The New Tier
Lesson 1 of 3 in Reasoning Models in the Landscape.
A few product generations ago, getting an Large language model (LLM) to work through a problem step by step was a prompting trick — you asked for the steps and hoped. Then the behavior was trained in deliberately, and a Reasoning model became a thing you could buy: a model that spends generated tokens on Chain-of-thought (CoT) before committing to an answer. How that training works — reinforcement learning against tasks with checkable answers — is the posttraining story. This module is about what it did to the map.
What it did is this: reasoning became a tier, not a family. You will not find a “reasoning vendor” the way you can find an open-weights vendor. Instead, almost every Model family now documents some way to turn thought on, off, or partway — a mode, a dial, a tagged toggle, or a separately listed variant. The tier reaches all the way down: even small models in the verified snapshot document dual-mode reasoning.
For a navigator, that changes the question. Not “which families reason?” but “what reasoning control does this exact model document, and what style of control is it?” The matrix below is the September 2026 answer — read it for the column structure, not the cell contents, because the cells will churn and the structure will not.
| Family | Documented reasoning control | Control style | Documented on |
|---|---|---|---|
Qwen | Thinking mode on by default, with a tunable | Default-on mode + tunable dial | Qwen3.8-27B model card |
DeepSeek | A “continuously controllable reasoning effort” setting — an integer from 1 to 100 | Continuous dial | DeepSeek-V4.1-Flash model card |
Mistral | Flagship Mistral Medium 3.5 — “our first flagship merged model” — is documented as handling instruction-following, reasoning, and coding with configurable reasoning effort per request | Per-request setting on a merged model | docs.mistral.ai models overview; Mistral Medium 3.5 card |
Phi | Hybrid reasoning in a single model: | Hybrid think/no-think toggle | Phi-4-reasoning-vision-15B model card |
gpt-oss | Adjustable reasoning effort (low/medium/high), with “Full chain-of-thought” access — which the card notes is not intended for end users | Discrete levels | gpt-oss-120b model card |
Claude | “Adaptive” thinking steered by an effort parameter (current lineup) | Adaptive mode + effort parameter | Anthropic model overview docs |
Gemini | The Live API lineup lists an “Extended Thinking” Live variant alongside a default voice model pitched as the “Default Live API model for most low-latency voice agent experiences without reasoning delays” | Separate model variant | Gemini API model docs |
Qwen3-0.6B (SLM) | Documents “seamless switching between thinking mode” and “non-thinking mode” within a single model | Mode toggle — in a sub-1B model | Qwen3-0.6B model card |
SmolLM3-3B (SLM) | “It supports dual mode reasoning” — thinking toggled via | Mode toggle | SmolLM3-3B model card |
Read the matrix twice. The first pass gives you today’s facts. The second pass — the one that lasts — gives you a taxonomy of control styles: a continuous dial, discrete levels, a mode toggle inside one model, a default-on mode with a tunable, and a separately listed variant. Every reasoning control you will meet for the next several release cycles is likely to be one of these shapes wearing a new name. When a card documents something, your job is to classify it, because the classification tells you what you can do operationally: dials and per-request settings mean you can route — choose an effort level for each request — while separate variants mean routing happens at model-selection time instead.
Notice also what the fourth column is doing. Every control is attributed to a specific model card, because that is exactly how the underlying fact base records it — several of its rows carry the hedge “verified for that model only.” Family branding does not transfer: a hybrid think/no-think design documented on one Model card tells you nothing certain about a sibling model, an earlier version, or next quarter’s successor. The per-model discipline is not pedantry; it is what keeps your architecture decisions attached to things that are actually documented.
Key terms: Reasoning model, Chain-of-thought (CoT), Model family, Model card, Model release
Interactive checkpoint quiz (2 questions) — open this page in a browser to take it.