pi-mono/packages/protocol

@earendil-works/pi-protocol

Runtime-neutral schemas, types, CBOR encoding, and byte-stream framing for the experimental Pi protocol.

Protocol version 3 adds the first plugin-service slice:

• a version handshake that identifies the logical serverId;
• explicit server and Session request targets;
• contract-agnostic service calls with optional keyed-instance identity;
• singleton and keyed-service subscription snapshots plus ordered state, spawn, and close updates;
• correlated responses, request cancellation, attachment-scoped events, and bounded protocol errors.

The transport carries { serviceId, instance?, member, args } calls. A server target contains { serverId }; a Session target contains { serverId, sessionId, attachmentId }. Keyed addresses contain a plugin key and provider-owned generation so delayed calls cannot reach a replacement instance. Service subscriptions return a complete member/state snapshot before update delivery starts. list() and create() return presentation-safe SessionSummary values containing no working directory, owner, storage, or parent metadata. The server derives private creation fields from authenticated workspace context. attach() creates or selects one presentation attachment and returns its Session and attachment IDs. prompt() targets that exact live attachment. The real Session and AgentHarness remain process-local. Disconnecting releases only that presentation's attachment after admitted work settles.

PromptArguments contains one serializable AgentLane.prompt() overload. PromptMessage is the protocol's closed set of built-in message DTOs; application-defined AgentMessage extensions are not accepted implicitly. RunResult is the wire-safe structural equivalent of the Harness result and contains no JavaScript Error instances.

The temporary ServiceRpc manifest still backs discovery, attachment, prompting, and transcript compatibility methods while those features migrate to plugin services. Session plugin calls outside that facade are routed opaquely to the attached worker, where the provider validates and invokes them.

A lane watch uses three RPCs so snapshot ordering does not depend on response/event scheduling: watch() creates a buffering watch and returns its authoritative snapshot, startWatch() flushes buffered events and begins live delivery, and stopWatch() releases it. Events carry their watch ID. Streaming message updates carry compact assistant-message frames rather than cumulative partial messages. Reconnection creates a new watch and snapshot rather than replaying old events.

Server and worker lifecycle is intentionally outside this public protocol. The experimental local coordinator is only an opaque message router; each replaceable server process owns the private lifecycle protocol.

Each wire frame consists of a four-byte unsigned big-endian payload length followed by one definite-length CBOR item. encodeClientMessage() and encodeServerMessage() validate and encode complete frames. ClientMessageDecoder and ServerMessageDecoder accept arbitrary stream fragmentation and coalescing.

import {
  PROTOCOL_VERSION,
  encodeClientMessage,
  ServerMessageDecoder,
  type ClientHello,
} from "@earendil-works/pi-protocol";

const hello: ClientHello = { type: "hello", version: PROTOCOL_VERSION };
transport.send(encodeClientMessage(hello));

const decoder = new ServerMessageDecoder({ maxFrameLength: 1024 * 1024 });
for (const message of decoder.push(incomingChunk)) handleServerMessage(message);
decoder.end();

All schemas reject unknown object properties. Schema violations, malformed CBOR, and invalid framing throw ProtocolValidationError. Transports authenticate peers before passing protocol bytes and must preserve byte order.

Default limits are 16 MiB per CBOR payload/frame, 1,000,000 array elements or map entries, and 64 nested item levels. The protocol is experimental and has no compatibility guarantees.