Parent metadata can arrive while a child document is still loading, replacing its URL with the parent URL and aborting navigation. Preserve the requested child slug until child details arrive, while continuing to update the parent’s canonical path and history.

Added a browser regression that holds the child request, renames the parent through the real API/WebSocket, and checks the canonical child URL and mounted document. It fails before the fix and passes afterward.

Validation: focused browser regression passed independently three times; original parent/child source-range case, nine route units, build, types, and CI checks pass. The existing design exception hash was refreshed with its cases and reason unchanged.

The child document remains open after the parent rename: