simplify

name	simplify
description	Clean up the changed code without changing behavior — review the diff for reuse, simplification, efficiency, and altitude cleanups via 4 parallel agents, then apply the fixes
argument-hint	[<target>] (defaults to the current diff)

Simplify

/simplify → 4 cleanup agents in parallel → apply the fixes

You are improving the quality of the changed code, not hunting for bugs. Review it for reuse, simplification, efficiency, and altitude issues, then fix what you find. Do not look for correctness bugs — that is what a code review is for.

Phase 0 — Establish the diff

If $ARGUMENTS names a target (a path, a commit, a ref range, a PR number), treat it as scope guidance and establish the diff from it. Otherwise review the current change:

• Working-tree changes: git diff HEAD (plus git status --short for new files).
• If the working tree is clean, the branch's committed diff: git diff @{upstream}...HEAD, falling back to git diff origin/main...HEAD when there is no upstream.

Read the diff, and read enough of each enclosing function or file to judge the change in context. If the diff is empty, say so and stop.

Phase 1 — Review (4 cleanup agents in parallel)

Launch 4 independent review agents via the task tool (subagent_type: "explore"), all in a single message so they run concurrently. Pass each agent the diff, the files it touches, and exactly one of the four angles below. Each returns its findings with file, line, a one-line summary, and the concrete cost (what is duplicated, wasted, or harder to maintain).

Reuse

Flag places the diff re-implements something the codebase already has — grep shared/utility modules and files adjacent to the change, and name the existing helper to call instead.

Simplification

Flag unnecessary complexity the diff adds: redundant or derivable state, copy-paste with slight variation, deep nesting, dead code left behind. Name the simpler form that does the same job.

Efficiency

Flag wasted work the diff introduces: redundant computation or repeated I/O, independent operations run sequentially, blocking work added to startup or hot paths. Also flag long-lived objects built from closures or captured environments — they keep the entire enclosing scope alive for the object's lifetime (a memory leak when that scope holds large values); prefer a class/struct that copies only the fields it needs. Name the cheaper alternative.

Altitude

Check that each change is implemented at the right depth, not as a fragile bandaid. Special cases layered on shared infrastructure are a sign the fix isn't deep enough — prefer generalizing the underlying mechanism over adding special cases.

Phase 2 — Apply the fixes

Wait for all four agents to complete, dedup findings that point at the same line or mechanism, and fix each remaining one directly. Skip any finding whose fix would change intended behavior, require changes well outside the reviewed diff, or that you judge to be a false positive — note the skip rather than arguing with it. Finish with a brief summary of what was fixed and what was skipped (or confirm the code was already clean).

Behavior must not change. If a cleanup is only safe alongside a behavior change, don't make it — report it as a suggestion instead.