Classification: layer=A (language-shape) + C (meta); mechanism=scaffold A.

Intent: Where an artifact is mechanically derivable from a smaller spec, ship a program that EMITS it (externalizing fragile implicit structure into named inputs and reusable functions) plus its committed output plus a determinism check — instead of hand-maintained output.

Also Known As: codegen; build script; metaprogramming; macro expansion; template generation; emitter.

Applicability / Recognition: Apply when — boilerplate repeats across cells; an artifact (transition table, FFI binding, serializer, exhaustive match) is a mechanical function of a manifest/spec; raw hand-authoring requires tracking implicit bookkeeping a weak reader cannot hold (the Brainfuck-generator case, R2C-008). *Detector seed:* near-duplicate code blocks differing only in a key, OR a hand-maintained table that mirrors a spec → recognition fires.

Motivation: A weak agent must add a variant to a 12-arm state machine spread across match, transition table, and error enum. Hand-editing three sites desynchronizes them. A generator emitting all three from one table turns the task into "add one row" — the strong author's structural decision is the emitter; the weak reader fills a named input.

Structure & Participants: *Spec/manifest* (the small input) · *Generator* (Rust build.rs or proc-macro / external codegen) · *Committed output* (plain idiomatic Rust) · *Determinism check* (regenerate-and-diff in CI).

Collaborations: Output is checked by Class E loop; generator emits Class G doctests for its products; pairs with Class B (generated types). In raids, regeneration is a batch operation.

Goals / Non-Goals: *Goals:* eliminate hand-maintained derivable artifacts (A2/A3); shrink edit surface to the spec. *Non-Goals:* NOT a custom compiler for production code (forbidden) — generators emit standard Rust; NOT for one-off code with no repetition.

Consequences: (+) edit surface collapses to the spec; (+) consistency is structural, not vigilance-based. (−) generator itself is code to maintain; (−) over-generation hides logic — generate structure, not business decisions.

Alternatives: hand-written code (fine when non-repetitive); a typed builder (Class B) when the variation is per-call not per-artifact.

Risks & Assumptions: assumes the derivation is truly mechanical; a generator encoding a business decision is misuse. *Sunset:* if a future language feature expresses the pattern natively, the generator retires. Weak agents may struggle to MODIFY a generator ([E-hyp] build/use boundary) — for the weakest tier, expose generation as a fixed codemod (Class I).

Evidence & Transfer-strength: R2C-008 (executable generators transformative, benchmark), R2C-003 (metaprogramming as adaptation, benchmark), A2/A3. Class: benchmark + production. Tag: **[E-strong]** (for generation).