diff --git a/CHANGELOG.md b/CHANGELOG.md
index b355bd5..01a094b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## [2.0.3] - 2025-08-22
+
+### Added Changes
+
+- `chainId` is mandatory in the `transaction()` method.
+- For `send` and `estimate`, the `etherspotModularSdk` is initialized using the transaction's `chainId` rather than the provider's `chainId`.
 ## [2.0.2] - 2025-07-24
 
 ### Added Changes
diff --git a/__tests__/EtherspotTransactionKit.test.ts b/__tests__/EtherspotTransactionKit.test.ts
index 137e854..16356c0 100644
--- a/__tests__/EtherspotTransactionKit.test.ts
+++ b/__tests__/EtherspotTransactionKit.test.ts
@@ -193,6 +193,7 @@ describe('EtherspotTransactionKit', () => {
 
     it('should use default values for optional parameters', () => {
       const txParams = {
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
       };
 
@@ -206,7 +207,7 @@ describe('EtherspotTransactionKit', () => {
 
     it('should throw error for missing to address', () => {
       expect(() => {
-        transactionKit.transaction({ to: '' });
+        transactionKit.transaction({ chainId: 1, to: '' });
       }).toThrow('transaction(): to is required.');
     });
 
@@ -214,7 +215,7 @@ describe('EtherspotTransactionKit', () => {
       (isAddress as unknown as jest.Mock).mockReturnValue(false);
 
       expect(() => {
-        transactionKit.transaction({ to: 'invalid-address' });
+        transactionKit.transaction({ chainId: 1, to: 'invalid-address' });
       }).toThrow(`transaction(): 'invalid-address' is not a valid address.`);
     });
 
@@ -230,6 +231,7 @@ describe('EtherspotTransactionKit', () => {
     it('should throw error for invalid value', () => {
       expect(() => {
         transactionKit.transaction({
+          chainId: 1,
           to: '0x1234567890123456789012345678901234567890',
           value: 'invalid',
         });
@@ -241,6 +243,7 @@ describe('EtherspotTransactionKit', () => {
     it('should throw error for negative value', () => {
       expect(() => {
         transactionKit.transaction({
+          chainId: 1,
           to: '0x1234567890123456789012345678901234567890',
           value: '-1',
         });
@@ -251,6 +254,7 @@ describe('EtherspotTransactionKit', () => {
 
     it('should accept bigint value', () => {
       const txParams = {
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
         value: BigInt(1000),
       };
@@ -266,6 +270,7 @@ describe('EtherspotTransactionKit', () => {
   describe('name', () => {
     beforeEach(() => {
       transactionKit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
       });
     });
@@ -319,6 +324,7 @@ describe('EtherspotTransactionKit', () => {
   describe('remove', () => {
     it('should remove named transaction', () => {
       transactionKit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
       });
       transactionKit.name({ transactionName: 'test' });
@@ -341,6 +347,7 @@ describe('EtherspotTransactionKit', () => {
 
     it('should throw error if transaction not named', () => {
       transactionKit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
       });
 
@@ -355,6 +362,7 @@ describe('EtherspotTransactionKit', () => {
   describe('update', () => {
     beforeEach(() => {
       transactionKit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
       });
       transactionKit.name({ transactionName: 'test' });
@@ -380,6 +388,7 @@ describe('EtherspotTransactionKit', () => {
   describe('estimate', () => {
     beforeEach(() => {
       transactionKit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
         value: '1000000000000000000',
         data: '0x1234',
@@ -504,6 +513,7 @@ describe('EtherspotTransactionKit', () => {
     it('should allow transaction with value = 0 and data = 0x', async () => {
       const kit = new EtherspotTransactionKit(mockConfig);
       kit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
         value: '0',
         data: '0x',
@@ -547,6 +557,7 @@ describe('EtherspotTransactionKit', () => {
   describe('send', () => {
     beforeEach(() => {
       transactionKit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
         value: '1000000000000000000',
         data: '0x1234',
@@ -658,6 +669,7 @@ describe('EtherspotTransactionKit', () => {
 
