Heads-up: Setting GOOGLE_CLOUD_PROJECT to a numeric project number causes 400 INVALID_ARGUMENT on all requests

[EvilDjango]

Type: Configuration tip / Q&A
Not a bug — sharing this for anyone who hits the same confusing error.

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Environment

• CLI version: 0.32.1
• Auth method: oauth-personal
• OS: macOS

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Symptom

Every request returns 400 INVALID_ARGUMENT immediately, regardless of the prompt content:

✖  Error when talking to Gemini API
GaxiosError: [{
  "error": {
    "code": 400,
    "message": "Request contains an invalid argument.",
    "status": "INVALID_ARGUMENT"
  }
}]

The routing classifier also fails before the main request:

⚠  [Routing] NumericalClassifierStrategy failed: Error: Failed to generate content: Request contains an invalid argument.

None of the usual remedies worked: downgrading/upgrading CLI, deleting ~/.gemini/ and re-authenticating, changing model settings.

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Root Cause

The environment variable GOOGLE_CLOUD_PROJECT was set to the GCP project number (numeric, e.g. 623157363865) instead of the project ID (string, e.g. bustling-bay-464713-h7).

In setup.js, the CLI reads this env var first:

const projectId = process.env['GOOGLE_CLOUD_PROJECT'] ||
    process.env['GOOGLE_CLOUD_PROJECT_ID'] ||
    undefined;

If the env var is set to the numeric project number, that value gets passed as the "project" field in all content generation requests to the Code Assist API. The API does not accept numeric project numbers in this field and rejects the request with a generic 400 error — without any indication of which parameter is wrong or why.

In Google Cloud, these are two distinct identifiers for the same project:

Field	Example
Project Number	623157363865 (numeric)
Project ID	bustling-bay-464713-h7 (string)

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Fix

Option A (recommended): Unset GOOGLE_CLOUD_PROJECT entirely if you're using a personal OAuth account. The CLI will resolve the correct project automatically via the Code Assist API.

unset GOOGLE_CLOUD_PROJECT
gemini -p "hello"

Option B: If you need the env var set (e.g. for other GCP tools), make sure it points to the string project ID, not the project number.

export GOOGLE_CLOUD_PROJECT=your-project-id   # e.g. bustling-bay-464713-h7

Find your project ID in Google Cloud Console — it's the hyphenated string under "Project ID", distinct from the numeric "Project Number".

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Minor Complaint (not a bug, but worth noting)

The error message Request contains an invalid argument. gives no hint about which argument is invalid or why. A more targeted message — or even a startup warning when GOOGLE_CLOUD_PROJECT is set to a numeric-only value — would have saved a lot of debugging time. Worth considering for a future improvement.

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Related Issues

• Request contains an invalid argument #18903 — Generic API Error 400 on all requests
• API Error (400): Request contains an invalid argument #13755 — API Error (400): Request contains an invalid argument
• Error 400 INVALID ARGUMENTS after resuming a conversation from API to oauth #3273 — Error 400 INVALID ARGUMENTS after resuming a conversation

[aniruddhaadak80]

From my point of view, this is a very useful finding because the current failure mode is too generic for something that is really just a configuration mismatch. A startup validation that warns when GOOGLE_CLOUD_PROJECT is numeric only would probably save a lot of wasted debugging time. Even a short hint in the error path would make this much easier to diagnose.