Not by version attribution: in 1 run, Claude Sonnet 5 places its react-router boundary at 7.0.0 (2024-11-22) — below react-router 8.0.0 (2026-06-17), the first release of react-router 8. That is ~13 months below the training cutoff the subject stated in those runs (2026-01). No finding is currently charged against Claude Sonnet 5 on react-router: every probe in the 1 run published here passed, which is a result rather than an absence of testing. Read the boundary precisely: it is the newest release whose contents the model can correctly attribute to that release, not the newest react-router feature it can use. Past it a model often writes working code with a newer API while naming the wrong release for it.
Answer class below, decided by one rule applied to every page
of this kind: every measured boundary is below the first release of the major named in the question. Every figure below is read from
the dataset at build time; nothing on this page is written by hand.
| Battery | Newest release it can place | Oldest it cannot | Lag vs stated cutoff |
|---|---|---|---|
| v2-c 2026-09-10 | 7.0.0 2024-11-22 |
7.1.0 2024-12-20 |
~13 months |
One measurement of this pair, all giving the same boundary. No two of them were drawn from an identical prompt, so the spread mixes prompt differences with draw variance.
react-router published 12 minor or major releases in the twelve months before this model’s stated cutoff, which is the scale a spread should be read against.
Nothing is charged. Every probe in the runs below passed, which this index publishes the same way it publishes a failure.
The react-router correction pack states what is true now for each corrected fact, with a primary-source citation, as markdown you can paste into a rules file (raw). What a correction pack measurably changed when one was tested — a pre-registered run on zod — is on the benchmark page, including where it changed nothing.
All of them at once: Which Claude model knows react-router 8 best?
Other subjects on react-router:
Claude Sonnet 5 on the other libraries: