feat: Session Persistence API for Zero-Downtime Deployments (v2.24.1) (#438 )

* feat: Add session persistence API for zero-downtime deployments (v2.24.1) Implements export/restore functionality for MCP sessions to support container restarts without losing user sessions. This enables zero-downtime deployments for multi-tenant platforms and Kubernetes/Docker environments. New Features: - exportSessionState() - Export active sessions to JSON - restoreSessionState() - Restore sessions from exported data - SessionState type - Serializable session structure - Comprehensive test suite (22 tests, 100% passing) Implementation Details: - Only exports sessions with valid n8nApiUrl and n8nApiKey - Automatically filters expired sessions (respects sessionTimeout) - Validates context structure using existing validation - Handles null/invalid sessions gracefully with warnings - Enforces MAX_SESSIONS limit during restore (100 sessions) - Dormant sessions recreate transport/server on first request Files Modified: - src/http-server-single-session.ts: Core export/restore logic - src/mcp-engine.ts: Public API wrapper methods - src/types/session-state.ts: Type definitions - tests/: Comprehensive unit tests Security Note: Session data contains plaintext n8n API keys. Downstream applications MUST encrypt session data before persisting to disk. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com> Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en * feat: implement 7 critical session persistence API fixes for production readiness This commit implements all 7 critical fixes identified in the code review to make the session persistence API production-ready for zero-downtime container deployments in multi-tenant environments. Fixes implemented: 1. Made instanceId optional in SessionState interface 2. Removed redundant validation, properly using validateInstanceContext() 3. Fixed race condition in MAX_SESSIONS check using real-time count 4. Added comprehensive security logging with logSecurityEvent() helper 5. Added duplicate session ID detection during export with Set tracking 6. Added date parsing validation with isNaN checks for Invalid Date objects 7. Restructured null checks for proper TypeScript type narrowing Changes: - src/types/session-state.ts: Made instanceId optional - src/http-server-single-session.ts: Implemented all validation and security fixes - tests/unit/http-server/session-persistence.test.ts: Fixed MAX_SESSIONS test All 13 session persistence unit tests passing. All 9 MCP engine session persistence tests passing. Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com> --------- Co-authored-by: Claude <noreply@anthropic.com>
2026-01-30 06:22:04 +00:00 · 2025-11-24 18:53:26 +01:00
10 changed files with 1273 additions and 7 deletions
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,63 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

 ## [Unreleased]

+## [2.24.1] - 2025-01-24
+
+### ✨ Features
+
+**Session Persistence API**
+
+Added export/restore functionality for MCP sessions to enable zero-downtime deployments in container environments (Kubernetes, Docker Swarm, etc.).
+
+#### What's New
+
+**1. Export Session State**
+- `exportSessionState()` method in `SingleSessionHTTPServer` and `N8NMCPEngine`
+- Exports all active sessions with metadata and instance context
+- Automatically filters expired sessions
+- Returns serializable `SessionState[]` array
+
+**2. Restore Session State**
+- `restoreSessionState(sessions)` method for session recovery
+- Validates session structure using existing `validateInstanceContext()`
+- Handles null/invalid sessions gracefully with warnings
+- Enforces MAX_SESSIONS limit (100 concurrent sessions)
+- Skips expired sessions during restore
+
+**3. SessionState Type**
+- New type definition in `src/types/session-state.ts`
+- Fully documented with JSDoc comments
+- Includes metadata (timestamps) and context (credentials)
+- Exported from main package index
+
+**4. Dormant Session Behavior**
+- Restored sessions are "dormant" until first request
+- Transport and server objects recreated on-demand
+- Memory-efficient session recovery
+
+#### Security Considerations
+
+⚠️ **IMPORTANT:** Exported session data contains plaintext n8n API keys. Downstream applications MUST encrypt session data before persisting to disk using AES-256-GCM or equivalent.
+
+#### Use Cases
+- Zero-downtime deployments in container orchestration
+- Session recovery after crashes or restarts
+- Multi-tenant platform session management
+- Rolling updates without user disruption
+
+#### Testing
+- 22 comprehensive unit tests (100% passing)
+- Tests cover export, restore, edge cases, and round-trip cycles
+- Validation of expired session filtering and error handling
+
+#### Implementation Details
+- Only exports sessions with valid `n8nApiUrl` and `n8nApiKey` in context
+- Respects `sessionTimeout` setting (default 30 minutes)
+- Session metadata and context persisted; transport/server recreated on-demand
+- Comprehensive error handling with detailed logging
+
+**Conceived by Romuald Członkowski - [AiAdvisors](https://www.aiadvisors.pl/en)**
+
 ## [2.24.0] - 2025-01-24

 ### ✨ Features
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -32,7 +32,9 @@ src/
 │   ├── expression-validator.ts # n8n expression syntax validation (NEW in v2.5.0)
 │   └── workflow-validator.ts  # Complete workflow validation (NEW in v2.5.0)
 ├── types/
-│   └── type-structures.ts      # Type structure definitions (NEW in v2.22.21)
+│   ├── type-structures.ts      # Type structure definitions (NEW in v2.22.21)
+│   ├── instance-context.ts     # Multi-tenant instance configuration
+│   └── session-state.ts        # Session persistence types (NEW in v2.24.1)
 ├── constants/
 │   └── type-structures.ts      # 22 complete type structures (NEW in v2.22.21)
 ├── templates/
@@ -64,7 +66,9 @@ src/
 │   ├── console-manager.ts     # Console output isolation (NEW in v2.3.1)
 │   └── logger.ts              # Logging utility with HTTP awareness
 ├── http-server-single-session.ts  # Single-session HTTP server (NEW in v2.3.1)
+│                                   # Session persistence API (NEW in v2.24.1)
 ├── mcp-engine.ts              # Clean API for service integration (NEW in v2.3.1)
+│                                # Session persistence wrappers (NEW in v2.24.1)
 └── index.ts                   # Library exports
 ```

@@ -191,6 +195,35 @@ The MCP server exposes tools in several categories:
 ### Development Best Practices
 - Run typecheck and lint after every code change

+### Session Persistence Feature (v2.24.1)
+
+**Location:**
+- Types: `src/types/session-state.ts`
+- Implementation: `src/http-server-single-session.ts` (lines 698-702, 1444-1584)
+- Wrapper: `src/mcp-engine.ts` (lines 123-169)
+- Tests: `tests/unit/http-server/session-persistence.test.ts`, `tests/unit/mcp-engine/session-persistence.test.ts`
+
+**Key Features:**
+- **Export/Restore API**: `exportSessionState()` and `restoreSessionState()` methods
+- **Multi-tenant support**: Enables zero-downtime deployments for SaaS platforms
+- **Security-first**: API keys exported as plaintext - downstream MUST encrypt
+- **Dormant sessions**: Restored sessions recreate transports on first request
+- **Automatic expiration**: Respects `sessionTimeout` setting (default 30 min)
+- **MAX_SESSIONS limit**: Caps at 100 concurrent sessions
+
+**Important Implementation Notes:**
+- Only exports sessions with valid n8nApiUrl and n8nApiKey in context
+- Skips expired sessions during both export and restore
+- Uses `validateInstanceContext()` for data integrity checks
+- Handles null/invalid session gracefully with warnings
+- Session metadata (timestamps) and context (credentials) are persisted
+- Transport and server objects are NOT persisted (recreated on-demand)
+
+**Testing:**
+- 22 unit tests covering export, restore, edge cases, and round-trip cycles
+- Tests use current timestamps to avoid expiration issues
+- Integration with multi-tenant backends documented in README.md
+
 # important-instruction-reminders
 Do what has been asked; nothing more, nothing less.
