An open-source MCP server that gives your AI coding agent a visual canvas. Sketch the UI, review it in a browser, agree on the design — before any framework code gets written.

Contents: Viewer · Installation · Tools · Usage Example · Workflow · Development

Above: the framesmith viewer. Workspaces and projects in the sidebar, canvases as live thumbnails on the right. AI agents create canvases via MCP tools; you browse them like Figma files.

MCP Client → stdio → framesmith server
                        ↓
              Scene Graph (in-memory JSON tree)
                        ↓
              HTML/CSS Renderer (inline styles)
                        ↓
              Puppeteer (headless Chromium → PNG)

Run npx -p framesmith framesmith-viewer to start the standalone browser viewer (default port 3001). Open any canvas to review it at multiple breakpoints, compare them side-by-side, inspect the underlying JSON, or archive / delete.

Above: a single canvas in the detail view. The toolbar across the top exposes the breakpoint preview modes, Compare for side-by-side rendering, Fit for max-width, JSON for the raw scene graph, and lifecycle actions.

The viewer is purely read-only — every canvas is authored through MCP tool calls from your AI assistant. Files persist to ~/.framesmith/canvases/ so the viewer keeps showing them across sessions.

No clone or build needed — register framesmith with your MCP client via npx (requires Node 20+).

claude mcp add framesmith -- npx -y framesmith

Add to ~/.codex/config.toml:

[mcp_servers.framesmith]
command = "npx"
args = ["-y", "framesmith"]

Add to ~/.cursor/mcp.json (or per-project .cursor/mcp.json):

{
  "mcpServers": {
    "framesmith": {
      "command": "npx",
      "args": ["-y", "framesmith"]
    }
  }
}

Add to ~/.codeium/windsurf/mcp_config.json:

{
  "mcpServers": {
    "framesmith": {
      "command": "npx",
      "args": ["-y", "framesmith"]
    }
  }
}

Add to .vscode/mcp.json (project-scoped) or your global MCP settings:

{
  "servers": {
    "framesmith": {
      "command": "npx",
      "args": ["-y", "framesmith"]
    }
  }
}

framesmith speaks standard stdio MCP. Point your client at npx -y framesmith using whatever config shape your client expects.

Optional: set FRAMESMITH_VIEWER_URL=http://localhost:3001 in the MCP server env to pin it to a long-lived standalone viewer process — see Running the viewer.

git clone https://github.com/vicmaster/framesmith.git
cd framesmith
npm install
npm run build
# then point your client at: node /path/to/framesmith/dist/index.js

One-call onboarding — the recommended first call each session, and safe to run repeatedly (idempotent). Binds the current repo if it isn't already (canvases become checked-in JSON under .framesmith/), ensures the convention projects exist, and returns the live state you need to start working.

Returns the bound workspace + project IDs (binding re-keys IDs to repo-* — use the ones init returns), the on-disk layout, the workspace-layer token count, a workflow cheatsheet, the current gotchas, the framesmith://guidelines URI, and the viewer URL. It does not seed design tokens — set those at the workspace layer with workspace_set_design_system. The default Foundations project is just a canvas that visualizes the workspace tokens (which is where the design system actually lives).

Create a new canvas. If projectId is omitted, it lands in the built-in Untitled project of the Personal workspace.

The response also carries a diversification signal for the target project: the recently-built structures (newest first) and a hint to differ on at least one taxonomy axis, so successive canvases don't converge on the same layout. It's advisory — never blocking.

List canvases. Excludes archived canvases by default.

Returns [{ id, name, createdAt, lastModified, projectId, archived }].

Canvas lifecycle. canvas_move reassigns a canvas to a different project. canvas_archive sets a soft-delete flag (canvas stays on disk, hidden from default canvas_list); canvas_unarchive clears it. canvas_delete removes the canvas and its file permanently — irreversible.

Get the URL of the live viewer plus per-canvas URLs. Share these with the user so they can open the design in their browser. No params.

{
  "url": "http://localhost:3001",
  "gallery": "http://localhost:3001",
  "canvases": [
    { "name": "Login", "viewer": "http://localhost:3001/canvas/abc123" }
  ]
}

canvas_create already returns the per-canvas viewer URL in its response; reach for viewer_url when you want the gallery URL or to enumerate every existing canvas's URL in one call.

