Mistral Medium 3.5: The New Reference Model

Updated November 2, 2026. Mistral Medium 3.5 is no longer the reference model: it was deprecated on October 31, 2026 and will be removed on April 30, 2027, in favor of Mistral Large 4 (mistral-large-4), in public preview since October 6 (lesson 10).

Announced on May 22, 2026, Mistral Medium 3.5 (version 26.04) is the model official documentation presents as Mistral’s frontier model. Three characteristics define its positioning: it is multimodal, optimized for agentic use cases, and specifically targets code. In other words, when you ask yourself “which Mistral model for my demanding task?”, the default answer has changed names—and this lesson explains what that implies concretely for your existing projects.

A Clear Positioning: Agents and Code

The official documentation, accessed on July 28, 2026, is brief, but every line counts.

The most revealing detail does not appear in this table but in the announcement itself: Mistral explicitly links Medium 3.5 to remote coding agents. These are scenarios where an agent works on a code repository autonomously—it reads the code, plans modifications, executes them, checks the result, and starts over. This type of workload requires a model capable of sustaining long reasoning, chaining tool calls, and staying reliable over dozens of steps. This is precisely why Medium 3.5 is not presented as “a smarter chatbot” but as the engine for agentic use cases. The “OPEN” mention also deserves your attention: even the frontier model retains open weights, which remains a strong hallmark of Mistral’s strategy.

What This Replaces in Your Mental Model

If you followed our courses written in the spring, your reference was Medium 3, and “Mistral Large 2” still appeared in some comparisons. The hierarchy has reorganized, and it is worth restating it clearly. Medium 3.5 is now the model highlighted for demanding use cases: it occupies the place Medium 3 held a few months ago. Large 3 (v25.12) still exists, but its role is different: it is the cutting-edge open-weight generalist, the one you choose first when you want to host it yourself—lesson 3 covers this. As for mentions of “Mistral Large” without a version number that you might still encounter in our older courses, they refer to the previous generation: read them as historical markers, not as usage recommendations.

Access: The Mechanics Haven’t Changed, Only the Name

The good news for your integrations: the way to call the model has not changed. The Mistral API still exposes its chat completions, Mistral AI Studio remains the experimentation space, and Le Chat covers consumer usage. Concretely, migrating to Medium 3.5 comes down to a single line in your code—the model parameter.

from mistralai.client import Mistral

client = Mistral(api_key=api_key)

response = client.chat.complete(
    model="mistral-medium-latest",
    messages=[{"role": "user", "content": "Summarize this document in five points."}],
)
print(response.choices[0].message.content)

This code calls the alias mistral-medium-latest, which automatically follows the most recent version of the model. During exploration, this is exactly what you want: you benefit from improvements without touching the code. In production, it is the opposite: a silent model update can change the style, length, or format of responses, and break downstream parsing without any line of your code having moved. So pin a dated version to guarantee reproducibility—the advice has not changed since our other courses, and it applies to all models in the range. The rule of thumb for the exact identifier: check the official models page, which lists the API name and version for each.

If you are already using Medium 3 in production, take advantage of this lesson to audit your setup: identify every place where the model identifier appears in your code or configuration, and note which ones use a -latest alias—these are the ones that may have already switched to Medium 3.5 without you deciding it.

Official source: docs.mistral.ai — Models Overview

Key Takeaways

• Medium 3.5 (v26.04) is the frontier model highlighted since May 22, 2026
• Multimodal, oriented towards agents and code, open weights
• The announcement explicitly links it to remote coding agents
• Large 3 remains the open-weight generalist; “Mistral Large 2” is the previous generation
• In production, pin a version rather than a -latest alias