 NEVER create files unless they're absolutely necessary for achieving your goal.
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
  "name": "n8n-mcp",
-  "version": "2.24.0",
+  "version": "2.24.1",
  "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
  "main": "dist/index.js",
  "types": "dist/index.d.ts",
--- a/src/http-server-single-session.ts
+++ b/src/http-server-single-session.ts
@@ -25,6 +25,7 @@ import {
  STANDARD_PROTOCOL_VERSION
 } from './utils/protocol-version';
 import { InstanceContext, validateInstanceContext } from './types/instance-context';
+import { SessionState } from './types/session-state';

 dotenv.config();

@@ -71,6 +72,30 @@ function extractMultiTenantHeaders(req: express.Request): MultiTenantHeaders {
  };
 }

+/**
+ * Security logging helper for audit trails
+ * Provides structured logging for security-relevant events
+ */
+function logSecurityEvent(
+  event: 'session_export' | 'session_restore' | 'session_restore_failed' | 'max_sessions_reached',
+  details: {
+    sessionId?: string;
+    reason?: string;
+    count?: number;
+    instanceId?: string;
+  }
+): void {
+  const timestamp = new Date().toISOString();
+  const logEntry = {
+    timestamp,
+    event,
+    ...details
+  };
+
+  // Log to standard logger with [SECURITY] prefix for easy filtering
+  logger.info(`[SECURITY] ${event}`, logEntry);
+}
+
 export class SingleSessionHTTPServer {
  // Map to store transports by session ID (following SDK pattern)
  private transports: { [sessionId: string]: StreamableHTTPServerTransport } = {};
@@ -687,7 +712,20 @@ export class SingleSessionHTTPServer {
    if (!this.session) return true;
    return Date.now() - this.session.lastAccess.getTime() > this.sessionTimeout;
  }
-  
+
+  /**
+   * Check if a specific session is expired based on sessionId
+   * Used for multi-session expiration checks during export/restore
+   *
+   * @param sessionId - The session ID to check
+   * @returns true if session is expired or doesn't exist
+   */
+  private isSessionExpired(sessionId: string): boolean {
+    const metadata = this.sessionMetadata[sessionId];
+    if (!metadata) return true;
+    return Date.now() - metadata.lastAccess.getTime() > this.sessionTimeout;
+  }
+
  /**
   * Start the HTTP server
   */
@@ -1406,6 +1444,197 @@ export class SingleSessionHTTPServer {
      }
    };
  }
+
+  /**
+   * Export all active session state for persistence
+   *
+   * Used by multi-tenant backends to dump sessions before container restart.
+   * This method exports the minimal state needed to restore sessions after
+   * a restart: session metadata (timing) and instance context (credentials).
+   *
+   * Transport and server objects are NOT persisted - they will be recreated
+   * on the first request after restore.
+   *
+   * SECURITY WARNING: The exported data contains plaintext n8n API keys.
+   * The downstream application MUST encrypt this data before persisting to disk.
+   *
+   * @returns Array of session state objects, excluding expired sessions
+   *
+   * @example
+   * // Before shutdown
+   * const sessions = server.exportSessionState();
+   * await saveToEncryptedStorage(sessions);
+   */
+  public exportSessionState(): SessionState[] {
+    const sessions: SessionState[] = [];
+    const seenSessionIds = new Set<string>();
+
+    // Iterate over all sessions with metadata (source of truth for active sessions)
+    for (const sessionId of Object.keys(this.sessionMetadata)) {
+      // Check for duplicates (defensive programming)
+      if (seenSessionIds.has(sessionId)) {
+        logger.warn(`Duplicate sessionId detected during export: ${sessionId}`);
+        continue;
+      }
+
+      // Skip expired sessions - they're not worth persisting
+      if (this.isSessionExpired(sessionId)) {
+        continue;
+      }
+
+      const metadata = this.sessionMetadata[sessionId];
+      const context = this.sessionContexts[sessionId];
+
+      // Skip sessions without context - these can't be restored meaningfully
+      // (Context is required to reconnect to the correct n8n instance)
+      if (!context || !context.n8nApiUrl || !context.n8nApiKey) {
+        logger.debug(`Skipping session ${sessionId} - missing required context`);
+        continue;
+      }
+
+      seenSessionIds.add(sessionId);
+      sessions.push({
+        sessionId,
+        metadata: {
+          createdAt: metadata.createdAt.toISOString(),
+          lastAccess: metadata.lastAccess.toISOString()
+        },
+        context: {
+          n8nApiUrl: context.n8nApiUrl,
+          n8nApiKey: context.n8nApiKey,
+          instanceId: context.instanceId || sessionId, // Use sessionId as fallback
+          sessionId: context.sessionId,
+          metadata: context.metadata
+        }
+      });
+    }
+
+    logger.info(`Exported ${sessions.length} session(s) for persistence`);
+    logSecurityEvent('session_export', { count: sessions.length });
+    return sessions;
+  }
+
+  /**
+   * Restore session state from previously exported data
+   *
+   * Used by multi-tenant backends to restore sessions after container restart.