Top-level container CRUD. The built-in Personal workspace cannot be deleted, and workspace_delete refuses if the workspace still contains projects (move or delete them first).

Mid-level container CRUD inside a workspace. The built-in Untitled project cannot be deleted. project_delete refuses if the project still contains any canvases (archived ones still count — move or delete them first).

Bind a workspace to the current project directory so its canvases live in the repo as open JSON — a .framesmith/ directory checked in alongside the code, instead of the global ~/.framesmith store. Run it once per repo.

It creates .framesmith/workspace.json (the binding plus the design system, so a fresh clone resolves tokens identically) and one subdirectory per project holding one slug-named file per canvas:

.framesmith/
  workspace.json     # workspace + projects[] + design system
  design-system/
    design-tokens.json
  ui/
    bloom-landing.json
    login-form.json

It migrates the workspace's projects + canvases in and makes the repo the source of truth for the rest of the session. A canvas is either repo-bound or global, never both. Afterwards the server auto-detects .framesmith/ on startup (walking up from its working directory). Commit .framesmith/ so designs travel with the code and diff cleanly in review.

The bind also records the repo in ~/.framesmith/registry.json, so the standalone viewer shows bound repos alongside your global workspaces in one gallery (it rebuilds that read-only mirror on launch and whenever the registry changes).

Execute operations on the scene graph. Operations are line-separated strings:

# Insert a frame into the document root
header=I("document", { type: "frame", layout: "horizontal", fill: "#1a1a2e", padding: 24, gap: 16, width: 1440, height: 80 })

# Insert text into the header
I(header, { type: "text", content: "My App", fontSize: 24, fontWeight: 700, color: "#ffffff" })

# Update a node
U("nodeId", { fill: "#e94560" })

# Delete a node
D("nodeId")

# Copy a node to a new parent
copy=C("sourceId", "parentId", { fill: "#0f3460" })

# Move a node
M("nodeId", "newParentId", 0)

# Replace a node entirely
R("nodeId", { type: "text", content: "Replaced" })

Returns { ok, nodeIds, results }. nodeIds maps each bound variable to the node ID it created — e.g. { "header": "n_a1b2" } — so you can target those nodes in later calls (bindings only live within a single call). results lists each op's outcome in order.

Node types: frame, text, rectangle, ellipse, image, icon, path, component, instance, toggle, checkbox, radio, select

Properties: fill, gradient, stroke, strokeWidth, cornerRadius, width, height, layout ("horizontal" | "vertical"), gap, padding, alignItems, justifyContent, fontSize, fontFamily, fontWeight, color, content, textAlign, lineHeight, letterSpacing (px), textDecoration, textTransform, fontVariationSettings, src, objectFit, opacity, shadow, shadows, blur, backdropBlur, backdropFilter, overflow, wrap, position, x, y, icon, iconSize, iconColor, iconStyle, checked, disabled, value, d, viewBox, strokeLinecap, strokeLinejoin, animation, transition, componentId, overrides

Use textTransform: "uppercase" for uppercase labels (don't bake casing into content), letterSpacing for tracking, and fontVariationSettings (e.g. '"wght" 650') for variable-font axes.

Render canvas to PNG (returned as base64 image).

Read node data from the scene graph.

Get computed bounding boxes via browser rendering.

Read and write design tokens (colors, spacing, radius, typography). Use $tokenName in node properties to reference variables.

{
  "colors": { "primary": "#e94560", "bg": "#1a1a2e" },
  "spacing": { "sm": 8, "md": 16, "lg": 24 },
  "radius": { "sm": 4, "md": 8 }
}

Then use in nodes: { fill: "$primary", padding: "$md", cornerRadius: "$sm" }

Set tokens at the workspace level — every project + canvas under the workspace inherits them. Resolution order at render is canvas.variables (override) → project.designSystem → workspace.designSystem → built-in defaults, with the rightmost layer winning. Per-category merge: setting only colors doesn't reset spacing.

workspace_set_design_system({
  workspaceId: "...",
  variables: {
    colors: { primary: "#f59e0b", bg: "#0a0a0a" },
    spacing: { sm: 8, md: 16, lg: 24 }
  }
})

workspace_apply_preset({ workspaceId, preset }) is a shortcut that copies a named preset ("dark", "light", "material", "minimal") into the workspace.

