Antigravity — the secondary agent

Claude Code (c) is primary. Antigravity (a) is secondary. Same brain, cheaper lane.

Antigravity is Google's terminal coding agent (agy, Gemini-powered). kun installs it alongside Claude Code as a secondary agent for two jobs:

1. Fallback — when claude is down, unauthenticated, or rate-limited, reach for a and keep moving.
2. Easy / cheap tasks — quick edits, lookups, renames, one-file changes. Antigravity defaults to Gemini Flash (fast + cheap), so offloading trivial work here saves the primary agent's budget for the hard problems.

It is not a different toolchain. The onboarding wizard wires it to the same MCP fleet, the same skills, and the same databayt playbook Claude Code uses — so a behaves like kun, just on a lighter model. Reach for Claude Code (c) for anything beyond "easy": architecture, multi-step features, schema/migration work, anything risky.

The a launcher

The installer adds a shell launcher mirroring c:

Copy# what the onboarding scripts write to ~/.zshrc / ~/.bashrc / $PROFILE
function c { claude --dangerously-skip-permissions "$@"; }   # primary
function a { agy --dangerously-skip-permissions "$@"; }       # secondary

• c → Claude Code, permissions skipped (the daily driver).
• a → Antigravity, permissions skipped.
• The binary itself stays reachable as plain agy (e.g. agy --help, agy mcp list).

The old cc helper (safe claude with prompts) was removed — c is the only Claude launcher.

agy --help is the source of truth for Antigravity's flags. If --dangerously-skip-permissions ever differs in a new release, update the launcher in .claude/scripts/onboarding-* to match.

Shared configuration

Everything lives under ~/.gemini/, wired to the kun config already in ~/.claude/ by .claude/scripts/antigravity-sync.sh (called from setup.sh, re-run on every setup):

Why the MCP fleet is transformed, not symlinked

Antigravity reads the same shape as Claude — top-level mcpServers, command/args/env for local stdio servers — but remote servers use serverUrl instead of Claude's type: http|sse + url, and it ignores Claude's registries block. So a plain symlink would silently break the ~5 remote servers (vercel, sentry, linear, stripe, figma). antigravity-sync.sh rewrites them:

Copy// ~/.claude/mcp.json (Claude)        →  ~/.gemini/config/mcp_config.json (Antigravity)
"vercel": { "type": "http",           "vercel": { "serverUrl":
            "url": "https://..." }                "https://..." }
"shadcn": { "command": "npx",         "shadcn": { "command": "npx",      // stdio: unchanged
            "args": ["shadcn","mcp"] }            "args": ["shadcn","mcp"] }

AGENTS.md carries the shared playbook; GEMINI.md holds only the Antigravity-specific "you are the secondary agent" doctrine and takes precedence where the two overlap.

Install & verify

Antigravity installs automatically in Phase 5 of onboarding (the same phase as Claude Code). To set it up on a machine that already has the kun config:

Copy# install the CLI (idempotent native installer → ~/.local/bin/agy)
curl -fsSL https://antigravity.google/cli/install.sh | bash      # macOS / Linux
# windows: irm https://antigravity.google/cli/install.ps1 | iex
 
# wire it to the kun config (MCP + skills + playbook + doctrine)
bash ~/kun/.claude/scripts/antigravity-sync.sh

Verify:

Troubleshooting

Where to go next

• Onboarding — the one-paste setup that installs both agents
• Claude Code — the primary agent
• MCP — the server fleet both agents share
• Cowork ↔ Code — Claude's two modes, same ~/.claude/