Desktop: parent_message_uuid validation error on fresh chat startup

Description

On first startup of Claude Desktop — fresh open, fresh chat — the app throws a UUID validation error before any conversation begins.

Error

parent_message_uuid: Input should be a valid UUID, in
character: expected an optional prefix of urn:uuid: followed by
[0-9a-fA-F-], found n at 1

The found n at 1 suggests parent_message_uuid is being set to a string like null or none instead of a valid UUID or being omitted entirely.

Environment

• Platform: Claude Desktop (latest version)
• OS: Windows 10/11
• Context: First startup, brand new chat — no prior messages, no conversation history
• Date observed: February 3, 2026

Expected Behavior

A fresh chat should initialize cleanly without any UUID validation errors.

Actual Behavior

UUID validation fails immediately, preventing normal use.

Notes

This is not related to the Cowork/Research mode UUID issues (#18644, #18974, #20016) which involved local_ prefixed session IDs. This occurs in a standard chat session on first open.