Same shape, but at the project layer between workspace and canvas. Use for sub-brand overrides (e.g., a Marketing project that overrides one color while inheriting everything else from the workspace).

Fonts load by name automatically — naming a fontFamily in a typography token (or on a node) resolves it from Google Fonts at token-write time, with a render-time backstop catching anything else. Binaries are cached under ~/.framesmith/fonts/, so renders are offline and deterministic after the first resolve; typography.body.fontFamily becomes the document default. An unresolvable family renders in the fallback stack and adds a Font warnings item to the screenshot/export result.

set_fonts covers explicit registration. Three forms, combinable:

{
  "families": ["Inter", "JetBrains Mono"],
  "fonts": [
    { "family": "Inter", "url": "https://fonts.googleapis.com/css2?family=Inter:wght@400;700" },
    { "family": "Brand Face", "url": "https://example.com/brand.woff2", "weight": 400 }
  ]
}

• families — resolve by name from Google Fonts and merge into the existing declarations.
• fonts with a Google Fonts CSS URL (fonts.googleapis.com/css2?...) — faces are extracted from the stylesheet automatically.
• fonts with a direct binary URL (.woff2 / .woff / .ttf / .otf or a data: URI) — for non-Google sources.

fonts replaces declarations wholesale (pass [] to clear); families merges. The renderer emits @font-face blocks plus <link rel="preconnect"> per remote origin, with font-display: swap.

Export a canvas or specific nodes to files on disk.

List available style guide presets. No params. Returns preset names and descriptions.

Apply a style guide preset to a canvas. Merges preset design tokens into the canvas variables, and copies in any reusable components (button, card, badge) the preset defines so they can be instanced. The preset is also recorded in the canvas provenance + per-project build log.

List available layout structures — named scaffolds you stamp onto a canvas and then populate. Returns each structure's name, kind, description, and (for pages) taxonomy axes. Distinct from presets: structures define layout skeleton, presets define color/token theme — they compose.

Two kinds:

• page — whole-page scaffolds stamped once at the canvas root: marquee-hero, bento-grid, stat-led, editorial-longform, split-workbench, catalogue. Each is tagged on four independent axes — heroTreatment, density, rhythm, alignment — so you can deliberately vary page shape instead of defaulting to the same layout.
• component — reusable fragments stamped under any node via targetId, repeatably: data-table (header + 3 rows with avatar/name/email, role chip, status toggle, actions), form-field, toolbar, stat-card, toggle-row. A high-fidelity table costs one stamp instead of ~80 hand-placed nodes.

Stamp a layout structure onto a canvas and return the placeholder node IDs to populate. Seeds neutral default colors so the scaffold renders even before a preset is applied. Populate the placeholders with batch_design U ops, then screenshot to verify.

• Page scaffolds insert at the canvas root (refusing on a non-empty canvas unless replace), record provenance (metadata.provenance), and append to the per-project build log that feeds the diversification signal.
• Component scaffolds insert under targetId (default root), repeatably — every stamp re-keys its node IDs (form-field-1-…, form-field-2-…) and returns an idMap (template ID → live ID) for follow-up ops. Component stamps don't touch provenance or the build log: they don't shape the page.

Import an HTML snippet (+ optional CSS) as an editable canvas — the reverse of export. The markup renders headlessly and a computed-style DOM walk maps it to the scene graph:

Lossy by design. Every import returns a report — counts, warnings (dropped background images, grid containers, truncations), unmatched icons/fonts — and that report is the contract; the goal is an editable, honest starting point, not a pixel-perfect clone. Single-child wrapper divs collapse, same-style text runs merge, invisible nodes drop (all tunable via flatten).

