Flashbots

Flashbots provides Ethereum execution infrastructure with two distinct paths: an auction and relay system for bundles and block building, and private order-flow routes for wallets and applications. The relevant choice is whether the caller is protecting a normal transaction, submitting a bundle, or operating validator infrastructure.

Bundles express ordering, but builders and proposers still choose

In the Auction flow, a searcher submits signed transactions as a bundle with a target block and optional conditions such as replacement, builder sharing or allowed reverts. Builders combine candidate bundles with other order flow to make blocks, while a relay withholds the payload until a validator signs the selected header commitment.

A valid bundle is not a landing guarantee. State changes, competing bundles, simulation, builder policy and proposer selection can prevent inclusion, so an integration needs target-block, nonce, fee and missed-submission handling rather than treating the endpoint as a deterministic execution route.

Protect changes public-mempool exposure, not every execution risk

Protect sends a signed Ethereum transaction through a private path instead of broadcasting it immediately to the public mempool. Its default behaviour retries for up to 25 blocks, excludes reverted transactions and drops a transaction that does not land in that window, so private submission is not a promise of inclusion.

Privacy hints can range from a hash to calldata and transaction fields. Sharing more can enable searcher participation and refunds, but increases what counterparties see; fast mode broadens builder distribution and permits TEE searchers to view full information after a delay, including for failed or reverted transactions.

MEV-Share adds configurable sharing and backrun economics

MEV-Share lets an order-flow source disclose selected information to searchers, which submit partial bundles for simulation and possible forwarding to builders with a refund condition. The documented node accepts backruns only, making it narrower than a general interface for arbitrary reordering strategies.

Flashbots does not take custody or set an application’s execution-risk policy. Builders, relays, validators and selected searchers remain separate trust and availability surfaces; applications must decide on simulation, deadlines, fallbacks and whether a missed private transaction may be rebroadcast publicly.