Integrate WRT WebAssembly interpreter as MCP component host

[avrabe]

Summary

Create a reference host implementation using the WRT WebAssembly interpreter to run MCP server components, demonstrating secure, embedded execution of WASI-MCP components.

Background

WRT is a memory-safe, no_std compatible WebAssembly runtime with Component Model support, designed for embedded and safety-critical environments. Integrating WRT as an MCP component host will provide:

• Secure, sandboxed execution of MCP server components
• Embedded/constrained environment deployment capability
• Reference implementation for WASI-MCP proposal
• Alternative to larger runtimes like Wasmtime for specific use cases

Key WRT features relevant to MCP hosting:

• Full WebAssembly 1.0 specification implementation
• WebAssembly Component Model support
• no_std compatibility for embedded environments
• Memory-safe execution with ASIL-B compliance
• Stackless execution engine
• Control Flow Integrity protections

Implementation Tasks

Host Integration Layer

• Create pulseengine-mcp-wrt-host crate
• Implement WRT runtime initialization and configuration
• Add component loading and instantiation
• Create host function implementations for WASI-MCP interfaces

WASI-MCP Host Functions

• Implement host-side WASI-MCP interface providers
• Create resource management for component capabilities
• Add inter-component communication routing
• Implement host-provided services (storage, networking, etc.)

Component Lifecycle Management

• Component loading and validation
• Instance creation and destruction
• Resource cleanup and garbage collection
• Component health monitoring and crash recovery

Security & Sandboxing

• Implement capability-based security model
• Add resource access controls
• Create component isolation mechanisms
• Implement secure inter-component communication

Host Services Integration

• Bridge to native MCP transport implementations
• Provide host-side storage backends
• Implement host networking services
• Add logging and metrics collection

Configuration & Management

• Component configuration and deployment
• Runtime resource limits and quotas
• Performance monitoring and profiling
• Component update and hot-reload support

Example Integration

use pulseengine_mcp_wrt_host::*;
use wrt::{Module, ModuleInstance};

// Initialize WRT-based MCP host
let host = McpWrtHost::new(WrtConfig {
    memory_limit: 64 * 1024 * 1024, // 64MB
    execution_timeout: Duration::from_secs(30),
    allowed_imports: vec\!["wasi:mcp/*"],
})?;

// Load and instantiate MCP component
let component_bytes = std::fs::read("my_mcp_server.wasm")?;
let instance = host.load_component(component_bytes).await?;

// Execute MCP operations
let resources = instance.list_resources().await?;
let result = instance.call_tool("search", json\!({"query": "test"})).await?;

Integration Points

WASI-MCP Integration

• Interface with WASI-MCP component definitions (Implement WASI-MCP component model interfaces and reference implementation #30)
• Implement host-side async operation handling
• Bridge component calls to native MCP operations
• Provide resource handles and capability management

Framework Integration

• Integrate with main pulseengine-mcp-server framework
• Add component-based server deployment options
• Create unified configuration for WRT and native backends
• Implement graceful fallback to native execution

Development Tools

• Component debugging and profiling tools
• Development server with hot-reload
• Component testing framework
• Performance benchmarking utilities

Embedded & Constrained Environment Support

No-std Compatibility

• Ensure host implementation works in no_std environments
• Minimize memory allocation and usage
• Add heap-less operation modes
• Support for custom allocators

Resource Management

• Configurable memory limits per component
• CPU execution time limits and quotas
• I/O operation rate limiting
• Network bandwidth controls

Safety & Reliability

• Comprehensive error handling and recovery
• Component crash isolation
• Host stability protection
• Audit-quality logging and tracing

Performance Considerations

• Optimize component loading and instantiation
• Implement efficient inter-component communication
• Add JIT compilation support where available
• Create performance benchmarks vs other runtimes

Acceptance Criteria

• Successfully loads and executes WASI-MCP components
• Provides secure sandboxing and resource isolation
• Performs comparably to other WebAssembly runtimes
• Works in both standard and no_std environments
• Comprehensive test suite including embedded scenarios
• Documentation for deployment and configuration

Related Issues

• WASI-MCP Component Interfaces (Implement WASI-MCP component model interfaces and reference implementation #30)
• WASM32-WASIP2 Target Support (Add WASM32-WASIP2 target support for WebAssembly deployment #26)
• Component Model Examples (#TBD)

References

• WRT WebAssembly Runtime
• WebAssembly Component Model
• WASI Preview2/3 Specifications
• Embedded WebAssembly Best Practices