     it('should allow sending transaction with value = 0 and data = 0x', async () => {
       transactionKit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
         value: '0',
         data: '0x',
@@ -743,6 +755,7 @@ describe('EtherspotTransactionKit', () => {
 
     it('should return state with transaction', () => {
       transactionKit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
         value: '1000000000000000000',
       });
@@ -779,6 +792,7 @@ describe('EtherspotTransactionKit', () => {
       expect(() => {
         debugKit.setDebugMode(true);
         debugKit.transaction({
+          chainId: 1,
           to: '0x1234567890123456789012345678901234567890',
         });
         debugKit.name({ transactionName: 'debug-tx' });
@@ -828,6 +842,7 @@ describe('EtherspotTransactionKit', () => {
     it('should reset all state', () => {
       // Set up some state
       transactionKit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
       });
       transactionKit.name({ transactionName: 'test' });
@@ -870,6 +885,7 @@ describe('EtherspotTransactionKit', () => {
   describe('State management during operations', () => {
     beforeEach(() => {
       transactionKit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
         value: '1000000000000000000',
       });
@@ -929,23 +945,24 @@ describe('EtherspotTransactionKit', () => {
   });
 
   describe('Provider integration', () => {
-    it('should handle provider chain ID changes', () => {
+    it('should use explicit chainId from transaction call', () => {
       mockProvider.getChainId.mockReturnValue(5);
 
       transactionKit.transaction({
+        chainId: 1,
         to: '0x1234567890123456789012345678901234567890',
       });
 
       const state = transactionKit.getState();
       expect(state.workingTransaction?.chainId).toBe(1);
 
-      // Test with no explicit chainId
       transactionKit.transaction({
+        chainId: 137,
         to: '0x1234567890123456789012345678901234567890',
         value: '1',
       });
       const state2 = transactionKit.getState();
-      expect(state2.workingTransaction?.chainId).toBe(1); // Should use default
+      expect(state2.workingTransaction?.chainId).toBe(137);
     });
 
