fix: restore ninja -v flag for compile command visibility

Removed in b24e4647b under naive assumption we were "past debugging phase".

Reality: debugging is never done, verbose output is invaluable, costs nothing.
Keep -v flag permanently.

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

@@ -1,5 +1,5 @@
-name: 'Xahau Cache Restore (S3 + OverlayFS)'
-description: 'Drop-in replacement for actions/cache/restore using S3 and OverlayFS for delta caching'
+name: 'Xahau Cache Restore (S3)'
+description: 'Drop-in replacement for actions/cache/restore using S3 storage'
 
 inputs:
   path:
@@ -28,10 +28,6 @@ inputs:
     description: 'Check if a cache entry exists for the given input(s) without downloading it'
     required: false
     default: 'false'
-  use-deltas:
-    description: 'Enable delta caching (download/upload incremental changes). Set to false for base-only caching.'
-    required: false
-    default: 'true'
   # 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'
@@ -48,13 +44,13 @@ outputs:
     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 matched (same as cache-primary-key for compatibility)'
-    value: ${{ steps.restore-cache.outputs.cache-primary-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 with OverlayFS
+    - name: Restore cache from S3
       id: restore-cache
       shell: bash
       env:
@@ -67,133 +63,42 @@ runs:
         TARGET_PATH: ${{ inputs.path }}
         FAIL_ON_MISS: ${{ inputs.fail-on-cache-miss }}
         LOOKUP_ONLY: ${{ inputs.lookup-only }}
-        USE_DELTAS: ${{ inputs.use-deltas }}
-        COMMIT_MSG: ${{ github.event.head_commit.message }}
       run: |
         set -euo pipefail
 
         echo "=========================================="
-        echo "Xahau Cache Restore (S3 + OverlayFS)"
+        echo "Xahau Cache Restore (S3)"
         echo "=========================================="
         echo "Target path: ${TARGET_PATH}"
-        echo "Primary key: ${CACHE_KEY}"
+        echo "Cache key: ${CACHE_KEY}"
         echo "S3 bucket: s3://${S3_BUCKET}"
-        echo "Use deltas: ${USE_DELTAS}"
         echo ""
 
         # Normalize target path (expand tilde and resolve to absolute path)
-        # This ensures consistent path comparison in the mount registry
         if [[ "${TARGET_PATH}" == ~* ]]; then
-          # Expand tilde manually (works even if directory doesn't exist yet)
           TARGET_PATH="${HOME}${TARGET_PATH:1}"
         fi
+        TARGET_PATH=$(realpath -m "${TARGET_PATH}")
         echo "Normalized target path: ${TARGET_PATH}"
+        echo ""
 
-        # Generate unique cache workspace
-        CACHE_HASH=$(echo "${CACHE_KEY}" | md5sum | cut -d' ' -f1)
-        CACHE_WORKSPACE="/tmp/xahau-cache-${CACHE_HASH}"
-
-        echo "Cache workspace: ${CACHE_WORKSPACE}"
-
-        # Check for [ci-clear-cache] tag in commit message
-        if echo "${COMMIT_MSG}" | grep -q '\[ci-clear-cache\]'; then
-          echo ""
-          echo "🗑️  [ci-clear-cache] detected in commit message"
-          echo "Clearing cache for key: ${CACHE_KEY}"
-          echo ""
-
-          # Delete base layer
-          S3_BASE_KEY="s3://${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
-
-          # Delete all delta layers for this key
-          echo "Deleting all delta layers matching: ${CACHE_KEY}-delta-*"
-          DELTA_COUNT=$(aws s3 ls "s3://${S3_BUCKET}/" --region "${S3_REGION}" | grep "${CACHE_KEY}-delta-" | wc -l || echo "0")
-          DELTA_COUNT=$(echo "${DELTA_COUNT}" | tr -d ' \n')  # Trim whitespace
-          if [ "${DELTA_COUNT}" -gt 0 ]; then
-            aws s3 rm "s3://${S3_BUCKET}/" --recursive \
-              --exclude "*" \
-              --include "${CACHE_KEY}-delta-*" \
-              --region "${S3_REGION}" 2>/dev/null || true
-            echo "✓ Deleted ${DELTA_COUNT} delta layer(s)"
-          else
-            echo "ℹ️  No delta layers found to delete"
-          fi
-
-          echo ""
-          echo "✅ Cache cleared successfully"
-          echo "Build will proceed from scratch (bootstrap mode)"
-          echo ""
-        fi
-
-        # Create OverlayFS directory structure
-        mkdir -p "${CACHE_WORKSPACE}"/{base,upper,work,merged}
-
-        # Function to try downloading from S3
+        # Function to try restoring a cache key
         try_restore_key() {
-          local try_key="$1"
-          local s3_base="s3://${S3_BUCKET}/${try_key}-base.tar.zst"
+          local key=$1
+          local s3_key="s3://${S3_BUCKET}/${key}-base.tar.zst"
 
