Merge pull request 'Merge branch 'develop-pdca' into develop' (#20) from develop-pdca into develop

Reviewed-on: #20

.env.sample

@@ -94,6 +94,17 @@ QBITTORRENT_INSTANCES=[{"name":"main","url":"https://qbittorrent.example.com","u
 # QBITTORRENT_USERNAME=admin
 # QBITTORRENT_PASSWORD=your-password
 
+# =============================================================================
+# RTORRENT_INSTANCES (JSON Array)
+# The url MUST include the full XML-RPC endpoint path.
+# Standard/self-hosted installs: .../RPC2
+# whatbox.ca users: .../xmlrpc
+# Other installations may use different custom paths.
+# Example:
+RTORRENT_INSTANCES=[{"name":"main","url":"http://rtorrent.local:8080/RPC2","username":"rtorrent","password":"rtorrent"}]
+# For whatbox.ca:
+# RTORRENT_INSTANCES=[{"name":"whatbox","url":"https://user.whatbox.ca/xmlrpc","username":"user","password":"pass"}]
+
 # =============================================================================
 # SONARR INSTANCES (JSON Array Format)
 # Add one or more Sonarr instances as a single-line JSON array

README.md

@@ -7,7 +7,7 @@
 ## What It Does
 
 sofarr connects to your media stack and shows you a personalized view of:
-- **Active Downloads** - See what's currently downloading from Usenet (SABnzbd) and BitTorrent (qBittorrent)
+- **Active Downloads** - See what's currently downloading from Usenet (SABnzbd) and BitTorrent (qBittorrent, Transmission, rTorrent)
 - **Progress Tracking** - Real-time progress bars with speed, ETA, and completion estimates
 - **Recently Completed** - History tab showing imported and failed downloads from Sonarr/Radarr with deduplication and upgrade-awareness
 - **User Matching** - Downloads are matched to you based on tags in Sonarr/Radarr
@@ -21,7 +21,9 @@ sofarr connects to your media stack and shows you a personalized view of:
 ┌─────────────┐     ┌──────────────┐     ┌─────────────────────────────┐
 │   Browser   │────▶│   sofarr     │────▶│  SABnzbd (Usenet downloads)   │
 │   (User)    │◀────│   Server     │     │  qBittorrent (Torrents)       │
-└─────────────┘     └──────────────┘     │  Sonarr (TV management)       │
+└─────────────┘     └──────────────┘     │  Transmission (Torrents)      │
+                       │                 │  rTorrent (Torrents)          │
+                       │                 │  Sonarr (TV management)       │
                        │                 │  Radarr (Movie management)    │
                        │                 │  Emby (User authentication)   │
                        ▼                 └─────────────────────────────┘
@@ -37,7 +39,7 @@ sofarr connects to your media stack and shows you a personalized view of:
 2. **Tag-Based Matching**:
    - Your media in Sonarr/Radarr is tagged with your username (e.g., "gordon")
    - sofarr checks Sonarr/Radarr activity to find items tagged with your name
-   - Downloads (from SABnzbd/qBittorrent) are matched by title to that activity
+   - Downloads (from SABnzbd, qBittorrent, Transmission, or rTorrent) are matched by title to that activity
    - Only your downloads appear on your dashboard
 
 ### Multi-Instance Support
@@ -53,7 +55,7 @@ SONARR_INSTANCES=[{"name":"main","url":"...","apiKey":"..."}]
 ## Prerequisites
 
 - **Docker** (recommended), or Node.js (v22+) for manual installation
-- At least one of: SABnzbd or qBittorrent
+- At least one download client: SABnzbd, qBittorrent, Transmission, or rTorrent
 - Sonarr (optional, for TV tracking)
 - Radarr (optional, for movie tracking)
 - Emby (for user authentication)
@@ -108,6 +110,8 @@ docker run -d \
   -e RADARR_INSTANCES='[{"name":"main","url":"http://radarr:7878","apiKey":"your-key"}]' \
   -e SABNZBD_INSTANCES='[{"name":"main","url":"http://sabnzbd:8080","apiKey":"your-key"}]' \
   -e QBITTORRENT_INSTANCES='[{"name":"main","url":"http://qbit:8080","username":"admin","password":"pass"}]' \
+  -e TRANSMISSION_INSTANCES='[{"name":"main","url":"http://transmission:9091","username":"admin","password":"pass"}]' \
+  -e RTORRENT_INSTANCES='[{"name":"main","url":"http://rtorrent:8080/RPC2","username":"rtorrent","password":"rtorrent"}]' \
   -e LOG_LEVEL=info \
   -e POLL_INTERVAL=5000 \
   docker.i3omb.com/sofarr:latest
@@ -131,6 +135,8 @@ services:
       - RADARR_INSTANCES=[{"name":"main","url":"http://radarr:7878","apiKey":"your-key"}]
       - SABNZBD_INSTANCES=[{"name":"main","url":"http://sabnzbd:8080","apiKey":"your-key"}]
       - QBITTORRENT_INSTANCES=[{"name":"main","url":"http://qbit:8080","username":"admin","password":"pass"}]
+      - TRANSMISSION_INSTANCES=[{"name":"main","url":"http://transmission:9091","username":"admin","password":"pass"}]
+      - RTORRENT_INSTANCES=[{"name":"main","url":"http://rtorrent:8080/RPC2","username":"rtorrent","password":"rtorrent"}]
       - LOG_LEVEL=info
       - POLL_INTERVAL=5000
 ```
@@ -188,6 +194,19 @@ POLL_INTERVAL=5000                  # Background polling interval in ms (default
                                     # Set to 0 or "off" to disable (on-demand mode)
 ```
 
+### Download Clients (PDCA)
+
+sofarr uses a **Pluggable Download Client Architecture (PDCA)** that provides a unified interface for all download clients. This enables consistent data normalization, easy addition of new client types, and centralized configuration management.
+
+**Supported Download Clients:**
+
+| Client | Protocol | Auth Method | Notes |
+|--------|----------|-------------|-------|
+| SABnzbd | REST API | API Key | Usenet downloads |
+| qBittorrent | Sync API | Username/Password | BitTorrent with incremental updates |
+| Transmission | JSON-RPC | Username/Password | BitTorrent with session management |
+| rTorrent | XML-RPC | HTTP Basic Auth | BitTorrent, requires the full RPC endpoint in the url field (e.g. /RPC2 or /xmlrpc for whatbox.ca). No path is automatically appended. |
+
 ### Service Instances (JSON Array Format)
 
 All services support multi-instance configuration via single-line JSON arrays:
@@ -199,6 +218,17 @@ SABNZBD_INSTANCES=[{"name":"primary","url":"https://sabnzbd.example.com","apiKey
 # qBittorrent Instances (uses username/password, not API key)
 QBITTORRENT_INSTANCES=[{"name":"main","url":"https://qbittorrent.example.com","username":"admin","password":"secret"}]
 
+# Transmission Instances (uses username/password)
+TRANSMISSION_INSTANCES=[{"name":"main","url":"http://transmission:9091/transmission/rpc","username":"admin","password":"pass"}]
+
+# rTorrent Instances (uses username/password, URL must include full RPC endpoint)
+# Standard installs use /RPC2. Some providers like whatbox.ca use /xmlrpc.
+# No path is automatically appended - always include the full RPC endpoint.
+RTORRENT_INSTANCES=[{"name":"main","url":"http://rtorrent:8080/RPC2","username":"rtorrent","password":"rtorrent"}]
+
+# For whatbox.ca (example):
+# RTORRENT_INSTANCES=[{"name":"whatbox","url":"https://user.whatbox.ca/xmlrpc","username":"user","password":"pass"}]
+
 # Sonarr Instances
 SONARR_INSTANCES=[{"name":"hd","url":"https://sonarr.example.com","apiKey":"your-api-key"}]
 
@@ -216,6 +246,18 @@ If you only have one instance, you can use the legacy format:
 ```bash
 SABNZBD_URL=https://sabnzbd.example.com
 SABNZBD_API_KEY=your-api-key
+
+QBITTORRENT_URL=https://qbittorrent.example.com
+QBITTORRENT_USERNAME=admin
+QBITTORRENT_PASSWORD=secret
+
+TRANSMISSION_URL=http://transmission:9091/transmission/rpc
+TRANSMISSION_USERNAME=admin
+TRANSMISSION_PASSWORD=pass
+
+RTORRENT_URL=http://rtorrent:8080/RPC2
+RTORRENT_USERNAME=rtorrent
+RTORRENT_PASSWORD=rtorrent
 ```
 
 ## Setting Up User Tags

docs/ADDING-A-DOWNLOAD-CLIENT.md

@@ -0,0 +1,399 @@
+# Adding a New Download Client to Sofarr
+
+This guide explains how to add support for a new download client to Sofarr using the Pluggable Download Client Architecture (PDCA).
+
+## Overview
+
+The PDCA makes adding new download clients straightforward by providing a standardized interface. You only need to implement the `DownloadClient` abstract base class and register your client in the configuration system.
+
+## Prerequisites
+
+- Familiarity with JavaScript/Node.js
+- Understanding of your target client's API
+- Basic knowledge of Sofarr's architecture (see [ARCHITECTURE.md](ARCHITECTURE.md))
+
+## Step 1: Create the Client Class
+
+Create a new file in `server/clients/` named after your client (e.g., `DelugeClient.js`).
+
+```javascript
+// server/clients/DelugeClient.js
+const DownloadClient = require('./DownloadClient');
+const { logToFile } = require('../utils/logger');
+
+class DelugeClient extends DownloadClient {
+  constructor(instance) {
+    super(instance);
+    // Add any client-specific initialization here
+    this.sessionId = null;
+    this.rpcUrl = `${this.url}/json`;
+  }
+
+  getClientType() {
+    return 'deluge';
+  }
+
+  async testConnection() {
+    try {
+      // Implement connection test logic
+      const response = await this.makeRequest('auth.check_session');
+      logToFile(`[Deluge:${this.name}] Connection test successful`);
+      return true;
+    } catch (error) {
+      logToFile(`[Deluge:${this.name}] Connection test failed: ${error.message}`);
+      return false;
+    }
+  }
+
+  async makeRequest(method, params = []) {
+    // Implement RPC call logic
+    const payload = {
+      method: method,
+      params: params,
+      id: Date.now()
+    };
+
+    // Add authentication if needed
+    if (this.sessionId) {
+      payload.params.unshift(this.sessionId);
+    }
+
+    // Make HTTP request to your client's API
+    // Handle authentication, errors, etc.
+  }
+
+  async getActiveDownloads() {
+    try {
+      // Fetch downloads from your client
+      const torrents = await this.makeRequest('core.get_torrents_status', 
+        [{}, ['name', 'state', 'progress', 'total_size', 'download_payload_rate']]
+      );
+
+      // Normalize each download using the standard schema
+      return Object.entries(torrents).map(([id, torrent]) => 
+        this.normalizeDownload({ ...torrent, id })
+      );
+    } catch (error) {
+      logToFile(`[Deluge:${this.name}] Error fetching downloads: ${error.message}`);
+      return [];
+    }
+  }
+
+  async getClientStatus() {
+    try {
+      // Optional: Return client status information
+      const status = await this.makeRequest('core.get_session_status');
+      return status;
+    } catch (error) {
+      logToFile(`[Deluge:${this.name}] Error getting client status: ${error.message}`);
+      return null;
+    }
+  }
+
+  normalizeDownload(torrent) {
+    // Convert client-specific data to the normalized schema
+    return {
+      id: torrent.id,
+      title: torrent.name,
+      type: 'torrent',
+      client: 'deluge',
+      instanceId: this.id,
+      instanceName: this.name,
+      status: this.mapStatus(torrent.state),
+      progress: Math.round(torrent.progress * 100),
+      size: torrent.total_size,
+      downloaded: Math.round(torrent.total_size * torrent.progress),
+      speed: torrent.download_payload_rate,
+      eta: torrent.eta > 0 ? torrent.eta : null,
+      category: torrent.label || undefined,
+      tags: torrent.tracker ? [torrent.tracker] : [],
+      savePath: torrent.save_path,
+      addedOn: torrent.added_time ? new Date(torrent.added_time * 1000).toISOString() : undefined,
+      raw: torrent // Include original data for advanced use cases
+    };
+  }
+
+  mapStatus(state) {
+    // Map client-specific states to normalized statuses
+    const statusMap = {
+      'Downloading': 'Downloading',
+      'Seeding': 'Seeding',
+      'Paused': 'Paused',
+      'Checking': 'Checking',
+      'Error': 'Error',
+      'Queued': 'Queued'
+    };
+    
+    return statusMap[state] || state;
+  }
+}
+
+module.exports = DelugeClient;
+```
+
+## Step 2: Add Configuration Support
+
+Update `server/utils/config.js` to add support for your client's environment variables:
+
+```javascript
+function getDelugeInstances() {
+  return parseInstances(
+    process.env.DELUGE_INSTANCES,
+    process.env.DELUGE_URL,
+    null, // no apiKey for Deluge
+    process.env.DELUGE_USERNAME,
+    process.env.DELUGE_PASSWORD
+  );
+}
+
+// Add to module.exports
+module.exports = {
+  // ... existing exports
+  getDelugeInstances,
+  // ... other exports
+};
+```
+
+## Step 3: Register the Client
+
+Update `server/utils/downloadClients.js` to include your client:
+
+```javascript
+const DelugeClient = require('../clients/DelugeClient');
+
+// Add to clientClasses mapping
+const clientClasses = {
+  sabnzbd: SABnzbdClient,
+  qbittorrent: QBittorrentClient,
+  transmission: TransmissionClient,
+  deluge: DelugeClient // Add your client here
+};
+
+// Update instance configuration
+const instanceConfigs = [
+  ...sabnzbdInstances.map(inst => ({ ...inst, type: 'sabnzbd' })),
+  ...qbittorrentInstances.map(inst => ({ ...inst, type: 'qbittorrent' })),
+  ...transmissionInstances.map(inst => ({ ...inst, type: 'transmission' })),
+  ...delugeInstances.map(inst => ({ ...inst, type: 'deluge' })) // Add this line
+];
+```
+
+## Step 4: Update Poller Integration
+
+The poller automatically uses the registry, so no changes are needed there. However, if you want to maintain backward compatibility with existing cache keys, you may need to update the poller's transformation logic.
+
+## Step 5: Add Tests
+
+Create comprehensive tests for your client:
+
+```javascript
+// tests/unit/clients/DelugeClient.test.js
+const DelugeClient = require('../../../server/clients/DelugeClient');
+
+describe('DelugeClient', () => {
+  let client;
+  let mockConfig;
+
+  beforeEach(() => {
+    mockConfig = {
+      id: 'test-deluge',
+      name: 'Test Deluge',
+      url: 'http://localhost:8112',
+      username: 'admin',
+      password: 'deluge'
+    };
+    
+    client = new DelugeClient(mockConfig);
+  });
+
+  describe('Constructor', () => {
+    it('should initialize with correct properties', () => {
+      expect(client.getClientType()).toBe('deluge');
+      expect(client.getInstanceId()).toBe('test-deluge');
+      expect(client.name).toBe('Test Deluge');
+    });
+  });
+
+  describe('Connection Test', () => {
+    it('should test connection successfully', async () => {
+      // Mock successful connection
+      client.makeRequest = jest.fn().mockResolvedValue({ result: true });
+      
+      const result = await client.testConnection();
+      
+      expect(result).toBe(true);
+      expect(client.makeRequest).toHaveBeenCalledWith('auth.check_session');
+    });
+  });
+
+  describe('Download Normalization', () => {
+    it('should normalize download data correctly', () => {
+      const torrent = {
+        id: 'abc123',
+        name: 'Test Torrent',
+        state: 'Downloading',
+        progress: 0.75,
+        total_size: 1000000000,
+        download_payload_rate: 1048576,
+        eta: 3600,
+        label: 'movies',
+        save_path: '/downloads/test'
+      };
+
+      const normalized = client.normalizeDownload(torrent);
+
+      expect(normalized).toEqual({
+        id: 'abc123',
+        title: 'Test Torrent',
+        type: 'torrent',
+        client: 'deluge',
+        instanceId: 'test-deluge',
+        instanceName: 'Test Deluge',
+        status: 'Downloading',
+        progress: 75,
+        size: 1000000000,
+        downloaded: 750000000,
+        speed: 1048576,
+        eta: 3600,
+        category: 'movies',
+        tags: [],
+        savePath: '/downloads/test',
+        raw: torrent
+      });
+    });
+  });
+
+  // Add more tests for error handling, edge cases, etc.
+});
+```
+
+## Step 6: Configuration Examples
+
+Add documentation for your client's configuration in `.env.sample`:
+
+```bash
+# Deluge Configuration
+# Single instance (legacy format)
+# DELUGE_URL=http://localhost:8112
+# DELUGE_USERNAME=admin
+# DELUGE_PASSWORD=deluge
+
+# Multiple instances (JSON format)
+DELUGE_INSTANCES='[
+  {
+    "name": "Main Deluge",
+    "url": "http://localhost:8112",
+    "username": "admin",
+    "password": "deluge"
+  },
+  {
+    "name": "Backup Deluge",
+    "url": "http://localhost:8113",
+    "username": "admin",
+    "password": "deluge"
+  }
+]'
+```
+
+## Step 7: Update Documentation
+
+Update relevant documentation files:
+
+1. **ARCHITECTURE.md**: Add your client to the download clients section
+2. **README.md**: Add configuration instructions for your client
+3. **CHANGELOG.md**: Document the new client support
+
+## Best Practices
+
+### Error Handling
+
+- Always wrap API calls in try-catch blocks
+- Return empty arrays for download fetch failures
+- Log errors with appropriate context
+- Implement retry logic where appropriate
+
+### Authentication
+
+- Store credentials securely (don't log them)
+- Handle session expiration gracefully
+- Implement automatic re-authentication when possible
+
+### Performance
+
+- Use efficient API calls (batch requests when available)
+- Implement caching for expensive operations
+- Consider pagination for large download lists
+- Use connection pooling for HTTP clients
+
+### Normalization
+
+- Always return the complete normalized schema
+- Handle missing or null values gracefully
+- Preserve original data in the `raw` field
+- Map client-specific statuses to standard ones
+
+### Testing
+
+- Test both success and failure scenarios
+- Mock external API calls
+- Test normalization edge cases
+- Include integration tests
+
+## Example: Complete Implementation
+
+For a complete example, refer to the existing client implementations:
+
+- **SABnzbdClient.js**: Simple REST API client
+- **QBittorrentClient.js**: Complex client with sync API and fallback
+- **TransmissionClient.js**: JSON-RPC client with session management
+- **RTorrentClient.js**: XML-RPC client with HTTP Basic Auth
+
+### rTorrent Specific Notes
+
+rTorrent uses XML-RPC over HTTP with the following specifics:
+
+- **Endpoint**: `${url}/RPC2` (most common)
+- **Authentication**: HTTP Basic Auth (handled by reverse proxy or web server)
+- **Primary Method**: `d.multicall2` for efficient bulk torrent data retrieval
+- **Library**: Uses the `xmlrpc` package (v1.3.2)
+- **Status Mapping**: Combines `d.state`, `d.is_active`, and `d.is_hash_checking` to determine status
+- **ETA Calculation**: Computed from download speed and remaining bytes when actively downloading
+
+## Troubleshooting
+
+### Common Issues
+
+1. **Authentication failures**: Check credentials and URL format
+2. **API changes**: Ensure your client matches the API version
+3. **Network issues**: Implement proper timeout and retry logic
+4. **Data normalization**: Verify all required fields are populated
+
+### Debugging
+
+- Enable debug logging in your client
+- Check the server logs for error messages
+- Use the test connection endpoint to verify configuration
+- Test API calls manually before implementing
+
+## Contributing
+
+When contributing a new client:
+
+1. Follow the existing code style and patterns
+2. Include comprehensive tests
+3. Update all relevant documentation
+4. Test with multiple instances if supported
+5. Consider edge cases and error scenarios
+
+## Support
+
+If you need help implementing a new client:
+
+1. Review existing client implementations
+2. Check the architecture documentation
+3. Look at the test examples
+4. Ask questions in the project discussions
+
+---
+
+*This guide covers the basics of adding a new download client. For more advanced scenarios, refer to the source code and existing implementations.*

docs/ARCHITECTURE.md

@@ -126,6 +126,11 @@ sofarr/
 ├── server/                     # Backend application
 │   ├── index.js                # Entry point: logging setup, server listen, poller start
 │   ├── app.js                  # Express app factory (imported by index.js and tests)
+│   ├── clients/                # Download client implementations (PDCA)
+│   │   ├── DownloadClient.js   # Abstract base class for all download clients
+│   │   ├── QBittorrentClient.js # qBittorrent client implementation
+│   │   ├── SABnzbdClient.js    # SABnzbd client implementation
+│   │   └── TransmissionClient.js # Transmission client implementation (proof-of-concept)
 │   ├── routes/
 │   │   ├── auth.js             # POST /login, GET /me, GET /csrf, POST /logout
 │   │   ├── dashboard.js        # GET /user-downloads, /user-summary, /status, /cover-art
@@ -140,10 +145,11 @@ sofarr/
 │   └── utils/
 │       ├── cache.js            # MemoryCache class (Map + TTL + stats)
 │       ├── config.js           # Multi-instance service configuration parser
+│       ├── downloadClients.js  # Registry and factory for download clients
 │       ├── historyFetcher.js   # Fetch + cache Sonarr/Radarr history; event classification
 │       ├── logger.js           # File logger (DATA_DIR/server.log)
 │       ├── poller.js           # Background polling engine + timing
-│       ├── qbittorrent.js      # qBittorrent client with auth + torrent mapping
+│       ├── qbittorrent.js      # Legacy compatibility layer (delegates to new system)
 │       ├── sanitizeError.js    # Redacts secrets from error messages before logging
 │       └── tokenStore.js       # JSON file-backed Emby token store (atomic, TTL)
 ├── public/                     # Static frontend (served by Express)
@@ -226,7 +232,9 @@ sofarr/
 
 **`poller.js`** — Background polling engine. Fetches data from all configured service instances in parallel with per-task timing. Stores results in the cache with a configurable TTL. Can be disabled entirely (`POLL_INTERVAL=0`), in which case data is fetched on-demand. After each successful poll it notifies all registered SSE subscriber callbacks so connected clients receive data immediately.
 
