diff --git a/.github/workflows/bake-and-push.yml b/.github/workflows/_bake-and-push.yml
similarity index 77%
rename from .github/workflows/bake-and-push.yml
rename to .github/workflows/_bake-and-push.yml
index 203208281..747d05366 100644
--- a/.github/workflows/bake-and-push.yml
+++ b/.github/workflows/_bake-and-push.yml
@@ -1,10 +1,10 @@
-name: Bake and Push
+name: Reusable | Bake and Push
 
 permissions:
   contents: read
   actions: read
 
-# Reusable workflow for building and pushing a bake target.
+# Reusable workflow for building and optionally pushing a bake target.
 # Replaces build-docker-image.yml for apps migrated to docker-bake.hcl.
 #
 # Callers pass app-specific build args via the `set` input using GitHub Variables
@@ -25,12 +25,17 @@ on:
         required: true
         type: string
         description: >
-          JSON string. Target OS (e.g. ubuntu-24.04-arm or
-          ['ubuntu-24.04-arm', 'ubuntu-24.04']) of the image
+          JSON string passed to runs-on via fromJSON, e.g.
+          ["ubuntu-24.04-arm"].
       tag:
         required: true
         type: string
-        description: "Image tag to push (e.g. git SHA or semver)"
+        description: "Image tag to build or push (e.g. git SHA or semver)"
+      push:
+        required: false
+        type: boolean
+        default: true
+        description: "Whether to push the built image to the registry"
       base_tag:
         required: false
         type: string
@@ -38,9 +43,8 @@ on:
         description: >
           Pre-built base image tag (BASE_TAG). When set, pulls ui-builder-base
           and ui-runner-base from the registry instead of building them inline.
-          Use this in CI to avoid rebuilding base images on every app push.
-          Omit (or leave empty) to build base images inline — useful when
-          testing base image changes locally via act or in build-base-images.yml.
+          Required for CI app builds so they reuse published base images rather
+          than rebuilding base images inline.
       set:
         required: false
         type: string
@@ -56,9 +60,9 @@ on:
       DATABASE_URL:
         required: false
       DOCKER_HUB_USERNAME:
-        required: true
+        required: false
       DOCKER_HUB_ACCESS_TOKEN:
-        required: true
+        required: false
       PAYLOAD_SECRET:
         required: false
       SENTRY_AUTH_TOKEN:
@@ -82,14 +86,21 @@ jobs:
         id: meta
         run: echo "date=$(date -u +%Y-%m-%dT%H:%M:%SZ)" >> "$GITHUB_OUTPUT"
 
+      - name: Validate base image tag
+        if: ${{ inputs.base_tag == '' }}
+        run: |
+          echo "::error::base_tag is required for CI app builds. Build and publish base images, then set vars.UI_BASE_TAG."
+          exit 1
+
       - uses: docker/setup-buildx-action@v4
 
       - uses: docker/login-action@v4
+        if: ${{ inputs.push }}
         with:
           username: ${{ secrets.DOCKER_HUB_USERNAME }}
           password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
 
