Partly: in 4 runs, Claude Opus 5's langchain attribution reaches 1.0.0 (2025-10-17), inside langchain 1, and stops there — langchain was at 1.4.0 when this index last verified against it (2026-09-06). That is ~7 months below the training cutoff the subject stated in those runs (2026-05). 6 findings are currently charged against Claude Opus 5 on langchain (3x S2 silently-wrong, 2x S3 deprecated, 1x S4 wrong-metadata), each reproduced in a published run and checked against langchain's own release notes. Read the boundary precisely: it is the newest release whose contents the model can correctly attribute to that release, not the newest langchain 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 inside, decided by one rule applied to every page
of this kind: every measured boundary is at or above 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 |
|---|---|---|---|
| v1 2026-08-31 | 1.0.0 2025-10-17 |
1.1.0 2025-11-24 |
~7 months |
| v5-c 2026-09-06 | 1.0.0 2025-10-17 |
1.1.0 2025-11-24 |
~7 months |
| v6-a 2026-09-06 | 1.0.0 2025-10-17 |
1.1.0 2025-11-24 |
~7 months |
| v6-b 2026-09-06 | 1.0.0 2025-10-17 |
1.1.0 2025-11-24 |
~7 months |
2 further runs of this pair established only one end of the interval, or measured the instrument rather than the library; they are listed under Runs below.
4 measurements 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.
langchain published 3 minor or major releases in the twelve months before this model’s stated cutoff, which is the scale a spread should be read against.
“Chargeable” means the change was published before this model’s own stated cutoff, so it had the opportunity to know it.
| Severity | Belief | Changed in | Chargeable | Proof |
|---|---|---|---|---|
| S2silently-wrong | States that the bare model-retry middleware re-raises when retries run out; the shipped default returns an AIMessage and the agent carries onModelRetryMiddleware defaults |
1.1.0 2025-11-24 |
yes | run · source |
| S2silently-wrong | States the agent's step ceiling is LangGraph's 25 and prescribes raising it; create_agent has set a four-figure limit since 1.1.0create_agent recursion limit |
1.1.0 2025-11-24 |
yes | run · source |
| S2silently-wrong | Invents tool.provider_specific for per-tool provider parameters; the shipped attribute is extrastool extras |
1.2.0 2025-12-15 |
yes | run · source |
| S3deprecated | Writes middleware against ModelRequest.system_prompt; the field was renamed to system_message in 1.1.0 and the string route is a documented deprecationModelRequest.system_message |
1.1.0 2025-11-24 |
yes | run · source |
| S3deprecated | Denies that a LangChain tool has any place of its own for provider-specific fields, then rebuilds the tool definition by hand — the verdict, the artefact and the attribution all wrong in the same direction@tool(extras={...}) |
1.2.0 2025-12-15 |
yes | run · source |
| S4wrong-metadata | Version knowledge stops at 1.0.0 while 1.1.0 and 1.2.0 shipped inside its window | 1.1.0 2025-11-24 |
yes | run · source |
The langchain 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 langchain 1 best?
Other subjects on langchain:
Claude Opus 5 on the other libraries: