Skill

SVG Diagram Generation

Name: SVG Diagram Generation
Author: CopilotKit

generate SVG diagrams for system visualization

Published by CopilotKit Updated Jul 12

Covers CopilotKit Diagrams SVG Design

Description

Generating rich inline SVG diagrams to visually explain systems, processes, architectures, and abstract concepts.

SKILL.md

SVG Diagram Generation Skill

You can generate rich, inline SVG diagrams to visually explain concepts. Use this skill whenever a visual would help the user understand a system, process, architecture, or mechanism better than text alone.

Delivery

Diagrams ship through the generateSandboxedUi tool: the SVG markup goes in the html parameter, where it streams to the user element by element. SVG presentation attributes (fill, stroke, font-size) carry all styling here — if a diagram needs CSS animation classes, declare them in the css parameter, never in a <style> block inside html. Static diagrams need no jsFunctions or jsExpressions.

When to Use

Explaining how something works (load paths, circuits, pipelines, algorithms)
Showing architecture or structure (system diagrams, component layouts)
Illustrating processes or flows (flowcharts, data flow, decision trees)
Building intuition for abstract concepts (attention mechanisms, gradient descent, recursion)

SVG Setup

Always use this template:

<svg width="100%" viewBox="0 0 680 H" xmlns="http://www.w3.org/2000/svg">
  <defs>
    <marker id="arrow" viewBox="0 0 10 10" refX="8" refY="5"
            markerWidth="6" markerHeight="6" orient="auto-start-reverse">
      <path d="M2 1L8 5L2 9" fill="none" stroke="context-stroke"
            stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round"/>
    </marker>
  </defs>
  <!-- Content here -->
</svg>

Width is always 680px via viewBox. Set width="100%" so it scales responsively.
H (height) = bottom-most element's y + height + 40px padding. Don't guess — compute it.
Safe content area: x=40 to x=640, y=40 to y=(H-40).
No wrapping divs, no <html>, <head>, <body>, or DOCTYPE.
Background is transparent — the host provides the background.

Core Design Rules

Typography

Two sizes only: 14px for titles/labels, 12px for subtitles/descriptions.
Two weights only: 400 (regular), 500 (medium/bold). Never use 600 or 700.
Font: Use font-family="system-ui, -apple-system, sans-serif" or inherit from host.
Always set text-anchor="middle" and dominant-baseline="central" for centered text in boxes.
Sentence case always. Never Title Case or ALL CAPS.

Text Width Estimation

At 14px, each character ~ 8px wide. At 12px, each character ~ 7px wide.

"Load Balancer" (13 chars) at 14px ~ 104px -> needs rect ~ 140px wide (with padding).
Always compute: rect_width = max(title_chars x 8, subtitle_chars x 7) + 48px padding.

Colors (Light/Dark Mode Safe)

Use these semantic color sets that work in both modes:

Teal:    fill="#E1F5EE" stroke="#0F6E56" text="#085041"  (dark: fill="#085041" stroke="#5DCAA5" text="#9FE1CB")
Purple:  fill="#EEEDFE" stroke="#534AB7" text="#3C3489"  (dark: fill="#3C3489" stroke="#AFA9EC" text="#CECBF6")
Coral:   fill="#FAECE7" stroke="#993C1D" text="#712B13"  (dark: fill="#712B13" stroke="#F0997B" text="#F5C4B3")
Amber:   fill="#FAEEDA" stroke="#854F0B" text="#633806"  (dark: fill="#633806" stroke="#EF9F27" text="#FAC775")
Blue:    fill="#E6F1FB" stroke="#185FA5" text="#0C447C"  (dark: fill="#0C447C" stroke="#85B7EB" text="#B5D4F4")
Gray:    fill="#F1EFE8" stroke="#5F5E5A" text="#444441"  (dark: fill="#444441" stroke="#B4B2A9" text="#D3D1C7")
Red:     fill="#FCEBEB" stroke="#A32D2D" text="#791F1F"  (dark: fill="#791F1F" stroke="#F09595" text="#F7C1C1")
Green:   fill="#EAF3DE" stroke="#3B6D11" text="#27500A"  (dark: fill="#27500A" stroke="#97C459" text="#C0DD97")
Pink:    fill="#FBEAF0" stroke="#993556" text="#72243E"  (dark: fill="#72243E" stroke="#ED93B1" text="#F4C0D1")

Color meaning, not sequence: Don't rainbow-cycle. Use 2-3 colors per diagram. Map colors to categories or physical properties (warm = heat/energy, cool = calm/cold, gray = structural/neutral).

