collaborating-with-antigravity git:20260711.452f262A

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---
name: collaborating-with-antigravity
description: Delegate tasks to Google's Antigravity CLI (agy) for prototyping, debugging, code review, and research. Supports multi-turn sessions via SESSION_ID. Successor to the retired Gemini CLI.
metadata:
  short-description: Delegate to Antigravity CLI (agy)
---

# Collaborating with Antigravity (agy)

Use the Antigravity CLI (`agy`) as an independent collaborator while the calling agent stays
responsible for verification, synthesis, and final user-facing decisions. Antigravity CLI is
Google's replacement for the **retired Gemini CLI** (hosted auth shut off 2026-06-18).

The bridge script (`scripts/agy_bridge.py`) wraps `agy -p` (headless print mode), returns structured
JSON, and manages session continuity via `SESSION_ID`. **Always go through the bridge** — raw `agy -p`
surfaces no conversation ID and no structured output (see below).

## Why the bridge is mandatory

- **agy won't reveal the conversation ID** (no `--session-id`, never printed). The bridge recovers it
  from agy's cache, returns it as `SESSION_ID`, and resumes via `--conversation`. It also serializes
  calls with a file lock — **don't run bridge calls concurrently.**
- **agy has no structured output.** The bridge shapes plain text into JSON, streams live progress to
  stderr, and enforces its own wall-clock kill as the real timeout.

Mechanics, upstream issue numbers, and the verified flag surface: [references/agy-cli.md](references/agy-cli.md).

Commands below write `<skill_dir>` for the absolute path of the directory containing this SKILL.md. Your harness reports that path when it loads the skill, for example `~/.claude/skills/collaborating-with-antigravity`. Substitute it before running.

## Safety

`agy` can read and write files and run tools in the workspace. To constrain it:

- `--sandbox` is **on by default** in the bridge — it applies agy's terminal restrictions.
  **Recommended for review/consultation.** Use `--no-sandbox` only when you deliberately want edits/shell.
- Include `OUTPUT: Unified Diff Patch ONLY. Do not modify any files.` in the prompt when requesting
  code changes. This is a convention, not enforced.
- `--skip-permissions` maps to agy's `--dangerously-skip-permissions` (auto-approves every tool). Only
  use it with explicit user consent, ideally in an isolated worktree.
- Never hand `agy` secrets, private keys, or production data.

## Host-side approval (the bridge call itself)

Everything above governs the child agy. The **host** agent's own permission layer gates the `python3 … agy_bridge.py` Bash call first — and under classifier-gated auto-approval (Claude Code `auto`/`dontAsk`, Codex non-interactive runs), a long-running script that spawns another agent over the codebase pattern-matches "high-risk" and can be **denied silently**: the delegation never starts. A host permission error instead of bridge JSON means the host blocked the bridge, not that agy failed.

- **Pre-authorize the bridge instead of relying on the classifier.** Claude Code host: add `"Bash(python3 *collaborating-with-antigravity*bridge.py*)"` to `permissions.allow` in your `settings.json`. The wildcard form keeps matching wherever the skill is installed. Sandboxed hosts also need `"python3 *collaborating-with-antigravity*bridge.py*"` in `sandbox.excludedCommands`, because sandbox network policy blocks the child CLI's API traffic even after the command is allowed. Install and approval runbooks: [docs/setup/](https://github.com/appautomaton/agent-designer/tree/main/docs/setup) in the source repo.
- **Codex host: the sandbox is the second gate.** The child `agy` CLI needs network for Google auth and inference, which the host sandbox blocks in `read-only` and `workspace-write`. Run the bridge call through an approved escalation, or knowingly grant network for that call.
- **Never degrade silently.** If the host denies the bridge call, report it and propose the allowlist fix — don't substitute your own answer for the independent second opinion that was requested.

## When to use
- Second opinion on design tradeoffs, edge cases, or test gaps.
- Web search / research (Antigravity has built-in grounding).
- Reviewing a diff or proposing changes as a unified diff.
- Screenshot / image analysis.

## When not to use
- Trivial one-shot tasks — do them directly.
- Tasks requiring file edits — the calling agent edits, agy advises.
- Anything involving secrets, private keys, or prod data.

## Quick start

⚠️ Backticks / `$VARS` in prompts trigger shell expansion — use a single-quoted heredoc, or
`--prompt-file` for large/generated prompts. See [references/shell-quoting.md](references/shell-quoting.md).

```bash
PROMPT="$(cat <<'EOF'
Review src/auth.py around login() and propose fixes.
OUTPUT: Unified Diff Patch ONLY.
EOF
)"
python3 <skill_dir>/scripts/agy_bridge.py \
  --cd "." --model "Gemini 3.5 Flash (Low)" --PROMPT "$PROMPT"
```

**Returns** (stdout JSON): `{ "success": true, "SESSION_ID": "...", "agent_messages": "...", "model": "...", "warnings": [...] }`.
Live progress streams to **stderr**; the bridge exits non-zero on failure. Run non-trivial calls in
the host's background-command mode and watch the stderr progress.