+   * This method restores only the session metadata and instance context.
+   * Transport and server objects will be recreated on the first request.
+   *
+   * Restored sessions are "dormant" until a client makes a request, at which
+   * point the transport and server will be initialized normally.
+   *
+   * @param sessions - Array of session state objects from exportSessionState()
+   * @returns Number of sessions successfully restored
+   *
+   * @example
+   * // After startup
+   * const sessions = await loadFromEncryptedStorage();
+   * const count = server.restoreSessionState(sessions);
+   * console.log(`Restored ${count} sessions`);
+   */
+  public restoreSessionState(sessions: SessionState[]): number {
+    let restoredCount = 0;
+
+    for (const sessionState of sessions) {
+      try {
+        // Skip null or invalid session objects
+        if (!sessionState || typeof sessionState !== 'object' || !sessionState.sessionId) {
+          logger.warn('Skipping invalid session state object');
+          continue;
+        }
+
+        // Check if we've hit the MAX_SESSIONS limit (check real-time count)
+        if (Object.keys(this.sessionMetadata).length >= MAX_SESSIONS) {
+          logger.warn(
+            `Reached MAX_SESSIONS limit (${MAX_SESSIONS}), skipping remaining sessions`
+          );
+          logSecurityEvent('max_sessions_reached', { count: MAX_SESSIONS });
+          break;
+        }
+
+        // Skip if session already exists (duplicate sessionId)
+        if (this.sessionMetadata[sessionState.sessionId]) {
+          logger.debug(`Skipping session ${sessionState.sessionId} - already exists`);
+          continue;
+        }
+
+        // Parse and validate dates first
+        const createdAt = new Date(sessionState.metadata.createdAt);
+        const lastAccess = new Date(sessionState.metadata.lastAccess);
+
+        if (isNaN(createdAt.getTime()) || isNaN(lastAccess.getTime())) {
+          logger.warn(
+            `Skipping session ${sessionState.sessionId} - invalid date format`
+          );
+          continue;
+        }
+
+        // Validate session isn't expired
+        const age = Date.now() - lastAccess.getTime();
+        if (age > this.sessionTimeout) {
+          logger.debug(
+            `Skipping session ${sessionState.sessionId} - expired (age: ${Math.round(age / 1000)}s)`
+          );
+          continue;
+        }
+
+        // Validate context exists (TypeScript null narrowing)
+        if (!sessionState.context) {
+          logger.warn(`Skipping session ${sessionState.sessionId} - missing context`);
+          continue;
+        }
+
+        // Validate context structure using existing validation
+        const validation = validateInstanceContext(sessionState.context);
+        if (!validation.valid) {
+          const reason = validation.errors?.join(', ') || 'invalid context';
+          logger.warn(
+            `Skipping session ${sessionState.sessionId} - invalid context: ${reason}`
+          );
+          logSecurityEvent('session_restore_failed', {
+            sessionId: sessionState.sessionId,
+            reason
+          });
+          continue;
+        }
+
+        // Restore session metadata
+        this.sessionMetadata[sessionState.sessionId] = {
+          createdAt,
+          lastAccess
+        };
+
+        // Restore session context
+        this.sessionContexts[sessionState.sessionId] = {
+          n8nApiUrl: sessionState.context.n8nApiUrl,
+          n8nApiKey: sessionState.context.n8nApiKey,
+          instanceId: sessionState.context.instanceId,
+          sessionId: sessionState.context.sessionId,
+          metadata: sessionState.context.metadata
+        };
+
+        logger.debug(`Restored session ${sessionState.sessionId}`);
+        logSecurityEvent('session_restore', {
+          sessionId: sessionState.sessionId,
+          instanceId: sessionState.context.instanceId
+        });
+        restoredCount++;
+      } catch (error) {
+        logger.error(`Failed to restore session ${sessionState.sessionId}:`, error);
+        logSecurityEvent('session_restore_failed', {
+          sessionId: sessionState.sessionId,
+          reason: error instanceof Error ? error.message : 'unknown error'
+        });
+        // Continue with next session - don't let one failure break the entire restore
+      }
+    }
+
+    logger.info(
+      `Restored ${restoredCount}/${sessions.length} session(s) from persistence`
+    );
+    return restoredCount;
+  }
 }

 // Start if called directly
--- a/src/index.ts
+++ b/src/index.ts
@@ -18,6 +18,9 @@ export {
  validateInstanceContext,
  isInstanceContext
 } from './types/instance-context';
+export type {
+  SessionState
+} from './types/session-state';

 // Re-export MCP SDK types for convenience
 export type {
--- a/src/mcp-engine.ts
+++ b/src/mcp-engine.ts
@@ -9,6 +9,7 @@ import { Request, Response } from 'express';
 import { SingleSessionHTTPServer } from './http-server-single-session';
 import { logger } from './utils/logger';
 import { InstanceContext } from './types/instance-context';
+import { SessionState } from './types/session-state';

 export interface EngineHealth {
  status: 'healthy' | 'unhealthy';
@@ -97,7 +98,7 @@ export class N8NMCPEngine {
          total: Math.round(memoryUsage.heapTotal / 1024 / 1024),
          unit: 'MB'
        },
-        version: '2.3.2'
+        version: '2.24.1'
      };
    } catch (error) {
      logger.error('Health check failed:', error);
@@ -106,7 +107,7 @@ export class N8NMCPEngine {
        uptime: 0,
        sessionActive: false,
        memoryUsage: { used: 0, total: 0, unit: 'MB' },
-        version: '2.3.2'
+        version: '2.24.1'
      };
    }
  }
@@ -118,10 +119,58 @@ export class N8NMCPEngine {
  getSessionInfo(): { active: boolean; sessionId?: string; age?: number } {
    return this.server.getSessionInfo();
  }
-  
+
+  /**
+   * Export all active session state for persistence
+   *
+   * Used by multi-tenant backends to dump sessions before container restart.
