Antigravity CLI (experimental)

Happier runs Antigravity through the official pinned agy_acp_server ACP transport for normal sessions and execution runs. The interactive agy CLI stays a separate system-first terminal surface, with its own login and session IDs.

Requirements and authentication

Install the interactive Antigravity CLI using the official Antigravity CLI guide, and make sure agy is available on PATH for local terminal control. Happier sessions need a separate login to the ACP server. In development builds with the ACP login command, run this on the machine where Happier runs:

happier agy auth login

Follow the Google login link printed in the terminal. Wait for the command to confirm completion before starting a session. The ACP server stores its own credentials and authentication choice; logging into the interactive agy CLI does not sign it in. Subsequent Happier sessions use that saved choice without opening the login command again.

You can also open this ACP login flow from Settings → AI & Agents → AI backends → Antigravity. Happier does not probe Antigravity authentication in the background, so the app may continue to show Unknown after login.

For another authentication method, pass --method oauth-business, --method gemini-api-key, or --method agent-platform. Configure the chosen method's environment and ACP settings on the same machine; API keys are read by the ACP server from its environment, not from command-line arguments. Use the same GEMINI_HOME for login and the daemon if you override it.

When the browser runs on a different computer, keep the login command running and forward the port from the login URL's redirect_uri to the agent machine. For example, for port 12345, run ssh -N -L 12345:127.0.0.1:12345 user@agent-host on the browser computer before opening the link. The server chooses the port for each login attempt. Press Ctrl+C to cancel login.

Pinned ACP server install

Happier background-installs the official pinned agy_acp_server v1.1.1 platform archive when you select Antigravity, and launch reuses that same install instead of downloading twice. Integrity is verified by SHA-256 on every download, extraction reuses the shared archive helpers, and the executable bit is set on Unix. A corrupt or missing artifact fails visibly, and the next launch re-runs the authoritative ensure to recover.

Linux launches add the required --uid= platform arg. Platforms without a published v1.1.1 archive fail clearly instead of being emulated.

Start and resume sessions

happier agy

Happier supports new sessions, vendor resume, follow-up messages, cancellation, live model changes through the agent-advertised ACP model config option, and execution runs. Models, modes, and MCP tools come from negotiated agent state rather than a static list.

Permissions

Happier sends no static permission-mode override for Antigravity and preserves your agent configuration unless you choose otherwise in the session.

MCP tools

Happier passes its MCP server list through the standard ACP session request for Antigravity sessions. For shared MCP setup and session selection, see MCP servers.

Troubleshooting

• Run agy --version on the agent machine to confirm the interactive CLI is installed.
• For Authentication required, run happier agy auth login on that machine and wait for successful completion. An interactive CLI login alone does not authenticate ACP.
• If the ACP server is missing, reselect Antigravity in the app and watch the install progress, then retry launch.
• If a model is unavailable, retry after the ACP handshake completes; the model list is provider-advertised.

Related

• Agent capabilities — compare Antigravity's current session, model, media, and tool support.
• Provider authentication — how Happier presents provider-owned login flows.
• Subagents and execution runs — run Antigravity in Happier-managed non-interactive workflows.