diff --git a/src/lib/boss-projections.ts b/src/lib/boss-projections.ts
index c90b1d4..2533063 100644
--- a/src/lib/boss-projections.ts
+++ b/src/lib/boss-projections.ts
@@ -355,6 +355,7 @@ function buildConversationItem(state: BossState, project: Project): Conversation
   const folderLabel = project.threadMeta?.folderName ?? "";
   const activityIconCount = deriveConversationActivityIconCount(state, project);
   const topPinnedLabel = isTopPinnedConversation(project) ? "置顶" : undefined;
+  const latestConversationActivityAt = deriveLatestConversationActivityAt(project);
   const groupMembers = project.isGroup
     ? project.groupMembers.map((member) => ({
         threadId: member.threadId,
@@ -379,8 +380,8 @@ function buildConversationItem(state: BossState, project: Project): Conversation
     activityIconCount,
     topPinnedLabel,
     manualPinned: Boolean(project.pinned && !project.systemPinned),
-    latestReplyAt: project.lastMessageAt,
-    latestReplyLabel: formatTimestampLabel(project.lastMessageAt),
+    latestReplyAt: latestConversationActivityAt,
+    latestReplyLabel: formatTimestampLabel(latestConversationActivityAt),
     unreadCount: project.unreadCount,
     riskLevel: project.riskLevel,
     activeDeviceCount: devices.length,
@@ -403,6 +404,31 @@ function buildConversationItem(state: BossState, project: Project): Conversation
   } satisfies ConversationItem;
 }
 
+function deriveLatestConversationActivityAt(project: Project) {
+  const candidates = [
+    project.lastMessageAt,
+    project.threadMeta?.lastObservedCodexActivityAt,
+    project.projectUnderstanding?.updatedAt,
+    project.updatedAt,
+  ].filter(Boolean) as string[];
+
+  let latest = candidates[0];
+  let latestTs = latest ? Date.parse(latest) : Number.NEGATIVE_INFINITY;
+
+  for (const candidate of candidates.slice(1)) {
+    const candidateTs = Date.parse(candidate);
+    if (!Number.isFinite(candidateTs)) {
+      continue;
+    }
+    if (!Number.isFinite(latestTs) || candidateTs > latestTs) {
+      latest = candidate;
+      latestTs = candidateTs;
+    }
+  }
+
+  return latest ?? project.lastMessageAt;
+}
+
 function deriveConversationActivityIconCount(state: BossState, project: Project): number {
   let count = 0;
 
diff --git a/tests/conversation-home-items.test.ts b/tests/conversation-home-items.test.ts
index 82db352..3865ea7 100644
--- a/tests/conversation-home-items.test.ts
+++ b/tests/conversation-home-items.test.ts
@@ -8,6 +8,7 @@ let runtimeRoot = "";
 let readState: (typeof import("../src/lib/boss-data"))["readState"];
 let getConversationHomeItems: (typeof import("../src/lib/boss-projections"))["getConversationHomeItems"];
 let getConversationFolderView: (typeof import("../src/lib/boss-projections"))["getConversationFolderView"];
+let formatTimestampLabel: (typeof import("../src/lib/boss-projections"))["formatTimestampLabel"];
 
 async function setup() {
   if (runtimeRoot) return;
@@ -22,6 +23,7 @@ async function setup() {
   readState = data.readState;
   getConversationHomeItems = projections.getConversationHomeItems;
   getConversationFolderView = projections.getConversationFolderView;
+  formatTimestampLabel = projections.formatTimestampLabel;
 }
 
 test.after(async () => {
@@ -199,3 +201,35 @@ test("conversation items keep a safe context ring even when no thread snapshot e
   assert.equal(directThread?.contextBudgetIndicator.percent, 100);
   assert.equal(directThread?.contextBudgetIndicator.level, "safe");
 });
+
+test("conversation items prefer latest observed codex activity over stale last message time", async () => {
+  await setup();
+  const state = await readState();
+  const baseProject = buildImportedThreadProject(
+    "mac-studio",
+    "stale-thread",
+    "Talking",
+    "talking",
+    "树莓派二代查询",
+    "thread-stale",
+    "2026-04-04T06:12:00+08:00",
+  );
+
+  state.projects = state.projects.filter((project) => project.id === "master-agent");
+  state.projects.push(
+    {
+      ...baseProject,
+      threadMeta: {
+        ...baseProject.threadMeta,
+        lastObservedCodexActivityAt: "2026-04-04T11:48:00+08:00",
+      },
+    },
+  );
+
+  const items = getConversationHomeItems(state);
+  const thread = items.find((item) => item.projectId === "stale-thread");
+
+  assert.ok(thread);
+  assert.equal(thread?.latestReplyAt, "2026-04-04T11:48:00+08:00");
+  assert.equal(thread?.latestReplyLabel, formatTimestampLabel("2026-04-04T11:48:00+08:00"));
+});