MCP Task Relay

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MCP Task Relay is a production-ready Model Context Protocol (MCP) server that exposes a sophisticated scheduler/executor workflow for autonomous agents. Built with enterprise-grade reliability, it features an intelligent Ask/Answer protocol with cryptographic context verification, preventing context drift while reducing token usage by 95%+.

Architecture Overview

┌─────────────┐     MCP Protocol     ┌──────────────┐
│   MCP       │ ◄──────────────────► │  Scheduler   │
│  Clients    │    (stdio/SSE)       │   (Relay)    │
│ (Claude/    │                      │              │
│  Codex)     │                      │  ┌────────┐  │
└─────────────┘                      │  │Answer  │  │
                                     │  │Runner  │  │
                                     │  │(LLM)   │  │
                                     │  └────────┘  │
                                     │      ▲       │
                                     │      │ Ask   │
                                     │      ▼       │
       ┌─────────────────────────────┤  ┌────────┐ │
       │   Ask/Answer Protocol       │  │Context │ │
       │   (Context Envelope)        │  │Envelope│ │
       │   ┌──────────────┐          │  │+ Hash  │ │
       │   │ Executor SDK │ ◄────────┤  └────────┘ │
       │   └──────────────┘          │              │
       │   Job Execution             └──────────────┘
       │   Environment
       └──────────────────────────────────────────────┘

Key Innovation: Context Envelope Protocol with SHA-256 verification ensures perfect context alignment between Executor and Answer Runner, eliminating context drift while minimizing token overhead.

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✨ Key Features

🔐 Context Envelope Protocol

Prevents context drift through explicit, verifiable context snapshots:

• Cryptographic Verification: SHA-256 hash ensures context integrity
• Token Optimization: ~50 tokens (minimal) vs 10k-50k tokens (full history)
• Zero Session Memory: Each Ask processed independently with complete context reconstruction
• Answer Attestation: Cryptographic proof of context/role/model/tools used

🤖 Intelligent Ask/Answer System

• Four-Layer Prompt Architecture: Base → Role → Context → Task
• Role Catalog: YAML-based extensible role definitions
• LLM Integration: Anthropic Claude with automatic retry and validation
• JSON Schema Validation: Type-safe responses with schema enforcement
• Decision Caching: Eliminates redundant LLM calls for identical queries

💾 Enterprise-Grade Storage

• SQLite with WAL Mode: High-performance concurrent access
• Automatic Schema Management: No manual migrations required
• In-Memory Mode: Perfect for testing and CI/CD
• Full Audit Trail: Complete event tracking for all state transitions

📊 Production Observability

• Structured Logging: JSON logs via Pino
• Real-Time Updates: Server-Sent Events (SSE) for job/ask status
• Comprehensive Metrics: Request latency, cache hit rates, token usage

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🚀 Quick Start

Prerequisites

• Node.js ≥ 20
• npm or bun 1.3+
• Anthropic API Key (for Answer Runner)

Installation

# NPM (recommended for production)
npm install -g mcp-task-relay

# Or use npx for one-off execution
npx -y mcp-task-relay@latest serve --profile dev

Basic Usage

# Start with in-memory storage (development)
mcp-task-relay serve \
  --profile dev \
  --storage memory \
  --config-dir ./.mcp-task-relay

# Start with persistent storage (production)
export ANTHROPIC_API_KEY="sk-ant-..."
mcp-task-relay serve \
  --profile prod \
  --storage sqlite \
  --sqlite ./data/relay.db \
  --config-dir ./config

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📖 Configuration

CLI Options

Flag	Description	Environment Variable
--profile <env>	Environment profile (dev/staging/prod)	TASK_RELAY_PROFILE
--config-dir <dir>	Configuration directory path	TASK_RELAY_CONFIG_DIR
--storage <type>	Storage backend (memory/sqlite)	TASK_RELAY_STORAGE
--sqlite <path>	SQLite database file path	TASK_RELAY_SQLITE_URL
--transport <type>	Transport protocol (stdio only in Phase 2)	TASK_RELAY_TRANSPORT

Environment Variables

Required:

• ANTHROPIC_API_KEY — Anthropic API key for Answer Runner

Optional:

• TASK_RELAY_PROMPTS_DIR — Custom prompts directory
• TASK_RELAY_SCHEMATA_DIR — Custom JSON schemas directory
• TASK_RELAY_POLICY_FILE — Custom policy YAML file
• TASK_RELAY_ANSWER_RUNNER_ENABLED — Enable/disable Answer Runner (default: true)

Context Envelope (Executor-side):

• TASK_RELAY_JOB_ID — Current job identifier
• TASK_RELAY_STEP_ID — Current execution step
• TASK_RELAY_REPO — Repository identifier
• TASK_RELAY_COMMIT_SHA — Git commit SHA
• TASK_RELAY_POLICY_VERSION — Policy version
• TASK_RELAY_FACT_* — Custom facts (e.g., TASK_RELAY_FACT_branch=main)

Configuration Directory Structure

.mcp-task-relay/
├── config.yaml              # Main configuration
├── policy.yaml              # Security policy rules
├── prompts/                 # Role definitions
│   ├── role.diff_planner@v1.yaml
│   ├── role.test_planner@v1.yaml
│   └── role.schema_summarizer@v1.yaml
└── schemata/                # JSON Schemas
    ├── ask.schema.json
    ├── answer.schema.json
    └── artifacts/
        ├── diff_plan.schema.json
        └── test_plan.schema.json

