Topic
Divergence between a backend's response schema and downstream consumers' hand-maintained copies of that schema, and mechanisms that make the divergence fail loudly.
Meta stops returning three Delivery Estimate fields on all Marketing API versions, pinned and unversioned, on October 27. The endpoint keeps answering 200, so forecasting code reads nulls and raises no error.
Reality
A new zero-dependency CLI reads a Python codebase with the standard library and reports spec-only, code-only and method-mismatch paths, exiting 0 every time so the question of which drift fails a build stays with the team.
Reality
In a dev.to sample the same restaurant search tool is described once in a C# attribute and twice in Bicep, and two of the copies already disagree after two days of editing. The author's argument is that the description is the API contract now.
Reality
The endpoint keeps returning 200 with valid JSON, so release tooling reads an absent field and carries on. Pinning the version header defers that work rather than removing it, and the deferral has a date on it.
Reality
A hand-written TypeScript copy of a Pydantic schema kept the compiler happy and the data wrong. The durable fix was deleting the copy and generating the contract from the backend.
Reality