[Bug] Session state mismatch: CLI reports running but browser shows "session could not be found"

Bug Description
Ultraplan stated the session is running, but when I open it in the browser it says "This session could not be found".

Environment Info

• Platform: win32
• Terminal: vscode
• Version: 2.1.119
• Feedback ID: 8919548f-dc18-43f8-bc63-ebac1ac092b9

Errors

[{"error":"Error: File does not exist. Note: your current working directory is C:\\Users\\iangr\\src\\sandbox-runtime.\n    at call (B:/~BUN/root/src/entrypoints/cli.js:4858:7647)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-25T15:58:18.815Z"},{"error":"ZC_: Diagnostics file path mismatch: expected C:\\Users\\iangr\\.claude\\plans\\woolly-imagining-minsky.md, got file://c:\\users\\iangr\\.claude\\plans\\woolly-imagining-minsky.md/)\n    at beforeFileEdited (B:/~BUN/root/src/entrypoints/cli.js:4885:23524)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-25T16:21:04.976Z"}]