Headless Chat SDK Agent Pack

The agent pack makes the SDK discoverable to Claude Code, Codex, and Antigravity — tri-agent parity is a first-class goal.

Installing into a downstream app

# Install for every detected agent
gecx agent-pack init --all --out .

# Or target one agent
gecx agent-pack init --target claude-code --out .
gecx agent-pack init --target codex --out .
gecx agent-pack init --target antigravity --out .

# Or just register the MCP server
gecx agent-pack init --mcp --out .

Then ask an agent to use the installed skill:

Use .agents/skills/headless-chat-vibe-coding to build a branded Headless Chat SDK support concierge.
Start mock-first, render message.parts with part.id keys, define tools with JSON Schema and ctx.signal, and add a mock test.

What gets installed

The canonical skill source is skills/headless-chat-vibe-coding/. pnpm install keeps these directories in sync — the agent-pack CLI is the downstream equivalent.

• AGENTS.md — shared rules. Codex reads this natively; Claude Code and Antigravity follow the same convention.
• CLAUDE.md — Claude Code entrypoint, pointing at .claude/skills/.
• GEMINI.md — Google Antigravity entrypoint, pointing at .agent/skills/.
• .claude/skills/headless-chat-vibe-coding/ — for Claude Code.
• .agents/skills/headless-chat-vibe-coding/ — for Codex.
• .agent/skills/headless-chat-vibe-coding/ — for Antigravity.
• Scaffold command examples.
• Safety review prompt.

When --mcp is included, the pack also writes the MCP server config in the right format for each detected agent: .mcp.json (Claude Code), .codex/config.toml (Codex), or mcp_servers.json (Antigravity). The merge is non-destructive.

MCP server v1

pnpm dlx gecx-chat-mcp-server --install

The MCP server exposes 14 tools, 12 resource templates, and 14 prompts (10 general + 4 commerce — add-cart-renderer, add-checkout-flow, add-returns-flow, redact-pci-fields). Once installed, prompts like "use the gecx-chat MCP to add a new client tool" work without further setup. See packages/gecx-chat-mcp-server/ for the source.

Walkthrough artifact protocol

The pack supports the cross-agent walkthrough protocol:

gecx walkthrough capture --task=<task-id>
gecx walkthrough verify <manifest-path>

This produces a PNG + manifest pair conforming to schemas/walkthrough.schema.json. Use it when you want an agent to prove a flow before merging. The stub driver works offline; the Playwright driver hook is ready for real browser captures.