Diagram Design

Create visual diagrams as self-contained HTML files with inline SVG and CSS, following an opinionated editorial design system.

Thirty-nine visual types. Semantic patterns describe behavior independently; type references describe layout. Details load from references/ only when selected.

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0. First-time setup — style guide gate

Before generating your first diagram in a new project, verify the style guide has been customized.

Don't silently ship default-skinned diagrams into a branded project.

First check the project root for a .diagram-design marker and resolve it per references/profiles.md. A valid marker whose profile exists selects that file directly and skips this gate; profile: default also skips it. A malformed or missing-profile marker follows the visible failure handling in that reference. Never copy a marker-selected profile over the installed working copy.

Open references/style-guide.md and check the default tokens. If they're still the shipped defaults (paper #f5f5f5, ink #2d3142, accent #eb6c36 atomic-tangerine), pause and ask the user:

"This is your first diagram in this project. The style guide is still at the default (neutral white-smoke + atomic-tangerine). Do you want to customize it to match your brand first? Options: (a) pull from your website URL, (b) extract from an installed skill, (c) extract from a local folder / design-system directory, (d) paste tokens manually, (e) proceed with the default for now, (f) load a saved client profile."

Then branch per the matching section of references/onboarding.md; for (f) follow references/profiles.md.

Once the style guide has been customized (or the user explicitly opted for default), skip this gate on subsequent runs. A leading profile header names the copied-in active profile. Without a header, any semantic-role value or typography family differing from shipped defaults means custom-unsaved: skip the gate and offer to save it as a profile. All-default tokens with no marker/header trigger the gate. At the end of every onboarding method, offer to save the result as a named client profile per references/profiles.md.

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1. Philosophy

The highest-quality move is usually deletion.

Applied to schematics:

• Every node represents a distinct idea. Two nodes that always travel together are one node.
• Every connection carries information. If the relationship is obvious from layout, remove the line.
• Coral is editorial, not a flag. 1–2 focal nodes per diagram. Using it on 5 nodes erases the signal.
• The schematic isn't done when everything is added. It's done when nothing can be removed.

Target density: 4/10. Enough to be technically complete. Not so dense it needs a guide. Above 9 nodes, it's probably two diagrams.

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2. When to Use

Use for any of the 39 visual types (§3) when a reader will learn more from a visual than from prose, a table, or a bulleted list.

Don't use for:

• Quick unicode diagrams → use wiretext.
• Lists of things → table or bullets.
• Simple before/after → table.
• One-shape "diagrams" → just write the sentence.

Before drawing, ask: Would the reader learn more from this than from a well-written paragraph? If no, don't draw.

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3. Selection: semantic pattern, then visual type

When behavior, state, enforcement, or risk carries the meaning, first load references/semantic-patterns.md and choose one primary pattern. Then choose the nearest visual type for layout. If no pattern matches, choose the type directly.

Behavioral trigger	Semantic pattern → nearest type
Fan-in, queue depth, finite capacity, bottleneck	Fan-in queue / bottleneck → Data flow
Repeated Question / Input / Governance / Output slots across stages	Stage framework with semantic slots → Process
Conversation or loose input becomes a structured durable artifact	Unstructured input → structured artifact → Data flow
Two rule traces need pass/fail/skipped/not-reached and first divergence	Paired policy-evaluation traces → Flowchart
Trust boundaries plus permitted/forbidden ingress or deploy paths	Secure paved road → Architecture
Controls grouped by where they are enforced	Governance / control catalog → Layer stack
Defenses compensate for prior gaps and residual risk propagates	Compensating security layers → Layer stack

The pattern owns semantic primitives and its tighter budget; the type owns layout grammar. Use references/animation.md only when motion is requested or materially clarifies ordered change; static remains the default.