-      - name: Build and push
+      - name: Build with Docker bake
         uses: docker/bake-action@v7
         env:
           TAG: ${{ inputs.tag }}
@@ -104,7 +115,7 @@ jobs:
         with:
           files: docker-bake.hcl
           targets: ${{ inputs.target }}
-          push: true
+          push: ${{ inputs.push }}
           set: |
             *.cache-from=type=gha,scope=${{ inputs.target }}
             *.cache-to=type=gha,mode=max,scope=${{ inputs.target }}
diff --git a/.github/workflows/_build-techlabblog.yml b/.github/workflows/_build-techlabblog.yml
new file mode 100644
index 000000000..1d0a4e6b9
--- /dev/null
+++ b/.github/workflows/_build-techlabblog.yml
@@ -0,0 +1,61 @@
+name: Reusable Build | TechLab Blog
+
+on:
+  workflow_call:
+    inputs:
+      tag:
+        required: true
+        type: string
+        description: "Image tag to build or push"
+      push:
+        required: true
+        type: boolean
+        description: "Whether to push the built image to the registry"
+      base_tag:
+        required: true
+        type: string
+        description: "Published base image tag to build from"
+      sentry_environment:
+        required: true
+        type: string
+        description: "Sentry environment baked into the app"
+      set:
+        required: false
+        type: string
+        default: ""
+        description: "Additional bake --set overrides"
+    secrets:
+      DOCKER_HUB_USERNAME:
+        required: false
+      DOCKER_HUB_ACCESS_TOKEN:
+        required: false
+      SENTRY_AUTH_TOKEN:
+        required: false
+      SENTRY_ORG:
+        required: false
+      SENTRY_PROJECT:
+        required: false
+
+jobs:
+  build:
+    permissions:
+      actions: read
+      contents: read
+    uses: ./.github/workflows/_bake-and-push.yml
+    with:
+      target: techlabblog
+      target_os: '["ubuntu-24.04-arm"]'
+      base_tag: ${{ inputs.base_tag }}
+      tag: ${{ inputs.tag }}
+      push: ${{ inputs.push }}
+      # Stable app-level config lives here so PR and main builds share one build contract.
+      set: |
+        techlabblog.args.SENTRY_DSN=${{ vars.TECHLABBLOG_SENTRY_DSN }}
+        techlabblog.args.SENTRY_ENVIRONMENT=${{ inputs.sentry_environment }}
+        ${{ inputs.set }}
+    secrets:
+      DOCKER_HUB_USERNAME: ${{ secrets.DOCKER_HUB_USERNAME }}
+      DOCKER_HUB_ACCESS_TOKEN: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
+      SENTRY_AUTH_TOKEN: ${{ secrets.SENTRY_AUTH_TOKEN }}
+      SENTRY_ORG: ${{ secrets.SENTRY_ORG }}
+      SENTRY_PROJECT: ${{ secrets.SENTRY_PROJECT }}
diff --git a/.github/workflows/_build-trustlab.yml b/.github/workflows/_build-trustlab.yml
new file mode 100644
index 000000000..c6fadd496
--- /dev/null
+++ b/.github/workflows/_build-trustlab.yml
@@ -0,0 +1,59 @@
+name: Reusable Build | TrustLab
+
+on:
+  workflow_call:
+    inputs:
+      tag:
+        required: true
+        type: string
+        description: "Image tag to build or push"
+      push:
+        required: true
+        type: boolean
+        description: "Whether to push the built image to the registry"
+      base_tag:
+        required: true
+        type: string
+        description: "Published base image tag to build from"
+      set:
+        required: false
+        type: string
+        default: ""
+        description: "Additional bake --set overrides"
+    secrets:
+      DATABASE_URL:
+        required: false
+      DOCKER_HUB_USERNAME:
+        required: false
+      DOCKER_HUB_ACCESS_TOKEN:
+        required: false
+      PAYLOAD_SECRET:
+        required: false
+      SENTRY_AUTH_TOKEN:
+        required: false
+      SENTRY_ORG:
+        required: false
+      SENTRY_PROJECT:
+        required: false
+
+jobs:
+  build:
+    permissions:
+      actions: read
+      contents: read
+    uses: ./.github/workflows/_bake-and-push.yml
+    with:
+      target: trustlab
+      target_os: '["ubuntu-24.04-arm"]'
+      base_tag: ${{ inputs.base_tag }}
+      tag: ${{ inputs.tag }}
+      push: ${{ inputs.push }}
+      set: ${{ inputs.set }}
+    secrets:
+      DATABASE_URL: ${{ secrets.DATABASE_URL }}
+      DOCKER_HUB_USERNAME: ${{ secrets.DOCKER_HUB_USERNAME }}
+      DOCKER_HUB_ACCESS_TOKEN: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
+      PAYLOAD_SECRET: ${{ secrets.PAYLOAD_SECRET }}
+      SENTRY_AUTH_TOKEN: ${{ secrets.SENTRY_AUTH_TOKEN }}
+      SENTRY_ORG: ${{ secrets.SENTRY_ORG }}
+      SENTRY_PROJECT: ${{ secrets.SENTRY_PROJECT }}
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 916206732..25bcab2cf 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -24,17 +24,16 @@ jobs:
       TURBO_TOKEN: ${{ secrets.TURBO_TOKEN }}
     strategy:
       matrix:
-        node-version: [24]
         os: [ubuntu-latest]
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 2
 
