diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..b2f93e7
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,37 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version-file: '.nvmrc'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Lint
+        run: npm run lint
+        continue-on-error: true  # TODO: fix pre-existing lint errors then remove this
+
+      - name: Type check
+        run: npm run type-check
+
+      - name: Build
+        run: npm run build
+        env:
+          NEXT_PUBLIC_SUPABASE_URL: https://placeholder.supabase.co
+          NEXT_PUBLIC_SUPABASE_ANON_KEY: placeholder-anon-key
+          NEXT_PUBLIC_DEMO_MODE: 'true'
diff --git a/docs/CONTRIBUTING.md b/docs/CONTRIBUTING.md
new file mode 100644
index 0000000..75a3afc
--- /dev/null
+++ b/docs/CONTRIBUTING.md
@@ -0,0 +1,71 @@
+# Contributing to Project Firefly
+
+## Branching Model
+
+We use **GitHub Flow** — a simple branch-based workflow.
+
+- `main` is always production-ready and auto-deploys to Vercel production
+- All work happens on feature branches created from `main`
+- Every PR gets an automatic Vercel preview deployment for QA
+
+### Branch Naming
+
+Use a prefix that describes the type of change:
+
+| Prefix | Use for |
+|---|---|
+| `feature/` | New functionality |
+| `fix/` | Bug fixes |
+| `chore/` | Tooling, config, refactors, docs |
+
+Examples: `feature/auth-layer`, `fix/checkout-redirect`, `chore/update-deps`
+
+## Pull Request Process
+
+1. Create a branch from `main`:
+   ```bash
+   git checkout main && git pull
+   git checkout -b feature/my-feature
+   ```
+
+2. Make your changes, commit, and push:
+   ```bash
+   git push -u origin feature/my-feature
+   ```
+
+3. Open a PR targeting `main` on GitHub.
+
+4. CI must pass before merging. The pipeline runs:
+   - **Lint** — `npm run lint`
+   - **Type check** — `npm run type-check`
+   - **Build** — `npm run build`
+
+5. Get a code review, then **squash-merge** to `main`.
+
+## CI Requirements
+
+All PRs must pass the CI pipeline before merging. You can run the checks locally:
+
+```bash
+npm run lint
+npm run type-check
+npm run build
+```
+
+## Local Development
+
+```bash
+# Install dependencies
+npm install
+
+# Copy environment variables
+cp .env.local.example .env.local
+# Fill in your Supabase project credentials
+
+# Start dev server
+npm run dev
+```
+
+## Environment Variables
+
+See `.env.local.example` for all required variables. Refer to `docs/ENVIRONMENTS.md` for environment-specific configuration.
diff --git a/package.json b/package.json
index b6a524a..eaf1d0f 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,8 @@
     "dev": "next dev",
     "build": "next build",
     "start": "next start",
-    "lint": "eslint"
+    "lint": "eslint",
+    "type-check": "tsc --noEmit"
   },
   "dependencies": {
     "@radix-ui/react-avatar": "^1.1.11",