# Session Management Implementation Guide
## Overview
The Codex MCP Server provides advanced session management with native Codex CLI v0.50.0+ integration, enabling persistent conversational context and sophisticated AI coding assistance.
## Architecture
### Session Storage
- **In-memory Map-based storage** with automatic cleanup
- **UUID-based session IDs** for unique identification
- **TTL management** - 24 hour automatic session expiration
- **Session limit enforcement** - maximum 100 concurrent sessions
### Enhanced Session Data Structure
```typescript
interface SessionData {
id: string;
createdAt: Date;
lastAccessedAt: Date;
turns: ConversationTurn[];
codexConversationId?: string; // Native Codex conversation ID
}
interface ConversationTurn {
prompt: string;
response: string;
timestamp: Date;
}
```
### Native Codex Integration
- **Automatic conversation ID extraction** from Codex CLI output
- **Resume functionality** using `codex resume <conversation-id>`
- **Fallback context building** when native resume unavailable
- **Model consistency** across session interactions
### Tool Enhancements
#### Enhanced Codex Tool
- **sessionId** (optional): Session ID for conversational context
- **resetSession** (optional): Reset session history before processing
- **model** (optional): Model selection (defaults to `gpt-5-codex`)
- **reasoningEffort** (optional): Control reasoning depth (low/medium/high)
- **Smart context building**: Uses native resume or fallback context
- **Robust error handling**: Graceful degradation for various failure modes
#### ListSessions Tool
- **Session enumeration**: Returns all active session IDs with comprehensive metadata
- **Session introspection**: Creation time, last access, turn count, conversation ID
- **Management interface**: Enables session lifecycle monitoring
## Implementation Status ✅
### ✅ Completed Features
1. **Session Storage System**
- InMemorySessionStorage with TTL and cleanup
- Defensive programming against data corruption
- Conversation ID tracking and management
2. **Enhanced Codex Tool Handler**
- Native resume functionality with fallback
- GPT-5-Codex as intelligent default model
- Model and reasoning effort parameter support
- Comprehensive error handling and validation
3. **ListSessions Tool**
- Complete session metadata exposure
- JSON-formatted session information
- Real-time session status tracking
4. **Robust Testing Suite**
- 54 comprehensive tests covering all functionality
- Edge case handling and error scenario validation
- Integration testing with Codex CLI interactions
## Advanced Benefits
- **Native Codex Resume**: Optimal conversation continuity using Codex CLI's built-in resume feature
- **Intelligent Defaults**: GPT-5-Codex model selection for superior coding assistance
- **Production-Ready**: Comprehensive error handling, data validation, and graceful degradation
- **Enterprise-Scale**: Session management suitable for professional development workflows
- **Flexible Configuration**: Per-request model and reasoning effort customization
## Usage Patterns
### Basic Session Usage
```bash
# Automatic session creation with optimal defaults
codex "Analyze this authentication system"
# Explicit session management
codex --sessionId "auth-review" "Continue analysis"
codex --sessionId "auth-review" --resetSession true "Start fresh review"
```
### Advanced Configuration
```bash
# Model and reasoning control
codex --model "gpt-4" --reasoningEffort "high" "Complex architectural analysis"
# Session with custom parameters
codex --sessionId "deep-dive" --model "gpt-4" --reasoningEffort "high" "Advanced optimization review"
# Session management
listSessions # View all active sessions
```
## Technical Architecture
### Command Flow
```mermaid
graph TD
A[User Request] --> B{Session ID provided?}
B -->|Yes| C{Reset Session?}
B -->|No| D[Direct Execution]
C -->|Yes| E[Clear Session History]
C -->|No| F{Codex Conversation ID exists?}
E --> G[Execute with Default Model]
F -->|Yes| H[Use Codex Resume]
F -->|No| I[Build Enhanced Context]
H --> J[Execute with Parameters]
I --> J
G --> K[Extract Conversation ID]
J --> L[Save Turn to Session]
D --> M[Execute with Default Model]
K --> L
M --> N[Return Response]
L --> N
```
### Error Handling Strategy
- **Graceful Degradation**: System continues operation even with corrupted session data
- **Defensive Programming**: Validates array structures and handles null/undefined gracefully
- **Comprehensive Logging**: Error context preserved for debugging and monitoring
- **Fallback Mechanisms**: Manual context building when native resume fails
### Performance Considerations
- **Memory Management**: Automatic cleanup of expired sessions (24hr TTL)
- **Session Limits**: Maximum 100 concurrent sessions to prevent memory exhaustion
- **Context Optimization**: Only recent turns (last 2) used for manual context building
- **Efficient Storage**: Minimal session metadata for optimal memory usage
