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What chains does Shield support?

Shield supports the same chains as the Enso API. See the Supported Networks page for the full list.

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How long are simulations cached?

Simulations are cached for 5 minutes. After that, the simulationId expires and validation will return a 404 error. Re-simulate to get a fresh ID.

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Can I simulate transactions from other APIs?

Yes. Shield is source-agnostic — you can simulate any valid EVM transaction regardless of where the calldata came from. See the Third-Party Transactions guide for examples with custom contracts and more.

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Does Shield modify my transaction?

No. Shield only simulates and validates. The transaction you submit on-chain is exactly what you built. Shield never alters your calldata, target address, or value.

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What authentication does Shield use?

The same Enso API key used for the main Enso API. Pass it as a Bearer token in the Authorization header or as an api_key query parameter. See the Authentication guide.

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What is the base URL?

https://shield.api.enso.build

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How is the data field validated?

The calldata is compared by hash, not raw byte comparison. This means any modification to the data field — even a single byte — will cause the data check to fail during validation.

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Can I simulate delegate calls?

Yes. Set operationType: 1 in the transaction object to simulate a DelegateCall. This is useful for smart account and ERC-4337 scenarios. The default (0) is a standard Call.

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What are preSimulationTransactions?

Optional setup transactions that execute before the main simulation. Common uses include:
  • Token approvals — Approve a contract to spend tokens before simulating a deposit
  • State setup — Set up any on-chain state your main transaction depends on
See the Simulate guide for examples.

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How accurate is the gas estimate?

The gas estimate comes from actual EVM execution on a forked state, so it is highly accurate at the time of simulation. However, gas consumption can change if on-chain state changes between simulation and execution (e.g., storage slot modifications by other transactions).

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