AQ. auth key returns 401 ACCESS_TOKEN_TYPE_UNSUPPORTED on Generative Language API — standard AIza keys on same account still work

Gemini API
1 
Hi Googlers,

Reporting another case of the AQ.-format auth key rollout bug affecting the Generative Language API.

**Context**
- Account: free tier, Google AI Studio
- Project: "Agente Autonomo" (number 10509899345..), created fresh in AI Studio
- Key: created in AI Studio on Sep 23, 2026, minted in the new AQ. format (starts `AQ.Ab8RN6...`)
- Model: gemini-3.6-flash

**Exact error (verbatim)**
```json
{
  "error": {
    "code": 401,
    "message": "Request had invalid authentication credentials. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.",
    "status": "UNAUTHENTICATED",
    "details": [
      {
        "@type": "type.googleapis.com/google.rpc.ErrorInfo",
        "reason": "ACCESS_TOKEN_TYPE_UNSUPPORTED",
        "metadata": {
          "service": "generativelanguage.googleapis.com",
          "method": "google.ai.generativelanguage.v1beta.GenerativeService.GenerateContent"
        }
      }
    ]
  }
}
```

**Everything I tried — all return the identical 401:**
1. `x-goog-api-key` header on `POST /v1beta/models/gemini-3.6-flash:generateContent`
2. `?key=` query parameter
3. `Authorization: Bearer` header
4. `v1` endpoint instead of `v1beta`
5. `GET /v1beta/models` (model listing)
6. The new Interactions API (`google.learning.gemini.api.interactions.v1beta.InteractionsService.CreateInteractionHttp`) — same 401, same reason `ACCESS_TOKEN_TYPE_UNSUPPORTED`

**Repro curl (key redacted):**
```bash
curl -s -X POST "https://generativelanguage.googleapis.com/v1beta/models/gemini-3.6-flash:generateContent" \
  -H "x-goog-api-key: AQ.Ab8RXXXXXXX" \
  -H "Content-Type: application/json" \
  -d '{"contents":[{"parts":[{"text":"Reply only: OK"}]}]}'
```

**Key data point — same account, standard keys work:**
On the same Google account, two standard (AIzaSy...) keys created on Apr 26, 2026 in an older project authenticate fine against `generateContent` with `gemini-3.6-flash` and the `x-goog-api-key` header (tested minutes apart from the failing AQ. key). So the rejection is isolated to the AQ.-format key / new project, not the account, network, or request syntax.

Given the September 2026 standard-key deprecation deadline, accounts landing on AQ.-only keys with this bug currently have no working auth path to the Gemini API.

**Ask:** please un-flag / fix the project so AQ. keys authenticate against generativelanguage.googleapis.com, or confirm the working auth method for an AQ. auth key.

Happy to provide any console screenshot needed. Thank you!
2

Hello @Marco_Visentin , please try deleting all old, non-working API keys and then create a new key directly within the Google AI Studio UI specifically. If you continue to encounter the 401 error with the new key, could you please share the exact cURL command triggering the error (with your API key redacted) so we can investigate this further?