Launching a Proposer-Builder Separation (PBS) Adoption Roadmap

Proposer-Builder Separation (PBS) is a critical architectural upgrade for proof-of-stake blockchains, designed to mitigate centralization risks in block production. It formally separates the role of the block proposer (who selects the block) from the block builder (who constructs it). This guide outlines a phased roadmap for protocol developers and community stakeholders to adopt PBS, drawing from Ethereum's research and implementation path. The primary goals are to prevent validator centralization, reduce MEV-related harms, and enhance network neutrality by creating a competitive builder market.

The first phase involves research and specification. Teams must analyze existing PBS designs like Ethereum's enshrined PBS (ePBS) and builder APIs (e.g., the Builder API on Ethereum mainnet). This includes defining the protocol's threat model, particularly around MEV extraction and censorship. Key decisions involve choosing between a trusted relay model or a commit-reveal scheme for block submission. Concurrently, developers should prototype the core separation logic, often starting with a fork of an existing client like Prysm or Lighthouse, and integrate a minimal builder API specification for testing.

Phase two focuses on testnet deployment and builder ecosystem bootstrapping. Launch a dedicated devnet or use an existing testnet (like Goerli or Holesky) to deploy the PBS-enabled client software. Actively encourage external teams to develop block builders by providing clear documentation, SDKs, and incentive programs. For example, a testnet might run a builder competition with rewards for high-value blocks. Monitoring tools must be built to track key metrics: builder market concentration, bid inclusion rates, and the percentage of censorship-resistant blocks that include OFAC-sanctioned transactions.

The final phase is mainnet readiness and governance. This requires extensive security audits of the new consensus changes and builder relay infrastructure. A successful governance proposal must be ratified, detailing the activation epoch and contingency plans. Post-activation, the work shifts to ecosystem stewardship: monitoring builder health, adjusting parameters (like the builder bid floor), and planning for long-term upgrades like suave-style decentralized block building. Continuous iteration is essential, as PBS is not a one-time change but a foundational layer for a more robust and decentralized blockchain.

The first prerequisite is a deep technical understanding of PBS architecture and its components. You must be familiar with the roles of the block proposer, block builder, and relay, as defined in Ethereum's EIP-4844 and the evolving specifications from the Ethereum Research forum. This includes the mechanics of the builder API, the mev-boost middleware, and the trust assumptions in the relay-builder ecosystem. Without this foundational knowledge, you cannot effectively evaluate risks or design a viable integration path.

Next, assess your validator infrastructure's compatibility. PBS requires validators to run consensus and execution clients that support the builder API. Ensure your setup uses a client like Lighthouse, Teku, or Prysm with mev-boost integration. You'll need to configure secure connections to trusted relays, manage signing keys for block proposals, and establish monitoring for missed slots or relay failures. This operational readiness is non-negotiable for maintaining validator effectiveness and rewards in a PBS environment.

Strategic alignment is equally critical. You must define clear goals for adoption: is the aim to maximize MEV extraction, improve block proposal reliability, or decentralize the builder market? Engage with key stakeholders—including developers, operators, and governance token holders—to build consensus on the roadmap's priorities and success metrics. This phase often involves analyzing historical block data from services like Flashbots to model potential impact.

Finally, prepare for the legal and economic implications. PBS introduces new revenue streams and counterparty risks. You should establish a framework for evaluating relay reputations, understanding builder fee structures, and complying with any regulatory considerations around MEV. Creating a sandbox environment to test integrations with a local relay and mock builder is a recommended step before any mainnet deployment.

Proposer-Builder Separation (PBS) is a core architectural upgrade for Ethereum's consensus layer, designed to decentralize and democratize Maximum Extractable Value (MEV). In the pre-PBS model, a validator proposer is responsible for both building and proposing a block, which requires significant computational resources and exposes them to MEV-related risks like frontrunning. PBS splits this role: specialized block builders compete to create the most profitable blocks, while proposers (validators) simply select the highest-value block from a marketplace. This separation is currently facilitated off-chain by the mev-boost middleware, which acts as a relay network connecting proposers to builders. Adopting PBS is not just about earning more rewards; it's about contributing to a more resilient, efficient, and fair Ethereum ecosystem by outsourcing complex block construction.

