collaborating-with-antigravity

# Collaborating with Antigravity (agy)

Use the Antigravity CLI (`agy`) as a collaborator while Codex remains the primary implementer.
Antigravity CLI is Google's replacement for the **retiring Gemini CLI** (hosted auth shuts off
2026-06-18). If you used `collaborating-with-gemini`, switch to this skill.

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** — invoking
`agy -p` directly is unreliable (see below).

## Why the bridge is mandatory

Two `agy` v1.0.8 quirks make raw `agy -p` unusable from a script; the bridge fixes both:

- **Hangs on a pipe.** `agy -p ... | …` writes nothing and never exits. The bridge runs `agy` under a
  pseudo-terminal so its TTY check passes, and enforces its own wall-clock kill.
- **Won't reveal the conversation ID** (no `--session-id`). 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.**

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

## 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.

## 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 in Codex directly.
- Tasks requiring file edits — Codex 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="$(cat <<'EOF'
Review src/auth.py around login() and propose fixes.
OUTPUT: Unified Diff Patch ONLY.
EOF
)"
python3 skills/collaborating-with-antigravity/scripts/agy_bridge.py \
  --cd "." --model "Gemini 3.5 Flash (Low)" --PROMPT "$PROMPT"
```

**Returns** (stdout JSON): `{ "success": true, "SESSION_ID": "...", "agent_messages": "...", "model": "...", "warnings": [...] }`.
Live progress streams to **stderr**; the bridge exits non-zero on failure. In Codex, run non-trivial
calls in the background 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 skills/collaborating-with-antigravity/scripts/agy_bridge.py \
  --cd "." --PROMPT "Analyze the bug in foo()."

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

# Or continue the most recent conversation
python3 skills/collaborating-with-antigravity/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 skills/collaborating-with-antigravity/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 (v1.0.8) in [references/agy-cli.m