diff --git a/dist/index.d.ts b/dist/index.d.ts
index 222dfc3..1bab2a2 100644
--- a/dist/index.d.ts
+++ b/dist/index.d.ts
@@ -1,6 +1,7 @@
 export declare class TetherClient {
     private websocketHandler;
     private subscribedQueries;
+    private pendingMutations;
     connect: (url: string) => void;
     disconnect: () => void;
     subscribe: (queryName: string, params: any, callback: (data: any) => void) => void;
diff --git a/dist/index.js b/dist/index.js
index fbd2c96..bd5313c 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -2,6 +2,7 @@ import { WebSocketHandler } from './utils/websocket.js';
 export class TetherClient {
     websocketHandler = new WebSocketHandler();
     subscribedQueries = new Map();
+    pendingMutations = new Map();
     connect = (url) => {
         this.websocketHandler.startConnection(url);
         this.websocketHandler.onQuery = (location, data) => {
@@ -10,6 +11,15 @@ export class TetherClient {
                 callback?.(data);
             }
         };
+        this.websocketHandler.onMutation = (incoming_id, data) => {
+            const pending = this.pendingMutations.get(incoming_id);
+            if (!pending) {
+                return;
+            }
+            clearTimeout(pending.timeoutId);
+            this.pendingMutations.delete(incoming_id);
+            pending.resolve(data);
+        };
         this.websocketHandler.onOpen = () => {
             this.subscribedQueries.forEach(({ params }, queryName) => {
                 this.websocketHandler.send(JSON.stringify({
@@ -40,22 +50,19 @@ export class TetherClient {
     };
     sendMutation = (mutationName, params) => {
         const mutation_id = crypto.randomUUID();
+        const promise = new Promise((resolve, reject) => {
+            const timeoutId = setTimeout(() => {
+                this.pendingMutations.delete(mutation_id);
+                reject(new Error('Mutation timeout'));
+            }, 10000);
+            this.pendingMutations.set(mutation_id, { resolve, reject, timeoutId });
+        });
         this.websocketHandler.send(JSON.stringify({
             type: 'mutation',
             location: mutationName,
             params: params,
             mutation_id: mutation_id
         }));
-        return new Promise((resolve, reject) => {
-            const timeoutId = setTimeout(() => {
-                reject(new Error('Mutation timeout'));
-            }, 10000);
-            this.websocketHandler.onMutation = (incoming_id, data) => {
-                if (incoming_id === mutation_id) {
-                    clearTimeout(timeoutId);
-                    resolve(data);
-                }
-            };
-        });
+        return promise;
     };
 }
diff --git a/dist/utils/websocket.js b/dist/utils/websocket.js
index 6a89d86..6dad246 100644
--- a/dist/utils/websocket.js
+++ b/dist/utils/websocket.js
@@ -23,7 +23,14 @@ export class WebSocketHandler {
             this.reconnectAttempts = 0;
         };
         ws.onmessage = (event) => {
-            const data = JSON.parse(String(event.data));
+            let data;
+            try {
+                data = JSON.parse(String(event.data));
+            }
+            catch (e) {
+                console.error('Tether: invalid JSON message', event.data, e);
+                return;
+            }
             if (data.type === 'query') {
                 this.onQuery(data.location, data.data);
             }
@@ -34,8 +41,8 @@ export class WebSocketHandler {
                 console.error(data.error);
             }
         };
-        ws.onclose = () => {
-            console.log('Disconnected from Tether');
+        ws.onclose = (event) => {
+            console.log('Disconnected from Tether', 'code:', event.code, 'reason:', event.reason || '(none)', 'wasClean:', event.wasClean);
             this.attemptReconnect();
         };
     };
diff --git a/src/index.ts b/src/index.ts
index 8c7a090..e5a110a 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,7 +1,14 @@
 import { WebSocketHandler } from './utils/websocket.js';
+type PendingMutation = {
+    resolve: (value: unknown) => void;
+    reject: (reason: Error) => void;
+    timeoutId: ReturnType<typeof setTimeout>;
+};
+
 export class TetherClient {
     private websocketHandler: WebSocketHandler = new WebSocketHandler();
     private subscribedQueries = new Map<string, { callback: (data: any) => void, params: any }>();
+    private pendingMutations = new Map<string, PendingMutation>();
 
     connect = (url: string) => {
         this.websocketHandler.startConnection(url);
@@ -11,6 +18,15 @@ export class TetherClient {
                 callback?.(data);
             }
         };
+        this.websocketHandler.onMutation = (incoming_id, data) => {
+            const pending = this.pendingMutations.get(incoming_id);
+            if (!pending) {
+                return;
+            }
+            clearTimeout(pending.timeoutId);
+            this.pendingMutations.delete(incoming_id);
+            pending.resolve(data);
+        };
         this.websocketHandler.onOpen = () => {
             this.subscribedQueries.forEach(({ params }, queryName) => {
                 this.websocketHandler.send(JSON.stringify({
@@ -45,22 +61,19 @@ export class TetherClient {
     
     sendMutation = (mutationName: string, params: any) => {
         const mutation_id = crypto.randomUUID();
+        const promise = new Promise((resolve, reject) => {
+            const timeoutId = setTimeout(() => {
+                this.pendingMutations.delete(mutation_id);
+                reject(new Error('Mutation timeout'));
+            }, 10000);
+            this.pendingMutations.set(mutation_id, { resolve, reject, timeoutId });
+        });
         this.websocketHandler.send(JSON.stringify({
             type: 'mutation',
             location: mutationName,
             params: params,
             mutation_id: mutation_id
         }));
-        return new Promise((resolve, reject) => {
-            const timeoutId = setTimeout(() => {
-                reject(new Error('Mutation timeout'));
-            }, 10000);
-            this.websocketHandler.onMutation = (incoming_id: string, data: any) => {
-                if (incoming_id === mutation_id) {
-                    clearTimeout(timeoutId);
-                    resolve(data);
-                }
-            };
-        });
+        return promise;
     };
 }
\ No newline at end of file
diff --git a/src/utils/websocket.ts b/src/utils/websocket.ts
index 12e3fe9..776f7ea 100644
--- a/src/utils/websocket.ts
+++ b/src/utils/websocket.ts
@@ -25,13 +25,19 @@ export class WebSocketHandler {
         };
 
         ws.onmessage = (event: MessageEvent) => {
-            const data = JSON.parse(String(event.data)) as {
+            let data: {
                 type: string;
                 location?: string;
                 data?: unknown;
                 error?: string;
                 mutation_id?: string;
             };
+            try {
+                data = JSON.parse(String(event.data));
+            } catch (e) {
+                console.error('Tether: invalid JSON message', event.data, e);
+                return;
+            }
             if (data.type === 'query') {
                 this.onQuery(data.location, data.data);
             } else if (data.type === 'mutation') {
@@ -41,8 +47,16 @@ export class WebSocketHandler {
             }
         };
 
-        ws.onclose = () => {
-            console.log('Disconnected from Tether');
+        ws.onclose = (event: CloseEvent) => {
+            console.log(
+                'Disconnected from Tether',
+                'code:',
+                event.code,
+                'reason:',
+                event.reason || '(none)',
+                'wasClean:',
+                event.wasClean
+            );
             this.attemptReconnect();
         };
     };