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Summary

• Add Google Antigravity browser OAuth under /connect, using a generated Google authorization URL followed by a pasted full localhost callback URL.
• Show open/copy-link controls, callback input, inline validation errors, submission state, and explicit cancellation. Keep the API-key option available and retain internal provider ID google for config/credential compatibility.
• Validate callback origin/path/state, use PKCE, exchange and persist credentials, discover/onboard a managed project, and refresh credentials before outbound generations (including subagents).
• Add the Antigravity Gemini transport with streaming text/reasoning/tool calls, image inputs, usage/finish handling, bounded stream reads, cancellation, and persisted thought-signature replay across tool loops and later turns.
• Rename provider display labels to Google Antigravity, including old cached catalog/snapshot views, and expose OAuth-compatible Gemini model IDs using existing catalog metadata.
• Add terminal ACP login support and document the flow and unofficial-service/account-eligibility caveat.

OAuth client configuration

No Google OAuth client ID or secret is bundled, persisted in config, or compiled into the binary. Set CRABCODE_ANTIGRAVITY_CLIENT_ID and CRABCODE_ANTIGRAVITY_CLIENT_SECRET in the runtime environment. The OAuth client must be authorized for the requested Google scopes/service and use http://localhost:51121/oauth-callback as its redirect URI. An arbitrary new Google Cloud OAuth client does not guarantee Antigravity access. Existing refresh tokens remain bound to their original client.

Missing/invalid settings fail with setup instructions without echoing values. Unit tests inject fake clients and do not mutate global environment variables.

Validation

• 1,896 unit tests and 7 ACP integration tests passed (3 pre-existing ignored tests).

• cargo test --offline -- --test-threads=1

• cargo build --offline --bin crabcode

• cargo fmt --all -- --check

• bash scripts/check-aisdk-boundary.sh

• git diff --check

OAuth, refresh, project onboarding, HTTP/SSE, signed-history, dialog, and cancellation tests use local fixtures; no Google token exchange or account authorization was performed during development. Live Google/Antigravity account eligibility and service availability still require a manual smoke test.

Two existing test fixtures were made environment-independent while running the suite: the edit-rendering fixture now uses the current checkout path, and the ACP stdio fixture explicitly avoids live Ollama discovery.

Manual smoke test

1. Run /connect → Google Antigravity → Gemini via Antigravity (browser).
2. Open/copy the generated authorization link and authorize an eligible Google account.
3. Copy the full http://localhost:51121/oauth-callback?... URL from the address bar even if the localhost page cannot load.
4. Paste into the callback input and submit; confirm Gemini models are selectable and a text/tool turn works.
5. Confirm invalid state is rejected inline and Esc cancels without saving credentials.

This integration uses an unofficial Antigravity transport; Google account eligibility, service terms, and restrictions apply.