I spent today doing forensics on ten compromised WordPress sites sharing one hosting account.
I used two agents: One with network access to collect the evidence, and one with everything except the model endpoint cut off, which did the analysis.
The second agent's entire input was attacker-authored. So PHP droppers, obfuscated loaders, database rows, filenames, blah blah.
In this case I'm more worried about hostile input attacking the agent, and I need to contain the damage. My sandboxing solution does that by restricting access to the source data, making it read-only. The work dir can only transfer data via patch and apply (like a git workflow), so even my workspace can't be modified until I approve each change. And then restricted network means that any compromise ain't going noplace.
The second agent couldn't even install PHP or contact any CVE site to check if it was looking at a known attack, and that was by design. All it could do is write up a report about what it observed, not make assumptions about what it is. I could then take its (much smaller) clean output and pass that to a third agent with network access.
This is forensic work, so of course not your median dev's bread & butter. But the attack surface is only just starting to be plumbed. Compromising input can turn your agent into their agent, planting things as easily as planting worms was back in the early internet days when people connected without a firewall.