-          echo "Trying cache key: ${try_key}"
-
-          # Check if base exists (one base per key, immutable)
-          echo "Checking for base layer..."
-          if aws s3 ls "${s3_base}" --region "${S3_REGION}" >/dev/null 2>&1; then
-            echo "✓ Found base layer: ${s3_base}"
-
-            if [ "${LOOKUP_ONLY}" = "true" ]; then
-              echo "Lookup-only mode: cache exists, skipping download"
-              return 0
-            fi
-
-            # Download base layer
-            echo "Downloading base layer..."
-            aws s3 cp "${s3_base}" /tmp/cache-base.tar.zst --region "${S3_REGION}" --quiet
-
-            # Extract base layer
-            echo "Extracting base layer..."
-            tar -xf /tmp/cache-base.tar.zst -C "${CACHE_WORKSPACE}/base"
-            rm /tmp/cache-base.tar.zst
-
-            # Query for latest timestamped delta (only if use-deltas enabled)
-            if [ "${USE_DELTAS}" = "true" ]; then
-              echo "Querying for latest delta..."
-              LATEST_DELTA=$(aws s3api list-objects-v2 \
-                --bucket "${S3_BUCKET}" \
-                --prefix "${try_key}-delta-" \
-                --region "${S3_REGION}" \
-                --query 'sort_by(Contents, &LastModified)[-1].Key' \
-                --output text 2>/dev/null || echo "")
-
-              if [ -n "${LATEST_DELTA}" ] && [ "${LATEST_DELTA}" != "None" ]; then
-                echo "✓ Found latest delta: ${LATEST_DELTA}"
-                echo "Downloading delta layer..."
-                aws s3 cp "s3://${S3_BUCKET}/${LATEST_DELTA}" /tmp/cache-delta.tar.zst --region "${S3_REGION}" --quiet
-
-                echo "Extracting delta layer..."
-                tar -xf /tmp/cache-delta.tar.zst -C "${CACHE_WORKSPACE}/upper" 2>/dev/null || true
-                rm /tmp/cache-delta.tar.zst
-              else
-                echo "ℹ No delta layer found (this is fine for first build)"
-              fi
-            else
-              echo "ℹ Delta caching disabled (use-deltas: false)"
-            fi
+          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 "✗ No base layer found for key: ${try_key}"
+            echo "✗ Not found: ${key}"
             return 1
           fi
         }
 
-        # Try primary key first
+        # Try exact match first
         MATCHED_KEY=""
         EXACT_MATCH="false"
 
@@ -208,12 +113,8 @@ runs:
             echo ""
             echo "Primary key not found, trying restore-keys..."
 
-            # Split restore-keys by newline
             while IFS= read -r restore_key; do
-              # Skip empty lines
               [ -z "${restore_key}" ] && continue
-
-              # Trim whitespace
               restore_key=$(echo "${restore_key}" | xargs)
 
               if try_restore_key "${restore_key}"; then
@@ -231,7 +132,6 @@ runs:
         if [ -z "${MATCHED_KEY}" ]; then
           echo ""
           echo "❌ No cache found for key: ${CACHE_KEY}"
-          echo "This is BOOTSTRAP mode - first build for this cache key"
 
           if [ "${FAIL_ON_MISS}" = "true" ]; then
             echo "fail-on-cache-miss is enabled, failing workflow"
@@ -241,16 +141,11 @@ runs:
           # 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 for bootstrap
+          # Create empty cache directory
           mkdir -p "${TARGET_PATH}"
 
-          # Record bootstrap mode for save action
-          # Format: path:workspace:matched_key:primary_key:exact_match:use_deltas
-          # For bootstrap: workspace="bootstrap", matched_key=primary_key, exact_match=false
-          MOUNT_REGISTRY="/tmp/xahau-cache-mounts.txt"
-          echo "${TARGET_PATH}:bootstrap:${CACHE_KEY}:${CACHE_KEY}:false:${USE_DELTAS}" >> "${MOUNT_REGISTRY}"
-
           echo ""
           echo "=========================================="
           echo "Cache restore completed (bootstrap mode)"
@@ -262,36 +157,30 @@ runs:
         # If lookup-only, we're done
         if [ "${LOOKUP_ONLY}" = "true" ]; then
           echo "cache-hit=${EXACT_MATCH}" >> $GITHUB_OUTPUT
-          echo "cache-primary-key=${MATCHED_KEY}" >> $GITHUB_OUTPUT
-
-          # Clean up workspace
-          rm -rf "${CACHE_WORKSPACE}"
+          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
 
