doubt-driven-development

A review practice that asks a fresh perspective to challenge important technical decisions instead of simply approving them.

In plain words
What is it for?
Use it for complex logic, unfamiliar code, cross-module changes, security-sensitive work, production changes, data migrations, and other decisions where errors are costly.
Why use it?
Long coding sessions can make assumptions feel certain. Adversarial review can catch mistakes while changes are still relatively easy to make.

Skill for Claude CodeCodexCursor

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/mamahoos/dot-files/doubt-driven-development
Any agent
npx skills add mamahoos/dot-files --skill doubt-driven-development
Clone the repo
git clone --depth 1 https://github.com/mamahoos/dot-files

Made for: Claude Code, Codex, Cursor.

Per session 67 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,595 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 98% copy Near-identical to another mod 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 $0.00067 $0.03595
Opus 5 $0.00034 $0.01798
Sonnet 5 $0.00013 $0.00719
Haiku 4.5 $0.00007 $0.00360

Measured 2d ago against content hash 9e4709c6e9de, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

doubt-driven-development 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 2d ago.

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.

Origin

This is a copy

98% identical to doubt-driven-development — 1 line differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

home/.cursor/skills/doubt-driven-development/SKILL.md · 245 lines

How it starts

The opening of the file, as written. The whole thing — 245 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Doubt-Driven Development

Overview

A confident answer is not a correct one. Long sessions accumulate context that quietly turns assumptions into "facts" without anyone noticing. Doubt-driven development is the discipline of materializing a fresh-context reviewer — biased to disprove, not approve — before any non-trivial output stands.

This is not /review. /review is a verdict on a finished artifact. This is an in-flight posture: non-trivial decisions get cross-examined while course-correction is still cheap.

When to Use

A decision is non-trivial when at least one of these is true:

  • It introduces or modifies branching logic
  • It crosses a module or service boundary
  • It asserts a property the type system or compiler cannot verify (thread safety, idempotence, ordering, invariants)
  • Its correctness depends on context the future reader cannot see
  • Its blast radius is irreversible (production deploy, data migration, public API change)

Apply the skill when:

  • About to make an architectural decision under uncertainty
  • About to commit non-trivial code
  • About to claim a non-obvious fact ("this is safe", "this scales", "this matches the spec")
  • Working in code you don't fully understand

When NOT to use:

  • Mechanical operations (renaming, formatting, file moves)
  • Following a clear, unambiguous user instruction
  • Reading or summarizing existing code
  • One-line changes with obvious correctness
  • Pure tooling operations (running tests, listing files)
  • The user has explicitly asked for speed over verification

If you doubt every keystroke, you ship nothing. The skill applies only to non-trivial decisions as defined above.

Loading Constraints

This skill is designed for the main-session orchestrator, where Step 3 (DOUBT, detailed below) can spawn a fresh-context reviewer.

  • Do NOT add this skill to a persona's skills: frontmatter. A persona that follows Step 3 would spawn another persona — the orchestration anti-pattern explicitly forbidden by ../../references/orchestration-patterns.md ("personas do not invoke other personas").
  • If you find yourself applying this skill from inside a subagent context (where Claude Code prevents nested subagent spawn): the preferred path is to surface to the user that doubt-driven cannot run nested and let the main session handle it. As a last resort only, a degraded self-questioning fallback exists — rewrite ARTIFACT + CONTRACT as a fresh self-prompt with a hard mental separator from your prior reasoning, and walk Steps 1–5. This is not fresh-context review (you carry your own context with you), so flag the result as degraded and prefer escalation whenever the user is reachable.

Read the full file on GitHub · 245 lines

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. 2d ago First seen · 245 lines · 67 tokens per session scan A 9e4709c6e9de

Subscribe to this mod's changes

doubt-driven-development is a skill published in the GitHub repository mamahoos/dot-files (3 stars, last pushed 3d ago), licensed MIT. It adds 67 tokens to every session and 3,595 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 98% identical to doubt-driven-development, differing in 1 line, and is treated as a copy.

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