Vibe-Code Rescue

Platform

Vercel fixes

404s on refresh, missing env vars, timeouts, 500s, and domain setup.

23 fixes, most common first.

  1. Rank 1. Supabase login redirects to localhost:3000 after deploy

    Login or email confirm sends users to localhost:3000 on your live site? Change Supabase's Site URL and add your domain to Redirect URLs.

  2. Rank 2. Invalid API key (Supabase)

    Supabase says "Invalid API key" on your live site? Usually the key or project URL env var is missing, mistyped, or from another project.

  3. Rank 3. Environment variables are undefined in production

    Works locally but env vars are undefined once deployed? Add them to your host, use the VITE_ or NEXT_PUBLIC_ prefix for browser code, then redeploy.

  4. Rank 6. Webhook signature verification failed. No signatures found matching the expected signature for payload

    Stripe webhook fails signature check? Usually the wrong whsec_ secret or your framework changed the raw request body. Here's the fix.

  5. Rank 7. Stripe webhook failing: 404, 307/308 redirect, timeout or 500

    Stripe shows webhook deliveries Failed with 3xx, 4xx, 5xx or timed out? Point it at the exact final URL and respond 200 fast.

  6. Rank 8. Blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present

    "Blocked by CORS policy" on your live site? The server you call must allow your domain. How to fix it for APIs you own and ones you don't.

  7. Rank 10. Vercel 404: NOT_FOUND when refreshing a page or opening a direct link

    Home page works on Vercel but refreshing /dashboard gives 404 NOT_FOUND? Add a rewrite to index.html for your single-page app.

  8. Rank 12. Module not found: Can't resolve (build works locally, fails on Vercel)

    Vercel build fails with "Module not found: Can't resolve" but works on your Mac/PC? Usually filename casing. How to find and fix it.

  9. Rank 13. Changed an environment variable on Vercel but the live site still uses the old value

    Updated a key in Vercel env vars but nothing changed? Env var changes only apply to new deployments. Redeploy and check the right environment.

  10. Rank 21. Vercel FUNCTION_INVOCATION_TIMEOUT (504) on API routes or AI calls

    Vercel API route times out with 504 FUNCTION_INVOCATION_TIMEOUT? Common with slow AI calls. Raise maxDuration, stream, or move work to background.

  11. Rank 22. 500: INTERNAL_SERVER_ERROR / FUNCTION_INVOCATION_FAILED on Vercel

    Live site shows 500 FUNCTION_INVOCATION_FAILED but works locally? Your server code crashed. Read the runtime logs, then check env vars.

  12. Rank 23. too many connections / remaining connection slots are reserved (Supabase + serverless)

    Database errors like "too many connections" after deploying to Vercel? Use Supabase's transaction pooler (port 6543) for serverless functions.

  13. Rank 25. Mixed Content: the page was loaded over HTTPS but requested an insecure resource

    Browser blocks requests with a "Mixed Content" warning on your HTTPS site? Change every http:// URL your app calls to https://.

  14. Rank 26. Vercel custom domain shows "Invalid Configuration"

    Added your domain to Vercel and it says Invalid Configuration? Set the DNS records Vercel shows at your registrar and wait for DNS.

  15. Rank 30. OpenAI API 429: You exceeded your current quota / rate limit reached

    Your app's AI feature fails with OpenAI 429? Either your credits ran out or you're sending requests too fast. How to tell which and fix it.

  16. Rank 31. Invalid JWT after switching to sb_publishable or sb_secret keys

    The app broke after Supabase's new sb_publishable or sb_secret keys? Legacy keys can stay on until you swap them. Don't send the new keys as a Bearer JWT.

  17. Rank 32. Build failed: npm ERR! ERESOLVE

    Vercel stops on npm ERR! ERESOLVE unable to resolve dependency tree? npm is refusing a peer dependency clash. Fix the versions, or override the install command on purpose.

  18. Rank 33. ReferenceError: window is not defined

    Next.js crashes with window is not defined? The page is rendered on the server, where window does not exist. Read it after the component mounts.

  19. Rank 34. Supabase error: JWT expired

    API calls fail with JWT expired? The Supabase access token is meant to be short-lived. Refresh the session once, and don't refresh it twice at the same time.

  20. Rank 35. Clerk sign-in keeps redirecting in a loop

    The app bounces between the page and Clerk sign-in forever? The redirect target is protected too, or the force-redirect URL points back at the gate.

  21. Rank 36. TypeError: Failed to fetch (only in production)

    The live site says Failed to fetch, but the preview worked? The browser could not open the connection. Check the URL, HTTPS, and the console, not the HTTP status.

  22. Rank 37. Vite env var is undefined because the name has no VITE_ prefix

    import.meta.env.MY_KEY is undefined in a Vite app? Vite only exposes names that start with VITE_. Rename it and rebuild.

  23. Rank 39. Prisma on Vercel: query engine not found

    Vercel runs the app and Prisma can't find its query engine? The Rust engine file was left out of the serverless bundle, or Prisma Client was generated for the wrong machine.

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