Visual-type guide (39)

If you're showing…	Use	Reference
Components + connections in a system	Architecture	type-architecture.md
Legacy IT landscape grouped by phase/department; documents the before state in modernization proposals	IT current-state	type-it-state.md
Decision logic with branches	Flowchart	type-flowchart.md
Time-ordered messages between actors	Sequence	type-sequence.md
States + transitions + guards	State machine	type-state.md
Entities + fields + relationships	ER / data model	type-er.md
Events positioned in time	Timeline	type-timeline.md
Cross-functional process with handoffs	Swimlane	type-swimlane.md
Two-axis positioning / prioritization	Quadrant	type-quadrant.md
Multiple entities scored across 3–5 quantitative criteria	Radar / Spider	type-radar.md
One quantitative series across cyclic categories; angle=category, radius=magnitude	Polar chart	type-polar.md
Reinforcing cycle / flywheel where the last step feeds the first and a shared hub accumulates state	Loop	type-loop.md
Hierarchy through containment / scope	Nested	type-nested.md
Parent → children relationships	Tree	type-tree.md
Human/agent/team ownership, reporting, routing, escalation	Org chart	type-org-chart.md
Stacked abstraction levels	Layer stack	type-layers.md
Overlap between sets	Venn	type-venn.md
Ranked hierarchy or conversion drop-off	Pyramid / funnel	type-pyramid.md
Quantitative comparison across categories	Bar chart	type-bar.md
Part-of-whole where the relative sizes are the story	Treemap	type-treemap.md
Continuous trends over time, change between exactly two states (slopegraph), one distribution per series (ridgeline), or rank movement across several snapshots (bump)	Line chart	type-line.md
Tasks and phases on a timeline	Gantt	type-gantt.md
Distribution and correlation between two variables, three with area-sized marks (bubble), or one variable with a dot per item (beeswarm)	Scatter plot	type-scatter.md
End-to-end data stack on a container cluster	High-Level	type-high-level.md
Multi-actor sequential process with data handoffs	Process	type-process.md
Multi-tier data storage with quality levels and access policies	Medallion	type-medallion.md
Role-scoped data flow: who does what at each pipeline step	Data flow	type-data-flow.md
Integration topology of a data platform — sources → core → consumers	DP integration	type-dp-integration.md
Per-role / per-component access permissions matrix	DP security matrix	type-dp-security-matrix.md
A quantity splitting and merging across stages, band width = amount	Sankey	type-sankey.md
Causes of one observed effect, grouped by category (root-cause analysis)	Fishbone	type-fishbone.md
Value chain against evolution — what to build, buy, and what is moving	Wardley map	type-wardley.md
Work-in-progress by state, with WIP limits and blocked items	Kanban	type-kanban.md
What a person does across stages of an experience, and how it feels	User journey	type-journey.md
Where software runs — zones, hosts, artifacts, replicas, ports	Deployment	type-deployment.md
What depends on what, with fan-in and cycles a tree cannot express	Dependency graph	type-dependency.md
Classes with operations, inheritance, composition (other UML routes elsewhere)	UML class	type-uml-class.md
Narrative backbone sliced into releases, with the cut line	Story map	type-story-map.md
Physical tables: SQL types, constraints, indexes, column-level FKs	Database schema	type-db-schema.md

Rules of thumb:

• If a 3-column table communicates the same thing, pick the table.
• If two types seem useful, pick the dominant axis; a semantic pattern may add behavior-specific primitives, not a second layout grammar.
• If you're past the complexity budget (§7), split into an overview + detail.

Always load the chosen type reference linked in the guide before drawing. When routed above, also load semantic-patterns.md; when animation is chosen, load animation.md.

Confirm before drawing

Before rendering, state the plan in one short message: the chosen visual type (and semantic pattern, if routed), the size preset, and anything the complexity budget (§7) will force out. If the user is reachable, let them redirect before you draw; if not, proceed and note the assumptions beside the deliverable. Skip the pause only when the request already pins type, size, and content exactly.

