Hexagonal DDD

Redshank uses a DDD-Lite hexagonal architecture. The key invariant is the dependency rule: inner rings know nothing about outer rings.

          ┌─────────────────────────────────────┐
          │           Adapters (outer)           │
          │  ┌───────────────────────────────┐  │
          │  │      Application layer        │  │
          │  │  ┌─────────────────────────┐  │  │
          │  │  │    Domain (inner)        │  │  │
          │  │  │  Types, events, rules    │  │  │
          │  │  └─────────────────────────┘  │  │
          │  │  Commands / Queries / Services │  │
          │  └───────────────────────────────┘  │
          │  Providers / Tools / Persistence     │
          └─────────────────────────────────────┘

Domain layer (src/domain/)

Pure Rust structs and enums. No async, no tokio, no I/O of any kind.

• agent.rs — AgentSession aggregate root, AgentConfig, ProviderKind
• auth.rs — AuthContext, Role, Permission, SecurityPolicy
• credentials.rs — CredentialBundle, resolution order
• errors.rs — DomainError enum (all thiserror)
• events.rs — DomainEvent variants
• session.rs — session value objects
• settings.rs — PersistentSettings
• wiki.rs — WikiEntry, WikiEntryId

Ports layer (src/ports/)

Trait interfaces that the domain and application layers call. Adapters implement these traits; the domain never sees the implementations.

• ModelProvider — LLM completions with streaming
• SessionStore — session persistence (CQRS-aware)
• WikiStore — wiki entry persistence
• ToolDispatcher — tool invocation
• ReplayLog — JSONL delta-encoded call log
• FetcherPort — data fetcher abstraction