diff --git a/packages/browser-tests/README.md b/packages/browser-tests/README.md
index e3f30fbc80..bf329bdc65 100644
--- a/packages/browser-tests/README.md
+++ b/packages/browser-tests/README.md
@@ -65,7 +65,21 @@ The server exposes the following HTTP endpoints:
 
 ### Examples
 
-#### Send a Message
+#### Send a Message (Auto-sharding)
+```bash
+curl -X POST http://localhost:8080/lightpush/v3/message \
+  -H "Content-Type: application/json" \
+  -d '{
+    "pubsubTopic": "",
+    "message": {
+      "contentTopic": "/test/1/example/proto",
+      "payload": "SGVsbG8gV2FrdQ==",
+      "version": 1
+    }
+  }'
+```
+
+#### Send a Message (Explicit pubsub topic)
 ```bash
 curl -X POST http://localhost:8080/lightpush/v3/message \
   -H "Content-Type: application/json" \
diff --git a/packages/browser-tests/src/routes/waku.ts b/packages/browser-tests/src/routes/waku.ts
index 39fd6040ea..9e39d254af 100644
--- a/packages/browser-tests/src/routes/waku.ts
+++ b/packages/browser-tests/src/routes/waku.ts
@@ -42,12 +42,13 @@ router.get("/waku/v1/peer-info", createEndpointHandler({
 
 router.post("/lightpush/v3/message", createEndpointHandler({
   methodName: "pushMessageV3",
-  validateInput: (body: any): [string, string] => {
+  validateInput: (body: any): [string, string, string] => {
     const validatedRequest = validators.requireLightpushV3(body);
 
     return [
       validatedRequest.message.contentTopic,
       validatedRequest.message.payload,
+      validatedRequest.pubsubTopic,
     ];
   },
   handleError: errorHandlers.lightpushError,
diff --git a/packages/browser-tests/src/server.ts b/packages/browser-tests/src/server.ts
index 21f06f6ceb..5a76006ec1 100644
--- a/packages/browser-tests/src/server.ts
+++ b/packages/browser-tests/src/server.ts
@@ -145,8 +145,6 @@ async function startServer(port: number = 3000): Promise<void> {
     }
   } catch (error: any) {
     console.error("Error starting server:", error);
-    // Don't exit the process, just log the error
-    // The server might still be partially functional
   }
 }
 
diff --git a/packages/browser-tests/src/utils/endpoint-handler.ts b/packages/browser-tests/src/utils/endpoint-handler.ts
index fa13ed71bf..3b6395bf05 100644
--- a/packages/browser-tests/src/utils/endpoint-handler.ts
+++ b/packages/browser-tests/src/utils/endpoint-handler.ts
@@ -118,8 +118,8 @@ export function createEndpointHandler<TInput = any, TOutput = any>(
 
 export const validators = {
   requireLightpushV3: (body: any): LightpushV3Request => {
-    if (!body.pubsubTopic || typeof body.pubsubTopic !== "string") {
-      throw new Error("pubsubTopic is required and must be a string");
+    if (body.pubsubTopic !== undefined && typeof body.pubsubTopic !== "string") {
+      throw new Error("pubsubTopic must be a string if provided");
     }
     if (!body.message || typeof body.message !== "object") {
       throw new Error("message is required and must be an object");
@@ -135,7 +135,7 @@ export const validators = {
     }
 
     return {
-      pubsubTopic: body.pubsubTopic,
+      pubsubTopic: body.pubsubTopic || "",
       message: {
         payload: body.message.payload,
         contentTopic: body.message.contentTopic,
diff --git a/packages/browser-tests/web/index.ts b/packages/browser-tests/web/index.ts
index 0c8f46f26d..6c8569ab48 100644
--- a/packages/browser-tests/web/index.ts
+++ b/packages/browser-tests/web/index.ts
@@ -64,7 +64,6 @@ export class WakuHeadless {
   enrBootstrap: string | null;
   constructor(networkConfig?: Partial<NetworkConfig>, lightpushNode?: string, enrBootstrap?: string) {
     this.waku = null as unknown as LightNode;
-    // Use provided config or defaults
     this.networkConfig = this.buildNetworkConfig(networkConfig);
     this.lightpushNode = lightpushNode || null;
     this.enrBootstrap = enrBootstrap || null;
@@ -107,7 +106,6 @@ export class WakuHeadless {
   private buildNetworkConfig(providedConfig?: Partial<NetworkConfig>): NetworkConfig {
     const clusterId = providedConfig?.clusterId ?? 1;
     
-    // Check if static sharding is requested through environment or config
     const staticShards = (providedConfig as any)?.shards;
     if (staticShards && Array.isArray(staticShards) && staticShards.length > 0) {
       return {
@@ -116,7 +114,6 @@ export class WakuHeadless {
       } as NetworkConfig;
     }
     
-    // Default to auto-sharding
     const numShardsInCluster = (providedConfig as any)?.numShardsInCluster ?? 8;
     return {
       clusterId,
@@ -133,11 +130,8 @@ export class WakuHeadless {
       throw new Error("Waku node not started");
     }
 
-    // Ensure payload is properly formatted
     let processedPayload: Uint8Array;
-    // If it's a string, try to decode as base64 first
     try {
-      // Use TextDecoder to decode base64 (browser-compatible)
       const binaryString = atob(payload);
       const bytes = new Uint8Array(binaryString.length);
       for (let i = 0; i < binaryString.length; i++) {
@@ -145,7 +139,6 @@ export class WakuHeadless {
       }
       processedPayload = bytes;
     } catch (e) {
-      // If base64 decoding fails, encode as UTF-8
       processedPayload = new TextEncoder().encode(payload);
     }
 
@@ -163,7 +156,6 @@ export class WakuHeadless {
         timestamp: new Date(),
       });
 
-      // Convert to serializable format for cross-context communication
       const serializableResult = makeSerializable(result);
 
       return serializableResult;
@@ -178,16 +170,14 @@ export class WakuHeadless {
   async pushMessageV3(
     contentTopic: string,
     payload: string,
+    pubsubTopic: string,
   ): Promise<SerializableSDKProtocolResult> {
     if (!this.waku) {
       throw new Error("Waku node not started");
     }
 
-    // Ensure payload is properly formatted
     let processedPayload: Uint8Array;
-    // If it's a string, try to decode as base64 first
     try {
-      // Use TextDecoder to decode base64 (browser-compatible)
       const binaryString = atob(payload);
       const bytes = new Uint8Array(binaryString.length);
       for (let i = 0; i < binaryString.length; i++) {
@@ -195,7 +185,6 @@ export class WakuHeadless {
       }
       processedPayload = bytes;
     } catch (e) {
-      // If base64 decoding fails, encode as UTF-8
       processedPayload = new TextEncoder().encode(payload);
     }
 
@@ -207,6 +196,10 @@ export class WakuHeadless {
 
 
       const encoder = this.waku.createEncoder({ contentTopic });
+      
+      if (pubsubTopic && pubsubTopic !== encoder.pubsubTopic) {
+        console.warn(`Explicit pubsubTopic ${pubsubTopic} provided, but auto-sharding determined ${encoder.pubsubTopic}. Using auto-sharding.`);
+      }
 
       let result;
       if (this.lightpushNode) {
@@ -234,7 +227,6 @@ export class WakuHeadless {
         });
       }
 
-      // Convert to serializable format for cross-context communication
       const serializableResult = makeSerializable(result);
 
       return serializableResult;
@@ -260,7 +252,6 @@ export class WakuHeadless {
       await this.waku.waitForPeers(protocols, timeoutMs);
       const elapsed = Date.now() - startTime;
 
-      // Log connected peers
       const peers = this.waku.libp2p.getPeers();
 
       return {