What
A subagent is a helper that Claude starts to handle part of a task on its own. In some sessions, Claude Code cannot work out which folder the subagent should work in. It now refuses to start the subagent there, and Claude is told: "A subagent cannot be started from here in this session. Do the task without a subagent." Claude Code also records the failed launch.
Why
Claude gets a clear refusal it can act on and carries on with the task itself. Without the check, the subagent may have run in the wrong folder.
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
It is not clear which kinds of session end up without a folder to give a subagent.