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4. Universal Anti-patterns

These mark "AI slop" schematics of any type:

Anti-pattern	Why it fails
Dark mode + cyan/purple glow	Looks "technical" without design decisions
JetBrains Mono as blanket "dev" font	Mono is for technical content — ports, commands, URLs. Names go in Geist sans.
Identical boxes for every node	Erases hierarchy
Legend floating inside the diagram area	Collides with nodes
Arrow labels with no masking rect	Bleeds through the line
Vertical writing-mode text on arrows	Unreadable
3 equal-width summary cards as default	Generic grid — vary widths
Shadow on any element	Shadows are out. Borders are in.
rounded-2xl on boxes	Max radius 6–10px or none
Coral on every "important" node	Coral is 1–2 editorial accents, not a signaling system
Reproducing Mermaid's renderer layout	Imports automatic spacing and routing instead of making an editorial layout
Any breach of the six §6 connector rules	Diagonal slants, labels touching their stroke, masks clipped by a later node, overlapping paths, shared attach points, transit behind a non-endpoint box — each is an automatic fail; §6 states them in full

Type-specific anti-patterns live in each type reference linked in the guide.

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5. Design System

The design system is skinnable. All colors, typography, and tokens live in a single source of truth — references/style-guide.md. This file describes semantic roles (paper, ink, muted, accent, link, …). The default skin is a cool editorial palette (white-smoke paper, jet-black ink, atomic-tangerine accent, blue-slate muted, silver hairlines); to apply your own brand, either edit style-guide.md directly or run the URL-based flow described in references/onboarding.md.

When specs below or in type references mention "ink", "accent", "muted", etc., look up the current hex value in style-guide.md.

Semantic roles (at a glance)

Role	Purpose
paper, paper-2	Page bg and container bg
ink	Primary text / stroke
muted, soft	Secondary text, default arrows, sublabels
rule, rule-solid	Hairline borders
accent, accent-tint	1–2 focal elements per diagram
link	HTTP/API calls, external arrows

Focal rule: accent goes on 1–2 elements max. Everything else is ink / muted / soft. If you're tempted to accent 4 things, you haven't decided what's focal yet.

Node type → treatment

Type	Fill	Stroke
Focal (1–2 max)	accent-tint	accent
Backend / API / Step	white	ink
Store / State	ink @ 0.05	muted
External / Cloud	ink @ 0.03	ink @ 0.30
Input / User	muted @ 0.10	soft
Optional / Async	ink @ 0.02	ink @ 0.20 dashed 4,3
Security / Boundary	accent @ 0.05	accent @ 0.50 dashed 4,4

Typography (summary — full spec in style-guide.md)

• Title — Instrument Serif, 1.75rem, 400 — H1 only
• Node name — Geist (sans), 12px, 600 — human-readable labels
• Sublabel — Geist Mono, 9px — ports, URLs, field types
• Eyebrow / tag — Geist Mono, 7–8px, uppercase, tracked — type tags, axis labels
• Arrow label — Geist Mono, 8px — annotation on arrows
• Editorial aside — Instrument Serif italic, 14px — callouts only

Korean labels — Geist and Instrument Serif carry no Hangul. Extend the family on that <text>, budget 1em per Unicode wide or full-width character and the Latin advance for every other, and never set Hangul below 12px. Full rules in style-guide.md.

Mono is for technical content only — never as a blanket "dev" font, and never JetBrains Mono.

<link href="https://fonts.googleapis.com/css2?family=Instrument+Serif:ital@0;1&family=Geist:wght@400;500;600&family=Geist+Mono:wght@400;500;600&family=Noto+Sans+KR:wght@400;500;600&family=Noto+Serif+KR:wght@400&display=swap" rel="stylesheet">

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6. Core SVG Primitives

Universal building blocks. Type-specialized primitives (lifeline, activation bar, region) live in the relevant type reference linked in the guide. Optional primitives:

• Editorial callouts → primitive-annotation.md
• Hand-drawn variant → primitive-sketchy.md
• Icon set (laptop, server, DB, K8s, Docker, AWS, …) → primitive-icons.md. Browse the gallery at assets/icons.html.
• Terminal / CLI-window variant → primitive-terminal.md
• Optional explanatory motion → animation.md

Background

Default: clean paper, no dot pattern. Single <rect> filled with paper. Don't wrap the diagram in a secondary container background — the diagram sits directly on the page.