-        # Mount OverlayFS
+        # Download and extract cache
+        S3_KEY="s3://${S3_BUCKET}/${MATCHED_KEY}-base.tar.zst"
+        TEMP_TARBALL="/tmp/xahau-cache-restore-$$.tar.zst"
+
         echo ""
-        echo "Mounting OverlayFS..."
-        sudo mount -t overlay overlay \
-          -o lowerdir="${CACHE_WORKSPACE}/base",upperdir="${CACHE_WORKSPACE}/upper",workdir="${CACHE_WORKSPACE}/work" \
-          "${CACHE_WORKSPACE}/merged"
+        echo "Downloading cache..."
+        aws s3 cp "${S3_KEY}" "${TEMP_TARBALL}" --region "${S3_REGION}"
 
-        # Verify mount
-        if mount | grep -q "${CACHE_WORKSPACE}/merged"; then
-          echo "✓ OverlayFS mounted successfully"
-        else
-          echo "❌ Failed to mount OverlayFS"
-          exit 1
-        fi
+        TARBALL_SIZE=$(du -h "${TEMP_TARBALL}" | cut -f1)
+        echo "✓ Downloaded: ${TARBALL_SIZE}"
 
-        # Create target directory parent if needed
-        TARGET_PARENT=$(dirname "${TARGET_PATH}")
-        mkdir -p "${TARGET_PARENT}"
+        # Create parent directory if needed
+        mkdir -p "$(dirname "${TARGET_PATH}")"
 
         # Remove existing target if it exists
         if [ -e "${TARGET_PATH}" ]; then
@@ -299,30 +188,24 @@ runs:
           rm -rf "${TARGET_PATH}"
         fi
 
-        # Symlink target path to merged view
-        echo "Creating symlink: ${TARGET_PATH} -> ${CACHE_WORKSPACE}/merged"
-        ln -s "${CACHE_WORKSPACE}/merged" "${TARGET_PATH}"
+        # Create target directory and extract
+        mkdir -p "${TARGET_PATH}"
+        echo ""
+        echo "Extracting cache..."
+        zstd -d -c "${TEMP_TARBALL}" | tar -xf - -C "${TARGET_PATH}"
+        echo "✓ Cache extracted to: ${TARGET_PATH}"
 
-        # Save mount info for cleanup/save later
-        # Format: path:workspace:matched_key:primary_key:exact_match:use_deltas
-        # This tells save action whether to create new base (partial match) or just delta (exact match)
-        MOUNT_REGISTRY="/tmp/xahau-cache-mounts.txt"
-        echo "${TARGET_PATH}:${CACHE_WORKSPACE}:${MATCHED_KEY}:${CACHE_KEY}:${EXACT_MATCH}:${USE_DELTAS}" >> "${MOUNT_REGISTRY}"
+        # Cleanup
+        rm -f "${TEMP_TARBALL}"
 
         # Set outputs
         echo "cache-hit=${EXACT_MATCH}" >> $GITHUB_OUTPUT
-        echo "cache-primary-key=${MATCHED_KEY}" >> $GITHUB_OUTPUT
-
-        # Show statistics
-        echo ""
-        echo "Cache statistics:"
-        echo "  Base layer size:  $(du -sh ${CACHE_WORKSPACE}/base 2>/dev/null | cut -f1 || echo '0')"
-        echo "  Delta layer size: $(du -sh ${CACHE_WORKSPACE}/upper 2>/dev/null | cut -f1 || echo '0')"
-        echo "  Merged view size: $(du -sh ${CACHE_WORKSPACE}/merged 2>/dev/null | cut -f1 || echo '0')"
+        echo "cache-primary-key=${CACHE_KEY}" >> $GITHUB_OUTPUT
+        echo "cache-matched-key=${MATCHED_KEY}" >> $GITHUB_OUTPUT
 
         echo ""
         echo "=========================================="
         echo "Cache restore completed successfully"
-        echo "Exact match: ${EXACT_MATCH}"
+        echo "Cache hit: ${EXACT_MATCH}"
         echo "Matched key: ${MATCHED_KEY}"
         echo "=========================================="

