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DeepSeek
For step-by-step reasoning you can check, with the option to self-host.
Step-by-step reasoning — maths, logic, and technical problem-solving — plus the unusual option of running an open-weights model yourself.
Primarily its training data. The distinctive property is not where it gets information but that its weights are openly available, so the same model can be run on infrastructure you control — which changes the privacy calculus entirely (see below).
The fundamentals — goal, context, constraints, format — work the same everywhere. Build one in the prompt lab
Capable on documents and code, but the reason to reach for it is reasoning-heavy work. It does not have the live-web or workspace-grounding shapes of other assistants, so bring the material to it directly.
Writing
Here's my technical explanation. Check it for logical errors and unstated assumptions. Don't improve the prose.
Plays to reasoning checking rather than style editing.
Research
Work through whether this argument holds. State the premises, then say which one is doing the most work.
Argument analysis rather than source retrieval.
Coding
This function fails on this input. Reason through what happens step by step, then give the fix and a test that would have caught it.
Step-by-step debugging is where its reasoning trace earns its keep.
Learning
Derive this result from first principles. Number each step and state which rule you used.
A checkable derivation, not just a stated result.
Document analysis
Here's the methodology section. Identify every assumption the conclusion depends on, and which would break it if wrong.
Structural analysis of an argument's reasoning, not its prose.
Brainstorming
Give me five approaches, then rank them by which has the fewest unverified assumptions, showing your reasoning.
Ranking its own generated options against a stated criterion — not a ranking of tools.
Everyday
I have these constraints and this budget. Work out what's feasible and show the arithmetic.
Practical constrained reasoning with checkable arithmetic.
This one needs the most care, factually and without alarmism. The hosted consumer service is operated by a company subject to its own jurisdiction's laws, with its own retention and training terms — read them and decide deliberately, exactly as you should for any operator. Distinctly, because the weights are open, a self-hosted or third-party-hosted deployment is a genuinely different privacy proposition: your data can stay on infrastructure you control. Do not generalise a judgment about one deployment to the other. For regulated or confidential material, your organisation's policy governs — check before using any hosted assistant.
Read DeepSeek’s privacy policy (opens in a new tab)These change frequently. Checked on 15 Aug 2026 — if what you see differs, the official documentation is right and we are out of date.
These details are more than six weeks old and may have changed. Check the official documentation.
Related CalQuest content
Stating constraints formally, then checking the result, is the same habit the lab builds around any task.
Open the prompt lab