diff --git a/desktop/src/features/agents/agentConversations.test.mjs b/desktop/src/features/agents/agentConversations.test.mjs
index f8103e4e03..8443ce477a 100644
--- a/desktop/src/features/agents/agentConversations.test.mjs
+++ b/desktop/src/features/agents/agentConversations.test.mjs
@@ -564,3 +564,96 @@ test("dedicated conversation view stops at the next task anchor", () => {
 
   assert.deepEqual(visibleIds, ["root", "agent-reply", "first-task-reply"]);
 });
+
+test("dedicated conversation view keeps older task descendant replies", () => {
+  const root = message({
+    body: "Can you look into the data model?",
+    createdAt: 1,
+    id: "root",
+  });
+  const firstAnchor = message({
+    body: "I'll look into it.",
+    createdAt: 2,
+    id: "agent-reply",
+    pubkey: "agent",
+  });
+  const firstTaskReply = message({
+    body: "This belongs in the first task.",
+    createdAt: 3,
+    id: "first-task-reply",
+  });
+  const secondAnchor = message({
+    body: "Let's split this into another task.",
+    createdAt: 4,
+    id: "second-anchor",
+    pubkey: "agent",
+  });
+  const secondTaskReply = message({
+    body: "This belongs in the second task.",
+    createdAt: 5,
+    id: "second-task-reply",
+  });
+  const firstTaskFollowup = {
+    ...message({
+      body: "Continuing the first task after task two started.",
+      createdAt: 6,
+      id: "first-task-followup",
+    }),
+    parentId: "first-task-reply",
+    rootId: "root",
+  };
+  const plainRootReply = message({
+    body: "A plain root reply after task two should not join task one.",
+    createdAt: 7,
+    id: "plain-root-reply",
+  });
+  const messages = [
+    root,
+    firstAnchor,
+    firstTaskReply,
+    secondAnchor,
+    secondTaskReply,
+    firstTaskFollowup,
+    plainRootReply,
+  ];
+  const conversation = buildAgentConversation({
+    agentName: "Fizz",
+    agentPubkey: "agent",
+    agentReply: firstAnchor,
+    channel: { id: "channel", name: "general" },
+    contextMessages: messages,
+    parentMessage: root,
+    threadRootMessage: root,
+  });
+  const firstMarker = parseAgentConversationMarker(
+    markerEvent({ content: { startedAt: 2 }, createdAt: 2 }),
+  );
+  const secondMarker = parseAgentConversationMarker({
+    ...markerEvent({
+      content: { agentReplyId: "second-anchor", startedAt: 4 },
+      createdAt: 4,
+      id: "second-marker",
+    }),
+    tags: [
+      ["h", "channel"],
+      ["e", "root", "", "root"],
+      ["e", "second-anchor", "", "agent-reply"],
+      ["p", "agent"],
+      ["title", "Second task"],
+    ],
+  });
+  const markers = [firstMarker, secondMarker].filter(Boolean);
+
+  const visibleIds = messages
+    .filter((entry) =>
+      isConversationMessage(entry, conversation, markers, messages),
+    )
+    .map((entry) => entry.id);
+
+  assert.deepEqual(visibleIds, [
+    "root",
+    "agent-reply",
+    "first-task-reply",
+    "first-task-followup",
+  ]);
+});
diff --git a/desktop/src/features/agents/ui/AgentConversationScreen.helpers.ts b/desktop/src/features/agents/ui/AgentConversationScreen.helpers.ts
index 9c933bc602..42d2eee85d 100644
--- a/desktop/src/features/agents/ui/AgentConversationScreen.helpers.ts
+++ b/desktop/src/features/agents/ui/AgentConversationScreen.helpers.ts
@@ -93,6 +93,16 @@ export function isConversationMessage(
     return false;
   }
 
+  const markerAnchorIds = new Set(
+    markers
+      .filter(
+        (marker) =>
+          marker.channelId === conversation.channelId &&
+          marker.threadRootId === conversation.threadRootId &&
+          marker.agentReplyId !== conversation.agentReply.id,
+      )
+      .map((marker) => marker.agentReplyId),
+  );
   const orderedThreadMessages =
     messages.length > 0
       ? messages.filter(
@@ -133,7 +143,44 @@ export function isConversationMessage(
       }
     }
 
