diff --git a/crates/defguard_proxy_manager/src/lib.rs b/crates/defguard_proxy_manager/src/lib.rs
index ea4ffef294..6057dea7be 100644
--- a/crates/defguard_proxy_manager/src/lib.rs
+++ b/crates/defguard_proxy_manager/src/lib.rs
@@ -35,7 +35,7 @@ use defguard_core::{
 use defguard_mail::Mail;
 use defguard_proto::proxy::{
     AuthCallbackResponse, AuthInfoResponse, CoreError, CoreRequest, CoreResponse, DerPayload,
-    InitialSetupInfo, core_request, core_response, proxy_client::ProxyClient,
+    InitialInfo, InitialSetupInfo, core_request, core_response, proxy_client::ProxyClient,
     proxy_setup_client::ProxySetupClient,
 };
 use defguard_version::{
@@ -58,7 +58,6 @@ use tokio::{
 use tokio_stream::wrappers::UnboundedReceiverStream;
 use tonic::{
     Code, Streaming,
-    metadata::MetadataValue,
     transport::{Certificate, ClientTlsConfig, Endpoint},
 };
 
@@ -73,7 +72,6 @@ extern crate tracing;
 const TEN_SECS: Duration = Duration::from_secs(10);
 const PROXY_AFTER_SETUP_CONNECT_DELAY: Duration = Duration::from_secs(1);
 static VERSION_ZERO: Version = Version::new(0, 0, 0);
-static COOKIE_KEY_HEADER: &str = "dg-cookie-key-bin";
 
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
 pub(crate) enum Scheme {
@@ -376,16 +374,7 @@ impl ProxyServer {
             let interceptor = ClientVersionInterceptor::new(Version::parse(VERSION)?);
             let mut client = ProxyClient::with_interceptor(endpoint.connect_lazy(), interceptor);
             let (tx, rx) = mpsc::unbounded_channel();
-            let mut request = tonic::Request::new(UnboundedReceiverStream::new(rx));
-            let config = server_config();
-
-            // Derive proxy cookie key from core secret to avoid transmitting it.
-            let proxy_cookie_key = Key::derive_from(config.secret_key.expose_secret().as_bytes());
-            request.metadata_mut().insert_bin(
-                COOKIE_KEY_HEADER,
-                MetadataValue::from_bytes(proxy_cookie_key.master()),
-            );
-            let response = match client.bidi(request).await {
+            let response = match client.bidi(UnboundedReceiverStream::new(rx)).await {
                 Ok(response) => response,
                 Err(err) => {
                     match err.code() {
@@ -435,6 +424,20 @@ impl ProxyServer {
 
             info!("Connected to proxy at {}", endpoint.uri());
             let mut resp_stream = response.into_inner();
+
+            // Derive proxy cookie key from core secret to avoid transmitting it over gRPC.
+            let config = server_config();
+            let proxy_cookie_key = Key::derive_from(config.secret_key.expose_secret().as_bytes());
+
+            // Send initial info with private cookies key.
+            let initial_info = InitialInfo {
+                private_cookies_key: proxy_cookie_key.master().to_vec(),
+            };
+            let _ = tx.send(CoreResponse {
+                id: 0,
+                payload: Some(core_response::Payload::InitialInfo(initial_info)),
+            });
+
             self.message_loop(tx, tx_set.wireguard.clone(), &mut resp_stream)
                 .await?;
         }
diff --git a/proto b/proto
index 161c6c6776..ec48aca943 160000
--- a/proto
+++ b/proto
@@ -1 +1 @@
-Subproject commit 161c6c677662130924e8bac0c16421b8ed085d33
+Subproject commit ec48aca9438e7cdcb4fcdb01ce6dcb5dac7f8dd3