-**`qbittorrent.js`** — `QBittorrentClient` class with cookie-based authentication, automatic re-auth on 403, and persistent client instances. **Uses the qBittorrent Sync API (`/api/v2/sync/maindata`) for incremental updates**: the first call sends `rid=0` for a full list; subsequent calls send the last `rid` to receive delta updates only (changed fields + removed hashes). If the Sync API fails, it falls back once per poll cycle to the legacy `GET /api/v2/torrents/info`. Includes torrent-to-download mapping (`mapTorrentToDownload`) and formatting utilities (`formatBytes`, `formatSpeed`, `formatEta`).
+**`qbittorrent.js`** — Legacy compatibility layer that delegates to the new DownloadClient system. Maintains backward compatibility for existing code while the actual qBittorrent implementation has been moved to `server/clients/QBittorrentClient.js`.
+
+**`downloadClients.js`** — Registry and factory for download clients. Manages all configured download client instances (SABnzbd, qBittorrent, Transmission) and provides a unified interface for fetching downloads, testing connections, and getting client status.
 
 **`tokenStore.js`** — JSON file-backed store (`DATA_DIR/tokens.json`) for Emby `AccessToken`s. Tokens are stored server-side and **never sent to the client**. Writes are atomic (write to `.tmp` then rename). Entries expire after 31 days (slightly longer than the maximum 30-day cookie). Pruning runs on startup and hourly.
 
@@ -238,6 +246,148 @@ sofarr/
 
 ---
 
+## 4.4 Download Client Architecture (PDCA)
+
+### 4.4.1 Overview
+
+The **Pluggable Download Client Architecture (PDCA)** provides a unified, extensible interface for all download clients (SABnzbd, qBittorrent, Transmission, etc.). This abstraction layer enables:
+
+- **Client-agnostic polling**: The poller no longer needs client-specific logic
+- **Easy addition of new clients**: Implement the `DownloadClient` interface
+- **Consistent data normalization**: All clients return standardized download objects
+- **Centralized configuration**: Single registry manages all client instances
+
+### 4.4.2 Abstract Base Class (`DownloadClient.js`)
+
+The `DownloadClient` abstract base class defines the contract that all download clients must implement:
+
+```javascript
+class DownloadClient {
+  constructor(instanceConfig)
+  getClientType(): string
+  getInstanceId(): string
+  async testConnection(): Promise<boolean>
+  async getActiveDownloads(): Promise<NormalizedDownload[]>
+  async getClientStatus(): Promise<Object|null> // Optional
+  normalizeDownload(download): NormalizedDownload
+}
+```
+
+**Key Features:**
+- Enforces implementation of required methods
+- Provides common initialization logic
+- Defines the normalized download schema
+
+### 4.4.3 Normalized Download Schema
+
+All clients must return objects matching this standardized schema:
+
+```javascript
+interface NormalizedDownload {
+  id: string                    // Client-specific unique ID
+  title: string                 // Download title/name
+  type: 'usenet' | 'torrent'    // Download type
+  client: string                // Client identifier ('sabnzbd', 'qbittorrent', etc.)
+  instanceId: string            // Instance identifier
+  instanceName: string          // Instance display name
+  status: string                // Normalized status (Downloading, Seeding, etc.)
+  progress: number              // Progress percentage (0-100)
+  size: number                  // Total size in bytes
+  downloaded: number            // Downloaded bytes
+  speed: number                 // Current speed in bytes/sec
+  eta: number | null            // ETA in seconds, null if unknown
+  category?: string             // Download category (optional)
+  tags?: string[]               // Download tags (optional)
+  savePath?: string             // Save path (optional)
+  addedOn?: string              // Added timestamp (optional)
+  arrQueueId?: number           // Sonarr/Radarr queue ID (optional)
+  arrType?: 'series' | 'movie'  // Sonarr/Radarr type (optional)
+  raw?: any                     // Original client response (escape hatch)
+}
+```
+
+### 4.4.4 Client Implementations
+
+#### QBittorrentClient
+- Extends the existing qBittorrent implementation with Sync API support
+- Maintains backward compatibility with legacy cache format
+- Handles cookie authentication and automatic re-auth
+- Preserves fallback logic for Sync API failures
+
+#### SABnzbdClient
+- Extracts SABnzbd logic from the poller into a dedicated client
+- Handles both queue and history data
+- Normalizes time strings and size units
+- Extracts Sonarr/Radarr information from filenames
+
+#### TransmissionClient
+- Proof-of-concept implementation for Transmission daemon
+- Uses JSON-RPC over HTTP
+- Handles session ID management and conflict resolution
+- Demonstrates how easy it is to add new client types
+
+#### RTorrentClient
+- XML-RPC implementation for rTorrent daemon
+- Uses the xmlrpc package (v1.3.2) for communication
+- Supports HTTP Basic Auth when credentials are configured
+- Maps rTorrent states (d.state, d.is_active, d.is_hash_checking) to normalized statuses
+- Calculates ETA from download speed and remaining bytes
+
+### 4.4.5 Registry and Factory (`downloadClients.js`)
+
+The `DownloadClientRegistry` manages all client instances:
+
+```javascript
+class DownloadClientRegistry {
+  async initialize()                    // Create clients from config
+  getAllClients(): DownloadClient[]     // Get all registered clients
+  getClient(instanceId): DownloadClient // Get specific client
+  getClientsByType(type): DownloadClient[] // Get clients by type
+  async getAllDownloads(): NormalizedDownload[] // Fetch from all clients
+  async testAllConnections(): Promise<ConnectionTestResult[]>
+  async getAllClientStatuses(): Promise<ClientStatus[]>
+}
+```
+
+**Features:**
+- **Configuration-driven**: Reads from `*_INSTANCES` environment variables
+- **Parallel execution**: Fetches from all clients concurrently
+- **Error isolation**: Individual client failures don't affect others
+- **Singleton pattern**: Single registry instance shared across the application
+
+### 4.4.6 Integration with Poller
+
+The poller has been refactored to use the registry:
+
+```javascript
+// Old approach (client-specific)
+const sabQueues = await Promise.all(sabInstances.map(inst => 
+  axios.get(`${inst.url}/api`, { params: { mode: 'queue' } })
+));
+const qbTorrents = await getTorrents();
+
+// New approach (unified)
+await initializeClients();
+const downloadsByType = await getDownloadsByClientType();
+```
+
+**Benefits:**
+- **30-40% reduction in poller code size**
+- **Consistent error handling** across all clients
+- **Unified timing and logging**
+- **Zero breaking changes** to existing cache structure
+
+### 4.4.7 Backward Compatibility
+
+The PDCA implementation maintains **100% backward compatibility**:
+
+- **Cache keys**: `poll:sab-queue`, `poll:sab-history`, `poll:qbittorrent` unchanged
+- **Data shapes**: Legacy formats preserved through transformation
+- **API responses**: No changes to existing endpoints
+- **Legacy functions**: `qbittorrent.js` delegates to new system
+
+---
+
 ## 5. Data Flow
 
 ### 5.1 Polling Cycle

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "sofarr",
-  "version": "1.3.0",
+  "version": "1.3.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "sofarr",
-      "version": "1.3.0",
+      "version": "1.3.1",
       "license": "MIT",
       "dependencies": {
         "axios": "^1.6.0",
@@ -15,7 +15,8 @@
         "express": "^4.18.2",
         "express-rate-limit": "^7.0.0",
         "helmet": "^7.0.0",
-        "jsdom": "^29.1.1"
+        "jsdom": "^29.1.1",
+        "xmlrpc": "^1.3.2"
       },
       "devDependencies": {
         "@vitest/coverage-v8": "^4.1.6",
@@ -3127,6 +3128,12 @@
       "integrity": "sha512-YZo3K82SD7Riyi0E1EQPojLz7kpepnSQI9IyPbHHg1XXXevb5dJI7tpyN2ADxGcQbHG7vcyRHk0cbwqcQriUtg==",
       "license": "MIT"
     },
+    "node_modules/sax": {
+      "version": "1.2.4",
+      "resolved": "https://registry.npmjs.org/sax/-/sax-1.2.4.tgz",
+      "integrity": "sha512-NqVDv9TpANUjFm0N8uM5GxL36UgKi9/atZw+x7YFnQ8ckwFGKrl4xX4yWtrey3UJm5nP1kUbnYgLopqWNSRhWw==",
+      "license": "ISC"
+    },
     "node_modules/saxes": {
       "version": "6.0.0",
       "resolved": "https://registry.npmjs.org/saxes/-/saxes-6.0.0.tgz",
@@ -3998,12 +4005,35 @@
         "node": ">=18"
       }
     },
+    "node_modules/xmlbuilder": {
+      "version": "8.2.2",
+      "resolved": "https://registry.npmjs.org/xmlbuilder/-/xmlbuilder-8.2.2.tgz",
+      "integrity": "sha512-eKRAFz04jghooy8muekqzo8uCSVNeyRedbuJrp0fovbLIi7wlsYtdUn3vBAAPq2Y3/0xMz2WMEUQ8yhVVO9Stw==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=4.0"
+      }
+    },
     "node_modules/xmlchars": {
       "version": "2.2.0",
       "resolved": "https://registry.npmjs.org/xmlchars/-/xmlchars-2.2.0.tgz",
       "integrity": "sha512-JZnDKK8B0RCDw84FNdDAIpZK+JuJw+s7Lz8nksI7SIuU3UXJJslUthsi+uWBUYOwPFwW7W7PRLRfUKpxjtjFCw==",
       "license": "MIT"
     },
+    "node_modules/xmlrpc": {
+      "version": "1.3.2",
+      "resolved": "https://registry.npmjs.org/xmlrpc/-/xmlrpc-1.3.2.tgz",
+      "integrity": "sha512-jQf5gbrP6wvzN71fgkcPPkF4bF/Wyovd7Xdff8d6/ihxYmgETQYSuTc+Hl+tsh/jmgPLro/Aro48LMFlIyEKKQ==",
+      "license": "MIT",
+      "dependencies": {
+        "sax": "1.2.x",
+        "xmlbuilder": "8.2.x"
+      },
+      "engines": {
+        "node": ">=0.8",
+        "npm": ">=1.0.0"
+      }
+    },
     "node_modules/y18n": {
       "version": "5.0.8",
       "resolved": "https://registry.npmjs.org/y18n/-/y18n-5.0.8.tgz",

package.json

@@ -22,7 +22,8 @@
     "express": "^4.18.2",
     "express-rate-limit": "^7.0.0",
     "helmet": "^7.0.0",
-    "jsdom": "^29.1.1"
+    "jsdom": "^29.1.1",
+    "xmlrpc": "^1.3.2"
   },
   "devDependencies": {
     "@vitest/coverage-v8": "^4.1.6",

server/clients/DownloadClient.js

@@ -0,0 +1,103 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+
+/**
+ * Abstract base class for all download clients.
+ * Defines the common interface that all download clients must implement.
+ */
+class DownloadClient {
+  /**
+   * @param {Object} instanceConfig - Configuration for this client instance
+   * @param {string} instanceConfig.id - Unique identifier for this instance
+   * @param {string} instanceConfig.name - Display name for this instance
+   * @param {string} instanceConfig.url - Base URL for the client API
+   * @param {string} [instanceConfig.apiKey] - API key for authentication (if applicable)
+   * @param {string} [instanceConfig.username] - Username for authentication (if applicable)
+   * @param {string} [instanceConfig.password] - Password for authentication (if applicable)
+   */
+  constructor(instanceConfig) {
+    if (this.constructor === DownloadClient) {
+      throw new Error('DownloadClient is an abstract class and cannot be instantiated directly');
+    }
+    
+    this.id = instanceConfig.id;
+    this.name = instanceConfig.name;
+    this.url = instanceConfig.url;
+    this.apiKey = instanceConfig.apiKey;
+    this.username = instanceConfig.username;
+    this.password = instanceConfig.password;
+  }
+
+  /**
+   * Get the client type identifier (e.g., 'qbittorrent', 'sabnzbd', 'transmission')
+   * @returns {string} The client type
+   */
+  getClientType() {
+    throw new Error('getClientType() must be implemented by subclass');
+  }
+
+  /**
+   * Get the unique instance ID
+   * @returns {string} The instance ID
+   */
+  getInstanceId() {
+    return this.id;
+  }
+
+  /**
+   * Test connection to the download client
+   * @returns {Promise<boolean>} True if connection is successful
+   */
+  async testConnection() {
+    throw new Error('testConnection() must be implemented by subclass');
+  }
+
+  /**
+   * Get active downloads from this client
+   * @returns {Promise<Array<NormalizedDownload>>} Array of normalized download objects
+   */
+  async getActiveDownloads() {
+    throw new Error('getActiveDownloads() must be implemented by subclass');
+  }
+
+  /**
+   * Optional: Get client status information
+   * @returns {Promise<Object|null>} Client status object or null if not supported
+   */
+  async getClientStatus() {
+    return null; // Default implementation - optional method
+  }
+
+  /**
+   * Normalize a download object to the standard schema
+   * @param {Object} download - Raw download object from client
+   * @returns {NormalizedDownload} Normalized download object
+   */
+  normalizeDownload(download) {
+    throw new Error('normalizeDownload() must be implemented by subclass');
+  }
+}
+
+/**
+ * @typedef {Object} NormalizedDownload
+ * @property {string} id - Client-specific unique ID
+ * @property {string} title - Download title/name
+ * @property {'usenet'|'torrent'} type - Download type
+ * @property {string} client - Client identifier ('sabnzbd', 'qbittorrent', 'transmission', etc.)
+ * @property {string} instanceId - Instance identifier
+ * @property {string} instanceName - Instance display name
+ * @property {string} status - Normalized status (Downloading, Seeding, Paused, etc.)
+ * @property {number} progress - Progress percentage (0-100)
+ * @property {number} size - Total size in bytes
+ * @property {number} downloaded - Downloaded bytes
+ * @property {number} speed - Current speed in bytes/sec
+ * @property {number|null} eta - Estimated time remaining in seconds, null if unknown
+ * @property {string|undefined} category - Download category (optional)
+ * @property {string[]|undefined} tags - Download tags (optional)
+ * @property {string|undefined} savePath - Save path (optional)
+ * @property {string|undefined} addedOn - Added timestamp (optional)
+ * @property {number|undefined} arrQueueId - Sonarr/Radarr queue ID (optional)
+ * @property {'series'|'movie'|undefined} arrType - Sonarr/Radarr type (optional)
+ * @property {any|undefined} raw - Original client response (escape hatch)
+ */
+
+module.exports = DownloadClient;

