Build, iterate, reuse and improve

Two pieces of code that do almost the same thing drift apart, and every fix then has to be made twice. So before writing anything new, a writer finds the code that already owns the concern and extends or improves it.

The user, 2026-10-10: “we must build, iterate, reuse and improve things, avoid duplicate or similar logics”.

• Before writing anything new, search for the existing owner and EXTEND or IMPROVE it.
• NEAR-duplicates (similar logic, renamed copies, parallel implementations of the same idea) are violations, not only identical code.
• Every writer’s report names the existing owners it reused or extended; every reviewer checks for similar logic.
• Retroactive (UR-19). It sharpens UR-01 and UR-16.

How it is enforced: tests/prevention/no-duplicate-code.test.ts refuses exact duplicate function bodies in the web, server and scripts trees, and engine/test/prevention/no-duplicate-function-bodies.test.ts adds a normalized-similarity pass over the engine’s source. Structural near-duplicates (renamed copies, parallel implementations) are not caught mechanically yet; review covers them.