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Why Unity started opening the Antigravity agent app instead of the IDE (and the fix)

tl;dr — Google split the Antigravity product at I/O 2026. The standalone "Antigravity" desktop app is now an agent-orchestration tool, not a code editor. The actual code editor is a separate install called "Antigravity IDE". Most Unity packages still match any Antigravity*.exe, so they hand Unity the wrong app. This page explains what changed and how the package in this repo detects the right one. If you just want the fix, install v1.0.7+ and re-select Antigravity IDE in Edit > Preferences > External Tools.

What actually changed on May 19, 2026

At Google I/O 2026 Google announced Antigravity 2.0, an "agent-first" rework of the Antigravity product line. It shipped as a separate desktop binary alongside the existing IDE, and they renamed the IDE to disambiguate.

So now there are two installs:

Product What it actually is Windows install dir Manifest name
Antigravity (2.0) Multi-agent orchestration UI in a Chromium shell. No code-editor surface — opening a .cs file in it just launches the agent home screen. %LOCALAPPDATA%\Programs\Antigravity\Antigravity.exe "Antigravity"
Antigravity IDE VS Code fork. The thing that actually has a text editor, tabs, IntelliSense, etc. %LOCALAPPDATA%\Programs\Antigravity IDE\Antigravity IDE.exe "Antigravity IDE"

Both apps share the same Code-fork shell and have an identical resources/app/ layout, including the same distro hash. The only reliable runtime signal that tells them apart is the name field in resources/app/package.json.

AppData paths split the same way:

  • Windows: %APPDATA%\Antigravity (agent app) vs %APPDATA%\Antigravity IDE (IDE)
  • macOS: ~/Library/Application Support/Antigravity vs ~/Library/Application Support/Antigravity IDE
  • Linux: ~/.config/Antigravity vs ~/.config/Antigravity IDE

Extensions also moved:

  • Old: ~/.antigravity/extensions
  • New: ~/.antigravity-ide/extensions (or ~/.antigravity-ide-insiders/extensions)

Why this silently broke Unity

Unity's "external script editor" support is implemented per-IDE through small packages that derive (originally) from com.unity.ide.vscode. Every community Antigravity package I've looked at — and the one in this repo, prior to v1.0.6 — used a single regex during discovery:

.*Antigravity.*.exe$        (Windows)
.*Antigravity.*\.app$        (macOS)
ends-with antigravity         (Linux)

That regex was perfectly fine when there was only one Antigravity desktop binary. After May 19, it happily matches both the IDE and the agent app. If you ended up with both installed (and a lot of people did, since the 2.0 installer doesn't remove the IDE), Unity's External Tools dropdown listed two "Antigravity" entries. Either Unity auto-picked the first candidate or the user picked the wrong one. From then on every double-clicked script launched the agent app's home screen and developers sat there wondering why their editor "broke".

It's worse than that, actually: even if you manually Browse... to the correct Antigravity IDE.exe, the old discovery code labelled it just "Antigravity" in the dropdown, indistinguishable from the agent-app entry.

The fix in this package (v1.0.6+)

Three layers:

1. Filename-level filtering

IsCandidateForDiscovery now requires the IDE-specific filename:

#if UNITY_EDITOR_WIN
    return File.Exists(path) && Regex.IsMatch(path, ".*Antigravity IDE.*\\.exe$", RegexOptions.IgnoreCase);
#elif UNITY_EDITOR_OSX
    return Directory.Exists(path) && Regex.IsMatch(path, ".*Antigravity IDE.*\\.app$", RegexOptions.IgnoreCase);
#else
    return File.Exists(path) && (path.EndsWith("antigravity-ide", StringComparison.OrdinalIgnoreCase)
                              || path.EndsWith("antigravity-ide-insiders", StringComparison.OrdinalIgnoreCase));
#endif

The wildcard .*Antigravity IDE.*\.exe$ (and equivalents on the other platforms) is broad enough to also catch Antigravity IDE - Insider.exe and similar future variants without picking up the bare Antigravity.exe.

2. Manifest-level verification

TryDiscoverInstallation reads resources/app/package.json and rejects anything whose name field isn't Antigravity IDE. This is the defence-in-depth — if a user has weird symlinks, or manually points External Tools at Antigravity.exe via Browse, the candidate is still rejected because the manifest says it's the agent app:

if (!string.IsNullOrEmpty(manifestName) &&
    manifestName.IndexOf("Antigravity IDE", StringComparison.OrdinalIgnoreCase) < 0)
    return false;

3. Search-path narrowing

GetVisualStudioInstallations only looks at known IDE locations. The plain Antigravity.exe / antigravity / antigravity.desktop paths were removed from Windows, macOS and Linux candidate lists. So even if both products are installed, only the IDE shows up in the dropdown — there's no ambiguous "Antigravity" entry any more.

A few other places also needed adjusting:

  • Reuse-window process matching (Process.GetProcessesByName) — used to also include plain "Antigravity" / "antigravity"; those are the agent app's process names now, so they're gone.
  • Workspace storage scan (ProcessRunner.GetProcessWorkspaces) — used to read \Roaming\Antigravity\User\workspaceStorage; now reads \Roaming\Antigravity IDE\User\workspaceStorage (and the macOS / Linux equivalents).
  • Display name — always Antigravity IDE in the External Tools dropdown, never the ambiguous bare Antigravity.

Migrating from an older version

If you were on v1.0.5 or earlier:

  1. Update the package via Unity Package Manager (the git URL hasn't changed).
  2. Open Edit > Preferences > External Tools. If your saved selection was the agent app's executable, the discovery code will refuse to register it next domain reload — re-pick Antigravity IDE from the dropdown.
  3. Domain reload by closing and reopening Unity, or by toggling Play mode.
  4. Double-click any C# script. It should launch Antigravity IDE.exe, not Antigravity.exe. The Antigravity IDE window title is the easiest way to confirm.

If you previously had Antigravity workspace state in \Roaming\Antigravity that you still want for the reuse-window feature, copy the relevant workspaceStorage subfolder across to \Roaming\Antigravity IDE. Easier in practice is to just open the Unity project in Antigravity IDE once, which writes a fresh entry.

What this doesn't fix

  • Microsoft's official C# / C# Dev Kit / Unity extensions are licensed for VS Code only and won't install on Antigravity IDE (or any other VS Code fork). Use DotRush instead — open-source Roslyn-based C# server, available from the Extensions panel inside Antigravity IDE.
  • The standalone Antigravity 2.0 agent app can't be turned into a code editor by this package. It's a separate product with its own scope. If you want the agent UI for orchestration and the IDE for writing code, install both side by side; this package just makes sure Unity routes script opens to the right one.

References