diff --git a/crates/buzz-relay/src/handlers/side_effects.rs b/crates/buzz-relay/src/handlers/side_effects.rs
index c5485721b0..3da8f3ab71 100644
--- a/crates/buzz-relay/src/handlers/side_effects.rs
+++ b/crates/buzz-relay/src/handlers/side_effects.rs
@@ -169,8 +169,9 @@ pub async fn handle_side_effects(
 
 /// Validate a standard NIP-09 deletion event before it is stored.
 ///
-/// Buzz accepts standard deletions for self-authored events only. Channel
-/// admin deletions continue to use kind 9005.
+/// Buzz accepts standard deletions for self-authored events, plus the owning
+/// human deleting their agent's events (mirrors `validate_edit_ownership`).
+/// Channel admin deletions continue to use kind 9005.
 pub async fn validate_standard_deletion_event(
     tenant: &TenantContext,
     event: &Event,
@@ -193,7 +194,12 @@ pub async fn validate_standard_deletion_event(
         }
         let target_pubkey_bytes =
             hex::decode(parts[1]).map_err(|_| anyhow::anyhow!("invalid pubkey in a-tag"))?;
-        if target_pubkey_bytes != actor_bytes {
+        if target_pubkey_bytes != actor_bytes
+            && !state
+                .db
+                .is_agent_owner(tenant.community(), &target_pubkey_bytes, &actor_bytes)
+                .await?
+        {
             return Err(anyhow::anyhow!("must be event author"));
         }
         return Ok(());
@@ -208,7 +214,12 @@ pub async fn validate_standard_deletion_event(
 
         let target_author =
             effective_message_author(&target_event.event, &state.relay_keypair.public_key());
-        if target_author != actor_bytes {
+        if target_author != actor_bytes
+            && !state
+                .db
+                .is_agent_owner(tenant.community(), &target_author, &actor_bytes)
+                .await?
+        {
             return Err(anyhow::anyhow!("must be event author"));
         }
     }
diff --git a/crates/buzz-test-client/tests/e2e_human_edit_agent_content.rs b/crates/buzz-test-client/tests/e2e_human_edit_agent_content.rs
index 57a888e102..0e11e567d6 100644
--- a/crates/buzz-test-client/tests/e2e_human_edit_agent_content.rs
+++ b/crates/buzz-test-client/tests/e2e_human_edit_agent_content.rs
@@ -1,7 +1,8 @@
 //! End-to-end tests for human owners editing/managing content authored by
-//! their agents — all four authorization predicate sites:
+//! their agents — all five authorization predicate sites:
 //!
 //! - kind:40003 message edit (`validate_edit_ownership`)
+//! - kind:5 standard deletion (`validate_standard_deletion_event`)
 //! - kind:9005 DELETE_EVENT (`validate_admin_event` 9005 branch)
 //! - kind:9002 EDIT_METADATA privileged-tag branch
 //! - kind:9008 DELETE_GROUP
@@ -309,6 +310,97 @@ async fn test_third_party_cannot_delete_agent_message() {
     third_party_client.disconnect().await.ok();
 }
 
