Code Simplification

Code Simplification Skill

Code accretes defensive complexity: abstractions for futures that never came, options nobody passes, indirection that once had a reason. AI-generated code arrives pre-accreted — interfaces with one implementer, config objects with nine unused knobs. Simplification is its own pass with its own rule: behaviour identical, verified; complexity removed, listed.

What This Skill Produces

• The simplified code — smaller, flatter, same behaviour
• A removal ledger: each simplification, why it was safe, and what future it forecloses (honestly)
• Verification evidence that behaviour held

Required Inputs

Ask for these if not provided:

• The code — what works today and should keep working
• The pressure — what made it feel complex: onboarding, a bug, a review comment
• What must not change — the public API, behaviour, or performance envelope
• Test coverage — whether there are tests to prove the simplification is safe

What to Hunt (in order of payoff)

1. Speculative generality — the interface with one implementation, the parameter always called with the same value, the config option no caller sets, the "pluggable" thing nothing plugs into. Rule: the future that justified it must be on a roadmap, not in an imagination. YAGNI is a removal warrant.
2. Indirection without insulation — layers that only forward: the wrapper that calls one function, the factory returning one type, the event fired for one listener sitting next door. Each hop costs a reader a jump; collapse hops that don't isolate change.
3. Dead and duplicate paths — unreachable branches, handled-nowhere flags, the local re-implementation of a utility that exists (grep before believing anything is unique).
4. Cleverness taxing readers — the nested ternary, the reduce that should be a loop, the regex doing four jobs. Rewrite for the next reader; "fewer characters" is not "simpler".
5. Flatten control flow — guard clauses over nested ifs; early returns over else-pyramids; splitting the function that needs a comment per section into functions named by those comments.

The Safety Discipline (what makes this different from vandalism)

• Behaviour-preserving means verified, not asserted: run the full relevant suite before AND after; if coverage is thin over the code being simplified, add the pinning test first — simplifying untested code is refactoring blind.
• One hunt-class per pass where the code is load-bearing (remove speculation, verify; collapse indirection, verify) — mirrors incremental-implementation's rule.
• Chesterton's fence check on anything weird: git log/blame the strange bit before deleting it. Some "needless" complexity is a bug fix wearing an odd shape — if the history shows a fix, keep it and comment WHY it's shaped that way instead.
• Public surface needs a wider net: simplifying exported/shared code means checking callers across the codebase, not just the local file.

Output Format

Simplification: [target]

Verification: [suite/build run before → after: identical] · pinning tests added: [n or none-needed because…]

Removal ledger

Kept deliberately: [the weird-but-load-bearing bits, with their Chesterton evidence] Size: [LOC/complexity before → after]

Quality Checks

• Full verification ran before and after — identical behaviour, evidenced
• Thinly-tested code got pinning tests before simplification
• Every removal states the future it forecloses — "none" must be argued, not assumed
• Strange code was history-checked before deletion (Chesterton's fence)
• The result is simpler for a READER, not just shorter

Anti-Patterns

• Do not simplify and change behaviour in one pass — the moment behaviour shifts, this became a rewrite without a spec
• Do not delete weirdness without checking why it's weird — some of it is a production incident's scar tissue
• Do not confuse terse with simple — code golf raises the reading tax this skill exists to cut
• Do not remove flexibility that's actually on the roadmap — YAGNI applies to imagined futures, not planned ones
• Do not skip the ledger — invisible simplification is indistinguishable from unexplained deletion in review