pi-mono/packages/server

@earendil-works/pi-server

Experimental local server for the new durable Session and Agent Harness interfaces.

The current slice supports server- and Session-scoped plugin-service routing, multi-presentation attachment, prompting, and optional main-lane observation. RoutedServerServiceHost.attachClient() creates one connection-scoped server service endpoint with narrow attachment-management capabilities. RoutedSessionHandle.attachClient() returns a presentation-scoped Session capability. Its optional invokeService() forwards an opaque service/member envelope to the selected Session endpoint; the server validates the attachment route but does not load the plugin contract. Its optional watch() supplies an authoritative snapshot plus buffered events.

• server service calls and subscriptions route opaquely through the connection's RoutedServerServiceAttachment;
• the application-owned SessionDirectory projects the private catalog into replicated presentation-safe state;
• the application-owned SessionManagement creates, removes, attaches, and detaches Sessions without exposing route IDs in business results;
• attachment changes are published out of band after the router installs or clears the live route;
• the compatibility list, create, and attach operations remain available to low-level clients during migration;
• prompt executes one serializable prompt through the requesting presentation's attachment capability.
• unknown Session service calls route through invokeService without server-side business-payload decoding;
• service subscription updates remain scoped to the requesting attachment;
• watch, startWatch, and stopWatch provide snapshot-first lane observation when supported by the host.

A Session may have multiple presentation attachments. Repeating attach from one connection is idempotent; every successful attachment has a server-generated attachmentId delivered only as routing control data. Session requests carry { serverId, sessionId, attachmentId }, and the server rejects stale or mismatched routes. Losing a connection rejects its local responses but releases its attachment only after admitted prompts settle. The host decides when zero presentation demand and worker-local Harness activity permit worker retirement. Server shutdown closes every routed Session handle, releasing its worker and Session writer ownership.

import { randomUUID } from "node:crypto";
import { MemorySessionRepo, type Session } from "@earendil-works/pi-agent-core";
import {
  type RoutedSessionHandle,
  type ServerHost,
} from "@earendil-works/pi-server";
import { createUnixServer, getUnixSocketPath } from "@earendil-works/pi-server/unix";

async function startServer(
  openRoutedSession: (session: Session) => Promise<RoutedSessionHandle>,
) {
  const sessions = new MemorySessionRepo();
  const host: ServerHost = {
    sessions: {
      list: () => sessions.list(),
      async create({ id }) {
        const session = await sessions.create({ id });
        try {
          return session.metadata;
        } finally {
          await session.close();
        }
      },
    },
    async openSession(metadata) {
      const session = await sessions.open(metadata);
      try {
        return await openRoutedSession(session);
      } catch (error) {
        try {
          await session.close();
        } catch (cleanupError) {
          throw new AggregateError(
            [error, cleanupError],
            "Harness creation and Session cleanup failed",
          );
        }
        throw error;
      }
    },
  };

  const serverId = randomUUID();
  const server = createUnixServer(host, {
    serverId,
    path: getUnixSocketPath(serverId, "/run/user/1000/pi"),
  });
  await server.start();
  return server;
}

Applications supply a private Session catalog and a routed Session factory. The server projects catalog records to summaries before transport; the host receives the repository's concrete metadata and owns acquiring the worker-local Session and Harness. Failures are cleaned up in that worker. Neither an open JavaScript Session nor a Harness crosses the process boundary.

serverId is a logical identity supplied by the launcher, not a socket address. The Unix preset requires an explicit physical path; getUnixSocketPath() derives one from a caller-selected directory. Choose a short, private runtime directory rather than deriving the route from an unbounded home-directory path. A long-lived launcher can reuse the same ID and path when replacing a server process.

Server composes authenticated transports through ServerListener. The Unix submodule provides createUnixListener() and createUnixServer(). Low-level CBOR framing and validation come from @earendil-works/pi-protocol.

Server and worker lifecycle is managed outside the public Pi protocol. The replaceable application server converts connection attachments into private demand updates; the worker combines generation-tagged demand with authoritative Harness activity. The experimental coordinator only supplies stable routing and reports generic server-generation connection changes.