diff --git a/desktop/scripts/check-file-sizes.mjs b/desktop/scripts/check-file-sizes.mjs
index 530d2b336..1604dcc30 100644
--- a/desktop/scripts/check-file-sizes.mjs
+++ b/desktop/scripts/check-file-sizes.mjs
@@ -38,7 +38,7 @@ const overrides = new Map([
   ["src/features/settings/ui/SettingsView.tsx", 600],
   ["src/features/sidebar/ui/AppSidebar.tsx", 850], // channels + forums creation forms
   ["src/features/tokens/ui/TokenSettingsCard.tsx", 800],
-  ["src/shared/api/relayClientSession.ts", 725], // durable websocket session manager with reconnect/replay/recovery state
+  ["src/shared/api/relayClientSession.ts", 740], // durable websocket session manager with reconnect/replay/recovery state + sendTypingIndicator
   ["src/shared/api/tauri.ts", 1100], // remote agent provider API bindings + canvas API functions
   ["src-tauri/src/commands/agents.rs", 845], // remote agent lifecycle routing (local + provider branches) + scope enforcement; rustfmt adds line breaks around long tuple/closure blocks
   ["src-tauri/src/managed_agents/backend.rs", 530], // provider IPC, validation, discovery, binary resolution + tests
diff --git a/desktop/src/features/messages/ui/MessageComposer.tsx b/desktop/src/features/messages/ui/MessageComposer.tsx
index 25232f2f3..e1d85f919 100644
--- a/desktop/src/features/messages/ui/MessageComposer.tsx
+++ b/desktop/src/features/messages/ui/MessageComposer.tsx
@@ -3,6 +3,7 @@ import * as React from "react";
 import { useChannelLinks } from "@/features/messages/lib/useChannelLinks";
 import type { ChannelSuggestion } from "@/features/messages/lib/useChannelLinks";
 import { useMentions } from "@/features/messages/lib/useMentions";
+import { useTypingBroadcast } from "@/features/messages/useTypingBroadcast";
 import {
   type BlobDescriptor,
   pickAndUploadMedia,
@@ -63,6 +64,7 @@ export function MessageComposer({
 
   const mentions = useMentions(channelId);
   const channelLinks = useChannelLinks();
+  const notifyTyping = useTypingBroadcast(channelId);
 
   const [uploadState, setUploadState] = React.useState<{
     status: "idle" | "uploading" | "error";
@@ -371,11 +373,15 @@ export function MessageComposer({
       updateDraftSelection(event.target);
       mentions.updateMentionQuery(nextContent, cursorPos);
       channelLinks.updateChannelQuery(nextContent, cursorPos);
+      if (nextContent.trim().length > 0) {
+        notifyTyping();
+      }
     },
     [
       updateDraftSelection,
       mentions.updateMentionQuery,
       channelLinks.updateChannelQuery,
+      notifyTyping,
     ],
   );
 
diff --git a/desktop/src/features/messages/useTypingBroadcast.ts b/desktop/src/features/messages/useTypingBroadcast.ts
new file mode 100644
index 000000000..80175318a
--- /dev/null
+++ b/desktop/src/features/messages/useTypingBroadcast.ts
@@ -0,0 +1,39 @@
+import { useCallback, useRef } from "react";
+
+import { relayClient } from "@/shared/api/relayClient";
+
+const TYPING_SEND_INTERVAL_MS = 3_000;
+
+/**
+ * Publishes kind:20002 typing indicators for the current user,
+ * throttled to at most once every 3 seconds per channel.
+ */
+export function useTypingBroadcast(channelId: string | null | undefined) {
+  const lastSentRef = useRef(0);
+  const lastChannelRef = useRef(channelId);
+  const channelIdRef = useRef(channelId);
+  channelIdRef.current = channelId;
+
+  const notifyTyping = useCallback(() => {
+    const id = channelIdRef.current;
+    if (!id) {
+      return;
+    }
+
+    // Reset throttle when channel changes.
+    if (lastChannelRef.current !== id) {
+      lastChannelRef.current = id;
+      lastSentRef.current = 0;
+    }
+
+    const now = Date.now();
+    if (now - lastSentRef.current < TYPING_SEND_INTERVAL_MS) {
+      return;
+    }
+
+    lastSentRef.current = now;
+    relayClient.sendTypingIndicator(id).catch(() => {});
+  }, []);
+
+  return notifyTyping;
+}
diff --git a/desktop/src/shared/api/relayClientSession.ts b/desktop/src/shared/api/relayClientSession.ts
index d27cf2d83..446483582 100644
--- a/desktop/src/shared/api/relayClientSession.ts
+++ b/desktop/src/shared/api/relayClientSession.ts
@@ -125,6 +125,21 @@ export class RelayClient {
     );
   }
 
+  async sendTypingIndicator(channelId: string) {
+    // Bail when disconnected — not worth triggering a reconnect for ephemeral typing events.
+    if (this.wsId === null) {
+      return;
+    }
+    const event = await signRelayEvent({
+      kind: KIND_TYPING_INDICATOR,
+      content: "",
+      tags: [["h", channelId]],
+    });
+
+    // Fire-and-forget: no need to wait for relay acknowledgement.
+    void this.sendRaw(["EVENT", event]).catch(() => {});
+  }
+
   async subscribeToChannel(
     channelId: string,
     onEvent: (event: RelayEvent) => void,