Excalidraw Skill

Step 0: Setup

Load companion skills when needed

• Drawing or styling a diagram → load excalidraw-design-guide (colors, sizing, anti-patterns)
• Building a multi-element diagram or reviewing one → must load excalidraw-workflow (planning, progressive drawing, review checklist)
• Mindmap or quality-sensitive visual request → must load both excalidraw-workflow and excalidraw-design-guide
• Just checking status, exporting, or a single command → no companion skills needed

Check if canvas is running

excalidraw status

Returns {"status":"healthy","timestamp":"...","elements_count":N,"websocket_clients":N} if running.

Start canvas if not running

excalidraw serve --port 3000

For autonomous multi-step runs, avoid foreground blocking. Use a detached startup and then verify health:

nohup excalidraw serve --port 3000 >/tmp/excalidraw-serve.log 2>&1 &
excalidraw status

Browser required for: viewport, screenshot, and mermaid commands. These route through the browser tab via WebSocket — they return a 503 error if no browser has the canvas open. Open http://localhost:3000 before using any of these commands.

Install CLI (one-time)

bun add -g github:opencoredev/excalidraw-cli

Global URL override

export EXCALIDRAW_URL=http://localhost:3000

All commands respect EXCALIDRAW_URL. Override per-command with --url <url>.

Execution Contract (Continuous Delivery)

When a request implies implementation (not just explanation), run this default loop:

1. Start with a minimal working step that produces visible output fast.
2. Expand in small increments, validating each increment before moving on.
3. Keep going without stopping between increments unless blocked by missing credentials or irreversible risk.
4. Before finishing, run one end-to-end verification sweep (describe, fit viewport, screenshot).

No pause rule: do not stop after a single successful command if there are still unfinished checkpoints.

Failure handling: treat errors as fix-and-continue, not stop-and-wait.

• If 503 No frontend client connected, open canvas and retry the failed step.
• If a command depends on IDs, run excalidraw describe, repair IDs/ordering, retry.
• If batch or mermaid receives no input, provide file or stdin explicitly and continue.

If the user asks to "ship" or requests commit/push behavior:

• Stage only relevant files.
• Commit each verified unit with clear intent-focused messages.
• Push after final verification.

Progress contract: after each checkpoint, report what changed and run the next checkpoint immediately.

⚡ Draw Element by Element — Don't Make the User Wait

Create each element individually so the user sees every shape appear on canvas and can redirect if something is wrong.

excalidraw create --type rectangle --id svc-a --x 100 --y 100 --width 160 --height 60 --text "Service A" --stroke-color "#1971c2" --fill "#a5d8ff"
excalidraw viewport --fit

excalidraw create --type rectangle --id svc-b --x 100 --y 240 --width 160 --height 60 --text "Service B" --stroke-color "#2f9e44" --fill "#b2f2bb"
excalidraw viewport --fit

excalidraw create --type arrow --x 0 --y 0 --start svc-a --end svc-b
excalidraw viewport --fit

Order: zones/containers first → nodes one by one → arrows one by one → detail labels last.

Rule: your first tool call must be a draw command. Do not reason through the whole diagram before starting.

excalidraw batch is best for complete diagrams where all elements and their arrows are defined together — arrow bindings are computed across the whole set at once, which gives better geometry. For live incremental drawing, use individual create calls.

Mindmap Quality Mode (use for any mindmap request unless user explicitly asks for rough/freeform brainstorming)

Mandatory constraints:

1. One center node with 5 primary branches in distinct directions.
2. Each primary branch has one continuation node in the same direction.
3. All branch labels must be inside nodes (label.text), never detached text elements.
4. Use only bound arrows (--start / --end), no raw coordinate links.
5. Run visual QA and fix until branches look balanced and readable.

Quick QA checks (must pass before done):

• Center appears central to all first-level branches.
• Branches are directionally distinct (up/right/down-right/down-left/left or equivalent spread).
• No floating text and no overlapping nodes.
• excalidraw describe shows expected node count and branch connectivity.

