API Error: Invalid JSON request body - tool call interrupted

Issue Description

Session becomes unusable after a tool call process is interrupted before the tool response. Every subsequent message returns:

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 412857 (char 412856)"}}

Steps to Reproduce

1. Start a tool call
2. Process gets interrupted/stopped before tool response completes
3. All subsequent messages in the session fail with JSON parsing error

Expected Behavior

Session should recover gracefully from interrupted tool calls or provide clear error recovery mechanism.

Actual Behavior

Session becomes completely unusable, requiring restart.

Impact

Forces users to restart sessions and lose conversation context when interruptions occur.