Create Arch Docs

Create Architecture Documentation

Generate architecture documentation by analyzing the codebase, then producing C4 diagrams, Architecture Decision Records, and system context documentation.

Instructions

1. Codebase Discovery

Before documenting anything, read the codebase to understand the architecture:

• Read CLAUDE.md, README.md, and any existing architecture docs.
• Examine the directory structure, entry points, and module organization.
• Identify the tech stack: languages, frameworks, databases, message brokers, external services.
• Trace key request/data flows through the system.
• Read configuration files to understand deployment targets and infrastructure.
• Identify architectural patterns in use (MVC, microservices, event-driven, monolith, etc.).

2. System Context Documentation

Create a high-level system context diagram and description:

• Document what the system does and who uses it (users, external systems, APIs).
• Define system boundaries — what is in scope vs. external.
• Map external integrations and dependencies.
• Use the mermaid skill to generate a C4 Context diagram.

3. Container and Service Architecture

Document the major deployable units:

• Map containers/services, their responsibilities, and communication patterns (REST, gRPC, events, etc.).
• Document deployment architecture and infrastructure (cloud services, containers, serverless).
• Define API contracts between services.
• Document data persistence: databases, caches, file storage, and what each stores.
• Use the mermaid skill to generate a C4 Container diagram.

4. Component and Module Documentation

Document internal structure of key containers:

• Create component diagrams for the most important modules.
• Document internal module relationships and dependency direction.
• Describe design patterns used and why (repository pattern, CQRS, pub/sub, etc.).
• Document the package/folder organization and its rationale.
• Use the mermaid skill to generate component-level diagrams.

5. Data Architecture

• Document data models and key database schemas.
• Create data flow diagrams showing how data moves through the system.
• Document data storage strategies (relational, document, key-value, etc.) and why each was chosen.
• Note any data synchronization, replication, or migration patterns.

6. Architecture Decision Records (ADRs)

Create ADRs for significant architectural decisions found in the codebase:

• Use the format: Title, Status, Context, Decision, Consequences.
• Document trade-offs and alternatives that were likely considered.
• Cover decisions like: framework choice, database selection, API style, authentication approach, deployment strategy.
• Place ADRs in docs/adr/ with sequential numbering (e.g., 0001-use-postgresql.md).

7. Quality Attributes and Cross-Cutting Concerns

Document how the system handles:

• Performance — Caching strategies, query optimization, scaling approach.
• Security — Authentication/authorization flows, trust boundaries, data protection.
• Reliability — Error handling patterns, retry logic, circuit breakers.
• Observability — Logging, monitoring, health checks, tracing.

Output

Produce the following files:

• docs/architecture/README.md — Overview and index linking to all architecture docs.
• docs/architecture/system-context.md — System context with C4 Level 1 diagram.
• docs/architecture/containers.md — Container architecture with C4 Level 2 diagram.
• docs/architecture/components.md — Component details with C4 Level 3 diagrams.
• docs/architecture/data-architecture.md — Data models, flows, and storage.
• docs/architecture/quality-attributes.md — Cross-cutting concerns.
• docs/adr/0001-*.md (one per decision) — Architecture Decision Records.

All diagrams should use Mermaid syntax for version-control-friendly, renderable documentation.