feat(agent): add Antigravity (agy) CLI agent

[peyton-alt]

https://entire.io/gh/entireio/cli/trails/444

Summary

• Adds first-class support for Antigravity CLI (agy), Google's successor to Gemini CLI as of 2026-05, as a new agent in the Entire CLI. Mirrors the Gemini/Claude integration model: agent package implements Agent + HookSupport, installs hooks into .agents/hooks.json, and routes pre-tool-use / post-tool-use / pre-invocation / post-invocation / stop hooks through entire hooks antigravity <verb>.
• Verified end-to-end against the real agy binary: shadow branch creation, files_touched capture, Entire-Checkpoint: <hex> trailer on user commits, and matching Checkpoint: <hex> entry on entire/checkpoints/v1.
• Registered for the E2E suite (E2E_AGENT=antigravity) and covered by integration tests at cmd/entire/cli/integration_test/antigravity_test.go.

Notable real-agy quirks (all hardened in code + tests)

• invocationNum is 0-indexed despite docs reading like 1-based — parsePreInvocation gates TurnStart on invocationNum == 0, dropping per-invocation follow-ups so the framework's pre-prompt state isn't clobbered after tool calls.
• agy writes its transcript AFTER Stop fires. Implements TranscriptPreparer to materialize an empty placeholder, so the framework's fileExists check in handleLifecycleTurnEnd doesn't abort.
• Stop maps to TurnEnd, not SessionEnd, so SaveStep runs (shadow branch commit + step_count++) and the eventual git commit actually condenses.
• agy 1.0.0 double-encodes tool args ("TargetFile":"\"foo.txt\"", "Overwrite":"true"). decodeAgyString / decodeAgyBool tolerate both the docs shape and the actual wire shape.
• macOS /tmp → /private/tmp symlink would filter agy-supplied paths as "outside repo"; resolveAgySymlinks resolves parent-dir symlinks.

Known v1 gaps (documented inline)

• Resume sessions (agy --continue, agy --conversation <id>) start with invocationNum > 0, so they don't fire TurnStart. Tracking only works on fresh conversations until we add a state-existence check.
• No "tracked by entire" banner in the agy UI. Other agents that expose a SessionStart-equivalent hook (Claude Code, Gemini CLI) print a one-line banner inside the agent terminal confirming that the session is being checkpointed. agy does not expose a session-start hook, so we cannot inject that banner — entire still tracks the session (entire status lists it, checkpoints land, commits get the trailer), it's just silent in the agy UI. Matches the existing pattern for Cursor / OpenCode / Copilot CLI / Pi, which also lack the hook. Will be addressed if Google adds a session-start hook surface.
• Transcript field-aware decoding (token counts, prompt-line attribution) is deferred — prompt_attributions lands with zero line counts in v1.

Test plan

• mise run check (fmt + lint + unit + integration + canary E2E) is green locally
• CI passes
• Reviewer can install via entire agent add antigravity in a test repo and run a real agy session, then confirm Entire-Checkpoint: <hex> lands on the commit
• Vogon canary E2E still green (no regression in the deterministic E2E path)
• Optional: real-agy E2E (mise run test:e2e --agent antigravity) — note costs real API tokens

🤖 Generated with Claude Code

---

Note

Medium Risk
New agent code paths affect session lifecycle, hook-installed repo files, and checkpoint condensation; risk is mitigated by extensive tests but behavior depends on undocumented agy wire formats.

Overview
Adds preview first-class support for Antigravity CLI (agy): a new antigravity agent package that registers with Entire, installs five workspace hooks into .agents/hooks.json (entire entry → entire hooks antigravity <verb>), and maps hook stdin to lifecycle events (TurnStart, ToolUse, TurnEnd).

