perf

perf

Structured performance investigation with baselines, profiling, and evidence-backed decisions - run by AI agents inside your editor.

Why

Performance work without structure leads to random micro-optimizations, unmeasured changes, and wasted time. /perf enforces a rigorous 10-phase methodology - derived from recorded real investigation sessions - that ensures every optimization is baselined, isolated, measured, and documented.

Use cases:

• Investigating a reported performance regression
• Establishing baselines before and after a refactor
• Finding breaking points under load
• Profiling CPU and memory hotspots with language-native tools
• Making evidence-backed continue/stop decisions on optimization efforts

Installation

agentsys install perf

Requires agentsys to be set up in your project.

Quick Start

/perf --phase setup --scenario "API response time regression" --command "npm run bench" --version v1.2.0

This initializes an investigation, records the scenario, and prepares for baselining. The orchestrator walks you through each phase sequentially, checkpointing progress after every step.

To resume an in-progress investigation:

/perf --resume

How It Works

Every investigation follows 10 phases in order. The orchestrator enforces strict rules: sequential benchmarks only, 60-second minimum run durations, one change per experiment, and checkpoint commits after each phase.

1. Setup - Confirm the scenario, success criteria, and benchmark command. The benchmark must emit metrics between PERF_METRICS_START / PERF_METRICS_END markers.

2. Baseline - Run the benchmark for 60+ seconds with a 10-second warmup. Results are stored as baselines/<version>.json. This is the reference point for all comparisons.

3. Breaking point - Binary search across a parameterized range to find the threshold where performance degrades. Uses 30-second runs (the only exception to the 60-second rule).

4. Constraints - Run the benchmark under CPU and memory limits (default: 1 CPU, 1GB RAM). Compare against the unconstrained baseline to identify resource sensitivity.

5. Hypotheses - Generate up to 5 hypotheses about the root cause, each backed by evidence from git history and code analysis. No guessing - every hypothesis needs a file path or commit reference.

6. Code paths - Use repo-intel to identify entry points, hot files, and call chains relevant to the scenario. Narrows the search space before profiling.

7. Profiling - Run language-specific profilers: --cpu-prof for Node.js, JFR for Java, cProfile for Python, pprof for Go. Capture file:line hotspots and flame graphs.

8. Optimization - Apply one change at a time. Validate with 2+ benchmark runs. Revert between experiments to keep the baseline clean.

9. Decision - Based on measured improvement, decide whether to continue optimizing or stop. The verdict and rationale are recorded in the investigation log.

10. Consolidation - Write the final baseline, close the evidence log, and mark the investigation complete.

Usage

/perf --phase setup --scenario "startup time" --command "node bench.js" --version v2.0.0
/perf --resume                                          # continue where you left off
/perf --resume --phase profiling                        # jump to a specific phase
/perf --resume --phase baseline --runs 5 --aggregate median
/perf --resume --phase optimization --change "replaced O(n^2) loop with hash lookup"
/perf --resume --phase decision --verdict continue --rationale "20% improvement"

Key Flags

Flag	Description
--resume	Continue the active investigation
--phase <name>	Target a specific phase
--command <cmd>	Benchmark command (must emit PERF_METRICS markers)
--version <ver>	Baseline version label
--duration <sec>	Override benchmark duration (default 60s)
--runs <n>	Number of runs for multi-run benchmarks
--aggregate <method>	median, mean, min, or max (default median)
--change <summary>	Description of the optimization being tested
--verdict <v>	continue or stop

Investigation Artifacts

State is persisted under {state-dir}/perf/: investigation.json (active state), investigations/<id>.md (evidence log), and baselines/<version>.json (metrics per version).

Architecture