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[Bug]: Antigravity Agent Platform shows "authenticated" without Google Cloud credentials; first turn fails with raw ADC error #23036
Description
Before submitting
- I searched existing issues and did not find a duplicate.
- I included enough detail to reproduce or investigate the problem.
Area
apps/server
Steps to reproduce
- On a machine with no Application Default Credentials (no
~/.config/gcloud/application_default_credentials.json,gcloudnot installed, noGOOGLE_APPLICATION_CREDENTIALS). - In Settings > Providers > Antigravity, set Sign-in method to "Agent Platform (Vertex AI)", fill in GCP project and location, leave API key empty.
- Wait for the provider status check.
- Start an Antigravity thread and send any message.
Expected behavior
Agent Platform should be usable from the settings panel alone, like the other Antigravity sign-in methods: a browser sign-in (or similar) that leaves the provider ready to work, without installing the Google Cloud SDK or running terminal commands. The standalone agy CLI already runs in Agent Platform mode without ADC on this machine, so a credential-free path seems to exist on Google's side.
At minimum, if ADC is required, the provider status should say so before a thread starts (for example "No Google Cloud credentials found. Run gcloud auth application-default login."), instead of showing authenticated.
Actual behavior
The provider status shows ready / authenticated with the label "Agent Platform", and the model list loads. The first turn then fails with the raw runtime error:
Agent execution error: failed to create Gemini client: failed to configure default GCP credentials for Vertex AI: failed to find default credentials: credentials: could not find default credentials. See https://cloud.google.com/docs/authentication/external/set-up-adc for more information
Nothing in the settings UI mentions that Agent Platform without an API key needs ADC, so the only hint is the error on the first message.
Impact
Major degradation or frequent failure
Version or commit
T3 Code (Beta) 0.1.1, managed Antigravity ACP runtime 1.3.0
Environment
macOS 27.0.1 (arm64), desktop app, Antigravity provider with authMethod: "agent-platform"
Workaround
Install the Google Cloud SDK and run gcloud auth application-default login. After that, turns succeed.
Related: #16078 (unverified account passes the sign-in check, then the first turn fails with a raw 403) and #12751 (misleading Antigravity auth status) show the same pattern for other sign-in methods.
Activity
juliusmarminge commentedon Nov 14, 2026
I tried to reproduce this on the current build and could not.
Commit origin/main 4c47315, Linux VM with no ~/.config/gcloud/application_default_credentials.json, no GOOGLE_APPLICATION_CREDENTIALS, no gcloud, no metadata server. Ran
T3CODE_DEV_SEED=0 vp run dev, paired the web client, Settings > Providers > Add provider > Antigravity, Sign-in method 'Agent Platform (Vertex AI)', GCP project example-project, location us-central1, no API key; saved config = {authMethod: agent-platform, gcpProject, gcpLocation}. Installed the managed runtime from Settings (v1.5.9). Status: 'Needs attention · Antigravity is installed. Connect with Agent Platform to load models.', 0 models. Clicked Connect: Account row shows 'Antigravity could not authenticate with the configured credentials.' and status stays Needs attention; server log shows the runtime's AcpRequestError 'Couldn't sign in: failed to load Application Default Credentials: google: could not find default credentials ... configure GEMINI_API_KEY or Application Default Credentials, then try again.' The provider never reaches Authenticated and loads no models, so no Antigravity thread can be started and the first-turn ADC failure cannot be reached. The reporter used runtime 1.3.0; main now installs only managed runtimes >=1.5.0 (#35409, compatibility ranges from #13130), and those check credentials at sign-in. Matches the maintainer's own no-repro on #24957 (closed 2026-11-14).Closing as not planned. If it still happens for you, reply with the exact steps and the version you are on and it will be looked at again.