Claude Opus 5 closed last year's SDK gaps — not this year's
A while back I built a small tool called SDKProof. it checks how well an AI coding agent writes an SDK's current API — the stuff that changed in the last major, that the model tends to get wrong because it learned the old version. Claude Opus 5 came out today. so I re-ran the whole board on it. short version: it fixed last year's SDKs. it did not fix this year's. The board, now on Opus 5 Same tasks, same libraries, new model: SDK shipped its major Opus 5 Prisma 7 late 2025 (freshest) 87 Next.js 16 late 2025 92 Vercel AI SDK 7 mid 2025 100 Zod 4 2025 100 TanStack Query 5 2023 100 The way each score works: the model solves ~10–15 real tasks, the code gets type-checked against the real installed package, pass = it compiles. no LLM judging another LLM, the compiler decides. The two that jumped: Vercel AI SDK 7 and Zod 4 were both 90 on the previous model (Opus 4.8). Opus 5 took them to 100. What flipped Here's the kind of thing that changed. Define a tool with the AI SDK. Opus 4.8 wrote it the old (v4) way: const getWeather = tool ({ parameters : z . object ({ city : z . string () }), // renamed to inputSchema execute : async ({ city }) => `...` , }) await generateText ({ model , prompt , tools : { getWeather }, maxSteps : 5 , // removed }) That doesn't compile against ai v7. parameters is now inputSchema , and maxSteps is gone (it's stopWhen: stepCountIs(5) now). Opus 5 writes the current shape by itself: const getWeather = tool ({ inputSchema : z . object ({ city : z . string () }), execute : async ({ city }) => `...` , }) await generateText ({ model , prompt , tools : { getWeather }, stopWhen : stepCountIs ( 5 ), }) Clean compile. same for Zod — Opus 4.8 kept reaching for the removed required_error , Opus 5 writes the new unified error option. What didn't move Prisma 7 and Next 16 barely changed. they shipped their breaking changes most recently, and even the newest model hasn't caught up. Prisma still writes the pre-v7 client setup — it skips the driver adapter that