/performance-review

name: performance-review
description: Detects time and space complexity hotspots via AST scan. Use when code feels slow, before performance-sensitive merges, or to find O(n²) regressions.
alwaysApply: false
category: code-quality
tags:
- performance
- complexity
- algorithms
- ast
- static-analysis
tools: []
usage_patterns:
- hotspot-detection
- complexity-review
- pre-merge-performance-check
complexity: advanced
estimated_tokens: 280
progressive_loading: true
dependencies:
- imbue:proof-of-work
- imbue:review-core
- imbue:structured-output
modules:
- modules/time-complexity.md
- modules/space-complexity.md
- modules/gauntlet-integration.md
- modules/kuva-visualization.md
- modules/memory-allocation-lenses.md

Performance Review

Static-analysis review of time and space complexity hotspots.

The skill runs in three escalating tiers. Tier 1 uses Python's stdlib `ast` and always runs. Tier 2 uses tree-sitter to extend detection to JS/TS, Go, Rust, Java, and C/C++ when the `tiers` extra is installed. Tier 3 walks the gauntlet call graph forward from each finding and raises its severity one step when a callee holds a hotspot, and runs when the gauntlet plugin is importable and a `.gauntlet/graph.db` exists. Without them, Tiers 2 and 3 no-op and Tier 1 still produces findings on Python source.

Quick Start

/performance-review                  # scan changed files
/performance-review path/to/file.py  # scan one file
/performance-review --tier 1         # force Tier 1 only

Programmatic use:

from pensive.skills.performance_review import PerformanceReviewSkill

skill = PerformanceReviewSkill()
result = skill.analyze(context, "src/module.py")
for f in result.issues:
    print(f"[{f.severity}] {f.file}:{f.line} {f.message}")

When To Use

• Pre-merge review of code that runs on user-scaled inputs.
• Triage of a function that "feels slow" before reaching for a

profiler.

• Audit a refactor for newly introduced O(n²) patterns.
• Guardrail for AI-generated code where nested-loop hot spots

are common.

When NOT to Use

• The target needs **runtime** measurement (memory profile, CPU

time on real data). Use `Skill(parseltongue:python-performance)` instead: that skill drives `cProfile`, `py-spy`, and benchmarks.

• General refactoring guidance not focused on hotspots: use

`Skill(pensive:code-refinement)` whose `algorithm-efficiency` module covers broader optimization patterns. This skill detects; that skill teaches.

• Deciding whether a hand-rolled loop transform (unrolling, manual

SIMD, strength reduction) is worth keeping: use `Skill(leyline:loop-optimization)` for the hand-vs-compiler rule. This skill flags hotspot shapes, not transformation choices.

• Architecture-level performance (sharding, caching layers,

queue placement): use `Skill(pensive:architecture-review)`.

Required Progress Items

1. `perf-review:context-established` 2. `perf-review:scan-complete` 3. `perf-review:findings-categorized` 4. `perf-review:integration-checked` 5. `perf-review:report-generated` 6. `perf-review:findings-verified`

Workflow

Step 1: Context (`perf-review:context-established`)

• Identify target files. If invoked with no argument, use

`git diff --name-only`. If invoked with a path, scope to that.

• Note language(s) involved. Tier 1 covers Python; non-Python

files need the `tiers` extra for Tier 2 coverage.

Step 2: Tier 1 AST scan (`perf-review:scan-complete`)

Load `modules/time-complexity.md` for the time-side patterns and `modules/space-complexity.md` for space-side. Each module documents the AST shape of every detector.

Alongside the automated scan, load `modules/memory-allocation-lenses.md` and apply its three manual lenses (unbounded external-source collections, hot-path recompute, serial blocking I/O) by reading the target files.

For each Python target file, call:

from pensive.skills.performance_review import PerformanceReviewSkill

result = PerformanceReviewSkill().analyze(context, path)

The visitor walks the AST once and emits `ReviewFinding` records.

Step 3: Categorize and rank (`perf-review:findings-categorized`)

Group findings by severity:

• **HIGH**: O(n²) or worse on input-sized iterables (T1, T2).
• **MEDIUM**: Unbounded allocation or per-iteration overhead

(T3, T4, S1, S3).

• **LOW**: Style-level inefficiencies (T5, T6, S2).
• **CRITICAL**: Reserved for Tier-3 transitive upgrades.

Within a severity, sort by file then line. Suppress findings the user has explicitly marked acceptable (TODO/comment markers) at module-load time of the target.

Step 4: Tier 2/3 enrichment (`perf-review:integration-checked`)

Load `modules/gauntlet-integration.md` for the contract.

If `tree_sitter_language_pack` is importable, run Tier 2 on non-Python files that were skipped at Step 2. If gauntlet is importable and a `.gauntlet/graph.db` exists in the scanned file's directory or any parent, run Tier 3 to upgrade severities based on hotspots in transitive callees.

Without the extra, this step is a no-op and the report notes "Tier 2/3 not available: install pensive with the `tiers` extra for multi-language and call-chain coverage." A file that tree-sitter cannot parse adds a warning and yields no Tier 2 findings.

Step 5: Report (`perf-review:report-generated`)

Emit a markdown report:

## Performance Review: <target>

### HIGH (<count>)
- src/foo.py:42: Nested loop over the same iterable 'items'.
  Suggestion: sort + two pointers, or hash-set membership.

### MEDIUM (<count>)
- ...

### LOW (<count>)
- ...

Tier coverage: 1 (always) | 2 (gauntlet ✓/✗) | 3 (graph ✓/✗)

The report is informational. Apply fixes via `Skill(pensive:code-refinement)` or hand-merge.

Tiered Analysis

| Tier | Source | When it runs | What it covers | |------|--------|--------------|----------------| | 1 | stdlib `ast` | Always (Python source only) | T1-T6, S1-S3 | | 2 | `tree_sitter_language_pack` | When importable,