Safari Extension Path and Configuration Issues | Generated by AI

Home 2026.05

Found it. Here’s the full diagnosis:

======================================================== ROOT CAUSE: Extension loaded from Xcode DerivedData, never installed ========================================================

Your Safari extension is registered at:

~/Library/Developer/Xcode/DerivedData/TabsKiller-fxpnluewboejtagbipylkghpxpjx/Build/Products/Debug/TabsKiller.app/Contents/PlugIns/TabsKiller Extension.appex

TabsKiller.app is NOT in /Applications/.

This is why it keeps disappearing. Safari’s extension registry points to a path inside DerivedData. Every time ANY of these happens, the path breaks and Safari unloads it:

  1. You do “Clean Build Folder” in Xcode
  2. Xcode auto-purges old DerivedData (it does this periodically)
  3. You rebuild and Xcode creates a NEW DerivedData folder with a different hash
  4. macOS updates or Safari gets updated
  5. System restart (Safari re-validates extension paths on boot)

The extension was NEVER properly installed — you’ve been running it from Xcode’s debug build, which is temporary by design.

======================================================== SECONDARY ISSUES (also problematic) ========================================================

  1. MISSING FILES — The “TabsKiller Extension/” directory (SafariWebExtensionHandler.swift + extension Info.plist) was NEVER committed to git. The Xcode project references them but they don’t exist on disk. This means the extension target can’t build from a clean clone.

  2. BUNDLE ID CASE MISMATCH:
    • project.pbxproj: com.lzw.TabsKiller.Extension
    • ViewController.swift: com.lzw.tabskiller.Extension (lowercase!) Safari extensions are case-sensitive. This can cause “extension not found” errors.
  3. MANIFEST V2 on macOS 26 — Your manifest.json uses manifest_version: 2 (browser_action, background.page). Safari on macOS 26 Tahoe may require Manifest V3 (action, service_worker). Safari periodically deprecates MV2 APIs and can disable MV2 extensions.

======================================================== FIX ========================================================

To permanently fix this, you need to:

  1. Rebuild the Xcode project (since the Extension target files are missing, create a fresh Safari Web Extension project or regenerate with Xcode’s “Safari Web Extension” template)

  2. ARCHIVE the app (Product → Archive in Xcode), then:
    • Export as “Developer ID” signed app
    • Copy TabsKiller.app to /Applications/
    • Launch it once from /Applications/ to register the extension

  3. OR the quick fix: just build in Xcode, then manually copy the built app: cp -R ~/Library/Developer/Xcode/DerivedData/TabsKiller-*/Build/Products/Debug/TabsKiller.app /Applications/ Then launch it from /Applications/ once.

  4. Update manifest.json to Manifest V3 if targeting macOS 26.

The copy-to-Applications step is the key. Once the .appex is in a stable path (/Applications/TabsKiller.app/Contents/PlugIns/), Safari won’t lose it.

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