<rect width="100%" height="100%" fill="#f5f5f5"/>

Optional: dotted paper variant. When a long-form editorial diagram benefits from textured ground (essays, hero diagrams on a dedicated page), opt in by adding the dots pattern and a second rect:

<defs>
  <pattern id="dots" width="22" height="22" patternUnits="userSpaceOnUse">
    <circle cx="1" cy="1" r="0.9" fill="rgba(45,49,66,0.10)"/>
  </pattern>
</defs>
<rect width="100%" height="100%" fill="#f5f5f5"/>
<rect width="100%" height="100%" fill="url(#dots)" opacity="0.6"/>

Don't use the dot pattern when the diagram sits inside a product page, slide, or card — the texture compounds with surrounding chrome and reads as noise.

Arrow markers (define all three, always)

<marker id="arrow" markerWidth="8" markerHeight="6" refX="7" refY="3" orient="auto">
  <polygon points="0 0, 8 3, 0 6" fill="#4f5d75"/>
</marker>
<marker id="arrow-accent" markerWidth="8" markerHeight="6" refX="7" refY="3" orient="auto">
  <polygon points="0 0, 8 3, 0 6" fill="#eb6c36"/>
</marker>
<marker id="arrow-link" markerWidth="8" markerHeight="6" refX="7" refY="3" orient="auto">
  <polygon points="0 0, 8 3, 0 6" fill="#2e5aa8"/>
</marker>

Arrow	Stroke	When
Default	muted #4f5d75	Internal, generic
Accent	coral #eb6c36	Primary / highlighted / headline
Link-blue	#2e5aa8	HTTP/API calls, external systems
Dashed	stroke-dasharray="5,4" + any color	Optional, passive, return, async

Draw arrows before boxes so z-order puts lines behind nodes.

Mandatory connector rules

These six rules are non-negotiable. Run the pre-output checklist (§9) to verify before producing any diagram.

1. Rounded right-angle (orthogonal) connectors are mandatory. Never use diagonal <line> or straight slanted paths between nodes that don't share an x or y axis. Every bend must be a quarter-arc with r=8 (or r=6 minimum for tight layouts). See references/type-architecture.md for the elbow-path formula. Reserve plain straight <line> only for connections whose endpoints share the same x or y coordinate. Diagonal connectors are an automatic fail.

2. Label-to-connector margin: 6–10px gap, always. A label must never sit on its arrow — the connector must remain visible. Place the label centered above (or beside, for vertical segments) the line with a minimum 6px gap between the bottom of the label's mask rect and the connector stroke. The opaque mask rect prevents the arrow from bleeding through, but the visible gap between mask edge and line preserves the reader's ability to trace the connection. If the label is large enough that 6px feels cramped, push it to 8–10px. Never let the mask rect touch or overlap the stroke.

3. No overlapping connectors. Two connectors must never share the same stroke path, run parallel on top of each other, or be drawn on top of each other for any segment. When two orthogonal arrows must cross at a single point, apply the bridge / hop primitive (see references/type-architecture.md § Crossing arrows). When two arrows naturally want to overlap, offset their routing by ≥12px so each line is independently traceable. If you find yourself stacking connectors, redesign the layout — it means two nodes are too close, or the diagram is over budget (split into overview + detail).