     it('should handle SDK instance errors gracefully', async () => {
@@ -972,12 +989,14 @@ describe('Batch operations', () => {
     mockSdk.send.mockReset();
     mockSdk.totalGasEstimated.mockReset();
     transactionKit.transaction({
+      chainId: 1,
       to: '0x1111111111111111111111111111111111111111',
       value: '1000000000000000000',
     });
     transactionKit.name({ transactionName: 'tx1' });
     transactionKit.addToBatch({ batchName: 'batch1' });
     transactionKit.transaction({
+      chainId: 1,
       to: '0x2222222222222222222222222222222222222222',
       value: '2000000000000000000',
     });
diff --git a/example/package-lock.json b/example/package-lock.json
index c7fdadf..ff5a37c 100644
--- a/example/package-lock.json
+++ b/example/package-lock.json
@@ -29,11 +29,11 @@
     },
     "..": {
       "name": "@etherspot/transaction-kit",
-      "version": "2.0.0",
+      "version": "2.0.2",
       "license": "MIT",
       "dependencies": {
         "@etherspot/eip1271-verification-util": "0.1.2",
-        "@etherspot/modular-sdk": "6.1.0",
+        "@etherspot/modular-sdk": "6.1.1",
         "buffer": "6.0.3",
         "lodash": "4.17.21",
         "viem": "2.21.54"
diff --git a/example/src/App.tsx b/example/src/App.tsx
index 4d506f6..f36b2de 100644
--- a/example/src/App.tsx
+++ b/example/src/App.tsx
@@ -39,6 +39,7 @@ const App = () => {
       action: async (logAndUpdateState: (msg: string) => void) => {
         try {
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000dead',
             value: '1000000000000000000',
           });
@@ -57,6 +58,7 @@ const App = () => {
             transactionName: 'tx1',
           }) as INamedTransaction;
           named.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000beef',
             value: '2000000000000000000',
           });
@@ -86,6 +88,7 @@ const App = () => {
       action: async (logAndUpdateState: (msg: string) => void) => {
         try {
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000cafe',
             value: '3000000000000000000',
           });
@@ -104,6 +107,7 @@ const App = () => {
       action: async (logAndUpdateState: (msg: string) => void) => {
         try {
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000babe',
             value: '4000000000000000000',
           });
@@ -252,6 +256,7 @@ const App = () => {
       action: async (logAndUpdateState: (msg: string) => void) => {
         try {
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000f00d',
             value: '5000000000000000000',
           });
@@ -272,6 +277,7 @@ const App = () => {
         try {
           // Ensure tx3 is in batch1
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000babe',
             value: '4000000000000000000',
           });
@@ -295,6 +301,7 @@ const App = () => {
         try {
           // Add tx5 to batch2
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000c0de',
             value: '6000000000000000000',
           });
@@ -304,6 +311,7 @@ const App = () => {
           named.addToBatch({ batchName: 'batch2' });
           // Add tx6 to batch2
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000c0fe',
             value: '7000000000000000000',
           });
@@ -327,6 +335,7 @@ const App = () => {
         try {
           // Ensure tx3 is in batch1
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000babe',
             value: '4000000000000000000',
           });
@@ -336,6 +345,7 @@ const App = () => {
           named.addToBatch({ batchName: 'batch1' });
           // Now update tx3 in batch1
           named.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000feed',
             value: '8880000000000000000',
           });
@@ -353,6 +363,7 @@ const App = () => {
       action: async (logAndUpdateState: (msg: string) => void) => {
         try {
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000aabb',
             value: '1000000000000000000',
           });
@@ -389,6 +400,7 @@ const App = () => {
       action: async (logAndUpdateState: (msg: string) => void) => {
         try {
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000cafe',
             value: '123',
           });
@@ -423,7 +435,7 @@ const App = () => {
       label: 'Add Transaction with Invalid Address',
       action: async (logAndUpdateState: (msg: string) => void) => {
         try {
-          kit.transaction({ to: 'not-an-address', value: '1' });
+          kit.transaction({ chainId: 137, to: 'not-an-address', value: '1' });
           logAndUpdateState('Should not see this.');
         } catch (e) {
           logAndUpdateState('Error: ' + (e as Error).message);
@@ -435,6 +447,7 @@ const App = () => {
       action: async (logAndUpdateState: (msg: string) => void) => {
         try {
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000dead',
             value: '-1',
           });
@@ -474,6 +487,7 @@ const App = () => {
         try {
           // Create empty batchD by adding and removing a tx
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000dede',
             value: '1',
           });
@@ -512,6 +526,7 @@ const App = () => {
         try {
           // Add tx10 to batchE
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000eeee',
             value: '1',
           });
@@ -533,6 +548,7 @@ const App = () => {
       action: async (logAndUpdateState: (msg: string) => void) => {
         try {
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000f0f0',
             value: '1',
           });
@@ -548,6 +564,7 @@ const App = () => {
       action: async (logAndUpdateState: (msg: string) => void) => {
         try {
           kit.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000f1f1',
             value: '1',
           });
@@ -556,6 +573,7 @@ const App = () => {
           }) as INamedTransaction;
           named.addToBatch({ batchName: 'batchF' });
           named.transaction({
+            chainId: 137,
             to: '0x000000000000000000000000000000000000f2f2',
             value: '2',
           });
diff --git a/lib/TransactionKit.ts b/lib/TransactionKit.ts
index b8ed22a..3f7aee0 100644
--- a/lib/TransactionKit.ts
+++ b/lib/TransactionKit.ts
@@ -125,12 +125,12 @@ export class EtherspotTransactionKit implements IInitial {
 
     try {
       // Get SDK instance for the chain
-      const etherspotModulaSdk =
+      const etherspotModularSdk =
         await this.etherspotProvider.getSdk(walletAddressChainId);
 
