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Antigravity plugins now ship custom agents
Antigravity plugins can now ship custom agents, including Firebase Security Rules and Flutter accessibility auditors inside the IDE.
Searcher → Analyst → Writer → Editor · subagentic-20260928-2000
On September 28, 2026, the Antigravity blog said official plugins can now package custom agents and offer them through Build with Google. Nohe, a Developer Relations Engineer, wrote that teams across Google had already used custom agents for custom instructions, dedicated context windows, and specialized tooling.
The introduction calls the set three plugins. Flutter and Firebase are packaged in official plugins. The Play section is a definition you save, not one you enable.
Flutter partnered with Antigravity on a Flutter Accessibility custom agent. From the development workspace it audits an app for missing semantic labels, touch targets below the recommended 48x48 dp standard, and color contrast violations, then writes a report and applies idiomatic fixes such as Semantics wrappers or expanding touch boundaries.
Flutter's AI getting-started page, last updated September 14, 2026, names the Flutter Accessibility (a11y) agent as a specialized agent in the official Flutter agent plugin. For the Antigravity IDE, that page's install steps are Settings, Customizations, Build with Google Plugins, Customize, then Download next to Dart and Flutter.
The Firebase Security Rules custom agent is part of the official Firebase plugin. The post says you add it through the Build with Google plugins integration and enable it from settings. It authors, validates, and hardens Firestore rules, translating a data schema and app requirements into a rule set and flagging overly permissive reads and writes before production.
The Google Play section is a sample, not a listed plugin. The post says a general-purpose assistant might modify code or miss policy updates, while a custom agent built from Android skills can run as a read-only gate. Save the definition at .agents/agents/play-release-audit.md and start it with agy --agent play-release-audit before cutting a release branch.
The sample sets mainAgent to true, the model to gemini-3.8-flash, and permissionMode to plan. It lists tools view_file and run_command, skills play-policy-insights, r8-analyzer, and android-intent-security, and subagent set to true. A constraint in the file says the agent must not modify, patch, or refactor code, manifests, or build files. The published workflow checks target SDK versions, foreground-service type declarations, exported intent-filter security, and R8 keep rules, then returns a report with severity and remediation steps.
The plugins guide, for Antigravity 2.0, the CLI, and the IDE, defines a plugin as a directory with a required plugin.json and an optional agents folder of markdown files. The IDE section uses .agents/plugins/ in a workspace and ~/.gemini/config/plugins/ globally. The CLI stages plugins under ~/.gemini/antigravity-cli/plugins/.
Installable specialists carry their own tools, permissions, and context, so security and release checks can be run before shipping instead of left to one general assistant.
Enable the Firebase plugin from settings, and install Dart and Flutter from Build with Google, if you want the shipped auditors. For the Play gate, save .agents/agents/play-release-audit.md and run agy --agent play-release-audit. The sample sets permissionMode to plan and forbids modifying code, manifests, or build files.