Specify Builder Configurations and Bid selection strategies by bharath-123 · Pull Request #144 · ethereum/builder-specs

bharath-123 · 2026-01-13T07:10:39Z

This PR standardizes how clients configure builder lists and their corresponding configurations for interacting with builders over the builder-api.

New Containers

We define three new containers:

BuilderConfig: Contains per-builder configuration:
- url: The builder endpoint URL
- max_trusted_bid: Maximum amount the proposer will accept in trusted payments
- min_bid: Minimum acceptable bid value from the builder
- bid_boost: Multiplier factor (in basis points, where 10000 = 100%) applied to the builder's bid value when comparing against other bids.
GlobalPreferences: Contains validator preferences that apply across all builders:
- bid_selection_strategy: Strategy for selecting the winning bid from multiple bids (e.g., max_profit)
- local_block_boost: Multiplier factor (in basis points) applied to locally built block values, giving priority to local blocks in bid selection
- p2p_bid_block_boost: Multiplier factor (in basis points) applied to bids received from the p2p topic, giving priority to p2p bids in bid selection
BuilderWhitelist: Top-level container combining:
- builders: List of BuilderConfig entries (up to MAX_WHITELISTED_BUILDERS)
- global_preferences: The GlobalPreferences configuration

Implementation

The boost parameters (bid_boost, local_block_boost, p2p_bid_block_boost) allow validators to express preferences between different bid sources. For example, a validator might apply a 110% boost (11000 basis points) to their local block to prefer building locally unless an external bid is significantly better.

How clients fetch bids from builders and send validator registrations remains an implementation detail. This PR only standardizes the per-builder and global configurations for whitelisted builder. A client could query all builders in the whitelist in parallel to fetch their bids, then apply the configured bid_selection_strategy and boost parameters to select the winning bid.

bharath-123 · 2026-01-16T16:46:01Z

+    # Builders must respond by 2 seconds into the slot
+    # This leaves 2 seconds for local building fallback
+    return slot_start + BUILDER_DEADLINE_MS


This deadline can be just 1 sec.

bharath-123 · 2026-01-16T16:46:56Z

+            # Validate the bid
+            registration = registrations.get(builder_config.url)
+            if registration and validate_bid(state, registration, signed_bid, registration.message.fee_recipient):
+                bids.append((builder_config, signed_bid))


Bid needs to be boosted before being added.

bharath-123 · 2026-01-19T11:46:46Z

-| `MAX_SALT_BYTES`                          | `4096`             |
+| Name | Value | | ----------------------------------------- |
+------------------ | | `MAX_SALT_BYTES` | `4096` | | `MAX_URL_BYTES` | `4096` |
+| `MAX_WHITELISTED_BUILDERS` | `10000` | | `BUILDER_DEADLINE_MS` | `2000` | | `MAX_STRATEGY_DESC_BYTES` | `4096` |


Need to fix formatting

bharath-123 · 2026-01-19T12:14:30Z

+### `BuilderConfig`
+
+```python
+class BuilderConfig(Container):


MEV-Boost could be a special case of just having one builder in the configuration pointing to the url of the local mev-boost container.

bharath-123 · 2026-01-19T12:17:29Z

+and decide on the best possible bid after making all requests.
+
+```python
+def query_builders(


Maybe it is not necessary to specify how to fetch bids and send registrations in the specification and leave this to implementation. We could just specify the BuilderConfig

potuz · 2026-01-19T12:54:48Z

I don't see how this replaces Mev Boost. There are two components to mev boost, one is to request bids from multiple builders/relays. The other one is to handle exchange of blind signed objects. The first part has to be implemented by CL clients on Gloas to be able to request signed bids from builders directly. The second part would be the core feature of Mev Boost that this PR does not make any mention of.

tersec · 2026-01-19T13:47:42Z

The main functionality of MEV-Boost is to maintain a whitelist of builders

How/where? https://github.com/flashbots/mev-boost/blob/develop/cli/flags.go selects from entities the current builder API MEV ecyosystem calls relays (which, "whitelist" is an odd word here: it's mostly that they have to be queried explicitly, not that other relays are providing information which is being ignored). It doesn't know or care about what the current builder API MEV ecosystem calls "builders".

