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Does ChainGuard's defense hold against adaptive attacks?

ChainGuard reduced attack success to 22.5%, but the paper doesn't report whether the attacker refined its strategy specifically against ChainGuard's feedback, as it did against other scanners. Testing against an unadapted attacker gives defenders an unfair advantage.

Synthesis note · 2026-09-23 · sourced from Agents Multi Architecture

The paper's attack is adaptive against the scanners: scanner-feedback refinement keeps lowering each sub-skill's suspicious signals until the chain gets through, for a 96.0 percent mean ASR (see Can attackers evade skill scanners by refining individual skills?). ChainGuard's result is a single number, an ASR reduced "to 22.5%" with 99.5 percent of benign workflows passing (see Does chain-level inspection close the cross-skill attack blind spot?). The excerpt does not say whether the same refinement loop was run against ChainGuard. If it was not, the defense was tested against an attacker tuned to something else, and 22.5 percent is a best case for the defender.

Three readings are open. The figure could hold. A chain-level check may resist the loop because what it inspects is the very thing the loop is built to preserve, the chain's attack semantics, so lowering chain-level suspicion would trade directly against the attack. That is a vault reading; the excerpt does not say what ChainGuard inspects. The figure could rise: if ChainGuard exposes any per-chain signal the attacker can read, the loop has a new objective to optimize. Or the answer could turn on what the defense reveals: a scanner that returns findings gives the loop a signal, and a bare block-or-allow verdict gives it much less.

How to settle it: read the evaluation for whether ColluSkill was run in a ChainGuard-aware variant, what feedback ChainGuard returns to the attacker, and per-round attack success against it. The general expectation is in What makes detecting AI agent traps fundamentally difficult?: each defense will be probed and worked around. The same condition is open on other defense evidence in the vault. Why does compression defense fail at the user prompt boundary? reports a 100 percent compress-stop rate on attack traces that may append by construction. Can monitors catch plan injection attacks in chain-of-thought reasoning? names an attacker searching against a deeper monitor as the risk of its first candidate, and the attack there was itself found by automated investigator agents.

Until then, a post citing 22.5 percent should say that the excerpt does not report whether the attack adapted to ChainGuard.

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Can defenses detect attacks composed across multiple skills? Do multi-agent systems create greater security risks than single-agent ones?

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Original note title

does ChainGuard's reduction hold when the attacker refines against ChainGuard's own feedback — the excerpt reports the reduced attack success without saying the attack adapted to the defense