test262-pass-rates

test262-pass-rates is a skill for Claude Code from loopdive/js2. It costs 48 tokens per session (809 once invoked), scanned A, original, Apache-2.0.

A quick check of committed Test262 pass rates for two JavaScript compiler targets. Test262 is the standard test suite used to check JavaScript language compatibility.

In plain words
What is it for?
Use it to check the latest recorded pass and total counts for the js-host and standalone compiler targets and confirm which main-branch revision they represent.
Why use it?
It provides a current conformance snapshot without running tests or downloading data, while showing the two targets separately.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Good fit Use it to check the latest recorded pass and total counts for the js-host and standalone compiler targets and confirm which main-branch revision they represent.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/loopdive/js2/test262-pass-rates
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.

Any agent
npx skills add loopdive/js2 --skill test262-pass-rates
Clone the repo
git clone --depth 1 https://github.com/loopdive/js2

Made for: Claude Code.

Wrote 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.

agentmods badge for test262-pass-rates

README.md
[![agentmods](https://agentmods.dev/badge/skills/loopdive/js2/test262-pass-rates/github.svg)](https://agentmods.dev/skills/loopdive/js2/test262-pass-rates)
Your own site
<a href="https://agentmods.dev/skills/loopdive/js2/test262-pass-rates"><img src="https://agentmods.dev/badge/skills/loopdive/js2/test262-pass-rates/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.

agentmods 80×15 button for test262-pass-rates

Your own site · 80×15
<a href="https://agentmods.dev/skills/loopdive/js2/test262-pass-rates"><img src="https://agentmods.dev/badge/skills/loopdive/js2/test262-pass-rates.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 48 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 809 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 5.1 $0.00048 $0.00809
Opus 5.5 $0.00019 $0.00324
Sonnet 5.5 $0.00010 $0.00162
Haiku 4.5 $0.00005 $0.00081

Measured 1mo ago against content hash d07a6787c05c, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

test262-pass-rates 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.

.claude/skills/test262-pass-rates/SKILL.md · 49 lines

How it starts

The opening of the file, as written. The whole thing — 49 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Test262 Pass Rates (js-host vs standalone)

Prints the current committed test262 conformance numbers for both compile targets side by side. Reads two committed, CI-refreshed summary files directly — no test run, no network fetch, near-instant.

Data sources

  • js-host (gc target): benchmarks/results/test262-current.json — refreshed by the promote-baseline job in test262-sharded.yml on every push to main. Use .summary (or .official_summary if present) for pass/total, and .summary.host_free_pass for the narrower "passes with zero host imports" count (not the same as a standalone-target run — see below).
  • standalone target: benchmarks/results/test262-standalone-highwater.json — refreshed alongside the js-host baseline (same sha/generated_at). Use .official_pass / .official_total for the genuine standalone-target compile+run pass rate.

Both files are committed to the repo (small, ~KB-scale) and always reflect the last successful push-to-main run — check .timestamp/.generated_at and .sha against git -C /workspace log -1 --format=%H to confirm freshness; if the sha doesn't match current main, note that the numbers are as-of the last CI run, not live.

Steps

  1. Read both files:
node -e "
const host = require('/workspace/benchmarks/results/test262-current.json');
const sa = require('/workspace/benchmarks/results/test262-standalone-highwater.json');
const h = host.official_summary ?? host.summary;
const hostPct = (100 * h.pass / h.total).toFixed(1);
const saPct = (100 * sa.official_pass / sa.official_total).toFixed(1);
const gap = h.pass - sa.official_pass;
console.log('js-host (gc):   ' + h.pass + ' / ' + h.total + '  (' + hostPct + '%)');
console.log('standalone:     ' + sa.official_pass + ' / ' + sa.official_total + '  (' + saPct + '%)');
console.log('honest gap:     ' + gap + ' tests pass under js-host but not standalone');
console.log('baseline sha:   ' + host.baseline_sha);
console.log('generated at:   ' + host.timestamp);
"

Read the full file on GitHub · 49 lines

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. 1mo ago First seen · 49 lines · 48 tokens per session scan A d07a6787c05c

Subscribe to this mod's changes

test262-pass-rates is a skill published in the GitHub repository loopdive/js2 (67 stars, last pushed today), licensed Apache-2.0. It adds 48 tokens to every session and 809 once invoked, about $0.0002 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.