diff --git a/desktop/src/features/channels/ui/ChannelPane.helpers.test.mjs b/desktop/src/features/channels/ui/ChannelPane.helpers.test.mjs
index b94a8974b..ab79b6d49 100644
--- a/desktop/src/features/channels/ui/ChannelPane.helpers.test.mjs
+++ b/desktop/src/features/channels/ui/ChannelPane.helpers.test.mjs
@@ -4,6 +4,7 @@ import test from "node:test";
 import {
   canOpenAgentConversationInChannel,
   getDmTaskAgentPubkeys,
+  getThreadTaskAgentPubkeys,
   mergeAutoRouteMentionPubkeys,
 } from "./ChannelPane.helpers.ts";
 
@@ -114,3 +115,61 @@ test("DM task agent inference requires exactly one other known agent", () => {
     [],
   );
 });
+
+test("thread task agent inference requires exactly one known agent and one human", () => {
+  const knownAgentPubkeys = new Set(["agent-one", "agent-two"]);
+
+  assert.deepEqual(
+    getThreadTaskAgentPubkeys({
+      currentPubkey: "human",
+      knownAgentPubkeys,
+      messages: [
+        {
+          pubkey: "human",
+          tags: [["p", "agent-one"]],
+        },
+        {
+          pubkey: "agent-one",
+          tags: [["p", "human"]],
+        },
+      ],
+    }),
+    ["agent-one"],
+  );
+
+  assert.deepEqual(
+    getThreadTaskAgentPubkeys({
+      currentPubkey: "human",
+      knownAgentPubkeys,
+      messages: [
+        {
+          pubkey: "human",
+          tags: [["p", "agent-one"]],
+        },
+        {
+          pubkey: "other-human",
+          tags: [["p", "human"]],
+        },
+      ],
+    }),
+    [],
+  );
+
+  assert.deepEqual(
+    getThreadTaskAgentPubkeys({
+      currentPubkey: "human",
+      knownAgentPubkeys,
+      messages: [
+        {
+          pubkey: "human",
+          tags: [["p", "agent-one"]],
+        },
+        {
+          pubkey: "agent-two",
+          tags: [["p", "human"]],
+        },
+      ],
+    }),
+    [],
+  );
+});
diff --git a/desktop/src/features/channels/ui/ChannelPane.helpers.ts b/desktop/src/features/channels/ui/ChannelPane.helpers.ts
index 8643525ce..bcb47c02b 100644
--- a/desktop/src/features/channels/ui/ChannelPane.helpers.ts
+++ b/desktop/src/features/channels/ui/ChannelPane.helpers.ts
@@ -3,6 +3,7 @@ import type { TimelineMessage } from "@/features/messages/types";
 import type { Channel } from "@/shared/api/types";
 import { KIND_SYSTEM_MESSAGE } from "@/shared/constants/kinds";
 import { normalizePubkey } from "@/shared/lib/pubkey";
+import { getMentionTagPubkey } from "@/shared/lib/resolveMentionNames";
 
 export function getChannelIntroKind(channel: Channel): string {
   const isPrivate = channel.visibility === "private";
@@ -120,6 +121,53 @@ export function getDmTaskAgentPubkeys({
   );
 }
 
+export function getThreadTaskAgentPubkeys({
+  currentPubkey,
+  knownAgentPubkeys,
+  messages,
+}: {
+  currentPubkey?: string;
+  knownAgentPubkeys: ReadonlySet<string>;
+  messages: readonly TimelineMessage[];
+}) {
+  const normalizedCurrentPubkey = currentPubkey
+    ? normalizePubkey(currentPubkey)
+    : null;
+  const participants = new Map<string, string>();
+
+  const addParticipant = (pubkey: string | null | undefined) => {
+    if (!pubkey) {
+      return;
+    }
+    const normalized = normalizePubkey(pubkey);
+    if (!normalized || participants.has(normalized)) {
+      return;
+    }
+    participants.set(normalized, pubkey);
+  };
+
+  for (const message of messages) {
+    addParticipant(message.pubkey);
+    for (const tag of message.tags ?? []) {
+      addParticipant(getMentionTagPubkey(tag));
+    }
+  }
+
+  const agentPubkeys = new Map<string, string>();
+
+  for (const [normalized, pubkey] of participants) {
+    if (normalizedCurrentPubkey && normalized === normalizedCurrentPubkey) {
+      continue;
+    }
+    if (!knownAgentPubkeys.has(normalized)) {
+      return [];
+    }
+    agentPubkeys.set(normalized, pubkey);
+  }
+
+  return agentPubkeys.size === 1 ? [...agentPubkeys.values()] : [];
+}
+
 export function mergeAutoRouteMentionPubkeys({
   autoRouteAgentPubkeys,
   mentionPubkeys,
@@ -148,3 +196,20 @@ export function mergeAutoRouteMentionPubkeys({
 