       let walletAddress: string | undefined;
       try {
-        walletAddress = await etherspotModulaSdk.getCounterFactualAddress();
+        walletAddress = await etherspotModularSdk.getCounterFactualAddress();
         log(
           `Got wallet address from getCounterFactualAddress for chain ${walletAddressChainId}`,
           walletAddress,
@@ -173,11 +173,21 @@ export class EtherspotTransactionKit implements IInitial {
    * - The transaction context is stored in the instance until it is named or added to a batch.
    */
   transaction({
-    chainId = 1,
+    chainId,
     to,
     value = '0',
     data = '0x',
   }: TransactionParams): ITransaction {
+    if (chainId === undefined || chainId === null) {
+      this.throwError(
+        'transaction(): chainId is required. Please specify the target network explicitly.'
+      );
+    }
+
+    if (typeof chainId !== 'number' || !Number.isInteger(chainId)) {
+      this.throwError('transaction(): chainId must be a valid number.');
+    }
+
     if (!to) {
       this.throwError('transaction(): to is required.');
     }
@@ -186,10 +196,6 @@ export class EtherspotTransactionKit implements IInitial {
       this.throwError(`transaction(): '${to}' is not a valid address.`);
     }
 
-    if (typeof chainId !== 'number' || !Number.isInteger(chainId)) {
-      this.throwError('transaction(): chainId must be a valid number.');
-    }
-
     let parsedValue: bigint;
     try {
       parsedValue = typeof value === 'bigint' ? value : BigInt(value);
@@ -618,7 +624,7 @@ export class EtherspotTransactionKit implements IInitial {
       const result = {
         to: this.workingTransaction?.to || '',
         chainId:
-          this.workingTransaction?.chainId ||
+          this.workingTransaction?.chainId ??
           this.etherspotProvider.getChainId(),
         errorMessage,
         errorType,
@@ -653,11 +659,12 @@ export class EtherspotTransactionKit implements IInitial {
       // Only proceed if value and data are defined
       // Get fresh SDK instance to avoid state pollution
       log('estimate(): Getting SDK...', undefined, this.debugMode);
-      const etherspotModulaSdk = await this.etherspotProvider.getSdk(
-        this.etherspotProvider.getChainId(),
+      const transactionChainId = this.workingTransaction!.chainId;
+      const etherspotModularSdk = await this.etherspotProvider.getSdk(
+        transactionChainId,
         true
       );
-      log('estimate(): Got SDK:', etherspotModulaSdk, this.debugMode);
+      log('estimate(): Got SDK:', etherspotModularSdk, this.debugMode);
 
       // Clear any existing operations
       log(
@@ -665,7 +672,7 @@ export class EtherspotTransactionKit implements IInitial {
         undefined,
         this.debugMode
       );
-      await etherspotModulaSdk.clearUserOpsFromBatch();
+      await etherspotModularSdk.clearUserOpsFromBatch();
       log(
         'estimate(): Cleared user ops from batch.',
         undefined,
@@ -678,7 +685,7 @@ export class EtherspotTransactionKit implements IInitial {
         this.workingTransaction,
         this.debugMode
       );
-      await etherspotModulaSdk.addUserOpsToBatch({
+      await etherspotModularSdk.addUserOpsToBatch({
         to: this.workingTransaction.to || '',
         value: this.workingTransaction.value.toString(),
         data: this.workingTransaction.data,
@@ -687,7 +694,7 @@ export class EtherspotTransactionKit implements IInitial {
 
       // Estimate the transaction
       log('estimate(): Estimating user op...', undefined, this.debugMode);
-      const userOp = await etherspotModulaSdk.estimate({
+      const userOp = await etherspotModularSdk.estimate({
         paymasterDetails,
         gasDetails,
         callGasLimit,
@@ -696,7 +703,7 @@ export class EtherspotTransactionKit implements IInitial {
 
