hyperhive/hive-subagent-mcp/src/mcp.rs

//! The MCP tool surface: `start` / `continue` / `interrupt`, served
//! directly over streamable-http — no stdio bridge, no round-trip socket.

use std::sync::Arc;

use rmcp::{
    ServerHandler,
    handler::server::wrapper::Parameters,
    schemars::{self, JsonSchema},
    tool, tool_handler, tool_router,
};
use serde::Deserialize;

use crate::session::{self, State};

#[derive(Debug, Deserialize, JsonSchema)]
struct StartArgs {
    /// Session name — becomes both this daemon's tracking key and claude's
    /// own `--name`/`--resume` session title. Same identifier rules as the
    /// `bash` server's task names: lowercase, digits, hyphen, max 63 chars.
    /// Reusable once a prior *finished* session under that name is done —
    /// rejected while one under the same name is still running.
    name: String,
    /// `--model` for the subagent's own claude invocation. Omit for
    /// claude's own default. The `base:claude-subagents` skill's
    /// "cheaper-than-you" guidance still applies here.
    #[serde(default)]
    model: Option<String>,
    /// Path to a file passed as `--append-system-prompt-file` — the
    /// subagent's actual task instructions. A file, not an inline string,
    /// to avoid `ARG_MAX` on a large recipe.
    prompt_file: String,
    /// Written to the subagent's stdin as its first turn's prompt. Default:
    /// a generic "carry out your instructions" nudge — the real task detail
    /// belongs in `prompt_file`, not here.
    #[serde(default = "default_trigger")]
    trigger: String,
}

fn default_trigger() -> String {
    "Carry out the task described in your instructions.".to_owned()
}

#[derive(Debug, Deserialize, JsonSchema)]
struct ContinueArgs {
    /// The existing session's name (from a prior `start`).
    name: String,
    /// The new turn's prompt, written to the subagent's stdin.
    prompt: String,
    /// `--model` for this turn. Omit to let claude fall back to its own
    /// default — this does not have to match whatever model `start` used.
    #[serde(default)]
    model: Option<String>,
}

#[derive(Debug, Deserialize, JsonSchema)]
struct InterruptArgs {
    /// The running session's name to signal.
    name: String,
    /// `true` sends SIGKILL immediately; `false` (default) sends SIGINT,
    /// letting claude shut down cleanly if it's already mid-response.
    #[serde(default)]
    force: bool,
}

#[derive(Clone)]
struct SubagentMcp {
    state: Arc<State>,
}

#[tool_router]
impl SubagentMcp {
    #[tool(
        description = "Start a fresh claude subagent session under `name`, running in the \
            background. Returns as soon as the process is confirmed running — not once it \
            finishes; poll for completion via the todo this daemon pushes when the turn ends, \
            or use `continue` later to give it another turn. A prior *finished* session under \
            the same name is archived first (real fresh start, not a silent resume); a \
            *currently running* one is refused. Always runs with \
            `--dangerously-skip-permissions --strict-mcp-config` (no `--mcp-config` override — \
            that's a safety property, not a knob). See the `base:claude-subagents` skill for \
            when to reach for this."
    )]
    fn start(&self, Parameters(args): Parameters<StartArgs>) -> String {
        match session::start(
            &self.state,
            &args.name,
            args.model,
            &args.prompt_file,
            args.trigger,
        ) {
            Ok(msg) => msg,
            Err(e) => format!("start error: {e:#}"),
        }
    }

    #[tool(
        name = "continue",
        description = "Give an existing named subagent session a new turn — whether that's \
            because its previous turn finished and you have a follow-up instruction, or you're \
            reattaching after this daemon restarted (the session itself survives independently \
            of the daemon that spawned it). Returns as soon as confirmed running, same as \
            `start`. Refuses a name with no session on disk at all, or one already running."
    )]
    fn r#continue(&self, Parameters(args): Parameters<ContinueArgs>) -> String {
        match session::continue_(&self.state, &args.name, args.prompt, args.model) {
            Ok(msg) => msg,
            Err(e) => format!("continue error: {e:#}"),
        }
    }

    #[tool(
        description = "Signal a currently-running subagent session to stop. Only works while \
            it's actually running — there's no queued/pending state to cancel pre-emptively, \
            only running or not tracked at all. `force: true` for SIGKILL, otherwise SIGINT."
    )]
    fn interrupt(&self, Parameters(args): Parameters<InterruptArgs>) -> String {
        match session::interrupt(&self.state, &args.name, args.force) {
            Ok(msg) => msg,
            Err(e) => format!("interrupt error: {e:#}"),
        }
    }
}

#[tool_handler]
impl ServerHandler for SubagentMcp {}

/// Run the MCP server over HTTP (rmcp streamable-http transport) on `addr`.
/// Loopback-only bind, one long-lived session — same shape as the bash and
/// matrix daemons' own `serve_http`.
///
/// # Errors
///
/// Returns an error if the listener cannot bind `addr` or the HTTP server
/// exits with a fatal error.
pub async fn serve_http(addr: std::net::SocketAddr, state: Arc<State>) -> anyhow::Result<()> {
    use rmcp::transport::streamable_http_server::{
        StreamableHttpServerConfig, StreamableHttpService, session::local::LocalSessionManager,
    };
    let mut session_manager = LocalSessionManager::default();
    // A subagent turn can run considerably longer than a bash command —
    // same 24h keep-alive rationale as the bash/matrix daemons.
    session_manager.session_config.keep_alive = Some(std::time::Duration::from_hours(24));
    let session_manager = std::sync::Arc::new(session_manager);
    let service = StreamableHttpService::new(
        move || {
            Ok(SubagentMcp {
                state: Arc::clone(&state),
            })
        },
        session_manager,
        StreamableHttpServerConfig::default(),
    );
    let app = axum::Router::new().nest_service("/mcp", service);
    let listener = tokio::net::TcpListener::bind(addr).await?;
    tracing::info!(%addr, "serving hive-subagent MCP over streamable-http at /mcp");
    axum::serve(listener, app).await?;
    Ok(())
}