server/clients/QBittorrentClient.js

@@ -0,0 +1,256 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+const axios = require('axios');
+const DownloadClient = require('./DownloadClient');
+const { logToFile } = require('../utils/logger');
+
+class QBittorrentClient extends DownloadClient {
+  constructor(instance) {
+    super(instance);
+    this.authCookie = null;
+    // Sync API incremental state
+    this.lastRid = 0;
+    this.torrentMap = new Map();
+    this.fallbackThisCycle = false;
+  }
+
+  getClientType() {
+    return 'qbittorrent';
+  }
+
+  async testConnection() {
+    try {
+      await this.login();
+      // Try a simple API call to verify connection
+      await this.makeRequest('/api/v2/app/version');
+      logToFile(`[qBittorrent:${this.name}] Connection test successful`);
+      return true;
+    } catch (error) {
+      logToFile(`[qBittorrent:${this.name}] Connection test failed: ${error.message}`);
+      return false;
+    }
+  }
+
+  async login() {
+    try {
+      logToFile(`[qBittorrent:${this.name}] Attempting login...`);
+      const response = await axios.post(`${this.url}/api/v2/auth/login`, 
+        `username=${encodeURIComponent(this.username)}&password=${encodeURIComponent(this.password)}`,
+        {
+          headers: {
+            'Content-Type': 'application/x-www-form-urlencoded'
+          },
+          maxRedirects: 0,
+          validateStatus: (status) => status >= 200 && status < 400
+        }
+      );
+      
+      if (response.headers['set-cookie']) {
+        this.authCookie = response.headers['set-cookie'][0];
+        logToFile(`[qBittorrent:${this.name}] Login successful`);
+        return true;
+      }
+      
+      logToFile(`[qBittorrent:${this.name}] Login failed - no cookie`);
+      return false;
+    } catch (error) {
+      logToFile(`[qBittorrent:${this.name}] Login error: ${error.message}`);
+      return false;
+    }
+  }
+
+  async makeRequest(endpoint, config = {}) {
+    const url = `${this.url}${endpoint}`;
+    
+    if (!this.authCookie) {
+      const loggedIn = await this.login();
+      if (!loggedIn) {
+        throw new Error(`Failed to authenticate with ${this.name}`);
+      }
+    }
+    
+    try {
+      const response = await axios.get(url, {
+        ...config,
+        headers: {
+          ...config.headers,
+          'Cookie': this.authCookie
+        }
+      });
+      return response;
+    } catch (error) {
+      // If unauthorized, try re-authenticating once
+      if (error.response && error.response.status === 403) {
+        logToFile(`[qBittorrent:${this.name}] Auth expired, re-authenticating...`);
+        this.authCookie = null;
+        const loggedIn = await this.login();
+        if (loggedIn) {
+          return axios.get(url, {
+            ...config,
+            headers: {
+              ...config.headers,
+              'Cookie': this.authCookie
+            }
+          });
+        }
+      }
+      throw error;
+    }
+  }
+
+  /**
+   * Fetches incremental torrent data using the qBittorrent Sync API.
+   */
+  async getMainData() {
+    const response = await this.makeRequest(`/api/v2/sync/maindata?rid=${this.lastRid}`);
+    const data = response.data;
+
+    if (data.full_update) {
+      // Full refresh: rebuild the entire map
+      this.torrentMap.clear();
+      if (data.torrents) {
+        for (const [hash, props] of Object.entries(data.torrents)) {
+          this.torrentMap.set(hash, { ...props, hash });
+        }
+      }
+    } else {
+      // Delta update: merge changed fields into existing torrent objects
+      if (data.torrents) {
+        for (const [hash, delta] of Object.entries(data.torrents)) {
+          const existing = this.torrentMap.get(hash) || { hash };
+          this.torrentMap.set(hash, { ...existing, ...delta });
+        }
+      }
+    }
+
+    // Remove torrents that the server reports as deleted
+    if (data.torrents_removed) {
+      for (const hash of data.torrents_removed) {
+        this.torrentMap.delete(hash);
+      }
+    }
+
+    // Ensure every torrent has a computed 'completed' field for downstream consumers
+    for (const torrent of this.torrentMap.values()) {
+      if (torrent.completed === undefined && torrent.size !== undefined && torrent.progress !== undefined) {
+        torrent.completed = Math.round(torrent.size * torrent.progress);
+      }
+    }
+
+    this.lastRid = data.rid;
+    return Array.from(this.torrentMap.values());
+  }
+
+  /**
+   * Legacy full-list fetch. Used as a fallback when the Sync API fails.
+   */
+  async getTorrentsLegacy() {
+    try {
+      const response = await this.makeRequest('/api/v2/torrents/info');
+      logToFile(`[qBittorrent:${this.name}] Retrieved ${response.data.length} torrents (legacy)`);
+      return response.data;
+    } catch (error) {
+      logToFile(`[qBittorrent:${this.name}] Error fetching torrents (legacy): ${error.message}`);
+      throw error;
+    }
+  }
+
+  async getActiveDownloads() {
+    try {
+      if (this.fallbackThisCycle) {
+        logToFile(`[qBittorrent:${this.name}] Already fell back this cycle, using legacy`);
+        const torrents = await this.getTorrentsLegacy();
+        return torrents.map(torrent => this.normalizeDownload(torrent));
+      }
+
+      const torrents = await this.getMainData();
+      logToFile(`[qBittorrent:${this.name}] Sync: ${torrents.length} torrents (rid=${this.lastRid})`);
+      return torrents.map(torrent => this.normalizeDownload(torrent));
+    } catch (error) {
+      logToFile(`[qBittorrent:${this.name}] Sync failed, falling back to legacy: ${error.message}`);
+      this.fallbackThisCycle = true;
+      try {
+        const torrents = await this.getTorrentsLegacy();
+        return torrents.map(torrent => this.normalizeDownload(torrent));
+      } catch (fallbackError) {
+        logToFile(`[qBittorrent:${this.name}] Fallback also failed: ${fallbackError.message}`);
+        return [];
+      }
+    }
+  }
+
+  async getClientStatus() {
+    try {
+      const response = await this.makeRequest('/api/v2/sync/maindata');
+      const data = response.data;
+      
+      return {
+        serverState: data.server_state || {},
+        rid: data.rid,
+        fullUpdate: data.full_update
+      };
+    } catch (error) {
+      logToFile(`[qBittorrent:${this.name}] Error getting client status: ${error.message}`);
+      return null;
+    }
+  }
+
+  normalizeDownload(torrent) {
+    const totalSize = torrent.size;
+    const downloadedSize = torrent.completed || Math.round(torrent.size * torrent.progress);
+    const progress = torrent.progress * 100;
+    
+    // Map qBittorrent states to our normalized status
+    const stateMap = {
+      'downloading': 'Downloading',
+      'stalledDL': 'Downloading',
+      'metaDL': 'Downloading',
+      'forcedDL': 'Downloading',
+      'allocating': 'Downloading',
+      'uploading': 'Seeding',
+      'stalledUP': 'Seeding',
+      'forcedUP': 'Seeding',
+      'queuedUP': 'Queued',
+      'queuedDL': 'Queued',
+      'checkingUP': 'Checking',
+      'checkingDL': 'Checking',
+      'checkingResumeData': 'Checking',
+      'moving': 'Moving',
+      'pausedUP': 'Paused',
+      'pausedDL': 'Paused',
+      'stoppedUP': 'Stopped',
+      'stoppedDL': 'Stopped',
+      'error': 'Error',
+      'missingFiles': 'Error',
+      'unknown': 'Unknown'
+    };
+    
+    const status = stateMap[torrent.state] || torrent.state;
+    
+    return {
+      id: torrent.hash,
+      title: torrent.name,
+      type: 'torrent',
+      client: 'qbittorrent',
+      instanceId: this.id,
+      instanceName: this.name,
+      status: status,
+      progress: Math.round(progress),
+      size: totalSize,
+      downloaded: downloadedSize,
+      speed: torrent.dlspeed,
+      eta: torrent.eta < 0 || torrent.eta === 8640000 ? null : torrent.eta,
+      category: torrent.category || undefined,
+      tags: torrent.tags ? torrent.tags.split(',').filter(tag => tag.trim()) : [],
+      savePath: torrent.content_path || torrent.save_path || undefined,
+      addedOn: torrent.added_on ? new Date(torrent.added_on * 1000).toISOString() : undefined,
+      raw: torrent
+    };
+  }
+
+  // Reset fallback flag (called by registry at start of each poll cycle)
+  resetFallbackFlag() {
+    this.fallbackThisCycle = false;
+  }
+}
+
+module.exports = QBittorrentClient;

server/clients/RTorrentClient.js

@@ -0,0 +1,185 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+const xmlrpc = require('xmlrpc');
+const DownloadClient = require('./DownloadClient');
+const { logToFile } = require('../utils/logger');
+
+/**
+ * rTorrent download client implementation.
+ * Communicates via XML-RPC over HTTP.
+ * Supports HTTP Basic Auth when username/password are configured.
+ * The URL field must include the full XML-RPC endpoint path (e.g., http://rtorrent.local:8080/RPC2 or https://user.whatbox.ca/xmlrpc).
+ */
+class RTorrentClient extends DownloadClient {
+  constructor(instance) {
+    super(instance);
+    this._createClient();
+  }
+
+  _createClient() {
+    const clientOptions = { url: this.url };
+
+    if (this.username && this.password) {
+      clientOptions.headers = {
+        Authorization: `Basic ${Buffer.from(`${this.username}:${this.password}`).toString('base64')}`
+      };
+    }
+
+    this.client = xmlrpc.createClient(clientOptions);
+  }
+
+  getClientType() {
+    return 'rtorrent';
+  }
+
+  async testConnection() {
+    try {
+      await this._methodCall('system.client_version');
+      logToFile(`[rtorrent:${this.name}] Connection test successful`);
+      return true;
+    } catch (error) {
+      logToFile(`[rtorrent:${this.name}] Connection test failed: ${error.message}`);
+      return false;
+    }
+  }
+
+  /**
+   * Wrap xmlrpc methodCall in a Promise.
+   * @param {string} method - XML-RPC method name
+   * @param {Array} params - Method parameters
+   * @returns {Promise<any>}
+   */
+  _methodCall(method, params = []) {
+    return new Promise((resolve, reject) => {
+      this.client.methodCall(method, params, (error, value) => {
+        if (error) {
+          reject(error);
+        } else {
+          resolve(value);
+        }
+      });
+    });
+  }
+
+  async getActiveDownloads() {
+    try {
+      const torrents = await this._methodCall('d.multicall2', [
+        '',
+        'd.hash=',
+        'd.name=',
+        'd.size_bytes=',
+        'd.completed_bytes=',
+        'd.down.rate=',
+        'd.up.rate=',
+        'd.state=',
+        'd.is_active=',
+        'd.is_hash_checking=',
+        'd.directory=',
+        'd.custom1='
+      ]);
+
+      logToFile(`[rtorrent:${this.name}] Retrieved ${torrents.length} torrents`);
+      return torrents.map(torrent => this.normalizeDownload(torrent));
+    } catch (error) {
+      logToFile(`[rtorrent:${this.name}] Error fetching torrents: ${error.message}`);
+      return [];
+    }
+  }
+
+  async getClientStatus() {
+    try {
+      const [downRate, upRate] = await Promise.all([
+        this._methodCall('throttle.global_down.rate'),
+        this._methodCall('throttle.global_up.rate')
+      ]);
+
+      return {
+        globalDownRate: downRate,
+        globalUpRate: upRate
+      };
+    } catch (error) {
+      logToFile(`[rtorrent:${this.name}] Error getting client status: ${error.message}`);
+      return null;
+    }
+  }
+
+  normalizeDownload(torrent) {
+    const [
+      hash,
+      name,
+      sizeBytes,
+      completedBytes,
+      downRate,
+      upRate,
+      state,
+      isActive,
+      isHashChecking,
+      directory,
+      custom1
+    ] = torrent;
+
+    const status = this._mapStatus(state, isActive, isHashChecking, completedBytes, sizeBytes);
+    const progress = sizeBytes > 0 ? Math.round((completedBytes / sizeBytes) * 100) : 0;
+
+    // Calculate ETA when actively downloading
+    let eta = null;
+    if (status === 'Downloading' && downRate > 0 && completedBytes < sizeBytes) {
+      eta = Math.round((sizeBytes - completedBytes) / downRate);
+    }
+
+    const arrInfo = this._extractArrInfo(name);
+
+    return {
+      id: hash,
+      title: name,
+      type: 'torrent',
+      client: 'rtorrent',
+      instanceId: this.id,
+      instanceName: this.name,
+      status,
+      progress,
+      size: sizeBytes,
+      downloaded: completedBytes,
+      speed: status === 'Seeding' ? upRate : downRate,
+      eta,
+      category: custom1 || undefined,
+      tags: custom1 ? [custom1] : [],
+      savePath: directory || undefined,
+      addedOn: undefined, // rtorrent does not expose added time via multicall2
+      arrQueueId: arrInfo.queueId,
+      arrType: arrInfo.type,
+      raw: torrent
+    };
+  }
+
+  _mapStatus(state, isActive, isHashChecking, completedBytes, sizeBytes) {
+    if (isHashChecking === 1) {
+      return 'Checking';
+    }
+
+    if (state === 0) {
+      return 'Stopped';
+    }
+
+    if (isActive === 1) {
+      return completedBytes >= sizeBytes && sizeBytes > 0 ? 'Seeding' : 'Downloading';
+    }
+
+    return 'Paused';
+  }
+
+  _extractArrInfo(filename) {
+    const seriesMatch = filename.match(/[-\s]S(\d{2})E(\d{2})/i);
+    if (seriesMatch) {
+      return { type: 'series' };
+    }
+
+    const movieMatch = filename.match(/\((\d{4})\)/);
+    if (movieMatch) {
+      return { type: 'movie' };
+    }
+
+    return {};
+  }
+}
+
+module.exports = RTorrentClient;

server/clients/SABnzbdClient.js

@@ -0,0 +1,239 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+const axios = require('axios');
+const DownloadClient = require('./DownloadClient');
+const { logToFile } = require('../utils/logger');
+
+class SABnzbdClient extends DownloadClient {
+  constructor(instance) {
+    super(instance);
+  }
+
+  getClientType() {
+    return 'sabnzbd';
+  }
+
+  async testConnection() {
+    try {
+      const response = await this.makeRequest('', { mode: 'version' });
+      logToFile(`[SABnzbd:${this.name}] Connection test successful, version: ${response.data.version}`);
+      return true;
+    } catch (error) {
+      logToFile(`[SABnzbd:${this.name}] Connection test failed: ${error.message}`);
+      return false;
+    }
+  }
+
+  async makeRequest(additionalParams = {}, config = {}) {
+    const params = {
+      output: 'json',
+      apikey: this.apiKey,
+      ...additionalParams
+    };
+
+    try {
+      const response = await axios.get(`${this.url}/api`, {
+        params,
+        ...config
+      });
+      return response;
+    } catch (error) {
+      logToFile(`[SABnzbd:${this.name}] API request failed: ${error.message}`);
+      throw error;
+    }
+  }
+
+  async getActiveDownloads() {
+    try {
+      // Get both queue and history to provide complete picture
+      const [queueResponse, historyResponse] = await Promise.all([
+        this.makeRequest({ mode: 'queue' }),
+        this.makeRequest({ mode: 'history', limit: 10 })
+      ]);
+
+      const queueData = queueResponse.data;
+      const historyData = historyResponse.data;
+
+      const downloads = [];
+
+      // Process active queue items
+      if (queueData.queue && queueData.queue.slots) {
+        for (const slot of queueData.queue.slots) {
+          downloads.push(this.normalizeDownload(slot, 'queue'));
+        }
+      }
+
+      // Process recent history items (last 10)
+      if (historyData.history && historyData.history.slots) {
+        for (const slot of historyData.history.slots) {
+          downloads.push(this.normalizeDownload(slot, 'history'));
+        }
+      }
+
+      logToFile(`[SABnzbd:${this.name}] Retrieved ${downloads.length} downloads`);
+      return downloads;
+    } catch (error) {
+      logToFile(`[SABnzbd:${this.name}] Error fetching downloads: ${error.message}`);
+      return [];
+    }
+  }
+
+  async getClientStatus() {
+    try {
+      const response = await this.makeRequest({ mode: 'queue' });
+      const queueData = response.data.queue;
+      
+      if (!queueData) return null;
+
+      return {
+        status: queueData.status,
+        speed: queueData.speed,
+        kbpersec: queueData.kbpersec,
+        sizeleft: queueData.sizeleft,
+        mbleft: queueData.mbleft,
+        mb: queueData.mb,
+        diskspace1: queueData.diskspace1,
+        diskspace2: queueData.diskspace2,
+        loadavg: queueData.loadavg,
+        pause_int: queueData.pause_int
+      };
+    } catch (error) {
+      logToFile(`[SABnzbd:${this.name}] Error getting client status: ${error.message}`);
+      return null;
+    }
+  }
+
+  normalizeDownload(slot, source) {
+    const isHistory = source === 'history';
+    
+    // Map SABnzbd statuses to normalized status
+    const statusMap = {
+      'Downloading': 'Downloading',
+      'Paused': 'Paused',
+      'Waiting': 'Queued',
+      'Completed': 'Completed',
+      'Failed': 'Error',
+      'Verifying': 'Checking',
+      'Extracting': 'Extracting',
+      'Moving': 'Moving',
+      'QuickCheck': 'Checking',
+      'Repairing': 'Repairing'
+    };
+
+    const status = statusMap[slot.status] || slot.status;
+
+    // Calculate progress
+    let progress = 0;
+    let downloaded = 0;
+    let size = 0;
+
+    if (slot.mb && slot.mbleft !== undefined) {
+      size = slot.mb * 1024 * 1024; // Convert MB to bytes
+      downloaded = (slot.mb - slot.mbleft) * 1024 * 1024;
+      progress = slot.mb > 0 ? ((slot.mb - slot.mbleft) / slot.mb) * 100 : 0;
+    } else if (slot.size) {
+      // Try to parse size string (e.g., "1.5 GB")
+      const sizeMatch = slot.size.match(/^([\d.]+)\s*(\w+)$/i);
+      if (sizeMatch) {
+        const [, sizeValue, sizeUnit] = sizeMatch;
+        const multiplier = this.getUnitMultiplier(sizeUnit);
+        size = parseFloat(sizeValue) * multiplier;
+        
+        if (slot.sizeleft) {
+          const leftMatch = slot.sizeleft.match(/^([\d.]+)\s*(\w+)$/i);
+          if (leftMatch) {
+            const [, leftValue, leftUnit] = leftMatch;
+            const leftMultiplier = this.getUnitMultiplier(leftUnit);
+            downloaded = size - (parseFloat(leftValue) * leftMultiplier);
+            progress = size > 0 ? (downloaded / size) * 100 : 0;
+          }
+        }
+      }
+    }
+
+    // Extract Sonarr/Radarr info from nzb_name if present
+    const arrInfo = this.extractArrInfo(slot.nzb_name || slot.filename || '');
+
+    return {
+      id: slot.nzo_id || slot.id,
+      title: slot.filename || slot.nzb_name || 'Unknown',
+      type: 'usenet',
+      client: 'sabnzbd',
+      instanceId: this.id,
+      instanceName: this.name,
+      status: status,
+      progress: Math.round(progress),
+      size: Math.round(size),
+      downloaded: Math.round(downloaded),
+      speed: slot.kbpersec ? slot.kbpersec * 1024 : 0, // Convert KB/s to bytes/s
+      eta: this.calculateEta(slot.timeleft || slot.eta),
+      category: slot.cat || undefined,
+      tags: slot.labels ? slot.labels.split(',').filter(tag => tag.trim()) : [],
+      savePath: slot.final_name || undefined,
+      addedOn: slot.added ? new Date(slot.added * 1000).toISOString() : undefined,
+      arrQueueId: arrInfo.queueId,
+      arrType: arrInfo.type,
+      raw: { ...slot, source }
+    };
+  }
+
+  getUnitMultiplier(unit) {
+    const unitMap = {
+      'b': 1,
+      'byte': 1,
+      'bytes': 1,
+      'kb': 1024,
+      'k': 1024,
+      'mb': 1024 * 1024,
+      'm': 1024 * 1024,
+      'gb': 1024 * 1024 * 1024,
+      'g': 1024 * 1024 * 1024,
+      'tb': 1024 * 1024 * 1024 * 1024,
+      't': 1024 * 1024 * 1024 * 1024
+    };
+    return unitMap[unit.toLowerCase()] || 1;
+  }
+
+  calculateEta(timeLeft) {
+    if (!timeLeft || timeLeft === '0:00' || timeLeft === 'unknown') {
+      return null;
+    }
+
+    // Parse time in various formats: "0:05:30", "15:30", "330"
+    const parts = timeLeft.split(':').reverse();
+    let totalSeconds = 0;
+
+    if (parts.length === 1) {
+      // Just seconds
+      totalSeconds = parseInt(parts[0], 10);
+    } else if (parts.length === 2) {
+      // MM:SS
+      totalSeconds = parseInt(parts[0], 10) + parseInt(parts[1], 10) * 60;
+    } else if (parts.length === 3) {
+      // HH:MM:SS
+      totalSeconds = parseInt(parts[0], 10) + parseInt(parts[1], 10) * 60 + parseInt(parts[2], 10) * 3600;
+    }
+
+    return isNaN(totalSeconds) ? null : totalSeconds;
+  }
+
+  extractArrInfo(filename) {
+    // Try to extract Sonarr/Radarr info from filename patterns
+    // This is a simple implementation - could be enhanced with regex patterns
+    
+    // Look for patterns like "Series Name - S01E02 - Episode Title"
+    const seriesMatch = filename.match(/[-\s]S(\d{2})E(\d{2})/i);
+    if (seriesMatch) {
+      return { type: 'series' };
+    }
+
+    // Look for movie year patterns like "Movie Title (2023)"
+    const movieMatch = filename.match(/\((\d{4})\)/);
+    if (movieMatch && !seriesMatch) {
+      return { type: 'movie' };
+    }
+
+    return {};
+  }
+}
+
+module.exports = SABnzbdClient;

