Snapshots fail with "_0x5971 is not defined"
Every snapshot attempt fails with the cryptic error _0x5971 is not defined, while everything else — reading layouts, moving objects, editing text — works normally.
What it means: a specific batch of Sidekick versions from early July 2026 could get stuck running an older backup copy of Sidekick that’s built into the extension. That backup copy has a broken snapshot feature, and — the frustrating part — it also can’t update itself, so the problem never goes away on its own. This almost always occurred on Windows with Claude Desktop. Nothing on your side caused it, and your documents are unaffected.
The telltale sign: ask your AI Assistant to run sidekick health. If the server version is stuck on an old number (1.0.15 through 1.0.18) even though the update status claims everything is up to date, you’re running the stuck backup copy.
The fix is a one-time fresh install of the extension:
- Download the latest version from the install page.
- Double-click the downloaded file so Claude Desktop offers to install it. If double-clicking doesn’t open Claude Desktop (common on Windows), open Claude Desktop and use Settings → Extensions → Advanced Settings → Install Extension to pick the file instead.
- Quit Claude Desktop fully — on Windows, closing the window leaves it running in the system tray, so right-click the tray icon near the clock and choose Quit. On a Mac, press Cmd-Q.
- Reopen Claude Desktop, open InDesign, and try a snapshot.
Current versions of Sidekick no longer have this problem, and once you’re on one, updates arrive automatically again — you won’t need to do this twice.
If snapshots still fail after the fresh install, contact support with the sidekick health output and whether you’re on Windows or Mac, and we’ll dig in with you.