       // Calculate total gas cost
       log('estimate(): Calculating total gas...', undefined, this.debugMode);
-      const totalGas = await etherspotModulaSdk.totalGasEstimated(userOp);
+      const totalGas = await etherspotModularSdk.totalGasEstimated(userOp);
       log('estimate(): Got totalGas:', totalGas, this.debugMode);
       const totalGasBigInt = BigInt(totalGas.toString());
       const maxFeePerGasBigInt = BigInt(userOp.maxFeePerGas.toString());
@@ -721,9 +728,7 @@ export class EtherspotTransactionKit implements IInitial {
         to: this.workingTransaction?.to || '',
         value: this.workingTransaction?.value?.toString(),
         data: this.workingTransaction?.data,
-        chainId:
-          this.workingTransaction?.chainId ||
-          this.etherspotProvider.getChainId(),
+        chainId: this.workingTransaction!.chainId,
         cost,
         userOp,
         isEstimatedSuccessfully: true,
@@ -846,7 +851,7 @@ export class EtherspotTransactionKit implements IInitial {
       const result = {
         to: this.workingTransaction?.to || '',
         chainId:
-          this.workingTransaction?.chainId ||
+          this.workingTransaction?.chainId ??
           this.etherspotProvider.getChainId(),
         errorMessage,
         errorType,
@@ -861,15 +866,16 @@ export class EtherspotTransactionKit implements IInitial {
     try {
       // Get fresh SDK instance to avoid state pollution
       log('send(): Getting SDK...', undefined, this.debugMode);
-      const etherspotModulaSdk = await this.etherspotProvider.getSdk(
-        this.etherspotProvider.getChainId(),
+      const transactionChainId = this.workingTransaction!.chainId;
+      const etherspotModularSdk = await this.etherspotProvider.getSdk(
+        transactionChainId,
         true
       );
-      log('send(): Got SDK:', etherspotModulaSdk, this.debugMode);
+      log('send(): Got SDK:', etherspotModularSdk, this.debugMode);
 
       // Clear any existing operations
       log('send(): Clearing user ops from batch...', undefined, this.debugMode);
-      await etherspotModulaSdk.clearUserOpsFromBatch();
+      await etherspotModularSdk.clearUserOpsFromBatch();
       log('send(): Cleared user ops from batch.', undefined, this.debugMode);
 
       // Add the transaction to the userOp Batch
@@ -878,7 +884,7 @@ export class EtherspotTransactionKit implements IInitial {
         this.workingTransaction,
         this.debugMode
       );
-      await etherspotModulaSdk.addUserOpsToBatch({
+      await etherspotModularSdk.addUserOpsToBatch({
         to: this.workingTransaction?.to || '',
         value: this.workingTransaction?.value?.toString(),
         data: this.workingTransaction?.data || '0x',
@@ -889,7 +895,7 @@ export class EtherspotTransactionKit implements IInitial {
       let estimatedUserOp;
       try {
         log('send(): Estimating user op...', undefined, this.debugMode);
-        estimatedUserOp = await etherspotModulaSdk.estimate({
+        estimatedUserOp = await etherspotModularSdk.estimate({
           paymasterDetails,
         });
         log('send(): Got estimated userOp:', estimatedUserOp, this.debugMode);
@@ -923,7 +929,7 @@ export class EtherspotTransactionKit implements IInitial {
 
       // Calculate total gas cost (using the final UserOp values)
       log('send(): Calculating total gas...', undefined, this.debugMode);
-      const totalGas = await etherspotModulaSdk.totalGasEstimated(finalUserOp);
+      const totalGas = await etherspotModularSdk.totalGasEstimated(finalUserOp);
       log('send(): Got totalGas:', totalGas, this.debugMode);
       const totalGasBigInt = BigInt(totalGas.toString());
       const maxFeePerGasBigInt = BigInt(finalUserOp.maxFeePerGas.toString());
@@ -945,7 +951,7 @@ export class EtherspotTransactionKit implements IInitial {
       let userOpHash: string;
       try {
         log('send(): Sending userOp...', undefined, this.debugMode);
-        userOpHash = await etherspotModulaSdk.send(finalUserOp);
+        userOpHash = await etherspotModularSdk.send(finalUserOp);
         log('send(): Got userOpHash:', userOpHash, this.debugMode);
       } catch (sendError) {
         const sendErrorMessage = parseEtherspotErrorMessage(
@@ -965,7 +971,7 @@ export class EtherspotTransactionKit implements IInitial {
           value: this.workingTransaction?.value?.toString(),
           data: this.workingTransaction?.data,
           chainId:
-            this.workingTransaction?.chainId ||
+            this.workingTransaction?.chainId ??
             this.etherspotProvider.getChainId(),
           cost,
           userOp: finalUserOp,
@@ -987,6 +993,14 @@ export class EtherspotTransactionKit implements IInitial {
       this.isSending = false;
       this.containsSendingError = false;
 