Token re-mapping makes the import a token-driven design instead of a pile of hex:

• Tailwind intent first — class names carry intent a computed value can't: bg-surface → fill: "$surface", gap-4 → 16, rounded-xl → 12, text-sm font-semibold uppercase → typography props. Custom utilities resolve via tailwind.theme; palette classes (bg-red-500) map to the bundled v4 palette as hex literals (generated from the official oklch values by Chrome itself — see scripts/generate-tailwind-palette.ts), so a bare snippet styles without compiled CSS; arbitrary values and unknowns fall through to computed styles. Geometry intent and palette literals only fill gaps the CSS didn't set; token-ref colors override computed literals.
• Nearest-color snapping second — remaining literal colors snap to the matched design system within tolerance (exact matches always; near-ties between two tokens are reported and left literal, never guessed). Spacing/radius/fontSize values that equal a scale token are reported under report.scaleMatches.
• Fonts seen in computed styles feed the font-by-name resolver, so the imported canvas renders in the same faces.

Returns { canvasId, rootId, report } — report.snapped / literals / scaleMatches / warnings are the contract.

Import a live page as an editable, token-mapped canvas — point at a running app and the screen becomes the design-of-record without redrawing. Same engine and token re-mapping as canvas_import_html, plus live-page controls:

Relative image URLs resolve against the page; fonts seen in computed styles load through the font-by-name resolver so the canvas renders in the same faces. The source URL (never auth) is recorded in metadata.provenance.importedFrom.

Drift detection — the design-of-record as a living contract. Re-imports a live page ephemerally (no canvas created, nothing mutated) and pixel-diffs it against an existing canvas at the same viewport:

Returns the diff image (changed regions in red), changePercent, changedPixels/totalPixels, and the import report. Both sides render at scale 1, so the percentage is comparable run-to-run — an unchanged page diffs at ~0%.

CI pattern (a pattern, not a shipped feature): after deploy, call canvas_sync_from_url for each route ↔ canvas pair and fail the job when changePercent exceeds your threshold — design ↔ code divergence becomes a build failure instead of a surprise.

Import a DESIGN.md file as a design system preset. Parses the Google Stitch format and extracts colors, typography, spacing, and border radius. It also extracts reusable component skeletons (button, card, badge) from the "Component Styling" section — apply_preset then makes them available as instanceable components on the canvas. After importing, use apply_preset to apply it to any canvas.

Compatible with the 55+ design systems in awesome-design-md (Stripe, Notion, Figma, Vercel, Linear, etc.).

Accepted token formats. Each category is read from a loosely-matched heading section (Colors / Color Palette, Spacing, Border Radius / Radius, Typography). Within a section, tokens may be written as a list item (- name: value), a 2-column table row (| name | value |), or a name: value / **name** (\value`) line — where value is a color (#hex, rgba(...)) for colors, Npxfor spacing/radius, andNpx(optionally/ weight, e.g. 16px / 600) for typography. Named spacing tokens (md: 12px) are honored verbatim; a scale is synthesized **only** when no named tokens are given and a Base unit: Npxis stated — otherwise nothing is fabricated. Radius accepts the scale namessm/md/lg/xl/full/pill`.

Render a canvas at multiple viewport sizes. Defaults to mobile (390x844), tablet (768x1024), and desktop (1440x900).

The renderer emits clamp() for paddings ≥ 32px and font sizes ≥ 24px, so headlines and large spacing shrink proportionally at narrower viewports (assuming a 1440px design width). Smaller values stay static.

Compare two canvases visually. Returns a diff image with changed regions highlighted in red.

Auto-score a design against quality heuristics. Returns an overall score (0–100), per-category scores, and per-node actionable issues. Designed for generator-evaluator loops: build with batch_design, score with canvas_evaluate, fix the issues targeting the returned nodeIds, repeat.

Categories and what they check

Return shape

{
  "overallScore": 87,
  "categories": [{ "name": "spacing", "score": 90, "issueCount": 1, "weight": 20 }],
  "issues": [
    {
      "category": "color",
      "severity": "error",
      "nodeId": "abc123",
      "message": "Text \"Sign In\" has contrast ratio 2.8:1 against #1a1a2e. WCAG AA requires 4.5:1.",
      "suggestion": "Increase contrast by darkening/lightening the text or background."
    }
  ],
  "summary": "Overall quality: Good (87/100). Strongest: spacing (90/100). Weakest: color (75/100)...",
  "stats": { "totalNodes": 14, "textNodes": 5, "frameNodes": 8, "maxDepth": 4, "tokenUsagePercent": 61, "componentReusePercent": 0 },
  "mode": "fast"
}

With mode: "llm" (Phase 13), the vision model scores a fixed rubric — five axes, each 1–5 with a rationale — instead of one opaque number. The verdict is stamped on the canvas (metadata.critique) and the per-project build log so quality is auditable over time. Add floor (1–5, default 3, or FRAMESMITH_CRITIQUE_FLOOR) to set the per-axis threshold that trips needsRevision.

