Antigravity Agent 09-2026 replaces 05-2026 with new built-in file and search tools

Google released the antigravity-preview-09-2026 agent, which replaces and deprecates antigravity-preview-05-2026.

Remote sandbox users reading only output_text or model_output steps need only update the agent string, while local-environment users or those parsing function_call steps must adapt to renamed tools, PascalCase parameters, and line-range file edits.

The 05-2026 preview shuts down on October 5, 2026.