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

@@ -1,5 +1,5 @@
-name: 'Xahau Cache Save (S3 + OverlayFS)'
-description: 'Drop-in replacement for actions/cache/save using S3 and OverlayFS for delta caching'
+name: 'Xahau Cache Save (S3)'
+description: 'Drop-in replacement for actions/cache/save using S3 storage'
 
 inputs:
   path:
@@ -16,10 +16,6 @@ inputs:
     description: 'S3 region'
     required: false
     default: 'us-east-1'
-  use-deltas:
-    description: 'Enable delta caching (download/upload incremental changes). Set to false for base-only caching.'
-    required: false
-    default: 'true'
   # 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'
@@ -31,7 +27,7 @@ inputs:
 runs:
   using: 'composite'
   steps:
-    - name: Save cache to S3 with OverlayFS delta
+    - name: Save cache to S3
       shell: bash
       env:
         AWS_ACCESS_KEY_ID: ${{ inputs.aws-access-key-id }}
@@ -40,12 +36,11 @@ runs:
         S3_REGION: ${{ inputs.s3-region }}
         CACHE_KEY: ${{ inputs.key }}
         TARGET_PATH: ${{ inputs.path }}
-        USE_DELTAS: ${{ inputs.use-deltas }}
       run: |
         set -euo pipefail
 
         echo "=========================================="
-        echo "Xahau Cache Save (S3 + OverlayFS)"
+        echo "Xahau Cache Save (S3)"
         echo "=========================================="
         echo "Target path: ${TARGET_PATH}"
         echo "Cache key: ${CACHE_KEY}"
@@ -53,346 +48,63 @@ runs:
         echo ""
 
         # Normalize target path (expand tilde and resolve to absolute path)
-        # This ensures consistent path comparison with the mount registry
         if [[ "${TARGET_PATH}" == ~* ]]; then
-          # Expand tilde manually (works even if directory doesn't exist yet)
           TARGET_PATH="${HOME}${TARGET_PATH:1}"
         fi
         echo "Normalized target path: ${TARGET_PATH}"
         echo ""
 
-        # Find the cache workspace from mount registry
-        MOUNT_REGISTRY="/tmp/xahau-cache-mounts.txt"
-
-        if [ ! -f "${MOUNT_REGISTRY}" ]; then
-          echo "⚠️  No cache mounts found (mount registry doesn't exist)"
-          echo "This usually means cache restore was not called, or there was no cache to restore."
+        # Check if target directory exists
+        if [ ! -d "${TARGET_PATH}" ]; then
+          echo "⚠️  Target directory does not exist: ${TARGET_PATH}"
           echo "Skipping cache save."
           exit 0
         fi
 
-        # Find entry for this path
-        # Format: path:workspace:matched_key:primary_key:exact_match:use_deltas
-        # Bootstrap mode: path:bootstrap:key:key:false:true/false (workspace="bootstrap")
-        CACHE_WORKSPACE=""
-        MATCHED_KEY=""
-        PRIMARY_KEY=""
-        EXACT_MATCH=""
-        REGISTRY_USE_DELTAS=""
+        # Use static base name (one base per key, immutable)
+        S3_BASE_KEY="s3://${S3_BUCKET}/${CACHE_KEY}-base.tar.zst"
 
-        while IFS=: read -r mount_path mount_workspace mount_matched_key mount_primary_key mount_exact_match mount_use_deltas; do
-          if [ "${mount_path}" = "${TARGET_PATH}" ]; then
-            CACHE_WORKSPACE="${mount_workspace}"
-            MATCHED_KEY="${mount_matched_key}"
-            PRIMARY_KEY="${mount_primary_key}"
-            EXACT_MATCH="${mount_exact_match}"
-            REGISTRY_USE_DELTAS="${mount_use_deltas}"
-            break
-          fi
-        done < "${MOUNT_REGISTRY}"
-
-        if [ -z "${CACHE_WORKSPACE}" ] && [ -z "${MATCHED_KEY}" ]; then
-          echo "⚠️  No cache entry found for path: ${TARGET_PATH}"
-          echo "This usually means cache restore was not called for this path."
-          echo "Skipping cache save."
+        # Check if base already exists (immutability - first write wins)
+        if aws s3 ls "${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
 