{
  "llmCritique": {
    "provider": "anthropic",
    "model": "claude-sonnet-4-6",
    "rubric": {
      "hierarchy":   { "score": 4, "rationale": "clear primary metric, secondary stats recede" },
      "execution":   { "score": 4, "rationale": "tidy alignment and consistent spacing" },
      "specificity": { "score": 3, "rationale": "reads a touch generic for a dashboard" },
      "restraint":   { "score": 5, "rationale": "flat surfaces, no gratuitous effects" },
      "variety":     { "score": 2, "rationale": "the default centered three-card row" }
    },
    "score": 72,
    "summary": "Clean, restrained dashboard; layout is conventional.",
    "suggestions": ["break the symmetric three-card row with an asymmetric feature tile"],
    "needsRevision": true,
    "failingAxes": [{ "axis": "variety", "score": 2, "rationale": "the default centered three-card row" }]
  }
}

Axes: hierarchy (focal order), execution (craft — alignment/spacing/contrast), specificity (designed-for-purpose vs generic), restraint (no overdone effects — the LLM sibling of the cliche category), variety (avoids same-shape sameness). score is derived: round(mean(axisScores) / 5 * 100). To close the loop automatically, see canvas_revise.

Provider selection: FRAMESMITH_LLM_PROVIDER env var (anthropic | openai), else falls back to whichever of ANTHROPIC_API_KEY / OPENAI_API_KEY is set. Default models: claude-sonnet-4-6 / gpt-4.1 (override via FRAMESMITH_LLM_ANTHROPIC_MODEL / FRAMESMITH_LLM_OPENAI_MODEL). Adding a third provider is one entry in the judges table in src/llm-judge.ts.

Example generator-evaluator loop

batch_design({ canvasId, operations: "..." })
const r = canvas_evaluate({ canvasId, mode: "fast" })
// r.issues[].nodeId points to exactly what to fix
batch_design({ canvasId, operations: `U("${r.issues[0].nodeId}", { color: "#ffffff" })` })
canvas_evaluate({ canvasId })  // re-score

Issues that have a mechanical fix come back with an extra fix: { op, rationale } field — see canvas_autofix below.

Runs canvas_evaluate in fast mode and returns just the subset of issues with a mechanically derived fix — no judgement calls. Each fix carries a ready-to-paste batch_design Update op string. Closes the generator-evaluator loop without a second AI hop.

What gets auto-fixed

• Spacing — off-scale gap or scalar padding snaps to the nearest scale value. Array padding is skipped (ambiguous which index).
• Consistency — frames with multiple children but no layout get layout: "vertical".
• Color — recoverable WCAG contrast failures get color: "#000000" or "#FFFFFF", whichever wins against the resolved background. Failures so bad that neither black nor white meets the threshold are not auto-fixed (the background also needs to change).
• Cliché — a known-default purple/indigo accent (#6366f1 and friends) written literally on a node swaps to a neutral accent; a dedicated fake-chrome strip (a row that is just traffic-light dots) gets a D(...) delete. Taste-dependent tells (gradient/glow overuse, the hanging header, fabricated copy) are reported by canvas_evaluate with a suggestion but carry no auto-fix op.

Return shape

{
  "totalIssues": 18,
  "fixableCount": 5,
  "fixes": [
    {
      "nodeId": "abc123",
      "category": "color",
      "op": "U(\"abc123\", { color: \"#000000\" })",
      "rationale": "Switch text color to #000000 for WCAG AA contrast against #F8FAFC",
      "message": "Text \"Sign In\" has contrast ratio 2.8:1 against #F8FAFC. WCAG AA requires 4.5:1."
    }
  ]
}

Apply the ops by joining them with newlines and passing to batch_design, then re-evaluate.

