fix(orchestration): do not revive idle tasks from status-free progress (#7172)

Author: maslinedwin

apps/server/src/orchestration/ThreadBackgroundLiveness.test.ts

@@ -2,6 +2,32 @@ import { describe, expect, it } from "vite-plus/test";
 import * as ThreadBackgroundLiveness from "./ThreadBackgroundLiveness.ts";
 
 describe("ThreadBackgroundLiveness", () => {
+  it("does not let status-free progress restart an idle task", () => {
+    const liveness = ThreadBackgroundLiveness.make();
+    liveness.recordTaskLiveness({
+      threadId: "thread",
+      taskId: "task",
+      taskType: undefined,
+      status: undefined,
+      kind: "started",
+    });
+    liveness.recordTaskLiveness({
+      threadId: "thread",
+      taskId: "task",
+      taskType: undefined,
+      status: "idle",
+      kind: "updated",
+    });
+    liveness.recordTaskLiveness({
+      threadId: "thread",
+      taskId: "task",
+      taskType: undefined,
+      status: undefined,
+      kind: "progress",
+    });
+    expect(liveness.getThreadBackgroundLiveness("thread")).toBeNull();
+  });
+
   it("agents present as working; monitors as monitoring; agents win", () => {
     const liveness = ThreadBackgroundLiveness.make();
     const threadId = "t-live-1";

apps/server/src/orchestration/ThreadBackgroundLiveness.ts

@@ -130,6 +130,19 @@ export function make(): ThreadBackgroundLivenessService["Service"] {
         return;
       }
 
+      // Status-free progress is a description tick, not a restart. A delayed
+      // progress event after idle must not put the task back in the live set
+      // (#7128).
+      if (input.kind === "progress" && input.status === undefined) {
+        const existing = stateByThreadId.get(input.threadId);
+        const stillLive =
+          existing !== undefined &&
+          (existing.agents.has(input.taskId) || existing.monitors.has(input.taskId));
+        if (!stillLive) {
+          return;
+        }
+      }
+
       drop(input.threadId, input.taskId);
       const state = stateFor(input.threadId);
       const bucket =