-        # Determine cache mode
-        if [ "${CACHE_WORKSPACE}" = "bootstrap" ]; then
-          CACHE_MODE="bootstrap"
-          PRIMARY_KEY="${MATCHED_KEY}"  # In bootstrap, matched_key field contains primary key
-          echo "Cache mode: BOOTSTRAP (first build for this key)"
-          echo "Primary key: ${PRIMARY_KEY}"
-        elif [ "${EXACT_MATCH}" = "false" ]; then
-          CACHE_MODE="partial-match"
-          echo "Cache mode: PARTIAL MATCH (restore-key used)"
-          echo "Cache workspace: ${CACHE_WORKSPACE}"
-          echo "Matched key from restore: ${MATCHED_KEY}"
-          echo "Primary key (will save new base): ${PRIMARY_KEY}"
-        else
-          CACHE_MODE="exact-match"
-          echo "Cache mode: EXACT MATCH (cache hit)"
-          echo "Cache workspace: ${CACHE_WORKSPACE}"
-          echo "Matched key: ${MATCHED_KEY}"
-        fi
-        echo "Use deltas: ${REGISTRY_USE_DELTAS}"
+        # 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 ""
 
-        # Handle different cache modes
-        if [ "${CACHE_MODE}" = "bootstrap" ]; then
-          # Bootstrap: Save entire cache as base layer (no OverlayFS was used)
-          echo "Bootstrap mode: Creating initial base layer from ${TARGET_PATH}"
+        # Upload to S3
+        echo "Uploading cache to S3..."
+        echo "  Key: ${CACHE_KEY}-base.tar.zst"
 
-          BASE_TARBALL="/tmp/xahau-cache-base-$$.tar.zst"
-          echo "Creating base tarball..."
-          tar -cf - -C "${TARGET_PATH}" . | zstd -3 -T0 -q -o "${BASE_TARBALL}"
+        aws s3api put-object \
+          --bucket "${S3_BUCKET}" \
+          --key "${CACHE_KEY}-base.tar.zst" \
+          --body "${BASE_TARBALL}" \
+          --tagging 'type=base' \
+          --region "${S3_REGION}" \
+          >/dev/null
 
-          BASE_SIZE=$(du -h "${BASE_TARBALL}" | cut -f1)
-          echo "✓ Base tarball created: ${BASE_SIZE}"
-          echo ""
+        echo "✓ Uploaded: ${S3_BASE_KEY}"
 
