You'll noticeTier: how much it should matter to you
3Useful: my rating, 1 to 5
3Signal: worth watching, 1 to 5
SubagentsArea: what it touches
ImprovementsKind: in v2.1.301,
ImprovementsSection of the release
What
Claude can send messages to other agents, such as subagents (helper agents it starts to work on part of a task). Two cases now behave differently:
A running agent: if the session has no room left, the message is not sent and Claude gets a failure message instead. Before, the message was always queued.
A stopped agent: Claude Code first works out which agent to resume. If that runs into a conflict, it refuses unless the agent belongs to the one asking.
When a stopped agent is resumed, the result now also gives the ID of the agent that was brought back.
Why
In sessions with limited room, Claude may now be told it cannot message or resume an agent, rather than the message being queued anyway.
