[Desktop] New sessions created from sidebar never respond — prompt_async fails: FileSystem.realPath ENOENT on missing worktree dir (global/silent-knight) #49561

Summary

OpenCode Desktop (Windows 11): clicking the "+ New session" button in the sidebar creates a new chat window, but sending a message produces no assistant reply and no visible error in the UI. The CLI works fine on the same project/provider.

Environment

• OS: Windows 11 Home (Chinese), build 26200, x64
• OpenCode Desktop: 1.18.31 (%LOCALAPPDATA%\Programs\@opencode-aidesktop\OpenCode.exe)
• Provider/model: opencode/big-pickle
• Node: v24.17.0

Steps to reproduce

1. Launch OpenCode Desktop
2. Click "+ New session" in the sidebar (new chat window opens)
3. Type a message and press Enter
4. The user message renders, but the assistant never replies (no output, no spinner, no error)
5. Repeating/sending more messages behaves the same

Actual behavior

• Every request fails with prompt_async failed; the broken sessions get silently archived afterwards.
• A full quit + relaunch does not fix it.

Root cause (from %USERPROFILE%\.local\share\opencode\log\opencode.log)

Every affected session logs the same error:

timestamp=2026-09-17T13:46:20.243Z level=ERROR run=afdd6996 message="prompt_async failed" sessionID=ses_f5061bbc4ffe5iahY9b6Zr7kxy cause="Cause([Die(PlatformError: NotFound: FileSystem.realPath (C:\\Users\\Lenovo\\.local\\share\\opencode\\worktree\\global\\silent-knight) (cause: Error: ENOENT: no such file or directory, lstat 'C:\\Users\\Lenovo\\.local\\share\\opencode\\worktree\\global\\silent-knight'))])"

• C:\Users\Lenovo\.local\share\opencode\worktree\global exists but is empty — the silent-knight worktree dir is missing.
• Log shows 11 FileSystem.realPath errors and 8 prompt_async failed across 3 sessions.
• The project is a non-git folder (uses global workspace scope).

Possible relation

May relate to existing issues about the desktop sidecar being stuck / new sessions not replying: #36061, #37255, #41964.

Full log available at %USERPROFILE%\.local\share\opencode\log\opencode.log if maintainers need the complete excerpt.