Under the hood
Nested blocked agent chains now properly release their pending callback when unblocked
What
When a chain of blocked, nested agents (agents waiting on each other) gets unblocked, Claude Code now runs a stored callback for that chain via a new releaseNestedChainPark mechanism, then clears the stored callback (nestedChainUnparks) so it isn't run again.
Why
This is internal plumbing for how nested agent chains resume after being blocked. It reduces the chance of a leftover callback firing incorrectly or a chain failing to fully resume.