${CACHE_KEY}"
+        echo "S3 bucket: s3://${S3_BUCKET}"
+        echo ""
+
+        # Normalize target path (expand tilde)
+        if [[ "${TARGET_PATH}" == ~* ]]; then
+          TARGET_PATH="${HOME}${TARGET_PATH:1}"
+        fi
+
+        # Canonicalize path (Linux only - macOS realpath doesn't support -m)
+        if [[ "$OSTYPE" == "linux-gnu"* ]]; then
+          TARGET_PATH=$(realpath -m "${TARGET_PATH}")
+        fi
+
+        echo "Normalized target path: ${TARGET_PATH}"
+        echo ""
+
+        # Debug: Show commit message
+        echo "=========================================="
+        echo "DEBUG: Cache clear tag detection"
+        echo "=========================================="
+        echo "Raw commit message:"
+        echo "${XAHAU_GA_COMMIT_MSG}"
+        echo ""
+        echo "Searching for: [ci-ga-clear-cache] or [ci-ga-clear-cache:*]"
+        echo ""
+
+        # Check for [ci-ga-clear-cache] tag in commit message (with optional search terms)
+        # Examples:
+        #   [ci-ga-clear-cache]              - Clear this job's cache
+        #   [ci-ga-clear-cache:ccache]       - Clear only if key contains "ccache"
+        #   [ci-ga-clear-cache:gcc Debug]    - Clear only if key contains both "gcc" AND "Debug"
+
+        # Extract search terms if present (e.g., "ccache" from "[ci-ga-clear-cache:ccache]")
+        SEARCH_TERMS=$(echo "${XAHAU_GA_COMMIT_MSG}" | grep -o '\[ci-ga-clear-cache:[^]]*\]' | sed 's/\[ci-ga-clear-cache://;s/\]//' || echo "")
+
+        SHOULD_CLEAR=false
+
+        if [ -n "${SEARCH_TERMS}" ]; then
+          # Search terms provided - check if THIS cache key matches ALL terms (AND logic)
+          echo "🔍 [ci-ga-clear-cache:${SEARCH_TERMS}] detected"
+          echo "Checking if cache key matches search terms..."
+          echo "  Cache key: ${CACHE_KEY}"
+          echo "  Search terms: ${SEARCH_TERMS}"
+          echo ""
+
+          MATCHES=true
+          for term in ${SEARCH_TERMS}; do
+            if ! echo "${CACHE_KEY}" | grep -q "${term}"; then
+              MATCHES=false
+              echo "  ✗ Key does not contain '${term}'"
+              break
+            else
+              echo "  ✓ Key contains '${term}'"
+            fi
+          done
+
+          if [ "${MATCHES}" = "true" ]; then
+            echo ""
+            echo "✅ Cache key matches all search terms - will clear cache"
+            SHOULD_CLEAR=true
+          else
+            echo ""
+            echo "⏭️  Cache key doesn't match search terms - skipping cache clear"
+          fi
+        elif echo "${XAHAU_GA_COMMIT_MSG}" | grep -q '\[ci-ga-clear-cache\]'; then
+          # No search terms - always clear this job's cache
+          echo "🗑️  [ci-ga-clear-cache] detected in commit message"
+          echo "Clearing cache for key: ${CACHE_KEY}"
+          SHOULD_CLEAR=true
+        fi
+
+        if [ "${SHOULD_CLEAR}" = "true" ]; then
+          echo ""
+
+          # Delete base layer
+          S3_BASE_KEY="s3://${S3_BUCKET}/${CACHE_KEY}-base.tar.zst"
+          if aws s3 ls "${S3_BASE_KEY}" --region "${S3_REGION}" >/dev/null 2>&1; then
+            echo "Deleting base layer: ${S3_BASE_KEY}"
+            aws s3 rm "${S3_BASE_KEY}" --region "${S3_REGION}" 2>/dev/null || true
+            echo "✓ Base layer deleted"
+          else
+            echo "ℹ️  No base layer found to delete"
+          fi
+
+          echo ""
+          echo "✅ Cache cleared successfully"
+          echo "Build will proceed from scratch (bootstrap mode)"
+          echo ""
+        fi
+
+        # Function to try restoring a cache key
+        try_restore_key() {
+          local key=$1
+          local s3_key="s3://${S3_BUCKET}/${key}-base.tar.zst"
+
+          echo "Checking for key: ${key}"
+
+          if aws s3 ls "${s3_key}" --region "${S3_REGION}" >/dev/null 2>&1; then
+            echo "✓ Found cache: ${s3_key}"
+            return 0
+          else
+            echo "✗ Not found: ${key}"
+            return 1
+          fi
+        }
+
+        # Try exact match first
+        MATCHED_KEY=""
+        EXACT_MATCH="false"
+
+        if try_restore_key "${CACHE_KEY}"; then
+          MATCHED_KEY="${CACHE_KEY}"
+          EXACT_MATCH="true"
+          echo ""
+          echo "🎯 Exact cache hit for key: ${CACHE_KEY}"
+        else
+          # Try restore-keys (prefix matching)
+          if [ -n "${RESTORE_KEYS}" ]; then
+            echo ""
+            echo "Primary key not found, trying restore-keys..."
+
+            while IFS= read -r restore_key; do
+              [ -z "${restore_key}" ] && continue
+              restore_key=$(echo "${restore_key}" | xargs)
+
+              if try_restore_key "${restore_key}"; then
+                MATCHED_KEY="${restore_key}"
+                EXACT_MATCH="false"
+                echo ""
+                echo "✓ Cache restored from fallback key: ${restore_key}"
+                break
+              fi
+            done <<< "${RESTORE_KEYS}"
+          fi
+        fi
+
+        # Check if we found anything
+        if [ -z "${MATCHED_KEY}" ]; then
+          echo ""
+          echo "❌ No cache found for key: ${CACHE_KEY}"
+
+          if [ "${FAIL_ON_MISS}" = "true" ]; then
+            echo "fail-on-cache-miss is enabled, failing workflow"
+            exit 1
+          fi
+
+          # Set outputs for cache miss
+          echo "cache-hit=false" >> $GITHUB_OUTPUT
+          echo "cache-primary-key=" >> $GITHUB_OUTPUT
+          echo "cache-matched-key=" >> $GITHUB_OUTPUT
+
+          # Create empty cache directory
+          mkdir -p "${TARGET_PATH}"
+
+          echo ""
+          echo "=========================================="
+          echo "Cache restore completed (bootstrap mode)"
+          echo "Created empty cache directory: ${TARGET_PATH}"
+          echo "=========================================="
+          exit 0
+        fi
+
+        # If lookup-only, we're done
+        if [ "${LOOKUP_ONLY}" = "true" ]; then
+          echo "cache-hit=${EXACT_MATCH}" >> $GITHUB_OUTPUT
+          echo "cache-primary-key=${CACHE_KEY}" >> $GITHUB_OUTPUT
+          echo "cache-matched-key=${MATCHED_KEY}" >> $GITHUB_OUTPUT
+
+          echo ""
+          echo "=========================================="
+          echo "Cache lookup completed (lookup-only mode)"
+          echo "Cache exists: ${MATCHED_KEY}"
+          echo "=========================================="
+          exit 0
+        fi
+
+        # Download and extract cache
+        S3_KEY="s3://${S3_BUCKET}/${MATCHED_KEY}-base.tar.zst"
+        TEMP_TARBALL="/tmp/xahau-cache-restore-$$.tar.zst"
+
+        echo ""
+        echo "Downloading cache..."
+        aws s3 cp "${S3_KEY}" "${TEMP_TARBALL}" --region "${S3_REGION}" --no-progress
+
+        TARBALL_SIZE=$(du -h "${TEMP_TARBALL}" | cut -f1)
+        echo "✓ Downloaded: ${TARBALL_SIZE}"
+
+        # Create parent directory if needed
+        mkdir -p "$(dirname "${TARGET_PATH}")"
+
+        # Remove existing target if it exists
+        if [ -e "${TARGET_PATH}" ]; then
+          echo "Removing existing target: ${TARGET_PATH}"
+          rm -rf "${TARGET_PATH}"
+        fi
+
+        # Create target directory and extract
+        mkdir -p "${TARGET_PATH}"
+        echo ""
+        echo "Extracting cache..."
+        zstd -d -c "${TEMP_TARBALL}" | tar -xf - -C "${TARGET_PATH}"
+        echo "✓ Cache extracted to: ${TARGET_PATH}"
+
+        # Cleanup
+        rm -f "${TEMP_TARBALL}"
+
+        # Set outputs
+        echo "cache-hit=${EXACT_MATCH}" >> $GITHUB_OUTPUT
+        echo "cache-primary-key=${CACHE_KEY}" >> $GITHUB_OUTPUT
+        echo "cache-matched-key=${MATCHED_KEY}" >> $GITHUB_OUTPUT
+
+        echo ""
+        echo "=========================================="
+        echo "Cache restore completed successfully"
+        echo "Cache hit: ${EXACT_MATCH}"
+        echo "Matched key: ${MATCHED_KEY}"
+        echo "=========================================="

