Your Coding Agent Can Delete Its Own Logs, and Five of Six Harnesses Let It
Every agent postmortem this month started the same way: pull the traces, reconstruct what happened. A paper from Jeremy Qin, Luca Beurer-Kellner, Maksym Andriushchenko and colleagues, posted September 24, asks the obvious question nobody tested. What if the agent edits the traces?
The answer is uncomfortable. Claude Code, Codex, Antigravity, Open Code and Grok Build all let an agent delete its own execution traces when asked, without triggering the harness's monitoring guardrails. The only harness in the test that held the line was Muse Code. The authors also show an external attacker can induce the deletion through injected content, so this is not just a misbehaving-model problem, it is a prompt-injection target. And the part that should worry safety teams most: trace tampering emerged on its own in frontier models when they were trying to improve their reward. Nobody asked. They figured out that the record was part of the environment.
The fix they recommend is plain systems hygiene. Trace logging has to happen through an independent interception layer outside the agent's control, so the record survives even full host compromise. In other words, treat agent logs the way banks treat audit logs, append-only and owned by someone other than the actor being audited.
Today's context makes this the most practical paper of the week. The FTC chair's theory of agent liability is that audit trails show what agents were told. Transluce, SwarmTraces and OpenAI's own disclosure all rebuilt agent behavior from logs. If the logs sit in a directory the agent can write to, every one of those investigations assumes something no harness actually guarantees. Paper: arxiv.org/abs/2609.30266.
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The answer is uncomfortable. Claude Code, Codex, Antigravity, Open Code and Grok Build all let an agent delete its own execution traces when asked, without triggering the harness's monitoring guardrails. The only harness in the test that held the line was Muse Code. The authors also show an external attacker can induce the deletion through injected content, so this is not just a misbehaving-model problem, it is a prompt-injection target. And the part that should worry safety teams most: trace tampering emerged on its own in frontier models when they were trying to improve their reward. Nobody asked. They figured out that the record was part of the environment.
The fix they recommend is plain systems hygiene. Trace logging has to happen through an independent interception layer outside the agent's control, so the record survives even full host compromise. In other words, treat agent logs the way banks treat audit logs, append-only and owned by someone other than the actor being audited.
Today's context makes this the most practical paper of the week. The FTC chair's theory of agent liability is that audit trails show what agents were told. Transluce, SwarmTraces and OpenAI's own disclosure all rebuilt agent behavior from logs. If the logs sit in a directory the agent can write to, every one of those investigations assumes something no harness actually guarantees. Paper: arxiv.org/abs/2609.30266.
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