Yes, ePBS changes this terminology, but in terms of discussing what mev-boost the builder API software does, it's worth being clear about the terminology it uses.

bharath-123 · 2026-01-19T14:11:55Z

I don't see how this replaces Mev Boost. There are two components to mev boost, one is to request bids from multiple builders/relays. The other one is to handle exchange of blind signed objects. The first part has to be implemented by CL clients on Gloas to be able to request signed bids from builders directly. The second part would be the core feature of Mev Boost that this PR does not make any mention of.

With ePBS, we won't have blind signed objects. With the Builder-API with ePBS, the CL client would query the block builders for all their bids, pick the winning bid, embed it to the beacon block and send the beacon block to the builder whose bid has been selected.

I should note that, I intended to have this PR only for ePBS and not pre-ePBS. So we wouldn't have blind signing going forward in ePBS.

bharath-123 · 2026-01-19T14:13:57Z

The main functionality of MEV-Boost is to maintain a whitelist of builders

How/where? https://github.com/flashbots/mev-boost/blob/develop/cli/flags.go selects from entities the current builder API MEV ecyosystem calls relays (which, "whitelist" is an odd word here: it's mostly that they have to be queried explicitly, not that other relays are providing information which is being ignored). It doesn't know or care about what the current builder API MEV ecosystem calls "builders".

Yes, ePBS changes this terminology, but in terms of discussing what mev-boost the builder API software does, it's worth being clear about the terminology it uses.

Yes we can be more clear about the terminology here for sure. I will re-work that aspect. Ideally relays and builders are technically interchangable.

bharath-123 added 30 commits January 8, 2026 10:13

initial builder-api for gloas

d87aa1a

updates

f087efb

pass in params while querying execution payload bid

85f6f8f

introduce validator registrations v2

5ed1841

run doctoc

503eee6

update validator registration v2

7dde2ec

add more specs

8011cd8

run lint

610bfae

updates

beef159

abstract execution_payment_accepted to a BuilderPreferences struct

9a6eeb7

minor fixes

36fdcd2

run doctoc

75a9906

use correct method to check if builder is active

b2b5974

save

6e8f58a

updates

5f67639

add information for bidding

d503193

update

c78bccd

add bid request auth

959babe

remove builder index from validator registration

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add validator registration type

a382dcc

link to api calls

29c1908

add some notes

ec5f63f

fix return type of execution_payload_bid.yaml

2ee40cd

use max_trusted_bid in builder preferences

104cd7d

run linter

aef010d

fix spellchecker

ef1ffce

update bid request auth according to feedback

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minor updates

fbaeee5

use a salt in the bid request auth

0cd4399

correctly render constants table

b299c34

bharath-123 added 2 commits January 9, 2026 22:40

address feedback

d7bf68f

update bid request auth to request auth

c39bf4a

bharath-123 commented Jan 16, 2026

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bharath-123 commented Jan 19, 2026

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bharath-123 force-pushed the epbs-builder-config branch from 6327e7e to b4d745e Compare January 19, 2026 11:53

bharath-123 mentioned this pull request Jan 19, 2026

All Core Devs - Testing (ACDT) #66, January 19, 2026 ethereum/pm#1878

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bharath-123 commented Jan 19, 2026

View reviewed changes

bharath-123 force-pushed the epbs-builder-config branch from ef29bb8 to 0c9dced Compare January 20, 2026 06:41

bharath-123 changed the title ~~Specify Builder Configurations, Bid multiplexing and Bid selection strategies~~ Specify Builder Configurations and Bid selection strategies Jan 20, 2026

bharath-123 added 6 commits January 20, 2026 20:25

fix typo

75749c0

use salt instead of url

accd79c

use get-upcoming-proposal-slots

53c7d9f

Update liveness failsafe section

b522a99

define builder config spec

9f7d9c0

update validator.md

43f15ca

bharath-123 force-pushed the epbs-builder-config branch from b037d16 to 43f15ca Compare February 6, 2026 12:17

fix conflict

0e77300

shane-moore mentioned this pull request Mar 6, 2026

Produce block v4 with payload ethereum/beacon-APIs#580

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bharath-123 force-pushed the epbs-updates branch from 9d5be35 to 3b5735b Compare March 12, 2026 08:08

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Specify Builder Configurations and Bid selection strategies#144

Specify Builder Configurations and Bid selection strategies#144
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