Grounds every implementation decision in official documentation. Use when you want authoritative, source-cited code free from outdated patterns. Use when building with any framework or library where correctness matters.
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Step 1
Copy the install command
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Step 2
Check source and behavior
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Step 3
Overview
# Source-Driven Development
Overview
Every framework-specific code decision must be backed by official documentation. Don't implement from memory — verify, cite, and let the user see your sources. Training data goes stale, APIs get deprecated, best practices evolve. This skill ensures the user gets code they can trust because every pattern traces back to an authoritative source they can check.
When to Use
The user wants code that follows current best practices for a given framework
Building boilerplate, starter code, or patterns that will be copied across a project
The user explicitly asks for documented, verified, or "correct" implementation
Implementing features where the framework's recommended approach matters (forms, routing, data fetching, state management, auth)
Reviewing or improving code that uses framework-specific patterns
Any time you are about to write framework-specific code from memory
**When NOT to use:**
Correctness does not depend on a specific version (renaming variables, fixing typos, moving files)
Pure logic that works the same across all versions (loops, conditionals, data structures)
The user explicitly wants speed over verification ("just do it quickly")
The Process
```
DETECT ──→ FETCH ──→ IMPLEMENT ──→ CITE
│ │ │ │
Validate with a real task
Run one small real task before keeping it in your long-term workflow.
▼ ▼ ▼ ▼
What Get the Follow the Show your
stack? relevant documented sources
docs patterns
```
Step 1: Detect Stack and Versions
Read the project's dependency file to identify exact versions:
After fetching, extract the key patterns and note any deprecation warnings or migration guidance.
When official sources conflict with each other (e.g. a migration guide contradicts the API reference), surface the discrepancy to the user and verify which pattern actually works against the detected version.
Step 3: Implement Following Documented Patterns
Write code that matches what the documentation shows:
Use the API signatures from the docs, not from memory
If the docs show a new way to do something, use the new way
If the docs deprecate a pattern, don't use the deprecated version
If the docs don't cover something, flag it as unverified
**When docs conflict with existing project code:**
```
CONFLICT DETECTED:
The existing codebase uses useState for form loading state,
but React 19 docs recommend useActionState for this pattern.
"useTransition now supports async functions [...] to handle
pending states automatically"
```
**Citation rules:**
Full URLs, not shortened
Prefer deep links with anchors where possible (e.g. `/useActionState#usage` over `/useActionState`) — anchors survive doc restructuring better than top-level pages
Quote the relevant passage when it supports a non-obvious decision
Include browser/runtime support data when recommending platform features
If you cannot find documentation for a pattern, say so explicitly:
```
UNVERIFIED: I could not find official documentation for this
pattern. This is based on training data and may be outdated.
Verify before using in production.
```
Honesty about what you couldn't verify is more valuable than false confidence.
Common Rationalizations
| Rationalization | Reality |
|---|---|
| "I'm confident about this API" | Confidence is not evidence. Training data contains outdated patterns that look correct but break against current versions. Verify. |
| "Fetching docs wastes tokens" | Hallucinating an API wastes more. The user debugs for an hour, then discovers the function signature changed. One fetch prevents hours of rework. |
| "The docs won't have what I need" | If the docs don't cover it, that's valuable information — the pattern may not be officially recommended. |
| "I'll just mention it might be outdated" | A disclaimer doesn't help. Either verify and cite, or clearly flag it as unverified. Hedging is the worst option. |
| "This is a simple task, no need to check" | Simple tasks with wrong patterns become templates. The user copies your deprecated form handler into ten components before discovering the modern approach exists. |
Red Flags
Writing framework-specific code without checking the docs for that version
Using "I believe" or "I think" about an API instead of citing the source
Implementing a pattern without knowing which version it applies to
Citing Stack Overflow or blog posts instead of official documentation
Using deprecated APIs because they appear in training data
Not reading `package.json` / dependency files before implementing
Delivering code without source citations for framework-specific decisions
Fetching an entire docs site when only one page is relevant
Verification
After implementing with source-driven development:
[ ] Framework and library versions were identified from the dependency file
[ ] Official documentation was fetched for framework-specific patterns
[ ] All sources are official documentation, not blog posts or training data
[ ] Code follows the patterns shown in the current version's documentation
[ ] Non-trivial decisions include source citations with full URLs
[ ] No deprecated APIs are used (checked against migration guides)
[ ] Conflicts between docs and existing code were surfaced to the user
[ ] Anything that could not be verified is explicitly flagged as unverified