server/clients/TransmissionClient.js

@@ -0,0 +1,181 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+const axios = require('axios');
+const DownloadClient = require('./DownloadClient');
+const { logToFile } = require('../utils/logger');
+
+class TransmissionClient extends DownloadClient {
+  constructor(instance) {
+    super(instance);
+    this.sessionId = null;
+    this.rpcUrl = `${this.url}/transmission/rpc`;
+  }
+
+  getClientType() {
+    return 'transmission';
+  }
+
+  async testConnection() {
+    try {
+      await this.makeRequest('session-get');
+      logToFile(`[Transmission:${this.name}] Connection test successful`);
+      return true;
+    } catch (error) {
+      logToFile(`[Transmission:${this.name}] Connection test failed: ${error.message}`);
+      return false;
+    }
+  }
+
+  async makeRequest(method, arguments_ = {}, config = {}) {
+    const payload = {
+      method,
+      arguments: arguments_
+    };
+
+    const headers = {
+      'Content-Type': 'application/json'
+    };
+
+    if (this.sessionId) {
+      headers['X-Transmission-Session-Id'] = this.sessionId;
+    }
+
+    try {
+      const response = await axios.post(this.rpcUrl, payload, {
+        headers,
+        ...config
+      });
+
+      if (response.data.result !== 'success') {
+        throw new Error(`Transmission RPC error: ${response.data.result}`);
+      }
+
+      return response;
+    } catch (error) {
+      // Handle session ID conflict (409 Conflict)
+      if (error.response && error.response.status === 409) {
+        const sessionId = error.response.headers['x-transmission-session-id'];
+        if (sessionId) {
+          this.sessionId = sessionId;
+          logToFile(`[Transmission:${this.name}] Updated session ID`);
+          return this.makeRequest(method, arguments_, config);
+        }
+      }
+      logToFile(`[Transmission:${this.name}] RPC request failed: ${error.message}`);
+      throw error;
+    }
+  }
+
+  async getActiveDownloads() {
+    try {
+      // Get all torrents with detailed fields
+      const response = await this.makeRequest('torrent-get', {
+        fields: [
+          'id', 'name', 'hashString', 'status', 'totalSize', 'sizeWhenDone',
+          'leftUntilDone', 'rateDownload', 'rateUpload', 'eta', 'downloadedEver',
+          'uploadedEver', 'percentDone', 'addedDate', 'doneDate', 'trackerStats',
+          'labels', 'downloadDir', 'error', 'errorString', 'peersConnected',
+          'peersGettingFromUs', 'peersSendingToUs', 'queuePosition'
+        ]
+      });
+
+      const torrents = response.data.arguments.torrents || [];
+      logToFile(`[Transmission:${this.name}] Retrieved ${torrents.length} torrents`);
+      
+      return torrents.map(torrent => this.normalizeDownload(torrent));
+    } catch (error) {
+      logToFile(`[Transmission:${this.name}] Error fetching torrents: ${error.message}`);
+      return [];
+    }
+  }
+
+  async getClientStatus() {
+    try {
+      const response = await this.makeRequest('session-get');
+      const sessionStats = await this.makeRequest('session-stats');
+      
+      return {
+        session: response.data.arguments,
+        stats: sessionStats.data.arguments
+      };
+    } catch (error) {
+      logToFile(`[Transmission:${this.name}] Error getting client status: ${error.message}`);
+      return null;
+    }
+  }
+
+  normalizeDownload(torrent) {
+    // Map Transmission status codes to normalized status
+    const statusMap = {
+      0: 'Stopped',      // TORRENT_STOPPED
+      1: 'Queued',       // TORRENT_CHECK_WAIT
+      2: 'Checking',     // TORRENT_CHECK
+      3: 'Queued',       // TORRENT_DOWNLOAD_WAIT
+      4: 'Downloading',  // TORRENT_DOWNLOAD
+      5: 'Queued',       // TORRENT_SEED_WAIT
+      6: 'Seeding',      // TORRENT_SEED
+      7: 'Unknown'       // TORRENT_IS_CHECKING (alias for 2)
+    };
+
+    const status = statusMap[torrent.status] || 'Unknown';
+
+    // Calculate progress and sizes
+    const progress = torrent.percentDone * 100;
+    const size = torrent.totalSize;
+    const downloaded = torrent.sizeWhenDone - torrent.leftUntilDone;
+
+    // Handle ETA - Transmission uses -1 for unknown, -2 for infinite
+    let eta = null;
+    if (torrent.eta >= 0) {
+      eta = torrent.eta;
+    }
+
+    // Extract category/labels
+    const labels = torrent.labels || [];
+    const category = labels.length > 0 ? labels[0] : undefined;
+
+    // Try to extract Sonarr/Radarr info from name
+    const arrInfo = this.extractArrInfo(torrent.name);
+
+    return {
+      id: torrent.hashString,
+      title: torrent.name,
+      type: 'torrent',
+      client: 'transmission',
+      instanceId: this.id,
+      instanceName: this.name,
+      status: status,
+      progress: Math.round(progress),
+      size: size,
+      downloaded: downloaded,
+      speed: torrent.rateDownload,
+      eta: eta,
+      category: category,
+      tags: labels,
+      savePath: torrent.downloadDir || undefined,
+      addedOn: torrent.addedDate ? new Date(torrent.addedDate * 1000).toISOString() : undefined,
+      arrQueueId: arrInfo.queueId,
+      arrType: arrInfo.type,
+      raw: torrent
+    };
+  }
+
+  extractArrInfo(filename) {
+    // Similar to SABnzbdClient, try to extract Sonarr/Radarr info
+    
+    // Look for patterns like "Series Name - S01E02 - Episode Title"
+    const seriesMatch = filename.match(/[-\s]S(\d{2})E(\d{2})/i);
+    if (seriesMatch) {
+      return { type: 'series' };
+    }
+
+    // Look for movie year patterns like "Movie Title (2023)"
+    const movieMatch = filename.match(/\((\d{4})\)/);
+    if (movieMatch && !seriesMatch) {
+      return { type: 'movie' };
+    }
+
+    return {};
+  }
+}
+
+module.exports = TransmissionClient;

server/utils/config.js

@@ -94,11 +94,33 @@ function getQbittorrentInstances() {
   );
 }
 
+function getTransmissionInstances() {
+  return parseInstances(
+    process.env.TRANSMISSION_INSTANCES,
+    process.env.TRANSMISSION_URL,
+    null, // no apiKey for Transmission
+    process.env.TRANSMISSION_USERNAME,
+    process.env.TRANSMISSION_PASSWORD
+  );
+}
+
+function getRtorrentInstances() {
+  return parseInstances(
+    process.env.RTORRENT_INSTANCES,
+    process.env.RTORRENT_URL,
+    null, // no apiKey for rtorrent
+    process.env.RTORRENT_USERNAME,
+    process.env.RTORRENT_PASSWORD
+  );
+}
+
 module.exports = {
   getSABnzbdInstances,
   getSonarrInstances,
   getRadarrInstances,
   getQbittorrentInstances,
+  getTransmissionInstances,
+  getRtorrentInstances,
   parseInstances,
   validateInstanceUrl
 };

server/utils/downloadClients.js

@@ -0,0 +1,254 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+const { logToFile } = require('./logger');
+const {
+  getSABnzbdInstances,
+  getQbittorrentInstances,
+  getTransmissionInstances,
+  getRtorrentInstances
+} = require('./config');
+
+// Import client classes
+const SABnzbdClient = require('../clients/SABnzbdClient');
+const QBittorrentClient = require('../clients/QBittorrentClient');
+const TransmissionClient = require('../clients/TransmissionClient');
+const RTorrentClient = require('../clients/RTorrentClient');
+
+// Client type mapping
+const clientClasses = {
+  sabnzbd: SABnzbdClient,
+  qbittorrent: QBittorrentClient,
+  transmission: TransmissionClient,
+  rtorrent: RTorrentClient
+};
+
+/**
+ * Registry and factory for download clients
+ */
+class DownloadClientRegistry {
+  constructor() {
+    this.clients = new Map();
+    this.initialized = false;
+  }
+
+  /**
+   * Initialize all configured download clients
+   */
+  async initialize() {
+    if (this.initialized) {
+      return;
+    }
+
+    logToFile('[DownloadClientRegistry] Initializing download clients...');
+
+    // Get all instance configurations
+    const sabnzbdInstances = getSABnzbdInstances();
+    const qbittorrentInstances = getQbittorrentInstances();
+    const transmissionInstances = getTransmissionInstances();
+    const rtorrentInstances = getRtorrentInstances();
+
+    // Create client instances
+    const instanceConfigs = [
+      ...sabnzbdInstances.map(inst => ({ ...inst, type: 'sabnzbd' })),
+      ...qbittorrentInstances.map(inst => ({ ...inst, type: 'qbittorrent' })),
+      ...transmissionInstances.map(inst => ({ ...inst, type: 'transmission' })),
+      ...rtorrentInstances.map(inst => ({ ...inst, type: 'rtorrent' }))
+    ];
+
+    for (const config of instanceConfigs) {
+      try {
+        const ClientClass = clientClasses[config.type];
+        if (!ClientClass) {
+          logToFile(`[DownloadClientRegistry] Unknown client type: ${config.type}`);
+          continue;
+        }
+
+        const client = new ClientClass(config);
+        this.clients.set(config.id, client);
+        logToFile(`[DownloadClientRegistry] Created ${config.type} client: ${config.name} (${config.id})`);
+      } catch (error) {
+        logToFile(`[DownloadClientRegistry] Failed to create client ${config.id}: ${error.message}`);
+      }
+    }
+
+    this.initialized = true;
+    logToFile(`[DownloadClientRegistry] Initialized ${this.clients.size} download clients`);
+  }
+
+  /**
+   * Get all registered clients
+   * @returns {Array<DownloadClient>} Array of client instances
+   */
+  getAllClients() {
+    return Array.from(this.clients.values());
+  }
+
+  /**
+   * Get client by instance ID
+   * @param {string} instanceId - The instance ID
+   * @returns {DownloadClient|null} Client instance or null if not found
+   */
+  getClient(instanceId) {
+    return this.clients.get(instanceId) || null;
+  }
+
+  /**
+   * Get clients by type
+   * @param {string} type - Client type ('sabnzbd', 'qbittorrent', 'transmission')
+   * @returns {Array<DownloadClient>} Array of client instances
+   */
+  getClientsByType(type) {
+    return this.getAllClients().filter(client => client.getClientType() === type);
+  }
+
+  /**
+   * Get active downloads from all clients
+   * @returns {Promise<Array<NormalizedDownload>>} Array of all downloads
+   */
+  async getAllDownloads() {
+    const clients = this.getAllClients();
+    if (clients.length === 0) {
+      return [];
+    }
+
+    // Reset fallback flags for qBittorrent clients
+    for (const client of clients) {
+      if (client.resetFallbackFlag) {
+        client.resetFallbackFlag();
+      }
+    }
+
+    // Fetch downloads from all clients in parallel
+    const results = await Promise.allSettled(
+      clients.map(async (client) => {
+        try {
+          const downloads = await client.getActiveDownloads();
+          logToFile(`[DownloadClientRegistry] ${client.name}: ${downloads.length} downloads`);
+          return downloads;
+        } catch (error) {
+          logToFile(`[DownloadClientRegistry] Error fetching from ${client.name}: ${error.message}`);
+          return [];
+        }
+      })
+    );
+
+    // Flatten and return all downloads
+    const allDownloads = results
+      .filter(result => result.status === 'fulfilled')
+      .flatMap(result => result.value);
+
+    logToFile(`[DownloadClientRegistry] Total downloads from all clients: ${allDownloads.length}`);
+    return allDownloads;
+  }
+
+  /**
+   * Get downloads grouped by client type (for backward compatibility)
+   * @returns {Promise<Object>} Downloads grouped by client type
+   */
+  async getDownloadsByClientType() {
+    const clients = this.getAllClients();
+    const result = {};
+
+    // Group by client type
+    for (const client of clients) {
+      const type = client.getClientType();
+      if (!result[type]) {
+        result[type] = [];
+      }
+
+      try {
+        const downloads = await client.getActiveDownloads();
+        result[type].push(...downloads);
+      } catch (error) {
+        logToFile(`[DownloadClientRegistry] Error fetching from ${client.name}: ${error.message}`);
+      }
+    }
+
+    return result;
+  }
+
+  /**
+   * Test connection to all clients
+   * @returns {Promise<Array<Object>>} Array of connection test results
+   */
+  async testAllConnections() {
+    const clients = this.getAllClients();
+    const results = await Promise.allSettled(
+      clients.map(async (client) => {
+        try {
+          const success = await client.testConnection();
+          return {
+            instanceId: client.getInstanceId(),
+            instanceName: client.name,
+            clientType: client.getClientType(),
+            success,
+            error: null
+          };
+        } catch (error) {
+          return {
+            instanceId: client.getInstanceId(),
+            instanceName: client.name,
+            clientType: client.getClientType(),
+            success: false,
+            error: error.message
+          };
+        }
+      })
+    );
+
+    return results
+      .filter(result => result.status === 'fulfilled')
+      .map(result => result.value);
+  }
+
+  /**
+   * Get client status information from all clients
+   * @returns {Promise<Array<Object>>} Array of client status objects
+   */
+  async getAllClientStatuses() {
+    const clients = this.getAllClients();
+    const results = await Promise.allSettled(
+      clients.map(async (client) => {
+        try {
+          const status = await client.getClientStatus();
+          return {
+            instanceId: client.getInstanceId(),
+            instanceName: client.name,
+            clientType: client.getClientType(),
+            status
+          };
+        } catch (error) {
+          logToFile(`[DownloadClientRegistry] Error getting status from ${client.name}: ${error.message}`);
+          return {
+            instanceId: client.getInstanceId(),
+            instanceName: client.name,
+            clientType: client.getClientType(),
+            status: null,
+            error: error.message
+          };
+        }
+      })
+    );
+
+    return results
+      .filter(result => result.status === 'fulfilled')
+      .map(result => result.value);
+  }
+}
+
+// Create singleton instance
+const registry = new DownloadClientRegistry();
+
+module.exports = {
+  DownloadClientRegistry,
+  registry,
+  
+  // Convenience functions
+  initializeClients: () => registry.initialize(),
+  getAllClients: () => registry.getAllClients(),
+  getClient: (instanceId) => registry.getClient(instanceId),
+  getClientsByType: (type) => registry.getClientsByType(type),
+  getAllDownloads: () => registry.getAllDownloads(),
+  getDownloadsByClientType: () => registry.getDownloadsByClientType(),
+  testAllConnections: () => registry.testAllConnections(),
+  getAllClientStatuses: () => registry.getAllClientStatuses()
+};

server/utils/poller.js

@@ -1,9 +1,8 @@
 // Copyright (c) 2026 Gordon Bolton. MIT License.
 const axios = require('axios');
 const cache = require('./cache');
-const { getTorrents } = require('./qbittorrent');
+const { initializeClients, getAllDownloads, getDownloadsByClientType } = require('./downloadClients');
 const {
-  getSABnzbdInstances,
   getSonarrInstances,
   getRadarrInstances
 } = require('./config');
@@ -39,28 +38,18 @@ async function pollAllServices() {
   const start = Date.now();
 
   try {
-    const sabInstances = getSABnzbdInstances();
+    // Ensure download clients are initialized
+    await initializeClients();
+
     const sonarrInstances = getSonarrInstances();
     const radarrInstances = getRadarrInstances();
 
     // All fetches in parallel, each individually timed
     const results = await Promise.all([
-      timed('SABnzbd Queue', () => Promise.all(sabInstances.map(inst =>
+      timed('Download Clients', async () => {
-        axios.get(`${inst.url}/api`, {
+        const downloadsByType = await getDownloadsByClientType();
-          params: { mode: 'queue', apikey: inst.apiKey, output: 'json' }
+        return downloadsByType;
-        }).then(res => ({ instance: inst.id, data: res.data })).catch(err => {
+      }),
-          console.error(`[Poller] SABnzbd ${inst.id} queue error:`, err.message);
-          return { instance: inst.id, data: { queue: { slots: [] } } };
-        })
-      ))),
-      timed('SABnzbd History', () => Promise.all(sabInstances.map(inst =>
-        axios.get(`${inst.url}/api`, {
-          params: { mode: 'history', apikey: inst.apiKey, output: 'json', limit: 10 }
-        }).then(res => ({ instance: inst.id, data: res.data })).catch(err => {
-          console.error(`[Poller] SABnzbd ${inst.id} history error:`, err.message);
-          return { instance: inst.id, data: { history: { slots: [] } } };
-        })
-      ))),
       timed('Sonarr Tags', () => Promise.all(sonarrInstances.map(inst =>
         axios.get(`${inst.url}/api/v3/tag`, {
           headers: { 'X-Api-Key': inst.apiKey }
@@ -113,19 +102,14 @@ async function pollAllServices() {
           return { instance: inst.id, data: [] };
         })
       ))),
-      timed('qBittorrent', () => getTorrents().catch(err => {
-        console.error(`[Poller] qBittorrent error:`, err.message);
-        return [];
-      }))
     ]);
 
     const [
-      { result: sabQueues }, { result: sabHistories },
+      { result: downloadsByType },
       { result: sonarrTagsResults }, { result: sonarrQueues },
       { result: sonarrHistories },
       { result: radarrQueues }, { result: radarrHistories },
-      { result: radarrTagsResults },
+      { result: radarrTagsResults }
-      { result: qbittorrentTorrents }
     ] = results;
 
     // Store per-task timings
@@ -140,18 +124,69 @@ async function pollAllServices() {
     // When polling is disabled (on-demand), use 30s so data refreshes on next request after expiry
     const cacheTTL = POLLING_ENABLED ? POLL_INTERVAL * 3 : 30000;
 
-    // SABnzbd
+    // Download Clients (SABnzbd, qBittorrent, Transmission)
-    const firstSabQueue = sabQueues[0] && sabQueues[0].data && sabQueues[0].data.queue;
+    // Preserve backward compatibility with existing cache keys
+    const sabnzbdDownloads = downloadsByType.sabnzbd || [];
+    const qbittorrentDownloads = downloadsByType.qbittorrent || [];
+    
+    // SABnzbd - separate queue and history based on source
+    const sabQueue = sabnzbdDownloads.filter(d => d.raw && d.raw.source === 'queue');
+    const sabHistory = sabnzbdDownloads.filter(d => d.raw && d.raw.source === 'history');
+    
+    // Transform SABnzbd downloads to legacy format for cache
+    const sabQueueLegacy = {
+      slots: sabQueue.map(d => ({
+        nzo_id: d.id,
+        filename: d.title,
+        status: d.status,
+        progress: d.progress / 100,
+        mb: d.size / (1024 * 1024),
+        mbleft: (d.size - d.downloaded) / (1024 * 1024),
+        kbpersec: d.speed / 1024,
+        timeleft: d.eta ? `${Math.floor(d.eta / 60)}:${String(Math.floor(d.eta % 60)).padStart(2, '0')}` : 'unknown',
+        cat: d.category,
+        labels: d.tags.join(','),
+        added: d.addedOn ? Math.floor(new Date(d.addedOn).getTime() / 1000) : null,
+        raw: d.raw
+      }))
+    };
+    
+    const sabHistoryLegacy = {
+      slots: sabHistory.map(d => ({
+        nzo_id: d.id,
+        filename: d.title,
+        status: d.status,
+        mb: d.size / (1024 * 1024),
+        cat: d.category,
+        labels: d.tags.join(','),
+        added: d.addedOn ? Math.floor(new Date(d.addedOn).getTime() / 1000) : null,
+        raw: d.raw
+      }))
+    };
+    
+    // Extract status from first SABnzbd download if available
+    const firstSabDownload = sabQueue[0];
+    const sabStatus = firstSabDownload ? {
+      status: 'Active',
+      speed: firstSabDownload.speed,
+      kbpersec: firstSabDownload.speed / 1024
+    } : { status: 'Idle', speed: 0, kbpersec: 0 };
+    
     cache.set('poll:sab-queue', {
-      slots: sabQueues.flatMap(q => (q.data.queue && q.data.queue.slots) || []),
+      ...sabQueueLegacy,
-      status: firstSabQueue && firstSabQueue.status,
+      ...sabStatus
-      speed: firstSabQueue && firstSabQueue.speed,
-      kbpersec: firstSabQueue && firstSabQueue.kbpersec
     }, cacheTTL);
     
-    cache.set('poll:sab-history', {
+    cache.set('poll:sab-history', sabHistoryLegacy, cacheTTL);
-      slots: sabHistories.flatMap(h => (h.data.history && h.data.history.slots) || [])
+    
-    }, cacheTTL);
+    // qBittorrent - transform to legacy format
+    const qbittorrentLegacy = qbittorrentDownloads.map(d => ({
+      ...d.raw,
+      instanceId: d.instanceId,
+      instanceName: d.instanceName
+    }));
+    
+    cache.set('poll:qbittorrent', qbittorrentLegacy, cacheTTL);
 
     // Sonarr
     cache.set('poll:sonarr-tags', sonarrTagsResults, cacheTTL);
@@ -192,8 +227,7 @@ async function pollAllServices() {
     }, cacheTTL);
     cache.set('poll:radarr-tags', radarrTagsResults.flatMap(t => t.data || []), cacheTTL);
 
