Who Owns This Agent? Tracing AI Agents Back to Their Owners

AI agents increasingly act autonomously in the world, yet harmful behavior cannot be reliably traced to the account that deployed the agent. This creates an accountability gap across both benign and malicious settings: misconfigured or hijacked agents may cause unintended harm, while malicious operators may deploy agents for scams, harassment, or cyberattacks. In many cases, these agents rely on vendor-hosted language models. Affected parties can observe the harm, but cannot identify the responsible vendor session or account. We formalize this problem as agent attribution: linking an observed agent interaction to the account responsible for the underlying model calls. We present a canary-based protocol in which an authorized party embeds selected signals in content consumed by the agent, then asks the vendor to search a narrow time window of account-linked session logs. Lexical canaries provide exact-match attribution when a benign operator does not deliberately evade detection. Against adaptive adversaries, we use task-relevant semantic canaries whose removal or replacement also removes information required for successful task execution, creating a utility--evasion asymmetry. Across communication, web, and cyber-agent settings, we show that the protocol supports reliable session attribution, withstands adaptive transformations, and scales to practical vendor-side log search.