StyleSpeak - MCP and CLI

A companion MCP server and CLI to stylesafe that makes CSS legible to AI agents — resolving cascade, tracing properties, predicting change impact, and explaining what applies and why before an agent touches a single line of styles.

The problem

AI coding agents write CSS without being able to see its effect. They modify a rule, assume it worked, and move on — unaware that a higher-specificity rule elsewhere already overrides it, a combinator rule in another file is silently winning, or a CSS variable resolves to something entirely different than expected. stylespeak gives agents a structured knowledge layer to consult before making changes.

Related MCP server: @designjs/mcp-server

What it does

resolve_styles — answers "what CSS actually applies to this selector?"

Given a selector and a set of files, returns every CSS property the selector would receive, which rule wins for each, and which rules were overridden — with confidence levels since no real DOM is available. CSS custom properties (var()) are resolved to their actual values, including chained variables, fallbacks, and media-context overrides.

trace_property — answers "everywhere this property is set, who wins?"

Given a property name and a set of files, returns every rule that sets it, groups competing rules that target overlapping selectors, and shows the full cascade chain for each group — with resolved variable values included.

impact_preview — answers "if I change this, what else breaks?"

Given a selector, property, and optional new value, predicts the full blast radius of the change before it's made — showing which selectors will see a different value, which are shielded by higher specificity, which cascade relationships are uncertain, and which downstream rules are affected through CSS variable chains or property inheritance. Works without a browser.

style_manifest — answers "what does this entire project's CSS look like at a glance?"

Builds a compressed, structured summary of a project's entire CSS knowledge — selectors, properties, variables, competition groups, and risk hotspots — that an agent can load once at the start of a session and keep in context instead of repeatedly querying individual files.

live_resolve — answers "what does the browser actually compute for this selector?"

Queries a running Chromium browser via CDP and returns exact computed styles and matched rules. No heuristics, no confidence levels — the browser resolved it. Requires Chrome running with --remote-debugging-port=9222.

Works on more than plain CSS. The four static tools above analyze .css, .scss, CSS Modules, and — as of v1.3 — styled-components and Emotion source files (.js / .jsx / .ts / .tsx), all through the same cascade engine.

Quick start

As a CLI tool

npm install -g @patrizzos/stylespeak

stylespeak resolve ".btn.primary" src/styles/main.css
stylespeak trace "color" --projectRoot src/styles
stylespeak impact ".btn" "background-color" src/styles/main.css --newValue "#ff0000"
stylespeak manifest --projectRoot src/styles

# styled-components / Emotion — components are addressed by variable name (const Button = styled.button`` -> .Button)
stylespeak resolve ".Button" src/components/Button.jsx
stylespeak manifest --projectRoot src

As an MCP server

Add to your MCP client config (Cursor: .cursor/mcp.json, VS Code: .vscode/mcp.json):

{
  "mcpServers": {
    "stylespeak": {
      "command": "node",
      "args": ["/absolute/path/to/stylespeak/src/server.js"]
    }
  }
}

Once connected, agents can call:

• resolve_styles({ selector, files, projectRoot, componentFiles? })

• trace_property({ property, files, projectRoot })

• impact_preview({ selector, property, newValue?, files, projectRoot })

• style_manifest({ files?, projectRoot?, maxSelectors? })

• live_resolve({ selector, port?, tabUrl? })

Example output

impact_preview

stylespeak impact ".btn" "background-color" src/styles/buttons.css --newValue "#ff0000"

{
  "change": {
    "selector": ".btn",
    "property": "background-color",
    "currentValue": "var(--color-primary)",
    "newValue": "#ff0000"
  },
  "blastRadius": {
    "total": 3,
    "valueChanges": 1,
    "shielded": 1,
    "risks": 0,
    "variableDownstream": 0,
    "inheritanceDownstream": 1
  },
  "riskLevel": "low",
  "safeToChange": true,
  "impacts": [
    {
      "type": "value-change",
      "affectedSelector": ".btn",
      "currentValue": "var(--color-primary)",
      "newValue": "#ff0000",
      "confidence": "certain"
    },
    {
      "type": "shielded",
      "affectedSelector": ".btn.primary",
      "shieldingValue": "darkblue",
      "confidence": "certain",
      "reason": ".btn.primary has higher specificity — elements with both classes won't be affected"
    }
  ],
  "summary": "1 selector will see a different value, 1 selector is shielded by higher specificity.",
  "agentNote": "Change appears safe to make. Shielded selectors are safe — higher-specificity rules protect those elements."
}

resolve_styles

stylespeak resolve ".btn" src/styles/buttons.css

{
  "properties": {
    "background-color": {
      "winner": {
        "value": "var(--color-primary)",
        "resolvedValue": "#2563eb",
        "variableChain": ["--color-primary → #2563eb"],
        "selector": ".btn",
        "specificity": "(0,0,1,0)"
      },
      "confidence": "certain"
    }
  },
  "variables": { "--color-primary": { "value": "#2563eb", "selector": ":root" } }
}

Confidence levels

CSS custom property resolution

As of v0.2, stylespeak fully resolves CSS custom properties (var()) in all output:

• value — the raw value as written (var(--color-primary))

• resolvedValue — the actual resolved value (#2563eb)

• variableChain — the full resolution path, including chained variables

• conditionalValues — media-context overrides where the variable resolves differently

Supported: simple, fallback, nested fallback, chained, scoped, media-context, circular reference protection.