+      // Save transaction data before clearing state
+      const successResult = {
+        to: this.workingTransaction?.to || '',
+        value: this.workingTransaction?.value?.toString(),
+        data: this.workingTransaction?.data,
+        chainId: this.workingTransaction!.chainId,
+      };
+
       // Remove transaction from state after successful send
       const transactionName = this.selectedTransactionName;
       if (transactionName && this.namedTransactions[transactionName]) {
@@ -1004,12 +1018,7 @@ export class EtherspotTransactionKit implements IInitial {
       this.clearWorkingState();
 
       const result = {
-        to: this.workingTransaction?.to || '',
-        value: this.workingTransaction?.value?.toString(),
-        data: this.workingTransaction?.data,
-        chainId:
-          this.workingTransaction?.chainId ||
-          this.etherspotProvider.getChainId(),
+        ...successResult,
         cost,
         userOp: finalUserOp,
         userOpHash,
@@ -1127,13 +1136,13 @@ export class EtherspotTransactionKit implements IInitial {
             undefined,
             this.debugMode
           );
-          const etherspotModulaSdk = await this.etherspotProvider.getSdk(
+          const etherspotModularSdk = await this.etherspotProvider.getSdk(
             batchChainId,
             true // force new instance
           );
           log(
             `estimateBatches(): Got SDK for batch ${batchName}:`,
-            etherspotModulaSdk,
+            etherspotModularSdk,
             this.debugMode
           );
 
@@ -1143,7 +1152,7 @@ export class EtherspotTransactionKit implements IInitial {
             undefined,
             this.debugMode
           );
-          await etherspotModulaSdk.clearUserOpsFromBatch();
+          await etherspotModularSdk.clearUserOpsFromBatch();
           log(
             `estimateBatches(): Cleared user ops from batch ${batchName}.`,
             undefined,
@@ -1163,7 +1172,7 @@ export class EtherspotTransactionKit implements IInitial {
                 undefined,
                 this.debugMode
               );
-              await etherspotModulaSdk.addUserOpsToBatch({
+              await etherspotModularSdk.addUserOpsToBatch({
                 to: tx.to || '',
                 value: tx.value?.toString(),
                 data: tx.data,
@@ -1187,7 +1196,7 @@ export class EtherspotTransactionKit implements IInitial {
             undefined,
             this.debugMode
           );
-          const userOp = await etherspotModulaSdk.estimate({
+          const userOp = await etherspotModularSdk.estimate({
             paymasterDetails,
           });
           log(
@@ -1202,7 +1211,7 @@ export class EtherspotTransactionKit implements IInitial {
             undefined,
             this.debugMode
           );
-          const totalGas = await etherspotModulaSdk.totalGasEstimated(userOp);
+          const totalGas = await etherspotModularSdk.totalGasEstimated(userOp);
           log(
             `estimateBatches(): Got totalGas for batch ${batchName}:`,
             totalGas,
@@ -1400,13 +1409,13 @@ export class EtherspotTransactionKit implements IInitial {
             undefined,
             this.debugMode
           );
-          const etherspotModulaSdk = await this.etherspotProvider.getSdk(
+          const etherspotModularSdk = await this.etherspotProvider.getSdk(
             batchChainId,
             true // force new instance
           );
           log(
             `sendBatches(): Got SDK for batch ${batchName}:`,
-            etherspotModulaSdk,
+            etherspotModularSdk,
             this.debugMode
           );
 
