diff --git a/.env.staging.example b/.env.staging.example
new file mode 100644
index 00000000..39de6783
--- /dev/null
+++ b/.env.staging.example
@@ -0,0 +1,65 @@
+# Staging environment variable overrides
+# ----------------------------------------
+# These are the values that should DIFFER between staging and production.
+# All other variables from .env.example apply unchanged.
+#
+# In Vercel: set these under Settings → Environment Variables, scoped to "Preview"
+# (optionally restricted to the "staging" branch for branch-specific isolation).
+#
+# The staging deployment URL is: https://staging.reactnativevibecode.com
+
+# ── App URLs ────────────────────────────────────────────────────────────────────
+# Tell the app its own public URL so OAuth callbacks and auth work correctly.
+NEXT_PUBLIC_APP_URL=https://staging.reactnativevibecode.com
+NEXT_PUBLIC_BASE_URL=https://staging.reactnativevibecode.com
+NEXT_PUBLIC_SITE_URL=https://staging.reactnativevibecode.com
+# Leave NEXT_PUBLIC_PROD_URL pointing to production (used only when VERCEL_ENV=production)
+NEXT_PUBLIC_PROD_URL=https://www.reactnativevibecode.com
+
+# ── Database ─────────────────────────────────────────────────────────────────────
+# Use a SEPARATE staging database — never share the production database.
+DATABASE_URL=postgresql://USER:PASSWORD@HOST/staging_db
+
+# ── Authentication ────────────────────────────────────────────────────────────────
+# Generate a distinct secret for staging (min 32 chars, never share with production).
+BETTER_AUTH_SECRET=<generate-a-new-32-char-secret-for-staging>
+
+# Google OAuth — create separate OAuth credentials for staging in Google Cloud Console,
+# with Authorized Redirect URIs pointing to staging.reactnativevibecode.com
+GOOGLE_CLIENT_ID=<staging-google-client-id>
+GOOGLE_CLIENT_SECRET=<staging-google-client-secret>
+
+# ── Billing (Polar) ────────────────────────────────────────────────────────────────
+# Use Polar's sandbox server for staging so no real payments are processed.
+POLAR_SERVER=sandbox
+POLAR_ACCESS_TOKEN=<your-polar-sandbox-access-token>
+POLAR_WEBHOOK_SECRET=<your-polar-sandbox-webhook-secret>
+# Sandbox product IDs from your Polar sandbox dashboard
+NEXT_PUBLIC_POLAR_START_PRODUCT_ID=<sandbox-start-product-id>
+NEXT_PUBLIC_POLAR_PRO_PRODUCT_ID=<sandbox-pro-product-id>
+NEXT_PUBLIC_POLAR_SENIOR_PRODUCT_ID=<sandbox-senior-product-id>
+
+# ── Real-time (Pusher) ─────────────────────────────────────────────────────────────
+# Optionally use a separate Pusher app for staging to isolate events.
+NEXT_PUBLIC_PUSHER_APP_KEY=<staging-pusher-key>
+PUSHER_APP_ID=<staging-pusher-app-id>
+PUSHER_APP_SECRET=<staging-pusher-secret>
+NEXT_PUBLIC_PUSHER_CLUSTER=<pusher-cluster>
+
+# ── E2B Sandboxes ─────────────────────────────────────────────────────────────────
+# You can share the same E2B key as production, or use a separate one for staging.
+E2B_API_KEY=<e2b-api-key>
+
+# ── Inngest ───────────────────────────────────────────────────────────────────────
+# Use Inngest's staging/dev branch or a separate app for background jobs.
+INNGEST_EVENT_KEY=<staging-inngest-event-key>
+INNGEST_SIGNING_KEY=<staging-inngest-signing-key>
+
+# ── Additional trusted origins ─────────────────────────────────────────────────────
+# Add your Vercel preview URL pattern here if needed (e.g. Vercel bot previews).
+# The regex .*\.reactnativevibecode\.com already covers staging.reactnativevibecode.com.
+ADDITIONAL_TRUSTED_ORIGINS=https://staging.reactnativevibecode.com
+
+# ── Anthropic ─────────────────────────────────────────────────────────────────────
+# You can share the production key or use a rate-limited staging key.