-          # Use static base name (one base per key, immutable)
-          S3_BASE_KEY="s3://${S3_BUCKET}/${PRIMARY_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 "⚠️  Base layer already exists: ${S3_BASE_KEY}"
-            echo "Skipping upload (immutability - first write wins, like GitHub Actions)"
-          else
-            echo "Uploading base layer to S3..."
-            echo "  Key: ${PRIMARY_KEY}-base.tar.zst"
-
-            aws s3api put-object \
-              --bucket "${S3_BUCKET}" \
-              --key "${PRIMARY_KEY}-base.tar.zst" \
-              --body "${BASE_TARBALL}" \
-              --tagging 'type=base' \
-              --region "${S3_REGION}" \
-              >/dev/null
-
-            echo "✓ Uploaded: ${S3_BASE_KEY}"
-          fi
-
-          # Cleanup
-          rm -f "${BASE_TARBALL}"
-
-          echo ""
-          echo "=========================================="
-          echo "Bootstrap cache save completed"
-          echo "Base size: ${BASE_SIZE}"
-          echo "Cache key: ${PRIMARY_KEY}"
-          echo "=========================================="
-          exit 0
-
-        elif [ "${CACHE_MODE}" = "partial-match" ]; then
-          # Partial match: Save merged view as new base ONLY (no delta)
-          # The delta is relative to the OLD base, not the NEW base we're creating
-          echo "Partial match mode: Saving new base layer for primary key"
-          echo "Note: Delta will NOT be saved (it's relative to old base)"
-
-          BASE_TARBALL="/tmp/xahau-cache-base-$$.tar.zst"
-          echo "Creating base tarball from merged view..."
-          tar -cf - -C "${CACHE_WORKSPACE}/merged" . | zstd -3 -T0 -q -o "${BASE_TARBALL}"
-
-          BASE_SIZE=$(du -h "${BASE_TARBALL}" | cut -f1)
-          echo "✓ Base tarball created: ${BASE_SIZE}"
-          echo ""
-
-          # Use static base name (one base per key, immutable)
-          S3_BASE_KEY="s3://${S3_BUCKET}/${PRIMARY_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 "⚠️  Base layer already exists: ${S3_BASE_KEY}"
-            echo "Skipping upload (immutability - first write wins, like GitHub Actions)"
-          else
-            echo "Uploading new base layer to S3..."
-            echo "  Key: ${PRIMARY_KEY}-base.tar.zst"
-
-            aws s3api put-object \
-              --bucket "${S3_BUCKET}" \
-              --key "${PRIMARY_KEY}-base.tar.zst" \
-              --body "${BASE_TARBALL}" \
-              --tagging 'type=base' \
-              --region "${S3_REGION}" \
-              >/dev/null
-
-            echo "✓ Uploaded: ${S3_BASE_KEY}"
-          fi
-
-          # Cleanup
-          rm -f "${BASE_TARBALL}"
-
-          # Unmount and cleanup
-          echo ""
-          echo "Cleaning up..."
-          if mount | grep -q "${CACHE_WORKSPACE}/merged"; then
-            sudo umount "${CACHE_WORKSPACE}/merged" || {
-              echo "⚠️  Warning: Failed to unmount ${CACHE_WORKSPACE}/merged"
-              echo "Attempting lazy unmount..."
-              sudo umount -l "${CACHE_WORKSPACE}/merged" || true
-            }
-          fi
-          rm -rf "${CACHE_WORKSPACE}"
-
-          # Remove from registry
-          if [ -f "${MOUNT_REGISTRY}" ]; then
-            grep -v "^${TARGET_PATH}:" "${MOUNT_REGISTRY}" > "${MOUNT_REGISTRY}.tmp" 2>/dev/null || true
-            mv "${MOUNT_REGISTRY}.tmp" "${MOUNT_REGISTRY}" 2>/dev/null || true
-          fi
-
-          echo "✓ Cleanup completed"
-
-          echo ""
-          echo "=========================================="
-          echo "Partial match cache save completed"
-          echo "New base created for: ${PRIMARY_KEY}"
-          echo "Base size: ${BASE_SIZE}"
-          if [ "${REGISTRY_USE_DELTAS}" = "true" ]; then
-            echo "Next exact-match build will create deltas from this base"
-          else
-            echo "Next exact-match build will reuse this base (base-only mode)"
-          fi
-          echo "=========================================="
-          exit 0
-        fi
-
-        # For exact-match ONLY: Save delta (if use-deltas enabled)
-        if [ "${CACHE_MODE}" = "exact-match" ]; then
-          # If deltas are disabled, just cleanup and exit
-          if [ "${REGISTRY_USE_DELTAS}" != "true" ]; then
-            echo "ℹ️  Delta caching disabled (use-deltas: false)"
-            echo "Base already exists for this key, nothing to save."
-
-            # Unmount and cleanup
-            echo ""
-            echo "Cleaning up..."
-            if mount | grep -q "${CACHE_WORKSPACE}/merged"; then
-              sudo umount "${CACHE_WORKSPACE}/merged" 2>/dev/null || true
-            fi
-            rm -rf "${CACHE_WORKSPACE}"
-
-            # Remove from registry
-            if [ -f "${MOUNT_REGISTRY}" ]; then
-              grep -v "^${TARGET_PATH}:" "${MOUNT_REGISTRY}" > "${MOUNT_REGISTRY}.tmp" 2>/dev/null || true
-              mv "${MOUNT_REGISTRY}.tmp" "${MOUNT_REGISTRY}" 2>/dev/null || true
-            fi
-
-            echo ""
-            echo "=========================================="
-            echo "Cache save completed (base-only mode)"