+   * Returns an array of session state objects containing metadata and credentials.
+   *
+   * SECURITY WARNING: Exported data contains plaintext n8n API keys.
+   * Encrypt before persisting to disk.
+   *
+   * @returns Array of session state objects
+   *
+   * @example
+   * // Before shutdown
+   * const sessions = engine.exportSessionState();
+   * await saveToEncryptedStorage(sessions);
+   */
+  exportSessionState(): SessionState[] {
+    if (!this.server) {
+      logger.warn('Cannot export sessions: server not initialized');
+      return [];
+    }
+    return this.server.exportSessionState();
+  }
+
+  /**
+   * Restore session state from previously exported data
+   *
+   * Used by multi-tenant backends to restore sessions after container restart.
+   * Restores session metadata and instance context. Transports/servers are
+   * recreated on first request.
+   *
+   * @param sessions - Array of session state objects from exportSessionState()
+   * @returns Number of sessions successfully restored
+   *
+   * @example
+   * // After startup
+   * const sessions = await loadFromEncryptedStorage();
+   * const count = engine.restoreSessionState(sessions);
+   * console.log(`Restored ${count} sessions`);
+   */
+  restoreSessionState(sessions: SessionState[]): number {
+    if (!this.server) {
+      logger.warn('Cannot restore sessions: server not initialized');
+      return 0;
+    }
+    return this.server.restoreSessionState(sessions);
+  }
+
  /**
   * Graceful shutdown for service lifecycle
-   * 
+   *
   * @example
   * process.on('SIGTERM', async () => {
   *   await engine.shutdown();
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -1,6 +1,8 @@
 // Export n8n node type definitions and utilities
 export * from './node-types';
 export * from './type-structures';
+export * from './instance-context';
+export * from './session-state';

 export interface MCPServerConfig {
  port: number;
--- a/src/types/session-state.ts
+++ b/src/types/session-state.ts
@@ -0,0 +1,92 @@
+/**
+ * Session persistence types for multi-tenant deployments
+ *
+ * These types support exporting and restoring MCP session state across
+ * container restarts, enabling seamless session persistence in production.
+ */
+
+import { InstanceContext } from './instance-context.js';
+
+/**
+ * Serializable session state for persistence across restarts
+ *
+ * This interface represents the minimal state needed to restore an MCP session
+ * after a container restart. Only the session metadata and instance context are
+ * persisted - transport and server objects are recreated on the first request.
+ *
+ * @example
+ * // Export sessions before shutdown
+ * const sessions = server.exportSessionState();
+ * await saveToEncryptedStorage(sessions);
+ *
+ * @example
+ * // Restore sessions on startup
+ * const sessions = await loadFromEncryptedStorage();
+ * const count = server.restoreSessionState(sessions);
+ * console.log(`Restored ${count} sessions`);
+ */
+export interface SessionState {
+  /**
+   * Unique session identifier
+   * Format: UUID v4 or custom format from MCP proxy
+   */
+  sessionId: string;
+
+  /**
+   * Session timing metadata for expiration tracking
+   */
+  metadata: {
+    /**
+     * When the session was created (ISO 8601 timestamp)
+     * Used to track total session age
+     */
+    createdAt: string;
+
+    /**
+     * When the session was last accessed (ISO 8601 timestamp)
+     * Used to determine if session has expired based on timeout
+     */
+    lastAccess: string;
+  };
+
+  /**
+   * n8n instance context (credentials and configuration)
+   *
+   * Contains the n8n API credentials and instance-specific settings.
+   * This is the critical data needed to reconnect to the correct n8n instance.
+   *
+   * Note: API keys are stored in plaintext. The downstream application
+   * MUST encrypt this data before persisting to disk.
+   */
+  context: {
+    /**
+     * n8n instance API URL
+     * Example: "https://n8n.example.com"
+     */
+    n8nApiUrl: string;
+
+    /**
+     * n8n instance API key (plaintext - encrypt before storage!)