+// ─── kind:5 standard deletion ───────────────────────────────────────────────
+
+/// Owner can delete a message authored by their agent via standard NIP-09
+/// kind:5 (the deletion kind the desktop app sends).
+#[tokio::test]
+#[ignore]
+async fn test_owner_can_delete_agent_message_kind5() {
+    let owner_keys = Keys::generate();
+    let agent_keys = Keys::generate();
+    let channel_id = create_agent_owned_channel(&agent_keys).await;
+
+    let mut agent_client = connect_agent_with_owner(&agent_keys, &owner_keys).await;
+
+    let content = format!("agent-msg-{}", uuid::Uuid::new_v4());
+    let ok = agent_client
+        .send_text_message(&agent_keys, &channel_id, &content, 9)
+        .await
+        .expect("agent send message");
+    assert!(ok.accepted, "agent message rejected: {}", ok.message);
+    let msg_event_id = ok.event_id;
+
+    let mut owner_client = BuzzTestClient::connect(&relay_url(), &owner_keys)
+        .await
+        .expect("connect owner");
+
+    let delete_event = EventBuilder::new(Kind::Custom(5), "")
+        .tags(vec![
+            Tag::parse(["e", &msg_event_id]).unwrap(),
+            Tag::parse(["h", &channel_id]).unwrap(),
+        ])
+        .sign_with_keys(&owner_keys)
+        .unwrap();
+
+    let ok = owner_client
+        .send_event(delete_event)
+        .await
+        .expect("send delete");
+    assert!(
+        ok.accepted,
+        "owner kind:5 delete of agent message rejected: {}",
+        ok.message
+    );
+
+    agent_client.disconnect().await.ok();
+    owner_client.disconnect().await.ok();
+}
+
+/// An unrelated third party cannot delete an agent's message via kind:5.
+#[tokio::test]
+#[ignore]
+async fn test_third_party_cannot_delete_agent_message_kind5() {
+    let owner_keys = Keys::generate();
+    let agent_keys = Keys::generate();
+    let third_party_keys = Keys::generate();
+    let channel_id = create_agent_owned_channel(&agent_keys).await;
+
+    let mut agent_client = connect_agent_with_owner(&agent_keys, &owner_keys).await;
+
+    let content = format!("agent-msg-{}", uuid::Uuid::new_v4());
+    let ok = agent_client
+        .send_text_message(&agent_keys, &channel_id, &content, 9)
+        .await
+        .expect("agent send message");
+    assert!(ok.accepted, "agent message rejected: {}", ok.message);
+    let msg_event_id = ok.event_id;
+
+    let mut third_party_client = BuzzTestClient::connect(&relay_url(), &third_party_keys)
+        .await
+        .expect("connect third party");
+
+    let delete_event = EventBuilder::new(Kind::Custom(5), "")
+        .tags(vec![
+            Tag::parse(["e", &msg_event_id]).unwrap(),
+            Tag::parse(["h", &channel_id]).unwrap(),
+        ])
+        .sign_with_keys(&third_party_keys)
+        .unwrap();
+
+    let ok = third_party_client
+        .send_event(delete_event)
+        .await
+        .expect("send delete attempt");
+    assert!(
+        !ok.accepted,
+        "third party should NOT be able to kind:5-delete agent message, but was accepted"
+    );
+
+    agent_client.disconnect().await.ok();
+    third_party_client.disconnect().await.ok();
+}
+
 // ─── kind:9002 EDIT_METADATA ────────────────────────────────────────────────
 
 /// Owner can edit metadata (name/archived) of a channel owned by their agent,
diff --git a/desktop/src/features/channels/useChannelPaneHandlers.ts b/desktop/src/features/channels/useChannelPaneHandlers.ts
index efe36c70b2..078b0aff61 100644
--- a/desktop/src/features/channels/useChannelPaneHandlers.ts
+++ b/desktop/src/features/channels/useChannelPaneHandlers.ts
@@ -112,7 +112,8 @@ export function useChannelPaneHandlers({
   }, [setEditTargetId]);
 
   const handleDelete = React.useCallback(async (message: { id: string }) => {
-    await deleteMutateRef.current({ eventId: message.id });
+    // Failure is surfaced via the mutation's onError toast.
+    await deleteMutateRef.current({ eventId: message.id }).catch(() => {});
   }, []);
 
   const handleEdit = React.useCallback(
diff --git a/desktop/src/features/messages/hooks.ts b/desktop/src/features/messages/hooks.ts
index f262d9e79e..0517d25d75 100644
--- a/desktop/src/features/messages/hooks.ts
+++ b/desktop/src/features/messages/hooks.ts
@@ -1,5 +1,6 @@
 import { useEffect, useEffectEvent } from "react";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
+import { toast } from "sonner";
 
 import {
   channelMessagesKey,
@@ -703,6 +704,9 @@ export function useDeleteMessageMutation(channel: Channel | null) {
         (current = []) => current.filter((message) => message.id !== eventId),
       );
     },
+    onError: (error) => {
+      toast.error(`Failed to delete message: ${error.message}`);
+    },
   });
 }
 