-            echo "=========================================="
-            exit 0
-          fi
-
-          # Check if upper layer has any changes
-          if [ -z "$(ls -A ${CACHE_WORKSPACE}/upper 2>/dev/null)" ]; then
-            echo "ℹ️  No changes detected in upper layer (cache is unchanged)"
-            echo "Skipping delta upload to save bandwidth."
-
-            # Still unmount and cleanup
-            echo ""
-            echo "Cleaning up..."
-            sudo umount "${CACHE_WORKSPACE}/merged" 2>/dev/null || true
-            rm -rf "${CACHE_WORKSPACE}"
-
-            echo ""
-            echo "=========================================="
-            echo "Cache save completed (no changes)"
-            echo "=========================================="
-            exit 0
-          fi
-
-          # Show delta statistics
-          echo "Delta layer statistics:"
-          echo "  Files changed: $(find ${CACHE_WORKSPACE}/upper -type f 2>/dev/null | wc -l)"
-          echo "  Delta size:    $(du -sh ${CACHE_WORKSPACE}/upper 2>/dev/null | cut -f1)"
-          echo ""
-
-          # Create delta tarball from upper layer
-          echo "Creating delta tarball..."
-          DELTA_TARBALL="/tmp/xahau-cache-delta-$$.tar.zst"
-
-          tar -cf - -C "${CACHE_WORKSPACE}/upper" . | zstd -3 -T0 -q -o "${DELTA_TARBALL}"
-
-          DELTA_SIZE=$(du -h "${DELTA_TARBALL}" | cut -f1)
-          echo "✓ Delta tarball created: ${DELTA_SIZE}"
-          echo ""
-
-          # Upload timestamped delta (no overwrites = zero concurrency issues)
-          TIMESTAMP=$(date +%Y%m%d%H%M%S)
-          COMMIT_SHA=$(git rev-parse --short HEAD 2>/dev/null || echo "unknown")
-
-          # Use PRIMARY_KEY for delta (ensures deltas match their base)
-          S3_DELTA_TIMESTAMPED="s3://${S3_BUCKET}/${PRIMARY_KEY}-delta-${TIMESTAMP}-${COMMIT_SHA}.tar.zst"
-
-          echo "Uploading timestamped delta to S3..."
-          echo "  Key: ${PRIMARY_KEY}-delta-${TIMESTAMP}-${COMMIT_SHA}.tar.zst"
-
-          # Upload with tag (deltas cleaned up inline - keep last 1)
-          aws s3api put-object \
-            --bucket "${S3_BUCKET}" \
-            --key "${PRIMARY_KEY}-delta-${TIMESTAMP}-${COMMIT_SHA}.tar.zst" \
-            --body "${DELTA_TARBALL}" \
-            --tagging 'type=delta-archive' \
-            --region "${S3_REGION}" \
-            >/dev/null
-
-          echo "✓ Uploaded: ${S3_DELTA_TIMESTAMPED}"
-
-          # Inline cleanup: Keep only latest delta (the one we just uploaded)
-          echo ""
-          echo "Cleaning up old deltas (keeping only latest)..."
-
-          # List all deltas for this key, sorted by LastModified (oldest first)
-          ALL_DELTAS=$(aws s3api list-objects-v2 \
-            --bucket "${S3_BUCKET}" \
-            --prefix "${PRIMARY_KEY}-delta-" \
-            --region "${S3_REGION}" \
-            --query 'sort_by(Contents, &LastModified)[*].Key' \
-            --output json 2>/dev/null || echo "[]")
-
-          DELTA_COUNT=$(echo "${ALL_DELTAS}" | jq 'length' 2>/dev/null || echo "0")
-
-          if [ "${DELTA_COUNT}" -gt 1 ]; then
-            # Keep last 1 (newest), delete all older ones (all except last 1 = [0:-1])
-            OLD_DELTAS=$(echo "${ALL_DELTAS}" | jq -r '.[0:-1][]' 2>/dev/null)
-
-            if [ -n "${OLD_DELTAS}" ]; then
-              DELETE_COUNT=$((DELTA_COUNT - 1))
-              echo "  Found ${DELETE_COUNT} old delta(s) to delete"
-
-              # Create delete batch request JSON
-              DELETE_OBJECTS=$(echo "${OLD_DELTAS}" | jq -R -s -c 'split("\n") | map(select(length > 0)) | map({Key: .}) | {Objects: ., Quiet: true}' 2>/dev/null)
-
-              if [ -n "${DELETE_OBJECTS}" ]; then
-                aws s3api delete-objects \
-                  --bucket "${S3_BUCKET}" \
-                  --delete "${DELETE_OBJECTS}" \
-                  --region "${S3_REGION}" \
-                  >/dev/null 2>&1
-
-                echo "✓ Deleted ${DELETE_COUNT} old delta(s)"
-              fi
-            fi
-          else
-            echo "ℹ️  Only ${DELTA_COUNT} delta(s) exist, no cleanup needed"
-          fi
-
-          # Cleanup delta tarball
-          rm -f "${DELTA_TARBALL}"
-
-          # Cleanup: Unmount OverlayFS and remove workspace
-          echo ""
-          echo "Cleaning up..."
-
-          if mount | grep -q "${CACHE_WORKSPACE}/merged"; then
-            sudo umount "${CACHE_WORKSPACE}/merged" || {
-              echo "⚠️  Warning: Failed to unmount ${CACHE_WORKSPACE}/merged"
-              echo "Attempting lazy unmount..."
-              sudo umount -l "${CACHE_WORKSPACE}/merged" || true
-            }
-          fi
-
-          # Remove workspace
-          rm -rf "${CACHE_WORKSPACE}"
-        fi
-
-        # Remove from registry
-        if [ -f "${MOUNT_REGISTRY}" ]; then
-          grep -v "^${TARGET_PATH}:" "${MOUNT_REGISTRY}" > "${MOUNT_REGISTRY}.tmp" 2>/dev/null || true
-          mv "${MOUNT_REGISTRY}.tmp" "${MOUNT_REGISTRY}" 2>/dev/null || true
-        fi
-
-        echo "✓ Cleanup completed"
+        # Cleanup
+        rm -f "${BASE_TARBALL}"
 
