omp-antigravity-acp

Google Antigravity's official ACP server, adapted for Oh My Pi (OMP).

An OMP-focused derivative fork of zacbemis/pi-antigravity-acp-provider. Original project by zacbemis and contributors, licensed under MIT.

This is an independent adaptation, not an official Google or OMP integration. It uses ACP over stdio. The local HTTP MCP bridge carries tool calls; it is not a model API reverse proxy.

Upstream and fork scope

The original project's ACP transport, Google-managed authentication, runtime installation, session restoration and MCP tool bridge form the foundation of this project. Credit for those capabilities belongs to the upstream authors.

This derivative adds OMP-specific provider registration, confirmed model/thinking selectors, lazy catalog loading, OMP-first tool instructions, API-equivalent pricing and per-session runtime lifecycle fixes for planning/refinement.

The repository keeps the OMP adapter sources separately and installs upstream version 0.1.15 as an unmodified, pinned npm dependency. It does not contain a copy of upstream's Git history. See THIRD_PARTY_NOTICES.md for the original copyright and license notice.

Status

Version 0.1.3 supports all models advertised by the official ACP server. Tested with macOS, OMP 18.12.2, upstream provider 0.1.15 and official ACP runtime 1.4.1. Other platforms and OMP versions are not yet verified.

Google's consumer-plan policies can restrict third-party agent access even through the official CLI or ACP executable. An official transport does not establish permission to use a subscription in OMP. Check the current Antigravity FAQ and terms for your account.

Features

• All server-advertised model IDs, without a Gemini-only whitelist. Claude, GPT-OSS or future models become available when the ACP endpoint advertises them for your account.
• Per-model, server-confirmed thinking selection. OMP efforts off, minimal, low, medium, high, xhigh and max are exposed only when advertised; models without these choices use the server default.
• Compatible OMP tools exposed through an authenticated loopback MCP bridge.
• Provider-specific instructions prefer OMP tools and require approval before substituting native Antigravity tools. These instructions are not a hard tool-disable mechanism.
• Lazy ACP startup; model selection and cached listing do not launch the server.
• Runtimes scoped to OMP sessions, including recovery after a planning session is disposed.
• OAuth credentials owned by Antigravity; OMP stores only a non-secret marker.
• API-equivalent cost estimates, not subscription billing or quota measurements.

Install from the OMP marketplace

No server is needed: this GitHub repository is also an OMP marketplace named sencha-plugins.

Add the source once, then install the plugin:

omp plugin marketplace add SenCha930511/omp-antigravity-acp
omp plugin install omp-antigravity-acp@sencha-plugins

Or, inside OMP:

/marketplace add SenCha930511/omp-antigravity-acp
/marketplace

Select omp-antigravity-acp in the browser, install it, and restart OMP to load the provider.

OMP's marketplace installer currently copies Git content without installing npm dependencies. This marketplace therefore ships a small source launcher that retrieves the exact published 0.1.3 prebuilt npm adapter and production dependencies on first load. It disables npm install scripts, skips Pi CLI peer installation, and performs no local compilation. Node.js 22.19+ and npm must be on PATH. First preparation needs internet access and roughly 150 MiB of disk space; later loads reuse the installed cache without npm network access.

The launcher stores its versioned dependencies in .runtime/ inside the installed marketplace plugin's cache directory. Uninstalling the marketplace plugin removes that cache when it is no longer referenced by another scope. Google credentials and the separately downloaded official ACP runtime are unaffected.

Use either marketplace installation or direct npm installation for this provider. Disable/remove an existing installation before switching to avoid duplicate provider registration. Adding this source makes it available to users who add sencha-plugins; it does not submit the package to a central curated store.

To refresh the catalog and upgrade an existing marketplace installation:

omp plugin marketplace update sencha-plugins
omp plugin upgrade omp-antigravity-acp@sencha-plugins

Install directly from npm

The prebuilt package is published on npm as omp-antigravity-acp. Use Node.js 22.19 or newer and OMP to install the latest release:

omp plugin install npm:omp-antigravity-acp

To install the first public npm release explicitly:

omp plugin install npm:omp-antigravity-acp@0.1.1

Restart OMP after installation. The npm package includes the built adapter; users do not need esbuild or a manual build step. Disable any older ACP adapter for the same provider before loading this package.

The upstream dependency declares Pi-specific peers, so package managers that automatically install peers may also fetch the Pi CLI. The OMP adapter does not invoke that CLI. This does not apply to source installs using this repository's .npmrc.

Find it with zmarketplace

zmarketplace searches npm using ecosystem keywords; it has no separate submission catalog. This package includes the pi-package keyword used for both Pi and OMP discovery, plus extension and plugin resource tags. These discovery tags do not establish compatibility with untested agent runtimes; this adapter targets OMP.

With zmarketplace already installed in OMP:

/zmarketplace search omp-antigravity-acp --eco=omp --type=extension

Or search from a terminal with Bun:

bunx zmarketplace search omp-antigravity-acp --eco=omp --type=extension

Use the OMP installation target when installing from the search result. The direct OMP command is omp plugin install npm:omp-antigravity-acp. Newly published metadata may take time to appear in npm search results.

Build from source

Use Node.js 22.19 or newer and OMP. Node.js is also required by the upstream process supervisor.

npm ci
npm run check

The checked-in npm configuration disables automatic peer installation because the upstream package declares Pi-specific peers. This adapter explicitly supplies its runtime dependency on pi-ai; it does not need the Pi coding-agent CLI.

The build produces extension/runtime.mjs and THIRD_PARTY_LICENSES.txt. They are ignored by Git, rebuilt locally and included in published npm tarballs. Supervisor and runtime catalog paths resolve against the installed upstream dependency, so the bundle does not embed the developer's home directory.

