Mistral Medium 3.5 Review: A 128B Open-Weight Model With a Coding Agent That Opens PRs For You

TL;DR: Mistral Medium 3.5 is a 128B open-weight model released April 29, 2026, with a 256K context window, configurable reasoning, and native multimodal input. It scores 77.6% on SWE-Bench Verified — close but not ahead of Claude Sonnet 4.6 — and ships alongside Vibe, a cloud coding agent that submits pull requests directly to GitHub without you babysitting it. API pricing is $1.50 per million input tokens. Open weights under a modified MIT license that routes high-revenue enterprises through Mi