-    // qBittorrent
+    // qBittorrent (already set above in download clients section)
-    cache.set('poll:qbittorrent', qbittorrentTorrents, cacheTTL);
 
     const elapsed = Date.now() - start;
     console.log(`[Poller] Poll complete in ${elapsed}ms`);

server/utils/qbittorrent.js

@@ -1,234 +1,47 @@
 // Copyright (c) 2026 Gordon Bolton. MIT License.
-const axios = require('axios');
+// Legacy compatibility layer - delegates to new DownloadClient system
 const { logToFile } = require('./logger');
-const { getQbittorrentInstances } = require('./config');
+const { initializeClients, getClientsByType } = require('./downloadClients');
-
-class QBittorrentClient {
-  constructor(instance) {
-    this.id = instance.id;
-    this.name = instance.name;
-    this.url = instance.url;
-    this.username = instance.username;
-    this.password = instance.password;
-    this.authCookie = null;
-    // Sync API incremental state
-    this.lastRid = 0;
-    this.torrentMap = new Map();
-    this.fallbackThisCycle = false;
-  }
-
-  async login() {
-    try {
-      logToFile(`[qBittorrent:${this.name}] Attempting login...`);
-      const response = await axios.post(`${this.url}/api/v2/auth/login`, 
-        `username=${encodeURIComponent(this.username)}&password=${encodeURIComponent(this.password)}`,
-        {
-          headers: {
-            'Content-Type': 'application/x-www-form-urlencoded'
-          },
-          maxRedirects: 0,
-          validateStatus: (status) => status >= 200 && status < 400
-        }
-      );
-      
-      if (response.headers['set-cookie']) {
-        this.authCookie = response.headers['set-cookie'][0];
-        logToFile(`[qBittorrent:${this.name}] Login successful`);
-        return true;
-      }
-      
-      logToFile(`[qBittorrent:${this.name}] Login failed - no cookie`);
-      return false;
-    } catch (error) {
-      logToFile(`[qBittorrent:${this.name}] Login error: ${error.message}`);
-      return false;
-    }
-  }
-
-  async makeRequest(endpoint, config = {}) {
-    const url = `${this.url}${endpoint}`;
-    
-    if (!this.authCookie) {
-      const loggedIn = await this.login();
-      if (!loggedIn) {
-        throw new Error(`Failed to authenticate with ${this.name}`);
-      }
-    }
-    
-    try {
-      const response = await axios.get(url, {
-        ...config,
-        headers: {
-          ...config.headers,
-          'Cookie': this.authCookie
-        }
-      });
-      return response;
-    } catch (error) {
-      // If unauthorized, try re-authenticating once
-      if (error.response && error.response.status === 403) {
-        logToFile(`[qBittorrent:${this.name}] Auth expired, re-authenticating...`);
-        this.authCookie = null;
-        const loggedIn = await this.login();
-        if (loggedIn) {
-          return axios.get(url, {
-            ...config,
-            headers: {
-              ...config.headers,
-              'Cookie': this.authCookie
-            }
-          });
-        }
-      }
-      throw error;
-    }
-  }
-
-  /**
-   * Fetches incremental torrent data using the qBittorrent Sync API.
-   *
-   * The Sync API uses a response ID (rid) to send only changed fields:
-   *  - First call uses rid=0 to get the full torrent list.
-   *  - Subsequent calls send the last received rid; qBittorrent returns
-   *    delta updates (changed fields only), new torrents, and removed hashes.
-   *  - If full_update is true, the server is sending a full refresh and
-   *    we rebuild our local map from scratch.
-   *
-   * @returns {Promise<Array>} Array of complete torrent objects.
-   */
-  async getMainData() {
-    const response = await this.makeRequest(`/api/v2/sync/maindata?rid=${this.lastRid}`);
-    const data = response.data;
-
-    if (data.full_update) {
-      // Full refresh: rebuild the entire map
-      this.torrentMap.clear();
-      if (data.torrents) {
-        for (const [hash, props] of Object.entries(data.torrents)) {
-          this.torrentMap.set(hash, { ...props, hash });
-        }
-      }
-    } else {
-      // Delta update: merge changed fields into existing torrent objects
-      if (data.torrents) {
-        for (const [hash, delta] of Object.entries(data.torrents)) {
-          const existing = this.torrentMap.get(hash) || { hash };
-          this.torrentMap.set(hash, { ...existing, ...delta });
-        }
-      }
-    }
-
-    // Remove torrents that the server reports as deleted
-    if (data.torrents_removed) {
-      for (const hash of data.torrents_removed) {
-        this.torrentMap.delete(hash);
-      }
-    }
-
-    // Ensure every torrent has a computed 'completed' field for downstream consumers
-    for (const torrent of this.torrentMap.values()) {
-      if (torrent.completed === undefined && torrent.size !== undefined && torrent.progress !== undefined) {
-        torrent.completed = Math.round(torrent.size * torrent.progress);
-      }
-    }
-
-    this.lastRid = data.rid;
-    return Array.from(this.torrentMap.values());
-  }
-
-  /**
-   * Legacy full-list fetch. Used as a fallback when the Sync API fails.
-   */
-  async getTorrentsLegacy() {
-    try {
-      const response = await this.makeRequest('/api/v2/torrents/info');
-      logToFile(`[qBittorrent:${this.name}] Retrieved ${response.data.length} torrents (legacy)`);
-      return response.data;
-    } catch (error) {
-      logToFile(`[qBittorrent:${this.name}] Error fetching torrents (legacy): ${error.message}`);
-      throw error;
-    }
-  }
-
-  /**
-   * Returns the current list of torrents for this instance.
-   * Uses the Sync API for incremental updates; falls back to torrents/info
-   * at most once per polling cycle if the Sync API call fails.
-   */
-  async getTorrents() {
-    try {
-      if (this.fallbackThisCycle) {
-        logToFile(`[qBittorrent:${this.name}] Already fell back this cycle, using legacy`);
-        const torrents = await this.getTorrentsLegacy();
-        return torrents.map(torrent => ({
-          ...torrent,
-          instanceId: this.id,
-          instanceName: this.name
-        }));
-      }
-
-      const torrents = await this.getMainData();
-      logToFile(`[qBittorrent:${this.name}] Sync: ${torrents.length} torrents (rid=${this.lastRid})`);
-      return torrents.map(torrent => ({
-        ...torrent,
-        instanceId: this.id,
-        instanceName: this.name
-      }));
-    } catch (error) {
-      logToFile(`[qBittorrent:${this.name}] Sync failed, falling back to legacy: ${error.message}`);
-      this.fallbackThisCycle = true;
-      try {
-        const torrents = await this.getTorrentsLegacy();
-        return torrents.map(torrent => ({
-          ...torrent,
-          instanceId: this.id,
-          instanceName: this.name
-        }));
-      } catch (fallbackError) {
-        logToFile(`[qBittorrent:${this.name}] Fallback also failed: ${fallbackError.message}`);
-        return [];
-      }
-    }
-  }
-}
-
-// Persist clients so auth cookies survive between requests
-let persistedClients = null;
-
-function getClients() {
-  if (persistedClients) return persistedClients;
-  const instances = getQbittorrentInstances();
-  if (instances.length === 0) {
-    logToFile('[qBittorrent] No instances configured');
-    return [];
-  }
-  logToFile(`[qBittorrent] Created ${instances.length} persistent client(s)`);
-  persistedClients = instances.map(inst => new QBittorrentClient(inst));
-  return persistedClients;
-}
 
+/**
+ * Legacy function for backward compatibility
+ * Returns all torrents from all qBittorrent instances
+ */
 async function getAllTorrents() {
-  const clients = getClients();
+  try {
-  if (clients.length === 0) {
+    await initializeClients();
+    const clients = getClientsByType('qbittorrent');
+    
+    if (clients.length === 0) {
+      logToFile('[qBittorrent] No instances configured');
+      return [];
+    }
+
+    const results = await Promise.all(
+      clients.map(client => client.getActiveDownloads().catch(err => {
+        logToFile(`[qBittorrent] Error from ${client.name}: ${err.message}`);
+        return [];
+      }))
+    );
+    
+    const allTorrents = results.flat();
+    // Convert back to legacy format for backward compatibility
+    const legacyTorrents = allTorrents.map(download => download.raw);
+    
+    logToFile(`[qBittorrent] Total torrents from all instances: ${legacyTorrents.length}`);
+    return legacyTorrents;
+  } catch (error) {
+    logToFile(`[qBittorrent] Error in getAllTorrents: ${error.message}`);
     return [];
   }
+}
 
-  // Reset fallback flags at the start of each poll cycle so every cycle
+/**
-  // gets one chance to use the Sync API before falling back.
+ * Legacy function for backward compatibility
-  for (const client of clients) {
+ */
-    client.fallbackThisCycle = false;
+function getClients() {
-  }
+  logToFile('[qBittorrent] getClients() called - delegating to new system');
-
+  return []; // Not used in new system
-  const results = await Promise.all(
-    clients.map(client => client.getTorrents().catch(err => {
-      logToFile(`[qBittorrent] Error from ${client.name}: ${err.message}`);
-      return [];
-    }))
-  );
-  
-  const allTorrents = results.flat();
-  logToFile(`[qBittorrent] Total torrents from all instances: ${allTorrents.length}`);
-  return allTorrents;
 }
 
 function formatBytes(bytes) {
@@ -312,11 +125,10 @@ function mapTorrentToDownload(torrent) {
 }
 
 module.exports = {
-  getTorrents: getAllTorrents,
+  getAllTorrents,
   getClients,
   mapTorrentToDownload,
   formatBytes,
   formatSpeed,
-  formatEta,
+  formatEta
-  QBittorrentClient
 };

tests/integration/downloadClients.test.js

@@ -0,0 +1,300 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+import {
+  initializeClients,
+  getAllDownloads,
+  getDownloadsByClientType,
+  testAllConnections,
+  registry
+} from '../../server/utils/downloadClients.js';
+import axios from 'axios';
+import { vi } from 'vitest';
+
+// Mock environment variables for testing
+process.env.SABNZBD_INSTANCES = JSON.stringify([
+  {
+    id: 'test-sab',
+    name: 'Test SABnzbd',
+    url: 'http://localhost:8080',
+    apiKey: 'test-api-key'
+  }
+]);
+
+process.env.QBITTORRENT_INSTANCES = JSON.stringify([
+  {
+    id: 'test-qb',
+    name: 'Test qBittorrent',
+    url: 'http://localhost:8080',
+    username: 'admin',
+    password: 'adminadmin'
+  }
+]);
+
+process.env.TRANSMISSION_INSTANCES = JSON.stringify([
+  {
+    id: 'test-trans',
+    name: 'Test Transmission',
+    url: 'http://localhost:9091',
+    username: 'transmission',
+    password: 'transmission'
+  }
+]);
+
+process.env.RTORRENT_INSTANCES = JSON.stringify([
+  {
+    id: 'test-rtorrent',
+    name: 'Test rTorrent',
+    url: 'http://localhost:8080/RPC2',
+    username: 'rtorrent',
+    password: 'rtorrent'
+  }
+]);
+
+// Mock axios to prevent actual network calls
+vi.mock('axios', () => {
+  const mockAxios = vi.fn();
+  mockAxios.post = vi.fn();
+  mockAxios.get = vi.fn();
+  return {
+    default: mockAxios,
+    post: vi.fn(),
+    get: vi.fn()
+  };
+});
+vi.mock('../../server/utils/logger', () => ({
+  logToFile: vi.fn()
+}));
+
+describe('Download Clients Integration Tests', () => {
+  beforeEach(() => {
+    registry.initialized = false;
+    registry.clients.clear();
+    vi.clearAllMocks();
+  });
+
+  describe('Client Initialization', () => {
+    it('should initialize all configured client types', async () => {
+      await initializeClients();
+      
+      // The registry should have clients for all three types
+      const downloadsByType = await getDownloadsByClientType();
+      
+      // Should have keys for each client type (even if empty due to mocked failures)
+      expect(typeof downloadsByType).toBe('object');
+    });
+
+    it('should handle missing environment variables gracefully', async () => {
+      // Temporarily clear environment variables
+      const originalSab = process.env.SABNZBD_INSTANCES;
+      const originalQb = process.env.QBITTORRENT_INSTANCES;
+      const originalTrans = process.env.TRANSMISSION_INSTANCES;
+      const originalRt = process.env.RTORRENT_INSTANCES;
+      
+      delete process.env.SABNZBD_INSTANCES;
+      delete process.env.QBITTORRENT_INSTANCES;
+      delete process.env.TRANSMISSION_INSTANCES;
+      delete process.env.RTORRENT_INSTANCES;
+      
+      await initializeClients();
+      
+      const downloadsByType = await getDownloadsByClientType();
+      expect(Object.keys(downloadsByType)).toHaveLength(0);
+      
+      // Restore environment variables
+      process.env.SABNZBD_INSTANCES = originalSab;
+      process.env.QBITTORRENT_INSTANCES = originalQb;
+      process.env.TRANSMISSION_INSTANCES = originalTrans;
+      process.env.RTORRENT_INSTANCES = originalRt;
+    });
+  });
+
+  describe('Download Aggregation', () => {
+    it('should aggregate downloads from multiple client types', async () => {
+      await initializeClients();
+      
+      const downloadsByType = await getDownloadsByClientType();
+      const allDownloads = await getAllDownloads();
+      
+      // Should return downloads grouped by type
+      expect(typeof downloadsByType).toBe('object');
+      
+      // Should return flattened array of all downloads
+      expect(Array.isArray(allDownloads)).toBe(true);
+      
+      // All downloads should have required normalized fields
+      allDownloads.forEach(download => {
+        expect(download).toHaveProperty('id');
+        expect(download).toHaveProperty('title');
+        expect(download).toHaveProperty('type');
+        expect(download).toHaveProperty('client');
+        expect(download).toHaveProperty('instanceId');
+        expect(download).toHaveProperty('instanceName');
+        expect(download).toHaveProperty('status');
+        expect(download).toHaveProperty('progress');
+        expect(download).toHaveProperty('size');
+        expect(download).toHaveProperty('downloaded');
+        expect(download).toHaveProperty('speed');
+        expect(download).toHaveProperty('raw');
+      });
+    });
+
+    it('should maintain type consistency across clients', async () => {
+      await initializeClients();
+      
+      const downloadsByType = await getDownloadsByClientType();
+      
+      // Check that each client type returns consistent data structure
+      Object.entries(downloadsByType).forEach(([clientType, downloads]) => {
+        if (downloads.length > 0) {
+          downloads.forEach(download => {
+            expect(download.client).toBe(clientType);
+            expect(download.type).toMatch(/^(usenet|torrent)$/);
+            expect(typeof download.progress).toBe('number');
+            expect(download.progress).toBeGreaterThanOrEqual(0);
+            expect(download.progress).toBeLessThanOrEqual(100);
+            expect(typeof download.size).toBe('number');
+            expect(typeof download.downloaded).toBe('number');
+            expect(typeof download.speed).toBe('number');
+          });
+        }
+      });
+    });
+  });
+
+  describe('Connection Testing', () => {
+    it('should test connections for all configured clients', async () => {
+      await initializeClients();
+      
+      const results = await testAllConnections();
+      
+      expect(Array.isArray(results)).toBe(true);
+      
+      results.forEach(result => {
+        expect(result).toHaveProperty('instanceId');
+        expect(result).toHaveProperty('instanceName');
+        expect(result).toHaveProperty('clientType');
+        expect(result).toHaveProperty('success');
+        expect(typeof result.success).toBe('boolean');
+      });
+    });
+
+    it('should handle connection failures gracefully', async () => {
+      // This test verifies that connection failures don't crash the system
+      await initializeClients();
+      
+      const results = await testAllConnections();
+      
+      // Should still return results even if connections fail
+      expect(results.length).toBeGreaterThan(0);
+    });
+  });
+
+  describe('Error Handling and Resilience', () => {
+    it('should handle individual client failures without affecting others', async () => {
+      await initializeClients();
+      
+      // Even if some clients fail, others should still work
+      const downloadsByType = await getDownloadsByClientType();
+      const allDownloads = await getAllDownloads();
+      
+      expect(typeof downloadsByType).toBe('object');
+      expect(Array.isArray(allDownloads)).toBe(true);
+    });
+
+    it('should handle malformed configuration gracefully', async () => {
+      // Test with malformed JSON
+      const originalSab = process.env.SABNZBD_INSTANCES;
+      process.env.SABNZBD_INSTANCES = 'invalid-json{';
+      
+      // Should not throw an error
+      await expect(initializeClients()).resolves.not.toThrow();
+      
+      // Restore
+      process.env.SABNZBD_INSTANCES = originalSab;
+    });
+
+    it('should handle network timeouts and errors', async () => {
+      await initializeClients();
+      
+      // Mock network failures by setting up axios to reject
+      axios.get.mockRejectedValue(new Error('Network timeout'));
+      axios.post.mockRejectedValue(new Error('Network timeout'));
+      
+      // Should handle errors gracefully and return empty results
+      const downloads = await getAllDownloads();
+      expect(Array.isArray(downloads)).toBe(true);
+    });
+  });
+
+  describe('Backward Compatibility', () => {
+    it('should maintain compatibility with existing cache structure', async () => {
+      await initializeClients();
+      
+      const downloadsByType = await getDownloadsByClientType();
+      
+      // SABnzbd downloads should have raw data for legacy compatibility
+      if (downloadsByType.sabnzbd && downloadsByType.sabnzbd.length > 0) {
+        downloadsByType.sabnzbd.forEach(download => {
+          expect(download.raw).toBeTruthy();
+          expect(download.raw.source).toMatch(/^(queue|history)$/);
+        });
+      }
+      
+      // qBittorrent downloads should have raw data for legacy compatibility
+      if (downloadsByType.qbittorrent && downloadsByType.qbittorrent.length > 0) {
+        downloadsByType.qbittorrent.forEach(download => {
+          expect(download.raw).toBeTruthy();
+          expect(download.raw.hash).toBeTruthy(); // qBittorrent specific field
+        });
+      }
+    });
+  });
+
+  describe('Performance and Scalability', () => {
+    it('should handle multiple instances of the same client type', async () => {
+      // Configure multiple instances
+      process.env.QBITTORRENT_INSTANCES = JSON.stringify([
+        {
+          id: 'test-qb-1',
+          name: 'Test qBittorrent 1',
+          url: 'http://localhost:8080',
+          username: 'admin',
+          password: 'adminadmin'
+        },
+        {
+          id: 'test-qb-2',
+          name: 'Test qBittorrent 2',
+          url: 'http://localhost:8081',
+          username: 'admin',
+          password: 'adminadmin'
+        }
+      ]);
+      
+      await initializeClients();
+      
+      const downloadsByType = await getDownloadsByClientType();
+      
+      // Should aggregate downloads from both instances
+      expect(Array.isArray(downloadsByType.qbittorrent)).toBe(true);
+      
+      // Each download should have correct instance information
+      downloadsByType.qbittorrent.forEach(download => {
+        expect(download.instanceId).toMatch(/^(test-qb-1|test-qb-2)$/);
+        expect(download.instanceName).toMatch(/^(Test qBittorrent 1|Test qBittorrent 2)$/);
+      });
+    });
+
+    it('should execute client requests in parallel', async () => {
+      const startTime = Date.now();
+      
+      await initializeClients();
+      await getAllDownloads();
+      
+      const endTime = Date.now();
+      const duration = endTime - startTime;
+      
+      // This is a rough check - in a real scenario with actual network calls,
+      // parallel execution should be significantly faster than sequential
+      expect(duration).toBeGreaterThan(0);
+    });
+  });
+});

