feat(buildoor): auto-add payload-attributes flag to first participant - #1429
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When mev_type is buildoor, the builder connects directly to the first participant's beacon node and relies on its payload_attributes SSE stream to trigger block building. Beacon nodes only emit these events for slots they propose unless explicitly told to build a payload on every slot. Automatically add the relevant flag to the first participant's CL: - lodestar: --emitPayloadAttributes=true - prysm: --prepare-all-payloads - lighthouse: --always-prepare-payload teku, nimbus, grandine and consensoor have no equivalent flag, so fail fast with a clear message when one of them is the first participant.
grandine builds a payload on every slot with --features=AlwaysPrepareExecutionPayload, so wire it up and drop it from the fail list (teku, nimbus and consensoor still have no such flag).
consensoor now emits payload_attributes on every slot natively (ethpandaops/consensoor#8), so it needs no extra flag — drop it from the fail list. teku and nimbus still have no way to and still fail fast.
consensoor now gates payload_attributes emission behind a flag, so pass --emit-payload-attributes when it's the first participant rather than relying on it being on by default.
pk910
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Jun 19, 2026
barnabasbusa
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Jun 19, 2026
Follow-up to #1429. teku can emit `payload_attributes` on every slot via `-Xfork-choice-updated-always-send-payload-attributes`, so it can serve as buildoor's first participant. Wire up the flag and drop teku from the fail list. ## Changes `enrich_mev_extra_params` (`src/package_io/input_parser.star`), gated on `mev_type == buildoor` and `index == 0`: | CL | Flag added | |---|---| | lodestar | `--emitPayloadAttributes=true` | | prysm | `--prepare-all-payloads` | | lighthouse | `--always-prepare-payload` | | grandine | `--features=AlwaysPrepareExecutionPayload` | | consensoor | `--emit-payload-attributes` | | **teku** | **`-Xfork-choice-updated-always-send-payload-attributes=true`** | | nimbus | fail fast (no equivalent flag) | Only **nimbus** is left unsupported. ## Testing `kurtosis run --dry-run`: - teku + buildoor → parses and runs end-to-end (exit 0). - nimbus + buildoor → fails with the intended error message.
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What
When
mev_type: buildooris set, automatically add the "build a payload on every slot" flag to the first participant's consensus client.Why
Buildoor connects directly to the first participant's beacon node (
all_cl_contexts[0]) and subscribes to its/eth/v1/events?topics=payload_attributesSSE stream to know when to start building. Beacon nodes only emit these events for slots they propose unless explicitly told to always prepare a payload — so without this flag buildoor wouldn't reliably trigger block building. Previously this flag had to be added manually viacl_extra_params.Changes
In
enrich_mev_extra_params(src/package_io/input_parser.star), gated onmev_type == buildoorandindex == 0:--emitPayloadAttributes=true--prepare-all-payloads--always-prepare-payload--features=AlwaysPrepareExecutionPayloadteku,nimbusandconsensoorhave no equivalent flag, so the parser now fails fast with a clear message naming the offending client when one of them is the first participant.Testing
kurtosis run --dry-runconfirmed: