From 40c71bd0d8c6803456a81ca4225f34c1706ecf0f Mon Sep 17 00:00:00 2001
From: Gustavo Madeira Santana <gumadeiras@gmail.com>
Date: Sun, 19 Apr 2026 17:52:56 -0400
Subject: [PATCH] fix: stabilize subagent outcome timing equality

---
 .../subagent-registry-completion.test.ts      |  8 ++++-
 src/agents/subagent-registry-completion.ts    | 11 ++++++
 .../subagent-registry-lifecycle.test.ts       | 34 ++++++++++++++++---
 src/agents/subagent-registry-lifecycle.ts     |  7 ++--
 src/agents/subagent-registry.test.ts          |  7 +++-
 5 files changed, 58 insertions(+), 9 deletions(-)

diff --git a/src/agents/subagent-registry-completion.test.ts b/src/agents/subagent-registry-completion.test.ts
index 3c4d01ed9a9..54685caf88f 100644
--- a/src/agents/subagent-registry-completion.test.ts
+++ b/src/agents/subagent-registry-completion.test.ts
@@ -49,7 +49,7 @@ describe("emitSubagentEndedHookOnce", () => {
     lifecycleMocks.runSubagentEnded.mockClear();
   });
 
-  it("treats timing differences as different run outcomes", () => {
+  it("treats timing differences as different only after both outcomes have timing", () => {
     expect(
       mod.runOutcomesEqual(
         { status: "timeout", startedAt: 1_000, endedAt: 2_000, elapsedMs: 1_000 },
@@ -62,6 +62,12 @@ describe("emitSubagentEndedHookOnce", () => {
         { status: "error", error: "boom", startedAt: 1_000, endedAt: 2_000, elapsedMs: 1_000 },
       ),
     ).toBe(true);
+    expect(
+      mod.runOutcomesEqual(
+        { status: "ok", startedAt: 1_000, endedAt: 2_000, elapsedMs: 1_000 },
+        { status: "ok" },
+      ),
+    ).toBe(true);
   });
 
   it("records ended hook marker even when no subagent_ended hooks are registered", async () => {
diff --git a/src/agents/subagent-registry-completion.ts b/src/agents/subagent-registry-completion.ts
index e78bda27b1f..3c887e93bab 100644
--- a/src/agents/subagent-registry-completion.ts
+++ b/src/agents/subagent-registry-completion.ts
@@ -28,9 +28,20 @@ export function runOutcomesEqual(
       return false;
     }
   }
+  if (!runOutcomeHasTiming(a) || !runOutcomeHasTiming(b)) {
+    return true;
+  }
   return a.startedAt === b.startedAt && a.endedAt === b.endedAt && a.elapsedMs === b.elapsedMs;
 }
 
+export function runOutcomeHasTiming(outcome: SubagentRunOutcome | undefined): boolean {
+  return (
+    Number.isFinite(outcome?.startedAt) ||
+    Number.isFinite(outcome?.endedAt) ||
+    Number.isFinite(outcome?.elapsedMs)
+  );
+}
+
 export function resolveLifecycleOutcomeFromRunOutcome(
   outcome: SubagentRunOutcome | undefined,
 ): SubagentLifecycleEndedOutcome {
diff --git a/src/agents/subagent-registry-lifecycle.test.ts b/src/agents/subagent-registry-lifecycle.test.ts
index d1abc3eb5c1..617ab6e7de6 100644
--- a/src/agents/subagent-registry-lifecycle.test.ts
+++ b/src/agents/subagent-registry-lifecycle.test.ts
@@ -62,11 +62,6 @@ vi.mock("./subagent-registry-cleanup.js", () => ({
   resolveDeferredCleanupDecision: () => ({ kind: "give-up", reason: "retry-limit" }),
 }));
 
-vi.mock("./subagent-registry-completion.js", () => ({
-  runOutcomesEqual: (left: unknown, right: unknown) =>
-    JSON.stringify(left) === JSON.stringify(right),
-}));
-
 vi.mock("./subagent-registry-helpers.js", () => ({
   ANNOUNCE_COMPLETION_HARD_EXPIRY_MS: 30 * 60_000,
   ANNOUNCE_EXPIRY_MS: 5 * 60_000,
@@ -280,6 +275,35 @@ describe("subagent registry lifecycle hardening", () => {
     expect(persist).toHaveBeenCalled();
   });
 
+  it("persists timing when a preexisting outcome matches without timing", async () => {
+    const persist = vi.fn();
+    const entry = createRunEntry({
+      startedAt: 2_000,
+      outcome: { status: "ok" },
+      expectsCompletionMessage: false,
+    });
+
+    const controller = createLifecycleController({ entry, persist });
+
+    await expect(
+      controller.completeSubagentRun({
+        runId: entry.runId,
+        endedAt: 4_250,
+        outcome: { status: "ok" },
+        reason: SUBAGENT_ENDED_REASON_COMPLETE,
+        triggerCleanup: false,
+      }),
+    ).resolves.toBeUndefined();
+
+    expect(entry.outcome).toEqual({
+      status: "ok",
+      startedAt: 2_000,
+      endedAt: 4_250,
+      elapsedMs: 2_250,
+    });
+    expect(persist).toHaveBeenCalled();
+  });
+
   it("does not wait for a completion reply when the run does not expect one", async () => {
     const entry = createRunEntry({
       expectsCompletionMessage: false,
diff --git a/src/agents/subagent-registry-lifecycle.ts b/src/agents/subagent-registry-lifecycle.ts
index c278d62a86d..2caa54831c7 100644
--- a/src/agents/subagent-registry-lifecycle.ts
+++ b/src/agents/subagent-registry-lifecycle.ts
@@ -23,7 +23,7 @@ import {
   resolveCleanupCompletionReason,
   resolveDeferredCleanupDecision,
 } from "./subagent-registry-cleanup.js";
-import { runOutcomesEqual } from "./subagent-registry-completion.js";
+import { runOutcomeHasTiming, runOutcomesEqual } from "./subagent-registry-completion.js";
 import {
   ANNOUNCE_COMPLETION_HARD_EXPIRY_MS,
   ANNOUNCE_EXPIRY_MS,
@@ -594,7 +594,10 @@ export function createSubagentRegistryLifecycleController(params: {
       startedAt: entry.startedAt,
       endedAt,
     });
-    if (!runOutcomesEqual(entry.outcome, outcome)) {
+    const shouldPersistOutcome =
+      !runOutcomesEqual(entry.outcome, outcome) ||
+      (!runOutcomeHasTiming(entry.outcome) && runOutcomeHasTiming(outcome));
+    if (shouldPersistOutcome) {
       entry.outcome = outcome;
       mutated = true;
     }
diff --git a/src/agents/subagent-registry.test.ts b/src/agents/subagent-registry.test.ts
index 2c8b2de16f0..8c872cd3b2b 100644
--- a/src/agents/subagent-registry.test.ts
+++ b/src/agents/subagent-registry.test.ts
@@ -191,7 +191,12 @@ describe("subagent registry seam flow", () => {
         task: "finish the task",
         cleanup: "delete",
         roundOneReply: "final completion reply",
-        outcome: { status: "ok" },
+        outcome: {
+          status: "ok",
+          startedAt: 111,
+          endedAt: 222,
+          elapsedMs: 111,
+        },
       }),
     );