Canvas Design Decomposition

Canvas design decomposition

Mandatory triggers (load this skill first)

Load and follow this skill before proposing component structure for a component library, writing implementation plans, or implementing components—including when the user only asks for a plan or breakdown—whenever you are modeling how UI should split into Canvas components (a component library, section, or full page). The same applies when you are about to build, add, or scaffold components (see below). Treat any of the following as a trigger:

• Building or adding Canvas components: creating new folders under src/components/, authoring component.yml and the entry file (index.jsx/.tsx in React projects; the framework-appropriate file in headless projects), scaffolding a component from a ticket or spec, coding a section from a design, or implementing a named block (hero, footer, card, and so on). Decompose before writing schema or implementation code so names, slots, variants, and reuse stay aligned—unless the task is a trivial one-line tweak inside an existing, stable API.
• Designing or evolving a component library for Canvas—naming regions, deciding reuse, props/slots, and granularity—whether the stimulus is a file, a site, or a conversation.
• The message contains a Figma URL (figma.com/design, figma.com/make, or branch URLs) or explicit node-id / frame language tied to Figma.
• The source of truth is an existing website, screenshot, scraped page, or reference URL meant to drive layout or components (pair with nebula-scrape-url when a live URL needs capture).
• The source is text-only or generative: a written brief, markdown spec, or an AI- / prompt-generated design (layout description, wireframe in words, component list from a chat). Phase A still applies—classify intake and list unknowns even when pixels are absent.
• The user asks to implement, build, match, recreate, or plan implementation of a design, frame, screen, or page from any artifact or description.

Do not skip (common failure mode)

• Greenfield work is not exempt. Implementing a new page or Figma frame from scratch still requires this skill—you map the design to a coherent tree, props, and slots before locking implementation details.
• Draft files in the repo are not a shortcut. Existing pages/*.json, partial components under src/components/, or scraped assets may be helpful starting points, but they do not replace reading this skill and completing phases A–G for the current artifact. Reconcile draft code with the breakdown; do not assume prior work already did decomposition.
• Plans count. If the user asks only for an implementation plan, you still load this skill and summarize regions → components → placement before pixel work or tooling shortcuts.

Automated tool output (for example Figma MCP reference JSX, HTML export, or generated code) is input to this workflow—not a substitute for completing phases A–G.

Turn a design artifact into a stable component model: regions, tree, prop vs slot decisions, and granularity checks. A breakdown is incomplete without sketching props and slots for each node—Canvas authors interact with the tree through that API, so plan it with structure, not after implementation.

During planning, step past the single frame or ticket: ask where else each piece could appear and what would differ (copy, children, variant). Prefer reusable machineNames, slots for variable regions, and presets via variant over one-off names or props that hard-code one campaign’s content.

Do not implement pixels or write component.yml inside this workflow—finish the structure and prop/slot sketch first, then hand off.

Skill order

1. This skill — workflow, tree, and handoff.
2. canvas-component-composability — shared props/slots rules, repeatable content, and granularity checks.
3. canvas-component-metadata — exact component.yml schema.
4. canvas-component-definition — folder contract, mocks, naming authority.
5. implement-design — pixel-level fidelity when the source is Figma and after the tree is locked (requires Figma MCP when used). For non-Figma sources, implement from the locked tree and tokens without this step unless the user points back to a Figma file.

For repeatable lists/grids in Canvas, see canvas-component-composability/references/repeatable-content.md.

Inputs

Classify the source in Phase A. Typical categories:

Optional helpers:

• URL capture: nebula-scrape-url (not for Figma or docs).
• Figma fidelity pass (after decomposition): implement-design.

Workflow (mandatory)

Complete phases A → G in order. Each phase has an exit criterion. If Phase F fails, fix the tree and re-run Phase E for affected nodes only.

Phase A — Intake and framing

• Identify input type: design file (e.g. Figma), live site / scrape, screenshot, or text-only / prompt-generated spec.
• List unknowns: breakpoints, empty states, max copy length, media aspect ratios, hover/focus/active, accessibility expectations.
• Tag each unknown with risk: low / medium / high (edits likely to churn structure).

Exit: Input type stated; unknowns listed with risk (workflow continues even if some answers are missing).

Phase B — Region map

• Divide the design into regions (e.g. header, hero, content band, sidebar, footer, modal chrome).
• For each region: label, purpose (one line), class — chrome (shell), navigation, or content.

Exit: Ordered region list with purpose and class for each.