tests/unit/clients/DownloadClient.test.js

@@ -0,0 +1,77 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+const DownloadClient = require('../../../server/clients/DownloadClient');
+
+describe('DownloadClient', () => {
+  describe('Abstract Base Class', () => {
+    it('should throw error when instantiated directly', () => {
+      expect(() => {
+        new DownloadClient({ id: 'test', name: 'Test', url: 'http://test.com' });
+      }).toThrow('DownloadClient is an abstract class and cannot be instantiated directly');
+    });
+
+    it('should enforce implementation of required methods', () => {
+      class TestClient extends DownloadClient {
+        getClientType() {
+          return 'test';
+        }
+      }
+
+      const client = new TestClient({ id: 'test', name: 'Test', url: 'http://test.com' });
+      
+      expect(() => client.testConnection()).rejects.toThrow('testConnection() must be implemented by subclass');
+      expect(() => client.getActiveDownloads()).rejects.toThrow('getActiveDownloads() must be implemented by subclass');
+      expect(() => client.normalizeDownload({})).toThrow('normalizeDownload() must be implemented by subclass');
+    });
+  });
+
+  describe('Base Properties', () => {
+    class TestClient extends DownloadClient {
+      getClientType() {
+        return 'test';
+      }
+      
+      async testConnection() {
+        return true;
+      }
+      
+      async getActiveDownloads() {
+        return [];
+      }
+      
+      normalizeDownload(download) {
+        return download;
+      }
+    }
+
+    it('should set basic properties from config', () => {
+      const config = {
+        id: 'test-instance',
+        name: 'Test Instance',
+        url: 'http://test.com',
+        apiKey: 'test-key',
+        username: 'test-user',
+        password: 'test-pass'
+      };
+
+      const client = new TestClient(config);
+      
+      expect(client.id).toBe('test-instance');
+      expect(client.name).toBe('Test Instance');
+      expect(client.url).toBe('http://test.com');
+      expect(client.apiKey).toBe('test-key');
+      expect(client.username).toBe('test-user');
+      expect(client.password).toBe('test-pass');
+    });
+
+    it('should return correct instance ID', () => {
+      const client = new TestClient({ id: 'test-id', name: 'Test', url: 'http://test.com' });
+      expect(client.getInstanceId()).toBe('test-id');
+    });
+
+    it('should have optional getClientStatus method returning null', async () => {
+      const client = new TestClient({ id: 'test', name: 'Test', url: 'http://test.com' });
+      const status = await client.getClientStatus();
+      expect(status).toBeNull();
+    });
+  });
+});

tests/unit/clients/QBittorrentClient.test.js

@@ -0,0 +1,208 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+import QBittorrentClient from '../../../server/clients/QBittorrentClient.js';
+import nock from 'nock';
+import { vi } from 'vitest';
+
+vi.mock('../../../server/utils/logger', () => ({
+  logToFile: vi.fn()
+}));
+
+describe('QBittorrentClient', () => {
+  let client;
+  let mockConfig;
+
+  beforeEach(() => {
+    mockConfig = {
+      id: 'test-qb',
+      name: 'Test qBittorrent',
+      url: 'http://localhost:8080',
+      username: 'admin',
+      password: 'adminadmin'
+    };
+    
+    client = new QBittorrentClient(mockConfig);
+
+    // Clear all mocks
+    vi.clearAllMocks();
+  });
+
+  describe('Constructor', () => {
+    it('should initialize with correct properties', () => {
+      expect(client.getClientType()).toBe('qbittorrent');
+      expect(client.getInstanceId()).toBe('test-qb');
+      expect(client.name).toBe('Test qBittorrent');
+      expect(client.url).toBe('http://localhost:8080');
+      expect(client.authCookie).toBeNull();
+      expect(client.lastRid).toBe(0);
+      expect(client.torrentMap).toBeInstanceOf(Map);
+      expect(client.fallbackThisCycle).toBe(false);
+    });
+  });
+
+  describe('Authentication', () => {
+    it('should login successfully with valid credentials', async () => {
+      nock('http://localhost:8080')
+        .post('/api/v2/auth/login', 'username=admin&password=adminadmin')
+        .reply(200, {}, { 'set-cookie': ['SID=test-cookie'] });
+      
+      const result = await client.login();
+      
+      expect(result).toBe(true);
+      expect(client.authCookie).toBe('SID=test-cookie');
+    });
+
+    it('should handle login failure', async () => {
+      nock('http://localhost:8080')
+        .post('/api/v2/auth/login', 'username=admin&password=adminadmin')
+        .reply(200, {}, {});
+      
+      const result = await client.login();
+      
+      expect(result).toBe(false);
+      expect(client.authCookie).toBeNull();
+    });
+
+    it('should handle login error', async () => {
+      nock('http://localhost:8080')
+        .post('/api/v2/auth/login', 'username=admin&password=adminadmin')
+        .replyWithError(new Error('Network error'));
+      
+      const result = await client.login();
+      
+      expect(result).toBe(false);
+      expect(client.authCookie).toBeNull();
+    });
+  });
+
+  describe('Connection Test', () => {
+    it('should test connection successfully', async () => {
+      // Mock login success
+      client.login = vi.fn().mockResolvedValue(true);
+
+      // Mock version request
+      const mockResponse = { data: 'v4.3.5' };
+      client.makeRequest = vi.fn().mockResolvedValue(mockResponse);
+      
+      const result = await client.testConnection();
+      
+      expect(result).toBe(true);
+      expect(client.makeRequest).toHaveBeenCalledWith('/api/v2/app/version');
+    });
+
+    it('should handle connection test failure', async () => {
+      client.login = vi.fn().mockRejectedValue(new Error('Auth failed'));
+      
+      const result = await client.testConnection();
+      
+      expect(result).toBe(false);
+    });
+  });
+
+  describe('Download Normalization', () => {
+    it('should normalize torrent data correctly', () => {
+      const torrent = {
+        hash: 'abc123',
+        name: 'Test Torrent',
+        state: 'downloading',
+        progress: 0.75,
+        size: 1000000000,
+        completed: 750000000,
+        dlspeed: 1048576,
+        eta: 3600,
+        category: 'movies',
+        tags: 'movie,hd',
+        content_path: '/downloads/test',
+        added_on: 1640995200
+      };
+
+      const normalized = client.normalizeDownload(torrent);
+
+      expect(normalized).toEqual({
+        id: 'abc123',
+        title: 'Test Torrent',
+        type: 'torrent',
+        client: 'qbittorrent',
+        instanceId: 'test-qb',
+        instanceName: 'Test qBittorrent',
+        status: 'Downloading',
+        progress: 75,
+        size: 1000000000,
+        downloaded: 750000000,
+        speed: 1048576,
+        eta: 3600,
+        category: 'movies',
+        tags: ['movie', 'hd'],
+        savePath: '/downloads/test',
+        addedOn: '2022-01-01T00:00:00.000Z',
+        raw: torrent
+      });
+    });
+
+    it('should handle unknown torrent states', () => {
+      const torrent = {
+        hash: 'abc123',
+        name: 'Test Torrent',
+        state: 'unknown_state',
+        progress: 0.5,
+        size: 1000000,
+        completed: 500000,
+        dlspeed: 0,
+        eta: -1
+      };
+
+      const normalized = client.normalizeDownload(torrent);
+
+      expect(normalized.status).toBe('unknown_state');
+      expect(normalized.eta).toBeNull();
+    });
+
+    it('should handle missing completed field', () => {
+      const torrent = {
+        hash: 'abc123',
+        name: 'Test Torrent',
+        state: 'downloading',
+        progress: 0.5,
+        size: 1000000,
+        dlspeed: 0
+      };
+
+      const normalized = client.normalizeDownload(torrent);
+
+      expect(normalized.downloaded).toBe(500000);
+    });
+  });
+
+  describe('Fallback Flag Management', () => {
+    it('should reset fallback flag', () => {
+      client.fallbackThisCycle = true;
+      client.resetFallbackFlag();
+      expect(client.fallbackThisCycle).toBe(false);
+    });
+  });
+
+  describe('Error Handling', () => {
+    it('should handle makeRequest authentication failure', async () => {
+      client.authCookie = 'invalid-cookie';
+      
+      // First request fails with 403
+      nock('http://localhost:8080')
+        .get('/test')
+        .reply(403, {});
+
+      // Re-authentication succeeds
+      nock('http://localhost:8080')
+        .post('/api/v2/auth/login', 'username=admin&password=adminadmin')
+        .reply(200, {}, { 'set-cookie': ['SID=new-cookie'] });
+
+      // Retry succeeds
+      nock('http://localhost:8080')
+        .get('/test')
+        .reply(200, { data: 'success' });
+      
+      const result = await client.makeRequest('/test');
+      
+      expect(result.data).toEqual({ data: 'success' });
+      expect(client.authCookie).toBe('SID=new-cookie');
+    });
+  });
+});

tests/unit/clients/RTorrentClient.test.js

@@ -0,0 +1,423 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+import RTorrentClient from '../../../server/clients/RTorrentClient.js';
+import { vi } from 'vitest';
+
+vi.mock('../../../server/utils/logger', () => ({
+  logToFile: vi.fn()
+}));
+
+describe('RTorrentClient', () => {
+  let client;
+  let mockConfig;
+  let mockMethodCall;
+
+  beforeEach(() => {
+    mockMethodCall = vi.fn();
+
+    mockConfig = {
+      id: 'test-rtorrent',
+      name: 'Test rTorrent',
+      url: 'http://localhost:8080',
+      username: 'rtorrent',
+      password: 'rtorrent'
+    };
+
+    client = new RTorrentClient(mockConfig);
+    // Mock the xmlrpc client's methodCall directly
+    client.client.methodCall = mockMethodCall;
+  });
+
+  describe('Constructor', () => {
+    it('should initialize with correct properties', () => {
+      expect(client.getClientType()).toBe('rtorrent');
+      expect(client.getInstanceId()).toBe('test-rtorrent');
+      expect(client.name).toBe('Test rTorrent');
+      expect(client.url).toBe('http://localhost:8080');
+    });
+
+    it('should create xmlrpc client with correct URL', async () => {
+      expect(client.url).toBe('http://localhost:8080');
+      expect(client.client).toBeDefined();
+    });
+
+    it('should create xmlrpc client without auth when no credentials', () => {
+      const noAuthConfig = {
+        id: 'test-rtorrent-noauth',
+        name: 'Test rTorrent No Auth',
+        url: 'http://localhost:8080/RPC2'
+      };
+      const clientNoAuth = new RTorrentClient(noAuthConfig);
+      expect(clientNoAuth.client).toBeDefined();
+    });
+
+    it('should use whatbox.ca-style /xmlrpc path exactly as configured', () => {
+      const whatboxConfig = {
+        id: 'test-whatbox',
+        name: 'Whatbox',
+        url: 'https://user.whatbox.ca/xmlrpc',
+        username: 'user',
+        password: 'pass'
+      };
+      const clientWhatbox = new RTorrentClient(whatboxConfig);
+      expect(clientWhatbox.client).toBeDefined();
+    });
+
+    it('should use custom RPC path exactly as configured', () => {
+      const customConfig = {
+        id: 'test-custom',
+        name: 'Custom',
+        url: 'https://example.com/custom/rpc/path'
+      };
+      const clientCustom = new RTorrentClient(customConfig);
+      expect(clientCustom.client).toBeDefined();
+    });
+  });
+
+  describe('Connection Test', () => {
+    it('should test connection successfully', async () => {
+      mockMethodCall.mockImplementation((method, params, callback) => {
+        callback(null, '0.9.8');
+      });
+
+      const result = await client.testConnection();
+
+      expect(result).toBe(true);
+    });
+
+    it('should handle connection test failure', async () => {
+      mockMethodCall.mockImplementation((method, params, callback) => {
+        callback(new Error('Connection refused'));
+      });
+
+      const result = await client.testConnection();
+
+      expect(result).toBe(false);
+    });
+  });
+
+  describe('getActiveDownloads', () => {
+    it('should fetch and normalize torrents', async () => {
+      const mockTorrents = [
+        [
+          'abc123def456',
+          'Test Torrent 1',
+          1000000000,
+          750000000,
+          1048576,
+          0,
+          1,
+          1,
+          0,
+          '/downloads/test',
+          'movies'
+        ],
+        [
+          'def789abc012',
+          'Test Torrent 2',
+          2000000000,
+          2000000000,
+          0,
+          512000,
+          1,
+          1,
+          0,
+          '/downloads/complete',
+          'tv'
+        ]
+      ];
+
+      mockMethodCall.mockImplementation((method, params, callback) => {
+        callback(null, mockTorrents);
+      });
+
+      const downloads = await client.getActiveDownloads();
+
+      expect(downloads).toHaveLength(2);
+      expect(downloads[0].id).toBe('abc123def456');
+      expect(downloads[0].title).toBe('Test Torrent 1');
+      expect(downloads[0].status).toBe('Downloading');
+      expect(downloads[0].progress).toBe(75);
+      expect(downloads[0].category).toBe('movies');
+      expect(downloads[1].status).toBe('Seeding');
+      expect(downloads[1].category).toBe('tv');
+    });
+
+    it('should handle empty torrent list', async () => {
+      mockMethodCall.mockImplementation((method, params, callback) => {
+        callback(null, []);
+      });
+
+      const downloads = await client.getActiveDownloads();
+
+      expect(downloads).toEqual([]);
+    });
+
+    it('should handle XML-RPC errors gracefully', async () => {
+      mockMethodCall.mockImplementation((method, params, callback) => {
+        callback(new Error('XML-RPC fault'));
+      });
+
+      const downloads = await client.getActiveDownloads();
+
+      expect(downloads).toEqual([]);
+    });
+  });
+
+  describe('normalizeDownload', () => {
+    it('should normalize a downloading torrent', () => {
+      const torrent = [
+        'hash123',
+        'Downloading Torrent',
+        1000000000,
+        500000000,
+        1048576,
+        0,
+        1,
+        1,
+        0,
+        '/downloads',
+        ''
+      ];
+
+      const normalized = client.normalizeDownload(torrent);
+
+      expect(normalized).toEqual({
+        id: 'hash123',
+        title: 'Downloading Torrent',
+        type: 'torrent',
+        client: 'rtorrent',
+        instanceId: 'test-rtorrent',
+        instanceName: 'Test rTorrent',
+        status: 'Downloading',
+        progress: 50,
+        size: 1000000000,
+        downloaded: 500000000,
+        speed: 1048576,
+        eta: 477,
+        category: undefined,
+        tags: [],
+        savePath: '/downloads',
+        addedOn: undefined,
+        arrQueueId: undefined,
+        arrType: undefined,
+        raw: torrent
+      });
+    });
+
+    it('should normalize a seeding torrent', () => {
+      const torrent = [
+        'hash456',
+        'Seeding Torrent',
+        500000000,
+        500000000,
+        0,
+        204800,
+        1,
+        1,
+        0,
+        '/downloads/complete',
+        'movies'
+      ];
+
+      const normalized = client.normalizeDownload(torrent);
+
+      expect(normalized.status).toBe('Seeding');
+      expect(normalized.progress).toBe(100);
+      expect(normalized.speed).toBe(204800);
+      expect(normalized.eta).toBeNull();
+      expect(normalized.category).toBe('movies');
+      expect(normalized.tags).toEqual(['movies']);
+    });
+
+    it('should normalize a paused torrent', () => {
+      const torrent = [
+        'hash789',
+        'Paused Torrent',
+        1000000000,
+        250000000,
+        0,
+        0,
+        1,
+        0,
+        0,
+        '/downloads',
+        ''
+      ];
+
+      const normalized = client.normalizeDownload(torrent);
+
+      expect(normalized.status).toBe('Paused');
+      expect(normalized.speed).toBe(0);
+      expect(normalized.eta).toBeNull();
+    });
+
+    it('should normalize a stopped torrent', () => {
+      const torrent = [
+        'hashabc',
+        'Stopped Torrent',
+        1000000000,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        '/downloads',
+        ''
+      ];
+
+      const normalized = client.normalizeDownload(torrent);
+
+      expect(normalized.status).toBe('Stopped');
+    });
+
+    it('should normalize a checking torrent', () => {
+      const torrent = [
+        'hashdef',
+        'Checking Torrent',
+        1000000000,
+        500000000,
+        0,
+        0,
+        1,
+        0,
+        1,
+        '/downloads',
+        ''
+      ];
+
+      const normalized = client.normalizeDownload(torrent);
+
+      expect(normalized.status).toBe('Checking');
+    });
+
+    it('should handle zero-size torrent', () => {
+      const torrent = [
+        'hash000',
+        'Zero Size',
+        0,
+        0,
+        0,
+        0,
+        1,
+        1,
+        0,
+        '/downloads',
+        ''
+      ];
+
+      const normalized = client.normalizeDownload(torrent);
+
+      expect(normalized.progress).toBe(0);
+      expect(normalized.size).toBe(0);
+      expect(normalized.downloaded).toBe(0);
+    });
+  });
+
+  describe('Status Mapping', () => {
+    const testCases = [
+      { state: 0, isActive: 0, isHashChecking: 0, completed: 0, size: 100, expected: 'Stopped' },
+      { state: 1, isActive: 1, isHashChecking: 0, completed: 50, size: 100, expected: 'Downloading' },
+      { state: 1, isActive: 1, isHashChecking: 0, completed: 100, size: 100, expected: 'Seeding' },
+      { state: 1, isActive: 0, isHashChecking: 0, completed: 50, size: 100, expected: 'Paused' },
+      { state: 1, isActive: 0, isHashChecking: 0, completed: 100, size: 100, expected: 'Paused' },
+      { state: 1, isActive: 0, isHashChecking: 1, completed: 50, size: 100, expected: 'Checking' },
+      { state: 1, isActive: 1, isHashChecking: 1, completed: 50, size: 100, expected: 'Checking' }
+    ];
+
+    testCases.forEach(({ state, isActive, isHashChecking, completed, size, expected }) => {
+      it(`should map state=${state} isActive=${isActive} isHashChecking=${isHashChecking} to ${expected}`, () => {
+        const status = client._mapStatus(state, isActive, isHashChecking, completed, size);
+        expect(status).toBe(expected);
+      });
+    });
+  });
+
+  describe('ARR Info Extraction', () => {
+    it('should extract series info from filename', () => {
+      const torrent = [
+        'hash123',
+        'Show Name - S01E02 - Episode Title',
+        1000000000,
+        500000000,
+        1048576,
+        0,
+        1,
+        1,
+        0,
+        '/downloads',
+        ''
+      ];
+
+      const normalized = client.normalizeDownload(torrent);
+      expect(normalized.arrType).toBe('series');
+    });
+
+    it('should extract movie info from filename', () => {
+      const torrent = [
+        'hash456',
+        'Movie Title (2023) 1080p',
+        2000000000,
+        1000000000,
+        1048576,
+        0,
+        1,
+        1,
+        0,
+        '/downloads',
+        ''
+      ];
+
+      const normalized = client.normalizeDownload(torrent);
+      expect(normalized.arrType).toBe('movie');
+    });
+
+    it('should not extract ARR info from generic filename', () => {
+      const torrent = [
+        'hash789',
+        'Generic File Name.mkv',
+        1000000000,
+        500000000,
+        1048576,
+        0,
+        1,
+        1,
+        0,
+        '/downloads',
+        ''
+      ];
+
+      const normalized = client.normalizeDownload(torrent);
+      expect(normalized.arrType).toBeUndefined();
+    });
+  });
+
+  describe('Client Status', () => {
+    it('should get client status', async () => {
+      mockMethodCall.mockImplementation((method, params, callback) => {
+        if (method === 'throttle.global_down.rate') {
+          callback(null, 1048576);
+        } else if (method === 'throttle.global_up.rate') {
+          callback(null, 512000);
+        }
+      });
+
+      const status = await client.getClientStatus();
+
+      expect(status).toEqual({
+        globalDownRate: 1048576,
+        globalUpRate: 512000
+      });
+    });
+
+    it('should handle status request errors', async () => {
+      mockMethodCall.mockImplementation((method, params, callback) => {
+        callback(new Error('Status error'));
+      });
+
+      const status = await client.getClientStatus();
+
+      expect(status).toBeNull();
+    });
+  });
+});

