Mistral Medium 3.5 128B Released: Dense Model with Configurable Reasoning and Vision
Mistral AI has released Mistral Medium 3.5 (128B), a dense transformer model that replaces Mistral Medium 3.1 and Magistral in Le Chat, and Devstral 2 in their coding agent Vibe. It's a single set of weights handling instruction-following, reasoning, and coding.
Key Features
- Dense 128B parameters — not Mixture of Experts.
- 256k context window for long inputs.
- Multimodal input: accepts text and images; outputs text only. Vision encoder trained from scratch to handle variable sizes and aspect ratios.
- Configurable reasoning effort: toggle per request between instant reply (
none) and deep reasoning (high). - Native function calling and JSON output for agentic workflows.
- Multilingual: supports English, French, Spanish, German, Italian, Portuguese, Dutch, Chinese, Japanese, Korean, Arabic, and others.
- Strong system prompt adherence.
Recommended Settings
- Reasoning effort:
nonefor quick replies;highfor complex prompts and agentic usage (e.g.,reasoning_effort="high"). - Temperature: 0.7 with
highreasoning; 0.0–0.7 withnonedepending on desired creativity.
License
Released under a Modified MIT License — open-source for commercial and non-commercial use, with exceptions for large revenue companies.
GGUF Quantizations Available
Unsloth has published a GGUF version on Hugging Face: unsloth/Mistral-Medium-3.5-128B-GGUF
This model is relevant for developers running local AI coding agents, particularly those needing high-quality instruction following, reasoning, and vision in a single dense model with a large context window.
📖 Read the full source: r/LocalLLaMA
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