feat(chain): implement BRIP-0008 hysteresis update for Fulu fork by calbera · Pull Request #3081 · berachain/beacon-kit

calbera · 2026-04-16T11:13:14Z

https://github.com/berachain/BRIPs/blob/main/meta/BRIP-0010.md

Add the Fulu fork (CL component of the Fusaka hardfork) with:

BRIP-0008: Fork-gated hysteresis parameter updates that improve validator capital efficiency by reducing the upward buffer from 125% to ~110% of the effective balance increment (HysteresisQuotient: 4->100, UpwardMultiplier: 5->10, DownwardMultiplier: 1->1 unchanged).
PoL vNext: New EVMInflationAddressFulu and EVMInflationPerBlockFulu fields following the same pattern as the Genesis-to-Deneb1 inflation migration. Values are placeholders pending PoL vNext design finalization.
Fulu fork plumbing: version constant (0x06000000), fork time in chain spec, fork ordering validation, state upgrade handler, Engine API routing, consensus type support, and osakaTime in EL genesis configs.

All devnet/testnet/mainnet chain specs and TOML configs updated with placeholder values (devnet: active from genesis, testnet/mainnet: far future).

…Fulu fork Add the Fulu fork (CL component of the Fusaka hardfork) with: - BRIP-0008: Fork-gated hysteresis parameter updates that improve validator capital efficiency by reducing the upward buffer from 125% to ~110% of the effective balance increment (HysteresisQuotient: 4->100, UpwardMultiplier: 5->10, DownwardMultiplier: 1->1 unchanged). - PoL vNext: New EVMInflationAddressFulu and EVMInflationPerBlockFulu fields following the same pattern as the Genesis-to-Deneb1 inflation migration. Values are placeholders pending PoL vNext design finalization. - Fulu fork plumbing: version constant (0x06000000), fork time in chain spec, fork ordering validation, state upgrade handler, Engine API routing, consensus type support, and osakaTime in EL genesis configs. All devnet/testnet/mainnet chain specs and TOML configs updated with placeholder values (devnet: active from genesis, testnet/mainnet: far future). https://claude.ai/code/session_01WL9ZgSDBYTcr1X91AYuPrU

…enesis Devnet now starts at the Fulu fork (FuluForkTime=0), so e2e tests that hardcoded Electra1 as the expected genesis fork version need updating. https://claude.ai/code/session_01WL9ZgSDBYTcr1X91AYuPrU

Copilot

Pull request overview

Implements the Fulu fork across the consensus layer, including fork-gated BRIP-0008 hysteresis parameter updates, PoL vNext inflation placeholders, and the required fork plumbing/routing so both CL and EL config paths recognize the new fork.

Changes:

Add Fulu (0x06000000) fork version support and fork-time plumbing across chain spec, state upgrade handling, and consensus types.
Gate hysteresis parameters by active fork (timestamp-based) per BRIP-0008, and add Fulu-specific spec fields.
Extend EL genesis / network config fixtures with osakaTime and add Fulu placeholders to TOML chain specs.

Reviewed changes

Copilot reviewed 28 out of 28 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
testing/simulated/el-genesis-files/eth-genesis.json	Adds `osakaTime` to simulated EL genesis config.
testing/networks/80094/spec.toml	Adds `fulu-fork-time` and Fulu hysteresis/PoL placeholder fields for network 80094.
testing/networks/80094/eth-genesis.json	Adds `osakaTime` placeholder for network 80094 EL genesis.
testing/networks/80069/spec.toml	Adds `fulu-fork-time` and Fulu hysteresis/PoL placeholder fields for network 80069.
testing/networks/80069/eth-genesis.json	Adds `osakaTime` placeholder for network 80069 EL genesis.
testing/files/spec.toml	Adds Fulu fork time and Fulu hysteresis/PoL fields for test fixtures.
testing/files/eth-genesis.json	Adds `osakaTime` to test fixture EL genesis config.
state-transition/core/state_processor_forks.go	Adds Fulu fork processing, state upgrade handler, and fork logging.
state-transition/core/state_processor.go	Uses fork-gated hysteresis parameters during effective balance updates.
primitives/version/versions.go	Introduces `Fulu()` version constant and removes unused `Electra2`.
primitives/version/supported.go	Adds Fulu to the supported fork version list.
primitives/version/name.go	Adds human-readable name mapping for Fulu.
execution/client/ethclient/engine_test.go	Updates invalid-version test to use `Capella()` instead of removed `Electra2()`.
execution/client/ethclient/engine.go	Routes Fulu to the same Engine API variants as Electra1 where applicable.
consensus-types/types/signed_beacon_block.go	Allows creating empty signed blocks for Fulu version.
consensus-types/types/payload.go	Allows payload header conversion for Fulu version.
consensus-types/types/block.go	Allows beacon block creation for Fulu version.
config/spec/testnet.go	Adds placeholder `FuluForkTime` to testnet chain spec data.
config/spec/mainnet.go	Adds Fulu fork time + Fulu hysteresis/PoL placeholder constants and wires into mainnet spec data.
config/spec/devnet.go	Sets devnet to start with Fulu active and adds Fulu PoL inflation config.
cli/commands/genesis/payload.go	Extends supported fork range checks up to Fulu for genesis payload header handling.
chain/spec_test.go	Updates fork-order validation tests to include Fulu.
chain/spec.go	Adds Fulu fork time, enforces ordering including Fulu, gates hysteresis and PoL fields by active fork.
chain/helpers_test.go	Updates helper spec construction to include `FuluForkTime`.
chain/helpers.go	Extends fork-version selection by timestamp to include Fulu.
chain/data.go	Adds SpecData fields for Fulu fork time, Fulu hysteresis parameters, and Fulu PoL inflation fields.

