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🚀 PMCP v1.5.0: Write Once, Deploy Everywhere - WASM/WASI Universal MCP Servers

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@guyernest guyernest released this 25 Sep 01:37
· 697 commits to main since this release
v1.5.0
6be87f3

🚀 PMCP v1.5.0: Write Once, Deploy Everywhere - WASM/WASI Universal MCP Servers

🎯 Major Release: Platform-Agnostic MCP Architecture

✨ Headline Feature: Universal WASM Deployment

Write once in Rust, deploy everywhere - The same MCP server code now runs on Cloudflare Workers, Fermyon Spin, and any WASM/WASI-compliant platform, achieving true platform independence similar to the TypeScript SDK architecture.

🏗️ Architecture Revolution: Clean Separation of Logic and Transport

📐 New Architecture Design

Following the TypeScript SDK's successful pattern, v1.5.0 introduces a clean separation between:

  • Core MCP Logic: Platform-agnostic business logic (WasmMcpServer)
  • Transport Layer: Thin platform-specific adapters (Cloudflare, Fermyon, etc.)
  • Universal API: Consistent interface across all deployment targets

🎯 Key Achievement

// Same code runs everywhere
let server = WasmMcpServer::builder()
    .name("my-mcp-server")
    .version("1.0.0")
    .tool("calculator", SimpleTool::new(...))
    .build();

// Deploy to Cloudflare, Fermyon, or any WASM platform

🌟 Major New Features

🔧 WasmMcpServer - Universal MCP Implementation

  • Platform-agnostic core: Single implementation for all WASM targets
  • Type-safe builder pattern: Compile-time validation of server configuration
  • SimpleTool abstraction: Easy tool creation with automatic JSON-RPC handling
  • Full MCP protocol compliance: Initialize, tools/list, tools/call, notifications
  • Automatic error handling: Built-in validation and error responses

🌐 Multi-Platform Deployment Support

Cloudflare Workers

  • Global edge deployment: 200+ locations worldwide
  • V8 Isolates: Sub-millisecond cold starts
  • KV & Durable Objects: Integrated state management
  • Cost-effective: Pay-per-request pricing model

Fermyon Spin

  • Standard WASI: Uses wasm32-wasip1 target
  • Component Model: First-class WASI component support
  • Built-in SQLite: Persistent storage capabilities
  • Simple deployment: Single spin deploy command

🧪 Enhanced Testing Infrastructure

MCP Tester Improvements

  • Scenario-based testing: YAML/JSON test definitions
  • Comprehensive assertions: Success, failure, contains, equals, array operations
  • Verbose mode support: Detailed test output with --verbose flag
  • HTTP/JSON-RPC alignment: Full protocol compliance testing

Test Scenarios

  • calculator-test.yaml: Comprehensive test suite with error cases
  • calculator-simple.json: Basic operation validation
  • minimal-test.json: Quick connectivity verification

🔄 Transport Layer Improvements

  • JSON-RPC notification handling: Proper detection of requests without 'id' field
  • Empty response support: Handle 200 OK with no Content-Type (notifications)
  • Platform-specific adapters: Minimal boilerplate for each platform
  • Error propagation: Consistent error handling across transports

📊 Performance & Scalability

🚀 Deployment Metrics

Platform Cold Start Global Scale State Management Cost Model
Cloudflare 50-200ms 200+ locations KV, Durable Objects Pay-per-request
Fermyon 100-300ms Regional SQLite Instance-based
WASI Generic Varies Custom Platform-specific Flexible

⚡ Runtime Performance

  • Zero overhead abstraction: No performance penalty for platform abstraction
  • Compile-time optimization: WASM optimization at build time
  • Minimal binary size: ~500KB WASM modules
  • Memory efficient: Low memory footprint per request

🛠️ Developer Experience Improvements

📦 Simplified Development

# Build once
cargo build --target wasm32-unknown-unknown --release

# Deploy anywhere
wrangler deploy  # Cloudflare
spin deploy      # Fermyon
# ... any WASM platform

🔍 Testing Tools

# Test any deployment with scenarios
mcp-tester scenario https://<your-deployment> test-scenarios/calculator-test.yaml

# Verbose output for debugging
mcp-tester tools --verbose https://<your-deployment>

📚 Comprehensive Documentation

  • Platform-specific deployment guides
  • Scenario testing documentation
  • Architecture overview with examples
  • Migration guides from v1.4.x

🔧 Technical Improvements

Core SDK

  • ServerCore refactoring: Clean separation of concerns
  • Protocol version negotiation: Improved compatibility handling
  • Type safety enhancements: Stronger compile-time guarantees
  • Error recovery: Better error messages and recovery strategies

Quality & Testing

  • 100% scenario test pass rate: All test scenarios passing
  • Cross-platform validation: Tested on multiple WASM runtimes
  • Backward compatibility: Full compatibility with existing MCP clients
  • Toyota Way compliance: Zero tolerance for defects

🚀 Migration Guide

From v1.4.x to v1.5.0

  1. Update dependency: pmcp = "1.5.0"
  2. Choose deployment model:
    • Use WasmMcpServer for WASM deployments
    • Use existing Server for native deployments
  3. Platform adapters: Add thin wrapper for your platform
  4. Test with scenarios: Validate using mcp-tester

Example Migration

// Before (v1.4.x)
let server = Server::builder()
    .tool(my_tool_handler)
    .build();

// After (v1.5.0) - WASM deployment
let server = WasmMcpServer::builder()
    .tool("my_tool", SimpleTool::new(my_tool_handler))
    .build();

📈 What's Next

Roadmap

  • Additional platform support (Wasmtime, WasmEdge, etc.)
  • State management abstractions
  • Cross-platform resource handlers
  • Enhanced debugging tools

🙏 Acknowledgments

Special thanks to all contributors who made this release possible, especially the work on clean architecture separation and comprehensive testing infrastructure.

📦 Installation

[dependencies]
pmcp = "1.5.0"

🔗 Resources

Breaking Changes: None - Full backward compatibility maintained

Minimum Rust Version: 1.70.0

License: MIT

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