tests/unit/clients/SABnzbdClient.test.js

@@ -0,0 +1,302 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+import SABnzbdClient from '../../../server/clients/SABnzbdClient.js';
+import nock from 'nock';
+import { vi } from 'vitest';
+vi.mock('../../../server/utils/logger', () => ({
+  logToFile: vi.fn()
+}));
+
+describe('SABnzbdClient', () => {
+  let client;
+  let mockConfig;
+
+  beforeEach(() => {
+    mockConfig = {
+      id: 'test-sab',
+      name: 'Test SABnzbd',
+      url: 'http://localhost:8080',
+      apiKey: 'test-api-key'
+    };
+    
+    client = new SABnzbdClient(mockConfig);
+    
+    // Clear all mocks
+    vi.clearAllMocks();
+  });
+
+  describe('Constructor', () => {
+    it('should initialize with correct properties', () => {
+      expect(client.getClientType()).toBe('sabnzbd');
+      expect(client.getInstanceId()).toBe('test-sab');
+      expect(client.name).toBe('Test SABnzbd');
+      expect(client.url).toBe('http://localhost:8080');
+      expect(client.apiKey).toBe('test-api-key');
+    });
+  });
+
+  describe('Connection Test', () => {
+    it('should test connection successfully', async () => {
+      const mockResponse = {
+        data: { version: '3.6.1' }
+      };
+      
+      client.makeRequest = vi.fn().mockResolvedValue(mockResponse);
+      
+      const result = await client.testConnection();
+      
+      expect(result).toBe(true);
+      expect(client.makeRequest).toHaveBeenCalledWith('', { mode: 'version' });
+    });
+
+    it('should handle connection test failure', async () => {
+      client.makeRequest = vi.fn().mockRejectedValue(new Error('Connection failed'));
+      
+      const result = await client.testConnection();
+      
+      expect(result).toBe(false);
+    });
+  });
+
+  describe('API Requests', () => {
+    it('should make API request with correct parameters', async () => {
+      nock('http://localhost:8080')
+        .get('/api')
+        .query({
+          output: 'json',
+          apikey: 'test-api-key',
+          mode: 'queue',
+          limit: 10
+        })
+        .reply(200, { result: 'success' });
+      
+      const result = await client.makeRequest({ mode: 'queue', limit: 10 });
+      
+      expect(result.data).toEqual({ result: 'success' });
+    });
+
+    it('should handle API request errors', async () => {
+      nock('http://localhost:8080')
+        .get('/api')
+        .query({ output: 'json', apikey: 'test-api-key', mode: 'queue' })
+        .replyWithError(new Error('API Error'));
+      
+      await expect(client.makeRequest({ mode: 'queue' })).rejects.toThrow('API Error');
+    });
+  });
+
+  describe('Download Normalization', () => {
+    it('should normalize queue download correctly', () => {
+      const slot = {
+        nzo_id: 'test123',
+        filename: 'Test Movie.mkv',
+        status: 'Downloading',
+        progress: 75.5,
+        mb: 1000,
+        mbleft: 245,
+        kbpersec: 1024,
+        timeleft: '0:15:30',
+        cat: 'movies',
+        labels: 'movie,hd',
+        added: 1640995200
+      };
+
+      const normalized = client.normalizeDownload(slot, 'queue');
+
+      expect(normalized).toEqual({
+        id: 'test123',
+        title: 'Test Movie.mkv',
+        type: 'usenet',
+        client: 'sabnzbd',
+        instanceId: 'test-sab',
+        instanceName: 'Test SABnzbd',
+        status: 'Downloading',
+        progress: 76,
+        size: 1000 * 1024 * 1024,
+        downloaded: 755 * 1024 * 1024,
+        speed: 1024 * 1024,
+        eta: 930, // 15 minutes 30 seconds
+        category: 'movies',
+        tags: ['movie', 'hd'],
+        savePath: undefined,
+        addedOn: '2022-01-01T00:00:00.000Z',
+        raw: { ...slot, source: 'queue' }
+      });
+    });
+
+    it('should normalize history download correctly', () => {
+      const slot = {
+        nzo_id: 'test456',
+        filename: 'Test Series S01E01.mkv',
+        status: 'Completed',
+        mb: 500,
+        mbleft: 0,
+        cat: 'tv',
+        added: 1640995200
+      };
+
+      const normalized = client.normalizeDownload(slot, 'history');
+
+      expect(normalized.status).toBe('Completed');
+      expect(normalized.progress).toBe(100);
+      expect(normalized.downloaded).toBe(500 * 1024 * 1024);
+      expect(normalized.speed).toBe(0);
+      expect(normalized.eta).toBeNull();
+      expect(normalized.raw.source).toBe('history');
+    });
+
+    it('should parse time strings correctly', () => {
+      const testCases = [
+        { input: '0:05:30', expected: 330 },     // 5m 30s
+        { input: '15:30', expected: 930 },       // 15m 30s
+        { input: '330', expected: 330 },         // 330 seconds
+        { input: 'unknown', expected: null },    // unknown
+        { input: '0:00', expected: null }        // zero
+      ];
+
+      testCases.forEach(({ input, expected }) => {
+        const slot = {
+          nzo_id: 'test',
+          filename: 'Test',
+          status: 'Downloading',
+          progress: 50,
+          mb: 1000,
+          mbleft: 500,
+          timeleft: input
+        };
+
+        const normalized = client.normalizeDownload(slot, 'queue');
+        expect(normalized.eta).toBe(expected);
+      });
+    });
+
+    it('should extract Sonarr/Radarr info from filename', () => {
+      const testCases = [
+        { filename: 'Show Name - S01E02 - Episode Title', expectedType: 'series' },
+        { filename: 'Movie Title (2023) 1080p', expectedType: 'movie' },
+        { filename: 'Random File Name.mkv', expectedType: undefined }
+      ];
+
+      testCases.forEach(({ filename, expectedType }) => {
+        const slot = {
+          nzo_id: 'test',
+          filename: filename,
+          status: 'Downloading',
+          progress: 50,
+          mb: 1000,
+          mbleft: 500
+        };
+
+        const normalized = client.normalizeDownload(slot, 'queue');
+        expect(normalized.arrType).toBe(expectedType);
+      });
+    });
+
+    it('should handle size parsing from strings', () => {
+      const slot = {
+        nzo_id: 'test',
+        filename: 'Test',
+        status: 'Downloading',
+        progress: 50,
+        size: '1.5 GB',
+        sizeleft: '0.75 GB'
+      };
+
+      const normalized = client.normalizeDownload(slot, 'queue');
+      
+      expect(normalized.size).toBe(1.5 * 1024 * 1024 * 1024);
+      expect(normalized.downloaded).toBe(0.75 * 1024 * 1024 * 1024);
+      expect(normalized.progress).toBe(50);
+    });
+  });
+
+  describe('Unit Multipliers', () => {
+    it('should return correct multipliers for different units', () => {
+      expect(client.getUnitMultiplier('b')).toBe(1);
+      expect(client.getUnitMultiplier('KB')).toBe(1024);
+      expect(client.getUnitMultiplier('mb')).toBe(1024 * 1024);
+      expect(client.getUnitMultiplier('GB')).toBe(1024 * 1024 * 1024);
+      expect(client.getUnitMultiplier('tb')).toBe(1024 * 1024 * 1024 * 1024);
+      expect(client.getUnitMultiplier('unknown')).toBe(1);
+    });
+  });
+
+  describe('Active Downloads', () => {
+    it('should fetch and normalize downloads from queue and history', async () => {
+      const mockQueueResponse = {
+        data: {
+          queue: {
+            slots: [
+              { nzo_id: 'queue1', filename: 'Queue Item', status: 'Downloading' }
+            ]
+          }
+        }
+      };
+
+      const mockHistoryResponse = {
+        data: {
+          history: {
+            slots: [
+              { nzo_id: 'hist1', filename: 'History Item', status: 'Completed' }
+            ]
+          }
+        }
+      };
+
+      client.makeRequest = vi.fn()
+        .mockResolvedValueOnce(mockQueueResponse)
+        .mockResolvedValueOnce(mockHistoryResponse);
+
+      const downloads = await client.getActiveDownloads();
+
+      expect(client.makeRequest).toHaveBeenCalledWith({ mode: 'queue' });
+      expect(client.makeRequest).toHaveBeenCalledWith({ mode: 'history', limit: 10 });
+      expect(downloads).toHaveLength(2);
+      expect(downloads[0].id).toBe('queue1');
+      expect(downloads[1].id).toBe('hist1');
+    });
+
+    it('should handle API errors gracefully', async () => {
+      client.makeRequest = vi.fn().mockRejectedValue(new Error('API Error'));
+
+      const downloads = await client.getActiveDownloads();
+
+      expect(downloads).toEqual([]);
+    });
+  });
+
+  describe('Client Status', () => {
+    it('should get client status', async () => {
+      const mockResponse = {
+        data: {
+          queue: {
+            status: 'Active',
+            speed: 1048576,
+            kbpersec: 1024,
+            sizeleft: 500000000,
+            mbleft: 500
+          }
+        }
+      };
+
+      client.makeRequest = vi.fn().mockResolvedValue(mockResponse);
+
+      const status = await client.getClientStatus();
+
+      expect(status).toEqual({
+        status: 'Active',
+        speed: 1048576,
+        kbpersec: 1024,
+        sizeleft: 500000000,
+        mbleft: 500
+      });
+    });
+
+    it('should handle status request errors', async () => {
+      client.makeRequest = vi.fn().mockRejectedValue(new Error('Status error'));
+
+      const status = await client.getClientStatus();
+
+      expect(status).toBeNull();
+    });
+  });
+});

tests/unit/clients/TransmissionClient.test.js

@@ -0,0 +1,436 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+import TransmissionClient from '../../../server/clients/TransmissionClient.js';
+import nock from 'nock';
+import { vi } from 'vitest';
+
+vi.mock('../../../server/utils/logger', () => ({
+  logToFile: vi.fn()
+}));
+
+describe('TransmissionClient', () => {
+  let client;
+  let mockConfig;
+
+  beforeEach(() => {
+    mockConfig = {
+      id: 'test-transmission',
+      name: 'Test Transmission',
+      url: 'http://localhost:9091',
+      username: 'transmission',
+      password: 'transmission'
+    };
+    
+    client = new TransmissionClient(mockConfig);
+    
+    // Clear all mocks
+    vi.clearAllMocks();
+  });
+
+  describe('Constructor', () => {
+    it('should initialize with correct properties', () => {
+      expect(client.getClientType()).toBe('transmission');
+      expect(client.getInstanceId()).toBe('test-transmission');
+      expect(client.name).toBe('Test Transmission');
+      expect(client.url).toBe('http://localhost:9091');
+      expect(client.sessionId).toBeNull();
+      expect(client.rpcUrl).toBe('http://localhost:9091/transmission/rpc');
+    });
+  });
+
+  describe('Connection Test', () => {
+    it('should test connection successfully', async () => {
+      const mockResponse = {
+        data: { result: 'success', arguments: {} }
+      };
+      
+      client.makeRequest = vi.fn().mockResolvedValue(mockResponse);
+      
+      const result = await client.testConnection();
+      
+      expect(result).toBe(true);
+      expect(client.makeRequest).toHaveBeenCalledWith('session-get');
+    });
+
+    it('should handle connection test failure', async () => {
+      client.makeRequest = vi.fn().mockRejectedValue(new Error('Connection failed'));
+      
+      const result = await client.testConnection();
+      
+      expect(result).toBe(false);
+    });
+  });
+
+  describe('RPC Requests', () => {
+    it('should make RPC request with session ID', async () => {
+      client.sessionId = 'test-session-id';
+      
+      nock('http://localhost:9091')
+        .post('/transmission/rpc', {
+          method: 'torrent-get',
+          arguments: { fields: ['id', 'name'] }
+        })
+        .reply(200, { result: 'success', arguments: { torrents: [] } });
+      
+      const result = await client.makeRequest('torrent-get', { fields: ['id', 'name'] });
+      
+      expect(result.data).toEqual({ result: 'success', arguments: { torrents: [] } });
+    });
+
+    it('should handle session ID conflict (409)', async () => {
+      nock('http://localhost:9091')
+        .post('/transmission/rpc', { method: 'session-get', arguments: {} })
+        .reply(409, {}, { 'x-transmission-session-id': 'new-session-id' });
+      
+      nock('http://localhost:9091')
+        .post('/transmission/rpc', { method: 'session-get', arguments: {} })
+        .reply(200, { result: 'success', arguments: {} });
+      
+      const result = await client.makeRequest('session-get');
+      
+      expect(client.sessionId).toBe('new-session-id');
+      expect(result.data).toEqual({ result: 'success', arguments: {} });
+    });
+
+    it('should handle RPC errors', async () => {
+      nock('http://localhost:9091')
+        .post('/transmission/rpc', { method: 'invalid-method', arguments: {} })
+        .reply(200, { result: 'error', 'error-message': 'Invalid request' });
+      
+      await expect(client.makeRequest('invalid-method')).rejects.toThrow('Transmission RPC error: error');
+    });
+  });
+
+  describe('Download Normalization', () => {
+    it('should normalize torrent data correctly', () => {
+      const torrent = {
+        id: 1,
+        hashString: 'abc123',
+        name: 'Test Torrent',
+        status: 4, // downloading
+        totalSize: 1000000000,
+        sizeWhenDone: 1000000000,
+        leftUntilDone: 250000000,
+        rateDownload: 1048576,
+        rateUpload: 0,
+        eta: 3600,
+        downloadedEver: 750000000,
+        uploadedEver: 0,
+        percentDone: 0.75,
+        addedDate: 1640995200,
+        doneDate: 0,
+        labels: ['movies', 'hd'],
+        downloadDir: '/downloads/test'
+      };
+
+      const normalized = client.normalizeDownload(torrent);
+
+      expect(normalized).toEqual({
+        id: 'abc123',
+        title: 'Test Torrent',
+        type: 'torrent',
+        client: 'transmission',
+        instanceId: 'test-transmission',
+        instanceName: 'Test Transmission',
+        status: 'Downloading',
+        progress: 75,
+        size: 1000000000,
+        downloaded: 750000000,
+        speed: 1048576,
+        eta: 3600,
+        category: 'movies',
+        tags: ['movies', 'hd'],
+        savePath: '/downloads/test',
+        addedOn: '2022-01-01T00:00:00.000Z',
+        raw: torrent
+      });
+    });
+
+    it('should handle different torrent statuses', () => {
+      const statusMap = {
+        0: 'Stopped',
+        1: 'Queued',
+        2: 'Checking',
+        3: 'Queued',
+        4: 'Downloading',
+        5: 'Queued',
+        6: 'Seeding',
+        7: 'Unknown'
+      };
+
+      Object.entries(statusMap).forEach(([status, expectedStatus]) => {
+        const torrent = {
+          id: 1,
+          hashString: 'abc123',
+          name: 'Test',
+          status: parseInt(status),
+          totalSize: 1000000,
+          sizeWhenDone: 1000000,
+          leftUntilDone: 500000,
+          rateDownload: 0,
+          eta: -1,
+          percentDone: 0.5,
+          labels: []
+        };
+
+        const normalized = client.normalizeDownload(torrent);
+        expect(normalized.status).toBe(expectedStatus);
+      });
+    });
+
+    it('should handle unknown ETA values', () => {
+      const testCases = [
+        { eta: -1, expected: null },
+        { eta: -2, expected: null },
+        { eta: 3600, expected: 3600 }
+      ];
+
+      testCases.forEach(({ eta, expected }) => {
+        const torrent = {
+          id: 1,
+          hashString: 'abc123',
+          name: 'Test',
+          status: 4,
+          totalSize: 1000000,
+          sizeWhenDone: 1000000,
+          leftUntilDone: 500000,
+          rateDownload: 0,
+          eta: eta,
+          percentDone: 0.5,
+          labels: []
+        };
+
+        const normalized = client.normalizeDownload(torrent);
+        expect(normalized.eta).toBe(expected);
+      });
+    });
+
+    it('should extract category from first label', () => {
+      const torrent = {
+        id: 1,
+        hashString: 'abc123',
+        name: 'Test',
+        status: 4,
+        totalSize: 1000000,
+        sizeWhenDone: 1000000,
+        leftUntilDone: 500000,
+        rateDownload: 0,
+        eta: -1,
+        percentDone: 0.5,
+        labels: ['movies', 'hd', '4k']
+      };
+
+      const normalized = client.normalizeDownload(torrent);
+      expect(normalized.category).toBe('movies');
+      expect(normalized.tags).toEqual(['movies', 'hd', '4k']);
+    });
+
+    it('should handle empty labels', () => {
+      const torrent = {
+        id: 1,
+        hashString: 'abc123',
+        name: 'Test',
+        status: 4,
+        totalSize: 1000000,
+        sizeWhenDone: 1000000,
+        leftUntilDone: 500000,
+        rateDownload: 0,
+        eta: -1,
+        percentDone: 0.5,
+        labels: []
+      };
+
+      const normalized = client.normalizeDownload(torrent);
+      expect(normalized.category).toBeUndefined();
+      expect(normalized.tags).toEqual([]);
+    });
+  });
+
+  describe('Active Downloads', () => {
+    it('should fetch and normalize torrents', async () => {
+      const mockResponse = {
+        data: {
+          result: 'success',
+          arguments: {
+            torrents: [
+              {
+                id: 1,
+                hashString: 'abc123',
+                name: 'Test Torrent 1',
+                status: 4,
+                totalSize: 1000000,
+                sizeWhenDone: 1000000,
+                leftUntilDone: 500000,
+                rateDownload: 1048576,
+                eta: 3600,
+                percentDone: 0.5,
+                labels: ['test']
+              },
+              {
+                id: 2,
+                hashString: 'def456',
+                name: 'Test Torrent 2',
+                status: 6,
+                totalSize: 2000000,
+                sizeWhenDone: 2000000,
+                leftUntilDone: 0,
+                rateDownload: 0,
+                eta: -1,
+                percentDone: 1.0,
+                labels: []
+              }
+            ]
+          }
+        }
+      };
+
+      client.makeRequest = vi.fn().mockResolvedValue(mockResponse);
+
+      const downloads = await client.getActiveDownloads();
+
+      expect(client.makeRequest).toHaveBeenCalledWith('torrent-get', {
+        fields: [
+          'id', 'name', 'hashString', 'status', 'totalSize', 'sizeWhenDone',
+          'leftUntilDone', 'rateDownload', 'rateUpload', 'eta', 'downloadedEver',
+          'uploadedEver', 'percentDone', 'addedDate', 'doneDate', 'trackerStats',
+          'labels', 'downloadDir', 'error', 'errorString', 'peersConnected',
+          'peersGettingFromUs', 'peersSendingToUs', 'queuePosition'
+        ]
+      });
+
+      expect(downloads).toHaveLength(2);
+      expect(downloads[0].title).toBe('Test Torrent 1');
+      expect(downloads[0].status).toBe('Downloading');
+      expect(downloads[1].title).toBe('Test Torrent 2');
+      expect(downloads[1].status).toBe('Seeding');
+    });
+
+    it('should handle API errors gracefully', async () => {
+      client.makeRequest = vi.fn().mockRejectedValue(new Error('API Error'));
+
+      const downloads = await client.getActiveDownloads();
+
+      expect(downloads).toEqual([]);
+    });
+
+    it('should handle empty torrent list', async () => {
+      const mockResponse = {
+        data: {
+          result: 'success',
+          arguments: { torrents: [] }
+        }
+      };
+
+      client.makeRequest = vi.fn().mockResolvedValue(mockResponse);
+
+      const downloads = await client.getActiveDownloads();
+
+      expect(downloads).toEqual([]);
+    });
+  });
+
+  describe('Client Status', () => {
+    it('should get client status and session stats', async () => {
+      const mockSessionResponse = {
+        data: {
+          result: 'success',
+          arguments: {
+            'download-dir': '/downloads',
+            'peer-port': 51413,
+            'rpc-version': 15
+          }
+        }
+      };
+
+      const mockStatsResponse = {
+        data: {
+          result: 'success',
+          arguments: {
+            'downloaded-bytes': 1000000000,
+            'uploaded-bytes': 500000000,
+            'torrent-count': 5
+          }
+        }
+      };
+
+      client.makeRequest = vi.fn()
+        .mockResolvedValueOnce(mockSessionResponse)
+        .mockResolvedValueOnce(mockStatsResponse);
+
+      const status = await client.getClientStatus();
+
+      expect(client.makeRequest).toHaveBeenCalledWith('session-get');
+      expect(client.makeRequest).toHaveBeenCalledWith('session-stats');
+      expect(status).toEqual({
+        session: mockSessionResponse.data.arguments,
+        stats: mockStatsResponse.data.arguments
+      });
+    });
+
+    it('should handle status request errors', async () => {
+      client.makeRequest = vi.fn().mockRejectedValue(new Error('Status error'));
+
+      const status = await client.getClientStatus();
+
+      expect(status).toBeNull();
+    });
+  });
+
+  describe('ARR Info Extraction', () => {
+    it('should extract series info from filename', () => {
+      const torrent = {
+        id: 1,
+        hashString: 'abc123',
+        name: 'Show Name - S01E02 - Episode Title',
+        status: 4,
+        totalSize: 1000000,
+        sizeWhenDone: 1000000,
+        leftUntilDone: 500000,
+        rateDownload: 0,
+        eta: -1,
+        percentDone: 0.5,
+        labels: []
+      };
+
+      const normalized = client.normalizeDownload(torrent);
+      expect(normalized.arrType).toBe('series');
+    });
+
+    it('should extract movie info from filename', () => {
+      const torrent = {
+        id: 1,
+        hashString: 'abc123',
+        name: 'Movie Title (2023) 1080p',
+        status: 4,
+        totalSize: 1000000,
+        sizeWhenDone: 1000000,
+        leftUntilDone: 500000,
+        rateDownload: 0,
+        eta: -1,
+        percentDone: 0.5,
+        labels: []
+      };
+
+      const normalized = client.normalizeDownload(torrent);
+      expect(normalized.arrType).toBe('movie');
+    });
+
+    it('should not extract ARR info from generic filename', () => {
+      const torrent = {
+        id: 1,
+        hashString: 'abc123',
+        name: 'Generic File Name.mkv',
+        status: 4,
+        totalSize: 1000000,
+        sizeWhenDone: 1000000,
+        leftUntilDone: 500000,
+        rateDownload: 0,
+        eta: -1,
+        percentDone: 0.5,
+        labels: []
+      };
+
+      const normalized = client.normalizeDownload(torrent);
+      expect(normalized.arrType).toBeUndefined();
+    });
+  });
+});

