spec-to-code-fidelitylisted

# Spec-to-Code Fidelity > Status: v0.1 baseline draft — derived from the case catalog and axis definitions; awaiting trace evidence from Fable 5.1 case runs. ## When to apply - Implementing a protocol or format from an RFC, W3C/WHATWG spec, or vendor format document (HTTP/1.1, WebSocket framing, GGUF, JWT, WAI-ARIA). - Translating equations from a paper into code (attention math, quantization schemes, PPO loss, numerical integrators). - Writing a parser/serializer for a binary or wire format where a single off-by-one silently corrupts everything downstream. - Porting a reference implementation to another language while claiming behavioral equivalence. - Any task where the acceptance criterion is "conforms to the document" rather than "seems to work." - Debugging interop failures where your implementation and a peer disagree about what the spec says. ## Core loop 1. **Acquire the authoritative text before writing code.** Get the actual RFC/paper/spec section into context — not your memory of it. If the exact document version matters (RFC obsoleted-by chains, paper v1 vs v2 on arXiv), pin the version and record it in a comment at the top of the implementation. 2. **Decompose the spec into a numbered clause inventory.** Walk the document and list every normative statement (MUST/SHALL/SHOULD, every equation, every field of every struct/frame, every state transition). Give each clause a stable ID (e.g. `§5.2-3`, `Eq.4`). This inventory is your requirements list and later your