If you're rendering inside a system that supports CSS variables, prefer:

var(--color-text-primary) for primary text
var(--color-text-secondary) for muted text
var(--color-border-tertiary) for light borders

Shapes & Layout

Stroke width: 0.5px for borders, 1.5px for arrows/connectors.
Corner radius: rx="4" for subtle rounding, rx="8" for emphasized. rx="20" for large containers.
Spacing: 60px minimum between boxes, 24px padding inside boxes, 12px text-to-edge clearance.
Single-line box: 44px tall. Two-line box: 56px tall.
Max 4-5 nodes per row at 680px width. If more, split into multiple diagrams.
All connectors need fill="none" — SVG defaults fill to black, which turns paths into black blobs.

Component Patterns

Single-Line Node

<g>
  <rect x="100" y="20" width="180" height="44" rx="8"
        fill="#EEEDFE" stroke="#534AB7" stroke-width="0.5"/>
  <text x="190" y="42" text-anchor="middle" dominant-baseline="central"
        font-size="14" font-weight="500" fill="#3C3489">Node title</text>
</g>

Two-Line Node

<g>
  <rect x="100" y="20" width="200" height="56" rx="8"
        fill="#E6F1FB" stroke="#185FA5" stroke-width="0.5"/>
  <text x="200" y="38" text-anchor="middle" dominant-baseline="central"
        font-size="14" font-weight="500" fill="#0C447C">Title</text>
  <text x="200" y="56" text-anchor="middle" dominant-baseline="central"
        font-size="12" fill="#185FA5">Short subtitle</text>
</g>

Arrow Connector

<line x1="200" y1="76" x2="200" y2="120"
      stroke="#534AB7" stroke-width="1.5" marker-end="url(#arrow)"/>

Dashed Flow Indicator

<line x1="200" y1="76" x2="200" y2="120"
      stroke="#534AB7" stroke-width="1.5" stroke-dasharray="4 3"/>

Leader Line with Label (for annotations)

<line x1="440" y1="100" x2="500" y2="130"
      stroke="currentColor" stroke-width="0.5" stroke-dasharray="4 4" opacity="0.5"/>
<circle cx="440" cy="100" r="2" fill="currentColor" opacity="0.5"/>
<text x="506" y="134" font-size="12" fill="currentColor" opacity="0.7">Annotation text</text>

Large Container (for structural diagrams)

<rect x="80" y="40" width="520" height="300" rx="20"
      fill="#E1F5EE" stroke="#0F6E56" stroke-width="0.5"/>
<text x="340" y="68" text-anchor="middle"
      font-size="14" font-weight="500" fill="#085041">Container name</text>

Diagram Types & When to Use Each

1. Flowchart

When: Sequential processes, decision trees, pipelines. Layout: Top-to-bottom or left-to-right. Single direction only. Rules:

Arrows must never cross unrelated boxes. Route around with L-bends if needed.
Keep all same-type boxes the same height.
Max 4-5 nodes per diagram. Break complex flows into multiple diagrams.

2. Structural Diagram

When: Containment matters — things inside other things (architecture, org charts, system components). Layout: Nested rectangles. Outer = container, inner = regions. Rules:

Max 2-3 nesting levels.
20px minimum padding inside every container.
Use different color ramps for parent vs child to show hierarchy.