@@ -1416,7 +1425,7 @@ export class EtherspotTransactionKit implements IInitial {
             undefined,
             this.debugMode
           );
-          await etherspotModulaSdk.clearUserOpsFromBatch();
+          await etherspotModularSdk.clearUserOpsFromBatch();
           log(
             `sendBatches(): Cleared user ops from batch ${batchName}.`,
             undefined,
@@ -1436,7 +1445,7 @@ export class EtherspotTransactionKit implements IInitial {
                 undefined,
                 this.debugMode
               );
-              await etherspotModulaSdk.addUserOpsToBatch({
+              await etherspotModularSdk.addUserOpsToBatch({
                 to: tx.to || '',
                 value: tx.value?.toString(),
                 data: tx.data,
@@ -1462,7 +1471,7 @@ export class EtherspotTransactionKit implements IInitial {
               undefined,
               this.debugMode
             );
-            estimatedUserOp = await etherspotModulaSdk.estimate({
+            estimatedUserOp = await etherspotModularSdk.estimate({
               paymasterDetails,
             });
             log(
@@ -1524,7 +1533,7 @@ export class EtherspotTransactionKit implements IInitial {
             this.debugMode
           );
           const totalGas =
-            await etherspotModulaSdk.totalGasEstimated(finalUserOp);
+            await etherspotModularSdk.totalGasEstimated(finalUserOp);
           log(
             `sendBatches(): Got totalGas for batch ${batchName}:`,
             totalGas,
@@ -1559,7 +1568,7 @@ export class EtherspotTransactionKit implements IInitial {
               undefined,
               this.debugMode
             );
-            userOpHash = await etherspotModulaSdk.send(finalUserOp);
+            userOpHash = await etherspotModularSdk.send(finalUserOp);
             log(
               `sendBatches(): Got userOpHash for batch ${batchName}:`,
               userOpHash,
@@ -1810,7 +1819,7 @@ export class EtherspotTransactionKit implements IInitial {
     timeout: number = 60 * 1000,
     retryInterval: number = 2000
   ): Promise<string | null> {
-    const etherspotModulaSdk = await this.getSdk(txChainId);
+    const etherspotModularSdk = await this.getSdk(txChainId);
 
     let transactionHash: string | null = null;
     const timeoutTotal = Date.now() + timeout;
@@ -1818,7 +1827,8 @@ export class EtherspotTransactionKit implements IInitial {
     while (!transactionHash && Date.now() < timeoutTotal) {
       await new Promise<void>((resolve) => setTimeout(resolve, retryInterval));
       try {
-        transactionHash = await etherspotModulaSdk.getUserOpReceipt(userOpHash);
+        transactionHash =
+          await etherspotModularSdk.getUserOpReceipt(userOpHash);
       } catch (error) {
         console.error(
           'Error fetching transaction hash. Please check if the transaction has gone through, or try to send the transaction again:',
diff --git a/lib/interfaces/index.ts b/lib/interfaces/index.ts
index b7cbc76..b7e3091 100644
--- a/lib/interfaces/index.ts
+++ b/lib/interfaces/index.ts
@@ -236,7 +236,7 @@ export interface ToParams {
 }
 
 export interface TransactionParams {
-  chainId?: number;
+  chainId: number;
   to: string;
   value?: bigint | string;
   data?: string;
diff --git a/package-lock.json b/package-lock.json
index d9a3688..112b41d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,16 +1,16 @@
 {
   "name": "@etherspot/transaction-kit",
-  "version": "2.0.0",
+  "version": "2.0.2",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@etherspot/transaction-kit",
-      "version": "2.0.0",
+      "version": "2.0.2",
       "license": "MIT",
       "dependencies": {
         "@etherspot/eip1271-verification-util": "0.1.2",
-        "@etherspot/modular-sdk": "^6.1.1",
+        "@etherspot/modular-sdk": "6.1.1",
         "buffer": "6.0.3",
         "lodash": "4.17.21",
         "viem": "2.21.54"
diff --git a/package.json b/package.json
index e437530..61f19ce 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@etherspot/transaction-kit",
   "description": "Framework-agnostic Etherspot Transaction Kit",
-  "version": "2.0.2",
+  "version": "2.0.3",
   "main": "dist/cjs/index.js",
   "scripts": {
     "rollup:build": "NODE_OPTIONS=--max-old-space-size=8192 rollup -c --bundleConfigAsCjs",