4. Shared edge → fan the attach points. When two or more connectors enter or exit the same edge of a box, each must have its own distinct attach point along that edge — no two connectors may share a single point on a box. Spread the attach points evenly along the edge with ≥12px between adjacent points (8px minimum for very small boxes). Routing rules:

   • For N connectors on an edge of length L, attach point k (1..N) sits at offset L * k / (N + 1) from the edge's leading corner.
   • When the connectors fan out to destinations on different sides, route each one orthogonally from its own attach point — no merging strokes near the box.
   • When two parallel connectors run in the same direction, keep them ≥12px apart along their entire length, not just at the attach point. Each arrow must remain independently traceable end-to-end.

   No connector may hide another. If you can't tell two arrows apart at a glance, the layout has failed.

5. A connector must not pass behind a box that isn't its source or destination — except when the box is geometrically unavoidable on a direct orthogonal path. Reroute around intervening boxes by default. The only legitimate exception is when a cross-cutting node (e.g., a footer service, a horizontal layer bar) physically sits between the connector's source and destination on the only straight path between them — for example, a METRICS arrow exiting an Observability footer bar and rising into a zone above must cross the Active Directory footer bar that sits between them. In that exception:

   • The stroke must be dashed (e.g., stroke-dasharray="4,3") to signal "transit, not interaction" — it tells the reader the intervening box is not an endpoint.
   • The label sits at the visible end of the connector (typically near the source) so it doesn't fall behind the intervening box.
   • No marker (arrowhead) may land on the intervening box's edge — the marker resolves at the true destination only.

   When in doubt, reroute. The exception exists for the narrow case where rerouting is geometrically impossible, not as a shortcut to avoid layout work.

6. A label mask must not overlap a node drawn after it. Rule 2 keeps the label off its own connector; this one keeps it off the boxes. Because nodes are painted after labels, a mask that lands partly inside a node is covered by the node fill and the text renders as a fragment sitting on the node border. Place the label on a segment of the connector that runs through open canvas — for a connector leaving a node's right edge, that means clearing the node's x + width before the mask starts. A mask fully inside a node is a badge chip and is fine; a mask overlapping a zone container is fine too, since zones are painted first. From a repository checkout, verify with python3 <repo-root>/scripts/verify-geometry.py <file>.

Node box — full pattern

<!-- 1. Opaque paper mask — prevents arrows bleeding through transparent fills -->
<rect x="X" y="Y" width="W" height="H" rx="6" fill="#f5f5f5"/>
<!-- 2. Styled box -->
<rect x="X" y="Y" width="W" height="H" rx="6" fill="FILL" stroke="STROKE" stroke-width="1"/>
<!-- 3. Rectangular type tag (rx=2, NOT a pill) -->
<rect x="X+8" y="Y+6" width="28" height="12" rx="2" fill="transparent" stroke="STROKE@0.40" stroke-width="0.8"/>
<text x="X+22" y="Y+15" fill="STROKE@0.8" font-size="7" font-family="'Geist Mono', monospace"
      text-anchor="middle" letter-spacing="0.08em">API</text>
<!-- 4. Node name (Geist sans — human-readable) -->
<text x="CX" y="CY+2" fill="#2d3142" font-size="12" font-weight="600"
      font-family="'Geist', sans-serif" text-anchor="middle">Node Name</text>
<!-- 5. Technical sublabel (Geist Mono) -->
<text x="CX" y="CY+18" fill="#4f5d75" font-size="9"
      font-family="'Geist Mono', monospace" text-anchor="middle">tech:port</text>

Arrow labels — always mask, always with margin

Every arrow label needs an opaque rect behind it. Without one it bleeds through the line. And the label must sit with a visible gap above the connector — never on top of it.

<!-- Mask sits 14px above the arrow (8px text height + 6px gap). Stroke is at ARROW_Y. -->
<rect x="MID_X-18" y="ARROW_Y-20" width="36" height="12" rx="2" fill="#f5f5f5"/>
<text x="MID_X" y="ARROW_Y-11" fill="#7a8399" font-size="8"
      font-family="'Geist Mono', monospace" text-anchor="middle" letter-spacing="0.06em">WRITE</text>

Rules: