Plain layer · ten-second read
When a model changes, will the provider not just tell you in a changelog or model card? Sometimes, eventually, in their words, on their schedule, for the changes they choose to disclose. A provider changelog is the vendor describing their own product. An independent record is an outside party measuring the served behavior and sealing every reading into an append-only, hash-chained record that cannot be quietly rewritten. One is the interested party's account; the other is evidence. Read the changelog for intent, keep the record for proof.
The distinction
A provider changelog or model card is authored by the provider, published when and if they choose, in prose they control, covering what they decide to mention. It tells you what they say changed. An independent record is measured from outside by one frozen protocol, on a fixed schedule, written into an append-only, hash-chained record, covering behavior whether or not anyone announced it. It tells you what actually moved, when, on the record.
Side by side
| Provider changelog | Independent record | |
|---|---|---|
| Who writes it | the provider, the interested party | an outside witness |
| When | when they choose | on a fixed schedule |
| Covers unannounced or silent changes | no | yes |
| Can be edited without trace | yes, by the author | no, append-only and hash-chained |
| Usable as third-party evidence | no | yes |
| Tells you intent and reason | yes | no, it detects, it does not explain intent |
Why the changelog cannot be the evidence
Three structural reasons. Coverage: a changelog lists only the changes the provider chose to announce, so silent serving swaps and quiet behavioral drift, the ones that hurt you, are exactly what it omits. Authorship: it is written by the party with the incentive, so for an auditor or a customer it is not independent evidence. Mutability: prose on a vendor page can be revised, and there is no external timestamp proving what it said and when, whereas an append-only, hash-chained record cannot be quietly rewritten; external timestamping, which is being added, will prove the dates without trusting the witness either.
Where they meet
They are complementary. Read the changelog for intent and context; keep the independent record for proof and for the changes the changelog does not mention. When the two agree, you have both the reason and the evidence. When the record shows a change the changelog does not, you have caught a silent one.
Technical layer · rigor intact
A changelog is unversioned, mutable prose published at the author's discretion. The record is a fixed measurement: one frozen protocol, readings coded by a deterministic parser, changes published only when confirmed and reproduced past a pre-registered floor, each reading written into an append-only hash chain, with external timestamping (OpenTimestamps anchoring) being added so the dates verify without trusting the bureau. States and dated evidence, never adjectives, and never a claim the record cannot support.
Common questions
Is a version number not enough?
A version bump says something changed, not what behavior moved, and many serving changes ship without one. The record measures the behavior regardless of whether a number changed.
What if the provider is trustworthy?
Independence is not an accusation. An auditor cannot accept the interested party's own notes as evidence however trustworthy the party, and silent changes are often unintentional on the provider's side too.
Does this compete with the provider?
No. It measures the served endpoint from outside and takes no payment from the providers it measures. The changelog and the record answer different questions.