diff --git a/desktop/src/features/agents/lib/agentAutocompleteEligibility.ts b/desktop/src/features/agents/lib/agentAutocompleteEligibility.ts
index e4afe7fea4..6763cbb7d5 100644
--- a/desktop/src/features/agents/lib/agentAutocompleteEligibility.ts
+++ b/desktop/src/features/agents/lib/agentAutocompleteEligibility.ts
@@ -57,10 +57,16 @@ export function getMentionableAgentPubkeys({
 export function isAgentIdentityInManagedList(
   candidate: { isAgent?: boolean; pubkey: string },
   managedAgentPubkeys: ReadonlySet<string>,
+  mentionableAgentPubkeys?: ReadonlySet<string>,
 ) {
+  const pubkey = normalizePubkey(candidate.pubkey);
   return (
     candidate.isAgent !== true ||
-    managedAgentPubkeys.has(normalizePubkey(candidate.pubkey))
+    managedAgentPubkeys.has(pubkey) ||
+    // Externally-hosted agents (relay directory, kind:10100) that are
+    // invocable for the current user are legitimate mention targets even
+    // though no local managed-agent record exists for them.
+    (mentionableAgentPubkeys?.has(pubkey) ?? false)
   );
 }
 
diff --git a/desktop/src/features/messages/lib/useMentions.ts b/desktop/src/features/messages/lib/useMentions.ts
index 0c73b75339..bd944e141f 100644
--- a/desktop/src/features/messages/lib/useMentions.ts
+++ b/desktop/src/features/messages/lib/useMentions.ts
@@ -246,7 +246,13 @@ export function useMentions(
       if (isArchivedDiscovery(pubkey)) {
         return;
       }
-      if (!isAgentIdentityInManagedList(candidate, managedAgentPubkeys)) {
+      if (
+        !isAgentIdentityInManagedList(
+          candidate,
+          managedAgentPubkeys,
+          mentionableAgentPubkeys,
+        )
+      ) {
         return;
       }
       if (