diff --git a/mobile/lib/features/channels/channel_detail_page/message_bubble.dart b/mobile/lib/features/channels/channel_detail_page/message_bubble.dart
index 22e3a87971..0226316f71 100644
--- a/mobile/lib/features/channels/channel_detail_page/message_bubble.dart
+++ b/mobile/lib/features/channels/channel_detail_page/message_bubble.dart
@@ -47,8 +47,10 @@ class _MessageBubble extends ConsumerWidget {
         ref: ref,
         message: message,
         channelId: currentChannelId,
-        isOwnMessage:
-            currentPubkey?.toLowerCase() == message.pubkey.toLowerCase(),
+        canManageMessage:
+            currentPubkey?.toLowerCase() == pk ||
+            (profile?.ownerPubkey != null &&
+                profile?.ownerPubkey == currentPubkey?.toLowerCase()),
         allMessages: allMessages,
         currentPubkey: currentPubkey,
         isMember: isMember,
diff --git a/mobile/lib/features/channels/channel_detail_page/system_rows.dart b/mobile/lib/features/channels/channel_detail_page/system_rows.dart
index 6420e7e936..f2dcb420d6 100644
--- a/mobile/lib/features/channels/channel_detail_page/system_rows.dart
+++ b/mobile/lib/features/channels/channel_detail_page/system_rows.dart
@@ -41,7 +41,7 @@ class _SystemMessageRow extends ConsumerWidget {
         ref: ref,
         message: message,
         channelId: channelId,
-        isOwnMessage: false,
+        canManageMessage: false,
         allMessages: null,
         currentPubkey: currentPubkey,
         isMember: isMember,
diff --git a/mobile/lib/features/channels/message_actions.dart b/mobile/lib/features/channels/message_actions.dart
index 4ff6a13247..fe03bcb65e 100644
--- a/mobile/lib/features/channels/message_actions.dart
+++ b/mobile/lib/features/channels/message_actions.dart
@@ -25,7 +25,7 @@ void showMessageActions({
   required WidgetRef ref,
   required TimelineMessage message,
   required String channelId,
-  required bool isOwnMessage,
+  required bool canManageMessage,
   List<TimelineMessage>? allMessages,
   String? currentPubkey,
   bool isMember = false,
@@ -129,7 +129,7 @@ void showMessageActions({
                   Clipboard.setData(data);
                 },
               ),
-            if (isOwnMessage) ...[
+            if (canManageMessage) ...[
               ListTile(
                 leading: const Icon(LucideIcons.pencil),
                 title: const Text('Edit message'),
@@ -256,9 +256,15 @@ void _confirmDelete({
         FilledButton(
           onPressed: () {
             Navigator.of(dialogContext).pop();
+            final messenger = ScaffoldMessenger.of(context);
             ref
                 .read(channelActionsProvider)
-                .deleteMessage(channelId: channelId, eventId: messageId);
+                .deleteMessage(channelId: channelId, eventId: messageId)
+                .catchError((Object error) {
+                  messenger.showSnackBar(
+                    SnackBar(content: Text('Failed to delete message: $error')),
+                  );
+                });
           },
           style: FilledButton.styleFrom(
             backgroundColor: dialogContext.colors.error,
diff --git a/mobile/lib/features/channels/thread_detail_page.dart b/mobile/lib/features/channels/thread_detail_page.dart
index 04522418a4..711508d734 100644
--- a/mobile/lib/features/channels/thread_detail_page.dart
+++ b/mobile/lib/features/channels/thread_detail_page.dart
@@ -401,8 +401,10 @@ class _ThreadMessage extends ConsumerWidget {
         ref: ref,
         message: message,
         channelId: channelId,
-        isOwnMessage:
-            currentPubkey?.toLowerCase() == message.pubkey.toLowerCase(),
+        canManageMessage:
+            currentPubkey?.toLowerCase() == pk ||
+            (profile?.ownerPubkey != null &&
+                profile?.ownerPubkey == currentPubkey?.toLowerCase()),
         allMessages: allMessages,
         currentPubkey: currentPubkey,
         isMember: isMember,