Example config.yaml:

askAnswer:
  port: 3415
  longPollTimeoutSec: 25
  sseHeartbeatSec: 10
  runner:
    enabled: true
    model: claude-3-5-sonnet-20241022
    maxRetries: 1
    defaultTimeout: 60

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🔧 MCP Client Integration

Codex CLI

# Add to Codex configuration
codex mcp add task-relay -- \
  mcp-task-relay serve \
  --profile prod \
  --storage sqlite \
  --sqlite ./relay.db

Claude Code (Desktop)

Add to your Claude Code MCP settings (~/.claude-code/mcp.json):

{
  "mcpServers": {
    "task-relay": {
      "command": "mcp-task-relay",
      "args": [
        "serve",
        "--profile", "prod",
        "--storage", "sqlite",
        "--sqlite", "./relay.db"
      ],
      "env": {
        "ANTHROPIC_API_KEY": "sk-ant-..."
      }
    }
  }
}

Gemini Code Assist

# Configure in Gemini workspace settings
gemini config mcp add task-relay \
  --command "mcp-task-relay serve" \
  --args "--profile prod --storage sqlite"

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🎯 Context Envelope Protocol

Overview

The Context Envelope Protocol eliminates context drift through explicit, cryptographically verified context snapshots.

Problem: Traditional approaches require transmitting complete conversation history (10k-50k tokens), causing:

• Massive token usage and cost
• Context window limitations
• Potential context misalignment between Executor and Answer Runner

Solution: Structured context snapshots with SHA-256 verification (50-300 tokens).

Token Usage Comparison

Approach	Token Usage	Context Integrity	Use Case
No Context	~50 tokens	None	Answer Runner blind to context ❌
Context Envelope	50-300 tokens	Cryptographic	Optimal for 95%+ scenarios ✅
Full History	10k-50k tokens	Complete	Complex decisions requiring full context

Context Envelope Structure

Minimal (Default Environment):

{
  "job_snapshot": {},
  "role": "default"
}

Token Cost: ~50 tokens

Typical (Production with Custom Facts):

{
  "job_snapshot": {
    "repo": "github.com/user/repo",
    "commit_sha": "abc123def456...",
    "env_profile": "production",
    "policy_version": "2.0"
  },
  "facts": {
    "branch": "main",
    "pr_number": "123"
  },
  "tool_caps": {
    "database": {
      "timeout_ms": 5000
    }
  },
  "role": "code_reviewer"
}

Token Cost: ~150-200 tokens

Verification Flow

1. Executor builds context_envelope
   └─► Computes SHA-256 hash → context_hash

2. Ask sent with both context_envelope + context_hash

3. Scheduler stores Ask in database

4. Answer Runner retrieves Ask
   ├─► Verifies: computed_hash == stored_hash
   └─► FAIL-FAST on mismatch (E_CONTEXT_MISMATCH)

5. Answer Runner generates response
   └─► Creates attestation with context_hash

6. Answer sent back to Executor

7. Executor verifies attestation
   └─► Ensures context_hash matches original

Error Codes

• E_CONTEXT_MISMATCH — Context hash verification failed
• E_CAPS_VIOLATION — Tool capability constraint violated
• E_NO_CONTEXT_ENVELOPE — Required context envelope missing

Smart Defaults (Token Optimization)

The SDK automatically omits default values to minimize token usage:

• repo: Omitted if "unknown" (default)
• commit_sha: Omitted if "unknown" (default)
• env_profile: Omitted if "dev" (default)
• policy_version: Omitted if "1.0" (default)
• facts: Omitted if empty
• tool_caps: Omitted if no tools specified

Result: 75-85% token reduction in typical scenarios.

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🛠️ Development

Build from Source

# Clone repository
git clone https://github.com/royisme/mcp-task-relay.git
cd mcp-task-relay

# Install dependencies
npm install

# Build
npm run build

# Run tests
npm test

# Link for local development
npm link

Project Structure

src/
├── cli.ts                   # CLI entry point
├── server.ts                # Runtime bootstrap
├── answer-runner/           # LLM-powered answering engine
│   ├── runner.ts            # Core Answer Runner
│   ├── role-catalog.ts      # YAML role loader
│   └── prompt-builder.ts    # 4-layer prompt architecture
├── core/                    # Business logic
│   └── job-manager.ts       # Job orchestration
├── db/                      # Data persistence
│   ├── connection.ts        # SQLite setup
│   ├── asks-repository.ts   # Ask/Answer storage
│   └── answers-repository.ts
├── models/                  # Type definitions
│   ├── schemas.ts           # Zod schemas
│   └── states.ts            # State machine & error codes
├── sdk/                     # Executor SDK
│   └── executor.ts          # Context envelope auto-packing
├── services/                # HTTP/SSE services
│   └── ask-answer.ts        # Ask/Answer API endpoints
└── utils/                   # Shared utilities
    ├── hash.ts              # Context hashing & verification
    └── logger.ts            # Structured logging

prompts/                     # Built-in role catalog
schemata/                    # JSON Schema definitions

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🤝 Contributing

Contributions are welcome! Please read our Contributing Guidelines before submitting PRs.

Development Workflow

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

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📄 License

MIT © 2025 Roy. See LICENSE for details.

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🙏 Acknowledgments

• Anthropic — For the Claude API and MCP specification
• Better-SQLite3 — High-performance SQLite bindings
• Zod — Type-safe schema validation

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📮 Support

• Issues: GitHub Issues
• Discussions: GitHub Discussions