Antigravity Companion for JetBrains IDEs

A JetBrains plugin that bridges the Antigravity CLI (agy) with JetBrains IDEs (IntelliJ IDEA, PhpStorm, WebStorm, PyCharm, GoLand, and other IntelliJ-based IDEs) so the agent can see your active file, selection, open tabs, and inspection diagnostics on demand.

Features

The plugin exposes four MCP tools to agy:

Tool	What it returns
ide_get_active_editor	File path, language, cursor (1-based), selection range and text, full file content
ide_get_open_files	Absolute paths of every file currently open in an editor tab
ide_get_diagnostics	Inspections, syntax errors, and warnings for a file (or the active editor)
ide_open_file	Open a file at an optional line/column

When you click the Open Antigravity CLI toolbar button, agy launches in an IDE-embedded terminal already wired to the current project — no manual configuration steps. By default the button focuses the existing Antigravity terminal tab if one is open; toggle Always open a new tab in settings to spawn a fresh session on every click.

Requirements

• A JetBrains IDE built on IntelliJ Platform 232+ (PhpStorm, IntelliJ IDEA, WebStorm, GoLand, RustRover, … — anything from 2023.2 through the current release).
• The Antigravity CLI installed locally. The plugin will look for agy (or agy.exe on Windows) on $PATH, then in ~/.local/bin, /opt/homebrew/bin, and /usr/local/bin. You can override the location in the plugin settings.
• macOS, Linux, or Windows. The plugin's stdio bridge uses the IDE's bundled JBR (Java) — no external tools like nc are required.

Installation

From a release ZIP

1. Grab or build an antigravity-companion-<version>.zip (see Building from source if you don't have one).
2. In the IDE: Settings → Plugins → ⚙ → Install Plugin from Disk…
3. Pick the ZIP and restart when prompted.

From source

See Building from source.

Configuration

Open Settings → Tools → Antigravity Companion.

• Path to agy executable — absolute path to the agy binary the plugin should launch. Leave blank to auto-detect ($PATH + common install dirs). The settings panel tells you which path it currently resolves to.
• Always open a new tab — when off (default), clicking the toolbar focuses the existing Antigravity terminal tab if one is open; when on, every click spawns a fresh agy session.
• Keyboard shortcut — no shortcut is bound by default (no chord is safe across every bundled keymap). Click Configure shortcut in Keymap settings… in the panel, or open Settings → Keymap directly and search for Open Antigravity CLI, to assign one. Multiple parallel agy sessions are still supported regardless of how the action is triggered.

No other configuration is required. The plugin manages ~/.gemini/config/mcp_config.json on its own and cleans up after itself when projects close.

Usage

1. Open a project and the file you want agy to see.
2. Click the lightning ⚡ toolbar button (top-right) or invoke Open Antigravity CLI from Find Action (⇧⌘A / Ctrl+Shift+A).
3. A terminal tab opens with agy running. Ask it about your code — when it needs context it will call the plugin's MCP tools transparently.

A useful first prompt: "What file am I looking at? Use ide_get_active_editor."

How it works

agy reads MCP server definitions from ~/.gemini/config/mcp_config.json. On project open the plugin:

1. Starts a small JSON-RPC server on 127.0.0.1:<random> (line-delimited MCP over a plain TCP socket).
2. Writes a per-project bridge script — jetbrains-mcp-bridge-<productCode>-<projectHash>.sh on Unix or .bat on Windows — under ~/.gemini/antigravity-cli/. <productCode> is the JetBrains IDE code (iu, ps, ws, py, go, …) so two IDEs opening the same project don't collide. The script uses the IDE's bundled JBR to run a tiny pure-Java stdio↔TCP relay, so agy (which speaks stdio MCP) can reach the in-IDE TCP server with no external dependencies.
3. Merges its entry into mcp_config.json under mcpServers.jetbrains-companion-<productCode>-<projectHash> (preserving any other entries).

On project close it removes the config entry and deletes the bridge script.

