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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.

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Claude Code v2.1.234

Another forged control tag is escaped in subagent output

You'll notice
Useful2 Signal3
Subagents

Subagent output that imitates one more internal marker name is now escaped, closing a prompt-injection route.

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.

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 →