+     * Example: "n8n_api_1234567890abcdef"
+     */
+    n8nApiKey: string;
+
+    /**
+     * Instance identifier (optional)
+     * Custom identifier for tracking which n8n instance this session belongs to
+     */
+    instanceId?: string;
+
+    /**
+     * Session-specific ID (optional)
+     * May differ from top-level sessionId in some proxy configurations
+     */
+    sessionId?: string;
+
+    /**
+     * Additional metadata (optional)
+     * Extensible field for custom application data
+     */
+    metadata?: Record<string, any>;
+  };
+}
--- a/tests/unit/http-server/session-persistence.test.ts
+++ b/tests/unit/http-server/session-persistence.test.ts
@@ -0,0 +1,546 @@
+/**
+ * Unit tests for session persistence API
+ * Tests export and restore functionality for multi-tenant session management
+ */
+
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+import { SingleSessionHTTPServer } from '../../../src/http-server-single-session';
+import { SessionState } from '../../../src/types/session-state';
+
+describe('SingleSessionHTTPServer - Session Persistence', () => {
+  let server: SingleSessionHTTPServer;
+
+  beforeEach(() => {
+    server = new SingleSessionHTTPServer();
+  });
+
+  describe('exportSessionState()', () => {
+    it('should return empty array when no sessions exist', () => {
+      const exported = server.exportSessionState();
+      expect(exported).toEqual([]);
+    });
+
+    it('should export active sessions with all required fields', () => {
+      // Create mock sessions by directly manipulating internal state
+      const sessionId1 = 'test-session-1';
+      const sessionId2 = 'test-session-2';
+
+      // Use current timestamps to avoid expiration
+      const now = new Date();
+      const createdAt1 = new Date(now.getTime() - 10 * 60 * 1000); // 10 minutes ago
+      const lastAccess1 = new Date(now.getTime() - 5 * 60 * 1000);  // 5 minutes ago
+      const createdAt2 = new Date(now.getTime() - 15 * 60 * 1000); // 15 minutes ago
+      const lastAccess2 = new Date(now.getTime() - 3 * 60 * 1000);  // 3 minutes ago
+
+      // Access private properties for testing
+      const serverAny = server as any;
+
+      serverAny.sessionMetadata[sessionId1] = {
+        createdAt: createdAt1,
+        lastAccess: lastAccess1
+      };
+
+      serverAny.sessionContexts[sessionId1] = {
+        n8nApiUrl: 'https://n8n1.example.com',
+        n8nApiKey: 'key1',
+        instanceId: 'instance1',
+        sessionId: sessionId1,
+        metadata: { userId: 'user1' }
+      };
+
+      serverAny.sessionMetadata[sessionId2] = {
+        createdAt: createdAt2,
+        lastAccess: lastAccess2
+      };
+
+      serverAny.sessionContexts[sessionId2] = {
+        n8nApiUrl: 'https://n8n2.example.com',
+        n8nApiKey: 'key2',
+        instanceId: 'instance2'
+      };
+
+      const exported = server.exportSessionState();
+
+      expect(exported).toHaveLength(2);
+
+      // Verify first session
+      expect(exported[0]).toMatchObject({
+        sessionId: sessionId1,
+        metadata: {
+          createdAt: createdAt1.toISOString(),
+          lastAccess: lastAccess1.toISOString()
+        },
+        context: {
+          n8nApiUrl: 'https://n8n1.example.com',
+          n8nApiKey: 'key1',
+          instanceId: 'instance1',
+          sessionId: sessionId1,
+          metadata: { userId: 'user1' }
+        }
+      });
+
+      // Verify second session
+      expect(exported[1]).toMatchObject({
+        sessionId: sessionId2,
+        metadata: {
+          createdAt: createdAt2.toISOString(),
+          lastAccess: lastAccess2.toISOString()
+        },
+        context: {
+          n8nApiUrl: 'https://n8n2.example.com',
+          n8nApiKey: 'key2',
+          instanceId: 'instance2'
+        }
+      });
+    });
+
+    it('should skip expired sessions during export', () => {
+      const serverAny = server as any;
+      const now = Date.now();
+      const sessionTimeout = 30 * 60 * 1000; // 30 minutes (default)
+
+      // Create an active session (accessed recently)
+      serverAny.sessionMetadata['active-session'] = {
+        createdAt: new Date(now - 10 * 60 * 1000), // 10 minutes ago
+        lastAccess: new Date(now - 5 * 60 * 1000)  // 5 minutes ago
+      };
+      serverAny.sessionContexts['active-session'] = {
+        n8nApiUrl: 'https://active.example.com',
+        n8nApiKey: 'active-key',
+        instanceId: 'active-instance'
+      };
+
+      // Create an expired session (last accessed > 30 minutes ago)
+      serverAny.sessionMetadata['expired-session'] = {
+        createdAt: new Date(now - 60 * 60 * 1000), // 60 minutes ago
+        lastAccess: new Date(now - 45 * 60 * 1000) // 45 minutes ago (expired)
+      };
+      serverAny.sessionContexts['expired-session'] = {
+        n8nApiUrl: 'https://expired.example.com',
+        n8nApiKey: 'expired-key',
+        instanceId: 'expired-instance'
+      };
+
+      const exported = server.exportSessionState();
+
+      expect(exported).toHaveLength(1);
+      expect(exported[0].sessionId).toBe('active-session');
+    });
+
+    it('should skip sessions without required context fields', () => {
+      const serverAny = server as any;
+
+      // Session with complete context
+      serverAny.sessionMetadata['complete-session'] = {
+        createdAt: new Date(),
+        lastAccess: new Date()
+      };
+      serverAny.sessionContexts['complete-session'] = {
+        n8nApiUrl: 'https://complete.example.com',
+        n8nApiKey: 'complete-key',
+        instanceId: 'complete-instance'
+      };
+
+      // Session with missing n8nApiUrl
+      serverAny.sessionMetadata['missing-url'] = {
+        createdAt: new Date(),
+        lastAccess: new Date()
+      };
+      serverAny.sessionContexts['missing-url'] = {
+        n8nApiKey: 'key',
+        instanceId: 'instance'
+      };
+
+      // Session with missing n8nApiKey
+      serverAny.sessionMetadata['missing-key'] = {
+        createdAt: new Date(),
+        lastAccess: new Date()
+      };
+      serverAny.sessionContexts['missing-key'] = {
+        n8nApiUrl: 'https://example.com',
+        instanceId: 'instance'
+      };
+
+      // Session with no context at all
+      serverAny.sessionMetadata['no-context'] = {
+        createdAt: new Date(),
+        lastAccess: new Date()
+      };
