diff --git a/contracts/built-in/Extension.sol b/contracts/built-in/Extension.sol
index e5f3d1d..5fd2a84 100644
--- a/contracts/built-in/Extension.sol
+++ b/contracts/built-in/Extension.sol
@@ -28,4 +28,8 @@ interface Extension {
 
     /// @notice Get the account that pays the TX fee at runtime.
     function txGasPayer() external view returns (address);
+
+    // extension v3 methods
+    function txClauseIndex() external view returns (uint256);
+    function txClauseCount() external view returns (uint256);
 }
diff --git a/network/config/genesis.json b/network/config/genesis.json
index 950e1b8..615ab2c 100644
--- a/network/config/genesis.json
+++ b/network/config/genesis.json
@@ -9,7 +9,7 @@
         "ETH_IST": 0,
         "VIP214": 0,
         "FINALITY": 0,
-        "GALACTICA": 0
+        "GALACTICA": 1
     },
     "accounts": [
         {
diff --git a/test/evm/builtins/extension.test.js b/test/evm/builtins/extension.test.js
new file mode 100644
index 0000000..246ef57
--- /dev/null
+++ b/test/evm/builtins/extension.test.js
@@ -0,0 +1,64 @@
+import { ThorWallet } from '../../../src/wallet'
+import { Client } from '../../../src/thor-client'
+import { contractAddresses } from '../../../src/contracts/addresses'
+import { Extension__factory } from '../../../typechain-types'
+import { addUintPadding } from '../../../src/utils/padding-utils'
+
+describe('Builtin :: Extension', () => {
+    const wallet = ThorWallet.withFunds()
+    const extension = Client.sdk.contracts.load(
+        contractAddresses.extension,
+        Extension__factory.abi,
+    )
+
+    it.e2eTest('should be able to get the clause count', 'all', async () => {
+        const count = 100
+        const contractCall = await extension.clause.txClauseCount()
+        const clause = {
+            to: extension.address,
+            value: '0x0',
+            data: contractCall.clause.data,
+        }
+        const best = await Client.raw.getBlock('best')
+        const clauses = Array.from({ length: count }).map(() => clause)
+        const batchCall = await Client.raw.executeAccountBatch(
+            {
+                gas: 10_000_000,
+                caller: wallet.address,
+                clauses,
+            },
+            best.body.id,
+        )
+
+        for (let i = 0; i < count; i++) {
+            expect(batchCall.body[i].data).toEqual('0x' + addUintPadding(count))
+        }
+    })
+
+    it.e2eTest('should be able to get the clause index', 'all', async () => {
+        const amount = 50
+
+        const contractCall = await extension.clause.txClauseIndex()
+        const clause = {
+            to: extension.address,
+            value: '0x0',
+            data: contractCall.clause.data,
+        }
+
+        const clauses = Array.from({ length: amount }).map(() => clause)
+
+        const best = await Client.raw.getBlock('best')
+        const batchCall = await Client.raw.executeAccountBatch(
+            {
+                gas: 10_000_000,
+                caller: wallet.address,
+                clauses,
+            },
+            best.body.id,
+        )
+
+        for (let i = 0; i < amount; i++) {
+            expect(batchCall.body[i].data).toEqual('0x' + addUintPadding(i))
+        }
+    })
+})