feat: Add message sequencing and acknowledgment to remote messaging

Implements message acknowledgment and retransmission:

- Update RemoteCommand type to include seq (sequence number) and ack (piggybacked ACK) fields
- Add per-peer sequence tracking that persists across reconnections
- Implement data structures with cumulative ACK support
- Implement transmission timeout with limited retries
- Reject pending promises when giving up on reconnection

Author: FUDCo

packages/kernel-test/src/remote-comms.test.ts

@@ -11,6 +11,7 @@ import type {
   PlatformServices,
   RemoteMessageHandler,
   RemoteCommsOptions,
+  RemoteMessageBase,
 } from '@metamask/ocap-kernel';
 import { NodejsPlatformServices } from '@ocap/nodejs';
 import { describe, it, expect, beforeEach } from 'vitest';
@@ -77,11 +78,13 @@ class DirectNetworkService {
         return Promise.resolve();
       },
 
-      async sendRemoteMessage(to: string, message: string) {
+      async sendRemoteMessage(to: string, messageBase: RemoteMessageBase) {
         const fromPeer = actualPeerId ?? tempPeerId;
         // Route message directly to the target peer's handler
         const targetHandler = self.peerRegistry.get(to);
         if (targetHandler) {
+          // Stringify the message object for transmission
+          const message = JSON.stringify(messageBase);
           const response = await targetHandler(fromPeer, message);
           // If there's a response, send it back
           if (response) {
@@ -95,6 +98,15 @@ class DirectNetworkService {
         }
       },
 
+      async handleAck(_peerId: string, _ackSeq: number) {
+        // Mock implementation - direct network doesn't need ACK handling
+        return Promise.resolve();
+      },
+
+      updateReceivedSeq(_peerId: string, _seq: number) {
+        // Mock implementation - direct network doesn't need sequence tracking
+      },
+
       async initializeRemoteComms(
         keySeed: string,
         _options: RemoteCommsOptions,

packages/ocap-kernel/src/Kernel.test.ts

@@ -1017,10 +1017,11 @@ describe('Kernel', () => {
           mockKernelDatabase,
         );
         const remoteManagerInstance = mocks.RemoteManager.lastInstance;
-        await kernel.sendRemoteMessage('peer-123', 'hello');
+        const messageBase = { method: 'deliver' as const, params: ['hello'] };
+        await kernel.sendRemoteMessage('peer-123', messageBase);
         expect(remoteManagerInstance.sendRemoteMessage).toHaveBeenCalledWith(
           'peer-123',
-          'hello',
+          messageBase,
         );
       });
     });

packages/ocap-kernel/src/Kernel.ts

@@ -13,6 +13,7 @@ import { KernelRouter } from './KernelRouter.ts';
 import { KernelServiceManager } from './KernelServiceManager.ts';
 import type { KernelService } from './KernelServiceManager.ts';
 import { OcapURLManager } from './remotes/OcapURLManager.ts';
+import type { RemoteMessageBase } from './remotes/RemoteHandle.ts';
 import { RemoteManager } from './remotes/RemoteManager.ts';
 import type { RemoteCommsOptions } from './remotes/types.ts';
 import { kernelHandlers } from './rpc/index.ts';
@@ -261,11 +262,14 @@ export class Kernel {
    * Send a message to a remote kernel.
    *
    * @param to - The peer ID of the remote kernel.
-   * @param message - The message to send.
+   * @param messageBase - The message to send (without seq/ack).
    * @returns a promise for the result of the message send.
    */
-  async sendRemoteMessage(to: string, message: string): Promise<void> {
-    await this.#remoteManager.sendRemoteMessage(to, message);
+  async sendRemoteMessage(
+    to: string,
+    messageBase: RemoteMessageBase,
+  ): Promise<void> {
+    await this.#remoteManager.sendRemoteMessage(to, messageBase);
   }
 
   /**

packages/ocap-kernel/src/index.ts

@@ -19,6 +19,7 @@ export type {
   StopRemoteComms,
   RemoteCommsOptions,
 } from './remotes/types.ts';
+export type { RemoteMessageBase } from './remotes/RemoteHandle.ts';
 export {
   isVatId,
   VatIdStruct,