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name: mermaid-diagramming type: standard depth: extended description: >- Creates Mermaid v11+ diagrams with ELK layout and YAML frontmatter. Covers 22 diagram types: flowchart, mindmap, block, sequence, journey, state, ER, class, requirement, pie, quadrant, sankey, xy, radar, gantt, treemap, C4, architecture, packet, timeline, gitgraph, kanban. Use when visualizing: logic flow, interactions, state machines, data models, charts, system architecture, or any diagram requiring theming, classDef styling, or accessibility.

[H1][MERMAID-DIAGRAMMING]

Dictum: Modern Mermaid syntax produces consistent, styled diagrams.

Mermaid v11+ diagram creation with frontmatter YAML, ELK layout, Dracula palette. 22 diagram types across 5 semantic categories.

Scope:

• Create: New diagrams from requirements. Select category, load syntax reference, apply styling.
• Reference: Syntax lookup for nodes, edges, relationships, charts, architecture.

Domain Navigation:

• [CONFIG] — Frontmatter YAML, ELK 5-phase layout, direction, limits. Load FIRST for all diagrams.
• [STYLING] — Theme presets, themeVariables, classDef, linkStyle, palette. Load for visual customization.
• [GRAPH] — Flowchart, mindmap, block. Load for: decision trees, hierarchies, system decomposition.
• [INTERACTION] — Sequence, journey. Load for: protocols, request-response, user experience.
• [MODELING] — State, ER, class, requirement. Load for: FSM, data models, OOP structure, traceability.
• [CHARTS] — Pie, quadrant, sankey, xy, radar, gantt, treemap. Load for: data visualization, project timelines.
• [ARCHITECTURE] — C4, architecture-beta, packet-beta, timeline, gitgraph, kanban. Load for: system views, infrastructure, network protocols, version control flow, project boards.

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[1][INSTRUCTIONS]

Dictum: Progressive loading optimizes context.

Required Tasks:

1. Read →global-config.md: Frontmatter YAML, ELK layout (required for ALL diagrams).
2. Read →styling.md: Theme, classDef, palette.
3. Select diagram category per §2 table, load corresponding syntax reference.

[REFERENCE]: →index.md — Complete file listing.

Guidance:

• Config First — Frontmatter YAML must precede diagram declaration. Mermaid parses config before nodes.
• ELK Layout — ELK provides comprehensive graph layout via five algorithmic phases: cycle breaking, layering, crossing minimization, node placement, edge routing.

Best-Practices:

• Load Sequence — global-config.md → styling.md → {category}.md → compose. Never skip configuration.
• Frontmatter Only — %%{init:...}%% directives deprecated v10.5.0. Use YAML frontmatter exclusively.

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[2][DIAGRAM_SELECTION]

Dictum: Category determines semantic structure.

[CATEGORY]	[TYPES]	[REFERENCE]
Graph	flowchart, mindmap, block	→graph.md
Interaction	sequence, journey	→interaction.md
Modeling	state, ER, class, requirement	→modeling.md
Charts	pie, quadrant, sankey, xy, radar, gantt, treemap	→charts.md
Architecture	C4, architecture, packet, timeline, gitgraph, kanban	→architecture.md

Type Headers:

[INDEX]	[TYPE]	[HEADER]	[DIR]	[CATEGORY]
[1]	Flowchart	flowchart LR	LR	Graph
[2]	Mindmap	mindmap	—	Graph
[3]	Block	block-beta	—	Graph
[4]	Sequence	sequenceDiagram	TB	Interaction
[5]	Journey	journey	—	Interaction
[6]	State	stateDiagram-v2	TB	Modeling
[7]	ER	erDiagram	LR	Modeling
[8]	Class	classDiagram	TB	Modeling
[9]	Requirement	requirementDiagram	—	Modeling
[10]	Pie	pie	—	Charts
[11]	Quadrant	quadrantChart	—	Charts
[12]	Sankey	sankey-beta	—	Charts
[13]	XY	xychart-beta	—	Charts
[14]	Radar	radar-beta	—	Charts
[15]	Gantt	gantt	—	Charts
[16]	Treemap	treemap-beta	—	Charts
[17]	C4	C4Context	—	Architecture
[18]	Architecture	architecture-beta	—	Architecture
[19]	Packet	packet-beta	—	Architecture
[20]	Timeline	timeline	—	Architecture
[21]	GitGraph	gitGraph	—	Architecture
[22]	Kanban	kanban	—	Architecture

Guidance:

• LR Default — Horizontal flow matches reading order. Sequence/State force TB implicitly.
• Beta Status — block, sankey, xy, radar, treemap, architecture, packet, kanban are beta; syntax may change.

Best-Practices:

• Category Match — Select by primary concern: flow→Graph, time→Interaction, structure→Modeling, data→Charts, system→Architecture.

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[3][VALIDATION]

Dictum: Gates prevent rendering failures.

[VERIFY] Before diagram creation:

• Frontmatter: valid YAML with config: key (before diagram declaration).
• Direction: LR for flowchart/ER, implicit TB for sequence/state.
• Reserved words avoided: end, default, subgraph, class in node IDs.
• classDef: placed at diagram end, after node definitions.
• Accessibility: accTitle/accDescr present after diagram type.

[REFERENCE]: →validation.md — Full validation checklists and anti-patterns.