Functions

A Function is a single source file (TypeScript or Python) attached to an app. Source code lives in Google Cloud Storage; a Firestore manifest tracks which functions an app has and their metadata. At runtime, GenMB's function host loads the source, validates it, and exposes a stable HTTPS endpoint your app can call.

There is no per-app server to provision. All apps share the same function host (a Cloud Run service) and the host loads code on demand, so a brand-new Function is reachable seconds after upload.

Both runtimes receive a request-like object and return a response. The exact shape mirrors what each ecosystem expects, so familiar Node.js or Python patterns work without translation.

export default async function ({ body, headers, query }) {
  return { ok: true, received: body }
}

def handler(event):
    return {"ok": True, "received": event["body"]}

From inside your generated app, call your function with a relative path. The platform handles routing to the function host and authenticates the call on your behalf.

const res = await fetch('/api/fn/my-handler', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ amount: 12.5 }),
})
const data = await res.json()

You can also invoke directly from the editor (a small playground in the Functions panel) to test with sample input before wiring it into your UI.

• Per-function source size: 100 KB.
• Per-invocation timeout: 30 seconds.
• Function name: alphanumeric (with _ or -), up to 64 characters.
• Collaborators on your app inherit the owner's plan, so they are not blocked by their own Free quota.

Functions execute in the multi-tenant function host with per-app isolation. Python functions are statically analyzed before execution; imports of dangerous modules are rejected at upload time.

Secrets your function needs (API keys, third-party tokens) belong in Environment Variables. Never paste secrets directly into source code.

When your prompt implies server-side logic, the code generator can emit Functions as part of the same pass. For example, asking GenMB for "an app that receives a Stripe webhook and updates a row" produces both the UI and a functions/stripe-webhook.ts file. After generation, the finalize step uploads the file and writes the manifest, so the function is live as soon as your app is ready to preview.

FAQs