.github/actions/xahau-ga-cache-save/action.yml

@@ -0,0 +1,110 @@
+name: 'Xahau Cache Save (S3)'
+description: 'Drop-in replacement for actions/cache/save using S3 storage'
+
+inputs:
+  path:
+    description: 'A list of files, directories, and wildcard patterns to cache (currently only single path supported)'
+    required: true
+  key:
+    description: 'An explicit key for saving the cache'
+    required: true
+  s3-bucket:
+    description: 'S3 bucket name for cache storage'
+    required: false
+    default: 'xahaud-github-actions-cache-niq'
+  s3-region:
+    description: 'S3 region'
+    required: false
+    default: 'us-east-1'
+  # Note: Composite actions can't access secrets.* directly - must be passed from workflow
+  aws-access-key-id:
+    description: 'AWS Access Key ID for S3 access'
+    required: true
+  aws-secret-access-key:
+    description: 'AWS Secret Access Key for S3 access'
+    required: true
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Save cache to S3
+      shell: bash
+      env:
+        AWS_ACCESS_KEY_ID: ${{ inputs.aws-access-key-id }}
+        AWS_SECRET_ACCESS_KEY: ${{ inputs.aws-secret-access-key }}
+        S3_BUCKET: ${{ inputs.s3-bucket }}
+        S3_REGION: ${{ inputs.s3-region }}
+        CACHE_KEY: ${{ inputs.key }}
+        TARGET_PATH: ${{ inputs.path }}
+      run: |
+        set -euo pipefail
+
+        echo "=========================================="
+        echo "Xahau Cache Save (S3)"
+        echo "=========================================="
+        echo "Target path: ${TARGET_PATH}"
+        echo "Cache key: ${CACHE_KEY}"
+        echo "S3 bucket: s3://${S3_BUCKET}"
+        echo ""
+
+        # Normalize target path (expand tilde and resolve to absolute path)
+        if [[ "${TARGET_PATH}" == ~* ]]; then
+          TARGET_PATH="${HOME}${TARGET_PATH:1}"
+        fi
+        echo "Normalized target path: ${TARGET_PATH}"
+        echo ""
+
+        # Check if target directory exists
+        if [ ! -d "${TARGET_PATH}" ]; then
+          echo "⚠️  Target directory does not exist: ${TARGET_PATH}"
+          echo "Skipping cache save."
+          exit 0
+        fi
+
+        # Use static base name (one base per key, immutable)
+        S3_BASE_KEY="s3://${S3_BUCKET}/${CACHE_KEY}-base.tar.zst"
+
+        # Check if base already exists (immutability - first write wins)
+        if aws s3 ls "${S3_BASE_KEY}" --region "${S3_REGION}" >/dev/null 2>&1; then
+          echo "⚠️  Cache already exists: ${S3_BASE_KEY}"
+          echo "Skipping upload (immutability - first write wins, like GitHub Actions)"
+          echo ""
+          echo "=========================================="
+          echo "Cache save completed (already exists)"
+          echo "=========================================="
+          exit 0
+        fi
+
+        # Create tarball
+        BASE_TARBALL="/tmp/xahau-cache-base-$$.tar.zst"
+
+        echo "Creating cache tarball..."
+        tar -cf - -C "${TARGET_PATH}" . | zstd -3 -T0 -q -o "${BASE_TARBALL}"
+
+        BASE_SIZE=$(du -h "${BASE_TARBALL}" | cut -f1)
+        echo "✓ Cache tarball created: ${BASE_SIZE}"
+        echo ""
+
+        # Upload to S3
+        echo "Uploading cache to S3..."
+        echo "  Key: ${CACHE_KEY}-base.tar.zst"
+
+        aws s3api put-object \
+          --bucket "${S3_BUCKET}" \
+          --key "${CACHE_KEY}-base.tar.zst" \
+          --body "${BASE_TARBALL}" \
+          --tagging 'type=base' \
+          --region "${S3_REGION}" \
+          >/dev/null 2>&1
+
+        echo "✓ Uploaded: ${S3_BASE_KEY}"
+
+        # Cleanup
+        rm -f "${BASE_TARBALL}"
+
+        echo ""
+        echo "=========================================="
+        echo "Cache save completed successfully"
+        echo "Cache size: ${BASE_SIZE}"
+        echo "Cache key: ${CACHE_KEY}"
+        echo "=========================================="

