Generates and validates Mermaid diagrams with YAML frontmatter, ELK layout, Dracula theme tokens, and a bundled render, graph-logic, and SVG-geometry validator. Owns diagram methodology — when to diagram, node and edge selection, per-type construction, logical soundness — the archetype template catalog from architecture spine to weighted decomposition, the concept-to-diagram map that turns state machines, dispatch topologies, dependency graphs, protocol seams, and chronologies into the right fence, and the embedding contract for diagrams inside markdown docs and single-file HTML artifacts. Use when authoring, editing, or fixing any mermaid fence, choosing a diagram type, embedding a rendered diagram in a page, or whenever a task asks to draw, diagram, map, or visualize a system, flow, state machine, sequence exchange, schema, dependency structure, schedule, hierarchy, or workflow board — even when mermaid is never named — distinct from quantitative dataviz marks and interactive HTML pages.
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Generates and validates Mermaid diagrams with YAML frontmatter, ELK layout, Dracula theme tokens, and a bundled render, graph-logic, and SVG-geometry validator. Owns diagram methodology — when to diagram, node and edge selection, per-type construction, logical soundness — the archetype template catalog from architecture spine to weighted decomposition, the concept-to-diagram map that turns state machines, dispatch topologies, dependency graphs, protocol seams, and chronologies into the right fence, and the embedding contract for diagrams inside markdown docs and single-file HTML artifacts. Use when authoring, editing, or fixing any mermaid fence, choosing a diagram type, embedding a rendered diagram in a page, or whenever a task asks to draw, diagram, map, or visualize a system, flow, state machine, sequence exchange, schema, dependency structure, schedule, hierarchy, or workflow board — even when mermaid is never named — distinct from quantitative dataviz marks and interactive HTML pages.
[MERMAID_DIAGRAMMING]
Every committed diagram answers one written question, instantiates one catalog archetype or admitted type, opens with frontmatter carrying its type's Dracula subset, and ships only after the validator and the soundness audit pass. Reasoning discipline and engine surface load on demand through the reference routes below.
[09]-EMBEDDING: fence law in markdown hosts, inline-SVG law in single-file HTML, export surfaces, source-beside-render
[02]-[QUESTION]
A diagram earns its fence only when the reader traces a relation across more marks than a clause holds: three or more nodes with at least one branch, cycle, or crossing relation. Below that threshold prose owns the fact, and one diagram owns one question — a diagram needing two legends is two diagrams. Full authoring discipline is references/methodology.md, and per-type mark law is references/construction.md. A subject that arrives as raw material — code, prose, a plan, an argument — with no written question resolves its shape first through references/concept-mapping.md.
[03]-[CATALOG]
Select the archetype by intent, copy its template, and refill — a catalog template is self-sufficient, carrying its archetype's construction law in its own prose. An intent outside the catalog selects its type through the methodology decision table and the extended registry, under the same frontmatter, theming, and validation law. A split move partitions a subject the moment a second question appears, and a required legend is itself a split signal.
A diagram is not done until its fence passes both stages: graph-logic checks over the source, then a render whose proof is an actual SVG artifact, never a zero exit alone.
uv run scripts/validate_mermaid.py <file.md ...>
Each fence emits file:line: STATUS check detail rows with check kinds render, legibility, frontmatter, contract, logic, export, proof, setup, read, and collect; --json emits identical-key NDJSON for tooling. Contract, logic, legibility, and frontmatter rows fire only on findings — a clean fence prints its render row alone, and silence from a check is a pass. Graph-logic analysis covers the families the validator implements; any family outside that set emits a logic-unimplemented warn instead of silent approval. A logic failure blocks on a structural break the graph cannot resolve, and a logic warn demands a split or a stated reason; the emitted row names the exact condition. Contract warnings enforce the theming, styling, and config canon per family. --no-render runs the logic and frontmatter checks alone for a fast loop; the process exits nonzero when any fence fails. A render failure splits syntax from environment, so a missing browser never masquerades as a broken diagram. After a fence renders, the legibility pass parses the SVG geometry for the graph families (flowchart, state, ER, class) and emits node-overlap (fail), edge-over-node, and edge-crossing-pairs:N rows — N counts crossing edge pairs, a lower bound, computed from node bounding boxes and edge routing rather than eyeballed; sequence, gantt, and quantitative families carry inherent crossings and are exempt.