       # https://github.com/pnpm/action-setup#use-cache-to-reduce-installation-time
       - name: Install pnpm
-        uses: pnpm/action-setup@v4
+        uses: pnpm/action-setup@v6
         id: pnpm-install
         with:
           run_install: false
@@ -46,7 +45,7 @@ jobs:
           echo "STORE_PATH=$(pnpm store path)" >> $GITHUB_OUTPUT
 
       - name: Setup pnpm cache
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: ${{ steps.pnpm-cache.outputs.STORE_PATH }}
           key: ${{ runner.os }}-pnpm-store-${{ hashFiles('**/pnpm-lock.yaml') }}
@@ -56,9 +55,9 @@ jobs:
       # Looks like to use pnpm cache, setup-node must run after pnpm/action-setup
       # https://github.com/actions/setup-node/blob/main/docs/advanced-usage.md#caching-packages-data
       - name: Install Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v6
         with:
-          node-version: ${{ matrix.node-version }}
+          node-version-file: "package.json"
           cache: "pnpm"
 
       - name: Confirm pnpm version
@@ -67,16 +66,18 @@ jobs:
       - name: Install dependencies
         run: pnpm install
 
+      # root task
+      # https://turborepo.dev/docs/guides/tools/oxc#create-root-tasks-1
       - name: Format
-        run: pnpm format:check
+        run: pnpm exec turbo format:check
 
       - name: Lint
         run: pnpm lint:check
 
       # Standard linux runners for public repositories have 4 vCPUs and 16GB of RAM
       # see: https://docs.github.com/en/actions/reference/runners/github-hosted-runners#standard-github-hosted-runners-for-public-repositories
-      - name: Jest
-        run: pnpm jest:ci
+      - name: Test
+        run: pnpm test:ci
 
