# Source Driven Development > Ground every framework- or library-specific decision in official docs you actually fetched — never in training-data memory. Use the moment you are about to write version-sensitive code (routing, forms, data fetching, auth, state, config, build setup): detect the installed version from the dependency file, deep-link the matching doc page, follow it exactly, and cite the full URL. Use whenever correctness depends on a version and "I think the API is…" is about to happen, or when reviewing framework-specific code for stale/deprecated patterns. - Skill: `celestialdust/source-driven-development` (Agent Skill) - Install (CLI): `npx skillmds@latest add celestialdust/source-driven-development` - Raw SKILL.md: https://api.skillmd.com/api/skills/celestialdust/source-driven-development/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Integrations & APIs - Author: celestialdust (https://skillmd.com/u/celestialdust) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/celestialdust/source-driven-development --- # Source-Driven Development ## Overview **Stage: Implement — a referenced discipline, not a chain stage.** `incremental-implementation` and `test-driven-development` pull it in mid-slice; it emits no artifact of its own. 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") ## Inputs It still refuses to *guess*. In order of authority it needs: - **The dependency manifest** (`package.json` · `pyproject.toml`/`requirements.txt` · `composer.json` · `go.mod` · `Cargo.toml` · `Gemfile`) — the source of truth for *which version* of each framework/library is installed. This is what Step 1 (DETECT) reads. - **`environment.md` → `runtime-dep` rows** (typed-kind manifest, closed kind enum incl. `runtime-dep`; **no value column**) — names the frameworks/runtimes the project depends on, to cross-check the manifest. Use it to confirm the stack, never as the version source (it carries no values). - **The current slice's step**, in `plan/.md` — the framework-specific code about to be written; tells you *which* feature's docs to fetch (the relevant page, not the homepage). **Refuse-to-run / ask-don't-guess:** if no dependency manifest is present and the version cannot be pinned from `environment.md`, STOP and ask the user for the version — never implement framework-specific code from memory against an unknown version (Step 1). ## The Process ``` DETECT ──→ FETCH ──→ IMPLEMENT ──→ CITE │ │ │ │ ▼ ▼ ▼ ▼ 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: ``` package.json → Node/React/Vue/Angular/Svelte composer.json → PHP/Symfony/Laravel requirements.txt / pyproject.toml → Python/Django/Flask go.mod → Go Cargo.toml → Rust Gemfile → Ruby/Rails ``` State what you found explicitly: ``` STACK DETECTED: - React 19.1.0 (from package.json) - Vite 6.2.0 - Tailwind CSS 4.0.3 → Fetching official docs for the relevant patterns. ``` If versions are missing or ambiguous, **ask the user**. Don't guess — the version determines which patterns are correct. ### Step 2: Fetch Official Documentation Fetch the specific documentation page for the feature you're implementing. Not the homepage, not the full docs — the relevant page. **Source hierarchy (in order of authority):** | Priority | Source | Example | |----------|--------|---------| | 1 | Official documentation | react.dev, docs.djangoproject.com, symfony.com/doc | | 2 | Official blog / changelog | react.dev/blog, nextjs.org/blog | | 3 | Web standards references | MDN, web.dev, html.spec.whatwg.org | | 4 | Browser/runtime compatibility | caniuse.com, node.green | **Not authoritative — never cite as primary sources:** - Stack Overflow answers - Blog posts or tutorials (even popular ones) - AI-generated documentation or summaries - Your own training data (that is the whole point — verify it) **Be precise with what you fetch:** ``` BAD: Fetch the React homepage GOOD: Fetch react.dev/reference/react/useActionState BAD: Search "django authentication best practices" GOOD: Fetch docs.djangoproject.com/en/6.0/topics/auth/ ``` 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. (Source: react.dev/reference/react/useActionState) Options: A) Use the modern pattern (useActionState) — consistent with current docs B) Match existing code (useState) — consistent with codebase → Which approach do you prefer? ``` Surface the conflict. Don't silently pick one. ### Step 4: Cite Your Sources Every framework-specific pattern gets a citation. The user must be able to verify every decision. **In code comments:** ```typescript // React 19 form handling with useActionState // Source: https://react.dev/reference/react/useActionState#usage const [state, formAction, isPending] = useActionState(submitOrder, initialState); ``` **In conversation:** ``` I'm using useActionState instead of manual useState for the form submission state. React 19 replaced the manual isPending/setIsPending pattern with this hook. Source: https://react.dev/blog/2024/12/05/react-19#actions "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 ## Outputs & handoff contract **Emits: no standalone chain artifact** — `source-driven-development` is applied *inside* `incremental-implementation`/`test-driven-development`, so its product lands in their diff: - **Source-cited code** — every framework-specific pattern carries a full-URL, deep-linked citation in a code comment (Step 4); the citation travels with the line into the slice's diff and is what `pull-request`'s design-anchored summary and the `code-review` fan-out read to confirm the pattern is current, not hallucinated. - **Surfaced conflicts** — any docs-vs-codebase or docs-vs-docs conflict is raised to the user at a human-led gate or recorded in the slice notes, never silently resolved (Step 3). - **`UNVERIFIED:` flags** — any pattern with no official documentation is explicitly flagged in the code/diff so downstream gates (`quality-verification`, `code-review`, the evaluator) can see it was not source-backed. **Stable contract for consumers:** the citation format is `// ` then `// Source: `; downstream skills key off the `Source:` token. **STATE.md:** this discipline writes no slice row of its own — the host `incremental-implementation` slice stays in `impl` and the orchestrator advances it; citations and `UNVERIFIED:` flags become part of that slice's diff/PR. Feeds `correctness` and `plan_adherence` (current, cited APIs) and is checked by the review fan-out.