bug: Win11 generate can fail with raw 'Unexpected end of JSON input' #128

Summary

On Windows 11, generation can fail with a raw main-process IPC error:

Error invoking remote method 'codesign:v1:generate': CodesignError: Unexpected end of JSON input

The error is surfaced directly to the user instead of being translated into an actionable message or recovered gracefully.

Environment

• OS: Windows 11
• App: open-codesign desktop
• Provider/model: unknown from screenshot
• Flow: normal generate via codesign:v1:generate

Repro

1. Open open-codesign on Windows 11.
2. Start a normal generation.
3. The run fails immediately or early in the request lifecycle.
4. A modal appears with:
   Error invoking remote method 'codesign:v1:generate': CodesignError: Unexpected end of JSON input

Actual

• Generation aborts.
• The user sees a raw JSON parse error.
• The UI does not indicate which local file/state is malformed or how to recover.

Expected

• Generate should not expose a raw Unexpected end of JSON input error to end users.
• If a local JSON-backed state file is truncated/corrupt, the app should:
  • detect it,
  • report which state source failed,
  • recover safely when possible, or
  • show an actionable error message (for example: re-login, reset preferences, or repair local state).

Suspected area

This looks like an uncaught JSON.parse failure somewhere on the main-process generate path.

Relevant entry points / likely parse sites:

• apps/desktop/src/main/index.ts codesign:v1:generate
• packages/providers/src/codex/token-store.ts reads persisted ChatGPT Codex auth via JSON.parse
• apps/desktop/src/main/preferences-ipc.ts reads preferences.json
• other local JSON-backed state read during generate/bootstrap

One likely failure mode is a partially written or truncated local JSON file on Windows, with the raw parse error bubbling through IPC.

Why this matters

This is a poor recovery path for a user-visible flow:

• it blocks generation completely,
• the message is too low-level,
• and it gives the user no clue which state file is broken or what action to take.

Suggested fix direction

• Wrap all JSON reads reachable from generate with source-specific error handling.
• Replace raw parse failures with structured CodesignErrors.
• Include the failing store/source in logs.
• Show a user-facing recovery hint instead of the raw parse message.