Closes the critique loop (Phase 13). Judges the canvas against the rubric; if any axis is below the floor, asks an LLM for targeted batch_design ops that raise the failing axes, applies them, re-renders, and re-judges — up to maxIterations passes. Mutates the canvas. Opt-in and bounded; it never runs implicitly.

Loop & safety

• Each pass: render → judge → if needsRevision, revise the failing axes → apply (validated through batch_design) → re-render → re-judge.
• Stops when the canvas passes (passed), at the cap (max-iterations), when a pass doesn't improve the overall (no-improvement — the regressing edit is reverted), when the reviser returns nothing (no-ops), or when an op fails to apply (apply-error — the partial edit is reverted).
• Every accepted pass re-stamps metadata.critique + the build log. Costs ≥2 paid API calls per pass (one judge + one revise) and renders between passes (Chrome required).

Return shape

{
  "iterations": [
    { "pass": 1, "overallBefore": 72, "failingAxes": ["variety"],
      "opsApplied": "U(\"cards\", { ... })", "overallAfter": 84 }
  ],
  "finalVerdict": { "rubric": { "...": {} }, "score": 84, "needsRevision": false, "failingAxes": [] },
  "stoppedReason": "passed"
}

• framesmith://guidelines — markdown authoring guide: width strategies (fixed / percentage / fluid+cap / floor / fit-content), responsive hint semantics (stack / wrap / fixed), common patterns (pricing tiers, two-column hero, tag list, toolbar), and anti-patterns. Source: docs/GUIDELINES.md.

npm run bench runs canvas_evaluate over a fixed corpus of canvases (a high-quality dashboard hero, a minimal well-formed canvas, an intentional-contrast-failure canvas) and diffs the result against benchmark/baselines.json. Catches drift in scoring across renderer / evaluator changes — exit code is nonzero on any score, issue-count, or issue-message change. Re-baseline with npx tsx benchmark/run.ts --update after intentional evaluator rewrites.

Nodes support linear and radial gradients via the gradient property:

# Linear gradient (angle in degrees)
I("parent", { type: "frame", width: 400, height: 200, gradient: { type: "linear", angle: 135, stops: [{color: "#667eea", position: 0}, {color: "#764ba2", position: 100}] } })

# Radial gradient
I("parent", { type: "frame", width: 200, height: 200, gradient: { type: "radial", stops: [{color: "#fff", position: 0}, {color: "#000", position: 100}] } })

When gradient is set, it takes precedence over fill. Both can coexist (fill as fallback).

Structured shadows, blur filters, and backdrop blur:

# Structured shadow (supports multiple shadows)
I("parent", { type: "frame", fill: "#fff", shadows: [{x: 0, y: 4, blur: 12, spread: 0, color: "rgba(0,0,0,0.15)"}] })

# Blur filter
I("parent", { type: "frame", fill: "#3b82f6", blur: 4 })

# Backdrop blur (single-function shorthand for `blur`)
I("parent", { type: "frame", fill: "rgba(255,255,255,0.5)", backdropBlur: 8 })

# Glassmorphism (composable backdrop-filter: blur + saturate + brightness + contrast)
I("parent", {
  type: "frame",
  fill: "rgba(255, 255, 255, 0.4)",
  backdropFilter: { blur: 12, saturate: 180, brightness: 110 }
})

The structured backdropFilter form takes precedence over backdropBlur when both are set. The renderer also emits the -webkit-backdrop-filter prefix so glass effects render in Safari/iOS without extra work.

The legacy shadow string property still works for simple cases.

