215 keys vanished from OpenAI, Anthropic and Groq OpenAPI specs with no version record

215 keys are gone from the published specs

A long-running diffing effort published on dev.to has quantified how quietly the machine-readable API specifications of OpenAI, Anthropic and Groq change underneath developers. The author, posting as AI ChangeWatch, snapshotted the three vendors' published OpenAPI files over time and kept every key that ever appeared: 2,802 operations, parameters, enum variants and beta markers in total. Of those, 215 are no longer in the current files — 157 parameters, 29 enum variants, 27 whole operations and 2 beta markers — and, according to the post, nothing in the specs themselves records that any of them existed.

Most removals are old, but 33 lasted a single day

The lifespans skew long: 76 of the removed keys had been in the specs for over a year and 87 for under a year, while 17 lasted less than 30 days. The outlier is the final group — 33 keys whose first and last observed appearance fell on the same day, plus two rows the author excluded as a defect in their own collection.

The largest single-day cluster hit OpenAI on 22 March 2025, when the spec briefly gained four operations managing fine-tuning checkpoint permissions along with their ten parameters. The post notes the paths were internally inconsistent — three keyed the permission collection on {permission_id} while a fourth keyed the same collection on the checkpoint — and none of the fourteen keys survived to the next capture.

Short-lived keys touch endpoints people actually call

Several transients sat on core endpoints. OpenAI's POST /chat/completions carried an instance_id parameter on 9 February 2024 and on no other day in the collection. POST /responses listed computer-preview as a tools[] variant on 11 March 2025 only. Anthropic's POST /v1/messages exposed a user_profile_id parameter for 67 days, from 16 April to 22 June 2026 — long enough, the post points out, that a client generated in May would still ship a field that no longer exists upstream. Six of Anthropic's /v1/environments operations carried a sessionKey parameter on 8 April 2026 and lost it the next day. The author writes that what these were for is unknown; what can be said is that they were in the published document and then were not.

A missing key is not always a deprecation

The post is careful about what removal means. In one clear case, three tool_choice enum variants (auto, any, tool) stopped appearing in Anthropic's spec on 3 October 2024 because the schema moved those values behind a $ref, not because the API changed — tool_choice: auto still works. Whole operations disappearing are treated as the most reliable signal, and even there, OpenAI's six Assistants file endpoints vanishing on 15 April 2024 matches the documented v2 migration rather than a silent change.

The deeper problem is that the spec is not a record of itself. The current file cannot tell you when user_profile_id first appeared, and the changelog had no entry for it.

Pin the spec, date the client

The author's recommendations are cheap. Vendor the spec file into your repository with a hash and diff it on a schedule instead of trusting the live URL; every finding in the post is a diff someone could have had for free, and the only reason the author has them is that nobody else kept the old copy. Treat generated clients as snapshots with a date on them. And be wary of any capability that shows up in the spec but in no changelog, documentation or release note — fourteen of OpenAI's did not survive the day.

The comparison covers only three vendors — OpenAI with 1,605 tracked keys, Anthropic with 1,069 and Groq with 128 — because they are the ones publishing a spec at a stable URL. First-seen dates are a floor rather than an introduction date for 153 keys that were already present in the earliest capture.

Why it matters

OpenAPI specs function as contracts: client generators, SDK tooling and CI checks are built on the assumption that the file is stable and authoritative. This data shows it is neither versioned nor self-documenting, and that vendors routinely publish keys — including on flagship endpoints like chat completions — that vanish without any changelog entry. For anyone generating API clients, the failure mode is silent: an SDK keeps compiling with fields the upstream API no longer advertises, and nothing warns you. A scheduled diff of a vendored spec turns that invisible drift into a reviewable change at essentially zero cost.