diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..6fb4f74
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,35 @@
+name: CI
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+concurrency:
+  group: ci-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    name: Build site
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+
+      - run: npm install
+
+      # Same command the deploy workflow runs, so a page that breaks the
+      # export is caught on the PR rather than after it lands on main.
+      # MARKLINE_AI_KEY is unset here; the export skips AI suggestions
+      # gracefully without it.
+      - run: npx markline export