Your adoption roadmap begins with a technical assessment. First, ensure your validator client (e.g., Prysm, Lighthouse, Teku, Nimbus) is compatible with the Builder API introduced in the Bellatrix upgrade. You must run a consensus client, an execution client (like Geth or Nethermind), and the mev-boost software as a separate service. The key configuration is pointing your validator client to the local mev-boost endpoint (typically http://localhost:18550) instead of directly to your execution client's engine API. This allows mev-boost to intercept block proposal requests, solicit bids from connected relays, and forward the most valuable block header for signing. Start by testing this setup on a Goerli or Sepolia testnet validator to familiarize yourself with the workflow and monitoring tools without risking mainnet funds.

Choosing which relays to connect to is a critical security and ethical decision. Relays are trusted intermediaries that receive block bids from builders and forward them to proposers. They must be trusted not to censor transactions or steal MEV. It is strongly recommended to connect to multiple reputable relays (e.g., Flashbots, BloXroute, Eden, Manifold) to maximize competition and redundancy. In your mev-boost configuration, this is done by adding each relay's URL. For example: -relay URL1 -relay URL2. You should also understand each relay's policy on censorship resistance and minimum bid transparency. Diversifying your relay connections reduces reliance on any single entity and aligns with Ethereum's credibly neutral principles.

Once live, monitoring is essential. Track key metrics to ensure performance and profitability. Your validator client logs will show when a block was proposed "via mev-boost." Use the mev-boost metrics endpoint (port 18550 by default) or dashboards to monitor: bid values received (in ETH), the winning relay, and missed slot rates. Compare your proposal rewards with the network average using explorers like mevboost.pics or rated.network. A significant drop in rewards or frequent missed proposals could indicate a configuration error, relay downtime, or network connectivity issue. Setting up alerts for missed proposals is crucial, as they represent lost income and can slightly impact your validator's effectiveness.

The long-term roadmap involves staying informed about in-protocol PBS (ePBS). The current mev-boost system is a temporary, off-chain implementation with trust assumptions in relays. Ethereum's core developers are actively researching designs like ePBS to bake this separation directly into the consensus protocol, eliminating the need for trusted relays. As a validator, your adoption of today's mev-boost prepares the network for this transition. Participating in testnets for ePBS proposals (like the upcoming Pectra devnet) and engaging with client development teams will be the next phase. Your experience with off-chain PBS provides invaluable data and operational knowledge that will shape the final, trust-minimized protocol.

Proposer-Builder Separation (PBS) is a design paradigm that decouples the roles of block proposal and block building. In Ethereum's post-Merge landscape, validators (proposers) can outsource block construction to specialized entities called builders via a relay. The mev-boost middleware is the standard implementation that allows a validator client to connect to this marketplace. By running mev-boost, your node receives complete, fee-optimized blocks from builders, maximizing your staking rewards through MEV (Maximal Extractable Value) without needing sophisticated infrastructure.

Before installation, ensure your setup meets the prerequisites. You need a synced Ethereum consensus client (e.g., Lighthouse, Teku, Prysm, Nimbus, Lodestar), a synced execution client (e.g., Geth, Nethermind, Besu, Erigon), and a configured validator client. Your validator must be active and proposing blocks. Crucially, you must configure your consensus client's builder API (the --builder or --http-mev-relay flag) to accept external block proposals. This tells your client to listen for blocks from mev-boost in addition to building them locally.

The core implementation involves running the mev-boost software as a separate service. You can download the latest release from the official GitHub repository. A typical startup command configures the connected relays: mev-boost -relays https://0xac6e77dfe25ecd6110b8e780608cce0dab71fdd5ebea22a16c0205200f2f8e2e3ad3b71d3499c54ad14d6c21b41a37ae@boost-relay.flashbots.net. It's critical to use multiple reputable relays from different entities (like Flashbots, BloXroute, Agnostic) for redundancy and censorship resistance. The mev-boost service runs on a specified port (e.g., -addr :18550), which your consensus client will connect to.