Lifecycle behavior is tailored to real agy quirks: TurnStart only when invocationNum == 0 (follow-up pre-invocations are ignored so baselines aren’t reset); Stop with fullyIdle → TurnEnd (so SaveStep/checkpoints run); post-invocation is a no-op because transcripts aren’t ready yet; PrepareTranscript creates an empty placeholder when the transcript file is still missing after stop. Pre-tool-use records touched files from mutating tools, including double-encoded args and parent-dir symlink normalization (macOS /tmp).

Also wires non-interactive GenerateText via agy -p, JSONL transcript chunk/reassemble (passthrough v1), registry/hooks CLI imports, integration tests over subprocess hooks, and optional E2E registration when agy is on PATH.

^{Reviewed by Cursor Bugbot for commit f141838. Configure here.}

[Copilot]

Pull request overview

Adds first-class preview support for the Antigravity (agy) CLI agent, wiring it into Entire’s agent registry, hook handling, transcript lifecycle, text generation, integration tests, and optional E2E coverage.

Changes:

• Introduces a new agent/antigravity package with identity, hook install/uninstall, lifecycle parsing, transcript handling, text generation, and discovery stubs.
• Registers Antigravity in hook routing, agent constants, tests, and E2E agent support.
• Adds fixtures and unit/integration coverage for Antigravity hook payloads, lifecycle behavior, hook config management, and transcript preparation.

Reviewed changes

Copilot reviewed 24 out of 24 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
e2e/agents/antigravity.go	Adds E2E runner support for agy.
e2e/agents/antigravity_test.go	Adds basic E2E agent identity tests.
cmd/entire/cli/integration_test/antigravity_test.go	Adds integration coverage for Antigravity hook flow.
cmd/entire/cli/hooks_cmd.go	Registers Antigravity hooks command package.
cmd/entire/cli/agent/registry.go	Adds Antigravity agent name/type constants.
cmd/entire/cli/agent/generate_external_test.go	Adds Antigravity text generation test coverage.
cmd/entire/cli/agent/antigravity/antigravity.go	Defines Antigravity agent identity and core methods.
cmd/entire/cli/agent/antigravity/antigravity_test.go	Tests agent registration, interfaces, and presence detection.
cmd/entire/cli/agent/antigravity/discovery.go	Adds review skill discovery stub.
cmd/entire/cli/agent/antigravity/generate.go	Adds non-interactive agy text generation.
cmd/entire/cli/agent/antigravity/hooks.go	Adds .agents/hooks.json install/uninstall/status handling.
cmd/entire/cli/agent/antigravity/hooks_test.go	Tests hook config installation behavior.
cmd/entire/cli/agent/antigravity/lifecycle.go	Maps Antigravity hook payloads to Entire lifecycle events.
cmd/entire/cli/agent/antigravity/lifecycle_test.go	Tests lifecycle parsing and file extraction edge cases.
cmd/entire/cli/agent/antigravity/transcript.go	Adds JSONL transcript read/chunk/reassemble and preparation.
cmd/entire/cli/agent/antigravity/transcript_test.go	Tests transcript round-trip and placeholder creation.
cmd/entire/cli/agent/antigravity/types.go	Defines Antigravity hook payload/config types.
cmd/entire/cli/agent/antigravity/types_test.go	Tests fixture decoding for hook payload types.
cmd/entire/cli/agent/antigravity/testdata/hook_stdin_pre_invocation.json	Adds PreInvocation fixture.
cmd/entire/cli/agent/antigravity/testdata/hook_stdin_post_invocation.json	Adds PostInvocation fixture.
cmd/entire/cli/agent/antigravity/testdata/hook_stdin_pre_tool_use.json	Adds PreToolUse fixture.
cmd/entire/cli/agent/antigravity/testdata/hook_stdin_post_tool_use.json	Adds PostToolUse fixture.
cmd/entire/cli/agent/antigravity/testdata/hook_stdin_stop.json	Adds Stop fixture.
cmd/entire/cli/agent/antigravity/testdata/transcript_sample.jsonl	Adds sample Antigravity JSONL transcript fixture.

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