Inline Self-Check (before EVERY create)

1. Will the text fit? width = max(160, charCount * 11 + 40). Go wider when unsure — truncation looks worse than a wide box.
2. Multi-word labels: measure the longest single word: max(160, longestWord * 11 + 80)
3. Shapes before arrows: arrows bind to shapes by ID — the shape must exist first.
4. Enough gap? At least 60px between shapes, 80px between tiers.

Fix immediately: excalidraw update <id> --width <wider> before moving on.

Arrow binding rules

• Always --start <id> --end <id> — never raw coordinates to connect shapes
• Shapes first, arrows second — every time, no exceptions
• Arrow passes through a box? Shapes too close, or arrow wasn't bound. Delete, increase gap, recreate with --start/--end.

Quality gate (only when something looks off)

excalidraw describe   # spot-check IDs and positions
excalidraw viewport --fit

Command Reference

Server

excalidraw serve [--port 3000] [--host localhost]   # Start server (blocks)
excalidraw serve --port 3000 --host 0.0.0.0         # Bind to all interfaces
excalidraw status                                    # Health check
excalidraw stop                                      # Prints Ctrl+C instructions

Create element — all flags

excalidraw create \
  --type <type> \          # rectangle | ellipse | diamond | arrow | text | line | freedraw (required)
  --x <n> --y <n> \        # Position (required)
  --width <n> --height <n> \
  --text "Label" \         # Shape label (stored as label.text) or text element content
  --id "my-id" \           # Custom ID — set this for any shape you'll reference with arrows
  --stroke-color "#1971c2" \
  --fill "#a5d8ff" \       # backgroundColor
  --stroke-width <n> \
  --stroke-style solid|dashed|dotted \
  --roughness <0-3> \      # 0 = sharp, 3 = very rough
  --opacity <0-100> \
  --font-size <n> \        # Text elements only
  --start <id> \           # Arrow: bind start to shape edge
  --end <id> \             # Arrow: bind end to shape edge
  --start-arrowhead arrow|bar|dot|triangle|none \
  --end-arrowhead arrow|bar|dot|triangle|none

Update element

excalidraw update <id> --text "New" --stroke-color "#e03131"
excalidraw update <id> --x 200 --y 300 --width 220 --height 80
excalidraw update <id> --fill "#ffd8a8" --stroke-style dashed --opacity 80

Read / delete

excalidraw get <id>
excalidraw query                   # All elements
excalidraw query --type rectangle  # Filter by type
excalidraw delete <id>
excalidraw clear                   # Remove all elements
excalidraw describe                # Human-readable summary of all elements

Batch create (best for complete diagrams)

excalidraw batch diagram.json      # From file
cat diagram.json | excalidraw batch  # From stdin (also accepts bare array)

Batch JSON — full property set:

{
  "elements": [
    {
      "id": "svc-a",
      "type": "rectangle",
      "x": 100, "y": 100, "width": 180, "height": 60,
      "label": {"text": "Service A"},
      "strokeColor": "#1971c2",
      "backgroundColor": "#a5d8ff",
      "fillStyle": "solid",
      "strokeStyle": "solid",
      "strokeWidth": 2,
      "roughness": 0,
      "opacity": 100,
      "roundness": {"type": 3}
    },
    {
      "id": "db",
      "type": "rectangle",
      "x": 100, "y": 240, "width": 180, "height": 60,
      "label": {"text": "Database"},
      "strokeColor": "#0c8599",
      "backgroundColor": "#99e9f2"
    },
    {
      "type": "arrow",
      "x": 0, "y": 0,
      "start": {"id": "svc-a"},
      "end": {"id": "db"},
      "label": {"text": "SQL"},
      "strokeStyle": "dashed",
      "endArrowhead": "arrow",
      "elbowed": true
    }
  ]
}

Batch-only properties (not exposed as CLI flags, only via batch JSON):

• fillStyle: "hachure" | "solid" | "cross-hatch" | "dots" | "zigzag" | "zigzag-line" — default is "hachure" (Excalidraw's sketchy fill); use "solid" for clean fills
• roundness: {"type": 3} for rounded corners on rectangles/ellipses
• elbowed: true on arrows for right-angle routing instead of curved

Critical: "label": {"text": "..."} for shapes. "text": "..." directly on "type": "text" elements only.