.github/actions/xahau-ga-dependencies/action.yml

@@ -25,6 +25,28 @@ inputs:
     description: 'Main branch name for restore keys'
     required: false
     default: 'dev'
+  os:
+    description: 'Operating system (Linux, Macos)'
+    required: false
+    default: 'Linux'
+  arch:
+    description: 'Architecture (x86_64, armv8)'
+    required: false
+    default: 'x86_64'
+  compiler:
+    description: 'Compiler type (gcc, clang, apple-clang)'
+    required: true
+  compiler_version:
+    description: 'Compiler version (11, 13, 14, etc.)'
+    required: true
+  cc:
+    description: 'C compiler executable (gcc-13, clang-14, etc.), empty for macOS'
+    required: false
+    default: ''
+  cxx:
+    description: 'C++ compiler executable (g++-14, clang++-14, etc.), empty for macOS'
+    required: false
+    default: ''
   stdlib:
     description: 'C++ standard library for Conan configuration (note: also in compiler-id)'
     required: true
@@ -32,6 +54,12 @@ inputs:
     options:
       - libstdcxx
       - libcxx
+  aws-access-key-id:
+    description: 'AWS Access Key ID for S3 cache storage'
+    required: true
+  aws-secret-access-key:
+    description: 'AWS Secret Access Key for S3 cache storage'
+    required: true
 
 outputs:
   cache-hit:
@@ -41,47 +69,72 @@ outputs:
 runs:
   using: 'composite'
   steps:
-    - name: Generate safe branch name
-      if: inputs.cache_enabled == 'true'
-      id: safe-branch
-      shell: bash
-      run: |
-        SAFE_BRANCH=$(echo "${{ github.ref_name }}" | tr -c 'a-zA-Z0-9_.-' '-')
-        echo "name=${SAFE_BRANCH}" >> $GITHUB_OUTPUT
-
-    - name: Check conanfile changes
-      if: inputs.cache_enabled == 'true'
-      id: check-conanfile-changes
-      shell: bash
-      run: |
-        # Check if we're on the main branch
-        if [ "${{ github.ref_name }}" == "${{ inputs.main_branch }}" ]; then
-          echo "should-save-conan-cache=true" >> $GITHUB_OUTPUT
-        else
-          # Fetch main branch for comparison
-          git fetch origin ${{ inputs.main_branch }}
-          
-          # Check if conanfile.txt or conanfile.py has changed compared to main branch
-          if git diff --quiet origin/${{ inputs.main_branch }}..HEAD -- '**/conanfile.txt' '**/conanfile.py'; then
-            echo "should-save-conan-cache=false" >> $GITHUB_OUTPUT
-          else
-            echo "should-save-conan-cache=true" >> $GITHUB_OUTPUT
-          fi
-        fi
 
