# Doubt Driven Development

> Challenge assumptions and hidden dependencies before they become bugs

- Skill: `vignesh2027/doubt-driven-development` (Agent Skill)
- Install (CLI): `npx skillmds@latest add vignesh2027/doubt-driven-development`
- Raw SKILL.md: https://api.skillmd.com/api/skills/vignesh2027/doubt-driven-development/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: vignesh2027 (https://skillmd.com/u/vignesh2027)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/vignesh2027/doubt-driven-development

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## Overview

Every "I'm sure this is fine" is a future incident. This skill applies systematic skepticism to assumptions in requirements, implementations, and integrations before they ship.

## When to Use

- When something "seems obvious" but hasn't been verified
- When implementing code that depends on external behavior
- When code review reveals an implicit assumption
- When debugging a "that's impossible" bug

## Process

### Step 1: List your assumptions
For every non-trivial implementation, write down all the things that must be true for it to work. Make implicit assumptions explicit.

### Step 2: Classify by risk
For each assumption: what is the cost if it's wrong? High-cost assumptions must be verified before shipping.

### Step 3: Verify high-cost assumptions
How to verify:
- Write a test that fails if the assumption is wrong
- Find the source of truth (spec, documentation)
- Measure it (add a log, run a query)
- Ask someone who knows

### Step 4: Make remaining assumptions visible
For assumptions you can't verify before shipping: document them as known assumptions. Future engineers must be able to find them.

## Verification Requirements

- [ ] All non-trivial assumptions listed
- [ ] High-cost assumptions verified before shipping
- [ ] Remaining assumptions documented in code