Scene I/O

excalidraw export                            # Print .excalidraw JSON to stdout
excalidraw export --out scene.excalidraw     # Write to file
excalidraw import scene.excalidraw           # Import — replaces canvas (default)
excalidraw import scene.excalidraw --mode merge  # Merge with existing elements

excalidraw snapshot v1                       # Save named in-memory snapshot
excalidraw restore v1                        # Restore snapshot (clears canvas first)

Snapshots are in-memory — they're lost when the server restarts, same as canvas state. Use excalidraw export --out backup.excalidraw before stopping the server.

Viewport & screenshot (browser must be open)

excalidraw viewport --fit                    # Zoom to fit all elements
excalidraw viewport --element <id>           # Center on element
excalidraw viewport --zoom 1.5              # Set zoom level (1 = 100%)
excalidraw viewport --offset-x <n> --offset-y <n>  # Manual scroll offset

excalidraw screenshot                        # Capture PNG (base64 to stdout)
excalidraw screenshot --format svg --out diagram.svg
excalidraw screenshot --out check.png

Layout

excalidraw align id1 id2 id3 --alignment left|right|center|top|bottom|middle
excalidraw distribute id1 id2 id3 --direction horizontal|vertical  # needs 3+
excalidraw group id1 id2 id3                # Assigns shared groupId; returns groupId
excalidraw ungroup <groupId>
excalidraw duplicate id1 id2 [--dx 20] [--dy 20]
excalidraw lock id1 id2                     # Prevent UI edits
excalidraw unlock id1 id2

Export & sharing

excalidraw url                              # Encrypted excalidraw.com link (uploads scene)
excalidraw mermaid diagram.mmd              # Convert Mermaid → Excalidraw (browser required)
echo "graph TD; A-->B" | excalidraw mermaid
excalidraw guide                            # Print color palette, sizing, layout rules

Element Types Reference

Common Patterns

Architecture diagram

{
  "elements": [
    {"id":"zone","type":"rectangle","x":40,"y":40,"width":500,"height":400,
     "backgroundColor":"#e9ecef","strokeColor":"#868e96","opacity":40,
     "fillStyle":"solid","label":{"text":"Backend"}},
    {"id":"api","type":"rectangle","x":80,"y":100,"width":200,"height":60,
     "strokeColor":"#1971c2","backgroundColor":"#a5d8ff","fillStyle":"solid",
     "roundness":{"type":3},"label":{"text":"API Gateway"}},
    {"id":"db","type":"rectangle","x":80,"y":260,"width":200,"height":60,
     "strokeColor":"#0c8599","backgroundColor":"#99e9f2","fillStyle":"solid",
     "roundness":{"type":3},"label":{"text":"Database"}},
    {"type":"arrow","x":0,"y":0,"start":{"id":"api"},"end":{"id":"db"},
     "label":{"text":"SQL"},"strokeStyle":"dashed"}
  ]
}

Flowchart

{
  "elements": [
    {"id":"start","type":"ellipse","x":160,"y":40,"width":120,"height":60,
     "strokeColor":"#2f9e44","backgroundColor":"#b2f2bb","fillStyle":"solid","label":{"text":"Start"}},
    {"id":"step1","type":"rectangle","x":140,"y":160,"width":160,"height":60,
     "strokeColor":"#1971c2","backgroundColor":"#a5d8ff","fillStyle":"solid","label":{"text":"Process Data"}},
    {"id":"decide","type":"diamond","x":140,"y":280,"width":160,"height":80,
     "strokeColor":"#e8590c","backgroundColor":"#ffd8a8","fillStyle":"solid","label":{"text":"Valid?"}},
    {"type":"arrow","x":0,"y":0,"start":{"id":"start"},"end":{"id":"step1"}},
    {"type":"arrow","x":0,"y":0,"start":{"id":"step1"},"end":{"id":"decide"}}
  ]
}

Iterative Refinement Loop

excalidraw batch diagram.json
  → excalidraw describe           (verify IDs exist and positions look right)
  → excalidraw viewport --fit     (fit view)
  → excalidraw screenshot --out /tmp/check.png   (visual check)
  → [issues?] excalidraw update <id> --width 220
  → excalidraw screenshot --out /tmp/check2.png
  → [done] excalidraw export --out backup.excalidraw

Troubleshooting