Managed Agents in the Gemini API now default to Gemini 3.6 Flash, as announced in a Jul 28, 2026 blog post by Google DeepMind staff. New environment hooks allow users to run custom scripts before or after every tool call inside the sandbox, enabling actions like blocking, linting, or auditing tool calls via a `.agents/hooks.json` configuration file. The update also includes budget controls, scheduled triggers, and free tier access. The antigravity-preview-05-2026 agent automatically uses Gemini 3.6 Flash without code changes, and users can explicitly select models including Gemini 3.6 Flash, Gemini 3.5 Flash, and Gemini 3.5 Flash-Lite.