+
+      const exported = server.exportSessionState();
+
+      expect(exported).toHaveLength(1);
+      expect(exported[0].sessionId).toBe('complete-session');
+    });
+
+    it('should use sessionId as fallback for instanceId', () => {
+      const serverAny = server as any;
+      const sessionId = 'test-session';
+
+      serverAny.sessionMetadata[sessionId] = {
+        createdAt: new Date(),
+        lastAccess: new Date()
+      };
+      serverAny.sessionContexts[sessionId] = {
+        n8nApiUrl: 'https://example.com',
+        n8nApiKey: 'key'
+        // No instanceId provided
+      };
+
+      const exported = server.exportSessionState();
+
+      expect(exported).toHaveLength(1);
+      expect(exported[0].context.instanceId).toBe(sessionId);
+    });
+  });
+
+  describe('restoreSessionState()', () => {
+    it('should restore valid sessions correctly', () => {
+      const sessions: SessionState[] = [
+        {
+          sessionId: 'restored-session-1',
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://restored1.example.com',
+            n8nApiKey: 'restored-key-1',
+            instanceId: 'restored-instance-1'
+          }
+        },
+        {
+          sessionId: 'restored-session-2',
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://restored2.example.com',
+            n8nApiKey: 'restored-key-2',
+            instanceId: 'restored-instance-2',
+            sessionId: 'custom-session-id',
+            metadata: { custom: 'data' }
+          }
+        }
+      ];
+
+      const count = server.restoreSessionState(sessions);
+
+      expect(count).toBe(2);
+
+      // Verify sessions were restored by checking internal state
+      const serverAny = server as any;
+
+      expect(serverAny.sessionMetadata['restored-session-1']).toBeDefined();
+      expect(serverAny.sessionContexts['restored-session-1']).toMatchObject({
+        n8nApiUrl: 'https://restored1.example.com',
+        n8nApiKey: 'restored-key-1',
+        instanceId: 'restored-instance-1'
+      });
+
+      expect(serverAny.sessionMetadata['restored-session-2']).toBeDefined();
+      expect(serverAny.sessionContexts['restored-session-2']).toMatchObject({
+        n8nApiUrl: 'https://restored2.example.com',
+        n8nApiKey: 'restored-key-2',
+        instanceId: 'restored-instance-2',
+        sessionId: 'custom-session-id',
+        metadata: { custom: 'data' }
+      });
+    });
+
+    it('should skip expired sessions during restore', () => {
+      const now = Date.now();
+      const sessionTimeout = 30 * 60 * 1000; // 30 minutes
+
+      const sessions: SessionState[] = [
+        {
+          sessionId: 'active-session',
+          metadata: {
+            createdAt: new Date(now - 10 * 60 * 1000).toISOString(),
+            lastAccess: new Date(now - 5 * 60 * 1000).toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://active.example.com',
+            n8nApiKey: 'active-key',
+            instanceId: 'active-instance'
+          }
+        },
+        {
+          sessionId: 'expired-session',
+          metadata: {
+            createdAt: new Date(now - 60 * 60 * 1000).toISOString(),
+            lastAccess: new Date(now - 45 * 60 * 1000).toISOString() // Expired
+          },
+          context: {
+            n8nApiUrl: 'https://expired.example.com',
+            n8nApiKey: 'expired-key',
+            instanceId: 'expired-instance'
+          }
+        }
+      ];
+
+      const count = server.restoreSessionState(sessions);
+
+      expect(count).toBe(1);
+
+      const serverAny = server as any;
+      expect(serverAny.sessionMetadata['active-session']).toBeDefined();
+      expect(serverAny.sessionMetadata['expired-session']).toBeUndefined();
+    });
+
+    it('should skip sessions with missing required context fields', () => {
+      const sessions: SessionState[] = [
+        {
+          sessionId: 'valid-session',
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://valid.example.com',
+            n8nApiKey: 'valid-key',
+            instanceId: 'valid-instance'
+          }
+        },
+        {
+          sessionId: 'missing-url',
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: '', // Empty URL
+            n8nApiKey: 'key',
+            instanceId: 'instance'
+          }
+        },
+        {
+          sessionId: 'missing-key',
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://example.com',
+            n8nApiKey: '', // Empty key
+            instanceId: 'instance'
+          }
+        }
+      ];
+
+      const count = server.restoreSessionState(sessions);
+
+      expect(count).toBe(1);
+
+      const serverAny = server as any;
+      expect(serverAny.sessionMetadata['valid-session']).toBeDefined();
+      expect(serverAny.sessionMetadata['missing-url']).toBeUndefined();
+      expect(serverAny.sessionMetadata['missing-key']).toBeUndefined();
+    });
+
+    it('should skip duplicate sessionIds', () => {
+      const serverAny = server as any;
+
+      // Create an existing session
+      serverAny.sessionMetadata['existing-session'] = {
+        createdAt: new Date(),
+        lastAccess: new Date()
+      };
+
+      const sessions: SessionState[] = [
+        {
+          sessionId: 'new-session',
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://new.example.com',
+            n8nApiKey: 'new-key',
+            instanceId: 'new-instance'
+          }
+        },
+        {
+          sessionId: 'existing-session', // Duplicate
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://duplicate.example.com',
+            n8nApiKey: 'duplicate-key',
+            instanceId: 'duplicate-instance'
+          }
+        }
+      ];
+
+      const count = server.restoreSessionState(sessions);
+
+      expect(count).toBe(1);
+      expect(serverAny.sessionMetadata['new-session']).toBeDefined();
+    });
+
+    it('should handle restore failures gracefully', () => {
+      const sessions: any[] = [
+        {
+          sessionId: 'valid-session',
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://valid.example.com',
+            n8nApiKey: 'valid-key',
+            instanceId: 'valid-instance'
+          }
+        },
+        {
+          sessionId: 'bad-session',
+          metadata: {}, // Missing required fields
+          context: null // Invalid context
+        },
