[BUG] Dispatch session permanently broken after fetching Dropbox image - "no low surrogate in string" API Error 400

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Environment:

• Claude Desktop App (Dispatch/Cowork mode)
• Version: 1.1348.0 (efa3fd)
• Device: Mac mini M4
• OS: macOS

What happened:
During a Dispatch session, I instructed the agent to fetch images from Dropbox inbox. After the agent retrieved the images, every subsequent message returns a permanent API 400 error:

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"The request body is not valid JSON: no low surrogate in string: line 1 column 92098 (char 92097)"}}

The error is fixed at the same character position (92097) regardless of what I type, indicating the corrupted data is stored server-side in the session context.

Steps to reproduce:

1. Open Dispatch session
2. Instruct agent to fetch images from Dropbox
3. Agent processes images and adds them to context
4. Every subsequent message returns the above error permanently

What I tried:

• /clear command → no effect
• Restarting Claude Desktop → no effect
• Restarting Mac → no effect
• The session is unrecoverable

Expected behavior:
Session should remain functional, or at minimum /clear should be able to reset the corrupted context.

Related issues: #39580, #16294

What Should Happen?

Environment:

• Claude Desktop App (Dispatch/Cowork mode)
• Version: 1.1348.0 (efa3fd)
• Device: Mac mini M4
• OS: macOS

What happened:
During a Dispatch session, I instructed the agent to fetch images from Dropbox inbox. After the agent retrieved the images, every subsequent message returns a permanent API 400 error:

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"The request body is not valid JSON: no low surrogate in string: line 1 column 92098 (char 92097)"}}

The error is fixed at the same character position (92097) regardless of what I type, indicating the corrupted data is stored server-side in the session context.

Steps to reproduce:

1. Open Dispatch session
2. Instruct agent to fetch images from Dropbox
3. Agent processes images and adds them to context
4. Every subsequent message returns the above error permanently

What I tried:

• /clear command → no effect
• Restarting Claude Desktop → no effect
• Restarting Mac → no effect
• The session is unrecoverable

Expected behavior:
Session should remain functional, or at minimum /clear should be able to reset the corrupted context.

Related issues: #39580, #16294

Error Messages/Logs

Steps to Reproduce

Environment:

• Claude Desktop App (Dispatch/Cowork mode)
• Version: 1.1348.0 (efa3fd)
• Device: Mac mini M4
• OS: macOS

What happened:
During a Dispatch session, I instructed the agent to fetch images from Dropbox inbox. After the agent retrieved the images, every subsequent message returns a permanent API 400 error:

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"The request body is not valid JSON: no low surrogate in string: line 1 column 92098 (char 92097)"}}

The error is fixed at the same character position (92097) regardless of what I type, indicating the corrupted data is stored server-side in the session context.

Steps to reproduce:

1. Open Dispatch session
2. Instruct agent to fetch images from Dropbox
3. Agent processes images and adds them to context
4. Every subsequent message returns the above error permanently

What I tried:

• /clear command → no effect
• Restarting Claude Desktop → no effect
• Restarting Mac → no effect
• The session is unrecoverable

Expected behavior:
Session should remain functional, or at minimum /clear should be able to reset the corrupted context.

Related issues: #39580, #16294

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude 1.1617.0 (8d6345) 2026-04-09T16:10:15.000Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_