Integration requires modifying your consensus client's configuration to point to the local mev-boost service. For a Lighthouse validator, you would add --builder http://localhost:18550 to its beacon node arguments. For Teku, use --validators-builder-registration-default-enabled=true and --builder-endpoint=http://localhost:18550. This step is essential; without it, your validator will ignore the mev-boost service. After restarting your consensus client, monitor the logs for connections to the relay endpoints and for messages indicating it is ready to receive builder payloads.

Monitoring and maintenance are key for a reliable setup. Use your consensus client logs, mev-boost logs, and relay status pages to verify health. Important metrics include bid acceptance rates and the frequency of received blinded block messages. Be aware of validator registration: your validator's public key must be registered with the builder market via a signed message. This is typically handled automatically by your validator client when configured correctly. If your node goes offline, ensure mev-boost and all clients restart in the correct order upon reboot, usually execution client first, then consensus client, then mev-boost, then validator.

Adopting mev-boost significantly impacts reward structure. You will typically see higher, more consistent rewards compared to local block building, as you capture MEV from a competitive auction. However, you cede some control over block content. Understanding the flow is crucial: 1) A builder creates an optimized block and sends a blinded version to a relay, 2) The relay forwards the header to your mev-boost, 3) Your validator signs the header, 4) The relay reveals the full block for you to propose. This process upholds PBS's goal of keeping proposers neutral while leveraging specialized builder expertise.

Proposer-Builder Separation (PBS) is a critical architectural shift for Ethereum, designed to mitigate centralization risks in block production. In PBS, the role of a validator (the proposer) is separated from the role of assembling a block's transactions (the builder). This guide outlines a phased roadmap for a protocol or validator operator to adopt a decentralized relay strategy, moving from a centralized model like the Flashbots relay to a permissionless, competitive network. The goal is to enhance censorship resistance and distribute block-building power.

Phase 1: Research and Relay Selection

Your first step is to evaluate the relay landscape. Key metrics include relay uptime, inclusion list compliance, maximum profit bids, and geographic distribution. Analyze data from relays like Ultra Sound, Agnostic, Aestus, and bloXroute. You must also decide on your builder client software. The two primary options are mev-boost, the current standard, and the newer mev-commit, which offers PBS for both execution and consensus layers. Test integration with multiple relays in a testnet environment like Goerli or Holesky.

Phase 2: Multi-Relay Configuration and Monitoring

Avoid single points of failure by configuring your validator client to connect to multiple relays simultaneously. In mev-boost, this is done by specifying several --relay flags in your launch command. Implement robust monitoring to track performance: measure the bid acceptance rate from each relay, the average block value delivered, and relay latency. Tools like Grafana dashboards connected to Prometheus metrics from your consensus and execution clients are essential for this operational visibility. Set up alerts for relay downtime.

Phase 3: Implementing Decentralized Commitments

To advance decentralization, integrate with relays that support mev-commit or similar protocols that move towards enshrined PBS. This phase involves updating your validator setup to handle builder commitments on the consensus layer. You'll need to ensure your beacon node and validator client are compatible with the latest Ethereum consensus specifications, such as the EIP-7547 fork. This prepares your infrastructure for a future where block building is a native, auction-based protocol component rather than an off-chain service.

Phase 4: Running a Private Relay or Builder

For maximum sovereignty and to contribute to network health, consider operating your own relay or builder. Running a private relay allows you to curate a trusted set of builders and enforce specific policies, like transaction inclusion rules. Operating a builder involves sophisticated transaction sourcing, bundling, and optimization to create profitable blocks. This requires significant engineering resources for MEV detection, simulation (using tools like Reth or Erigon), and bid submission. Start by contributing to open-source projects like the flashbots/mev-boost-relay repository.

A successful PBS adoption roadmap transforms your validator from a passive participant into an active, resilient node in the block production ecosystem. By methodically progressing through relay diversification, monitoring, protocol upgrades, and potentially running your own infrastructure, you strengthen both your operational resilience and the censorship-resistant properties of the Ethereum network itself.

