---
name: yagni-rules
description: The GRU953-Studio lean-coding rule set (YAGNI — "You Aren't Gonna Need It"). Use whenever the studio writes, reviews or trims code, whenever a builder is about to add a file, function, dependency or abstraction, and whenever the user says "keep it simple", "minimal", "lean", "no bloat", or "just the basics". Every line of studio-produced code must pass this ladder.
---

# YAGNI rules

Before writing ANY code — a file, a function, a class, a dependency — walk
this ladder from the top. Stop at the first rung that answers the need.

## The ladder

1. Does this need to exist at all? (speculative need = skip)
2. Already in this codebase? (reuse)
3. Standard library does it? (use it)
4. Native platform feature? (use it)
5. Already-installed dependency? (use it; never add a new one for what a
   few lines can do)
6. Can it be one line? (one line)
7. Only then: the minimum code that works.

## Standing rules

- **No unrequested abstractions.** No interfaces, base classes, plugin
  systems, config layers or wrappers the confirmed brief does not require
  today.
- **No scaffolding "for later".** Do not build hooks, empty folders, stub
  modules or feature flags for imagined future work. If it might matter
  later, write one line about it in `Dev-Memory/decisions/` instead.
- **Deletion over addition.** A smaller diff that deletes code beats a
  larger one that adds.
- **Boring over clever.** The obvious, well-trodden construct over the
  clever one.
- **Fewest files.** Split code across files only when a file genuinely
  serves two different owners or purposes.
- **Shortest working diff wins.**
- **Root-cause fixes.** Grep every caller and fix the cause, not the
  symptom.
- **Explanation never longer than the code it explains.**

## When NOT to be lazy

Deletion pressure STOPS at these:

- Input validation at trust boundaries.
- Error handling that prevents data loss.
- Security measures (authentication, permission checks, escaping).
- Accessibility basics (labels, keyboard use, readable contrast).
- Anything the confirmed brief explicitly asked for.

If in doubt, keep the safety and note the question in
`Dev-Memory/decisions/` rather than deleting it.

## Who applies this

- **builder** walks the ladder before every task.
- **reviewer** re-walks it over every diff, and also runs the whole-product
  trim before Publish (absorbing the retired `minimalist` role — 2026-07-10
  audit).
- **architect** applies the same ladder to stack and storage choices:
  zero-dependency options win ties.
- Deviations are allowed only with a written reason in
  `Dev-Memory/decisions/`.