Simplify

Improve the quality of the changed code. Review it for reuse, simplification, efficiency, and altitude issues, then fix what you find. Do not look for correctness bugs — that is a dedicated review pass, not this one.

Phase 0 — Gather the diff

Run git diff @{upstream}...HEAD to get the diff under review. Without an upstream, diff against the merge-base with the default branch, detected dynamically (e.g. git symbolic-ref refs/remotes/origin/HEAD), and fall back to git diff HEAD~1. If that range is empty or there are uncommitted changes, also run git diff HEAD and include the working tree — this often runs before the commit. If the invocation names a target — a PR, a branch, a path — review that instead. Treat this diff as the review scope.

Phase 1 — Review (four cleanup angles)

Spawn one subagent per angle below, each given the diff and its own angle. Run them in parallel if the harness supports it; otherwise serialize. If the harness has no subagents, work through all four angles yourself in one pass — do not drop an angle for lack of fan-out — and say so in the summary, so the reader isn't misled about what ran.

Each angle returns its findings with file, line, a one-line summary, and the concrete cost: what is duplicated, wasted, or made harder to maintain.

Once all reports are in, or if the run stops or fails, release the reviewers this run started and no others.

Reuse

Flag new code that re-implements something the codebase already has — search shared and utility modules and the 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 or struct that copies only the fields it needs. Name the cheaper alternative.

Altitude

Check that each change fixes the root cause at the right depth rather than patching a symptom with a fragile bandaid. Special cases layered on shared infrastructure are a sign the fix isn't deep enough — prefer the simpler, more general change to the underlying mechanism over adding special cases, and name that change.

Phase 2 — Apply the fixes

Wait for all four angles to report, 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).