You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
3Signal: worth watching, 1 to 5
SubagentsArea: what it touches
ImprovementsKind: in v2.1.234,
ImprovementsSection of the release
What
Output coming back from a subagent is scanned for text that imitates Claude Code's own internal message markers. A new marker name, slack-tag-message, is now on that list and gets escaped rather than passed through, closing one more prompt-injection route.
Details
Sits beside the existing slack-ping marker and is neutralized under the same control-tag handling.
Active wherever subagent output scanning runs; nothing in this build produces messages of that kind, so only the defensive half is present.
Evidence
slack-tag-message
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
