Adds first-class integration with Google's Antigravity IDE
(https://antigravity.google/) as a third sibling to the existing
Claude Code and Codex hook integrations. Strictly additive — no
existing files in main are restructured.
What ships
----------
* `.antigravity-plugin/` — verified-minimal plugin package:
* `plugin.json` with `{"name": "mempalace"}` (no fabricated fields)
* `mcp_config.json` registering the `mempalace-mcp` stdio server
* `hooks.json.tmpl` templated with `__PLUGIN_DIR__` substitution
* `skills/mempalace/SKILL.md` (real file — no symlinks)
* `hooks/antigravity/`:
* `lib/common.sh` — shared bash 3.2.57-compatible helpers with
sentinel-guarded camelCase JSON parser, antigravity_*-namespaced
state files, every existing kill switch, `MEMPAL_SAVE_INTERVAL >= 1`
floor (no /0), and fail-open emitters
* `mempal_save_hook_antigravity.sh` — Stop event handler:
increments per-conversation counter, defers when fullyIdle=False
or terminationReason=error, validates transcriptPath against
`..` traversal, spawns `mempalace mine --mode convos` in a
detached subprocess with a per-conversation pending marker,
ALWAYS emits `{}` (never `{"decision":"continue"}` — that would
force an infinite agent loop)
* `mempal_wake_hook_antigravity.sh` — PreInvocation handler gated
to invocationNum==1 with an atomic mkdir loop guard, runs
`mempalace wake-up` with a 500ms hard timeout, emits verbatim
output as `{"injectSteps":[{"ephemeralMessage":"..."}]}` or
`{}` on any failure
* `install.sh` — idempotent installer with cmp-gated copies,
`__PLUGIN_DIR__` substitution, relative path absolutization,
`--dry-run`, and basename-guarded `--uninstall` (refuses to
wipe a directory whose basename isn't `mempalace`)
* `INVESTIGATION.md` — verbatim quotes + URLs + dates from the
five official Antigravity doc pages, recording every surface
shipped and every surface deliberately omitted
(PreCompact equivalent, slash-commands, rules/, plugin
permissions field — the latter is third-party fabrication)
* `STDIN_SHAPE.md` — exact stdin/stdout contract per event with
worked examples
* `README.md` — local hook docs + troubleshooting
* `examples/antigravity/{hooks.json,mcp_config.json,README.md}` —
standalone configs for users who don't want the full installer
* `website/guide/antigravity.md` + sidebar entry — VitePress guide
* Updates to `README.md`, `CHANGELOG.md` (Unreleased), `hooks/README.md`
Tests (56 new, all passing)
---------------------------
* `tests/test_antigravity_plugin_manifest.py` (11 tests) — schema
contract on the in-repo `.antigravity-plugin/` directory, including
guards against re-introducing the fabricated `permissions` field
and against any symlink leak.
* `tests/test_antigravity_hooks_shell.py` (31 tests) — invokes the
bash hooks via subprocess with synthetic camelCase stdin, asserts
`{}` on every failure path, kill-switch coverage (env vars +
config.json + palace nuke), divide-by-zero floor, transcript
traversal rejection, namespacing, wing inference, and the hard
refusal to ever emit `decision=continue` from the Stop hook.
* `tests/test_antigravity_hooks_install.py` (14 tests) — `--dry-run`
side-effect-free, real install layout, executable bits preserved,
byte-identical idempotent re-runs (md5 + filecmp), basename-match
uninstall safety, refusal when plugin.json is missing or names a
different plugin, relative path absolutization. Skipped on Windows.
Verification
------------
* `uv run pytest tests/ --ignore=tests/benchmarks -v` → 2314 passed,
3 skipped (Windows), 1 unrelated warning
* `uv run ruff check .` → all checks passed
* `uv run ruff format --check .` → 139 files already formatted
* `bash -n` clean on common.sh, both hook scripts, install.sh
* Local install at `~/.gemini/config/plugins/mempalace/` verified end-
to-end: layout correct, paths absolutized in hooks.json, both hooks
fire with realistic camelCase JSON in <1s, wing inference picks
`wing_mempalace` from workspacePaths[0], state files all
`antigravity_*`-namespaced, second `install.sh` run produces
byte-identical output (md5 snapshots match), uninstall removes
only the mempalace plugin and leaves all 6 sibling Google plugins
untouched.
Constraints honoured
--------------------
bash 3.2.57 (no mapfile / readarray / declare -A / `${var^^}`),
verbatim guarantee on all wake injections, hooks <500ms / startup
injection <100ms target (kill-switch path returns in <1.5s in CI),
zero new runtime dependencies, no telemetry, no external API,
strictly additive (existing Claude/Codex hooks unchanged).
Refs: hooks/antigravity/INVESTIGATION.md for the full audit.
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