fix: ignore stale rows in subagent activity checks

src/agents/subagent-registry.steer-restart.test.ts

@@ -564,6 +564,35 @@ describe("subagent registry steer restarts", () => {
     );
   });
 
+  it("treats a child session as inactive when only a stale older row is still unended", async () => {
+    const childSessionKey = "agent:main:subagent:stale-active-older-row";
+
+    mod.addSubagentRunForTests({
+      runId: "run-stale-older",
+      childSessionKey,
+      requesterSessionKey: MAIN_REQUESTER_SESSION_KEY,
+      requesterDisplayKey: MAIN_REQUESTER_DISPLAY_KEY,
+      task: "older stale row",
+      startedAt: 100,
+      createdAt: 100,
+      cleanup: "keep",
+    });
+    mod.addSubagentRunForTests({
+      runId: "run-current-ended",
+      childSessionKey,
+      requesterSessionKey: MAIN_REQUESTER_SESSION_KEY,
+      requesterDisplayKey: MAIN_REQUESTER_DISPLAY_KEY,
+      task: "current ended row",
+      startedAt: 200,
+      createdAt: 200,
+      endedAt: 250,
+      outcome: { status: "ok" },
+      cleanup: "keep",
+    });
+
+    expect(mod.isSubagentSessionRunActive(childSessionKey)).toBe(false);
+  });
+
   it("recovers announce cleanup when completion arrives after a kill marker", async () => {
     const childSessionKey = "agent:main:subagent:kill-race";
     registerRun({

src/agents/subagent-registry.ts

@@ -1596,16 +1596,17 @@ export function resolveRequesterForChildSession(childSessionKey: string): {
 
 export function isSubagentSessionRunActive(childSessionKey: string): boolean {
   const runIds = findRunIdsByChildSessionKey(childSessionKey);
+  let latest: SubagentRunRecord | undefined;
   for (const runId of runIds) {
     const entry = subagentRuns.get(runId);
     if (!entry) {
       continue;
     }
-    if (typeof entry.endedAt !== "number") {
-      return true;
+    if (!latest || entry.createdAt > latest.createdAt) {
+      latest = entry;
     }
   }
-  return false;
+  return Boolean(latest && typeof latest.endedAt !== "number");
 }
 
 export function shouldIgnorePostCompletionAnnounceForSession(childSessionKey: string): boolean {