Minimal Modular Code

Keep agent-written code minimal and modular. Minimal is not fewest lines: it is behavior behind a small interface, reused before rebuilt, legible to a finite-context reader. Steer by named heuristics:

• Reuse before write — grep the repo and deps for an existing helper before adding one.
• Subtract first — ask "what can be removed?"; the subtractive option never surfaces on its own.
• Rule of three — duplication is cheaper than the wrong abstraction; back a bad abstraction out rather than parameterize it.
• Deep modules — small interface over substantial behavior; single-caller indirection and pass-through layers are negative-value structure.
• Information hiding — put the seam where it hides the likely-to-change decision; dependencies point toward stable code.
• Concise, not terse — fewer semantic elements, never code golf.
• Gates, not prose — a load-bearing invariant needs a failing check, not a sentence.

Deletion needs proof. Never delete guards, tests, validation, error paths, or boundaries to make a diff smaller unless the prompt supplies proof they are obsolete — from blame, tests, the contract, or an upstream invariant. "Not in scope", downstream behavior, or a promised later PR is not proof. When proof is missing, keep the code and say why.

Workflow