Under the hood
Fork-worker agents no longer show up as killable background tasks or as SendMessage handback targets
What
Agents marked with forkWorker === true are now explicitly excluded from several checks that decide whether an agent counts as a visible, killable background task, or as a candidate for handing control back to a parent agent via SendMessage.
Why
This keeps internal fork-worker agents out of the background-task list and controls meant for regular agents, so users only see and manage the agents they'd actually expect to.
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Anthropic's release notes agree
Fixed cross-session messages held by the receiving session's permission-mode policy leaving no trace: headless senders now get a delivery…