       # TODO: Re-enable build in a dedicated CI build cleanup PR. The current
       # build surface needs app-scoped env isolation for Payload/Next apps.
diff --git a/.github/workflows/pr-build.yml b/.github/workflows/pr-build.yml
new file mode 100644
index 000000000..5a4bf3146
--- /dev/null
+++ b/.github/workflows/pr-build.yml
@@ -0,0 +1,129 @@
+name: PR Build
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, ready_for_review]
+    paths:
+      - "apps/techlabblog/**"
+      - "apps/trustlab/**"
+      - "docker/apps/techlabblog/**"
+      - "docker/apps/trustlab/**"
+      - "docker-bake.hcl"
+      - "package.json"
+      - "pnpm-lock.yaml"
+      - "pnpm-workspace.yaml"
+      - "turbo.json"
+      - "packages/**"
+      - "scripts/revalidate.mjs"
+      - "scripts/pr-build-targets.mjs"
+      - "scripts/pr-build-targets.test.mjs"
+      - ".github/workflows/_bake-and-push.yml"
+      - ".github/workflows/_build-techlabblog.yml"
+      - ".github/workflows/_build-trustlab.yml"
+      - ".github/workflows/pr-build.yml"
+      - ".github/workflows/techlabblog.yml"
+      - ".github/workflows/trustlab.yml"
+
+permissions:
+  actions: read
+  contents: read
+
+concurrency:
+  group: "${{ github.workflow }} @ ${{ github.event.pull_request.head.label }}"
+  cancel-in-progress: true
+
+jobs:
+  affected:
+    name: Detect affected apps
+    runs-on: ubuntu-24.04
+    outputs:
+      targets: ${{ steps.targets.outputs.targets }}
+    steps:
+      - name: Check PR trust boundary
+        id: trust
+        shell: bash
+        run: |
+          trusted=false
+          if [[ "${{ github.event.pull_request.head.repo.full_name }}" == "${{ github.repository }}" ]]; then
+            case "${{ github.event.pull_request.author_association }}" in
+              OWNER|MEMBER|COLLABORATOR)
+                trusted=true
+                ;;
+            esac
+          fi
+          echo "trusted=${trusted}" >> "$GITHUB_OUTPUT"
+
+      - uses: actions/checkout@v6
+        if: ${{ steps.trust.outputs.trusted == 'true' }}
+        with:
+          fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.sha }}
+
+      - name: Install pnpm
+        if: ${{ steps.trust.outputs.trusted == 'true' }}
+        uses: pnpm/action-setup@v6
+        with:
+          run_install: false
+
+      - name: Install Node.js
+        if: ${{ steps.trust.outputs.trusted == 'true' }}
+        uses: actions/setup-node@v6
+        with:
+          node-version-file: "package.json"
+          cache: "pnpm"
+
+      - name: Install dependencies
+        if: ${{ steps.trust.outputs.trusted == 'true' }}
+        run: pnpm install --frozen-lockfile --ignore-scripts
+
+      - name: Detect app build targets
+        id: targets
+        shell: bash
+        run: |
+          if [[ "${{ steps.trust.outputs.trusted }}" != "true" ]]; then
+            echo "App PR builds are skipped for fork or untrusted PRs."
+            echo "targets=[]" >> "$GITHUB_OUTPUT"
+            exit 0
+          fi
+
+          node scripts/pr-build-targets.mjs \
+            --github-output \
+            --base "${{ github.event.pull_request.base.sha }}" \
+            --head "${{ github.event.pull_request.head.sha }}"
+
+  build-techlabblog:
+    name: Build techlabblog image
+    needs: affected
+    if: ${{ contains(fromJSON(needs.affected.outputs.targets), 'techlabblog') }}
+    permissions:
+      actions: read
+      contents: read
+    uses: ./.github/workflows/_build-techlabblog.yml
+    with:
+      base_tag: ${{ vars.UI_BASE_TAG }}
+      tag: pr-${{ github.event.pull_request.number }}-${{ github.sha }}
+      push: false
+      sentry_environment: ci
+    secrets:
+      SENTRY_AUTH_TOKEN: ${{ secrets.SENTRY_AUTH_TOKEN }}
+      SENTRY_ORG: ${{ secrets.SENTRY_ORG }}
+      SENTRY_PROJECT: ${{ secrets.TECHLABBLOG_SENTRY_PROJECT }}
+
+  build-trustlab:
+    name: Build trustlab image
+    needs: affected
+    if: ${{ contains(fromJSON(needs.affected.outputs.targets), 'trustlab') }}
+    permissions:
+      actions: read
+      contents: read
+    uses: ./.github/workflows/_build-trustlab.yml
+    with:
+      base_tag: ${{ vars.UI_BASE_TAG }}
+      tag: pr-${{ github.event.pull_request.number }}-${{ github.sha }}
+      push: false
+    secrets:
+      DATABASE_URL: ${{ secrets.TRUSTLAB_MONGO_URL }}
+      PAYLOAD_SECRET: ${{ secrets.TRUSTLAB_PAYLOAD_SECRET }}
+      SENTRY_AUTH_TOKEN: ${{ secrets.SENTRY_AUTH_TOKEN }}
+      SENTRY_ORG: ${{ secrets.SENTRY_ORG }}
+      SENTRY_PROJECT: ${{ secrets.TRUSTLAB_SENTRY_PROJECT }}
diff --git a/.github/workflows/techlabblog.yml b/.github/workflows/techlabblog.yml
index 7ded93094..4745d34d5 100644
--- a/.github/workflows/techlabblog.yml
+++ b/.github/workflows/techlabblog.yml
@@ -7,10 +7,10 @@ on:
     paths:
       - "apps/techlabblog/**"
       - "docker/apps/techlabblog/**"
-      - "docker/base.Dockerfile"
       - "docker-bake.hcl"
+      - ".github/workflows/_bake-and-push.yml"
+      - ".github/workflows/_build-techlabblog.yml"
       - ".github/workflows/techlabblog.yml"
-      - ".github/workflows/bake-and-push.yml"
 
