SEED is a design system that provides shared visual tokens, styling recipes, and UI components for React, iOS, Android, and Lynx, with Figma integration. It is used to build consistent products across platforms; the catalogue add-ons support agents working with its components, tools, documentation, and development workflows.
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 daangn/seed-design --skill chromatic-diffgit clone --depth 1 https://github.com/daangn/seed-designWrote 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/daangn/seed-design/chromatic-diff)<a href="https://agentmods.dev/skills/daangn/seed-design/chromatic-diff"><img src="https://agentmods.dev/badge/skills/daangn/seed-design/chromatic-diff/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/daangn/seed-design/chromatic-diff"><img src="https://agentmods.dev/badge/skills/daangn/seed-design/chromatic-diff.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 | $0.00026 | $0.02769 |
| Opus 5 | $0.00013 | $0.01385 |
| Sonnet 5 | $0.00005 | $0.00554 |
| Haiku 4.5 | $0.00003 | $0.00277 |
Grade A, and why
chromatic-diff 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 yesterday.
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 — 149 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Chromatic Diff Investigation
Chromatic tells you that a snapshot changed. It does not tell you why. This skill closes that gap: it resolves a Chromatic URL into the two builds being compared, puts both published Storybooks on localhost, and renders the same story from each so the difference can be read as structure, computed style, and token values rather than pixels.
Working from the rendered page rather than the snapshot image matters, because the useful answers are named things — "the dark-theme surface token changed", "this element gained a wrapper", "both builds render identically, so the snapshot is flaky". A pixel diff cannot say any of those.
How far you are allowed to go
Read this before the workflow. The steps below assume three things are present, and which of them this session actually has decides how much of the workflow exists for you:
| What is missing | How far this skill goes |
|---|---|
CHROMATIC_TOKEN |
Nowhere. Nothing else authenticates this API. Say it is missing, point at references/token.md, stop. |
| Bun | Nowhere. Say Bun is not installed, stop. |
| a chrome-devtools driver, meaning the MCP tools or the CLI | Steps 1 and 2. Report those, name the gap, stop. |
| nothing | Steps 1 through 5. |
Finishing the investigation is not the goal; a trustworthy answer is.
One row admits an exception. Bun installed but unreachable from PATH is an environment quirk rather than a missing capability, so finding the binary and calling it by absolute path is fine, provided the answer says you did it. Step 0 detects the situation and prints OFF PATH into the env: line for exactly that reason. Bun genuinely absent from the machine is the row above.
Do not route around a missing piece
Two workarounds sit within reach, and neither is the fallback:
- Playwright, Puppeteer, or headless Chrome launched from a shell — step 4's checks are written against the chrome-devtools tool surface, and an improvised driver drops them without saying so.
- Chromatic's own comparison images — the one substitution that changes what the answer rests on, so it is refused whatever else is present. A run that stopped reports what it has instead of filling the gap with pixels.
What ships with it
6 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.
- yesterday Changed · -141 tokens per session 910fe53caff1
- 5d ago First seen · 149 lines · 167 tokens per session scan A 48ccc6bfe608
chromatic-diff is a skill published in the GitHub repository daangn/seed-design (1,106 stars, last pushed today), licensed Apache-2.0. It adds 26 tokens to every session and 2,769 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 2026-09-04.
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