For Mac users seeing "Failed Patching" on macOS Ventura or Sonoma:
Power users sometimes use mklink to store STEAM on a different hard drive. If the drive letter changed (e.g., D: became E:), the patcher sees a broken link and fails.
Here’s a proper, instructive story about the error — written to explain what it is, why it happens, and how to resolve it without the usual forum guesswork.