[BUG] Windows MSIX: node-pty fails to spawn shell — 'Error: File not found:' in windowsPtyAgent.js (terminal panel broken)

Environment

• Claude version: 1.4758.0.0 (MSIX, x64, Windows Store / winget)
• OS: Windows 11
• Git Bash: C:\Program Files (x86)\Git\bin\bash.exe

Problem

The terminal panel in the Claude desktop app fails to spawn any shell (PowerShell or bash). Clicking the terminal button does nothing visible — no panel opens.

Exact error from %APPDATA%\Roaming\Claude\logs\main.log

2026-04-25 21:54:46 [info] LocalSessions.startShellPty: sessionId=local_4bfcaafa-ae6b-4681-bcd9-eeab7eb9f792, cols=60, rows=49
2026-04-25 21:54:46 [error] Failed to spawn shell powershell.exe for session local_4bfcaafa-ae6b-4681-bcd9-eeab7eb9f792 {
  error: Error: File not found:
      at new WindowsPtyAgent (C:\Program Files\WindowsApps\Claude_1.4758.0.0_x64__pzs8sxrjxfjjc\app\resources\app.asar\node_modules\node-pty\lib\windowsPtyAgent.js:81:36)
      at new WindowsTerminal (C:\Program Files\WindowsApps\Claude_1.4758.0.0_x64__pzs8sxrjxfjjc\app\resources\app.asar\node_modules\node-pty\lib\windowsTerminal.js:51:24)
      at spawn (C:\Program Files\WindowsApps\Claude_1.4758.0.0_x64__pzs8sxrjxfjjc\app\resources\app.asar\node_modules\node-pty\lib\index.js:29:12)
      at cTn.startShellPty (C:\Program Files\WindowsApps\Claude_1.4758.0.0_x64__pzs8sxrjxfjjc\app\resources\app.asar\.vite\build\index.js:6177:7690)
      at async Object.startShellPty (...index.js:6303:6744)

The error File not found: has an empty path — meaning the file argument passed to WindowsPtyAgent is empty string or unresolvable.

Key observations

• app.asar.unpacked\node_modules\node-pty\build\Release\ exists and contains all expected files: conpty.node, conpty_console_list.node, pty.node, winpty-agent.exe, winpty.dll
• The binaries are correctly unpacked — the issue is path resolution inside the asar, not missing files
• powershell.exe is accessible: C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe exists and is in PATH
• Terminal worked correctly on 2026-04-19 and 2026-04-20 (confirmed in main.log via successful startShellPty entries with no errors)
• Broke on 2026-04-25 — likely after an auto-update or Windows Update between those dates
• Force-reinstall via winget install Anthropic.Claude --force did not fix the issue

Hypothesis

windowsPtyAgent.js:81 resolves the shell/agent path using __dirname or a related construct. Inside the MSIX-packaged .asar, __dirname may resolve to the virtual asar path rather than the real filesystem path — making the constructed path to either winpty-agent.exe or the shell executable empty/invalid. Electron's asar path remapping works for require() but not for explicit path.join(__dirname, ...) + fs.existsSync() usage.

This is regression — it worked previously on the same machine and same MSIX packaging model.

Related issues

• #41546 — spawn UNKNOWN on LocalSessions start
• #51886 — CLAUDE_CODE_GIT_BASH_PATH not reaching MSIX child process

Additional context

Also present (but separately fixed by clearing Windows ReadOnly attribute from ~/.claude subtree):

• EEXIST: file already exists, mkdir 'C:\Users\marcu\.claude\plugins\data\context-mode-context-mode' on every SessionStart/PostToolUse hook — caused by ReadOnly attribute on ~/.claude/plugins and ~/.claude/session-env directories (13 000+ subdirs affected)