     - name: Restore Conan cache
       if: inputs.cache_enabled == 'true'
       id: cache-restore-conan
-      uses: actions/cache/restore@v4
+      uses: ./.github/actions/xahau-ga-cache-restore
       with:
-        path: |
-          ~/.conan
-          ~/.conan2
+        path: ~/.conan2
         # Note: compiler-id format is compiler-version-stdlib[-gccversion]
         key: ${{ runner.os }}-conan-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ hashFiles('**/conanfile.txt', '**/conanfile.py') }}-${{ inputs.configuration }}
         restore-keys: |
           ${{ runner.os }}-conan-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ hashFiles('**/conanfile.txt', '**/conanfile.py') }}-
           ${{ runner.os }}-conan-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-
+        aws-access-key-id: ${{ inputs.aws-access-key-id }}
+        aws-secret-access-key: ${{ inputs.aws-secret-access-key }}
+
+    - name: Configure Conan
+      shell: bash
+      run: |
+        # Create the default profile directory if it doesn't exist
+        mkdir -p ~/.conan2/profiles
+
+        # Determine the correct libcxx based on stdlib parameter
+        if [ "${{ inputs.stdlib }}" = "libcxx" ]; then
+          LIBCXX="libc++"
+        else
+          LIBCXX="libstdc++11"
+        fi
+
+        # Create profile with our specific settings
+        # This overwrites any cached profile to ensure fresh configuration
+        cat > ~/.conan2/profiles/default <<EOF
+        [settings]
+        arch=${{ inputs.arch }}
+        build_type=${{ inputs.configuration }}
+        compiler=${{ inputs.compiler }}
+        compiler.cppstd=20
+        compiler.libcxx=${LIBCXX}
+        compiler.version=${{ inputs.compiler_version }}
+        os=${{ inputs.os }}
+        EOF
+
+        # Add buildenv and conf sections for Linux (not needed for macOS)
+        if [ "${{ inputs.os }}" = "Linux" ] && [ -n "${{ inputs.cc }}" ]; then
+          cat >> ~/.conan2/profiles/default <<EOF
+
+        [buildenv]
+        CC=/usr/bin/${{ inputs.cc }}
+        CXX=/usr/bin/${{ inputs.cxx }}
+
+        [conf]
+        tools.build:compiler_executables={"c": "/usr/bin/${{ inputs.cc }}", "cpp": "/usr/bin/${{ inputs.cxx }}"}
+        EOF
+        fi
+
+        # Add macOS-specific conf if needed
+        if [ "${{ inputs.os }}" = "Macos" ]; then
+          cat >> ~/.conan2/profiles/default <<EOF
+
+        [conf]
+        # Workaround for gRPC with newer Apple Clang
+        tools.build:cxxflags=["-Wno-missing-template-arg-list-after-template-kw"]
+        EOF
+        fi
+
+        # Display profile for verification
+        conan profile show
 
     - name: Export custom recipes
       shell: bash
@@ -107,10 +160,10 @@ runs:
           ..
 
