🐉🗡 HydraKiller

HydraKiller is a lightweight macOS application bundle and daemon wrapper designed to mitigate runaway Apple system daemons (photoanalysisd, mediaanalysisd, and photolibraryd) on macOS Monterey 12.0 and later.

These background processes frequently trigger a cascading bug that forces the macOS "Shared with You" "Syndication" database write-ahead log (Photos.sqlite-wal) to grow unchecked, wasting significant CPU cycles and consuming hundreds of gigabytes of disk space until the hard drive is completely full.

Because launchd aggressively restarts these daemons like a replicating hydra, this project uses a C99 application shim to cleanly disable the daemons, wait out their file locks, and truncate the runaway SQLite database safely under full Transparency, Consent, and Control (TCC) authorization.

In other words... It kills Apple's hydra and saves your CPU & disk! 🐉🗡

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🛠️ System Architecture

Standard background scripts run via launchd trigger strict macOS TCC security blocks when attempting to access user Photos libraries. HydraKiller solves this by packaging a POSIX-compliant shell script inside a native compiled macOS App Bundle container. Thus, it can be run within the inherited permissions context from the App bundle.

• HydraKiller.app: A signable C99 application binary wrapper that resolves its own bundle paths and executes the embedded shell script payload via execv.
• truncate_syndication_wal.sh: The underlying POSIX script that sequentially disables and kills the daemons, monitors file locks via lsof to prevent database corruption, and safely truncates the write-ahead log.
• Launch Agent: Automates execution on a periodic background interval (e.g., hourly).
  • On macOS Monterey: com.lyraphase.HydraKillerLauncher.truncatesyndication.plist — A native user LaunchAgent that uses the older Program and ProgramArguments plist keys, for macOS 12.x compatibility
  • On macOS Ventura or later: com.lyraphase.HydraKillerLauncher.plist — A native bundled LaunchAgent that uses BundleProgram plist key to launch the embedded shim and script. This makes it possible for the HydraKillerLauncher.app to register the LaunchAgent with Apple's SMAppService API.

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🚀 Installation & Setup

App Store (Maybe in future)

TODO! I don't have an Apple Developer account, which requires $$, time, and possibly more entitlements & code signing debugging.

Manual Build

1. Embed and Build the Application

• Open the project in Xcode. Ensure your target type is a macOS App Template named HydraKillerLauncher.

• Compile the project (Product -> Build For -> Running) or press ⌘+Shift+R.

• Find the built App (Product -> Show Build Folder in Finder)

• Move the compiled App package to your /Applications folder. Drag and drop the HydraKillerLauncher.app, OR run:

  cp -R /path/to/built/HydraKillerLauncher.app ~/Applications
  

2. Configure the LaunchAgent Daemon

macOS Ventura 13.0 and Above

Run the HydraKillerLauncher.app once to trigger registering the LaunchAgent.

macOS Monterey 12.x

Copy the com.lyraphase.HydraKillerLauncher.truncatesyndication.plist configuration file into your user LaunchAgents folder:

cp HydraKillerLauncher/com.lyraphase.HydraKillerLauncher.truncatesyndication.plist  ~/Library/LaunchAgents/
launchctl load ~/Library/LaunchAgents/com.lyraphase.HydraKillerLauncher.truncatesyndication.plist

3. Authorize Full Disk Access (Optional)

In case the Photos library permissions were not enough, you can enable Full Disk Access to workaround issues with Apple's app sandbox permissions.

Because the app relies on a compiled app bundle rather than a raw terminal script, this allows it to be whitelisted natively in macOS System Settings:

• Navigate to System Settings -> Privacy & Security -> Full Disk Access.
• Click the + (Plus) button.
• Locate /Applications/HydraKillerLauncher.app and add it to the list.
• Toggle the permission switch next to it to On.

4. Start the Service

macOS Ventura 13.0 and Above

To run manual mitigation immediately at any time:

launchctl start com.lyraphase.HydraKillerLauncher

macOS Monterey 12.x

To run manual mitigation immediately at any time:

launchctl start com.lyraphase.HydraKillerLauncher.truncatesyndication

5. Print Service Details

macOS Ventura 13.0 and Above

launchctl print gui/$(id -u)/com.lyraphase.HydraKillerLauncher

macOS Monterey 12.x

launchctl print gui/$(id -u)/com.lyraphase.HydraKillerLauncher.truncatesyndication

🧾 License

This project is open-source software licensed under the GNU Affero General Public License v3.0 (AGPLv3).

See LICENSE

🔗 References & Acknowledgments

• Controlling photoanalysisd background workloads: G.J. Bianco on dev.to
• App bundle project structure and wrapper mechanics: StackOverflow Compilation Guidelines
• Runaway mediaanalysisd & Syndication WAL analysis: MacRumors Forums (Posts #29 and #30 by myself)