+ANTHROPIC_API_KEY=<anthropic-api-key>
diff --git a/apps/web/lib/auth/config.ts b/apps/web/lib/auth/config.ts
index 93d5ff1a..d5801205 100644
--- a/apps/web/lib/auth/config.ts
+++ b/apps/web/lib/auth/config.ts
@@ -94,7 +94,11 @@ async function ensureUserSubscription(userId: string, customerId?: string) {
 }
 
 export const auth = betterAuth({
-  baseURL: process.env.NODE_ENV === 'production' ? process.env.NEXT_PUBLIC_PROD_URL || 'https://www.reactnativevibecode.com' : getBaseURL(),
+  // Use VERCEL_ENV (not NODE_ENV) to distinguish production from preview/staging deployments.
+  // Vercel sets NODE_ENV='production' for ALL deployed environments (production AND preview/staging),
+  // so NODE_ENV alone cannot distinguish between them. VERCEL_ENV is 'production' only for
+  // the production branch, and 'preview' for staging/feature branches.
+  baseURL: process.env.VERCEL_ENV === 'production' ? process.env.NEXT_PUBLIC_PROD_URL || 'https://www.reactnativevibecode.com' : getBaseURL(),
   database: drizzleAdapter(db, {
     provider: 'pg',
     schema: {
diff --git a/docs/STAGING_SETUP.md b/docs/STAGING_SETUP.md
new file mode 100644
index 00000000..07540570
--- /dev/null
+++ b/docs/STAGING_SETUP.md
@@ -0,0 +1,186 @@
+# Staging Environment Setup
+
+This guide explains how to configure a persistent staging environment at
+`staging.reactnativevibecode.com` using Vercel.
+
+## How It Works
+
+Vercel automatically deploys every Git branch as a **Preview** deployment. The
+strategy is:
+
+| Branch    | Vercel environment | URL                                    |
+|-----------|--------------------|----------------------------------------|
+| `main`    | Production         | `reactnativevibecode.com`              |
+| `staging` | Preview            | `staging.reactnativevibecode.com`      |
+| `feat/*`  | Preview            | `<auto-generated>.vercel.app`          |
+
+The `staging` branch gets a permanent custom subdomain instead of the ephemeral
+Vercel preview URL. Everything else (feature branches, PRs) continues to use
+auto-generated preview URLs.
+
+---
+
+## Step 1 — Create the `staging` Branch
+
+```bash
+git checkout main
+git pull
+git checkout -b staging
+git push origin staging
+```
+
+Vercel will immediately build and deploy it as a Preview deployment.
+
+---
+
+## Step 2 — Add the Custom Domain in Vercel
+
+1. Open the [Vercel dashboard](https://vercel.com/dashboard) and select the project.
+2. Go to **Settings → Domains**.
+3. Click **Add**.
+4. Enter `staging.reactnativevibecode.com`.
+5. When prompted for **Git Branch**, enter `staging`.
+
+This tells Vercel to always route that domain to the latest deployment from the
+`staging` branch.
+
+---
+
+## Step 3 — Configure DNS
+
+Add a CNAME record with your DNS provider (wherever `reactnativevibecode.com`
+is managed):
+
+| Name      | Type  | Value                   | TTL  |
+|-----------|-------|-------------------------|------|
+| `staging` | CNAME | `cname.vercel-dns.com`  | 3600 |
+
+Vercel will provision a TLS certificate automatically once DNS propagates
+(usually within a few minutes).
+
+---
+
+## Step 4 — Set Environment Variables for Staging
+
+In Vercel: **Settings → Environment Variables**.
+
+For each variable, choose **scope = Preview** and optionally restrict it to the
+`staging` branch. See `.env.staging.example` at the repo root for the full list
+of values that should differ from production.
+
+### Critical variables
+
+| Variable | Staging value |
+|---|---|
+| `NEXT_PUBLIC_APP_URL` | `https://staging.reactnativevibecode.com` |
+| `NEXT_PUBLIC_BASE_URL` | `https://staging.reactnativevibecode.com` |
+| `NEXT_PUBLIC_SITE_URL` | `https://staging.reactnativevibecode.com` |
+| `DATABASE_URL` | A **separate** staging PostgreSQL database |
+| `BETTER_AUTH_SECRET` | A **different** secret from production |
+| `POLAR_SERVER` | `sandbox` (uses Polar's test environment) |
+| `GOOGLE_CLIENT_ID/SECRET` | Separate OAuth credentials (see below) |
+
+### Why a separate database?