 permissions:
   actions: read
@@ -30,9 +30,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        node-version: [24]
         os: [ubuntu-24.04]
-        target_os: [ubuntu-24.04-arm]
     permissions:
       contents: read
     outputs:
@@ -47,7 +45,7 @@ jobs:
       # https://github.com/EndBug/version-check#github-workflow
       - uses: actions/setup-node@v6
         with:
-          node-version: ${{ matrix.node-version }}
+          node-version-file: "package.json"
 
       - name: Check if version is bumped
         id: check
@@ -68,28 +66,23 @@ jobs:
   #   codeforafrica/techlabblog:latest     — version bump only (mutable, for convenience)
   #
   # Required GitHub Variables:
-  #   TECHLABBLOG_SENTRY_DSN
+  #   TECHLABBLOG_SENTRY_DSN, UI_BASE_TAG
   #
   # Required GitHub Secrets (for Sentry source map upload during build):
   #   SENTRY_AUTH_TOKEN, SENTRY_ORG, TECHLABBLOG_SENTRY_PROJECT
   #
-  # TODO: Set BASE_TAG below to a published base image version (e.g. v3) once
-  # base images are built and pushed via build-base-images.yml. Until then,
-  # base images are built inline (slower but correct).
   build:
     needs: version-check
     permissions:
       actions: read
       contents: read
-    uses: ./.github/workflows/bake-and-push.yml
+    uses: ./.github/workflows/_build-techlabblog.yml
     with:
-      target: techlabblog
-      target_os: "['ubuntu-24.04-arm']"
       base_tag: ${{ vars.UI_BASE_TAG }}
       tag: ${{ github.sha }}
+      push: true
+      sentry_environment: production
       set: |
-        techlabblog.args.SENTRY_DSN=${{ vars.TECHLABBLOG_SENTRY_DSN }}
-        techlabblog.args.SENTRY_ENVIRONMENT=production
         ${{ needs.version-check.outputs.changed == 'true' && format('techlabblog.tags=codeforafrica/techlabblog:{0}', github.sha) || '' }}
         ${{ needs.version-check.outputs.changed == 'true' && format('techlabblog.tags=codeforafrica/techlabblog:{0}', needs.version-check.outputs.version) || '' }}
         ${{ needs.version-check.outputs.changed == 'true' && 'techlabblog.tags=codeforafrica/techlabblog:latest' || '' }}
diff --git a/.github/workflows/trustlab.yml b/.github/workflows/trustlab.yml
index 2c402e0f0..07cd4cc0a 100644
--- a/.github/workflows/trustlab.yml
+++ b/.github/workflows/trustlab.yml
@@ -7,11 +7,11 @@ on:
     paths:
       - "apps/trustlab/**"
       - "docker/apps/trustlab/**"
-      - "docker/base.Dockerfile"
       - "docker-bake.hcl"
       - "scripts/revalidate.mjs"
+      - ".github/workflows/_bake-and-push.yml"
+      - ".github/workflows/_build-trustlab.yml"
       - ".github/workflows/trustlab.yml"
-      - ".github/workflows/bake-and-push.yml"
 
 permissions:
   actions: read
@@ -26,7 +26,6 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        node-version: [24]
         os: [ubuntu-24.04]
     permissions:
       contents: read
@@ -40,7 +39,7 @@ jobs:
 
