Perf Issue

---
name: perf-issue
description: Fix one performance defect using representative before and after traces and a correctness gate.
---

# Perf issue

Define the user's slow path, surface, workload, and metric. Capture a baseline
trace or profile through the real control surface before changing code. Use
[how](../how/SKILL.md) to connect cost to architecture. Do not claim a ceiling
or bottleneck by reading source alone.

Vet the baseline and each later number with
[benchmark-checklist](../benchmark-checklist/SKILL.md). Record successful and
failed work counts, tuning, repeated samples, spread, and the measured limiter.
If the requested task is only measurement validation, stay in that workflow.

Try hypotheses supported by the trace in this order: do not do unused work;
avoid repeated work; do less; do it later; move it outside the interactive
moment; do it concurrently; then do it cheaper. Stop when an earlier strategy
meets the target. A source read establishes that work is unused; a trace alone
does not authorize deletion. More specific mechanisms remain hypothesis tools,
not a checklist:
 remove unnecessary work; divide
scaling work; cache repeated work with explicit invalidation; index or add
indirection; batch fixed overhead; duplicate a dominant wait when capacity
allows; defer unused work; or schedule necessary work outside the critical
moment. These are hypothesis families, not a checklist to implement blindly.

Make one bounded change, using [architect](../architect/SKILL.md) if it alters
module boundaries. Review the diff, capture a post-change trace under the same
workload, compare numeric artifacts using a repeatable command, and run the
correctness gate. A change that improves one number but breaks the user flow
does not pass. A noisy or different-surface comparison is inconclusive.

Return baseline, after value, delta, trace paths, correctness result, and
remaining uncertainty. For sustained repeated iterations, route to
[hillclimb](../hillclimb/SKILL.md). Publish only when the user requested it.