ai-generation-hygiene

metadata	{"type":"protocol","invocation":"both","practice":null}
name	ai-generation-hygiene
description	Code quality rules that catch common AI-generation artifacts. Apply when writing code, generating functions, implementing features, creating scripts, or producing any code output. Catches: redundant defensive checks, gratuitous logging, restating comments, unnecessary casts, over-abstraction, verbose implementations. Always relevant during code generation tasks.

AI Generation Hygiene

Every line of generated code must earn its place. Cut until cutting would lose meaning.

The Nine Banned Patterns

Before presenting or committing code, scan for these. Each hit is a line that doesn't earn its place — fix before presenting.

#	Pattern	Rule	Example of violation
P1	Redundant defensive checks	MUST NOT null/type-check values the type system already guarantees	if x is None: raise when x is typed non-Optional
P2	Catch-everything	MUST NOT catch, log, and re-raise unchanged — only catch what you can handle (recover, degrade, or transform to a domain exception)	except Exception as e: logger.error(e); raise
P3	Restating comments	MUST NOT comment what the code already says — comments document WHY: constraints, rejected alternatives, non-local coupling	counter += 1 # increment counter
P4	Gratuitous logging	MUST NOT add entry/exit logging or parameter echoing — log state transitions, business decisions, errors	logger.info("Entering process_payment")
P5	Redundant casts	MUST NOT cast values to types they already are	str(f"hello"), list([1,2,3]), int(len(x))
P6	Single-use abstractions	SHOULD NOT create classes, factories, or wrappers used exactly once — direct code beats indirection without reuse	factory class instantiated once
P7	Defensive copies without mutation	SHOULD NOT copy data structures nothing in the call chain mutates	.copy() when nothing mutates the original
P8	Verbose conditionals	SHOULD reduce to direct expressions	if x: return True else: return False instead of return x
P9	Unused imports	MUST NOT leave imports never referenced — each import is a dependency claim	import os in a file that never uses it

The Exception: Trust Boundaries

Keep defensive code where values enter from outside your control:

• User input, form data, request bodies
• API responses, webhook payloads
• Deserialized data (JSON, YAML, config files)
• Shared library public APIs (callers you don't control)

The test: "Who would violate this contract and how?" If the answer is "no one, the type system prevents it," remove the check.