performance

A command for diagnosing or fixing performance problems in Bun and TypeScript programs. It includes a measurement workflow for comparing code before and after a change.

In plain words
What is it for?
Use it when code is slow, when benchmarking, or when deciding whether an optimization is worthwhile.
Why use it?
It helps separate real speed improvements from measurement noise and directs attention toward changes with the largest effect.

Command

Part of the bunjs plugin — 9 skills, 9 commands shipped together

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add commands/madappgang/magus/performance
Clone the repo
git clone --depth 1 https://github.com/MadAppGang/magus

Or install bunjs, the plugin that ships this one along with the rest of its 9 skills, 9 commands.

Per session 25 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 289 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00025 $0.00289
Opus 5 $0.00013 $0.00144
Sonnet 5 $0.00005 $0.00058
Haiku 4.5 $0.00003 $0.00029

Measured 2d ago against content hash 3d3ea0954e65, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

performance scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/bunjs/commands/performance.md · 23 lines

What it actually says

<user_request>$ARGUMENTS</user_request>

  1. Read skills/performance/SKILL.md in full first, resolved against this plugin's own directory (the tree this command was loaded from). It is the router: it names which files in skills/performance/references/ your task actually needs. Read those too before writing code.

Use this when something is slow, when benchmarking, or when deciding whether an optimisation is worth it.

  1. Measure before changing anything. Copy skills/performance/assets/perf/ and use the harness — it warms up, calibrates iterations against the measured ~42 ns clock granularity, and reports median/MAD rather than a mean that one GC pause destroys.
  2. Work the optimisation order: do it fewer times → off the request path → lazily → only then make it faster. An accidental O(n²) beats every micro-optimisation applied to it.
  3. Before reporting done: produce a before/after measurement from the same harness in the same session, including the spread. A change inside the noise band is not a change.
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 23 lines · 25 tokens per session scan A 3d3ea0954e65

Subscribe to this mod's changes

performance is a command published in the GitHub repository MadAppGang/magus (9 stars, last pushed 4d ago), licensed MIT. It adds 25 tokens to every session and 289 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.