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DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

All of v2.1.234 Home All releases olderv2.1.233 v2.1.235newer
Claude Code v2.1.234

Background task notifications arrive inside a system-reminder

Under the hood
Useful2 Signal3
Background Tasks

Background task results can no longer fake harness messages by closing the reminder wrapper early.

What

Automated background-task events delivered on your turn are now wrapped in a <system-reminder> envelope, and any closing tag inside the payload is escaped to &lt;/system-reminder&gt; so content coming back from a task cannot close the reminder early and start speaking as the harness.

Details
  • The escape is a case-insensitive global replace over the payload before wrapping.
  • The subagent prompt was updated to match: worker results arrive as user-role messages containing <task-notification> XML, delivered as harness input inside a reminder, and the model is told never to reproduce them in its own output.
  • The multi-agent example transcript now shows the nesting too.
  • Active on this build wherever task notifications are delivered.
Evidence

Worker results arrive as user-role messages containing \<task-notification>\ XML, delivered as harness input, normally inside a \<system-reminder>\ that opens with, <task-notification>

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.234 →