---
name: ln-75-architecture-diagram-builder
description: "Creates current or target architecture diagrams as the primary deliverable. Not for UI design, architecture audits, 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:** The ordered checkboxes are the Definition of Done. Track every item internally as `PENDING`, `PROVEN` with concrete evidence, `CLEARED` with evidence that its condition is absent, or `UNPROVEN` with a gap; reading, delegation, or tool failure is not proof. Reconcile items after each section. Before returning, resolve all `PENDING` and count only `PROVEN` and `CLEARED`; apply the skill's verdict and approval rules to every gap.
Preserve user intent, scope, and existing authorization. Continue authorized work; ask only for consequential unresolved choices or required external approval. Scale depth to material risk without silently skipping checks. Preserve dependency and safety ordering; otherwise choose the verification method appropriate to each obligation.

## 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.
- For static structure, choose the context, container, or component level that answers the requested question; do not create prerequisite overview diagrams when existing context suffices.
- 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 relevant people, systems, applications/data stores (C4 containers when using C4), components, queues, and external dependencies; distinguish logical containers from OS/container-runtime deployment units.
- [ ] 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 for responsibilities, deployability, stores, or operational topology; include nodes, regions, networks, scaling, and failover when relevant to the audience question.
- [ ] 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.
- [ ] Inspect rendered readability when a preview is available and split overloaded views rather than shrinking labels. Without a renderer, record visual readability as `UNPROVEN`; manual syntax inspection is not render proof.
- [ ] Verify current-state elements and relationships against implementation evidence, and target-state elements against the declared proposal or explicitly labelled assumptions.
- [ ] 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.

## Self-Check

- [ ] **Reconcile before returning.** Check item-level evidence, requirement coverage, contradictions, scope, verdict, and applicable cleanup. Correct the report or authorized artifacts. Reuse valid evidence; do not automatically rescan the repository or rerun successful commands. Repeat checks only for relevant changes, failures, or unresolved evidence. Disclose remaining gaps.

## Output Contract

Report in the user's language, in this order; retain all five fields and state each fact once. Small results may use one line per field; omit empty tables and do not copy linked artifacts:

1. **Result:** Skill-specific verdict and supported outcome.
2. **Scope:** Reviewed/changed scope, exclusions, baseline, and material assumptions.
3. **Evidence:** Skill-specific fields below; distinguish facts, inferences, and unverified claims. Link artifacts; use tables when useful.
4. **Verification:** Checks/results, unavailable evidence, and applicable cleanup/external state.
5. **Completion:** `Checklist: X/Y complete`; `Incomplete: None` or each `UNPROVEN` item's reason, outcome impact, and exact next action; residual risks and required decisions.

**Skill-specific evidence:** Artifact paths; each view’s current/target state, audience question, and evidence basis. Report syntax/render verification and current-state relationship checks, unknown relationships, and rendering limits that affect interpretation.