# Architecture — Chat Switchboard v0.9

## Deployment Modes

Three Docker images support different deployment scenarios:

| Image | Dockerfile | Contents | Use Case |
|-------|-----------|----------|----------|
| **Unified** | `Dockerfile` | nginx + Go backend | Dev, docker-compose, single-node |
| **Backend** | `server/Dockerfile` | Go binary only | K8s — scale API independently |
| **Frontend** | `Dockerfile.frontend` | nginx + static files | K8s — scale FE independently |

**Unified** bundles everything in one container. Nginx serves static files and proxies `/api/*` and `/ws` to the Go backend running on `:8080`. Good for development and small deployments.

**Split (Backend + Frontend)** for production K8s: Ingress routes `/api/*` and `/ws` to the backend Service, everything else to the frontend Service. The frontend entrypoint (`docker-entrypoint-fe.sh`) handles `BASE_PATH` injection into `index.html` and dynamic nginx config generation at startup. Supports branding volume mounts at `/branding/`.

```
                    ┌─────────────────────────┐
                    │  Ingress / Traefik       │
                    │  ├─ /api/* → be-svc:8080 │
                    │  ├─ /ws   → be-svc:8080  │
                    │  └─ /*    → fe-svc:80    │
                    └─────────────────────────┘
                         │              │
              ┌──────────▼──┐   ┌───────▼────────┐
              │  Backend    │   │  Frontend       │
              │  (Go :8080) │   │  (nginx :80)    │
              │  replicas:N │   │  replicas:M     │
              └──────┬──────┘   └────────────────┘
                     │
              ┌──────▼──────┐
              │ PostgreSQL  │
              └─────────────┘
```

## Design Principles

1. **Persona-as-Trust-Boundary**: A persona (model + config + prompt) is the unit of access control. Users interact with personas, not raw provider configs. Admins control which models are visible; team admins control which personas their team can use.

2. **Roles vs Teams**: Clean separation between vertical permissions (Roles: admin, user) and horizontal visibility (Teams: organizational units). A user's role determines what they can *do*; their team membership determines what they can *see*.

3. **Store Layer**: All database access goes through typed Go interfaces (`store.Stores`). Handlers never write raw SQL. This enables future portability (SQLite for dev, Postgres for prod) and testability (mock stores).

4. **Scope Model**: Provider configs, personas, and model settings all use a three-value `scope` column: `global` (admin-managed, visible to all), `team` (team-admin-managed, visible to team), `personal` (user-managed, visible to owner). The `owner_id` column points to the owning user or team depending on scope.

5. **Capabilities Resolution**: Model capabilities (vision, tool calling, thinking, context window) are resolved through a priority chain: catalog DB (provider API sync, per-provider authoritative) → heuristic inference (regex patterns on model ID). No static model table — the same model can have different capabilities on different providers. The catalog is populated by auto-fetch on provider creation and manual refresh.

6. **Channels as Execution Context**: Channels are the universal container for conversation state — messages, tool activity, notes, and artifacts all hang off a channel. Today channels are single-user direct chats. The architecture anticipates multi-participant channels (team members, anonymous visitors, AI personas) for workflow execution, without requiring changes to the message tree, tool framework, or streaming infrastructure.

## Workflow Architecture (Future — v0.21.0+)

The platform's existing primitives (teams, personas, channels, tools, notes)
compose into a workflow engine where the channel is the execution context
that moves through defined stages.

