diff --git a/packages/passport/sdk/src/zkEvm/relayerClient.test.ts b/packages/passport/sdk/src/zkEvm/relayerClient.test.ts
index 780cc82dc8..4a40f79a2d 100644
--- a/packages/passport/sdk/src/zkEvm/relayerClient.test.ts
+++ b/packages/passport/sdk/src/zkEvm/relayerClient.test.ts
@@ -44,6 +44,8 @@ describe('relayerClient', () => {
       const data = '0x123';
 
       (global.fetch as jest.Mock).mockResolvedValue({
+        ok: true,
+        text: () => Promise.resolve(JSON.stringify({ result: transactionHash })),
         json: () => ({
           result: transactionHash,
         }),
@@ -69,6 +71,36 @@ describe('relayerClient', () => {
         }],
       });
     });
+
+    it('throws HTTP error for non-ok response', async () => {
+      const to = '0xd64b0d2d72bb1b3f18046b8a7fc6c9ee6bccd287';
+      const data = '0x123';
+
+      (global.fetch as jest.Mock).mockResolvedValue({
+        ok: false,
+        status: 401,
+        statusText: 'Unauthorized',
+        text: () => Promise.resolve('{"error":"invalid_token"}'),
+      });
+
+      await expect(relayerClient.ethSendTransaction(to, data)).rejects.toThrow(
+        'Relayer HTTP error: 401. Content: "{"error":"invalid_token"}"',
+      );
+    });
+
+    it('throws JSON parse error for invalid response', async () => {
+      const to = '0xd64b0d2d72bb1b3f18046b8a7fc6c9ee6bccd287';
+      const data = '0x123';
+
+      (global.fetch as jest.Mock).mockResolvedValue({
+        ok: true,
+        text: () => Promise.resolve('invalid json'),
+      });
+
+      await expect(relayerClient.ethSendTransaction(to, data)).rejects.toThrow(
+        'Relayer JSON parse error: Unexpected token \'i\', "invalid json" is not valid JSON. Content: "invalid json"',
+      );
+    });
   });
 
   describe('imGetTransactionByHash', () => {
@@ -82,6 +114,8 @@ describe('relayerClient', () => {
       };
 
       (global.fetch as jest.Mock).mockResolvedValue({
+        ok: true,
+        text: () => Promise.resolve(JSON.stringify({ result: relayerTransaction })),
         json: () => ({
           result: relayerTransaction,
         }),
@@ -118,6 +152,8 @@ describe('relayerClient', () => {
       }];
 
       (global.fetch as jest.Mock).mockResolvedValue({
+        ok: true,
+        text: () => Promise.resolve(JSON.stringify({ result: feeOptions })),
         json: () => ({
           result: feeOptions,
         }),
@@ -152,6 +188,8 @@ describe('relayerClient', () => {
       const relayerSignature = '0x123';
 
       (global.fetch as jest.Mock).mockResolvedValue({
+        ok: true,
+        text: () => Promise.resolve(JSON.stringify({ result: relayerSignature })),
         json: () => ({
           result: relayerSignature,
         }),
@@ -186,6 +224,8 @@ describe('relayerClient', () => {
       const relayerSignature = '0x123';
 
       (global.fetch as jest.Mock).mockResolvedValue({
+        ok: true,
+        text: () => Promise.resolve(JSON.stringify({ result: relayerSignature })),
         json: () => ({
           result: relayerSignature,
         }),
diff --git a/packages/passport/sdk/src/zkEvm/relayerClient.ts b/packages/passport/sdk/src/zkEvm/relayerClient.ts
index ddbe226d66..1eaae5a077 100644
--- a/packages/passport/sdk/src/zkEvm/relayerClient.ts
+++ b/packages/passport/sdk/src/zkEvm/relayerClient.ts
@@ -102,6 +102,12 @@ export class RelayerClient {
     this.authManager = authManager;
   }
 
+  private static getResponsePreview(text: string): string {
+    return text.length > 100
+      ? `${text.substring(0, 50)}...${text.substring(text.length - 50)}`
+      : text;
+  }
+
   private async postToRelayer<T>(request: RelayerTransactionRequest): Promise<T> {
     const body: RelayerTransactionRequest & JsonRpc = {
       id: 1,
@@ -120,9 +126,19 @@ export class RelayerClient {
       body: JSON.stringify(body),
     });
 
-    const jsonResponse = await response.json();
-    if (jsonResponse.error) {
-      throw jsonResponse.error;
+    if (!response.ok) {
+      const responseText = await response.text();
+      const preview = RelayerClient.getResponsePreview(responseText);
+      throw new Error(`Relayer HTTP error: ${response.status}. Content: "${preview}"`);
+    }
+
+    const responseText = await response.text();
+    let jsonResponse;
+    try {
+      jsonResponse = JSON.parse(responseText);
+    } catch (parseError) {
+      const preview = RelayerClient.getResponsePreview(responseText);
+      throw new Error(`Relayer JSON parse error: ${parseError instanceof Error ? parseError.message : 'Unknown error'}. Content: "${preview}"`);
     }
 
     return jsonResponse;