EVM Onchain Actions

Build EVM workflows that read chain data, evaluate policy, and execute wallet-backed transactions.

EVM actions let workflows read chain state and execute wallet-backed transactions. Use them for token transfers, contract calls, approvals, swaps, position management, and policy-driven automations.

Stablecoin-to-stablecoin swaps inside B3OS are gasless, powered by Relay. Build a token-to-token swap workflow in under a minute.

Common EVM Workflow

graph TD
Trigger[Trigger] --> Read[Read chain or market data]
Read --> Policy[Policy branch]
Policy -->|Allowed| Simulate[Optional simulation]
Simulate --> Tx[Wallet-backed transaction]
Policy -->|Blocked| Notify[Notify or log]
Tx --> Record[Record result]

Design Rules

RuleWhy
Read before writeChain state can change and provider inputs need validation
Validate addressesWrong-chain or malformed addresses can fail or send funds incorrectly
Check balancesGas token and asset balances affect transaction success
Use policy branchesPrevent unintended transactions from noisy triggers or malformed payloads
Keep approvals narrowBroad approvals increase risk
Record transaction hashDownstream systems need traceability

Inputs to Validate

InputExamples
ChainBase, Ethereum, or another supported EVM chain
TokenContract address, symbol, decimals, native token flag
AmountRaw units or token units, slippage, minimum output
RecipientAddress, contract, treasury, protocol address
ABI and methodFunction name, argument types, payable value
WalletOrganization wallet and execution permissions

Session Keys and Nonces

Some EVM workflows use session-key or delegated execution patterns. B3OS also coordinates nonce-sensitive wallet execution to reduce conflicts between concurrent transactions.

Avoid publishing multiple high-frequency workflows that spend from the same wallet without understanding nonce, gas, and balance behavior.

Failure Modes

FailureTypical cause
Schema validation failedMissing chain, wallet, address, token, or amount field
Simulation failedContract would revert, insufficient balance, or invalid calldata
Transaction revertedChain state changed, slippage, allowance, deadline, or contract condition
Nonce conflictConcurrent transaction activity
Provider errorRPC, rate limit, unsupported chain, or malformed request
Wallets

Organization wallet model and transaction safety.

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Security

Workflow, API key, connector, webhook, and wallet protections.

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Expressions

Pass trigger and read-action data into transaction payloads.

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