diff --git a/clients/macos/vellum-assistant/App/AppDelegate+ConnectionSetup.swift b/clients/macos/vellum-assistant/App/AppDelegate+ConnectionSetup.swift
index 38e45bf22f9..915ab11c841 100644
--- a/clients/macos/vellum-assistant/App/AppDelegate+ConnectionSetup.swift
+++ b/clients/macos/vellum-assistant/App/AppDelegate+ConnectionSetup.swift
@@ -365,6 +365,15 @@ extension AppDelegate {
                     self.featureFlagStore.reloadFromGateway()
                 // Host tool execution — run locally and post results back
                 case .hostBashRequest(let msg):
+                    // Accept if this conversation is locally owned, OR if the request
+                    // is explicitly targeted at this client (cross-client proxy routing).
+                    let localClientId = DeviceIdStore.getOrCreate()
+                    let isLocalConversation = self.mainWindow?.conversationManager
+                        .conversations.contains(where: { $0.conversationId == msg.conversationId }) ?? false
+                    let isTargeted = msg.targetClientId == localClientId
+                    guard isLocalConversation || isTargeted else {
+                        break
+                    }
                     HostToolExecutor.executeHostBashRequest(msg)
                 case .hostFileRequest(let msg):
                     HostToolExecutor.executeHostFileRequest(msg)
diff --git a/clients/shared/Network/MessageTypes.swift b/clients/shared/Network/MessageTypes.swift
index 7d31d00b839..cd400d20f65 100644
--- a/clients/shared/Network/MessageTypes.swift
+++ b/clients/shared/Network/MessageTypes.swift
@@ -1538,6 +1538,9 @@ public struct HostBashRequest: Decodable, Sendable {
     public let timeoutSeconds: Double?
     /// Extra environment variables to inject into the subprocess (e.g. VELLUM_UNTRUSTED_SHELL).
     public let env: [String: String]?
+    /// When set, this request is targeted at a specific client ID. Non-nil only for
+    /// cross-client proxy requests routed through HostBashProxy.
+    public let targetClientId: String?
 
     private enum CodingKeys: String, CodingKey {
         case type
@@ -1547,6 +1550,7 @@ public struct HostBashRequest: Decodable, Sendable {
         case workingDir = "working_dir"
         case timeoutSeconds = "timeout_seconds"
         case env
+        case targetClientId
     }
 }