check if existing userOperation is already in internal mempool

src/mempool/mempool.ts

@@ -258,6 +258,16 @@ export class MemoryMempool {
                 .map(({ userOperation }) => userOperation)
         ]
 
+        // Check if the exact same userOperation is already in the mempool.
+        const existingUserOperation = [
+            ...outstandingOps,
+            ...processedOrSubmittedOps
+        ].find(({ userOperationHash }) => userOperationHash === opHash)
+
+        if (existingUserOperation) {
+            return [false, "Already known"]
+        }
+
         if (
             processedOrSubmittedOps.find(({ mempoolUserOperation }) => {
                 const userOperation = deriveUserOperation(mempoolUserOperation)

src/rpc/rpcHandler.ts

@@ -909,7 +909,7 @@ export class RpcHandler implements IRpcEndpoint {
                         getAAError(errorReason)
                     )
                     throw new RpcError(
-                        `UserOperation reverted during simulation with reason: ${errorReason}`,
+                        errorReason,
                         ValidationErrors.InvalidFields
                     )
                 }
@@ -952,7 +952,7 @@ export class RpcHandler implements IRpcEndpoint {
                         getAAError(errorReason)
                     )
                     throw new RpcError(
-                        `UserOperation reverted during simulation with reason: ${errorReason}`,
+                        errorReason,
                         ValidationErrors.InvalidFields
                     )
                 }

test/e2e/tests/eth_sendUserOperation.test.ts

@@ -12,7 +12,8 @@ import {
     type EntryPointVersion,
     UserOperationReceiptNotFoundError,
     entryPoint06Address,
-    entryPoint07Address
+    entryPoint07Address,
+    UserOperation
 } from "viem/account-abstraction"
 import { generatePrivateKey } from "viem/accounts"
 import { foundry } from "viem/chains"
@@ -383,5 +384,39 @@ describe.each([
                 )
             ).toEqual(true)
         })
+
+        test("Should throw 'already known' if same userOperation is sent twice", async () => {
+            const smartAccountClient = await getSmartAccountClient({
+                entryPointVersion
+            })
+
+            const to = "0x23B608675a2B2fB1890d3ABBd85c5775c51691d5"
+            const value = parseEther("0.15")
+
+            const userOperation =
+                (await smartAccountClient.prepareUserOperation({
+                    calls: [
+                        {
+                            to,
+                            value,
+                            data: "0x"
+                        }
+                    ]
+                })) as UserOperation
+            userOperation.signature =
+                await smartAccountClient.account.signUserOperation(
+                    userOperation
+                )
+
+            await smartAccountClient.sendUserOperation(userOperation) // first should go through
+
+            await expect(async () => {
+                await smartAccountClient.sendUserOperation(userOperation) // second should fail due to "already known"
+            }).rejects.toThrowError(
+                expect.objectContaining({
+                    details: expect.stringContaining("Already known")
+                })
+            )
+        })
     }
 )