om-scogo Simplify recently changed code for clarity, reuse, quality, and efficiency while preserving exact behavior. Prioritize readable, explicit code over compact code — fewer lines is not the goal.
Step 1: Identify scope
Resolve the simplification scope in this order:
- If the user explicitly named a scope (a file, a directory, "the function I just wrote", "the changes from this morning"), use that scope. Treat user-named scope as authoritative — do not widen it.
- Otherwise, in a git repository, default to the diff between the current branch and its base branch (e.g.,
git diff origin/main...or against the configured upstream). This covers the common case of "simplify everything I've added on this feature branch before opening a PR." If the branch has no upstream or base ref, fall back to staged + unstaged changes (git diff HEAD). - Outside a git repository or when no diff is available, review the most recently modified files mentioned by the user or edited earlier in this conversation.
If none of the above produces a non-empty scope, stop and ask the user what to simplify rather than guessing. Use the platform's blocking question tool: AskUserQuestion in Claude Code (call ToolSearch with select:AskUserQuestion first if its schema isn't loaded), request_user_input in Codex, ask_question in Antigravity CLI (agy), ask_user in Pi (requires the pi-ask-user extension). Fall back to numbered options in chat only when no blocking tool exists in the harness or the call errors (e.g., Codex edit modes) — not because a schema load is required. Never silently skip the question.
Preflight — skip a no-yield scope before spending reviewers. The three reviewers hunt for reuse, quality, and efficiency issues in code. If the resolved scope contains no substantive human-authored code — it is documentation- or Markdown-only, or only generated, vendored, dependency/lockfile, or purely mechanical (formatting, lint autofix, mass rename) churn — stop here with a one-line note that there is nothing to simplify, and do not dispatch the reviewers. On a mixed diff that includes both real code and these no-yield changes, narrow the scope to the code files and continue. This preflight gates on the kind of change only, never on size or count: an explicit user-named scope is authoritative and still runs even when small. (Callers that already gate on size — ce-work, /lfg — and any standing "run this automatically" instruction own the size/cost policy; this preflight is only the no-code safety net.)
Step 2: Launch 3 review agents in parallel
Dispatch three generic subagents — code-reuse, code-quality, and efficiency reviewers — via the platform's subagent primitive (Agent/Task in Claude Code, spawn_agent in Codex) where available; otherwise run the reviews inline or serially. For each reviewer, read its prompt asset from this skill's directory and pass the full file content as the subagent's prompt, together with the resolved scope (the full diff or file set) so it has complete context:
references/personas/code-reuse-reviewer.md— existing utilities, duplicated functionality, reimplemented stdlib/runtime primitives.references/personas/code-quality-reviewer.md— redundant state, parameter sprawl, copy-paste, leaky abstractions, stringly-typed code, dead code, over-nesting, and the over-simplification balance guard.references/personas/efficiency-reviewer.md— unnecessary work, missed concurrency, hot-path bloat, no-op updates, memory leaks.
Do not paraphrase these rubrics from memory — read each file and pass it verbatim, or the reviewer loses the gating rules that keep the pass behavior-preserving.
Bounded dispatch. Queue the three reviewers and launch only as many as the harness accepts at once; treat a concurrency/active-agent-limit error as backpressure (leave the reviewer queued and retry after a slot frees), not as reviewer failure.
Model selection. Use the platform's balanced mid-tier model for these reviewers when the current harness exposes a known override. In Claude Code this is the Sonnet class. In Codex, apply this tier only when the active dispatch primitive exposes an explicit model or custom-agent selector; task wording alone does not select a different model. Otherwise omit the override and inherit the parent model -- a working pass on the parent model beats a broken dispatch.
Permission mode. Omit the mode parameter on the dispatch call so the user's configured permission settings apply.
Step 3: Fix issues
Wait for all three agents to complete. Aggregate their findings and fix each issue directly. If a finding is a false positive or not worth addressing, note it and move on. Do not argue with the finding or raise questions to the user, just skip it.
Before applying each fix, confirm it preserves behavior: same output for every input, same error behavior, and same side effects and ordering. If a fix can't clear that test, skip it — automated checks in Step 4 don't cover every behavior.
Never simplify away a safety check. Input validation at trust boundaries, error handling that prevents data loss, security checks (authorization, escaping, sanitization), and accessibility affordances are not removable boilerplate — preserve them even when a finding frames them as redundant or inline-able. Code that drops one of these is not simpler, it is unfinished. If a proposed simplification would thin or remove one, skip it.
Honor caller-passed structure pins. When the caller passes a plan path with the structure-pin constraint, that plan path is context, never the simplification scope; that plan's session-settled:-labeled Key Technical Decisions are structural constraints the simplification must preserve — deliberately duplicated files stay duplicated, deliberately separate implementations stay separate — even when consolidation would otherwise be the obvious simplification. Behavior preservation already governs every fix; this extends it to settled structure.
Step 4: Verify behavior is preserved
The premise of this skill is that simplification preserves exact functionality. After applying fixes:
Run typecheck and lint over the full project. They are usually fast and catch the most common simplification regressions — broken imports, unused exports, dropped type narrowings, dead code other modules still reference.
Run tests:
- Run tests scoped to the changed paths. CI runs the full suite on PR — this local check is a fast signal, not the final guarantee. Match scope to blast radius; a 3-line simplification doesn't warrant a 20-minute test run.
- Broaden scope when the change has obvious wide reach — e.g., a heavily-imported utility was rewritten, or the code-quality reviewer's consolidation/dedup fixes modified shared code. This is a judgment call about ripple risk, not a mechanical rule.
- If the test runner has no scoping mechanism, run the full suite.
Surface any failure clearly with the failing check name and the relevant output. Do not relax assertions, weaken type signatures, or skip tests to make checks pass — that defeats the "preserves functionality" guarantee. Either fix the underlying break introduced by simplification, or revert the specific change that caused the regression.
If no test suite, lint, or typecheck is configured, state that explicitly in the summary; do not silently skip verification.
Step 5: Summarize
Briefly summarize what was good vs improved and fixed, including which checks were run and their results. If there were no findings to act on, confirm the code didn't require any changes.
Quantify the impact by dimension. Report what was actually applied, not a line count: fixes applied per reviewer dimension (reuse, quality, efficiency), how many findings were skipped as false-positive or not worth addressing, and the behavior-preservation result (checks run and outcome). For example: "Applied 6 — reuse 2, quality 3, efficiency 1; skipped 2 false positives; typecheck + lint clean, 11 scoped tests pass." Do not headline a net-lines-removed figure or frame fewer lines as the win — many clarity, safety, and efficiency fixes preserve or add lines. The measure is what improved and that behavior held, not how much code shrank.