Borrowing it
Nothing to install: this file belongs to computesdk/benchmarks. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/computesdk/benchmarks/master/.agents/skills/writing-benchmarks/SKILL.mdgit clone --depth 1 https://github.com/computesdk/benchmarksWrote 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/computesdk/benchmarks/writing-benchmarks)<a href="https://agentmods.dev/skills/computesdk/benchmarks/writing-benchmarks"><img src="https://agentmods.dev/badge/skills/computesdk/benchmarks/writing-benchmarks/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/computesdk/benchmarks/writing-benchmarks"><img src="https://agentmods.dev/badge/skills/computesdk/benchmarks/writing-benchmarks.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00073 | $0.02150 |
| Opus 5.5 | $0.00029 | $0.00860 |
| Sonnet 5.5 | $0.00015 | $0.00430 |
| Haiku 4.5 | $0.00007 | $0.00215 |
Grade A, and why
writing-benchmarks 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 1mo 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 — 169 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Writing a benchmark
A benchmark is a unit of work (what one iteration measures) expressed as a
declarative *.bench.ts file that exports exactly config + task. The
bench run CLI owns orchestration — the file never calls the runner itself.
Canonical API reference: WRITING_BENCHMARKS.md (repo root) — read it for the
full field tables. Runnable templates: examples/01-hello.bench.ts through
11-logging.bench.ts. Reference implementations:
benchmarks/sandbox/tti.bench.ts— minimal sandbox benchmark (create → exec → destroy, one metric).benchmarks/sandbox/dax.bench.ts— rich benchmark (work measured inside the sandbox, pre-measured phase steps,TaskError, legacy results writer).
1. Define the unit of work
Before writing code, pin down:
- Timed boundary — what starts the clock and what ends it. For TTI that's
sandbox.create()→ first command succeeding; destroy is excluded. Write the boundary in the file's header comment. - Uniformity — the task body must run identically for every participant.
Push provider differences into participant config (
sandboxOptions,timeout,destroyTimeoutMs), never intoif (provider === ...)branches inside the task. - Headline metric(s) — the numbers the task reports via
measure()and what counts as a success (exit-code checks,scoring.success.requireData). - Load profile — which of
iterations,concurrency,staggerDelayMsdefine the benchmark vs. stay CLI-overridable. Ashapemay set slug/name/staggerDelayMs, neveriterations/concurrency. See § Horizontal load.
2. Horizontal load — iterations × concurrency
Horizontal load (how many units of work run at once, and how fast they ramp) is controlled entirely by three config/CLI knobs — the task function itself never manages parallelism:
iterations— total tasks per participant. Each iteration is one full unit of work (one sandbox create → work → destroy). This is the horizontal volume knob:iterations: 100launches 100 sandboxes per participant.concurrency— max tasks in flight at once.1= sequential (one-at-a-time cold starts),N= up to N units of work running simultaneously.iterations: N, concurrency: Nis a burst: all N sandboxes launch at once.staggerDelayMs— task i launches ati * staggerDelayMs. Combined withconcurrency: Nthis is a staggered ramp (e.g. 100 sandboxes, one every 200ms) — measures how TTI degrades as load ramps.
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.
- 1mo ago First seen · 169 lines · 73 tokens per session scan A a8364682305e
writing-benchmarks is a skill published in the GitHub repository computesdk/benchmarks (131 stars, last pushed yesterday), licensed MIT. It adds 73 tokens to every session and 2,150 once invoked, about $0.0003 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 2026-09-27.
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