Enshrined Proposer-Builder Separation (PBS) is a core protocol upgrade that will formalize the roles of block proposers and block builders within Ethereum's consensus layer. Unlike the current off-chain, marketplace-driven PBS facilitated by MEV-Boost, enshrined PBS will be a native protocol feature. This transition aims to enhance decentralization, censorship resistance, and economic efficiency by providing all validators with guaranteed access to a competitive block-building market. For entities operating validators, preparing now is essential for a smooth transition and to capture the full benefits of the new design.

The roadmap begins with a technical assessment of your current infrastructure. Solo validators and staking pools must evaluate their validator client software for PBS readiness. Clients like Lighthouse, Teku, Prysm, and Nimbus will implement the new consensus APIs defined by Ethereum Improvement Proposals like EIP-7251 (increasing the MAX_EFFECTIVE_BALANCE) and the forthcoming EIPs for crList (censorship resistance lists). You should monitor client release notes and testnet announcements, such as those on the Holesky testnet, to schedule upgrades. Infrastructure must also support the new Builder API endpoints that will replace the current MEV-Boost relay interface.

Economic strategy is equally critical. Enshrined PBS introduces a new transaction flow where the proposer's role is simplified to selecting the most valuable header from builders. This changes the revenue model. Proposers will receive payments through a trusted payment channel or a new in-protocol mechanism. Staking pools need to model how builder payments flow to their stakers and update their fee structures accordingly. Understanding the proposer commitment scheme, where builders commit to a block value before seeing the full transaction list, is key to evaluating bid credibility and maximizing rewards.

For builders and searchers, enshrined PBS creates a more level playing field. The protocol will enforce crLists, allowing proposers to submit censored transactions that builders must include, mitigating censorship risks. Builders must adapt their block construction algorithms to comply with these rules while optimizing for MEV. This may involve investing in more sophisticated simulation infrastructure and competitive bidding strategies. The separation also clarifies legal and regulatory considerations by cleanly dividing block production from transaction ordering.

Long-term preparation involves active participation in the ecosystem's testing phases. Engage with client teams on forums like Ethereum R&D Discord and the ethstaker community. Run validators on devnets and public testnets that implement early PBS prototypes to gain operational experience. Document your setup, monitor for bugs, and provide feedback. This hands-on knowledge will be invaluable when the upgrade deploys on mainnet, ensuring your operation remains resilient, profitable, and aligned with Ethereum's core values of decentralization and neutrality.

Successfully implementing a PBS roadmap requires coordinated effort across different ecosystem roles. For protocol developers, the immediate focus is on integrating the builder API (builder-specs) into client software like Prysm, Lighthouse, or Teku. This involves supporting the getHeader and getPayload endpoints as defined in the Ethereum Builder API specification. For solo stakers and staking pools, the next step is to configure your validator client to connect to a relay. This typically means setting the --builder flag or modifying your configuration file to point to a relay URL, outsourcing block construction while maintaining control over which blocks are proposed.

For block builders, the development path involves creating sophisticated MEV (Maximal Extractable Value) strategies. This includes building systems for transaction aggregation, arbitrage detection, and backrunning. Builders must run execution and consensus clients, implement the builder API to receive transaction bundles from searchers, and submit signed header bids to relays. Open-source references like the Flashbots mev-boost repository provide a foundational implementation. The economic model is critical: builders must optimize for profit to cover operational costs and outbid competitors, while ensuring reliability to maintain a good reputation with proposers.

The final, crucial step for all participants is testing. Before mainnet deployment, utilize testnets like Goerli or Holesky. Validators should test relay integrations in a low-risk environment. Builders must rigorously test their bid simulation and submission logic. Looking ahead, teams should monitor the development of enshrined PBS (ePBS), a potential future protocol-level change that would bake separation directly into the consensus layer. Engaging with Ethereum Improvement Proposals (EIPs) and participating in research forums like ethresear.ch are essential for staying ahead of these evolution.