diff --git a/.forgejo/workflows/ci.yml b/.forgejo/workflows/ci.yml
index fada4116..1f16d305 100644
--- a/.forgejo/workflows/ci.yml
+++ b/.forgejo/workflows/ci.yml
@@ -4,27 +4,20 @@ on:
   push:
     branches: ['release/*']
   pull_request:
-    branches: [main]
+    branches: [main, 'release/*']
 
 jobs:
   ci:
     runs-on: docker
     container:
-      image: catthehacker/ubuntu:act-latest
+      image: forge.lvl0.xyz/lvl0/fedi-feed-router-ci:php8.3-2
     steps:
       - uses: https://data.forgejo.org/actions/checkout@v4
 
-      - name: Set up PHP
-        uses: https://github.com/shivammathur/setup-php@v2
-        with:
-          php-version: '8.3'
-          extensions: pdo_sqlite, mbstring, xml, dom
-          coverage: pcov
-
       - name: Cache Composer dependencies
         uses: https://data.forgejo.org/actions/cache@v4
         with:
-          path: ~/.composer/cache
+          path: ~/.cache/composer
           key: composer-${{ hashFiles('composer.lock') }}
           restore-keys: composer-
 
@@ -41,4 +34,4 @@ jobs:
         run: vendor/bin/phpstan analyse --memory-limit=1G
 
       - name: Tests
-        run: php artisan test --coverage-clover coverage.xml --coverage-text
+        run: php -d memory_limit=512M vendor/bin/phpunit
diff --git a/.forgejo/workflows/images.yml b/.forgejo/workflows/images.yml
new file mode 100644
index 00000000..ba694bfd
--- /dev/null
+++ b/.forgejo/workflows/images.yml
@@ -0,0 +1,47 @@
+name: Build and Push Base Images
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'docker/build/**'
+      - '.forgejo/workflows/images.yml'
+  workflow_dispatch:
+
+jobs:
+  images:
+    runs-on: docker
+    container:
+      image: catthehacker/ubuntu:act-latest
+    strategy:
+      matrix:
+        include:
+          - name: fedi-feed-router-base
+            file: docker/build/Dockerfile.base
+            version: php8.3-1
+          - name: fedi-feed-router-ci
+            file: docker/build/Dockerfile.ci
+            version: php8.3-2
+    steps:
+      - uses: https://data.forgejo.org/actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: https://data.forgejo.org/docker/setup-buildx-action@v3
+
+      - name: Login to Forgejo Registry
+        uses: https://data.forgejo.org/docker/login-action@v3
+        with:
+          registry: forge.lvl0.xyz
+          username: ${{ github.actor }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      - name: Build and push
+        uses: https://data.forgejo.org/docker/build-push-action@v5
+        with:
+          context: .
+          file: ${{ matrix.file }}
+          push: true
+          tags: |
+            forge.lvl0.xyz/lvl0/${{ matrix.name }}:${{ matrix.version }}
+            forge.lvl0.xyz/lvl0/${{ matrix.name }}:latest
+            forge.lvl0.xyz/lvl0/${{ matrix.name }}:${{ github.sha }}
diff --git a/composer.json b/composer.json
index 0254fbae..99b45229 100644
--- a/composer.json
+++ b/composer.json
@@ -14,6 +14,7 @@
     "license": "AGPL-3.0-only",
     "require": {
         "php": "^8.2",
+        "ext-gd": "*",
         "blade-ui-kit/blade-heroicons": "^2.6",
         "laravel/framework": "^12.0",
         "laravel/horizon": "^5.29",
diff --git a/composer.lock b/composer.lock
index 665abac6..fabaf870 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "e6ce5effb7f8c4d5a3f6d8cd04b6e299",
+    "content-hash": "67923d1e9e79798f3ebe2e79954f4795",
     "packages": [
         {
             "name": "blade-ui-kit/blade-heroicons",
@@ -8747,7 +8747,8 @@
     "prefer-stable": true,
     "prefer-lowest": false,
     "platform": {
-        "php": "^8.2"
+        "php": "^8.2",
+        "ext-gd": "*"
     },
     "platform-dev": {},
     "plugin-api-version": "2.6.0"
diff --git a/docker/build/Dockerfile.ci b/docker/build/Dockerfile.ci
new file mode 100644
index 00000000..50857a02
--- /dev/null
+++ b/docker/build/Dockerfile.ci
@@ -0,0 +1,32 @@
+# Image for CI: PHP and Composer only, no runtime server or frontend toolchain.
+# Tests run against sqlite in memory (see .env.testing), so no database client
+# or cache extension is needed.
+#
+# Published as fedi-feed-router-ci:php<version>-<revision>, not :latest. Runners
+# cache mutable tags and will not re-pull them, so bump the revision in the tag
+# and in ci.yml whenever this file changes.
+#
+# Debian-based rather than alpine: the alpine build hit repeated DNS resolution
+# timeouts against codeload.github.com during composer install.
+#
+# gd is not declared in composer.lock but ThumbnailUploader calls it directly.
+FROM php:8.3-cli
+
+COPY --from=mlocati/php-extension-installer:2 /usr/bin/install-php-extensions /usr/local/bin/
+
+RUN install-php-extensions \
+    pdo_sqlite \
+    mbstring \
+    dom \
+    xml \
+    fileinfo \
+    pcntl \
+    gd
+
+# nodejs is not used by the app's tests; the Forgejo/GitHub JavaScript actions
+# (checkout, cache) are executed with it inside this container.
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends git unzip nodejs \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY --from=composer:2 /usr/bin/composer /usr/bin/composer