         echo ""
         echo "=========================================="
         echo "Cache save completed successfully"
-        echo "Mode: ${CACHE_MODE}"
-        echo "Cache key: ${PRIMARY_KEY}"
-        if [ -n "${DELTA_SIZE:-}" ]; then
-          echo "Delta size: ${DELTA_SIZE}"
-        fi
+        echo "Cache size: ${BASE_SIZE}"
+        echo "Cache key: ${CACHE_KEY}"
         echo "=========================================="

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

@@ -1,45 +0,0 @@
-name: 'Configure ccache'
-description: 'Sets up ccache with consistent configuration'
-
-inputs:
-  cache_dir:
-    description: 'Path to ccache directory'
-    required: false
-    default: '~/.ccache'
-  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'
-
-runs:
-  using: 'composite'
-  steps:
-    - name: Configure ccache
-      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)
-        ccache --set-config=max_size=${{ inputs.max_size }}
-        ccache --set-config=hash_dir=${{ inputs.hash_dir }}
-        ccache --set-config=compiler_check=${{ inputs.compiler_check }}
-
-        # Note: Not setting CCACHE_DIR - let ccache use its default (~/.ccache)
-
-        # Print config for verification
-        ccache -p
-
-        # Zero statistics before the build
-        ccache -z

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

@@ -47,6 +47,18 @@ 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
@@ -79,6 +91,31 @@ runs:
         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=${{ inputs.ccache_compiler_check }}
+
+        # Note: Not setting CCACHE_DIR - let ccache use its default (~/.ccache)
+
+        # Print config for verification
+        echo "=== ccache configuration ==="
+        ccache -p
+
+        # Zero statistics before the build
+        ccache -z
+
     - name: Configure project
       shell: bash
       run: |
@@ -157,31 +194,22 @@ runs:
           -DCMAKE_TOOLCHAIN_FILE:FILEPATH=${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 }}
-        # TEMPORARY: Add -v to see compile commands for ccache debugging
         cmake --build . --config ${{ inputs.configuration }} --parallel $(nproc) -- -v
 
-    - name: Debug ccache directory
-      if: inputs.ccache_enabled == 'true'
-      shell: bash
-      run: |
-        echo "=== ccache directory contents ==="
-        ls -laR ~/.ccache || echo "Directory doesn't exist"
-        echo ""
-        echo "=== Disk space ==="
-        df -h ~
-        echo ""
-        echo "=== ccache config ==="
-        ccache --show-config | head -30
-        echo ""
-        echo "=== Directory sizes ==="
-        du -sh ~/.ccache 2>/dev/null || echo "No directory"
-        find ~/.ccache -type f -name "*.conf" -o -type f ! -name "*.conf" 2>/dev/null | head -20 || true
-        echo ""
-
     - name: Show ccache statistics
       if: inputs.ccache_enabled == 'true'
       shell: bash

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

@@ -81,7 +81,6 @@ runs:
         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 }}-
-        use-deltas: 'false'
         aws-access-key-id: ${{ inputs.aws-access-key-id }}
         aws-secret-access-key: ${{ inputs.aws-secret-access-key }}
 
@@ -166,6 +165,5 @@ runs:
       with:
         path: ~/.conan2
         key: ${{ runner.os }}-conan-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ hashFiles('**/conanfile.txt', '**/conanfile.py') }}-${{ inputs.configuration }}
-        use-deltas: 'false'
         aws-access-key-id: ${{ inputs.aws-access-key-id }}
         aws-secret-access-key: ${{ inputs.aws-secret-access-key }}

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

@@ -78,14 +78,6 @@ 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:"
@@ -130,6 +122,9 @@ 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

@@ -231,13 +231,6 @@ 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
-
       - name: Check environment
         run: |
           echo "PATH:"