excalidraw

name	excalidraw
description	Use when user requests diagrams, flowcharts, architecture charts, or visualizations. Also use proactively when explaining systems with 3+ components, complex data flows, or relationships that benefit from visual representation. Generates .excalidraw files and exports to PNG/SVG via Kroki API or locally using excalidraw-brute-export-cli.
homepage	https://github.com/Agents365-ai/excalidraw-skill
metadata	{"openclaw":{"requires":{"bins":["curl"]},"emoji":"🎨"}}

Excalidraw Diagrams

Overview

Generate .excalidraw JSON files and export to PNG/SVG.

Two export options:

• Kroki API (curl) — zero install, SVG output only
• excalidraw-brute-export-cli — local Firefox-based, PNG + SVG

Supported formats: PNG (local CLI only), SVG (both options). PDF is NOT supported.

When to Use

Explicit triggers: user says "画图", "diagram", "visualize", "flowchart", "draw", "架构图", "流程图"

Proactive triggers:

• Explaining a system with 3+ interacting components
• Describing a multi-step process or decision tree
• Comparing architectures or approaches side by side

Skip when: a simple list or table suffices, or user is in a quick Q&A flow

Prerequisites

Option A: Kroki API (recommended — zero install, SVG only)

# Just needs curl (pre-installed on macOS/Linux/Windows Git Bash)
curl --version

No additional setup. SVG rendered via https://kroki.io.

Option B: Local CLI (required for PNG)

The CLI uses Firefox (not Chromium). Check and install:

npm install -g excalidraw-brute-export-cli
npx playwright install firefox

macOS patch (one-time, required):

CLI_MAIN=$(npm root -g)/excalidraw-brute-export-cli/src/main.js
sed -i '' 's/keyboard.press("Control+O")/keyboard.press("Meta+O")/' "$CLI_MAIN"
sed -i '' 's/keyboard.press("Control+Shift+E")/keyboard.press("Meta+Shift+E")/' "$CLI_MAIN"

Windows/Linux: No patch needed.

Workflow

0. Update check (notify, don't pull) — first use per conversation. Throttle to once per 24 h via <this-skill-dir>/.last_update; never mutate the skill directory without explicit user consent.

   • If .last_update exists and is <24 h old, skip this step entirely.

   • Otherwise, fetch the latest tag from upstream:

     git -C <this-skill-dir> ls-remote --tags origin 'v*' 2>/dev/null \
       | awk '{print $2}' | sed 's|refs/tags/||' | sort -V | tail -1
     

   • Compare with this skill's metadata.version from the frontmatter. If the upstream tag is strictly newer (semver), tell the user one line and ask:

     "A newer version of this skill is available: vX.Y.Z → vA.B.C. Want me to git pull?"

     If they say yes, run git -C <this-skill-dir> pull --ff-only. Refresh .last_update either way so the prompt doesn't repeat for 24 hours.

   • If upstream is the same or older, refresh .last_update silently and continue.

   • On any failure (offline, not a git checkout — e.g. ClawHub-installed copy, read-only path, no permission), swallow the error silently and continue with the user's task. Do not mention the failure.

1. Check deps — use Kroki (curl) for SVG; use local CLI for PNG

2. Plan — identify diagram type, pick a visual pattern, choose color palette

3. Generate — write .excalidraw JSON file (section-by-section for large diagrams)

4. Export — run Kroki or CLI command

5. Report — tell user the output file path

Design Principles

Default style

• roughness: 0 — clean, modern look for all technical diagrams (use 1 only when user requests hand-drawn/casual style)
• fontFamily: 2 (Helvetica) — professional look; use 1 (Virgil) only for casual/sketch style, 3 (Cascadia) for code snippets
• fillStyle: "solid" — default fill

Font size hierarchy

Level	Size	Use for
Title	28px	Diagram title
Header	24px	Section/group headers
Label	20px	Primary element labels
Description	16px	Secondary text, descriptions
Note	14px	Annotations, fine print

Color palette

Follow the 60-30-10 rule: 60% whitespace/neutral, 30% primary accent, 10% highlight.

Semantic fill colors (use with strokeColor one shade darker):

Category	Fill	Stroke	Use for
Primary / Input	#dbeafe	#1e40af	Entry points, APIs, user-facing
Success / Data	#dcfce7	#166534	Data stores, success states
Warning / Decision	#fef9c3	#854d0e	Decision points, conditions
Error / Critical	#fee2e2	#991b1b	Errors, alerts, critical paths
External / Storage	#f3e8ff	#6b21a8	External services, databases, AI/ML
Process / Default	#e0f2fe	#0369a1	Standard process steps
Trigger / Start	#fed7aa	#c2410c	Start nodes, triggers, events
Neutral / Container	#f1f5f9	#475569	Groups, swimlanes, backgrounds

Text colors:

Level	Color
Title	#1e293b
Label	#334155
Description	#64748b

Rule: Do not invent new colors. Pick from this palette.