For a temporary session, from this repository:

omp --no-extensions -e ./extension/index.ts

This disables other extension discovery for that invocation, avoiding duplicate registration of an existing ACP adapter. For normal installation, use OMP's extension configuration or point ~/.omp/agent/extensions/omp-antigravity-acp at the built extension directory. Disable any previous antigravity-acp-omp or upstream Pi extension first; do not load two adapters for the same provider.

This repository does not change an existing OMP installation or overwrite its settings.

Sign in and choose a model

1. Run /login and select Google Antigravity (ACP).
2. Complete Google's authorization flow. On headless machines the upstream provider can relay a browser callback.
3. Run /antigravity-acp refresh to discover the models actually advertised for the account.
4. Select a model with /model and use OMP's thinking control to select a supported effort.

First use or login may download the official runtime. The observed macOS runtime occupies about 383 MiB; size varies by platform/version. It lives outside this repository under ~/.local/opt/agy-acp/. Do not remove it while ACP processes are running.

If OMP's enabledModels whitelist is configured, add antigravity-acp/* alongside your existing entries in ~/.omp/agent/config.yml to allow newly discovered models. Use individual antigravity-acp/<server-model-id> entries instead if you prefer a restricted list. The adapter does not rewrite that whitelist or any model-role preset.

After upgrading from an older adapter, run /antigravity-acp refresh once to replace the old cached list with per-model selector choices. Startup and ordinary catalog listing remain offline, so new server models appear after an explicit refresh. Availability in the Antigravity app or CLI does not guarantee availability through ACP: on the tested account, ACP still advertised only gemini-4-argon and gemini-3.8-flash on 2026-10-19.

Commands

Command	Purpose
/antigravity-acp status	Runtime, confirmed thinking and usage information
/antigravity-acp tools	Available and omitted OMP tool schemas after a request
/antigravity-acp refresh	Explicit network discovery and local catalog refresh
/antigravity-acp permissions default	Prompting permission mode
/antigravity-acp permissions auto-edit	Auto-edit mode
/antigravity-acp permissions yolo	Upstream permissive mode

The initial permission mode follows upstream configuration, whose default is yolo. Native Antigravity tools have separate execution permissions from OMP tools.

Data locations

Data	Location
Adapter configuration, catalog and session mappings	~/.omp/agent/antigravity-acp-provider/
Official credentials/settings/history	Managed by Antigravity under its own storage/keychain
Downloaded official runtime	~/.local/opt/agy-acp/
Generated adapter bundle	extension/runtime.mjs

Never include those user data directories, OAuth callback URLs, account identifiers or downloaded runtime binaries in issues or commits. OMP_ACP_TRACE=1 enables opt-in tool/selector diagnostics; review diagnostic output before sharing.

Limitations

• Argon/Flash retain client metadata of 1,000,000 context tokens and 65,536 output tokens. Other models use conservative defaults of 32,768 context tokens and 8,192 output tokens because the model selector does not supply these limits. These are client metadata, not verified server limits or controls over Antigravity's internal compaction.
• API background execution and long decode controls are not exposed.
• The bridge advertises text and image input, not the full Gemini API media surface.
• Thought summaries appear only if the ACP server emits them. A verified Argon High request returned no agent_thought_chunk; tool/plan progress can appear in OMP's thinking area.
• Cached-token usage appears only when ACP reports it. Missing counts are not proof that backend caching was disabled.
• The prompt inactivity watchdog is 10 minutes without progress, or 60 minutes while tools/permissions are outstanding.
• Argon estimates use the undiscounted list price: $4 input, $20 output and $0.20 cached input per million tokens. Flash estimates use the announced date-dependent rates. These are snapshots, not live pricing discovery.
• Other models have no configured API price yet. Their zero cost fields are placeholders for unavailable estimates and do not mean free usage.
• Not every OMP tool schema is bridge-compatible. Inspect tools after a request.
• Antigravity still manages its own native tools and checkpoint summaries.

Development and verification

npm test runs offline regression tests for all-vendor catalogs, per-model thinking choices, selector routing, session ownership, restart-after-shutdown, asynchronous teardown and price calculations. It performs no model inference and consumes no account quota.

npm run test:packed additionally requires OMP on PATH. It installs the exact npm tarball into a temporary consumer directory with development dependencies omitted and install scripts disabled, checks runtime assets, and loads its model catalog with ACP execution disabled. It downloads production dependencies and removes the temporary installation afterward.

npm run test:marketplace exercises catalog discovery, installation, automatic provider loading, offline cache reuse and uninstallation in a temporary named OMP profile. It downloads the published adapter and cleans the entire test profile afterward. Add -- --remote after publishing catalog changes to test the GitHub source instead of the local working tree. No model inference is performed.

Before publishing, verify local OMP loading without allowing ACP to start:

AGY_ACP_BIN=/usr/bin/false omp models antigravity-acp --no-extensions -e ./extension/index.ts --json

With no local model cache, upstream's conservative fallback may list fewer models. Listing a model is not proof of account entitlement or successful inference.

The original local implementation also passed live Argon/Flash inference, effort-selector and OMP tool round-trip checks. The planning lifecycle fix passed a live Argon Medium request, session shutdown and a subsequent request with conversation history. Those tests do not cover every platform or the complete interactive Refine plan UI.

The generic catalog implementation passed a live refresh and Argon Low/High inference. Claude, GPT-OSS and future IDs are covered by offline catalog/selector fixtures; live inference for those models remains unverified until the ACP server advertises them.

License and attribution

MIT. See LICENSE and THIRD_PARTY_NOTICES.md. Upstream source is installed as a pinned npm dependency rather than vendored or modified. Official Google executables and their licenses are separate.