Engine - AA account salt, new API reference, retry errors, + bugfixes

Phillip Ho

Engine has been updated to v2.0.25 which brings a handful of improvements.

First what is an account salt? The account salt is a unique ID that deterministically predicts a wallet address for a given admin + smart account factory.

This means your backend can provide a unique ID (like your dApp's user ID) as an account salt to Engine, and Engine will consistently reference and/or deploy the same smart account address each time (for the same admin + factory).

Here's an example:

My game has user IDs uid1, uid2, and uid3.

When a user signs up, the user's smart account calls my game contract.

Steps without account salt
1. User signs up.
2. Backend calls Engine to create a smart account.
3. Backend waits for the transaction to be mined.
4. Backend calls Engine with x-account-address: <address from step 2> to call the contract on behalf of the account.

Steps with account salt
1. User signs up.
2. Backend calls Engine with x-account-salt: uid1 to call the contract on behalf of the account.

💡 Bonus: The account is not deployed until a write transaction, deferring gas fees until the account is actually used!

The following endpoints now accept the x-account-salt header (more to come!):

• /contract/:chain/:contractAddress/write
• /contract/:chain/:contractAddress/erc20/claim-to
• /contract/:chain/:contractAddress/erc721/claim-to
• /contract/:chain/:contractAddress/erc1155/claim-to

To deploy a smart account from the account salt, call Create Smart Account and set the extraData arg to the salt.

To predict a smart account address from the account salt without deploying it, call Predict Address and set the extraData arg to the salt.

Our API reference page has moved! 👉 engine-api.thirdweb.com

This new API reference docs make it easier to search for endpoints (try CTRL/⌘+K), see path/query/body params, and view sample code.

You can even test requests right in the API docs page! Select Test Request and provide the following details:

The Send Retry (Synchronous) endpoint now allows retrying any transaction that was sent (either still waiting to be mined or "timed out"). This commonly occurs when a transaction is stuck because of gas spikes or other network congestion.

If a transaction appears stuck, try to resend with aggressive (3-10x) gas fees:

await fetch('https://<YOUR_ENGINE_URL>/transaction/sync-retry', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    Authorization: 'Bearer <YOUR_SECRET_TOKEN>'
  },
  body: JSON.stringify({
    queueId: '9eb88b00-f04f-409b-9df7-7dcc9003bc35',
    maxFeePerGas: '500000000000', // 500 gwei
    maxPriorityFeePerGas: '100000000000', // 100 gwei
  })
})

• Fixed issue signing messages with Google Cloud KMS and AWS KMS wallets.
• Fixed import of Google Cloud KMS wallets. (Thanks @yukia3e !)
• Fixed 500 response when using an unrecognized backend wallet.
• Updated userOp code to the latest thirdweb SDK -> simpler code and performance optimizations.
• Fix nonce resync worker exiting early when there are multiple wallets sending transactions concurrently.
• Handle errors of different types better to avoid "empty" error messages.
• Fallback if the contract write call is provided an incomplete ABI (missing inputs or outputs fields).
• Updated log lines to be single-line for improved debuggability.
• Added lots of new route tests around signMessage, contract write, and userOps.

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