+
+The staging database must be isolated from production so that schema migrations,
+test data, and destructive operations cannot affect real users. Provision a
+Neon branch (Neon supports instant database branching) or a separate Neon
+project for staging.
+
+---
+
+## Step 5 — Configure Google OAuth for Staging
+
+Google OAuth credentials require explicit Redirect URIs. Attempting to use
+production credentials from staging will fail.
+
+1. Open [Google Cloud Console](https://console.cloud.google.com) → **APIs & Services → Credentials**.
+2. Create a new **OAuth 2.0 Client ID** (or edit the existing one and add staging URIs).
+3. Add the following **Authorized Redirect URIs**:
+   ```
+   https://staging.reactnativevibecode.com/api/auth/callback/google
+   ```
+4. Set `GOOGLE_CLIENT_ID` and `GOOGLE_CLIENT_SECRET` in Vercel (Preview scope,
+   staging branch) to these staging credentials.
+
+---
+
+## Step 6 — Configure Polar Billing (Sandbox)
+
+Polar provides a full sandbox environment for testing subscriptions without
+real payments.
+
+1. Log in to [Polar](https://polar.sh) and switch to **Sandbox mode** (top-right toggle).
+2. Create products in the sandbox that mirror your production products.
+3. Copy the sandbox access token and product IDs.
+4. Set the following in Vercel (Preview scope):
+   - `POLAR_SERVER=sandbox`
+   - `POLAR_ACCESS_TOKEN=<sandbox token>`
+   - `NEXT_PUBLIC_POLAR_START_PRODUCT_ID=<sandbox id>`
+   - `NEXT_PUBLIC_POLAR_PRO_PRODUCT_ID=<sandbox id>`
+   - `NEXT_PUBLIC_POLAR_SENIOR_PRODUCT_ID=<sandbox id>`
+
+---
+
+## Step 7 — Turbo Remote Cache (already enabled)
+
+Vercel has native Turborepo remote cache support. No additional configuration
+is required — Turbo remote caching is enabled automatically for all Vercel
+deployments, including staging. The `vercel.json` build command already uses
+`turbo run build --filter=@react-native-vibe-code/web`.
+
+---
+
+## Deploying to Staging
+
+```bash
+# Merge a feature branch into staging for QA
+git checkout staging
+git merge feat/my-feature
+git push origin staging
+```
+
+Vercel will automatically build and deploy the updated `staging` branch to
+`https://staging.reactnativevibecode.com`.
+
+To promote staging to production, open a PR from `staging → main` and merge it.
+
+---
+
+## How `VERCEL_ENV` is Used
+
+The app uses `VERCEL_ENV` (set automatically by Vercel) to distinguish
+environments:
+
+| Context | `VERCEL_ENV` | `NODE_ENV` |
+|---|---|---|
+| Vercel Production | `production` | `production` |
+| Vercel Preview / Staging | `preview` | `production` |
+| Local `vercel dev` | `development` | `development` |
+| Local `next dev` | `undefined` | `development` |
+
+`NODE_ENV` is always `production` on Vercel, so the auth config uses
+`VERCEL_ENV === 'production'` to gate the hardcoded production URL. Preview
+deployments (including staging) fall through to `getBaseURL()`, which reads
+`NEXT_PUBLIC_APP_URL` — set to `https://staging.reactnativevibecode.com` in the
+staging Preview env vars.
+
+---
+
+## Troubleshooting
+
+**Auth redirects go to the production domain from staging**
+- Make sure `NEXT_PUBLIC_APP_URL` is set to `https://staging.reactnativevibecode.com`
+  in the Vercel Preview env vars (scoped to the `staging` branch).
+
+**Google OAuth callback fails**
+- Verify the staging redirect URI is added in Google Cloud Console.
+- Verify `GOOGLE_CLIENT_ID/SECRET` in Vercel are the staging credentials.
+
+**Polar webhooks don't arrive on staging**
+- In Polar Sandbox dashboard, add a webhook pointing to
+  `https://staging.reactnativevibecode.com/api/webhooks/polar`.
+
+**Domain shows "Invalid Configuration" in Vercel**
+- Check that the CNAME record for `staging` is live and pointing to
+  `cname.vercel-dns.com`. Use `dig staging.reactnativevibecode.com` to verify.