CSS-in-JS support (styled-components & Emotion)

As of v1.3, stylespeak statically extracts styles from .js, .jsx, .ts, .tsx, .mjs and .cjs files that import styled-components, @emotion/styled, @emotion/react or @emotion/css, and runs them through the same cascade engine as plain CSS. resolve_styles, trace_property, impact_preview and style_manifest all work on them, and CSS-in-JS and regular CSS can be analyzed together.

Pass JS/TS files in files, or point projectRoot at a directory — files that import one of these libraries are discovered automatically and all other JS/TS files are ignored.

Addressing components

Generated class names are hashed at runtime, so each styled component is addressed by its variable name as a class selector:

const Button = styled.button`...`;    // -> .Button
export default styled.section`...`;   // -> .Card  (named after the file, e.g. Card.jsx)

Rules are tagged cssInJs, library and component, and are treated as locally scoped (like CSS Modules): two components named Wrapper in different files are independent, never reported as conflicting, and never counted as a "declared in N locations" risk. Querying such a name is flagged as ambiguous, because results will mix both files.

What is extracted

What is flagged, never guessed

Values that depend on props or theme can't be known statically. stylespeak keeps the original expression, marks it, and tells the agent:

"color": {
  "winner": {
    "value": "${props => props.color}",
    "selector": ".Button",
    "cssInJs": true,
    "library": "styled-components",
    "component": "Button",
    "dynamic": true
  },
  "confidence": "certain",
  "dynamic": true
}

• dynamic: true on a declaration, winner and property means the value depends on runtime props/theme — the winner may differ depending on props.

• Conditional blocks and mixin calls (${p => p.active && css…}) can't be evaluated. They are dropped and counted in dynamicInterpolations, and agentNote warns that additional styles may apply at runtime.

• Style blocks that can't be attached to a selector are listed in cssInJs.skipped in style_manifest output instead of being silently ignored.

• styled(Base) records extends; agentNote tells the agent to also resolve the base component.

Limitations

This is static analysis, so there are boundaries:

• styled(Base) does not merge the base component's styles into the child — resolve the base selector separately.

• Constants and theme objects imported from other files are not resolved (same-file only). ThemeProvider themes are not resolved.

• Emotion's css prop on JSX elements and style blocks not assigned to a named variable are anonymous — there is no selector to target, so they are reported as skipped.

• keyframes are not modeled, and .attrs({ className }) is not considered.

• Cross-file injection order is approximated by the order files are provided.

• For ground truth on a running app, use live_resolve against the real element.

How it pairs with stylesafe

stylesafe catches problems in your CSS — conflicts, dead rules, Tailwind clashes — before they ship.

stylespeak explains your CSS — resolving cascade, tracing properties, predicting impact, resolving variables — so agents understand before they act.

Use stylesafe as a post-edit check. Use stylespeak as a pre-edit consultation. Together they give AI coding agents a complete feedback loop on styles.

Live browser inspection

live_resolve requires a Chromium browser running with remote debugging enabled:

# Windows
chrome.exe --remote-debugging-port=9222

# macOS
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --remote-debugging-port=9222

# Linux
google-chrome --remote-debugging-port=9222

Security note: Never run --remote-debugging-port on a machine exposed to untrusted networks or in production. This flag opens a local API that any process on the machine can connect to.

File format support

Architecture

src/
  cssParser.js            — CSS tokenizer with SCSS nesting support
  specificity.js          — standard (id, class, type) specificity calculator
  cssomBuilder.js         — in-memory cascade model builder (CSS, SCSS, CSS Modules, CSS-in-JS)
  selectorMatcher.js      — heuristic selector matching with confidence levels
  variableResolver.js     — CSS custom property resolution
  cssModulesAnalyzer.js   — CSS Modules local scope detection
  scssNestingExpander.js  — SCSS nesting pre-processor
  cssInJsExtractor.js     — styled-components / Emotion static extractor (template + object syntax)
  astComponentGraph.js    — AST component graph for graph-aware matching
  resolveStyles.js        — resolve_styles tool
  traceProperty.js        — trace_property tool
  impactPreview.js        — impact_preview tool
  styleManifest.js        — style_manifest project-wide knowledge builder
  cdpBridge.js            — Chrome DevTools Protocol WebSocket client
  liveResolve.js          — live_resolve tool
  server.js               — MCP server (stdio JSON-RPC) + CLI entry point

Zero external dependencies. Requires Node.js 21+.

Roadmap

• v0.2 ✅ — CSS custom property resolution

• v0.3 ✅ — SCSS nesting, CSS Modules scope awareness, AST component graph

• v1.0 ✅ — Chrome DevTools Protocol live resolution

• v1.1 ✅ — impact_preview: blast radius prediction before making a change

• v1.2 ✅ — style_manifest: compressed project-wide CSS knowledge for agent context

• v1.3 ✅ — CSS-in-JS: static extraction for styled-components and Emotion (template and object syntax)

Next (not yet scheduled)

Known gaps in CSS-in-JS support, in no particular order: merging styled(Base) styles into the child, resolving constants and theme objects imported from other files, and modeling keyframes and the Emotion css prop.