uv run scripts/check_canon.py <file.md ...> runs the canon checker beside the validator — a render-free, table-driven enforcement of the theming, styling, and config canon per family emitting the same file:line: STATUS canon rule detail row shape with --json NDJSON and a nonzero exit on any fail. --explain <rule-id> prints a finding's canon sentence and owning reference.
Renderer resolution walks the workspace first — node_modules/.bin/mmdc from any cwd ancestor, then PATH mmdc, --renderer CMD overriding both. Each render binds the pinned Chromium through the generated puppeteer-config executablePath, so the real Google Chrome app never launches. A fence the resolved renderer rejects re-proves through the pinned release renderer the validator invokes over the pnpm dlx cache, verified by the emitted SVG — so a lagging toolchain never masquerades as broken syntax; the passing row lands as rendered-release:, and a fence the pinned renderer also rejects stays a real syntax failure. --export DIR writes every passing fence as an embed-ready SVG — unique root id, aria title and description preserved, Dracula canvas baked — the mechanical arm of the embedding contract. --proof rasterizes each rendered SVG browserlessly through resvg into a per-run ephemeral dir cleaned on exit — --keep preserves it and prints proof-dir: — with mmdc's own PNG as the fallback where a family still carries foreignObject labels; a proof failure lands as a typed proof row, never a silent pass.
[05]-[CONTRACT]
Frontmatter opens every fence body above the diagram header, carrying theme: base and look: classic with the Dracula subset its type consumes; a fence opening with %%{init:...}%% converts to frontmatter.
Local style law replaces that subset on packet, C4 element surfaces, and host-themed docs.
Every themed fence renders flat by construction: look: classic, useGradient: false, dropShadow: "none", and the family themeCSS filter belt.
Flat construction kills gradient borders and node halos on every host, including one that initializes the neo look.
Theming's border canon owns the lock, the weight ladder, and the Lavender container boundary.
accTitle and accDescr follow the header on every committed diagram, stating the encoded relation so the exported SVG reads outside its source.
block, mindmap, sankey, and venn refuse the directives, ishikawa mis-handles them as nodes, and kanban as columns, so their relation sentence sits beside the fence; timeline and eventmodeling parse them but emit nothing into the SVG, so their relation sentence rides beside the fence too.
Node and edge labels carry concept names, never mechanism detail — the owning page carries the bytes.
Semantic node classes and edge rails ride the canonical Dracula classDef set with its ruled translucent accent fills; an ad-hoc hex is a defect.
Flowchart edge rails bind insertion-stably through eN@ edge-id classes; positional linkStyle indices drift on every insertion.
One animate: true edge per diagram may mark a genuinely live, streaming, or hot path with its semantic stated; unmotivated animation is a defect, and a raster export stills it.
Theming's ruled mono stack and the recessed #21222C label backing reach every themed fence, and no canvas text renders below 12px through the micro-scale themeCSS stamps.
[06]-[LEGIBILITY]
Legibility bounds a diagram, not syntax capacity. A rendered diagram ships only after the validator's geometry rows clear and the reviewer clears what geometry cannot — untruncated labels, reading-order orientation, light/dark host contrast, type matching subject. A faulted fence converges on its own source across at most five render-inspect-edit rounds; each correction is a minimal text edit to the fence itself, never a sibling file.
[07]-[REPO_INTEGRATION]
When the host repo declares a docs gate, that gate consumes scripts/validate_mermaid.py --json; the bundled script is the same engine everywhere else.
