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.

Availability

Development builds enable negotiated modes before session creation and upgrade the managed ACP server to 1.3.0. These changes are not yet a stable-release guarantee; authenticated composer, context-usage and account-switch validation is still in progress.

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. With native authentication selected, 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

Development builds background-install the official pinned agy_acp_server v1.3.0 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. An older managed version is also replaced through that ensure path. Explicitly configured executable overrides keep their own negotiated capabilities.

Linux launches add the required --uid= platform arg. Platforms without a published archive fail clearly instead of being emulated. The 1.3.0 pin includes Intel Mac; earlier releases using 1.1.1 do not gain that asset or context telemetry automatically.

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.

In development builds, choose the machine and project in the new-session composer to discover the available modes before launch. The chosen starting mode is applied before the first prompt. Discovery needs an authenticated ACP server; signed-out discovery does not invent model or mode choices. With machine-local authentication, these discovery sessions can leave empty conversations in Antigravity's history.

The official 1.3.0 server restricts Happier's model catalog to Gemini models. Happier keeps its own client identity and displays the models the server returns. When the server reports context usage after a turn, Happier uses those counts for its existing context indicator. Older executable overrides may not report that telemetry.

Permissions

Happier sends no static permission-mode override for Antigravity and preserves your agent configuration unless you choose otherwise in the session. The mode picker uses the server's advertised modes. Antigravity's /plan slash command does not establish an ACP Plan mode, so a legacy plan permission cannot create that missing option.

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.