diff --git a/app/lib/main.dart b/app/lib/main.dart
index c0de2b7..e1a0827 100644
--- a/app/lib/main.dart
+++ b/app/lib/main.dart
@@ -2944,6 +2944,9 @@ class MeshNode {
   }
 }
 
+/// The protocol identifier sent to the API to filter results to Meshtastic only.
+const String _kProtocolFilter = 'meshtastic';
+
 /// Build a messages API URI for a given domain or absolute URL.
 Uri _buildMessagesUri(String domain, {int since = 0, int limit = 1000}) {
   final trimmed = domain.trim();
@@ -2951,6 +2954,7 @@ Uri _buildMessagesUri(String domain, {int since = 0, int limit = 1000}) {
     'limit': limit.toString(),
     'encrypted': 'false',
     'since': since.toString(),
+    'protocol': _kProtocolFilter,
   };
   if (trimmed.isEmpty) {
     return Uri.https('potatomesh.net', '/api/messages', params);
@@ -2988,7 +2992,7 @@ Uri _buildNodeUri(String domain, String nodeId) {
 /// Build the bulk nodes API URI for fetching recent nodes.
 Uri _buildNodesUri(String domain, {int limit = 1000}) {
   final trimmedDomain = domain.trim();
-  final params = {'limit': limit.toString()};
+  final params = {'limit': limit.toString(), 'protocol': _kProtocolFilter};
 
   if (trimmedDomain.isEmpty) {
     return Uri.https('potatomesh.net', '/api/nodes', params);
diff --git a/app/test/mesh_message_test.dart b/app/test/mesh_message_test.dart
index cd5cd75..9b86b34 100644
--- a/app/test/mesh_message_test.dart
+++ b/app/test/mesh_message_test.dart
@@ -206,8 +206,10 @@ void main() {
 
       expect(calls[0].host, 'mesh.example.org');
       expect(calls[0].path, '/api/messages');
+      expect(calls[0].queryParameters['protocol'], 'meshtastic');
       expect(calls[1].scheme, 'https');
       expect(calls[1].path, '/api/messages');
+      expect(calls[1].queryParameters['protocol'], 'meshtastic');
     });
   });
 
diff --git a/app/test/mesh_repository_test.dart b/app/test/mesh_repository_test.dart
index ca702da..14a3f16 100644
--- a/app/test/mesh_repository_test.dart
+++ b/app/test/mesh_repository_test.dart
@@ -145,6 +145,7 @@ void main() {
       if (request.url.path == '/api/messages') {
         sinces.add(request.url.queryParameters['since'] ?? '');
         expect(request.url.queryParameters['limit'], '1000');
+        expect(request.url.queryParameters['protocol'], 'meshtastic');
         if (sinces.length == 1) {
           return http.Response(
             jsonEncode([
diff --git a/matrix/src/potatomesh.rs b/matrix/src/potatomesh.rs
index fc55cbe..c815680 100644
--- a/matrix/src/potatomesh.rs
+++ b/matrix/src/potatomesh.rs
@@ -19,6 +19,11 @@ use tokio::sync::RwLock;
 
 use crate::config::PotatomeshConfig;
 
+/// Protocol identifier sent as a query parameter to restrict API results to
+/// Meshtastic data only. Other protocols (e.g. MeshCore) are excluded until
+/// the clients are updated to support them.
+const PROTOCOL_FILTER: &str = "meshtastic";
+
 #[allow(dead_code)]
 #[derive(Debug, Deserialize, Clone)]
 pub struct PotatoMessage {
@@ -131,7 +136,10 @@ impl PotatoClient {
     }
 
     pub async fn fetch_messages(&self, params: FetchParams) -> anyhow::Result<Vec<PotatoMessage>> {
-        let mut req = self.http.get(self.messages_url());
+        let mut req = self
+            .http
+            .get(self.messages_url())
+            .query(&[("protocol", PROTOCOL_FILTER)]);
         if let Some(limit) = params.limit {
             req = req.query(&[("limit", limit)]);
         }
@@ -336,7 +344,10 @@ mod tests {
         let mut server = mockito::Server::new_async().await;
         let mock = server
             .mock("GET", "/api/messages")
-            .match_query(mockito::Matcher::Any) // allow optional query params
+            .match_query(mockito::Matcher::UrlEncoded(
+                "protocol".into(),
+                "meshtastic".into(),
+            ))
             .with_status(200)
             .with_header("content-type", "application/json")
             .with_body(
@@ -427,7 +438,10 @@ mod tests {
         let mut server = mockito::Server::new_async().await;
         let mock = server
             .mock("GET", "/api/messages")
-            .match_query(mockito::Matcher::Any)
+            .match_query(mockito::Matcher::UrlEncoded(
+                "protocol".into(),
+                PROTOCOL_FILTER.into(),
+            ))
             .with_status(500)
             .create();
 
@@ -448,7 +462,11 @@ mod tests {
         let mut server = mockito::Server::new_async().await;
         let mock = server
             .mock("GET", "/api/messages")
-            .match_query("limit=10&since=123")
+            .match_query(mockito::Matcher::AllOf(vec![
+                mockito::Matcher::UrlEncoded("protocol".into(), PROTOCOL_FILTER.into()),
+                mockito::Matcher::UrlEncoded("limit".into(), "10".into()),
+                mockito::Matcher::UrlEncoded("since".into(), "123".into()),
+            ]))
             .with_status(200)
             .with_header("content-type", "application/json")
             .with_body("[]")