CARD: scaffold-g-doctests — Executable Examples / Twoslash (TypeScript)

Band 1 — Identity & Recognition

02Classification: layer=C (meta) + G (empirics); mechanism=scaffold G.

03Intent: Ship one type-checked, runnable example per public seam showing the ONE canonical way to use it — a few-shot usage signal that cannot drift into a lie because it must type-check (Twoslash) and/or run.

04Also Known As: doctest; Twoslash; @example JSDoc; usage example; example-driven docs; golden usage; runnable spec-by-example; expectTypeOf/tsd type-level example.

05Applicability / Recognition: Apply when — a public seam has no type-checked example of canonical use; usage is documented only in prose; multiple usage idioms coexist with no canonical one. Detector seed: an exported seam item with no Twoslash/@example demonstrating construction+use → recognition fires (the reference-library result, R2C-008; examples are the executable half of "primitives + notes").

Band 2 — Justification & Tradeoffs

06Motivation: A weak agent imitates whatever usage it sees nearby (R3-006). If the nearest example is a prose snippet that has drifted, it imitates a lie. A Twoslash example that lies fails the docs build, so the imitated signal is guaranteed truthful — and it shows the single canonical idiom, suppressing idiom-divergence.

07Structure & Participants: Twoslash example (type-checked code in the docs) · @example JSDoc (validated) · examples/ cell (larger compiled scenario, built in CI) · canonical idiom (the one blessed usage).

08Collaborations: Encodes the canonical idiom Class B's branded/typed surface enforces; runs in the Class E loop; its truthfulness backs §10 prose discipline; pairs with the type-level tests (guide §12) for generic surfaces.

09Goals / Non-Goals: Goals: every public seam carries ≥1 type-checked example of canonical use. Non-Goals: NOT exhaustive examples (one canonical each); NOT a replacement for property tests (examples show usage, tests check behavior).

10Consequences: (+) the imitated few-shot signal cannot lie; (+) one canonical idiom suppresses divergence. (−) examples are code to maintain; (−) over-exampling bloats — one canonical per seam.

11Alternatives: prose examples (drift silently); separate example files (fine, but Twoslash sits at the point of use). Prefer type-checked, co-located.

12Risks & Assumptions: assumes the seam has a canonical usage worth blessing. Sunset: none material.

13Evidence & Transfer-strength: R2C-008 (executable reference material transformative, benchmark), R3-006 (codebase as few-shot prompt, theory), H4 (lying prose harms). Class: benchmark + theory. Tag: [E-strong].

Band 3 — Operation

trigger: WHEN an exported seam item lacks a type-checked example (Twoslash/@example) of canonical construction+use THEN apply
mode: gate
routine:
  1. Write the single canonical usage as a Twoslash example on the seam item (or an `@example` block).
  2. Ensure it constructs via the blessed path (Class B builder/branding) and uses the seam.
  3. For larger scenarios, add an examples/ cell that builds in CI.
  4. For generic/branded surfaces, add an `expectTypeOf`/`tsd` type-level example.
  5. Confirm the example type-checks green in the per-cell loop.
checker: @typescript-eslint/conform `seam-has-doctest` + Twoslash docs-build + `tsc --noEmit` on examples
raid_role: layer=cells; order=after:typed-builders; batch=seam
budget: active_rules=1; first_signal=tsc/twoslash (<60s)