How can I resolve the 400 Bad Request error on Firebase Firestore Write channel?

Below is a list of potential causes and troubleshooting steps you might follow:

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Possible Causes

• Client/Server Mismatch
  Although your Firebase configuration and security rules appear correct, a mismatch in credentials or an expired/invalid authentication token can cause the Write channel to reject the request. Even though you’re seeing valid tokens, it’s possible that an underlying client issue (or cookie/cache issue) is leading to an improper credential payload on the WebChannel.

• WebChannel or Browser-Specific Issues
  The Write channel uses a streaming WebChannel connection (initiated via GET) which automatically reconnects. If Chrome (or your environment) has experimental flags, ad blockers, or caching issues, these could interfere with the connection handshake.

• Network/Origin Mismatch
  Note the origin is reported as http://localhost:3000. Confirm that the project’s settings (such as allowed domains for authentication) match your local and production origins. Although your production environment works with the proper configuration, cached metadata or inconsistent origin resolution might cause issues.

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Troubleshooting Steps

1. Double-Check Client Authentication

   • Ensure that the Firebase SDK is obtaining a fresh and valid authentication token.
   • Confirm that the token’s project and sender information align with your Firestore settings.

2. Verify SDK and Browser Versions

   • Make sure you’re using an up-to-date Firebase client SDK.
   • Test using a different browser or incognito mode to rule out cache, extension, or browser-specific issues.

3. Review Network and Origin Settings

   • Verify that requests from http://localhost:3000 meet the same CORS and Firebase Console domain whitelist requirements as your production origin.
   • If your app uses any custom headers or proxies, ensure these are not altering the expected request parameters.

4. Investigate WebChannel Behavior

   • Although the GET request to the Write channel is part of the normal WebChannel establishment process, repeated failures may indicate that the initial handshake elements (such as gsessionid) are invalid.
   • Look for any client-side errors immediately on initialization that might hint at a token refresh or connection timing issue.

5. Clear Cache and Disable Interfering Extensions

   • Clear the browser cache and try again.
   • Temporarily disable browser extensions (such as ad blockers) that might interfere with web requests.

6. Check for Firebase SDK Bugs

   • Visit the Firebase SDK release notes and support channels to see if similar WebChannel transport issues have been reported with your version of Chrome or the Firebase SDK.

7. Contact Firebase Support if Needed

   • If you continue encountering multiple 400 errors on the Write channel after the above steps, consider contacting Firebase Support. Include your project number, app identifier, and a summary of your troubleshooting steps.

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Example Logging

Adding extra error logging might help pinpoint the issue. For example:

JAVASCRIPTCopied
try {
  await addDoc(collection(db, 'community'), {
    title: data.title,
    content: data.content,
    authorId: currentUser.uid,
    // ... any additional fields
  });
} catch (error) {
  console.error('Error writing document:', error);
  // Optionally log error.code or error.details if available
}

This can help you determine if the error is surfaced as a Firebase Firestore exception with additional details (such as UNAUTHENTICATED or INVALID_ARGUMENT).

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Summary

Even though your configuration appears correct, WebChannel transport errors (400 Bad Request) when writing indicate that the underlying handshake (including authentication and valid session identifiers) is failing. Work through the above troubleshooting steps to rule out token, SDK, browser, and network issues. If the error persists, reaching out to Firebase Support is recommended for further investigation.