diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..1e964a3
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,35 @@
+name: CI
+
+on:
+  pull_request:
+    branches: [main, preview]
+  push:
+    branches: [preview]
+  workflow_dispatch: # allows manual trigger from GitHub Actions tab
+
+jobs:
+  build:
+    name: Build check
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npm run build
+        env:
+          DATABASE_URL: ${{ secrets.DATABASE_URL }}
+          NEXTAUTH_SECRET: ${{ secrets.NEXTAUTH_SECRET }}
+          NEXTAUTH_URL: https://dbirecoding.vercel.app
+          RUNNER_URL: https://code-runner-cpqt.onrender.com
+          RUNNER_API_KEY: dummy
diff --git a/README.md b/README.md
index 1235e45..688b636 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # Recoding — Exercise Platform
 
-A controlled environment for running timed coding and writing exercises with live anti-cheat monitoring.
+A controlled environment for running timed coding and writing exercises with live anti-cheat monitoring. 
 
 ---
 
diff --git a/lib/db.ts b/lib/db.ts
index 3f42606..3234a9d 100644
--- a/lib/db.ts
+++ b/lib/db.ts
@@ -13,7 +13,8 @@ if (!process.env.DATABASE_URL) {
 }
 
 if (!process.env.DATABASE_URL) {
-  throw new Error('DATABASE_URL environment variable is not set');
+  // Don't throw at module load (breaks Next.js build) — throw at query time instead
+  console.warn('[db] DATABASE_URL is not set — queries will fail at runtime');
 }
 
 // Use @neondatabase/serverless in Next.js (works over HTTPS, no port 5432 needed)
@@ -37,8 +38,6 @@ async function getQueryFn() {
       return _queryFn;
     } catch { /* fall through to pg */ }
   }
-
-  // pg fallback — works in scripts and when port 5432 is accessible
   const { Pool } = await import('pg');
   const pool = new Pool({ connectionString: process.env.DATABASE_URL });
   pool.on('error', (err) => console.error('[db] Pool error:', err.message));