┌────────────────────┐   stdio    ┌──────────────────┐   TCP    ┌─────────────────┐
│ agy CLI (terminal) │ ─────────► │ bridge script    │ ───────► │ Plugin MCP svr  │
│                    │ ◄───────── │ (JBR StdioBridge)│ ◄─────── │ (in JetBrains)  │
└────────────────────┘            └──────────────────┘          └─────────────────┘

Where things live

Path	Purpose
~/.gemini/config/mcp_config.json	The plugin merges/removes its jetbrains-companion-<productCode>-<projectHash> entry here. Other entries are preserved. On register, the plugin also removes any legacy keys for this project's projectHash (e.g. phpstorm-companion-<projectHash>) left behind by older plugin versions; legacy entries belonging to other projects are not touched.
~/.gemini/antigravity-cli/jetbrains-mcp-bridge-<productCode>-<projectHash>.{sh,bat}	Auto-generated bridge script; deleted on project close. Do not edit by hand.
~/.gemini/antigravity-cli/cli.log (symlink to latest run)	agy's log — useful when MCP traffic looks wrong.
IDE idea.log	Plugin logs. Look for AntigravityCompanionService: MCP server listening on 127.0.0.1:<port>, MCP client connected from ….

Troubleshooting

The "Open Antigravity CLI" button shows a notification "agy executable not found". Open Settings → Tools → Antigravity Companion and set the path explicitly, or install agy to one of the auto-detected locations.

agy answers "I don't have visibility into your IDE". The plugin probably isn't registered. Check:

1. Settings → Plugins — make sure the plugin is enabled.
2. idea.log for MCP server listening on 127.0.0.1:<port>.
3. ~/.gemini/config/mcp_config.json contains a jetbrains-companion-* entry.

agy log shows Connection refused or socket errors on startup. The IDE (or that project) closed while agy was still running. Quit agy and relaunch it from the toolbar button — the plugin re-registers a fresh port each time a project opens.

mcp_config.json is corrupted. Delete it; the plugin will recreate it on the next project open.

Building from source

Prerequisites

• Git
• JDK 17 (Temurin, Zulu, or the IDE's bundled JBR all work). JAVA_HOME must point at it.
• Internet access on first build — the IntelliJ Gradle plugin downloads a sandboxed IDE matching platformVersion in gradle.properties.

Steps

git clone https://github.com/matasarei/antigravity-companion.git
cd antigravity-companion
./gradlew buildPlugin

The signed (unsigned in dev) plugin archive will be at:

build/distributions/antigravity-companion-<version>.zip

Install it via Settings → Plugins → ⚙ → Install Plugin from Disk….

Useful Gradle tasks

./gradlew runIde           # launch a sandbox IDE with the plugin pre-loaded
./gradlew verifyPlugin     # IntelliJ Plugin Verifier — static checks
./gradlew clean buildPlugin # full rebuild

./gradlew runIde is the fastest dev loop: it starts a fresh sandbox IDE, side-loads the plugin, and tears down on exit. Edit code, rerun, repeat.

Project layout

src/main/
├── java/dev/matasar/antigravity/bridge/
│   └── StdioBridge.java                          ← pure-Java stdio↔TCP relay
└── kotlin/dev/matasar/antigravity/
    ├── action/StartSessionAction.kt              ← toolbar button
    ├── service/AntigravityCompanionService.kt    ← MCP server + tool impls
    ├── settings/AntigravitySettings.kt           ← persistent state
    ├── settings/AntigravitySettingsConfigurable.kt ← Settings panel
    └── startup/AntigravityStartupActivity.kt     ← eager-init on project open
src/main/resources/
├── META-INF/plugin.xml                           ← plugin manifest
└── icons/                                        ← toolbar / plugin icons
build.gradle.kts, gradle.properties, settings.gradle.kts

Known limitations

• WSL2 on Windows. When running the JetBrains IDE natively on Windows but working on a project located in a WSL2 path (\\wsl.localhost\<distro>\...), the plugin cannot spawn a Linux agy binary directly. The only supported workaround is to run the JetBrains IDE itself inside WSL2 (e.g. using JetBrains Gateway or WSLg) and install the plugin and agy inside WSL.
• Pull-based only. The IDE does not push selection changes to agy mid-conversation; agy calls back over MCP when it decides it needs IDE state.
• Multi-project. Each open project registers a separate jetbrains-companion-<productCode>-<projectHash> entry. A running agy in workspace A will also see workspace B's tools in its catalog; only the live project's bridge succeeds, but the duplicate tool names can confuse the model.

License

MIT — see LICENSE.