execution-layer

The automated cycle a <a href="/en/glossary/defai-fundamentals/defai/">DeFAI</a> agent continuously repeats — read on-chain data, evaluate whether conditions are met, then assemble and submit a transaction — the core mechanism that turns an agent from passive monitoring into active execution.

In a system with multi-agent collaboration capability, a malicious third party impersonates a communication partner an agent originally trusts (another collaborating agent, or a data source, for example), sending a forged message or instruction that tricks the receiving agent into believing it's legitimate input from a trusted source and acting on it. An attack technique targeting the trust mechanism in inter-agent communication, a different attack surface from the <a href="/en/glossary/agent-permissions/delegation-chain-risk/">Delegation Chain Risk</a> discussed earlier in this series.

A mechanism where a <a href="/en/glossary/defai-fundamentals/defai/">DeFAI</a> agent continuously saves its current decision context, position information, internal strategy parameters, and other key state to storage that can be recovered after a system restart or interruption — preventing a gap between the agent's understanding of its actual holdings or pending actions and reality, caused by a server failure, network outage, or other unexpected interruption.

A mechanism where two or more autonomous AI agents directly complete a value exchange and settle obligations through on-chain transactions, without real-time human intervention — typically used for agent-to-agent task outsourcing, paid data access, or profit-sharing in multi-agent collaboration, serving as the underlying settlement layer of a multi-agent economy.

A mechanism that lets a user execute transactions without needing to hold the chain's native <a href="https://claude-me.com/en/glossary/core-concepts/token/" target="_blank" rel="noopener">Token</a> (like ETH) to pay <a href="https://crypto-bible.com/en/glossary/onchain-data/gas-fee/" target="_blank" rel="noopener">gas</a> fees — the fee can be sponsored by a third party, paid in a different token, or built directly into the transaction's own logic. Commonly used in <a href="/en/glossary/defai-fundamentals/defai/">DeFAI</a> agents to lower the operational barrier for users.

When an agent's transaction fails or its status becomes uncertain (a network timeout preventing a confirmation response from arriving, for example), it automatically resubmits the same operation. <a href="/en/glossary/execution-layer/idempotent-retry-logic/">Idempotent Retry Logic</a> ensures this retry doesn't cause the same operation to execute twice, in case the original transaction actually did succeed — the core design that makes an automated retry mechanism safe to use in a production environment.

A check where an agent, before actually submitting a transaction on-chain, first runs it entirely through a simulated environment to confirm the actual asset changes, <a href="https://crypto-bible.com/en/glossary/onchain-data/gas-fee/" target="_blank" rel="noopener">gas</a> cost, and whether it would fail — filtering out transactions that would lead to unexpected outcomes before any real funds are spent. A common safety checkpoint within a <a href="/en/glossary/defai-fundamentals/defai/">DeFAI</a> agent's execution loop.

<a href="/en/glossary/execution-layer/pre-execution-simulation/">Pre-Execution Simulation</a> can predict a transaction's outcome in a simulated environment before it's formally submitted, but a gap of some degree always exists between the simulated environment and the genuine on-chain environment, due to differing state timestamps and the simulation engine's own accuracy limits. This means "the simulation shows it's safe" doesn't equal "actual execution is definitely safe too" — how large this gap is and under what scenario it gets amplified is a layer easily overlooked yet critically important when assessing pre-execution simulation's actual reliability.

After multiple transactions are submitted at the same moment, the sequence in which they ultimately get packed into a <a href="https://crypto-bible.com/en/glossary/blockchain-fundamentals/block/" target="_blank" rel="noopener">Block</a> should theoretically be determined by a public, neutral rule (purely by submission time or priority fee level, say), but whether the role actually responsible for ordering (the block builder or <a href="https://chain-bible.com/en/glossary/layer2-scaling/sequencer/" target="_blank" rel="noopener">Sequencer</a>) could exploit this ordering power to deliberately place certain transactions in a position favorable to itself is the key component determining whether a user's transaction gets treated fairly. If this ordering power gets abused, it directly affects whether the many <a href="/en/glossary/mev-arbitrage/mev/">MEV</a> attack techniques discussed earlier in this series can actually be executed.