     - name: Save Conan cache
-      if: always() && inputs.cache_enabled == 'true' && steps.cache-restore-conan.outputs.cache-hit != 'true' && steps.check-conanfile-changes.outputs.should-save-conan-cache == 'true'
-      uses: actions/cache/save@v4
+      if: success() && inputs.cache_enabled == 'true' && steps.cache-restore-conan.outputs.cache-hit != 'true'
+      uses: ./.github/actions/xahau-ga-cache-save
       with:
-        path: |
-          ~/.conan
-          ~/.conan2
-        key: ${{ steps.cache-restore-conan.outputs.cache-primary-key }}
+        path: ~/.conan2
+        key: ${{ runner.os }}-conan-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ hashFiles('**/conanfile.txt', '**/conanfile.py') }}-${{ inputs.configuration }}
+        aws-access-key-id: ${{ inputs.aws-access-key-id }}
+        aws-secret-access-key: ${{ inputs.aws-secret-access-key }}

.github/actions/xahau-ga-get-commit-message/action.yml

@@ -0,0 +1,73 @@
+name: 'Get Commit Message'
+description: 'Gets commit message for both push and pull_request events and sets XAHAU_GA_COMMIT_MSG env var'
+
+inputs:
+  event-name:
+    description: 'The event name (push or pull_request)'
+    required: true
+  head-commit-message:
+    description: 'The head commit message (for push events)'
+    required: false
+    default: ''
+  pr-head-sha:
+    description: 'The PR head SHA (for pull_request events)'
+    required: false
+    default: ''
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Get commit message and set environment variable
+      shell: python
+      run: |
+        import os
+        import subprocess
+        import secrets
+
+        event_name = "${{ inputs.event-name }}"
+        pr_head_sha = "${{ inputs.pr-head-sha }}"
+
+        print("==========================================")
+        print("Setting XAHAU_GA_COMMIT_MSG environment variable")
+        print("==========================================")
+        print(f"Event: {event_name}")
+
+        if event_name == 'push':
+            # For push events, use the input directly
+            message = """${{ inputs.head-commit-message }}"""
+            print("Source: workflow input (github.event.head_commit.message)")
+        elif event_name == 'pull_request':
+            # For PR events, fetch the specific SHA
+            print(f"Source: git show {pr_head_sha} (fetching PR head commit)")
+
+            # Fetch the PR head commit
+            subprocess.run(
+                ['git', 'fetch', 'origin', pr_head_sha],
+                check=True
+            )
+
+            # Get commit message from the fetched SHA
+            result = subprocess.run(
+                ['git', 'show', '-s', '--format=%B', pr_head_sha],
+                capture_output=True,
+                text=True,
+                check=True
+            )
+            message = result.stdout.strip()
+        else:
+            message = ""
+            print(f"Warning: Unknown event type: {event_name}")
+
+        print(f"Commit message (first 100 chars): {message[:100]}")
+
+        # Write to GITHUB_ENV using heredoc with random delimiter (prevents injection attacks)
+        # See: https://securitylab.github.com/resources/github-actions-untrusted-input/
+        delimiter = f"EOF_{secrets.token_hex(16)}"
+
+        with open(os.environ['GITHUB_ENV'], 'a') as f:
+            f.write(f'XAHAU_GA_COMMIT_MSG<<{delimiter}\n')
+            f.write(message)
+            f.write(f'\n{delimiter}\n')
+
+        print(f"✓ XAHAU_GA_COMMIT_MSG set (available to all subsequent steps)")
+        print("==========================================")

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

@@ -30,6 +30,14 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
+      - name: Get commit message
+        id: get-commit-message
+        uses: ./.github/actions/xahau-ga-get-commit-message
+        with:
+          event-name: ${{ github.event_name }}
+          head-commit-message: ${{ github.event.head_commit.message }}
+          pr-head-sha: ${{ github.event.pull_request.head.sha }}
+
       - name: Install Conan
         run: |
           brew install conan
@@ -78,14 +86,6 @@ jobs:
       - 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:"
@@ -98,32 +98,12 @@ jobs:
           echo "---- Full Environment ----"
           env
 
-      - name: Configure Conan
+      - name: Detect compiler version
+        id: detect-compiler
         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
+          echo "compiler_version=${COMPILER_VERSION}" >> $GITHUB_OUTPUT
+          echo "Detected Apple Clang version: ${COMPILER_VERSION}"
 