3. Illustrative Diagram

When: Building intuition. "How does X actually work?" Layout: Freeform — follows the subject's natural geometry. Rules:

Shapes can be freeform (paths, ellipses, polygons), not just rects.
Color encodes intensity, not category (warm = active, cool = dormant).
Overlap shapes for depth, but never let strokes cross text.
Labels go in margins with leader lines pointing to the relevant part.

Critical Checks Before Finalizing

ViewBox height: Find your lowest element (max y + height). Set H = that + 40px.
No content past x=640 or below y=(H-40).
Text fits in boxes: (char_count x 8) + 48 < rect_width for 14px text.
No arrows through boxes: Trace every line's path — if it crosses a rect, reroute.
All <path> connectors have fill="none".
All text has appropriate fill color — never rely on inheritance (SVG defaults to black).
Colors work in dark mode: If using hardcoded colors, provide both light and dark variants. If using CSS variables, you're fine.

Multi-Diagram Approach

For complex topics, use multiple smaller SVGs instead of one dense one:

Each SVG should have 3-5 nodes max.
Write explanatory text between diagrams.
First diagram = overview, subsequent = zoom into subsections.
Never promise diagrams you don't deliver.

Example: Simple 3-Step Flow

<svg width="100%" viewBox="0 0 680 260" xmlns="http://www.w3.org/2000/svg">
  <defs>
    <marker id="arrow" viewBox="0 0 10 10" refX="8" refY="5"
            markerWidth="6" markerHeight="6" orient="auto-start-reverse">
      <path d="M2 1L8 5L2 9" fill="none" stroke="context-stroke"
            stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round"/>
    </marker>
  </defs>

  <!-- Step 1 -->
  <rect x="230" y="20" width="220" height="56" rx="8"
        fill="#E1F5EE" stroke="#0F6E56" stroke-width="0.5"/>
  <text x="340" y="38" text-anchor="middle" dominant-baseline="central"
        font-size="14" font-weight="500" fill="#085041">User request</text>
  <text x="340" y="56" text-anchor="middle" dominant-baseline="central"
        font-size="12" fill="#0F6E56">HTTP POST /api/data</text>

  <!-- Arrow 1->2 -->
  <line x1="340" y1="76" x2="340" y2="100" stroke="#534AB7"
        stroke-width="1.5" marker-end="url(#arrow)"/>

  <!-- Step 2 -->
  <rect x="230" y="106" width="220" height="56" rx="8"
        fill="#EEEDFE" stroke="#534AB7" stroke-width="0.5"/>
  <text x="340" y="124" text-anchor="middle" dominant-baseline="central"
        font-size="14" font-weight="500" fill="#3C3489">Server processing</text>
  <text x="340" y="142" text-anchor="middle" dominant-baseline="central"
        font-size="12" fill="#534AB7">Validate and transform</text>

  <!-- Arrow 2->3 -->
  <line x1="340" y1="162" x2="340" y2="186" stroke="#854F0B"
        stroke-width="1.5" marker-end="url(#arrow)"/>

  <!-- Step 3 -->
  <rect x="230" y="192" width="220" height="56" rx="8"
        fill="#FAEEDA" stroke="#854F0B" stroke-width="0.5"/>
  <text x="340" y="210" text-anchor="middle" dominant-baseline="central"
        font-size="14" font-weight="500" fill="#633806">Database write</text>
  <text x="340" y="228" text-anchor="middle" dominant-baseline="central"
        font-size="12" fill="#854F0B">INSERT into table</text>
</svg>

Tips for Great Diagrams

Less is more: A clean 4-node diagram teaches better than a cramped 12-node one.
Color = meaning: Warm colors for active/hot/important, cool for passive/cold/secondary, gray for structural.
Streaming effect: Since SVGs render top-to-bottom as tokens arrive, structure your elements top-down for a natural build-up animation.
Annotations on the side: Put explanatory labels in the right margin (x > 560) with leader lines pointing to the relevant element.
Consistent heights: All boxes of the same type should be the same height.
Whitespace is your friend: Don't fill every pixel. Breathing room makes diagrams readable.

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