Arrow semantics

Style	Meaning
Solid (strokeStyle: null)	Primary flow, main path
Dashed ("dashed")	Response, async, callback
Dotted ("dotted")	Optional, reference, weak dependency

Excalidraw JSON Structure

File skeleton

{
  "type": "excalidraw",
  "version": 2,
  "source": "claude-code",
  "elements": [],
  "appState": { "viewBackgroundColor": "#ffffff" }
}

Element types

type	use for
rectangle	boxes, components, modules
ellipse	start/end nodes, databases
diamond	decision points
arrow	directed connections
line	undirected connections
text	standalone labels

Element sizing

Calculate element width from label text to prevent truncation:

Latin text:  width = max(160, charCount * 9)
CJK text:   width = max(160, charCount * 18)
Mixed text:  estimate each character individually, sum up

Height: use 60 for single-line labels, add 24 per additional line.

Required properties (all elements)

{
  "id": "auth_service",
  "type": "rectangle",
  "x": 100, "y": 100,
  "width": 160, "height": 60,
  "angle": 0,
  "strokeColor": "#1e40af",
  "backgroundColor": "#dbeafe",
  "fillStyle": "solid",
  "strokeWidth": 2,
  "roughness": 0,
  "opacity": 100,
  "seed": 100001,
  "boundElements": [
    { "id": "arrow_to_db", "type": "arrow" },
    { "id": "label_auth", "type": "text" }
  ]
}

Use descriptive string IDs (e.g., "api_gateway", "arrow_gw_to_auth") instead of random strings.

Give each element a unique seed (integer). Namespace by section: 100xxx, 200xxx, 300xxx.

JSON field rules

• boundElements: use null when empty, never []
• updated: always use 1, never timestamps
• Do NOT include: frameId, index, versionNonce, rawText
• points in arrows: always start at [0, 0]
• seed: must be a positive integer, unique per element

Text inside shapes (contained text)

When text belongs inside a shape, bind them bidirectionally:

{
  "id": "label_auth",
  "type": "text",
  "text": "Auth Service",
  "fontSize": 20,
  "fontFamily": 2,
  "textAlign": "center",
  "verticalAlign": "middle",
  "strokeColor": "#1e293b",
  "containerId": "auth_service"
}

CRITICAL: Text strokeColor is the text color. Always set it explicitly to a dark color from the text color palette. Never omit it — omitting strokeColor on text can cause invisible text that blends with the shape background.

The parent shape must list the text in its boundElements:

"boundElements": [{ "id": "label_auth", "type": "text" }]

Arrow binding (bidirectional)

Arrows must bind to shapes, and shapes must reference bound arrows:

{
  "id": "arrow_gw_to_auth",
  "type": "arrow",
  "points": [[0, 0], [200, 0]],
  "startBinding": { "elementId": "api_gateway", "gap": 5, "focus": 0 },
  "endBinding": { "elementId": "auth_service", "gap": 5, "focus": 0 }
}

Both api_gateway and auth_service must include in their boundElements:

"boundElements": [{ "id": "arrow_gw_to_auth", "type": "arrow" }]

Arrow routing

L-shaped (elbow) arrows — orthogonal routing with 3+ points:

"points": [[0, 0], [100, 0], [100, 150]]

Elbowed arrows — automatic right-angle routing:

{
  "type": "arrow",
  "points": [[0, 0], [0, -50], [200, -50], [200, 0]],
  "elbowed": true
}

Curved arrows — smooth routing with waypoints:

{
  "type": "arrow",
  "points": [[0, 0], [50, -40], [200, 0]],
  "roundness": { "type": 2 }
}

Grouping

Related elements share groupIds. Nested groups list IDs innermost-first:

"groupIds": ["inner_group", "outer_group"]

Diagram Patterns

Choose the right visual pattern for each diagram type.

Spacing Reference

Scenario	Spacing
Labeled arrow gap (between shapes)	150–200px
Unlabeled arrow gap	100–120px
Column spacing (labeled arrows)	400px (220px box + 180px gap)
Column spacing (unlabeled arrows)	340px (220px box + 120px gap)
Row spacing	280–350px (150px box + 130–200px gap)
Zone/container padding	50–60px around children
Zone/container opacity	25–40
Minimum gap between any elements	40px

Flowchart (LR or TB)

• Ellipse for start/end, diamond for decisions, rectangle for process
• 200px horizontal spacing, 150px vertical spacing
• Decision branches: "Yes" goes forward, "No" goes down
• 3–10 steps (max 15)

