diff --git a/.gitea/workflows/ci.yml b/.gitea/workflows/ci.yml
index a792eaa..02a2068 100644
--- a/.gitea/workflows/ci.yml
+++ b/.gitea/workflows/ci.yml
@@ -20,14 +20,20 @@ jobs:
       - uses: actions/checkout@v4
 
       # setup-php installs PHP 8.3+ through php-builder, which apt-installs ~70
-      # -dev packages before unpacking the build (#178). Ubuntu's own image
-      # deletes the .debs after install, so every job re-downloads them from
-      # the archive. Keep them and restore them from the cache server, which
-      # lives in the cluster, turning a WAN download into a local one.
+      # -dev packages before unpacking the build (#178). Ubuntu's image deletes
+      # the .debs after install, so every job re-downloads them. Keeping them
+      # and restoring them from the cache server, which lives in the cluster,
+      # turns a WAN download into a local one.
       #
-      # The dep list is the same for every PHP version on the builder path, so
-      # one shared key serves them all. Only the .debs are cached, never
-      # /var/lib/apt/lists — a stale index is how you get 404s on install.
+      # Keyed per PHP version because the install path differs by version and
+      # the package sets are not interchangeable: 8.3+ pulls the ~70 -dev
+      # packages through php-builder, while 8.1 and 8.2 come from the ondrej
+      # PPA as a handful of runtime packages. Sharing one key across both lets
+      # whichever job finishes first decide what the others restore, and 8.1 is
+      # always first.
+      #
+      # Only the .debs are cached, never /var/lib/apt/lists — a stale index is
+      # how you get 404s mid-install.
       - name: Keep downloaded .debs
         run: |
           sudo rm -f /etc/apt/apt.conf.d/docker-clean
@@ -38,16 +44,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: /var/cache/apt/archives/*.deb
-          key: apt-php-builder-deps-${{ runner.arch }}-v1
-
-      # Temporary, for #178: shows whether the cache actually served the
-      # builder's dependencies, and times the step that consumes them.
-      - name: Report restored .debs
-        run: |
-          echo "ACTIONS_CACHE_URL: ${ACTIONS_CACHE_URL:-<unset>}"
-          echo "restored .debs: $(ls /var/cache/apt/archives/*.deb 2>/dev/null | wc -l)"
-          echo "restored size:  $(du -sh /var/cache/apt/archives 2>/dev/null | cut -f1)"
-          date -u +'setup-php start: %H:%M:%S'
+          key: apt-php8.3-${{ runner.arch }}-v1
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
@@ -84,14 +81,20 @@ jobs:
       - uses: actions/checkout@v4
 
       # setup-php installs PHP 8.3+ through php-builder, which apt-installs ~70
-      # -dev packages before unpacking the build (#178). Ubuntu's own image
-      # deletes the .debs after install, so every job re-downloads them from
-      # the archive. Keep them and restore them from the cache server, which
-      # lives in the cluster, turning a WAN download into a local one.
+      # -dev packages before unpacking the build (#178). Ubuntu's image deletes
+      # the .debs after install, so every job re-downloads them. Keeping them
+      # and restoring them from the cache server, which lives in the cluster,
+      # turns a WAN download into a local one.
       #
-      # The dep list is the same for every PHP version on the builder path, so
-      # one shared key serves them all. Only the .debs are cached, never
-      # /var/lib/apt/lists — a stale index is how you get 404s on install.
+      # Keyed per PHP version because the install path differs by version and
+      # the package sets are not interchangeable: 8.3+ pulls the ~70 -dev
+      # packages through php-builder, while 8.1 and 8.2 come from the ondrej
+      # PPA as a handful of runtime packages. Sharing one key across both lets
+      # whichever job finishes first decide what the others restore, and 8.1 is
+      # always first.
+      #
+      # Only the .debs are cached, never /var/lib/apt/lists — a stale index is
+      # how you get 404s mid-install.
       - name: Keep downloaded .debs
         run: |
           sudo rm -f /etc/apt/apt.conf.d/docker-clean
@@ -102,16 +105,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: /var/cache/apt/archives/*.deb
-          key: apt-php-builder-deps-${{ runner.arch }}-v1
-
-      # Temporary, for #178: shows whether the cache actually served the
-      # builder's dependencies, and times the step that consumes them.
-      - name: Report restored .debs
-        run: |
-          echo "ACTIONS_CACHE_URL: ${ACTIONS_CACHE_URL:-<unset>}"
-          echo "restored .debs: $(ls /var/cache/apt/archives/*.deb 2>/dev/null | wc -l)"
-          echo "restored size:  $(du -sh /var/cache/apt/archives 2>/dev/null | cut -f1)"
-          date -u +'setup-php start: %H:%M:%S'
+          key: apt-php${{ matrix.php }}-${{ runner.arch }}-v1
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
@@ -157,14 +151,20 @@ jobs:
       - uses: actions/checkout@v4
 
       # setup-php installs PHP 8.3+ through php-builder, which apt-installs ~70
-      # -dev packages before unpacking the build (#178). Ubuntu's own image
-      # deletes the .debs after install, so every job re-downloads them from
-      # the archive. Keep them and restore them from the cache server, which
-      # lives in the cluster, turning a WAN download into a local one.
+      # -dev packages before unpacking the build (#178). Ubuntu's image deletes
+      # the .debs after install, so every job re-downloads them. Keeping them
+      # and restoring them from the cache server, which lives in the cluster,
+      # turns a WAN download into a local one.
       #
-      # The dep list is the same for every PHP version on the builder path, so
-      # one shared key serves them all. Only the .debs are cached, never
-      # /var/lib/apt/lists — a stale index is how you get 404s on install.
+      # Keyed per PHP version because the install path differs by version and
+      # the package sets are not interchangeable: 8.3+ pulls the ~70 -dev
+      # packages through php-builder, while 8.1 and 8.2 come from the ondrej
+      # PPA as a handful of runtime packages. Sharing one key across both lets
+      # whichever job finishes first decide what the others restore, and 8.1 is
+      # always first.
+      #
+      # Only the .debs are cached, never /var/lib/apt/lists — a stale index is
+      # how you get 404s mid-install.
       - name: Keep downloaded .debs
         run: |
           sudo rm -f /etc/apt/apt.conf.d/docker-clean
@@ -175,16 +175,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: /var/cache/apt/archives/*.deb
-          key: apt-php-builder-deps-${{ runner.arch }}-v1
-
-      # Temporary, for #178: shows whether the cache actually served the
-      # builder's dependencies, and times the step that consumes them.
-      - name: Report restored .debs
-        run: |
-          echo "ACTIONS_CACHE_URL: ${ACTIONS_CACHE_URL:-<unset>}"
-          echo "restored .debs: $(ls /var/cache/apt/archives/*.deb 2>/dev/null | wc -l)"
-          echo "restored size:  $(du -sh /var/cache/apt/archives 2>/dev/null | cut -f1)"
-          date -u +'setup-php start: %H:%M:%S'
+          key: apt-php8.3-${{ runner.arch }}-v1
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2