Support Antigravity SDK as a first-class agent implementation framework

Start by reviewing the existing --agent template identifiers and the create, run, eval, deploy, and publish entry points described in the issue. Define the smallest supported Antigravity SDK integration, then verify that its template, manifest, lifecycle behavior, deployment target, and evaluation boundary are documented and tested.

What is your feature suggestion?

lease add first-class support for agents implemented with the Google Antigravity SDK for Python (google-antigravity) in agents-cli.

Today, agents-cli already works well as a lifecycle toolchain for Google Cloud agent development, and it already documents support for Antigravity as a coding assistant that can use the CLI. This feature request is about a different layer: using Antigravity SDK as the framework/runtime for the agent being created, run, evaluated, deployed, and published by agents-cli.

A useful first version could be an Antigravity SDK project template:

agents-cli create my-antigravity-agent --agent antigravity-sdk-python

The generated project should include a minimal runnable Antigravity SDK agent and the surrounding agents-cli project structure needed for local development, deployment, evaluation, and documentation.

Desired capabilities, ideally delivered incrementally:

1. Built-in Antigravity SDK template

   • Add an antigravity-sdk-python template alongside the existing agent templates.
   • Generate a minimal but production-shaped Python project using google-antigravity.
   • Include a runnable Agent / LocalAgentConfig example.
   • Include examples for a custom Python tool and an optional MCP server configuration.

2. Manifest support

   • Allow agents-cli-manifest.yaml to identify the agent framework as Antigravity SDK.
   • Capture the Antigravity agent entrypoint, runtime/deployment target, environment variables, and supported lifecycle commands.

3. Local run and playground support

   • Support running the generated Antigravity SDK agent locally through agents-cli run or document the supported local runner contract.
   • Support local development with either a Gemini API key or Vertex / Gemini Enterprise Agent Platform configuration where applicable.

4. Evaluation support

   • Support agents-cli eval for Antigravity SDK agents directly, or document an adapter interface that normalizes Antigravity SDK responses into the existing agents-cli evaluation format.
   • If Antigravity SDK exposes streaming steps, tool calls, or traces, document how much of that information can be collected for evaluation.

5. Deployment and publishing guidance

   • Document and test at least one supported deployment target, such as Cloud Run, Agent Runtime, or GKE.
   • Clarify whether Antigravity SDK agents can be published to Gemini Enterprise Agent Platform through agents-cli publish gemini-enterprise.
   • Provide safe defaults for service accounts, environment variables, secrets, ADC, and MCP configuration.

6. Safety and governance examples

   • Include examples for Antigravity SDK hooks or policies, such as read-only tools, deny-by-default tool policy, or explicit approval before risky tool execution.
   • Document recommended defaults for enterprise projects that use SaaS, public-cloud, or MCP tools.

What will this enable you to do?

This would allow teams to use agents-cli as the standard Google Cloud lifecycle toolchain while choosing Antigravity SDK as the agent implementation framework.

Example workflows this would enable:

agents-cli create incident-triage-agent --agent antigravity --deployment-target cloud_run
agents-cli run "Summarize this incident and propose next actions"
agents-cli eval run
agents-cli deploy
agents-cli publish gemini-enterprise

More specifically, this would enable developers to:

1. Build Antigravity SDK agents with production scaffolding

   • Start from a supported project layout instead of hand-rolling the integration.
   • Use the same agents-cli lifecycle conventions as other Google Cloud agent projects.

2. Use Antigravity SDK capabilities in enterprise agents

   • Implement agents with Antigravity SDK primitives.
   • Use stateful conversations and streaming responses.
   • Register custom Python tools.
   • Integrate MCP servers as tool providers.
   • Apply hooks and policies for safer tool execution.
   • Configure local Gemini API key development and Google Cloud / Vertex / Gemini Enterprise modes where supported.

3. Reduce framework fragmentation

   • Avoid forcing teams to choose between ADK-oriented agents-cli lifecycle support and Antigravity SDK-specific agent capabilities.
   • Make it clear when to choose ADK, Antigravity SDK, or another framework for a given agent project.

4. Improve enterprise governance

   • Give platform teams a consistent way to scaffold, evaluate, deploy, and review Antigravity SDK agents.
   • Encourage safer defaults around credentials, service accounts, MCP tools, and production deployment.

5. Support phased adoption

   • Teams could begin with a supported Antigravity SDK template and later adopt deeper agents-cli integration as run/eval/deploy/publish support matures.

Additional context

I think this is worthwhile because agents-cli is positioned as the lifecycle CLI for building, evaluating, deploying, publishing, governing, and optimizing agents on Google Cloud, while Antigravity SDK is a Google Python SDK for building agents powered by Antigravity and Gemini. Developers may reasonably expect these two Google agent-development surfaces to work together not only at the coding-assistant layer, but also at the agent-implementation-framework layer.

Current context that motivated this request:

• agents-cli already documents support for Antigravity as a coding assistant that can use the CLI.
• The currently documented built-in templates appear to be ADK-oriented, such as adk, adk_a2a, and agentic_rag.
• agents-cli create --agent already supports template identifiers, local paths, ADK sample shortcuts, and remote Git URLs, which suggests a low-risk incremental path: start with a documented remote Antigravity SDK starter template, then promote it to a first-class built-in template if it proves useful.
• Antigravity SDK has its own agent API/runtime surface, including agent configuration, conversations, streaming, custom tools, MCP integration, hooks/policies, triggers, and Google Cloud / Vertex / Gemini Enterprise configuration.