Antigravity Setup and Usage Guide

Google's Antigravity is an AI coding IDE that uses a .agent/ directory convention for configuration. ECC provides first-class support for Antigravity through its selective install system.

Quick Start

# Install ECC with Antigravity target
./install.sh --target antigravity typescript

# Or with multiple language modules
./install.sh --target antigravity typescript python go

This installs ECC components into your project's .agent/ directory, ready for Antigravity to pick up.

How the Install Mapping Works

ECC remaps its component structure to match Antigravity's expected layout:

Note on .agents/ vs .agent/ vs agents/: The installer only handles three source paths explicitly: rules → .agent/rules/, commands → .agent/workflows/, and agents (no dot prefix) → .agent/skills/. The dot-prefixed .agents/ directory in the ECC repo is a static layout for Codex/Antigravity skill definitions and openai.yaml configs — it is not directly mapped by the installer. Any .agents/ path falls through to the default scaffold operation. If you want .agents/skills/ content available in the Antigravity runtime, you must manually copy it to .agent/skills/.

Key Differences from Claude Code

• Rules are flattened: Claude Code nests rules under subdirectories (rules/common/, rules/typescript/). Antigravity expects a flat rules/ directory — the installer handles this automatically.
• Commands become workflows: ECC's /command files land in .agent/workflows/, which is Antigravity's equivalent of slash commands.
• Agents become skills: ECC agent definitions map to .agent/skills/, where Antigravity looks for skill configurations.

Directory Structure After Install

your-project/
├── .agent/
│   ├── rules/
│   │   ├── coding-standards.md
│   │   ├── testing.md
│   │   ├── security.md
│   │   └── typescript.md          # language-specific rules
│   ├── workflows/
│   │   ├── plan.md
│   │   ├── code-review.md
│   │   ├── tdd.md
│   │   └── ...
│   ├── skills/
│   │   ├── planner.md
│   │   ├── code-reviewer.md
│   │   ├── tdd-guide.md
│   │   └── ...
│   └── ecc-install-state.json     # tracks what ECC installed

The openai.yaml Agent Config

Each skill directory under .agents/skills/ contains an agents/openai.yaml file at the path .agents/skills/<skill-name>/agents/openai.yaml that configures the skill for Antigravity:

interface:
  display_name: "API Design"
  short_description: "REST API design patterns and best practices"
  brand_color: "#F97316"
  default_prompt: "Design REST API: resources, status codes, pagination"
policy:
  allow_implicit_invocation: true

Managing Your Installation

Check What's Installed

node scripts/list-installed.js --target antigravity

Repair a Broken Install

# First, diagnose what's wrong
node scripts/doctor.js --target antigravity

# Then, restore missing or drifted files
node scripts/repair.js --target antigravity

Uninstall

node scripts/uninstall.js --target antigravity

Install State

The installer writes .agent/ecc-install-state.json to track which files ECC owns. This enables safe uninstall and repair — ECC will never touch files it didn't create.

Adding Custom Skills for Antigravity

If you're contributing a new skill and want it available on Antigravity:

1. Create the skill under skills/your-skill-name/SKILL.md as usual
2. Add an agent definition at agents/your-skill-name.md — this is the path the installer maps to .agent/skills/ at runtime, making your skill available in the Antigravity harness
3. Add the Antigravity agent config at .agents/skills/your-skill-name/agents/openai.yaml — this is a static repo layout consumed by Codex for implicit invocation metadata
4. Mirror the SKILL.md content to .agents/skills/your-skill-name/SKILL.md — this static copy is used by Codex and serves as a reference for Antigravity
5. Mention in your PR that you added Antigravity support

Key distinction: The installer deploys agents/ (no dot) → .agent/skills/ — this is what makes skills available at runtime. The .agents/ (dot-prefixed) directory is a separate static layout for Codex openai.yaml configs and is not auto-deployed by the installer.

See CONTRIBUTING.md for the full contribution guide.

Comparison with Other Targets

Troubleshooting

Skills not loading in Antigravity

• Verify the .agent/ directory exists in your project root (not home directory)
• Check that ecc-install-state.json was created — if missing, re-run the installer
• Ensure files have .md extension and valid frontmatter

Rules not applying

• Rules must be in .agent/rules/, not nested in subdirectories
• Run node scripts/doctor.js --target antigravity to verify the install

Workflows not available

• Antigravity looks for workflows in .agent/workflows/, not commands/
• If you manually copied ECC commands, rename the directory

Related Resources

• Selective Install Architecture — how the install system works under the hood
• Selective Install Design — design decisions and target adapter contracts
• CONTRIBUTING.md — how to contribute skills, agents, and commands