/coco-diagram

name: coco-diagram
description: "Use for architecture, current-state, process, data-flow, medallion, or DP diagrams, including redrawing .drawio and Mermaid sources. Creates branded flowchart, sequence, ER, org, timeline, and chart visuals as standalone HTML/SVG/PNG."
license: MIT
domain: design
metadata:
  version: "2.3.2"

CoCo Diagram

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

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

---

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.

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 `#BE185D` coco-magenta), **pause and ask the user**:

> *"This is your first Schematic in this project. The style guide is still at the default (neutral white-smoke + coco-magenta). 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."*

Then branch:

• **(a)** → follow [`references/onboarding.md § URL`](references/onboarding.md) to fetch the site, extract palette + fonts, propose a diff, and write `style-guide.md`.
• **(b)** → follow [`references/onboarding.md § Skill`](references/onboarding.md) — ask which skill, read its SKILL.md / CSS / token files, map to semantic roles, propose diff.
• **(c)** → follow [`references/onboarding.md § Folder`](references/onboarding.md) — ask for the path, glob for CSS/JSON/MD token files, map to semantic roles, propose diff.
• **(d)** → accept the user's tokens and write them into `style-guide.md` under a new "Custom tokens" section.
• **(e)** → proceed; optionally remind the user they can run onboarding later.

**Once the style guide has been customized** (or the user explicitly opted for default), skip this gate on subsequent runs. A simple way to detect customization: if the `accent` value in `style-guide.md` differs from `#BE185D`, assume custom.

---

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.
• Accent 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.

---

2. When to Use

Use for any of the 27 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.

---

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 (27)

| 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 / prioritiza