The amount of gas used to verify the smart account or paymaster signature was higher than the verificationGasLimit.

Troubleshooting

1. First, verify the verificationGasLimit is a reasonable value.
   1. Simple user operations should be between 50,000 and 100,000 gas, while more complex user operations can be as much as 2 million gas.
   2. Check your verificationGasLimit against the values returned by eth_estimateUserOperationGas and pm_sponsorUserOperation API methods.
   3. If you are hard-coding the verificationGasLimit, consider using the eth_estimateUserOperationGas limit.
2. Investigate why the smart account and/or paymaster used more gas than expected using tools like userop.dev, Tenderly, or the ERC-4337 Devnet.
3. Reach out to your bundler provider or ask a question in the Stackup Discord server for help. Be sure to include the user operation and any relevant information about how you're building it.