Crate brainos_mcphost 

Brain MCP Host

Host-side integration for external Model Context Protocol servers. The sibling brainos-mcp crate is a server (Brain exposes its own tools); this crate is the host side — Brain mounts and routes through other people’s tool servers.

Supported transports (per MCP spec 2025-11-25):

• stdio — child process speaking JSON-RPC on stdin/stdout
• Streamable HTTP — current spec transport
• HTTP+SSE — legacy transport, still spec-required for compatibility

This crate currently provides the trait surfaces (MCPHost, MCPClient), the ServerConfig / OAuthConfig / ToolDescriptor / CallOutcome types, the McpHostError taxonomy, and an InMemoryMcpHost no-transport stub so downstream wiring can be built against the trait before transports are implemented.

Re-exports

pub use aud_check::validate_token_aud;

pub use aud_check::AudCheckOutcome;

pub use capability_index::InMemoryToolCapabilityIndex;

pub use capability_index::ToolCapabilityIndex;

pub use error::McpHostError;

pub use oauth::manager_from_vault;

pub use oauth::VaultCredentialStore;

pub use resilient::ResilienceConfig;

pub use resilient::ResilientMcpHost;

pub use rmcp_host::RmcpHost;

pub use types::CallOutcome;

pub use types::MountedServer;

pub use types::OAuthConfig;

pub use types::ServerConfig;

pub use types::ServerInfo;

pub use types::ServerStatus;

pub use types::ToolDescriptor;

Modules

aud_check

OAuth access-token audience-claim (aud) validation.

capability_index

Per-host index of tools published by mounted MCP servers.

error

MCP host error taxonomy.

oauth

OAuth 2.1 + PKCE for HTTP MCP transports.

resilient

Resilience-layered MCPHost decorator.

rmcp_host

MCPHost implementation backed by the rmcp Rust SDK.

types

Public types for the MCP host: server configs, tool descriptors, and outcomes.

Structs

InMemoryMcpHost

In-memory MCPHost with no transport — records mounts so downstream wiring (Signal, Thalamus intents, tests) can be built against the trait before the real stdio / HTTP clients are wired in.

Constants

MCP_PROTOCOL_VERSION

MCP protocol version Brain negotiates against. Per spec 2025-11-25.

Traits

MCPClient

A single transport-bound MCP client (one per mounted server).

MCPHost

The host: manages the lifecycle of mounted servers and routes tool calls.

Functions

empty_env

Helper used by ServerConfig::Stdio to keep env maps deterministic.

stdio_cfg

Helper for callers building stdio configs from path+args.