Support deep-link protocol registration for AppImage builds

[gantoine]

Problem

AppImage builds lack an installed .desktop file, so app.setAsDefaultProtocolClient() (which points xdg at one) is a no-op. This breaks OAuth callbacks: the browser cannot hand posthog-code://callback?... back to the app after authentication.

Changes

Added AppImage-specific protocol registration that mirrors manual xdg-mime default setup:

1. New module linux-appimage-protocol.ts: Detects AppImage runtime (APPIMAGE env var), builds freedesktop .desktop entries pointing at the stable $APPIMAGE path, stages the app icon to a persistent location, and registers URL schemes via xdg-mime.

2. Updated DeepLinkService: Collects all schemes (dev/prod, legacy) and calls registerAppImageSchemes() on AppImage builds. Failures are best-effort and do not block startup.

3. Updated forge.config.ts: Declared x-scheme-handler/posthog-code in the bundled .desktop entry so AppImage integrators (e.g., AppImageLauncher) register the handler at install time.

The solution is defensive: it only runs on Linux with APPIMAGE set, handles missing xdg utilities gracefully, and does not interfere with non-AppImage builds.

How did you test this?

• Added comprehensive unit tests (linux-appimage-protocol.test.ts) covering:
  • isAppImage() detection on Linux with/without APPIMAGE
  • .desktop entry generation with correct Exec path and MIME types
  • Icon staging and fallback
  • Desktop database update and xdg-mime default registration
  • Graceful handling when not running as AppImage
• Tests mock filesystem and execFile to verify correct paths and command sequences without side effects

https://claude.ai/code/session_014aMsqBjTdturnFTpnTsD1f

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 0e61eb1.}

[greptile-apps]

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
apps/code/src/main/utils/linux-appimage-protocol.test.ts:62-80
**Prefer parameterised tests for `isAppImage`**

The three cases here — `(linux, APPIMAGE set) → true`, `(linux, APPIMAGE missing) → false`, `(darwin, APPIMAGE set) → false` — all exercise the same predicate with different `(platform, envVar, expected)` inputs, which is the canonical use case for `it.each`. As a single table-driven test it would be easier to extend with new platforms and avoids the repeated `setPlatform` / `process.env` setup boilerplate.

### Issue 2 of 2
apps/code/src/main/services/deep-link/service.ts:55-59
**Dead `.catch()` — `registerAppImageSchemes` never rejects**

`registerAppImageSchemes` swallows every failure path internally: `runXdg` always resolves (warnings are logged, errors are not re-thrown), and the `writeFileSync` / `mkdirSync` catch block returns rather than throwing. The `.catch()` here can therefore never fire, making it a superfluous part. The `void` plus `.catch(log.error)` pattern is idiomatic only when the callee can reject — if you want to surface any future errors here, the callee's error handling would need to change too.

```suggestion
    if (isAppImage()) {
      void registerAppImageSchemes(schemes);
    }
```

_{Reviews (1): Last reviewed commit: "fix(deep-links): register posthog-code:/..." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (2): Last reviewed commit: "fix linxu build image target" | Re-trigger Greptile}

[Copilot]

Pull request overview

Adds Linux AppImage-specific deep-link protocol registration so OAuth callbacks (e.g. posthog-code://callback?...) can be handed back to the app even when no system .desktop file is installed.

Changes:

• Introduces an AppImage runtime helper that writes a user-scoped .desktop entry (Exec → $APPIMAGE), stages an icon, updates desktop DB, and registers x-scheme-handler/* via xdg-mime.
• Updates DeepLinkService to register all active schemes (dev/prod + legacy) and trigger AppImage registration best-effort on AppImage builds.
• Updates Forge AppImage maker config to include x-scheme-handler/posthog-code, and adjusts the Linux docker build script target mapping.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
apps/code/src/main/utils/linux-appimage-protocol.ts	Adds AppImage detection + .desktop/xdg-mime registration utilities.
apps/code/src/main/utils/linux-appimage-protocol.test.ts	Adds unit tests for AppImage scheme registration and desktop entry generation.
apps/code/src/main/services/deep-link/service.ts	Collects schemes consistently and triggers AppImage-specific registration.
apps/code/scripts/build-linux-docker.sh	Maps friendly maker targets to Forge maker names for Linux container builds.
apps/code/forge.config.ts	Declares deep-link MIME handler for AppImage .desktop generation.

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