       - uses: actions/setup-node@v6
         with:
-          node-version: ${{ matrix.node-version }}
+          node-version-file: "package.json"
 
       - name: Check if version is bumped
         id: check
@@ -55,12 +54,11 @@ jobs:
     permissions:
       actions: read
       contents: read
-    uses: ./.github/workflows/bake-and-push.yml
+    uses: ./.github/workflows/_build-trustlab.yml
     with:
-      target: trustlab
-      target_os: "['ubuntu-24.04-arm']"
       base_tag: ${{ vars.UI_BASE_TAG }}
       tag: ${{ github.sha }}
+      push: true
       set: |
         ${{ needs.version-check.outputs.changed == 'true' && format('trustlab.tags=codeforafrica/trustlab:{0}', github.sha) || '' }}
         ${{ needs.version-check.outputs.changed == 'true' && format('trustlab.tags=codeforafrica/trustlab:{0}', needs.version-check.outputs.version) || '' }}
diff --git a/package.json b/package.json
index 08e9e5a04..2f4a7f101 100644
--- a/package.json
+++ b/package.json
@@ -21,7 +21,9 @@
     "jest:coverage": "turbo run jest -- --coverage",
     "jest:debug": "turbo run jest --concurrency=1 -- --runInBand --detectOpenHandles",
     "playwright": "turbo run playwright",
-    "test": "turbo run jest playwright --parallel",
+    "test": "pnpm test:scripts && pnpm jest",
+    "test:ci": "pnpm test:scripts && pnpm jest:ci",
+    "test:scripts": "node --test scripts/*.test.mjs",
     "clean": "turbo run clean && rm -rf node_modules",
     "format:check": "oxfmt --check .",
     "format": "oxfmt .",
diff --git a/scripts/pr-build-targets.mjs b/scripts/pr-build-targets.mjs
new file mode 100644
index 000000000..413fe7d5f
--- /dev/null
+++ b/scripts/pr-build-targets.mjs
@@ -0,0 +1,205 @@
+#!/usr/bin/env node
+
+import { spawnSync } from "node:child_process";
+import { appendFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+
+// Policy:
+// - Turbo owns workspace impact detection, including package-to-app dependents.
+// - Only workspaces under apps/ can become PR build targets.
+// - Only Docker-migrated apps are buildable by this workflow today.
+// - Non-workspace build inputs are handled explicitly because Turbo cannot map
+//   them through the workspace graph.
+export const BUILD_TARGET_CONFIG = {
+  techlabblog: {
+    directBuildInputPaths: [
+      ".github/workflows/techlabblog.yml",
+      "docker/apps/techlabblog/",
+    ],
+  },
+  trustlab: {
+    directBuildInputPaths: [
+      ".github/workflows/trustlab.yml",
+      "docker/apps/trustlab/",
+      "scripts/revalidate.mjs",
+    ],
+  },
+};
+
+const GLOBAL_BUILD_FILES = new Set([
+  ".github/workflows/_bake-and-push.yml",
+  ".github/workflows/_build-techlabblog.yml",
+  ".github/workflows/_build-trustlab.yml",
+  ".github/workflows/pr-build.yml",
+  "scripts/pr-build-targets.mjs",
+  "docker-bake.hcl",
+  "package.json",
+  "pnpm-lock.yaml",
+  "pnpm-workspace.yaml",
+  "turbo.json",
+]);
+
+function parseArgs(argv) {
+  const args = {
+    base: "origin/main",
+    githubOutput: false,
+    head: "HEAD",
+  };
+
+  for (let i = 0; i < argv.length; i += 1) {
+    const arg = argv[i];
+    if (arg === "--base") {
+      args.base = readOptionValue(argv, ++i, arg);
+    } else if (arg === "--github-output") {
+      args.githubOutput = true;
+    } else if (arg === "--head") {
+      args.head = readOptionValue(argv, ++i, arg);