### Conceptual Model

```
Team
 └─ Workflow (team-admin defined)
      ├─ name, description
      ├─ entry conditions (public link, team-internal, API trigger)
      └─ Stages[]
           ├─ persona_id (which AI drives this stage)
           ├─ assignment_team_id (who can be assigned)
           ├─ form_template (structured note schema, optional)
           └─ transitions[] (conditions → next stage)

Channel (workflow instance)
 ├─ workflow_id + current_stage
 ├─ participants[]
 │    ├─ anonymous visitor (mTLS fingerprint / session token)
 │    ├─ AI persona (per-stage, from workflow definition)
 │    └─ assigned team member (claimed or auto-routed)
 ├─ messages (existing tree structure)
 ├─ notes (channel-scoped artifacts, intake forms)
 └─ tool activity (existing execution framework)
```

### How Existing Primitives Map

| Existing Primitive | Workflow Role |
|-------------------|---------------|
| **Persona** (system prompt + model) | Drives a workflow stage — the AI knows what to collect, when to route |
| **Team** (members + roles) | Owns the workflow definition; members are assignable to channels |
| **Channel** (messages + tree) | Execution instance of a workflow; full conversation history |
| **Notes + Tools** | Structured data collection; the persona's system prompt *is* the form definition, the note *is* the filled form |
| **EventBus + WebSocket** | Real-time notifications for assignment, stage transitions, new messages |

### Design Constraints for Current Development

These invariants keep the workflow path open without building it prematurely:

- **Channels**: Don't assume single-owner. If touching channel queries, keep
  room for `team_id`, `type` (beyond `direct`), and multi-participant access
  patterns alongside `user_id`.
- **Notes**: Currently user-scoped. Future channel-scoped notes (attached to
  a conversation, not a personal notebook) need a `channel_id` FK option.
- **Personas**: Already team-scoped. Don't couple to "user picks from dropdown"
  — a workflow stage references a persona programmatically.
- **Tool ExecutionContext**: Already carries `UserID` + `ChannelID`. Will need
  `TeamID` and `WorkflowID` — the struct is easily extended.
- **Auth**: mTLS anonymous users need identity to participate in channels.
  Lightest version: a `participants` table that can reference a `user_id` or
  an opaque session identifier (cert fingerprint). Don't assume every channel
  participant has a row in `users`.

## Package Structure

```
server/
├── main.go                    # Wiring: stores → handlers → routes
├── config/config.go           # Env-based configuration
├── database/
│   ├── database.go            # Connection management
│   ├── migrate.go             # Auto-migration on startup
│   └── migrations/
│       └── 001_v09_schema.sql # Consolidated schema
├── store/
│   ├── interfaces.go          # Store interfaces + shared types
│   └── postgres/              # Postgres implementations
│       ├── stores.go          # NewStores() constructor
│       ├── provider.go        # ProviderStore
│       ├── catalog.go         # CatalogStore
│       ├── persona.go         # PersonaStore
│       ├── user.go            # UserStore
│       ├── team.go            # TeamStore
│       ├── policy.go          # PolicyStore
│       ├── audit.go           # AuditStore
│       └── ...
├── models/models.go           # Shared domain types
├── capabilities/
│   ├── intrinsic.go           # Heuristic detection + resolution
│   └── resolver.go            # ModelsForUser() unified resolver
├── handlers/                  # HTTP handlers (Gin)
│   ├── auth.go                # Login, register, refresh, logout
│   ├── admin.go               # User/config/model management
│   ├── channels.go            # Channel CRUD
│   ├── messages.go            # Message CRUD + forking
│   ├── completion.go          # Chat completions (SSE streaming)
│   ├── capabilities.go        # Model list + ResolveModelCaps
│   ├── presets.go             # Persona CRUD (all scopes)
│   ├── apiconfigs.go          # User provider config CRUD (BYOK)
│   ├── teams.go               # Team management
│   └── ...
├── providers/                 # LLM provider adapters
│   ├── provider.go            # Provider interface
│   ├── anthropic.go
│   ├── openai.go
│   ├── openrouter.go
│   └── venice.go
├── middleware/                 # Auth, admin, CORS, rate limiting
├── events/                    # EventBus + WebSocket hub
└── tools/                     # Built-in tool definitions (notes)
```