       - name: Install dependencies
         uses: ./.github/actions/xahau-ga-dependencies
@@ -133,6 +113,13 @@ jobs:
           compiler-id: clang
           cache_version: ${{ env.CACHE_VERSION }}
           main_branch: ${{ env.MAIN_BRANCH_NAME }}
+          os: Macos
+          arch: armv8
+          compiler: apple-clang
+          compiler_version: ${{ steps.detect-compiler.outputs.compiler_version }}
+          stdlib: libcxx
+          aws-access-key-id: ${{ secrets.XAHAUD_GITHUB_ACTIONS_CACHE_NIQ_AWS_KEY_ID }}
+          aws-secret-access-key: ${{ secrets.XAHAUD_GITHUB_ACTIONS_CACHE_NIQ_AWS_ACCESS_KEY }}
 
       - name: Build
         uses: ./.github/actions/xahau-ga-build
@@ -143,6 +130,9 @@ jobs:
           compiler-id: clang
           cache_version: ${{ env.CACHE_VERSION }}
           main_branch: ${{ env.MAIN_BRANCH_NAME }}
+          stdlib: libcxx
+          aws-access-key-id: ${{ secrets.XAHAUD_GITHUB_ACTIONS_CACHE_NIQ_AWS_KEY_ID }}
+          aws-secret-access-key: ${{ secrets.XAHAUD_GITHUB_ACTIONS_CACHE_NIQ_AWS_ACCESS_KEY }}
 
       - name: Test
         run: |

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

@@ -2,7 +2,7 @@ name: Nix - GA Runner
 
 on:
   push:
-    branches: ["dev", "candidate", "release"]
+    branches: ["dev", "candidate", "release", "nd-experiment-overlayfs-2025-10-29"]
   pull_request:
     branches: ["dev", "candidate", "release"]
   schedule:
@@ -156,12 +156,20 @@ jobs:
     env:
       build_dir: .build
       # Bump this number to invalidate all caches globally.
-      CACHE_VERSION: 2
+      CACHE_VERSION: 3
       MAIN_BRANCH_NAME: dev
     steps:
       - name: Checkout
         uses: actions/checkout@v4
 
+      - name: Get commit message
+        id: get-commit-message
+        uses: ./.github/actions/xahau-ga-get-commit-message
+        with:
+          event-name: ${{ github.event_name }}
+          head-commit-message: ${{ github.event.head_commit.message }}
+          pr-head-sha: ${{ github.event.pull_request.head.sha }}
+
       - name: Install build dependencies
         run: |
           sudo apt-get update
@@ -231,48 +239,6 @@ jobs:
           # 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:"
@@ -293,7 +259,13 @@ jobs:
           compiler-id: ${{ matrix.compiler_id }}
           cache_version: ${{ env.CACHE_VERSION }}
           main_branch: ${{ env.MAIN_BRANCH_NAME }}
+          compiler: ${{ matrix.compiler }}
+          compiler_version: ${{ matrix.compiler_version }}
+          cc: ${{ matrix.cc }}
+          cxx: ${{ matrix.cxx }}
           stdlib: ${{ matrix.stdlib }}
+          aws-access-key-id: ${{ secrets.XAHAUD_GITHUB_ACTIONS_CACHE_NIQ_AWS_KEY_ID }}
+          aws-secret-access-key: ${{ secrets.XAHAUD_GITHUB_ACTIONS_CACHE_NIQ_AWS_ACCESS_KEY }}
 
       - name: Build
         uses: ./.github/actions/xahau-ga-build
@@ -308,6 +280,8 @@ jobs:
           main_branch: ${{ env.MAIN_BRANCH_NAME }}
           stdlib: ${{ matrix.stdlib }}
           clang_gcc_toolchain: ${{ matrix.clang_gcc_toolchain || '' }}
+          aws-access-key-id: ${{ secrets.XAHAUD_GITHUB_ACTIONS_CACHE_NIQ_AWS_KEY_ID }}
+          aws-secret-access-key: ${{ secrets.XAHAUD_GITHUB_ACTIONS_CACHE_NIQ_AWS_ACCESS_KEY }}
 
       - name: Set artifact name
         id: set-artifact-name