+    } else {
+      throw new Error(`Unknown argument: ${arg}`);
+    }
+  }
+  return args;
+}
+
+function readOptionValue(argv, index, option) {
+  const value = argv[index];
+  if (!value || value.startsWith("--")) {
+    throw new Error(`Missing value for ${option}`);
+  }
+  return value;
+}
+
+function run(command, args, options = {}) {
+  const result = spawnSync(command, args, {
+    encoding: "utf8",
+    stdio: ["ignore", "pipe", "pipe"],
+    ...options,
+  });
+
+  if (result.status !== 0) {
+    throw new Error(
+      [`Command failed: ${command} ${args.join(" ")}`, result.stderr.trim()]
+        .filter(Boolean)
+        .join("\n"),
+    );
+  }
+  return result.stdout;
+}
+
+function writeGitHubOutputs(outputs, outputFile) {
+  if (!outputFile) {
+    throw new Error("GITHUB_OUTPUT is required when using --github-output");
+  }
+
+  const output = Object.entries(outputs)
+    .map(([key, value]) => {
+      const normalizedValue = Array.isArray(value)
+        ? JSON.stringify(value)
+        : String(value);
+      return `${key}=${normalizedValue}`;
+    })
+    .join("\n");
+  appendFileSync(outputFile, `${output}\n`);
+}
+
+export function changedFilesFromGit(base, head) {
+  // Triple-dot matches PR semantics: files changed on head since the merge base.
+  return run("git", ["diff", "--name-only", `${base}...${head}`])
+    .split("\n")
+    .map((file) => file.trim())
+    .filter(Boolean);
+}
+
+export function hasGlobalBuildChange(changedFiles) {
+  return changedFiles.some((file) => GLOBAL_BUILD_FILES.has(file));
+}
+
+export function directBuildTargets(changedFiles) {
+  return changedFiles.flatMap((file) => {
+    return Object.entries(BUILD_TARGET_CONFIG)
+      .filter(([, config]) =>
+        config.directBuildInputPaths.some((path) => matchesPath(file, path)),
+      )
+      .map(([app]) => app);
+  });
+}
+
+function matchesPath(file, path) {
+  // Paths ending in "/" match all children.
+  return path.endsWith("/") ? file.startsWith(path) : file === path;
+}
+
+export function parseTurboBuildTargets(turboOutput) {
+  const data = parseTurboJson(turboOutput);
+  const packages = data.packages?.items ?? [];
+  return packages
+    .filter(
+      (pkg) =>
+        pkg.path?.startsWith("apps/") &&
+        Object.hasOwn(BUILD_TARGET_CONFIG, pkg.name),
+    )
+    .map((pkg) => pkg.name);
+}
+
+function parseTurboJson(turboOutput) {
+  const start = turboOutput.indexOf("{");
+  if (start === -1) {
+    throw new Error("Turbo output did not include JSON");
+  }
+  const end = turboOutput.lastIndexOf("}");
+  if (end < start) {
+    throw new Error("Turbo JSON was incomplete");
+  }
+
+  return JSON.parse(turboOutput.slice(start, end + 1));
+}
+
+export function turboBuildTargets(base, head) {
+  const turboOutput = run(
+    "pnpm",
+    ["exec", "turbo", "ls", "--affected", "--output=json"],
+    {
+      env: {
+        ...process.env,
+        TURBO_SCM_BASE: base,
+        TURBO_SCM_HEAD: head,
+      },
+    },
+  );
+  return parseTurboBuildTargets(turboOutput);
+}
+
+export function buildTargets({ base, head }) {
+  const changedFiles = changedFilesFromGit(base, head);
+  if (hasGlobalBuildChange(changedFiles)) {
+    return Object.keys(BUILD_TARGET_CONFIG).sort();
+  }
+  return [
+    ...new Set([
+      ...directBuildTargets(changedFiles),