+        null, // Invalid session
+        {
+          // Missing sessionId
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://example.com',
+            n8nApiKey: 'key',
+            instanceId: 'instance'
+          }
+        }
+      ];
+
+      // Should not throw and should restore only the valid session
+      expect(() => {
+        const count = server.restoreSessionState(sessions);
+        expect(count).toBe(1); // Only valid-session should be restored
+      }).not.toThrow();
+
+      // Verify the valid session was restored
+      const serverAny = server as any;
+      expect(serverAny.sessionMetadata['valid-session']).toBeDefined();
+    });
+
+    it('should respect MAX_SESSIONS limit during restore', () => {
+      // Create 99 existing sessions (MAX_SESSIONS is 100)
+      const serverAny = server as any;
+      const now = new Date();
+      for (let i = 0; i < 99; i++) {
+        serverAny.sessionMetadata[`existing-${i}`] = {
+          createdAt: now,
+          lastAccess: now
+        };
+      }
+
+      // Try to restore 3 sessions (should only restore 1 due to limit)
+      const sessions: SessionState[] = [];
+      for (let i = 0; i < 3; i++) {
+        sessions.push({
+          sessionId: `new-session-${i}`,
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: `https://new${i}.example.com`,
+            n8nApiKey: `new-key-${i}`,
+            instanceId: `new-instance-${i}`
+          }
+        });
+      }
+
+      const count = server.restoreSessionState(sessions);
+
+      expect(count).toBe(1);
+      expect(serverAny.sessionMetadata['new-session-0']).toBeDefined();
+      expect(serverAny.sessionMetadata['new-session-1']).toBeUndefined();
+      expect(serverAny.sessionMetadata['new-session-2']).toBeUndefined();
+    });
+
+    it('should parse ISO 8601 timestamps correctly', () => {
+      // Use current timestamps to avoid expiration
+      const now = new Date();
+      const createdAtDate = new Date(now.getTime() - 10 * 60 * 1000); // 10 minutes ago
+      const lastAccessDate = new Date(now.getTime() - 5 * 60 * 1000);  // 5 minutes ago
+      const createdAt = createdAtDate.toISOString();
+      const lastAccess = lastAccessDate.toISOString();
+
+      const sessions: SessionState[] = [
+        {
+          sessionId: 'timestamp-session',
+          metadata: { createdAt, lastAccess },
+          context: {
+            n8nApiUrl: 'https://example.com',
+            n8nApiKey: 'key',
+            instanceId: 'instance'
+          }
+        }
+      ];
+
+      const count = server.restoreSessionState(sessions);
+      expect(count).toBe(1);
+
+      const serverAny = server as any;
+      const metadata = serverAny.sessionMetadata['timestamp-session'];
+
+      expect(metadata.createdAt).toBeInstanceOf(Date);
+      expect(metadata.lastAccess).toBeInstanceOf(Date);
+      expect(metadata.createdAt.toISOString()).toBe(createdAt);
+      expect(metadata.lastAccess.toISOString()).toBe(lastAccess);
+    });
+  });
+
+  describe('Round-trip export and restore', () => {
+    it('should preserve data through export → restore cycle', () => {
+      // Create sessions with current timestamps
+      const serverAny = server as any;
+      const now = new Date();
+      const createdAt = new Date(now.getTime() - 10 * 60 * 1000); // 10 minutes ago
+      const lastAccess = new Date(now.getTime() - 5 * 60 * 1000);  // 5 minutes ago
+
+      serverAny.sessionMetadata['session-1'] = {
+        createdAt,
+        lastAccess
+      };
+      serverAny.sessionContexts['session-1'] = {
+        n8nApiUrl: 'https://n8n1.example.com',
+        n8nApiKey: 'key1',
+        instanceId: 'instance1',
+        sessionId: 'custom-id-1',
+        metadata: { userId: 'user1', role: 'admin' }
+      };
+
+      // Export sessions
+      const exported = server.exportSessionState();
+      expect(exported).toHaveLength(1);
+
+      // Clear sessions
+      delete serverAny.sessionMetadata['session-1'];
+      delete serverAny.sessionContexts['session-1'];
+
+      // Restore sessions
+      const count = server.restoreSessionState(exported);
+      expect(count).toBe(1);
+
+      // Verify data integrity
+      const metadata = serverAny.sessionMetadata['session-1'];
+      const context = serverAny.sessionContexts['session-1'];
+
+      expect(metadata.createdAt.toISOString()).toBe(createdAt.toISOString());
+      expect(metadata.lastAccess.toISOString()).toBe(lastAccess.toISOString());
+
+      expect(context).toMatchObject({
+        n8nApiUrl: 'https://n8n1.example.com',
+        n8nApiKey: 'key1',
+        instanceId: 'instance1',
+        sessionId: 'custom-id-1',
+        metadata: { userId: 'user1', role: 'admin' }
+      });
+    });
+  });
+});
--- a/tests/unit/mcp-engine/session-persistence.test.ts
+++ b/tests/unit/mcp-engine/session-persistence.test.ts
@@ -0,0 +1,255 @@
+/**
+ * Unit tests for N8NMCPEngine session persistence wrapper methods
+ */
+
+import { describe, it, expect, beforeEach } from 'vitest';
+import { N8NMCPEngine } from '../../../src/mcp-engine';
+import { SessionState } from '../../../src/types/session-state';
+
+describe('N8NMCPEngine - Session Persistence', () => {
+  let engine: N8NMCPEngine;
+
+  beforeEach(() => {
+    engine = new N8NMCPEngine({
+      sessionTimeout: 30 * 60 * 1000,
+      logLevel: 'error' // Quiet during tests
+    });
+  });
+
+  describe('exportSessionState()', () => {
+    it('should return empty array when no sessions exist', () => {
+      const exported = engine.exportSessionState();
+      expect(exported).toEqual([]);
+    });
+
+    it('should delegate to underlying server', () => {
+      // Access private server to create test sessions
+      const engineAny = engine as any;
+      const server = engineAny.server;
+      const serverAny = server as any;
+
+      // Create a mock session
+      serverAny.sessionMetadata['test-session'] = {
+        createdAt: new Date(),
+        lastAccess: new Date()
+      };
+      serverAny.sessionContexts['test-session'] = {
+        n8nApiUrl: 'https://test.example.com',
+        n8nApiKey: 'test-key',
+        instanceId: 'test-instance'
+      };
+
+      const exported = engine.exportSessionState();
+
+      expect(exported).toHaveLength(1);
+      expect(exported[0].sessionId).toBe('test-session');
