---
name: ln-75-architecture-diagram-builder
description: "Creates evidence-backed current or target architecture diagrams when the diagram is the primary deliverable. Not for UI design, architecture audit, or invented structure."
---

# Architecture Diagram Builder

**Goal:** Create the smallest set of understandable, evidence-backed diagrams needed to communicate current or proposed architecture. Change only approved architecture documentation; do not invent relationships, perform visual product design, replace prose evidence, audit fitness, or edit implementation.

**Execution contract:** Treat the ordered checkbox workflow below as this skill's Definition of Done. Track every checkbox as `PENDING`, then resolve it to `PROVEN` with concrete evidence, `CLEARED` with evidence that its conditional trigger is absent, or `UNPROVEN`; reading, mentioning, delegating, skipping, or tool failure is not proof.
Before returning, resolve every `PENDING`, count only `PROVEN` and `CLEARED` items as complete, apply this skill's verdict, decision, and approval rules to every `UNPROVEN`, and prepend **Checklist: X/Y complete**<br>**Incomplete: None | section/item — reason; outcome impact; exact next action**; list every `UNPROVEN` item.

## Tool Routing

| Need | Preferred capability | Fallback |
|---|---|---|
| Architecture evidence | Repository files, runtime wiring, IaC, contracts, and approved artifacts | User-provided model with `UNVERIFIED` labels |
| Relationship tracing | Language intelligence, dependency tools, and focused search | Direct inspection of producers, consumers, and registrations |
| Diagram format | Existing repository convention and renderer | Mermaid in Markdown, then plain ASCII |
| Syntax verification | Repository renderer, parser, or preview | Manual fence, identifier, and relationship inspection |
| Document mutation | Minimal patch to approved diagram artifacts | Return `BLOCKED` if path or evidence boundary is unsafe |

Diagrams communicate a model; executable behavior remains authoritative for current state. Keep current, target, and transition views visibly distinct.

## Artifact Rules

- Reuse an existing diagram convention or use `docs/architecture/diagrams/<view>.md`.
- Prefer Markdown with Mermaid for text-reviewable source; use ASCII when Mermaid is unsupported.
- Choose only views that answer a named audience question.
- For static structure, start with system context and container views; add component depth only when it changes a decision.
- Use sequence or dynamic views for critical runtime interactions and failure paths.
- Use data-flow views for stores, sensitive data, trust boundaries, and transformations.
- Use deployment views for runtime nodes, regions, networks, scaling, and failover.
- Give every diagram a title, scope, audience, legend, element descriptions, and labeled relationships.
- Keep diagram source reviewable in version control.
- Split views when one diagram needs multiple unrelated stories.
- Never use color as the only carrier of meaning.
- Use stable element identifiers and concise display labels so revisions produce reviewable diffs.
- Keep detailed evidence beside the diagram rather than crowding nodes and relationships.
- Preserve an understandable existing notation; introduce a new notation only when it answers the audience question better.

## Checklist

### 1. Establish the Diagram Contract

- [ ] Resolve audience, question, current or target state, scope, approved destination, and required notation.
- [ ] Read repository instructions, relevant architecture artifacts, and existing diagram conventions.
- [ ] Select the minimum useful view or views; reject diagrams that add no relationship clarity.
- [ ] Define the evidence boundary and label user-supplied or proposed elements separately.
- [ ] Keep the run read-only except for approved architecture diagram documentation.

### 2. Build the Architecture Model

- [ ] Identify people, software systems, deployable containers, components, stores, queues, and external dependencies relevant to the question.
- [ ] Record responsibility, type, technology when decision-relevant, owner when known, and current/target status for each element.
- [ ] Resolve relationship direction, label, protocol or data, synchronicity, and trust or network boundary where relevant.
- [ ] Trace runtime discovery and registration before including current-state routes, handlers, jobs, plugins, or consumers.
- [ ] Mark uncertain elements or relationships `UNKNOWN` rather than completing the picture aesthetically.

### 3. Select and Draw Views

- [ ] Create a system-context view when readers need system scope and external actors.
- [ ] Create a container or deployment view when readers need responsibilities, deployability, stores, or operational topology.
- [ ] Create a component view only for a complex area whose internal boundaries change understanding.
- [ ] Create sequence or dynamic views for critical success, failure, retry, timeout, recovery, or migration interactions.
- [ ] Create data-flow or trust-boundary views when security, privacy, residency, or system-of-record questions require them.
- [ ] Avoid mixing abstraction levels in one view unless the exception is explicit and necessary.

### 4. Make the Diagram Self-Describing

- [ ] Add title, diagram type, scope, current/target marker, intended audience, and observation or proposal date.
- [ ] Add a legend for shapes, colors, line styles, abbreviations, and uncertainty markers.
- [ ] Label every relationship with intent or data; avoid generic arrows and unexplained acronyms.
- [ ] Keep names consistent with code, contracts, and shared architecture documents.
- [ ] Add compact evidence notes or links sufficient to trace current-state claims.

### 5. Verify and Report

- [ ] Validate syntax with the repository renderer or perform a complete manual syntax inspection.
- [ ] Check readability at normal rendering size and split overloaded views rather than shrinking labels.
- [ ] Verify each current-state element and relationship against repository evidence.
- [ ] Confirm no UI design, audit verdict, code, tests, or external state changed.
- [ ] Use `READY` when diagrams are valid, scoped, and evidenced; use `INCONCLUSIVE` when material relationships remain unknown; use `BLOCKED` when scope, evidence, format, or destination prevents a trustworthy diagram.

## Output Contract

```markdown
# Architecture Diagrams

**Verdict:** READY | INCONCLUSIVE | BLOCKED
**Artifacts:** paths

## Views created or updated
| View | State | Audience question | Evidence basis |
|---|---|---|---|

## Verification
- Syntax or render check
- Current-state relationship checks

## Unknowns and residual risks
Only missing relationships or rendering limits that affect interpretation.
```