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 agentmods add skills/layoutit/polycss/chrome-tracenpx skills add layoutit/polycss --skill chrome-tracegit clone --depth 1 https://github.com/layoutit/polycssWhat 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 | $0.00082 | $0.01921 |
| Opus 5 | $0.00041 | $0.00960 |
| Sonnet 5 | $0.00016 | $0.00384 |
| Haiku 4.5 | $0.00008 | $0.00192 |
Grade A, and why
chrome-trace 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.
How it starts
The opening of the file, as written. The whole thing — 117 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Chrome Trace
Core Workflow
Use Playwright with Chromium and the Chrome DevTools Protocol Tracing domain to capture the exact interaction under investigation.
- Start from a reproducible page and action.
- Warm up the page until app-specific readiness is true.
- Start Chrome tracing and a
requestAnimationFramesampler immediately before the action. - Mark the action window with
performance.mark()andconsole.timeStamp(). - Perform the action with real Playwright input when the user is asking about input-driven behavior.
- Stop tracing after a short settle window.
- Align trace event timestamps to
performance.now()using the start/end marks. - Report where time went:
Scripting,Style,Layout,PrePaint,Paint, compositor main-thread work, compositor impl-thread work, raster, GPU/viz events, and the slowest frame windows.
Do not draw conclusions from FPS alone. Use FPS/frame-time summaries only as the symptom; use trace groups and top events as the explanation.
PolyCSS Trace Runners
Use scripts/trace.mjs as the front door:
pnpm bench:build
node .agents/skills/chrome-trace/scripts/trace.mjs motion --page nonvoxel --mesh glb:Elephant.glb --variant baseline --dom-samples --label elephant-baseline
node .agents/skills/chrome-trace/scripts/trace.mjs motion --page nonvoxel --mesh teapot --variant baseline --dom-samples --frame-details --layer-details --gpu-details --trace-out bench/results/teapot.trace.json --label teapot-enriched --report
node .agents/skills/chrome-trace/scripts/trace.mjs motion --page nonvoxel --mesh teapot --variant baseline --gpu-details full --trace-out bench/results/teapot-full-gpu.trace.json --label teapot-full-gpu
node .agents/skills/chrome-trace/scripts/trace.mjs drag --mesh teapot --mode baked --frame-details --label teapot-drag
node .agents/skills/chrome-trace/scripts/trace.mjs motion --mesh garden --report --markdown-out bench/results/garden-trace.md
node .agents/skills/chrome-trace/scripts/trace.mjs compare bench/results/before.json bench/results/after.json --markdown-out bench/results/trace-compare.md
What ships with it
5 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.
- 2d ago First seen · 117 lines · 82 tokens per session scan A 511dcc78c1b0
chrome-trace is a skill published in the GitHub repository layoutit/polycss (747 stars, last pushed 7d ago), licensed MIT. It adds 82 tokens to every session and 1,921 once invoked, about $0.0004 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 2026-08-30.
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