# Reasoning Models - Vendor Capability Matrix | Loop Engineering [← All matrices](/matrices/) # Reasoning Models - Vendor Capability Matrix Chapter 5 of Loop Engineering argues the prefrontal cortex layer runs two loops: a deliberation loop (reasoning models) and a critical-thinking loop (metacognition). This matrix tracks the deliberation-loop side: which vendors expose what, and where the architecturally-relevant deltas sit. Refreshed quarterly; next review 2026-09. Verified 2026-06. The reasoning-model surface changes faster than print can keep up - treat any row older than six months as a snapshot and consult the linked vendor docs. ### The matrix Model family Visible chain Thinking budget control Cost vs flagship non-reasoning Faithfulness caveat Materiality fit Verified OpenAI o-series o1, o3, o4 lineage Summary only (the full internal chain is hidden by API design). reasoning.effort parameter (low / medium / high) and reasoning-token budget. Higher per-call cost; reasoning tokens billed separately. Vendor does not publish a formal faithfulness claim for the visible summary; treat as a presentation layer. Medium to high stakes. 2026-06 DeepSeek R-series R1, R1-Distill Full visible chain in the API and chat surfaces. Implicit via prompt-side controls; full chain is always emitted. Open weights; self-hosted cost dominates. Chain is what the model produced; published in the R1 paper alongside training recipe. Medium to high stakes; research and audit-heavy contexts. 2026-06 Anthropic Claude extended thinking Sonnet / Opus extended thinking Visible thinking blocks in API and chat (when enabled). Thinking-budget tokens are an explicit parameter on the request. Higher cost when extended thinking is enabled; off by default. Vendor-published explicit caveat: visible thinking is not guaranteed to be a faithful trace of the model's actual computation. See [launch post](https://www.anthropic.com/news/visible-extended-thinking). Medium to high stakes; verifiability-sensitive work. 2026-06 Google Gemini thinking modes Flash Thinking, 2.5 Thinking lineage Visible thinking summaries in surfaces; API surface varies by model and tier. Per-model "thinking config" controls; consult [Gemini API docs](https://ai.google.dev/gemini-api/docs) for current parameters. Varies by tier; thinking variants are typically billed above non-thinking flagships. Treat visible thinking as presentation-layer unless Google publishes a formal faithfulness claim. Medium stakes; product-integration contexts. 2026-06 OpenAI GPT-5 reasoning modes unified reasoning-capable family Summary only; full chain hidden by API design (consistent with the o-series convention). Effort dial and per-call reasoning budget; surface details consolidating across OpenAI's reasoning offerings. Tier-dependent; reasoning calls billed at the higher tier. No formal faithfulness claim published for the visible summary. Medium to high stakes. 2026-06 ### What the columns mean - Visible chain - does the API or chat surface return the actual reasoning steps the model generated, or just a summary the vendor prepared from them? Architecturally relevant because the visible chain is what the critical-thinking loop has to work with. - Thinking budget control - can the caller bound how much reasoning is done? Materiality calibration depends on being able to dial this. - Cost vs flagship non-reasoning - reasoning calls are not free. Materiality budgets get burned on the wrong tier without explicit dial-down. - Faithfulness caveat - is the visible chain guaranteed to reflect what the model actually did? Anthropic is the only major vendor that has published an explicit "no" so far; others are silent, which means "treat as presentation layer until shown otherwise." - Materiality fit - recommended [materiality-dial](/materiality/) range for this model class, given cost and caveat profile. ### The faithfulness caveat in plain text The visible thinking trace is what the model emitted as thinking; it is not necessarily what the model actually used to produce the answer. This matters when you are auditing the reasoning to decide whether to trust the result. A visible chain that looks rigorous can still be window-dressing on a different underlying computation. Anthropic's [extended thinking launch](https://www.anthropic.com/news/visible-extended-thinking) says this explicitly. Other vendors' silence on this point is not the same as saying their visible thinking is faithful. Architectural implication: the critical-thinking loop in the prefrontal layer (the metacognitive frameworks) is what makes reasoning models defensible. The visible chain is evidence, not proof. ### What this matrix does not cover - Per-task benchmark performance - benchmark leaderboards age too fast for a quarterly refresh; consult [Chatbot Arena](https://lmsys.org/), [LiveCodeBench](https://livecodebench.github.io/), and the vendors' own technical reports for current numbers. - Latency - reasoning latency varies by load, region, and tier; this matrix tracks capability shape, not throughput. - Fine-tuning availability - some reasoning families allow fine-tuning, some do not; consult the relevant vendor doc. - Open-weights status - DeepSeek R-series is open-weights; the rest of the families in this matrix are closed-weights as of the verified date. ### Correction policy If a vendor surface changes materially before the next quarterly refresh, please flag it via [the errata page](/errata/). Substantive corrections that change a "visible chain" or "faithfulness caveat" cell will be reflected here within two weeks.