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.
npx skills add dean0x/devflow --skill performancegit clone --depth 1 https://github.com/dean0x/devflowWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/dean0x/devflow/performance)<a href="https://agentmods.dev/skills/dean0x/devflow/performance"><img src="https://agentmods.dev/badge/skills/dean0x/devflow/performance/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/dean0x/devflow/performance"><img src="https://agentmods.dev/badge/skills/dean0x/devflow/performance.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00019 | $0.01269 |
| Opus 5.5 | $0.00008 | $0.00508 |
| Sonnet 5.5 | $0.00004 | $0.00254 |
| Haiku 4.5 | $0.00002 | $0.00127 |
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 7d 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.
How it starts
The opening of the file, as written. The whole thing — 136 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Performance Patterns
Domain expertise for performance optimization and bottleneck detection. Use alongside devflow:review-methodology for complete performance reviews.
Iron Law
MEASURE BEFORE OPTIMIZING
Profile first, optimize second. Every performance claim requires benchmarks. Brendan Gregg's USE Method [1] (Utilization, Saturation, Errors) and Tom Wilkie's RED Method [2] (Rate, Errors, Duration) are the systematic starting points — not guesswork. Gil Tene's coordinated omission warning [8]: averages lie — monitor P99, not mean latency.
Measurement Foundation [1][2][7][8][9]
| Method | For | Measures |
|---|---|---|
| USE Method [1] | System resources | Utilization, Saturation, Errors per resource |
| RED Method [2] | Services | Rate, Errors, Duration per endpoint |
| Flame Graphs [9] | CPU hot paths | Widest frames = hottest code — optimize those |
| HDR Histogram [8] | Latency | Full distribution without coordinated omission |
Latency hierarchy [7]: L1 cache ~1ns · L2 ~4ns · L3 ~40ns · RAM ~100ns · SSD ~100µs · Network (DC) ~500µs · HDD ~10ms. Knowing these prevents optimizing the wrong layer [4].
Performance Categories
1. Algorithmic Issues [5][12]
N+1 Query Problem — database query inside a loop. O(n) round-trips [5].
// VIOLATION: 1 + N queries — O(n) round-trips [5]
for (const user of users) {
user.orders = await db.orders.findByUserId(user.id);
}
// CORRECT: Batch query with Map lookup — O(1) per access [5]
const orders = await db.orders.findAll({ where: { userId: userIds } });
const ordersByUser = new Map(groupBy(orders, 'userId'));
users.forEach(u => u.orders = ordersByUser.get(u.id) || []);
O(n²) Patterns — linear search inside a loop [12].
// VIOLATION: Array.includes is O(n), called n times → O(n²) [12]
items.filter(item => selected.includes(item.id));
// CORRECT: Set lookup is O(1) → total O(n) [12]
const selectedSet = new Set(selected);
items.filter(item => selectedSet.has(item.id));
What ships with it
4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 7d ago Changed · -7 tokens per session 9d76a9105946
- 1mo ago First seen · 136 lines · 26 tokens per session scan A 426f9c5c96c7
performance is a skill published in the GitHub repository dean0x/devflow (20 stars, last pushed today), licensed MIT. It adds 19 tokens to every session and 1,269 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-08-30.
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