Stylelint for Stylesheets in .NET Repositories

Trigger On

• the repo has

  stylelint.config.*

  ,

  .stylelintrc*

  , or CSS and SCSS assets under frontend folders
• the user asks for CSS linting, duplicate style cleanup, naming convention enforcement, or design-system guardrails
• the repo needs a stylesheet gate beyond formatting alone

Do Not Use For

• JavaScript or TypeScript ownership; route that to

  dotnet-eslint

  or

  dotnet-biome

• runtime accessibility, performance, SEO, or header checks; route that to

  dotnet-webhint

• repos that intentionally use only Biome for CSS linting and do not want a separate stylesheet linter

Inputs

• the nearest

  AGENTS.md

• package.json

• stylelint.config.*

  or

  .stylelintrc*

• the stylesheet file types in scope: CSS, SCSS, Less, embedded styles, or generated output

Workflow

1. Confirm what Stylelint should own:
   • plain CSS only
   • CSS plus SCSS
   • embedded styles in HTML, Markdown, or framework files
2. Prefer repo-local installation and checked-in config.
3. Start from a known shared config such as

   stylelint-config-standard

   , then add syntax-specific packages only when the repo truly needs them.
4. Add repeatable scripts to

   package.json

   , for example:

   • stylelint "**/*.{css,scss}"

   • stylelint "**/*.{css,scss}" --fix

5. Keep ignore patterns explicit so build output, vendored assets, and generated CSS do not pollute the signal.
6. Treat autofix as controlled cleanup:
   • run on a bounded scope first
   • inspect the diff
   • rerun the frontend build if the repo compiles styles
7. Use Stylelint for semantic CSS and selector policy, not as a replacement for site-level audits.

Bootstrap When Missing

1. Detect current state:

   • rg --files -g 'package.json' -g 'stylelint.config.*' -g '.stylelintrc*'

   • rg -n '"stylelint"|"stylelint-config-" --glob 'package.json' .

2. Prefer a repo-local install:

   • npm install --save-dev stylelint stylelint-config-standard

3. Add syntax packages only when the repo needs them for SCSS or embedded styles.
4. Create or refine

   stylelint.config.js

   ,

   stylelint.config.mjs

   , or the existing config format.
5. Add repeatable commands to

   AGENTS.md

   and

   package.json

   , then verify with:

   • npx stylelint "**/*.{css,scss}"

   • npx stylelint "**/*.{css,scss}" --fix

6. Return

   status: configured

   if Stylelint is now wired and repeatable, or

   status: improved

   if the existing baseline was tightened.
7. Return

   status: not_applicable

   only when another documented tool already owns stylesheet linting and migration is not requested.

Handle Failures

• Unknown rule

  usually means the config expects a plugin or a different Stylelint major version.

• Unknown word

  on SCSS, Vue, or mixed-content files usually means the repo needs the matching custom syntax package instead of plain CSS parsing.
• Massive autofix churn usually means generated assets or third-party CSS slipped into the lint target.
• Design-system rule noise should be handled by tuning the checked-in config, not by skipping the linter entirely.

Current 17.8 Guidance

• Stylelint

  17.8.0

  adds

  languageOptions.directionality

  ,

  property-layout-mappings

  ,

  relative-selector-nesting-notation

  , and

  selector-no-deprecated

  . Re-run the repo baseline after upgrading so any new selector or layout findings are reviewed instead of preserved by default.
• Use

  languageOptions.directionality

  explicitly when the repo styles bidirectional UI or logical properties. That keeps direction-sensitive rules aligned with the intended writing direction rather than inferred behavior.
• The earlier

  *syntax

  deprecation under

  declaration-property-value-no-unknown

  still matters on the 17.x line. If the repo still relies on those options, move the compatibility into

  customSyntax

  or parser selection instead of extending deprecated rule config.
• Keep repo ignores focused on generated or vendored assets. Re-check any broad ignore globs after upgrading so they are not masking selector or layout regressions that the new rules now catch.

Official Sources

• Stylelint 17.8.0 release notes

• references/release-notes.md

Deliver

• explicit stylesheet lint ownership
• checked-in config and repeatable commands
• clear scope boundaries for CSS, SCSS, and generated assets

Validate

• the lint target matches the repo's real stylesheet sources
• ignores exclude generated or vendored assets
• Stylelint ownership does not conflict with Biome without an explicit plan
• fixes were verified against the repo's stylesheet build flow when one exists

Ralph Loop

1. Plan: analyze current state, target outcome, constraints, and risks.
2. Execute one step and produce a concrete delta.
3. Review the result and capture findings.
4. Apply fixes in small batches and rerun checks.
5. Update the plan after each iteration.
6. Repeat until outcomes are acceptable.
7. If a dependency is missing, bootstrap it or return

   status: not_applicable

   with a reason.

Required Result Format

• status

  :

  complete

  |

  clean

  |

  improved

  |

  configured

  |

  not_applicable

  |

  blocked

• plan

  : concise plan and current step

• actions_taken

  : concrete changes made

• verification

  : commands, checks, or review evidence

• remaining

  : unresolved items or

  none

Example Requests

• "Add Stylelint for the SCSS in this ASP.NET Core app."
• "Block duplicate selectors and invalid CSS in CI."
• "Fix the current Stylelint violations without touching generated CSS."

References

• release-notes.md - Current 17.8.0 release changes that matter for repo config, rule tuning, and selector/layout validation