deepthink

A structured reasoning guide for difficult problems where quick debugging or analysis has stalled. It uses testable hypotheses, evidence tracking, confidence updates, and explicit remaining uncertainty.

In plain words
What is it for?
Investigating stubborn bugs, comparing competing explanations, recording supporting and opposing evidence, and reporting a justified conclusion.
Why use it?
It helps separate evidence from guesses and prevents repeatedly investigating the same explanation without making progress.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/cofin/flow/deepthink
Any agent
npx skills add cofin/flow --skill deepthink
Clone the repo
git clone --depth 1 https://github.com/cofin/flow

Made for: Claude Code, Codex.

Per session 39 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 332 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00039 $0.00332
Opus 5 $0.00019 $0.00166
Sonnet 5 $0.00008 $0.00066
Haiku 4.5 $0.00004 $0.00033

Measured yesterday against content hash 3835cbab40a2, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

deepthink scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/flow/skills/deepthink/SKILL.md · 60 lines

What it actually says

Deepthink

Use hypothesis tracking to turn a resistant problem into an evidence-backed, actionable conclusion.

Workflow

  1. Load the reasoning strategy and confidence ledger below.
  2. Frame one testable hypothesis, gather relevant evidence, and update the hypothesis and ledger after each investigation step.
  3. Continue until the completion criteria are met or the evidence establishes exactly what remains unknowable.

Guardrails

Do not hoard evidence, loop over the same checks, or present a hypothesis as a conclusion. Reassess after three steps without confidence progress.

Output

Return the final hypothesis, evidence for and against it, confidence and its basis, remaining uncertainty, and the resulting action.

Validation

Confirm the hypothesis evolved with evidence and the conclusion meets the reference completion criteria.

Example

For a CI-only failure, revise a flakiness hypothesis as deterministic environment evidence appears, then report the verified configuration cause.

References

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 60 lines · 39 tokens per session scan A 3835cbab40a2

Subscribe to this mod's changes

deepthink is a skill published in the GitHub repository cofin/flow (16 stars, last pushed 2d ago), licensed Apache-2.0. It adds 39 tokens to every session and 332 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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