Hermes.Client.Supervisor (hermes_mcp v0.10.1)

Supervisor for MCP client processes.

This module manages the lifecycle of both the MCP client and its associated transport process. It uses a :one_for_all strategy, meaning if either the client or transport crashes, both are restarted together to maintain consistency.

The supervisor automatically:

Starts the appropriate transport based on configuration
Starts the client with a reference to the transport
Ensures proper initialization order (transport first, then client)
Handles process naming for both client and transport

Process Naming

Client process: Uses the module name or custom :name option
Transport process: Named as Module.concat(ClientName, "Transport")

Transport Configuration

Supports all Hermes transport types:

:stdio - For command-line MCP servers
:sse - For Server-Sent Events transports
:websocket - For WebSocket connections
:streamable_http - For streaming HTTP transports

Summary

Types

transport_config()

Functions

child_spec(init_arg)

Returns a specification to start this module under a supervisor.

start_link(client_module, opts)

Starts the client supervisor.

Types

transport_config()

@type transport_config() ::
  {:stdio, keyword()}
  | {:sse, keyword()}
  | {:websocket, keyword()}
  | {:streamable_http, keyword()}

Functions

child_spec(init_arg)

Returns a specification to start this module under a supervisor.

See Supervisor.

start_link(client_module, opts)

@spec start_link(
  module(),
  keyword()
) :: Supervisor.on_start()

Starts the client supervisor.

Arguments

client_module - The client module using Hermes.Client
opts - Supervisor options including:
- :name - Optional custom name for the client process
- :transport - Transport configuration (required)
- :transport_name - Optional custom name for the transport process
- :client_info - Client identification info
- :capabilities - Client capabilities map
- :protocol_version - MCP protocol version

Examples

# Simple usage with module names
Hermes.Client.Supervisor.start_link(MyApp.MCPClient, 
  transport: {:stdio, command: "mcp", args: ["server"]},
  client_info: %{"name" => "MyApp", "version" => "1.0.0"},
  capabilities: %{"roots" => %{}},
  protocol_version: "2024-11-05"
)

# With custom names (e.g., for distributed systems)
Hermes.Client.Supervisor.start_link(MyApp.MCPClient,
  name: {:via, Horde.Registry, {MyCluster, "client_1"}},
  transport_name: {:via, Horde.Registry, {MyCluster, "transport_1"}},
  transport: {:stdio, command: "mcp", args: ["server"]},
  client_info: %{"name" => "MyApp", "version" => "1.0.0"},
  capabilities: %{"roots" => %{}},
  protocol_version: "2024-11-05"
)