## Multi-turn sessions

Capture `SESSION_ID` from the first call and pass it back (use the same `--cd`):

```bash
# Turn 1
python3 <skill_dir>/scripts/agy_bridge.py \
  --cd "." --PROMPT "Analyze the bug in foo()."

# Turn 2 — resume by ID
python3 <skill_dir>/scripts/agy_bridge.py \
  --cd "." --SESSION_ID "<id>" --PROMPT "Propose a fix as a unified diff."

# Or continue the most recent conversation
python3 <skill_dir>/scripts/agy_bridge.py \
  --cd "." --continue --PROMPT "What about edge cases?"
```

`--SESSION_ID` and `--continue` are mutually exclusive; `--continue` resumes agy's most-recent
conversation *globally* (not per-`--cd`), so prefer `--SESSION_ID` for deterministic resume. Sessions
persist as SQLite under `~/.gemini/antigravity-cli/conversations/<id>.db`. **Save turn 1's `SESSION_ID`** —
agy can't pre-assign one and never reprints it, so an unsaved conversation can't be resumed.

## Bridge flags

| Flag | Purpose | Default |
|---|---|---|
| `--PROMPT` / `--prompt-file` | Prompt text, or read it from a file (mutually exclusive) | — |
| `--cd` | Workspace root (required unless `--list-models`) | — |
| `--SESSION_ID` | Resume a conversation by ID (→ `agy --conversation`) | new conversation |
| `--continue` | Continue the most recent conversation (→ `agy -c`) | off |
| `--model` | Model from `agy models`, e.g. `"Gemini 3.5 Flash (Low)"`, `"Claude Sonnet 4.6 (Thinking)"` | CLI default |
| `--sandbox` / `--no-sandbox` | agy terminal restrictions | **on** |
| `--skip-permissions` | Auto-approve all tools (`--dangerously-skip-permissions`) | off |
| `--list-models` | Print `agy models` as JSON and exit (no prompt/`--cd`) | — |
| `--no-validate-model` | Skip validating `--model` against `agy models` | off |
| `--add-dir` | Additional workspace dir (repeatable) | none |
| `--print-timeout` | agy print wait, e.g. `5m`/`90s` (agy may ignore it) | `5m` |
| `--timeout` | Bridge wall-clock kill, seconds (the real cap) | print-timeout + 120s |
| `--log-file` | Override agy's log path | none |
| `--return-all-messages` | Include `raw_output` and the conversation `.db` path | off |

Set the host's `timeout_ms` to **600000** (10 min) when invoking via a command runner.

## Models

**Probe the live list — don't hardcode it:**

```bash
python3 <skill_dir>/scripts/agy_bridge.py --list-models
# -> { "success": true, "models": ["Gemini 3.5 Flash (Low)", "Claude Sonnet 4.6 (Thinking)", ...] }
```

Pass the exact string to `--model`. agy itself does **not** validate `--model` — a misspelled or
unknown name silently runs the default — so the bridge validates against `agy models` and errors on an
unknown name (`--no-validate-model` to skip). Rough guide: Flash (Low) for quick checks, Gemini Pro or
Claude for hard tasks. Full snapshot in [references/agy-cli.md](references/agy-cli.md).

## Prompting

Use [assets/prompt-template.md](assets/prompt-template.md) for structured starters. Key principles:

- **Point, don't paste** — give file paths and line numbers, not code blocks.
- **One objective per prompt** — competing goals produce noisy output.
- **Enforce output format** — append `OUTPUT: Unified Diff Patch ONLY.` for code changes.
- **Leverage grounding** — agy can search the web; ask for research when needed.

### Screenshots

agy reads files inside the workspace. Copy screenshots in first, then reference the path (example for a Codex host — adapt the clipboard source path to your host):

```bash
mkdir -p .codex_uploads && cp "${TMPDIR:-/tmp}"/codex-clipboard-*.png .codex_uploads/
```

Don't add the upload dir to `.gitignore` (agy, like Gemini, may refuse to read ignored paths). Delete screenshots when done.

## Verification

- Smoke: `python3 <skill_dir>/scripts/agy_bridge.py --help`
- Syntax: `python3 -m py_compile <skill_dir>/scripts/agy_bridge.py`
- Auth: run `agy` once and sign in with Google (token at `~/.gemini/antigravity-cli/`).
- Session test: run one prompt; confirm JSON has `success: true` and a `SESSION_ID`, then resume with
  `--SESSION_ID` and confirm continuity.

## Collaboration State Capsule

Keep this block updated while collaborating:

```
[Antigravity Capsule] Goal: | SID: | Model: | Sandbox: | Files: | Last: | Next:
```

## References
- [references/agy-cli.md](references/agy-cli.md) — verified `agy` flags, models, file layout, quirks
- [assets/prompt-template.md](assets/prompt-template.md) — structured prompt patterns
- [references/shell-quoting.md](references/shell-quoting.md) — heredoc quoting for backticks