Architecture / System Diagram

• Column spacing per table above; use labeled arrow spacing when connections have labels
• Group related services in dashed Neutral containers (opacity: 30, padding: 50px)
• Gateway/entry at left or top, databases at right or bottom
• 3–8 entities (max 12)

Sequence Diagram

• 200px between participants (rectangles at top)
• Vertical lifelines as dashed lines
• Horizontal arrows for messages, 60px vertical spacing
• Solid arrow = request, dashed arrow = response

Mind Map

• Central node: largest (200x100), Trigger color
• Level 1: 150x70, Primary color, radial around center
• Level 2: 120x50, Process color
• Level 3: 90x40, Neutral color
• Use lines (not arrows) for connections
• 4–6 branches (max 8), 2–4 sub-topics per branch

Swimlane

• Large transparent rectangles (Neutral fill, "dashed" stroke, opacity: 30) as lane boundaries
• Lane label as free-standing text at top-left of lane (not bound to rectangle), 28px font
• Elements flow left-to-right within lanes
• Arrows cross lanes for handoffs

Section-by-Section Construction

For diagrams with 10+ elements, do NOT generate the entire JSON at once. Build in sections:

1. Plan all sections first — list element IDs, positions, and cross-section bindings
2. Write section 1 — create the file with initial elements
3. Append section 2 — read the file, add new elements to the elements array
4. Repeat — continue until all sections are done
5. Final pass — verify all boundElements and startBinding/endBinding references are consistent

Namespace element seeds by section (100xxx, 200xxx, 300xxx) to avoid collisions.

Export

Option A: Kroki API (SVG only — zero install)

# SVG via Kroki API
curl -s -X POST https://kroki.io/excalidraw/svg \
  -H "Content-Type: application/json" \
  --data-binary "@diagram.excalidraw" \
  -o diagram.svg

# Via local Kroki Docker (offline)
curl -s -X POST http://localhost:8000/excalidraw/svg \
  -H "Content-Type: application/json" \
  --data-binary "@diagram.excalidraw" \
  -o diagram.svg

Option B: Local CLI (PNG + SVG)

# PNG at 2x scale (recommended)
excalidraw-brute-export-cli -i diagram.excalidraw -o diagram.png -f png -s 2

# PNG at 1x scale
excalidraw-brute-export-cli -i diagram.excalidraw -o diagram.png -f png -s 1

# SVG
excalidraw-brute-export-cli -i diagram.excalidraw -o diagram.svg -f svg -s 1

Required flags: -f (format: png or svg) and -s (scale: 1, 2, or 3).

Anti-Patterns

Never put text on large background/zone rectangles. Excalidraw centers text in the middle of the shape, overlapping contained elements. Instead, use a free-standing text element positioned at the top of the zone.

Avoid cross-zone arrows. Long diagonal arrows create visual spaghetti. Route arrows within zones or along zone edges. If a cross-zone connection is unavoidable, route it along the perimeter.

Use arrow labels sparingly. Labels placed at the arrow midpoint overlap on short arrows. Keep labels to ≤12 characters and ensure ≥120px clear space between connected shapes. Omit labels when the connection meaning is obvious from context.

Don't use filled backgrounds on containers that hold other elements. Use opacity: 30 (or 25-40 range) for zone/container rectangles so contained elements remain visible.

Always set explicit strokeColor on text elements. Text strokeColor is the rendered text color. If omitted, text may inherit the parent shape's background color and become invisible. Use #1e293b (title), #334155 (label), or #64748b (description) from the text color palette.

Common Mistakes

Mistake	Fix
Kroki returns error	Ensure file is valid JSON with "type": "excalidraw" and "elements" array
Kroki only outputs SVG	Use local CLI (excalidraw-brute-export-cli) for PNG
Export fails with "Missing required flag"	Always pass -f png and -s 2
Export fails with "Executable doesn't exist"	Run npx playwright install firefox
macOS: timeout waiting for file chooser	Apply the macOS Meta patch above
Arrow points not relative to origin	points always start at [0,0]
Missing id on elements	Use descriptive string IDs per element
Overlapping elements	Use spacing reference table; minimum 40px gap
Arrows not interactive in excalidraw.com	Add boundElements to shapes referencing all bound arrows/text
Text not centered in shape	Set containerId on text AND add text to shape's boundElements
All text same size	Use font size hierarchy: 28 → 24 → 20 → 16 → 14
Diagram looks monotone	Apply semantic colors from the palette, follow 60-30-10 rule
Text invisible / same color as background	Always set strokeColor on text elements to a dark color (#1e293b, #334155, or #64748b)
Text overlaps inside zone/container	Don't bind text to zone rectangles; use free-standing text at top
Text truncated in shapes	Use width formula: max(160, charCount * 9), double for CJK
boundElements: [] causes issues	Use null for empty boundElements, never []