diagram-design

# 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`](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`](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`](references/onboarding.md); for **(f)** follow [`references/profiles.md`](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`](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`](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](references/type-architecture.md) |
| Legacy IT landscape grouped by phase/department; documents the *before* state in modernization proposals | **IT current-state** | [type-it-state.md](references/type-it-state.md) |
| Decision logic with branches | **Flowchart** | [type-flowchart.md](references/type-flowchart.md) |
| Time-ordered messages between actors | **Sequence** | [type-sequence.md](references/type-sequence.md) |
| States + transitions + guards | **State machine** | [type-state.md](references/type-state.md) |
| Entities + fields + relationships | **ER / data model** | [type-er.md](references/type-er.md) |
| Events positioned in time | **Timeline** | [type-timeline.md](references/type-timeline.md) |
| Cross-functional process with handoffs | **Swimlane** | [type-swimlane.md](references/type-swimlane.md) |
| Two-axis positioning / prioritization | **Quadrant** | [type-quadrant.md](references/type-quadrant.md) |
| Multiple entities scored across 3–5 quantitative criteria | **Radar / Sp