Phase C — Candidate component inventory

• Map regions to candidate machineName values (kebab-case folder names per canvas-component-definition).
• Prefer reusable base names; variants via props/composition, not extra component names, unless truly one-off.
• Mark reuse count when the same pattern appears two or more times.
• Generalize: For each candidate, note other plausible contexts (other pages, shorter copy, different children). If it only makes sense for this one screen, rename or decompose until it is reusably scoped.

Exit: Table: candidate machineName, responsibility, reuse count, parent region.

Phase D — Component tree

• Build parent/child relationships: layout shells vs content leaves.
• Layout ownership: multi-column grids, page-level stacks, and section wrappers belong in layout-oriented components; avoid baking unrelated grids into content components unless the layout is invariant for every instance.
• Express the tree as a nested outline or Mermaid diagram (Mermaid node IDs: no spaces; use camelCase or underscores).

Exit: Tree covers every inventory row; layout vs content roles are explicit.

Phase E — Props vs slots (per node)

Required: Every decomposition includes this phase. Props and slots are not a late add-on—they define how editors use the tree. For each tree node, sketch:

• Props: configuration and simple values editors should set directly (variants, booleans, short strings, URLs, enums). Note intent and broad type class (string, boolean, enum, image/reference)—not final YAML. Follow canvas-component-composability for the actual props-vs-slots rubric, variants-vs-granular guidance, and prop ordering. This phase records the decision; it does not redefine that rubric.
• Slots: areas where authors compose child components or arbitrary blocks. Name the slot, describe allowed content, and note empty behavior (collapse, placeholder, min height).
• Implementation style: record variants (default) or granular props with a one-line rationale in the handoff. For the Phase E write-up convention, see references/props-vs-slots-rubric.md.

Exit: Every node has a prop/slot sketch, implementation style is stated, and repeatable rich children are not modeled as object arrays in props.

Phase F — Granularity audit

Run the shared granularity checklist in canvas-component-composability. In this phase, audit the candidate tree against that shared rule set and record the result; do not create a second split/merge rubric here. For the Phase F audit note, see references/granularity.md.

• Mark each node pass/fail with a short rationale.
• If any node fails, merge, split, or extract, then repeat Phase E for changed nodes only.
• Document intentional exceptions explicitly.

Exit: All nodes pass or failures are documented with explicit rationale.

Phase G — Handoff

Deliver one Markdown artifact using the template below. Point next steps to:

• Schema: canvas-component-metadata
• Composition edge cases: canvas-component-composability
• Contract and mocks: canvas-component-definition
• Visual fidelity from Figma: implement-design (when applicable)

Exit: Filled template ready to paste into an issue or MR.

Out of scope here: page JSON (canvas-page-definition), validation runs (nebula-component-validation).

Output template

Copy and fill:

## Summary

- **Design source:** (e.g. Figma URL | live URL | screenshots | prompt/spec
  text)
- **Scope:** (single component | section | full page)
- **Version / date:**

## Assumptions and open questions

- ...

## Region map

| Region | Purpose | Class |
| ------ | ------- | ----- |
| ...    | ...     | ...   |

## Component inventory

| machineName (candidate) | Responsibility | Reuse | Parent region | Notes |
| ----------------------- | -------------- | ----- | ------------- | ----- |
| ...                     | ...            | ...   | ...           | ...   |

## Component tree

(Nested list or Mermaid)

## API sketch (per component)

### `machine-name`

**Implementation style:** variants (default) | granular props — one-line
rationale

**Props** (table rows in editor order: **variant first** when there is a single
primary variation enum; **content first** otherwise—then configuration)

| Name (camelCase intent) | Purpose | Required? | Kind (string / bool / enum / …) |
| ----------------------- | ------- | --------- | ------------------------------- |
| ...                     | ...     | ...       | ...                             |

**Slots**

| Slot key | Purpose | Empty behavior |
| -------- | ------- | -------------- |
| ...      | ...     | ...            |

## Granularity audit

| Component / node | Pass/Fail | Notes / fix |
| ---------------- | --------- | ----------- |
| ...              | ...       | ...         |

## Next steps

- [ ] `canvas-component-composability` — edge cases for props/slots,
      repeatability, or granularity
- [ ] `canvas-component-metadata` — draft `component.yml`
- [ ] `canvas-component-definition` — folder, entry file, mocks
- [ ] `implement-design` — Figma fidelity pass (only when matching a Figma file)

Further reading

• canvas-component-composability
• references/granularity.md
• references/props-vs-slots-rubric.md
• references/worked-example.md

Anti-duplication

• Do not restate full component.yml grammar—use canvas-component-metadata.
• Do not restate the reusable props/slots or granularity rulebooks here—link canvas-component-composability.