Cloud Functions errorFirebase callable functions: error INTERNAL (functions/internal)

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Why the client gets INTERNAL, and the fix

1. 01

   A plain error escapes the handler

   “If an error other than an HTTPS error is thrown from your functions, your client instead receives an error with the message INTERNAL and the code internal.” Firebase, Call functions from your app

   A failed database write, a missing environment value or a bug throws a normal Error, and the client only sees INTERNAL. Log the real error and throw an HttpsError.

   const { onCall, HttpsError } = require('firebase-functions/https');
   const { logger } = require('firebase-functions');
   
   exports.createOrder = onCall(async (request) => {
     if (!request.auth) {
       throw new HttpsError('unauthenticated', 'Sign in first.');
     }
     try {
       return await saveOrder(request.data);
     } catch (err) {
       if (err instanceof HttpsError) throw err;
       logger.error(err);
       throw new HttpsError('internal', 'Could not save the order.');
     }
   });

2. 02

   The client calls a different region

   “To call a function running in any location other than us-central1, you must set the appropriate value at initialization.” Firebase, Call functions from your app

   A function deployed to europe-west1 and a client left on the default region never meet; the client may see INTERNAL or NOT_FOUND. Pass the region when you get the functions instance, such as getFunctions(app, 'europe-west1').

3. 03

   The function is onRequest, not onCall

   httpsCallable expects a function written with onCall. An onRequest function returns a plain HTTP response, so call it with fetch or rewrite it as onCall.

4. 04

   The function crashed or timed out

   Out-of-memory and timeout failures are recorded in the logs, while the client may see INTERNAL, UNAVAILABLE or DEADLINE_EXCEEDED. Raise the memory or timeout, or move long work to a background trigger.

Checked against the vendor’s docs on November 9, 2026: Firebase docs: Call functions from your app; Firebase docs: Cloud Functions locations.

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