Two bundled sets are available via the icon node type, rendering as inline SVGs with configurable size and color:

Lucide (1,900+, stroke style) — unprefixed names, browse here:

I("parent", { type: "icon", icon: "search", iconSize: 24, iconColor: "#888" })
I("parent", { type: "icon", icon: "heart", iconSize: 32, iconColor: "#ef4444" })

Material Symbols (3,800+, fill style) — material: prefix, browse here:

I("parent", { type: "icon", icon: "material:check", iconSize: 24, iconColor: "#b71421" })
I("parent", { type: "icon", icon: "material:settings", iconStyle: "rounded" })
I("parent", { type: "icon", icon: "material:star-fill" })   # "-fill" suffix = filled variant

iconStyle picks the Material variant ("outlined" default, "rounded", "sharp"); it's ignored for Lucide.

toggle, checkbox, radio, and select are first-class node types — static renders with a checked / value / disabled state, so app UI doesn't have to be faked from frames and ellipses:

I("parent", { type: "toggle", checked: true })
I("parent", { type: "checkbox", checked: true })
I("parent", { type: "radio" })
I("parent", { type: "select", value: "Administrator", width: 220 })
I("parent", { type: "select" })                      # renders a muted "Select…" placeholder
I("parent", { type: "toggle", checked: true, disabled: true })   # 50% opacity

Colors default from the design system — $accent (falling back to $primary) for active states, $border for outlines, $bg-surface / $text-primary for the select — with neutral fallbacks on unthemed canvases. Explicit fill / stroke / color override. Defaults: toggle 44×24, checkbox/radio 18×18, select fit-content (give it a width for form layouts).

For custom shapes and brand marks beyond the Lucide library, use the path node type with a raw SVG d attribute:

I("parent", { type: "path", width: 24, height: 24,
  d: "M 12 2 L 22 22 L 2 22 Z", fill: "#f59e0b" })

# With stroke + viewBox (defaults to `0 0 width height`)
I("parent", { type: "path", width: 48, height: 48, viewBox: "0 0 24 24",
  d: "M 12 2 L 22 22 L 2 22 Z",
  fill: "none", stroke: "#000", strokeWidth: 2,
  strokeLinecap: "round", strokeLinejoin: "round" })

fill/stroke/strokeWidth apply to the path itself (not the wrapper). d and viewBox are validated for safe characters — anything that could break out of the attribute is rejected.

Reference a built-in keyframe to make a node animate in on page load. The renderer auto-emits the @keyframes block only when referenced.

I("hero", { type: "frame", animation: { name: "fadeIn", duration: 400 } })
I("title", { type: "text", animation: { name: "slideUp", duration: 300, delay: 100 } })

Built-in keyframe names: fadeIn, slideUp, slideDown, scaleIn. All end at the natural resting state with animation-fill-mode: both, so the start state applies pre-animation and the end state sticks after.

animation: { name, duration?: 300ms, delay?: 0ms, easing?: "ease-out", iteration?: 1 | "infinite" }. Easing is whitelisted: ease, ease-in, ease-out, ease-in-out, linear (anything else falls back to ease-out).

transition: { property?: "all", duration, easing?: "ease", delay?: 0ms }. Transitions only fire on state change, so they're inert until interactive states exist in the renderer — included today so a future hover/focus PR has a place to land.

Define reusable components and create instances with overrides:

# Define a component (a frame subtree that gets registered)
card=I("document", { type: "component", name: "Card", width: 300, fill: "#1a1a1a", cornerRadius: 12, layout: "vertical", padding: 16, gap: 8 })
I(card, { type: "text", name: "title", content: "Default Title", fontSize: 20, color: "#fff" })
I(card, { type: "text", name: "subtitle", content: "Default subtitle", fontSize: 14, color: "#888" })

# Create instances with overrides (matched by child name)
I("document", { type: "instance", componentId: card, overrides: { title: { content: "My Card" }, subtitle: { content: "Custom text" } } })

Here's a complete session building a login card:

1. Create a canvas and set design tokens

canvas_create({ name: "Login" })
→ {
    "canvasId": "abc123",
    "rootId": "xyz789",
    "name": "Login",
    "projectId": "default-project",
    "viewerUrl": "http://localhost:3001/canvas/abc123",
    "galleryUrl": "http://localhost:3001"
  }

set_variables({
  canvasId: "abc123",
  variables: {
    colors: { bg: "#0a0a0a", surface: "#1a1a2e", accent: "#e94560", text: "#ffffff" },
    spacing: { sm: 8, md: 16, lg: 24, xl: 32 },
    radius: { md: 8, lg: 16 }
  }
})

