Oversized chat image causes persistent provider error loop in the affected conversation #314

Summary

Adding an image to a chat caused a provider error. The user is stuck in a repeating error loop in the chat containing the image and cannot continue that conversation. Unrelated chats are not affected.

Environment

• Version (kit --version): kit 0.2.20
• OS / architecture: macOS (Darwin arm64)
• Surface: acp (from the fatal log)
• Specific ACP host, model, image dimensions, and image format: not yet captured

Reported reproduction

1. Add an image to a chat.
2. Encounter the provider error below.
3. Attempt to continue the chat containing the image.
4. The error repeats and prevents that conversation from continuing. Other chats remain usable.

This report records the user's observed behavior; an independent reproduction has not yet been established.

Actual behavior

loop error: provider error: Responses image dimensions are too large; fatal log: ~/.kit/errors/s-1793235864568-63251-1/e-1793313023378-2665-3.json

Fatal log (home-directory path abbreviated above):

{
  "schema_version": 2,
  "event_id": "e-1793313023378-2665-3",
  "occurred_at_ms": 1793313023378,
  "kit_version": "0.2.20",
  "session_id": "s-1793235864568-63251-1",
  "surface": "acp",
  "kind": "provider",
  "code": "provider_error",
  "message": "provider request failed"
}

The structured log only records a generic failure, while the visible error identifies excessive image dimensions.

Expected behavior

• Validate or resize images before submitting them when provider dimension limits apply, or reject the attachment with an actionable error.
• Provide a way to remove or replace the offending attachment and continue the affected chat without repeatedly resubmitting an invalid image.
• Preserve the actionable provider error in diagnostic logs, without exposing image contents or sensitive data.

Impact

The conversation containing the image is blocked by the persistent error loop. Unrelated chats are not affected.