fix(server): bound stale websocket connections

Track application ownership per physical socket and terminate abandoned or backpressured transports without disrupting replacement connections.

packages/protocol/src/client-capabilities.ts

@@ -21,6 +21,7 @@ export const CLIENT_CAPS = {
   // COMPAT(projectUpdates): added in v0.1.109, remove gate after 2027-01-15.
   projectUpdates: "project_updates",
   browserHost: "browser_host",
+  applicationSocketLease: "application_socket_lease",
 } as const;
 
 export type ClientCapability = (typeof CLIENT_CAPS)[keyof typeof CLIENT_CAPS];

packages/protocol/src/messages.application-socket-lease.test.ts

@@ -0,0 +1,25 @@
+import { expect, test } from "vitest";
+import { CLIENT_CAPS } from "./client-capabilities.js";
+import { WSHelloMessageSchema } from "./messages.js";
+
+const legacyHello = {
+  type: "hello" as const,
+  clientId: "client-1",
+  clientType: "browser" as const,
+  protocolVersion: 1,
+};
+
+test("hello accepts the application socket lease capability", () => {
+  const hello = WSHelloMessageSchema.parse({
+    ...legacyHello,
+    capabilities: { [CLIENT_CAPS.applicationSocketLease]: true },
+  });
+
+  expect(hello.capabilities?.[CLIENT_CAPS.applicationSocketLease]).toBe(true);
+});
+
+test("hello remains compatible when the application socket lease capability is absent", () => {
+  const hello = WSHelloMessageSchema.parse(legacyHello);
+
+  expect(hello.capabilities).toBeUndefined();
+});

packages/protocol/src/messages.ts

@@ -5565,6 +5565,7 @@ export const WSHelloMessageSchema = z.object({
       [CLIENT_CAPS.providerSubagents]: z.boolean().optional(),
       [CLIENT_CAPS.projectUpdates]: z.boolean().optional(),
       [CLIENT_CAPS.browserHost]: BrowserAutomationHostCapabilitySchema.optional(),
+      [CLIENT_CAPS.applicationSocketLease]: z.boolean().optional(),
     })
     .passthrough()
     .optional(),