-    return messageIndex < nextAnchorIndex;
+    if (messageIndex < nextAnchorIndex) {
+      return true;
+    }
+
+    const selectedTaskMessageIds = new Set<string>();
+    for (const candidate of orderedThreadMessages) {
+      const candidateIndex = messageIndexById.get(candidate.id);
+      if (
+        candidateIndex !== undefined &&
+        candidateIndex >= anchorIndex &&
+        candidateIndex < nextAnchorIndex
+      ) {
+        selectedTaskMessageIds.add(candidate.id);
+      }
+    }
+    selectedTaskMessageIds.delete(conversation.threadRootId);
+
+    const messageById = new Map(
+      orderedThreadMessages.map((candidate) => [candidate.id, candidate]),
+    );
+    let parentId = message.parentId;
+    const visited = new Set<string>([message.id]);
+    while (parentId && !visited.has(parentId)) {
+      if (selectedTaskMessageIds.has(parentId)) {
+        return true;
+      }
+      if (
+        parentId === conversation.threadRootId ||
+        markerAnchorIds.has(parentId)
+      ) {
+        return false;
+      }
+
+      visited.add(parentId);
+      parentId = messageById.get(parentId)?.parentId ?? null;
+    }
+
+    return false;
   }
 
   const currentMarker =
diff --git a/desktop/src/features/agents/ui/AgentConversationScreen.tsx b/desktop/src/features/agents/ui/AgentConversationScreen.tsx
index 1f77560a5b..9d4294a557 100644
--- a/desktop/src/features/agents/ui/AgentConversationScreen.tsx
+++ b/desktop/src/features/agents/ui/AgentConversationScreen.tsx
@@ -135,7 +135,6 @@ export function AgentConversationScreen({
   const {
     getMessageReadAt,
     isThreadMuted,
-    markThreadRead,
     markMessageRead,
     updateAgentConversationTitle,
   } = useAppShell();
@@ -420,11 +419,6 @@ export function AgentConversationScreen({
     });
   }, [conversation, conversationSourceMessages, updateAgentConversationTitle]);
   React.useEffect(() => {
-    const latestMessage = timelineMessages[timelineMessages.length - 1] ?? null;
-    if (latestMessage) {
-      markThreadRead(conversation.threadRootId, latestMessage.createdAt);
-    }
-
     if (isThreadMuted(conversation.threadRootId)) {
       return;
     }
@@ -440,9 +434,19 @@ export function AgentConversationScreen({
     getMessageReadAt,
     isThreadMuted,
     markMessageRead,
-    markThreadRead,
     timelineMessages,
   ]);
+  const replyParentEventId = React.useMemo(() => {
+    const latestTaskMessage = [...timelineMessages]
+      .reverse()
+      .find((message) => message.id !== conversation.threadRootId);
+
+    return (
+      latestTaskMessage?.id ??
+      conversation.agentReply.id ??
+      conversation.threadRootId
+    );
+  }, [conversation.agentReply.id, conversation.threadRootId, timelineMessages]);
   const routeableAgentPubkeys = React.useMemo(
     () =>
       agentParticipants
@@ -539,10 +543,10 @@ export function AgentConversationScreen({
           autoRouteAgentPubkeys: autoRoutedAgentPubkeys,
           mentionPubkeys,
         }),
-        parentEventId: conversation.threadRootId,
+        parentEventId: replyParentEventId,
       });
     },
-    [autoRoutedAgentPubkeys, conversation.threadRootId, sendMessageMutation],
+    [autoRoutedAgentPubkeys, replyParentEventId, sendMessageMutation],
   );
 
   const isComposerDisabled =
@@ -734,6 +738,7 @@ export function AgentConversationScreen({
         emptyTitle="No conversation messages yet"
         hasComposerOverlay
         isLoading={messagesQuery.isLoading && timelineMessages.length === 0}
+        layoutShiftKey={conversation.id}
         messageListPlacement="top"
         messages={timelineMessages}
         profiles={profiles}