## Store Layer Pattern

Every store follows the same pattern:

```go
// Interface in store/interfaces.go
type FooStore interface {
    Create(ctx context.Context, f *models.Foo) error
    GetByID(ctx context.Context, id string) (*models.Foo, error)
    Update(ctx context.Context, id string, patch models.FooPatch) error
    Delete(ctx context.Context, id string) error
    List(ctx context.Context, opts ListOptions) ([]models.Foo, int, error)
}

// Implementation in store/postgres/foo.go
type fooStore struct{ db *sql.DB }
func (s *fooStore) Create(ctx context.Context, f *models.Foo) error { ... }
```

Handlers receive `store.Stores` (a bundle of all store interfaces):

```go
type AdminHandler struct { stores store.Stores }

func (h *AdminHandler) CreateUser(c *gin.Context) {
    // ...
    err := h.stores.Users.Create(c.Request.Context(), user)
}
```

## Capabilities Resolution Chain

When the system needs to know what a model can do (vision? tools? thinking?):

```
1. model_catalog DB (exact match: model_id + provider_config_id)
   ↓ miss
2. model_catalog DB (any provider: same model_id)
   ↓ miss
3. Heuristic inference (name-based: "gpt-4-vision" → vision=true)
```

The `capabilities.ModelsForUser()` function combines catalog entries, team personas, and user preferences into a single unified model list for the frontend.

## Scope / Ownership Model

```
scope='global'   → owner_id=NULL     → Admin-managed, visible to all
scope='team'     → owner_id=team.id  → Team-admin-managed, visible to team
scope='personal' → owner_id=user.id  → User-managed, visible to owner
```

Used by: `provider_configs`, `personas`, `model_catalog` (visibility column adds `enabled`/`disabled`/`team` states on top).

## Schema Migration

Single consolidated migration (`001_v09_schema.sql`) replaces the previous 21 incremental migrations. The Go backend auto-migrates on startup:

1. Creates `schema_migrations` table if absent
2. Checks which migration files have been applied
3. Applies any new `.sql` files in order

## Frontend Architecture

Vanilla JavaScript, no build step. Five files with clear responsibilities:

| File | Role |
|------|------|
| `api.js` | HTTP client with token refresh. All backend calls. |
| `app.js` | Application state machine. Business logic. |
| `ui.js` | DOM rendering. All `document.createElement` calls. |
| `events.js` | Labeled event bus with WebSocket bridge. |
| `debug.js` | Admin debug panel (model list, stats, config). |

Communication: `app.js` calls `API.*` methods, updates state, then calls `UI.*` methods to render. `events.js` handles real-time updates via WebSocket. No framework, no virtual DOM, no reactive bindings.

## Security Model

- **Auth**: JWT access tokens (short-lived) + refresh tokens (DB-stored, revocable)
- **Admin Bootstrap**: `SWITCHBOARD_ADMIN_USERNAME`/`PASSWORD` env vars create/update admin on every startup (K8s secret pattern)
- **API Key Storage**: Provider API keys stored in `api_key_enc` column (TODO: at-rest encryption)
- **Policies**: Boolean flags in `global_settings` table control registration, BYOK, team providers, etc.
- **Audit**: All admin operations logged to `audit_log` with actor, action, resource type/ID, and diff
- **Banner**: Environment classification banner configurable via admin settings (text, color, position)
- **CORS**: Configurable allowed origins via env var
- **No sensitive terminology**: Banner system avoids classification-related terms for security compliance

## Backward Compatibility

v0.9 maintains backward-compatible API routes:

| Old Route | New Handler | Notes |
|-----------|-------------|-------|
| `/api/v1/presets` | PersonaHandler | Returns both `personas` and `presets` keys |
| `/api/v1/api-configs` | ProviderConfigHandler | Unchanged route, new implementation |
| `/api/v1/models` | ModelHandler.ListEnabledModels | Alias for `/models/enabled` |

JSON field rename: `api_config_id` → `provider_config_id` in channel and completion request/response bodies. Frontend updated to match.