+      expect(exported[0].context.n8nApiUrl).toBe('https://test.example.com');
+    });
+
+    it('should handle server not initialized', () => {
+      // Create engine without server
+      const engineAny = {} as N8NMCPEngine;
+      const exportMethod = N8NMCPEngine.prototype.exportSessionState.bind(engineAny);
+
+      // Should not throw, should return empty array
+      expect(() => exportMethod()).not.toThrow();
+      const result = exportMethod();
+      expect(result).toEqual([]);
+    });
+  });
+
+  describe('restoreSessionState()', () => {
+    it('should restore sessions via underlying server', () => {
+      const sessions: SessionState[] = [
+        {
+          sessionId: 'restored-session',
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://restored.example.com',
+            n8nApiKey: 'restored-key',
+            instanceId: 'restored-instance'
+          }
+        }
+      ];
+
+      const count = engine.restoreSessionState(sessions);
+
+      expect(count).toBe(1);
+
+      // Verify session was restored
+      const engineAny = engine as any;
+      const server = engineAny.server;
+      const serverAny = server as any;
+
+      expect(serverAny.sessionMetadata['restored-session']).toBeDefined();
+      expect(serverAny.sessionContexts['restored-session']).toMatchObject({
+        n8nApiUrl: 'https://restored.example.com',
+        n8nApiKey: 'restored-key',
+        instanceId: 'restored-instance'
+      });
+    });
+
+    it('should return 0 when restoring empty array', () => {
+      const count = engine.restoreSessionState([]);
+      expect(count).toBe(0);
+    });
+
+    it('should handle server not initialized', () => {
+      const engineAny = {} as N8NMCPEngine;
+      const restoreMethod = N8NMCPEngine.prototype.restoreSessionState.bind(engineAny);
+
+      const sessions: SessionState[] = [
+        {
+          sessionId: 'test',
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://test.example.com',
+            n8nApiKey: 'test-key',
+            instanceId: 'test-instance'
+          }
+        }
+      ];
+
+      // Should not throw, should return 0
+      expect(() => restoreMethod(sessions)).not.toThrow();
+      const result = restoreMethod(sessions);
+      expect(result).toBe(0);
+    });
+
+    it('should return count of successfully restored sessions', () => {
+      const now = Date.now();
+      const sessions: SessionState[] = [
+        {
+          sessionId: 'valid-1',
+          metadata: {
+            createdAt: new Date(now - 10 * 60 * 1000).toISOString(),
+            lastAccess: new Date(now - 5 * 60 * 1000).toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://valid1.example.com',
+            n8nApiKey: 'key1',
+            instanceId: 'instance1'
+          }
+        },
+        {
+          sessionId: 'valid-2',
+          metadata: {
+            createdAt: new Date(now - 10 * 60 * 1000).toISOString(),
+            lastAccess: new Date(now - 5 * 60 * 1000).toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://valid2.example.com',
+            n8nApiKey: 'key2',
+            instanceId: 'instance2'
+          }
+        },
+        {
+          sessionId: 'expired',
+          metadata: {
+            createdAt: new Date(now - 60 * 60 * 1000).toISOString(),
+            lastAccess: new Date(now - 45 * 60 * 1000).toISOString() // Expired
+          },
+          context: {
+            n8nApiUrl: 'https://expired.example.com',
+            n8nApiKey: 'expired-key',
+            instanceId: 'expired-instance'
+          }
+        }
+      ];
+
+      const count = engine.restoreSessionState(sessions);
+
+      expect(count).toBe(2); // Only 2 valid sessions
+    });
+  });
+
+  describe('Round-trip through engine', () => {
+    it('should preserve sessions through export → restore cycle', () => {
+      // Create mock sessions with current timestamps
+      const engineAny = engine as any;
+      const server = engineAny.server;
+      const serverAny = server as any;
+
+      const now = new Date();
+      const createdAt = new Date(now.getTime() - 10 * 60 * 1000); // 10 minutes ago
+      const lastAccess = new Date(now.getTime() - 5 * 60 * 1000);  // 5 minutes ago
+
+      serverAny.sessionMetadata['engine-session'] = {
+        createdAt,
+        lastAccess
+      };
+      serverAny.sessionContexts['engine-session'] = {
+        n8nApiUrl: 'https://engine-test.example.com',
+        n8nApiKey: 'engine-key',
+        instanceId: 'engine-instance',
+        metadata: { env: 'production' }
+      };
+
+      // Export via engine
+      const exported = engine.exportSessionState();
+      expect(exported).toHaveLength(1);
+
+      // Clear sessions
+      delete serverAny.sessionMetadata['engine-session'];
+      delete serverAny.sessionContexts['engine-session'];
+
+      // Restore via engine
+      const count = engine.restoreSessionState(exported);
+      expect(count).toBe(1);
+
+      // Verify data
+      expect(serverAny.sessionMetadata['engine-session']).toBeDefined();
+      expect(serverAny.sessionContexts['engine-session']).toMatchObject({
+        n8nApiUrl: 'https://engine-test.example.com',
+        n8nApiKey: 'engine-key',
+        instanceId: 'engine-instance',
+        metadata: { env: 'production' }
+      });
+    });
+  });
+
+  describe('Integration with getSessionInfo()', () => {
+    it('should reflect restored sessions in session info', () => {
+      const sessions: SessionState[] = [
+        {
+          sessionId: 'info-session-1',
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://info1.example.com',
+            n8nApiKey: 'info-key-1',
+            instanceId: 'info-instance-1'
+          }
+        },
+        {
+          sessionId: 'info-session-2',
+          metadata: {
+            createdAt: new Date().toISOString(),
+            lastAccess: new Date().toISOString()
+          },
+          context: {
+            n8nApiUrl: 'https://info2.example.com',
+            n8nApiKey: 'info-key-2',
+            instanceId: 'info-instance-2'
+          }
+        }
+      ];
+
+      engine.restoreSessionState(sessions);
+
+      const info = engine.getSessionInfo();
+
+      // Note: getSessionInfo() reflects metadata, not transports
+      // Restored sessions won't have transports until first request
+      expect(info).toBeDefined();
+    });
+  });
+});