diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
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+++ b/.github/workflows/ci.yml
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+# CI pipeline for pull requests targeting master.
+#
+# Package-level steps (install, typecheck, test, build) require the monorepo
+# scaffold (root package.json, pnpm-lock.yaml, turbo tasks) which lands via
+# feat/monorepo-scaffold. Until that PR merges and this branch is rebased,
+# those steps are expected to fail here; everything up to and including
+# pnpm setup runs green.
+name: CI
+
+on:
+  pull_request:
+    branches: [master]
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  ci:
+    name: Typecheck, test, build
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node 20
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Enable pnpm via corepack
+        run: corepack enable
+
+      - name: Resolve pnpm store path
+        id: pnpm-store
+        run: echo "dir=$(pnpm store path --silent)" >> "$GITHUB_OUTPUT"
+
+      - name: Cache pnpm store
+        uses: actions/cache@v4
+        with:
+          path: ${{ steps.pnpm-store.outputs.dir }}
+          key: ${{ runner.os }}-pnpm-store-${{ hashFiles('**/pnpm-lock.yaml') }}
+          restore-keys: ${{ runner.os }}-pnpm-store-
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Typecheck
+        run: pnpm turbo run typecheck
+
+      - name: Unit tests (domain & extraction packages)
+        run: pnpm turbo run test
+
+      - name: Build
+        run: pnpm turbo run build