hermes-google-antigravity-plugin

Native Google Antigravity (Cloud Code PA) provider for the Hermes Agent — a first-class oauth_external provider you sign into with your Google account (subscription-style), exactly like the other OAuth providers (hermes auth add, hermes model, hermes chat). No API key, no dummy token: the access token lives in an auto-refreshed OAuth file.

Models are served through the cloudcode-pa.googleapis.com/v1internal:generateContent API and exposed to Hermes as OpenAI-style chat.completions via a thin shim, so Gemini / Claude / GPT-OSS models routed through Antigravity behave like any other Hermes model (tool calls, thinking, multi-turn).

Layout

agent/
  antigravity_native_adapter.py     # OpenAI chat.completions shim over the cloudcode-pa client
  antigravity_oauth.py              # OAuth login (PKCE) + runtime token resolution (auto-refresh)
  antigravity_cloudcode.py          # vendored Cloud Code PA client (generateContent, refresh, model aliases)
  antigravity_cloudcode_config.py   # settings/paths for the vendored client
patches/
  hermes-agent-antigravity-core.patch   # integration patch (9 Hermes core files)
plugins/model-providers/google-antigravity/
  __init__.py                       # ProviderProfile(name="google-antigravity", auth_type="oauth_external")
  plugin.yaml                       # plugin manifest
  login.py                          # standalone login helper

How it integrates (the core patch)

patches/hermes-agent-antigravity-core.patch touches 9 files:

File	What it adds
hermes_cli/runtime_provider.py	google-antigravity short-circuit (Vertex-style): resolves the OAuth token → cloudcode-pa base URL, never falls through to OpenRouter
agent/auxiliary_client.py	matching branch in resolve_provider_client for auxiliary tasks
agent/agent_runtime_helpers.py	create_openai_client hook — is_antigravity_base_url → instantiates the native shim
hermes_cli/auth.py	PROVIDER_REGISTRY["google-antigravity"] = oauth_external
hermes_cli/providers.py	HERMES_OVERLAYS entry (oauth_external, cloudcode-pa)
hermes_cli/auth_commands.py	hermes auth add google-antigravity → Google login + pooled credential
hermes_cli/main.py	hermes model dispatch to the antigravity flow
hermes_cli/model_setup_flows.py	_model_flow_google_antigravity (login + model picker)
hermes_cli/models.py	provider entry + curated model list

The shim reads/refreshes the OAuth file itself, so the api_key Hermes routes is only used to satisfy routing — the real auth is always the live Google token.

Install

Recommended: via the recovery system

Deploy through hermes-patch-manager as a mod (source-patch + new-file components). It re-applies the patch and re-copies the modules automatically after hermes update (which does a git reset + venv rebuild), with an LLM-assisted merge tier for upstream drift.

Manual

AGENT=~/.hermes/hermes-agent
# 1) new modules
cp agent/antigravity_*.py "$AGENT/agent/"
# 2) core integration patch
git -C "$AGENT" apply patches/hermes-agent-antigravity-core.patch
# 3) plugin (survives hermes update — lives outside the repo)
mkdir -p ~/.hermes/plugins/model-providers/google-antigravity
cp plugins/model-providers/google-antigravity/* ~/.hermes/plugins/model-providers/google-antigravity/
# 4) restart the gateway so the re-applied source is loaded

Usage

hermes auth add google-antigravity     # Google account OAuth login
hermes model                           # pick "Google Antigravity" + a model
hermes chat --provider google-antigravity --model gemini-3.5-flash-high

Available models (curated): gemini-3.1-pro-high/low, gemini-3.5-flash-high/medium/low, gemini-3-flash-high/low, claude-opus-4-6-thinking, claude-sonnet-4-6-thinking, gpt-oss-120b.

Image generation

Also ships an image_gen backend plugin (plugins/image_gen/google-antigravity/) exposing Antigravity's Gemini image models (Nano Banana family) over the same OAuth session. It delegates to the vendored client's generate_image() and lists models live from the backend (fetch_available_image_models), with a curated fallback when the live catalog is unavailable.

Enable + activate in ~/.hermes/config.yaml:

plugins:
  enabled:
    - image_gen/google-antigravity
image_gen:
  provider: google-antigravity
  model: gemini-3.1-flash-image

Models: gemini-3-pro-image (Nano Banana Pro), gemini-3.1-flash-image (Nano Banana), gemini-2.5-flash-image.

Web search (Google grounding)

Also ships a web_search backend plugin (plugins/web/google_grounding/) that answers queries with Google Search grounding through Antigravity's gemini-3.5-flash-high — cited, current sources, no API key. It calls the vendored client's grounded_search() (which adds tools=[{"google_search": {}}] to the generateContent request) and maps the response's groundingChunks to Hermes search results.

Enable + activate in ~/.hermes/config.yaml:

plugins:
  enabled:
    - web/google_grounding
web:
  search_backend: google_grounding

Search-only (cited source URLs + snippets); page-content extraction stays on your configured web.extract_backend.

Login notes

run_antigravity_login() uses the PKCE authorization-code flow (the device-code flow is rejected by the Antigravity client as invalid_client). It runs a local callback server on 127.0.0.1:51121 and reads a pasted callback URL/code from stdin concurrently — whichever arrives first wins:

• Local machine / SSH tunnel (ssh -L 51121:localhost:51121 <host>): the browser redirect is captured automatically.
• Headless remote, no tunnel: the redirect page fails to load — just copy the full redirected URL (or the code= value) and paste it into the terminal.

Token expiry is stored in milliseconds to match the vendored client, so a fresh login is not seen as instantly expired.

Note

This replaces an earlier gRPC/quota-oriented implementation. That approach was incompatible with current Hermes; its files remain in git history. The vendored Cloud Code client is adapted from Meapri/Antigravity-Proxy.