   return merged;
 }
+
+export function mergeTaskAgentMentionPubkeys({
+  agentPubkeys,
+  mentionPubkeys,
+}: {
+  agentPubkeys: readonly string[];
+  mentionPubkeys: string[];
+}) {
+  if (agentPubkeys.length === 0) {
+    return mentionPubkeys;
+  }
+
+  return mergeAutoRouteMentionPubkeys({
+    autoRouteAgentPubkeys: agentPubkeys,
+    mentionPubkeys,
+  });
+}
diff --git a/desktop/src/features/channels/ui/ChannelPane.tsx b/desktop/src/features/channels/ui/ChannelPane.tsx
index 50c020b79..520f6e916 100644
--- a/desktop/src/features/channels/ui/ChannelPane.tsx
+++ b/desktop/src/features/channels/ui/ChannelPane.tsx
@@ -44,7 +44,9 @@ import {
   getChannelIntroDescription,
   getChannelIntroKind,
   getDmTaskAgentPubkeys,
+  getThreadTaskAgentPubkeys,
   isWelcomeSetupSystemMessage,
+  mergeTaskAgentMentionPubkeys,
   mentionsKnownAgent,
 } from "@/features/channels/ui/ChannelPane.helpers";
 import type { ChannelPaneProps } from "@/features/channels/ui/ChannelPane.types";
@@ -421,13 +423,17 @@ export const ChannelPane = React.memo(function ChannelPane({
       mentionPubkeys: string[],
       mediaTags?: string[][],
     ) => {
+      const sendMentionPubkeys = mergeTaskAgentMentionPubkeys({
+        agentPubkeys: dmTaskAgentPubkeys,
+        mentionPubkeys,
+      });
       const shouldCompleteWelcomeBanner =
         isActiveWelcomeChannel &&
         (containsWelcomePersonaMention(content) ||
-          mentionsKnownAgent(mentionPubkeys, knownAgentPubkeys));
+          mentionsKnownAgent(sendMentionPubkeys, knownAgentPubkeys));
 
       messageTimelineRef.current?.scrollToBottomOnNextUpdate();
-      await onSendMessage(content, mentionPubkeys, mediaTags);
+      await onSendMessage(content, sendMentionPubkeys, mediaTags);
 
       if (shouldCompleteWelcomeBanner) {
         completeWelcomeComposerBanner();
@@ -435,6 +441,7 @@ export const ChannelPane = React.memo(function ChannelPane({
     },
     [
       completeWelcomeComposerBanner,
+      dmTaskAgentPubkeys,
       isActiveWelcomeChannel,
       knownAgentPubkeys,
       onSendMessage,
@@ -764,6 +771,22 @@ export const ChannelPane = React.memo(function ChannelPane({
       ...threadMessages.map((entry) => entry.message),
     ];
   }, [threadHeadMessage, threadMessages]);
+  const threadTaskAgentPubkeys = getThreadTaskAgentPubkeys({
+    currentPubkey,
+    knownAgentPubkeys,
+    messages: threadSourceMessages,
+  });
+  const handleSendThreadReply = React.useCallback(
+    (content: string, mentionPubkeys: string[], mediaTags?: string[][]) => {
+      const sendMentionPubkeys = mergeTaskAgentMentionPubkeys({
+        agentPubkeys: threadTaskAgentPubkeys,
+        mentionPubkeys,
+      });
+
+      return onSendThreadReply(content, sendMentionPubkeys, mediaTags);
+    },
+    [onSendThreadReply, threadTaskAgentPubkeys],
+  );
   const hiddenAgentConversationMessageIds = React.useMemo(() => {
     if (!enableAgentConversations) {
       return new Set<string>();
@@ -1194,7 +1217,7 @@ export const ChannelPane = React.memo(function ChannelPane({
                   : undefined
               }
               onSelectReplyTarget={onSelectThreadReplyTarget}
-              onSend={onSendThreadReply}
+              onSend={handleSendThreadReply}
               onScrollTargetResolved={onThreadScrollTargetResolved}
               onToggleReaction={onToggleReaction}
               onUnfollowThread={onUnfollowThread}