You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
SubagentsArea: what it touches
ImprovementsKind: in v2.1.301,
ImprovementsSection of the release
What
A subagent is a separate helper Claude can start to work on part of a task, and it can run in the background. When a session carries over background agents from an earlier session, Claude Code now checks them. Any agent it cannot confirm is marked as failed.
Claude then gets a notice saying the agent was carried into this session and not resumed, because the session could not confirm that its owner launched it and that it is still running. The notice also says that sending the agent a message may continue it.
Why
This affects what Claude is told after you resume a session, or move one to the background, while subagents are still running. Claude learns those agents did not carry on and that it can try messaging one to pick it back up.
