agentmods.dev

vscode css-best-practices.instructions.md

Coding guidance for writing and reviewing CSS, focused on selectors and UI state styles.

In plain words
What is it for?
Use it when creating or reviewing CSS selectors, especially styles that depend on component state or generated class names.
Why use it?
It helps avoid CSS patterns that can trigger unnecessary style recalculation and make styles harder to maintain.

Instructions file for GitHub Copilot

190k yesterday A scan 272 tokens original MIT
View the source file microsoft/vscode
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.

agentmods
npx agentmods add instructions/microsoft/vscode/css-best-practices
Clone the repo
git clone --depth 1 https://github.com/microsoft/vscode

Made for: GitHub Copilot.

Per session 272 This file is loaded in full into every session.
When invoked 272 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
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 $0.00272 $0.00272
Opus 5 $0.00136 $0.00136
Sonnet 5 $0.00054 $0.00054
Haiku 4.5 $0.00027 $0.00027

Measured yesterday against content hash 92e9835ddb8c, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

vscode css-best-practices.instructions.md 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.

.github/instructions/css-best-practices.instructions.md · 12 lines

What it actually says

CSS Best Practices

Selectors

  • Avoid :has() selectors. Because their result depends on descendant state, DOM mutations can invalidate styles on ancestors and cause expensive style recalculation, especially when selectors are broadly scoped. Instead, represent the state explicitly with a class or data attribute on the smallest container you own, and scope selectors to that marker. Add and remove the marker together with the state it represents.
  • Never match the class attribute by substring ([class*="…"], [class^="…"], [class$="…"]). A single such selector anywhere in the workbench stylesheet defeats Blink's per-class invalidation: every classList change then forces a style recalculation for that element, even when no rule references the class that changed. Measured on a 3.7k-node workbench, the ten [class*="monaco-decoration-itemColor"] selectors in the Modern UI tab styles alone made a full style recalculation 2.4x slower. When a class carries a generated suffix, have the code that applies it also set a stable marker class (see DECORATION_LABEL_COLOR_CLASS) and match that instead.
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. yesterday First seen · 12 lines · 272 tokens per session scan A 92e9835ddb8c

Subscribe to this mod's changes

vscode css-best-practices.instructions.md is an instructions file published in the GitHub repository microsoft/vscode (190,061 stars, last pushed yesterday), licensed MIT. It adds 272 tokens to every session, about $0.0014 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.

FrontendLanguagesWriting and docseditorelectronmicrosofttypescriptvisual-studio-code
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