2. Build the layout with batch_design

batch_design({
  canvasId: "abc123",
  operations: `
    page=I("document", { type: "frame", width: 1440, height: 900, fill: "$bg", layout: "vertical", alignItems: "center", justifyContent: "center" })
    card=I(page, { type: "frame", width: 400, fill: "$surface", cornerRadius: "$lg", padding: [32, 32, 32, 32], layout: "vertical", gap: 24 })
    I(card, { type: "text", content: "Sign In", fontSize: 28, fontWeight: 700, color: "$text" })
    I(card, { type: "frame", width: "100%", height: 44, fill: "#ffffff10", cornerRadius: "$md", padding: [0, 16, 0, 16], layout: "horizontal", alignItems: "center" })
    I(card, { type: "frame", width: "100%", height: 44, fill: "#ffffff10", cornerRadius: "$md", padding: [0, 16, 0, 16], layout: "horizontal", alignItems: "center" })
    btn=I(card, { type: "frame", width: "100%", height: 44, fill: "$accent", cornerRadius: "$md", layout: "horizontal", alignItems: "center", justifyContent: "center" })
    I(btn, { type: "text", content: "Continue", fontSize: 16, fontWeight: 600, color: "$text" })
  `
})

3. Take a screenshot to see the result

screenshot({ canvasId: "abc123" })
→ returns base64 PNG image

4. Iterate — update the button color and verify

batch_design({
  canvasId: "abc123",
  operations: `U("btn-id", { fill: "#3b82f6" })`
})

screenshot({ canvasId: "abc123" })

The viewer runs in one of two modes — embedded (auto-starts inside the MCP server process) or standalone (long-lived in its own terminal). Standalone is recommended; the embedded mode stops the moment your MCP session ends, so any viewer URL you shared becomes unreachable.

# In a separate terminal tab — stays alive independently of any MCP session
npx -p framesmith framesmith-viewer

# Or on a specific port
npx -p framesmith framesmith-viewer 3004

Working from a clone instead of npm? Run npm run viewer (or npm run viewer -- 3004) from the repo root — same standalone viewer, run from source.

The standalone viewer:

• Persists across sessions — URLs keep working after Claude / Cursor / Windsurf finishes
• Shared across projects — multiple MCP sessions (from different projects) all use the same viewer
• Auto-detects new canvases — watches ~/.framesmith/canvases/ for changes and picks them up immediately
• Auto-detected by MCP — when the MCP server starts, it probes for a running standalone viewer and uses it instead of starting its own

• Gallery (/) — browse all canvases as clickable cards with live thumbnails
• Project (/project/:id) — same gallery but scoped to one project
• Archive (/archive) — soft-deleted canvases with restore / permadelete actions
• Canvas detail (/canvas/:id) — full rendered design with responsive viewport buttons (Mobile / Tablet / Desktop), Compare mode, Fit toggle, and JSON inspector
• Raw HTML (/canvas/:id/html) — the rendered HTML for embedding or inspection
• JSON API (/api/canvases, /api/canvas/:id/meta) — programmatic access
• Live auto-refresh — the viewer polls for changes every 2 seconds, so the browser updates automatically as your agent runs batch_design

All canvases persist to ~/.framesmith/canvases/ as JSON files and survive process restarts. Set FRAMESMITH_VIEWER_URL in the MCP server env to point at a viewer running on a non-default port.

1. Start the standalone viewer in a terminal tab: npx -p framesmith framesmith-viewer
2. canvas_create → get canvas ID
3. Open the viewer URL in your browser for live preview
4. apply_preset or set_variables → set up design tokens
5. batch_design → build the UI with frames, text, icons, components, gradients
6. Watch the viewer auto-refresh as you design
7. screenshot_responsive → preview at mobile/tablet/desktop sizes
8. canvas_diff → compare before/after changes visually
9. export → save final designs to PNG/PDF files

git clone https://github.com/vicmaster/framesmith.git
cd framesmith
npm install
npm run build

• ESM only ("type": "module"). Imports in TypeScript source use .js extensions even when the source file is .ts.
• Don't edit dist/ — it's regenerated by tsc.
• New MCP tool? Register it in src/index.ts, document it in the Tools section above, and update VISION.md's phase checklist.

MIT — see LICENSE.

Copyright (c) 2026 Victor Velazquez.