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 fubits1/svelte-skills --skill css-nestinggit clone --depth 1 https://github.com/fubits1/svelte-skillsWrote 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/fubits1/svelte-skills/css-nesting)<a href="https://agentmods.dev/skills/fubits1/svelte-skills/css-nesting"><img src="https://agentmods.dev/badge/skills/fubits1/svelte-skills/css-nesting.svg" alt="Measured on agentmods" 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 | $0.00051 | $0.01760 |
| Opus 5 | $0.00026 | $0.00880 |
| Sonnet 5 | $0.00010 | $0.00352 |
| Haiku 4.5 | $0.00005 | $0.00176 |
Grade A, and why
css-nesting 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 6d 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 — 171 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CSS Nesting with Stylelint Compliance
Flat-to-nested CSS conversion breaks when done incrementally because each edit shifts specificity ordering, triggering cascading linter errors. This skill prevents that by requiring upfront analysis before any edits.
When This Applies
- Converting flat CSS selectors to nested
&syntax - Fixing
no-descending-specificityorno-duplicate-selectorserrors after nesting - Any CSS restructuring that changes selector source order
The Two Rules You Must Satisfy
no-descending-specificity
Selectors matching the same DOM element must appear in ascending specificity order in source. A .foo (0,1,0) appearing after .bar:hover .foo (0,3,0) is an error because both can match a .foo element.
Selectors matching different elements don't conflict regardless of order.
no-duplicate-selectors
Two rule blocks resolving to the same selector are forbidden. Nesting changes resolved selectors: & .child inside .parent resolves to .parent .child. A second .parent block is a duplicate even if the contents differ.
Exception: the same selector inside vs outside a @media block is allowed (different parent nodes).
The Workflow
Step 1: Map the DOM hierarchy
Write out the parent-child nesting from the HTML template:
.container
.wrapper
.item
.label
Step 2: List every selector with its specificity
For each selector in the flat CSS, calculate specificity and note which DOM element it matches:
.wrapper (0,1,0) matches .wrapper
.wrapper:hover (0,2,0) matches .wrapper
.item (0,1,0) matches .item
.wrapper:hover .item (0,3,0) matches .item
.label (0,1,0) matches .label
.container:has(:hover) .wrapper:not(:has(:hover)) (0,4,0) matches .wrapper
Step 3: Group by target element and sort ascending
For each element, the selectors that match it must appear in ascending specificity order in the final source:
What ships with it
1 file 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.
- 6d ago First seen · 171 lines · 51 tokens per session scan A 6d01af2df6af
css-nesting is a skill published in the GitHub repository fubits1/svelte-skills (10 stars, last pushed 1mo ago), licensed MIT. It adds 51 tokens to every session and 1,760 once invoked, about $0.0003 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 2026-08-31.
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