+      ...turboBuildTargets(base, head),
+    ]),
+  ].sort();
+}
+
+function main() {
+  const args = parseArgs(process.argv.slice(2));
+  const targets = buildTargets(args);
+  const outputs = { targets };
+
+  if (args.githubOutput) {
+    writeGitHubOutputs(outputs, process.env.GITHUB_OUTPUT);
+  }
+  process.stdout.write(`${JSON.stringify(outputs)}\n`);
+}
+
+const invokedPath =
+  process.argv[1] && fileURLToPath(import.meta.url) === process.argv[1];
+if (invokedPath) {
+  try {
+    main();
+  } catch (error) {
+    process.stderr.write(`${error.message}\n`);
+    process.exitCode = 1;
+  }
+}
diff --git a/scripts/pr-build-targets.test.mjs b/scripts/pr-build-targets.test.mjs
new file mode 100644
index 000000000..e60ccce5b
--- /dev/null
+++ b/scripts/pr-build-targets.test.mjs
@@ -0,0 +1,71 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+
+import {
+  directBuildTargets,
+  hasGlobalBuildChange,
+  parseTurboBuildTargets,
+} from "./pr-build-targets.mjs";
+
+describe("pr-build-targets", () => {
+  it("detects global build inputs that require all build targets", () => {
+    assert.equal(hasGlobalBuildChange(["docker-bake.hcl"]), true);
+    assert.equal(hasGlobalBuildChange(["scripts/pr-build-targets.mjs"]), true);
+    assert.equal(hasGlobalBuildChange(["pnpm-lock.yaml"]), true);
+    assert.equal(hasGlobalBuildChange(["turbo.json"]), true);
+    assert.equal(
+      hasGlobalBuildChange(["packages/commons-ui-core/index.js"]),
+      false,
+    );
+  });
+
+  it("maps direct build input paths to candidate build targets", () => {
+    assert.deepEqual(
+      directBuildTargets([
+        "docker/apps/techlabblog/Dockerfile",
+        ".github/workflows/trustlab.yml",
+      ]),
+      ["techlabblog", "trustlab"],
+    );
+  });
+
+  it("filters Turbo package output to build targets", () => {
+    const turboOutput = `
+      {
+        "packages": {
+          "items": [
+            { "name": "techlabblog", "path": "apps/techlabblog" },
+            { "name": "commons-ui-core", "path": "packages/commons-ui-core" },
+            { "name": "pesayetu", "path": "apps/pesayetu" },
+            { "name": "trustlab", "path": "apps/trustlab" }
+          ]
+        }
+      }`;
+
+    assert.deepEqual(parseTurboBuildTargets(turboOutput), [
+      "techlabblog",
+      "trustlab",
+    ]);
+  });
+
+  it("ignores Turbo output before and after JSON when on different lines", () => {
+    const turboOutput = `warning before json 
+      {
+        "packages": {
+          "items": [
+            { "name": "techlabblog", "path": "apps/techlabblog" }
+          ]
+        }
+      }
+      status after json`;
+
+    assert.deepEqual(parseTurboBuildTargets(turboOutput), ["techlabblog"]);
+  });
+
+  it("ignores Turbo output before and after JSON when on the same line", () => {
+    const turboOutput =
+      'warning {"packages":{"items":[{"name":"trustlab","path":"apps/trustlab"}]}} status';
+
+    assert.deepEqual(parseTurboBuildTargets(turboOutput), ["trustlab"]);
+  });
+});
diff --git a/turbo.json b/turbo.json
index a387b9828..7f38749a0 100644
--- a/turbo.json
+++ b/turbo.json
@@ -24,9 +24,6 @@
     "playwright": {
       "dependsOn": ["build"]
     },
-    "test": {
-      "dependsOn": ["build"]
-    },
     "lint:check": {
       "dependsOn": ["^lint:check"]
     },