Mistral AI · 2026-04-29 · major
Mistral Medium 3.5 — 128B Open-Weight Flagship Hits 77.6% on SWE-Bench Verified
Mistral Medium 3.5 — 128B dense open-weight model, 256k context, 77.6% on SWE-Bench Verified and 91.4 on τ³-Telecom. Ships with Vibe Remote Agents (async cloud coding agents) and Le Chat Work mode. $1.5/$7.5 per MTok via API.
Mistral's new flagship: 128B dense, 256k context, open weights under modified MIT, and a 77.6 SWE-Bench Verified score.
Key specs
| Parameters | 128B dense |
|---|---|
| Context window | 256k |
| Price (input) | $1.5/MTok |
| Price (output) | $7.5/MTok |
| SWE-bench | 77.6% |
| Τ³ telecom | 91.4 |
What is it?
Mistral Medium 3.5 is the newest dense flagship model from Mistral AI, released April 29 with open weights on Hugging Face under a modified MIT license. The same launch ships Vibe Remote Agents — async coding agents that run in cloud sandboxes — and a new Work mode for Le Chat. Mistral Medium 3.5 becomes the default model in both Le Chat and the Vibe CLI.
How does it work?
The model is 128B dense parameters with a 256k-token context window, trained for instruction-following, reasoning, and coding. Vibe Remote Agents launch from the Vibe CLI or Le Chat into isolated cloud sandboxes, run in parallel, and integrate with GitHub, Linear, Jira, Sentry, Slack, and Teams. A local Vibe session can be 'teleported' to the cloud mid-task. API pricing is $1.5 per million input tokens and $7.5 per million output tokens.
Why does it matter?
The 77.6% SWE-Bench Verified score puts an open-weight 128B dense model into the same coding-tier conversation as much larger closed flagships. Combined with remote agent infrastructure, Mistral now ships an end-to-end coding-agent stack — model, CLI, cloud orchestration — under permissive open weights. Teams that want a self-hostable alternative to Claude/Codex with first-party agent tooling now have one.
Who is it for?
Teams running self-hosted coding agents and developers wanting open-weight SWE-Bench-tier models
Try it
huggingface.co/mistralai/Mistral-Medium-3.5-128B