Struct HostParts 

pub struct HostParts {
    pub config: Config,
    pub providers: ProviderRegistry,
    pub runs_dir: PathBuf,
    pub shared_mcp: Arc<Mutex<ToolExecutor>>,
    pub mcp_tool_defs: Vec<Tool>,
    pub mcp_pool: Arc<McpPool>,
    pub runtime: Handle,
    pub now_secs: fn() -> i64,
}

Everything the daemon hands its world host at construction.

A struct rather than eight positional parameters because these are not arguments in the usual sense: each is a resource the host owns for the rest of the process’s life, assembled once at boot and never varied. Naming them here describes the daemon; listing them at the call site described nothing.

Fields

config: Config

The resolved configuration this daemon booted with.

providers: ProviderRegistry

Providers built from that config, keyed by name.

runs_dir: PathBuf

Where run state is persisted.

shared_mcp: Arc<Mutex<ToolExecutor>>

MCP connections shared across every agent.

mcp_tool_defs: Vec<Tool>

The tools those servers advertise.

mcp_pool: Arc<McpPool>

The pool that keeps per-agent MCP servers warm.

runtime: Handle

The tokio runtime the async lanes run on.

now_secs: fn() -> i64

The clock, injected so a test does not depend on the wall clock.