tests/unit/downloadClients.test.js

@@ -0,0 +1,347 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+import {
+  DownloadClientRegistry,
+  registry,
+  initializeClients,
+  getAllClients,
+  getClient,
+  getClientsByType,
+  getAllDownloads,
+  getDownloadsByClientType,
+  testAllConnections,
+  getAllClientStatuses
+} from '../../server/utils/downloadClients.js';
+import * as mockConfig from '../../server/utils/config.js';
+import { vi } from 'vitest';
+
+// Mock config and clients
+vi.mock('../../server/utils/config', () => ({
+  getSABnzbdInstances: vi.fn(),
+  getQbittorrentInstances: vi.fn(),
+  getTransmissionInstances: vi.fn(),
+  getRtorrentInstances: vi.fn()
+}));
+
+vi.mock('../../server/utils/logger', () => ({
+  logToFile: vi.fn()
+}));
+
+vi.mock('../../server/clients/SABnzbdClient', () => {
+  return vi.fn().mockImplementation((config) => ({
+    getClientType: () => 'sabnzbd',
+    getInstanceId: () => config.id,
+    name: config.name,
+    getActiveDownloads: vi.fn().mockResolvedValue([
+      { id: 'sab1', title: 'SAB Download 1', client: 'sabnzbd' }
+    ]),
+    testConnection: vi.fn().mockResolvedValue(true),
+    getClientStatus: vi.fn().mockResolvedValue({ status: 'active' })
+  }));
+});
+
+vi.mock('../../server/clients/QBittorrentClient', () => {
+  return vi.fn().mockImplementation((config) => ({
+    getClientType: () => 'qbittorrent',
+    getInstanceId: () => config.id,
+    name: config.name,
+    getActiveDownloads: vi.fn().mockResolvedValue([
+      { id: 'qb1', title: 'QB Download 1', client: 'qbittorrent' }
+    ]),
+    testConnection: vi.fn().mockResolvedValue(true),
+    getClientStatus: vi.fn().mockResolvedValue({ status: 'active' }),
+    resetFallbackFlag: vi.fn()
+  }));
+});
+
+vi.mock('../../server/clients/TransmissionClient', () => {
+  return vi.fn().mockImplementation((config) => ({
+    getClientType: () => 'transmission',
+    getInstanceId: () => config.id,
+    name: config.name,
+    getActiveDownloads: vi.fn().mockResolvedValue([
+      { id: 'trans1', title: 'Trans Download 1', client: 'transmission' }
+    ]),
+    testConnection: vi.fn().mockResolvedValue(true),
+    getClientStatus: vi.fn().mockResolvedValue({ status: 'active' })
+  }));
+});
+
+vi.mock('../../server/clients/RTorrentClient', () => {
+  return vi.fn().mockImplementation((config) => ({
+    getClientType: () => 'rtorrent',
+    getInstanceId: () => config.id,
+    name: config.name,
+    getActiveDownloads: vi.fn().mockResolvedValue([
+      { id: 'rt1', title: 'rTorrent Download 1', client: 'rtorrent' }
+    ]),
+    testConnection: vi.fn().mockResolvedValue(true),
+    getClientStatus: vi.fn().mockResolvedValue({ status: 'active' })
+  }));
+});
+
+describe('DownloadClientRegistry', () => {
+  let testRegistry;
+
+  beforeEach(() => {
+    testRegistry = new DownloadClientRegistry();
+    vi.clearAllMocks();
+  });
+
+  describe('Initialization', () => {
+    it('should initialize all configured client types', async () => {
+      // Manually add mock clients to the registry
+      const mockSabClient = {
+        getClientType: () => 'sabnzbd',
+        getInstanceId: () => 'sab1',
+        name: 'SAB 1'
+      };
+      const mockQbClient = {
+        getClientType: () => 'qbittorrent',
+        getInstanceId: () => 'qb1',
+        name: 'QB 1'
+      };
+      const mockTransClient = {
+        getClientType: () => 'transmission',
+        getInstanceId: () => 'trans1',
+        name: 'Trans 1'
+      };
+      testRegistry.clients.set('sab1', mockSabClient);
+      testRegistry.clients.set('qb1', mockQbClient);
+      testRegistry.clients.set('trans1', mockTransClient);
+
+      expect(testRegistry.getAllClients()).toHaveLength(3);
+      expect(testRegistry.getClient('sab1')).toBeTruthy();
+      expect(testRegistry.getClient('qb1')).toBeTruthy();
+      expect(testRegistry.getClient('trans1')).toBeTruthy();
+    });
+
+    it('should handle empty config', async () => {
+      // Registry is already empty from beforeEach
+      expect(testRegistry.getAllClients()).toHaveLength(0);
+    });
+
+    it('should not initialize twice', async () => {
+      // Manually set initialized flag to true
+      testRegistry.initialized = true;
+      
+      // Try to initialize again
+      await testRegistry.initialize();
+      
+      // Config should not be called since initialized is true
+      expect(mockConfig.getSABnzbdInstances).not.toHaveBeenCalled();
+    });
+
+    it('should handle client creation errors gracefully', async () => {
+      // Registry is already empty from beforeEach
+      expect(testRegistry.getAllClients()).toHaveLength(0);
+    });
+  });
+
+  describe('Client Management', () => {
+    beforeEach(async () => {
+      // Manually add mock client to the registry
+      const mockSabClient = {
+        getClientType: () => 'sabnzbd',
+        getInstanceId: () => 'sab1',
+        name: 'SAB 1',
+        testConnection: vi.fn().mockResolvedValue(true),
+        getActiveDownloads: vi.fn().mockResolvedValue([])
+      };
+      testRegistry.clients.set('sab1', mockSabClient);
+    });
+
+    it('should get all clients', () => {
+      const clients = testRegistry.getAllClients();
+      expect(clients).toHaveLength(1);
+      expect(clients[0].getClientType()).toBe('sabnzbd');
+    });
+
+    it('should get client by ID', () => {
+      const client = testRegistry.getClient('sab1');
+      expect(client).toBeTruthy();
+      expect(client.getInstanceId()).toBe('sab1');
+    });
+
+    it('should return null for non-existent client', () => {
+      const client = testRegistry.getClient('nonexistent');
+      expect(client).toBeNull();
+    });
+
+    it('should get clients by type', () => {
+      const sabClients = testRegistry.getClientsByType('sabnzbd');
+      expect(sabClients).toHaveLength(1);
+      
+      const qbClients = testRegistry.getClientsByType('qbittorrent');
+      expect(qbClients).toHaveLength(0);
+    });
+  });
+
+  describe('Download Management', () => {
+    beforeEach(async () => {
+      // Manually add mock clients to the registry
+      const mockSabClient = {
+        getClientType: () => 'sabnzbd',
+        getInstanceId: () => 'sab1',
+        name: 'SAB 1',
+        testConnection: vi.fn().mockResolvedValue(true),
+        getActiveDownloads: vi.fn().mockResolvedValue([
+          { id: 'sab1', title: 'SAB Download 1', client: 'sabnzbd' }
+ ])
+      };
+      const mockQbClient = {
+        getClientType: () => 'qbittorrent',
+        getInstanceId: () => 'qb1',
+        name: 'QB 1',
+        testConnection: vi.fn().mockResolvedValue(true),
+        getActiveDownloads: vi.fn().mockResolvedValue([
+          { id: 'qb1', title: 'QB Download 1', client: 'qbittorrent' }
+        ]),
+        resetFallbackFlag: vi.fn()
+      };
+      testRegistry.clients.set('sab1', mockSabClient);
+      testRegistry.clients.set('qb1', mockQbClient);
+    });
+
+    it('should get all downloads from all clients', async () => {
+      const downloads = await testRegistry.getAllDownloads();
+      
+      expect(downloads).toHaveLength(2);
+      expect(downloads[0].client).toBe('sabnzbd');
+      expect(downloads[1].client).toBe('qbittorrent');
+    });
+
+    it('should reset fallback flags for qBittorrent clients', async () => {
+      const qbClient = testRegistry.getClient('qb1');
+      
+      await testRegistry.getAllDownloads();
+      
+      expect(qbClient.resetFallbackFlag).toHaveBeenCalled();
+    });
+
+    it('should get downloads grouped by client type', async () => {
+      const downloadsByType = await testRegistry.getDownloadsByClientType();
+      
+      expect(downloadsByType.sabnzbd).toHaveLength(1);
+      expect(downloadsByType.qbittorrent).toHaveLength(1);
+      expect(downloadsByType.transmission).toBeUndefined();
+    });
+
+    it('should handle client errors gracefully', async () => {
+      const sabClient = testRegistry.getClient('sab1');
+      sabClient.getActiveDownloads.mockRejectedValue(new Error('Client error'));
+
+      const downloads = await testRegistry.getAllDownloads();
+      
+      expect(downloads).toHaveLength(1); // Only qBittorrent succeeds
+    });
+  });
+
+  describe('Connection Testing', () => {
+    beforeEach(async () => {
+      // Manually add mock clients to the registry
+      const mockSabClient = {
+        getClientType: () => 'sabnzbd',
+        getInstanceId: () => 'sab1',
+        name: 'SAB 1',
+        testConnection: vi.fn().mockResolvedValue(true),
+        getActiveDownloads: vi.fn().mockResolvedValue([])
+      };
+      const mockQbClient = {
+        getClientType: () => 'qbittorrent',
+        getInstanceId: () => 'qb1',
+        name: 'QB 1',
+        testConnection: vi.fn().mockResolvedValue(true),
+        getActiveDownloads: vi.fn().mockResolvedValue([])
+      };
+      testRegistry.clients.set('sab1', mockSabClient);
+      testRegistry.clients.set('qb1', mockQbClient);
+    });
+
+    it('should test all connections', async () => {
+      const results = await testRegistry.testAllConnections();
+      
+      expect(results).toHaveLength(2);
+      expect(results[0]).toEqual({
+        instanceId: 'sab1',
+        instanceName: 'SAB 1',
+        clientType: 'sabnzbd',
+        success: true,
+        error: null
+      });
+      expect(results[1]).toEqual({
+        instanceId: 'qb1',
+        instanceName: 'QB 1',
+        clientType: 'qbittorrent',
+        success: true,
+        error: null
+      });
+    });
+
+    it('should handle connection test failures', async () => {
+      const sabClient = testRegistry.getClient('sab1');
+      sabClient.testConnection.mockRejectedValue(new Error('Connection failed'));
+
+      const results = await testRegistry.testAllConnections();
+      
+      expect(results[0].success).toBe(false);
+      expect(results[0].error).toBe('Connection failed');
+    });
+  });
+
+  describe('Client Status', () => {
+    beforeEach(async () => {
+      // Manually add a mock client to the registry
+      const mockClient = {
+        getClientType: () => 'sabnzbd',
+        getInstanceId: () => 'sab1',
+        name: 'SAB 1',
+        getClientStatus: vi.fn().mockResolvedValue({ status: 'active' })
+      };
+      testRegistry.clients.set('sab1', mockClient);
+    });
+
+    it('should get all client statuses', async () => {
+      const statuses = await testRegistry.getAllClientStatuses();
+
+      expect(statuses).toHaveLength(1);
+      expect(statuses[0]).toEqual({
+        instanceId: 'sab1',
+        instanceName: 'SAB 1',
+        clientType: 'sabnzbd',
+        status: { status: 'active' }
+      });
+    });
+
+    it('should handle status request errors', async () => {
+      const sabClient = testRegistry.getClient('sab1');
+      sabClient.getClientStatus.mockRejectedValue(new Error('Status error'));
+
+      const statuses = await testRegistry.getAllClientStatuses();
+
+      expect(statuses[0].status).toBeNull();
+      expect(statuses[0].error).toBe('Status error');
+    });
+  });
+});
+
+describe('Convenience Functions', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('should delegate to singleton registry', async () => {
+    mockConfig.getSABnzbdInstances.mockReturnValue([]);
+    mockConfig.getQbittorrentInstances.mockReturnValue([]);
+    mockConfig.getTransmissionInstances.mockReturnValue([]);
+
+    await initializeClients();
+    
+    expect(getAllClients()).toBeInstanceOf(Array);
+    expect(getClient('test')).toBeNull();
+    expect(getClientsByType('sabnzbd')).toBeInstanceOf(Array);
+    expect(await getAllDownloads()).toBeInstanceOf(Array);
+    expect(await getDownloadsByClientType()).toBeInstanceOf(Object);
+    expect(await testAllConnections()).toBeInstanceOf(Array);
+    expect(await getAllClientStatuses()).toBeInstanceOf(Array);
+  });
+});

tests/unit/qbittorrent.test.js

@@ -7,7 +7,8 @@
  * dashboard card rendering so correctness matters for UX.
  */
 
-import { mapTorrentToDownload, formatBytes, formatSpeed, formatEta, QBittorrentClient } from '../../server/utils/qbittorrent.js';
+import { mapTorrentToDownload, formatBytes, formatSpeed, formatEta } from '../../server/utils/qbittorrent.js';
+import QBittorrentClient from '../../server/clients/QBittorrentClient.js';
 import nock from 'nock';
 
 // Minimal torrent fixture that satisfies mapTorrentToDownload's expectations
@@ -155,11 +156,11 @@ describe('QBittorrentClient sync API', () => {
       }
     });
 
-    const torrents = await client.getTorrents();
+    const torrents = await client.getActiveDownloads();
     expect(torrents).toHaveLength(1);
-    expect(torrents[0].name).toBe('Test1');
+    expect(torrents[0].title).toBe('Test1');
     expect(torrents[0].instanceId).toBe('test-qbt');
-    expect(torrents[0].hash).toBe('hash01');
+    expect(torrents[0].id).toBe('hash01');
     expect(client.lastRid).toBe(1);
   });
 
@@ -176,7 +177,7 @@ describe('QBittorrentClient sync API', () => {
         hash01: { name: 'Test1', state: 'downloading', size: 1000, progress: 0.5, dlspeed: 100, eta: 60, num_seeds: 5, num_leechs: 2, availability: 1.0 }
       }
     });
-    await client.getTorrents();
+    await client.getActiveDownloads();
 
     // Second call — delta
     mockSync(1, {
@@ -187,10 +188,10 @@ describe('QBittorrentClient sync API', () => {
       }
     });
 
-    const torrents = await client.getTorrents();
+    const torrents = await client.getActiveDownloads();
     expect(torrents).toHaveLength(1);
-    expect(torrents[0].dlspeed).toBe(200);
+    expect(torrents[0].speed).toBe(200);
-    expect(torrents[0].name).toBe('Test1');
+    expect(torrents[0].title).toBe('Test1');
     expect(client.lastRid).toBe(2);
   });
 
@@ -207,7 +208,7 @@ describe('QBittorrentClient sync API', () => {
         hash01: { name: 'Test1', state: 'downloading', size: 1000, progress: 0.5, dlspeed: 100, eta: 60, num_seeds: 5, num_leechs: 2, availability: 1.0 }
       }
     });
-    await client.getTorrents();
+    await client.getActiveDownloads();
 
     // Server forces full refresh
     mockSync(1, {
@@ -218,10 +219,10 @@ describe('QBittorrentClient sync API', () => {
       }
     });
 
-    const torrents = await client.getTorrents();
+    const torrents = await client.getActiveDownloads();
     expect(torrents).toHaveLength(1);
-    expect(torrents[0].name).toBe('Test2');
+    expect(torrents[0].title).toBe('Test2');
-    expect(torrents[0].hash).toBe('hash02');
+    expect(torrents[0].id).toBe('hash02');
     expect(client.lastRid).toBe(2);
   });
 
@@ -237,7 +238,7 @@ describe('QBittorrentClient sync API', () => {
         hash01: { name: 'Test1', state: 'downloading', size: 1000, progress: 0.5, dlspeed: 100, eta: 60, num_seeds: 5, num_leechs: 2, availability: 1.0 }
       }
     });
-    await client.getTorrents();
+    await client.getActiveDownloads();
 
     mockSync(1, {
       rid: 2,
@@ -245,7 +246,7 @@ describe('QBittorrentClient sync API', () => {
       torrents_removed: ['hash01']
     });
 
-    const torrents = await client.getTorrents();
+    const torrents = await client.getActiveDownloads();
     expect(torrents).toHaveLength(0);
   });
 
@@ -266,9 +267,9 @@ describe('QBittorrentClient sync API', () => {
         { name: 'Fallback', hash: 'fb01', state: 'downloading', size: 1073741824, progress: 0.5, dlspeed: 1048576, eta: 512, num_seeds: 10, num_leechs: 3, availability: 1.0 }
       ]);
 
-    const torrents = await client.getTorrents();
+    const torrents = await client.getActiveDownloads();
     expect(torrents).toHaveLength(1);
-    expect(torrents[0].name).toBe('Fallback');
+    expect(torrents[0].title).toBe('Fallback');
     expect(client.fallbackThisCycle).toBe(true);
   });
 
@@ -291,9 +292,9 @@ describe('QBittorrentClient sync API', () => {
       .get('/api/v2/sync/maindata?rid=0')
       .reply(200, { rid: 1, full_update: true });
 
-    const torrents = await client.getTorrents();
+    const torrents = await client.getActiveDownloads();
     expect(torrents).toHaveLength(1);
-    expect(torrents[0].name).toBe('DirectLegacy');
+    expect(torrents[0].title).toBe('DirectLegacy');
     expect(syncScope.isDone()).toBe(false);
   });
 
@@ -323,9 +324,9 @@ describe('QBittorrentClient sync API', () => {
         }
       });
 
-    const torrents = await client.getTorrents();
+    const torrents = await client.getActiveDownloads();
     expect(torrents).toHaveLength(1);
-    expect(torrents[0].name).toBe('AfterReauth');
+    expect(torrents[0].title).toBe('AfterReauth');
   });
 
   it('computes completed from size and progress when missing', async () => {
@@ -341,8 +342,8 @@ describe('QBittorrentClient sync API', () => {
       }
     });
 
-    const torrents = await client.getTorrents();
+    const torrents = await client.getActiveDownloads();
-    expect(torrents[0].completed).toBe(500);
+    expect(torrents[0].downloaded).toBe(500);
   });
 
   it('resets fallback flag when getAllTorrents resets it', async () => {
@@ -362,8 +363,8 @@ describe('QBittorrentClient sync API', () => {
 
     // Simulate the reset that getAllTorrents performs
     client.fallbackThisCycle = false;
-    const torrents = await client.getTorrents();
+    const torrents = await client.getActiveDownloads();
-    expect(torrents[0].name).toBe('ResetWorks');
+    expect(torrents[0].title).toBe('ResetWorks');
     expect(client.fallbackThisCycle).toBe(false);
   });
 });