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The simulated test chain spec providers override Electra1ForkTime to far-future values but didn't set FuluForkTime, causing fork ordering violations since testnet's FuluForkTime (9999999999999999) was smaller than the overridden Electra1ForkTime (math.MaxInt64). https://claude.ai/code/session_01WL9ZgSDBYTcr1X91AYuPrU

Expand the comment in processEffectiveBalanceUpdates to explain that the previous block's payload timestamp is used for fork gating because processEpoch runs inside ProcessSlots (before ProcessFork updates the state). This means Fulu hysteresis values take effect one epoch after fork activation at an exact epoch boundary — acceptable since hysteresis only affects capital efficiency, not consensus safety. https://claude.ai/code/session_01WL9ZgSDBYTcr1X91AYuPrU

The testing/simulated/el-genesis-files/eth-genesis.json file is paired with ProvideSimulationChainSpec where Electra, Electra1, and Fulu are all far-future. The file intentionally omits pragueTime to test pre- Pectra behavior. Adding osakaTime=0 created an invalid config (Osaka without Prague), causing Geth containers to fail to start in simulated tests. https://claude.ai/code/session_01WL9ZgSDBYTcr1X91AYuPrU

codecov · 2026-04-17T14:31:51Z

Codecov Report

❌ Patch coverage is 83.03571% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.41%. Comparing base (2f41454) to head (872e2dc).

Files with missing lines	Patch %	Lines
state-transition/core/state_processor_forks.go	82.50%	5 Missing and 2 partials ⚠️
execution/client/ethclient/engine.go	0.00%	5 Missing ⚠️
chain/spec.go	87.09%	4 Missing ⚠️
state-transition/core/state_processor.go	62.50%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3081      +/-   ##
==========================================
- Coverage   60.44%   60.41%   -0.04%     
==========================================
  Files         367      367              
  Lines       18610    18698      +88     
==========================================
+ Hits        11249    11296      +47     
- Misses       6422     6458      +36     
- Partials      939      944       +5

Files with missing lines	Coverage Δ
chain/helpers.go	`85.18% <100.00%> (+1.85%)`	⬆️
cli/commands/genesis/payload.go	`54.19% <100.00%> (ø)`
config/spec/devnet.go	`100.00% <100.00%> (ø)`
config/spec/mainnet.go	`100.00% <100.00%> (ø)`
config/spec/testnet.go	`100.00% <100.00%> (ø)`
consensus-types/types/block.go	`97.14% <100.00%> (ø)`
consensus-types/types/payload.go	`92.54% <100.00%> (ø)`
consensus-types/types/signed_beacon_block.go	`93.18% <100.00%> (ø)`
primitives/version/name.go	`45.45% <100.00%> (-4.55%)`	⬇️
primitives/version/supported.go	`100.00% <ø> (ø)`
... and 5 more

... and 1 file with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

fridrik01

mostsly nits

fridrik01 · 2026-04-20T13:22:14Z

-	switch fv {
-	case version.Deneb1(), version.Electra(), version.Electra1():
+	switch {
+	case version.EqualsOrIsAfter(fv, version.Fulu()):


Should we not check for exact version here? If we add Fulu1 (or future fork) then we would silently return here instead of panicking which is how the switch was written explicitly before.

Suggested change

case version.EqualsOrIsAfter(fv, version.Fulu()):

case version.Equals(fv, version.Fulu()):

Well I'd argue it's more correct now. For example the value we set in Deneb1 EVMInflationAddressDeneb1 is actually valid from fork Deneb1 and onwards (including Electra and Electra1) until its overriden with a new value. Which is now EVMInflationAddressFulu; this value is valid until overriden again. So for Fulu1 it would also be used by default.

Also adjusted other functions to work like this in 4d88d47

fridrik01 · 2026-04-20T13:22:43Z


 	// HysteresisDownwardMultiplier returns the multiplier used when checking
 	// if the effective balance should be decreased.
 	HysteresisDownwardMultiplier() math.U64


Looking at the code its unclear why HysteresisUpwardMultiplier takes an argument but HysteresisDownwardMultiplier does not. Since HysteresisDownwardMultiplier does not change in the fork there is no need to, but maybe add an inline comment (or pass a unused timetsamp)

Added comment in 3cdc138

…tamp

…om:berachain/beacon-kit into claude/implement-brip-0008-pol-vnext-p043C

claude and others added 3 commits April 16, 2026 10:57

update values

095433f

fix

36c3ee0

calbera requested a review from a team April 16, 2026 11:13

calbera added 2 commits April 16, 2026 16:45

nit

75c2286

format

21e8648

calbera marked this pull request as ready for review April 16, 2026 11:39

calbera requested a review from a team as a code owner April 16, 2026 11:39

Copilot AI review requested due to automatic review settings April 16, 2026 11:39

Copilot started reviewing on behalf of calbera April 16, 2026 11:40 View session

fix(e2e): update test expectations from Electra1 to Fulu for devnet g…

4e3c20d

…enesis Devnet now starts at the Fulu fork (FuluForkTime=0), so e2e tests that hardcoded Electra1 as the expected genesis fork version need updating. https://claude.ai/code/session_01WL9ZgSDBYTcr1X91AYuPrU

Copilot AI reviewed Apr 16, 2026

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Comment thread state-transition/core/state_processor_forks.go

chatgpt-codex-connector bot reviewed Apr 16, 2026

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Comment thread state-transition/core/state_processor.go

Comment thread state-transition/core/state_processor_forks.go

claude added 3 commits April 16, 2026 12:04

fridrik01 self-requested a review April 19, 2026 15:52

fridrik01 approved these changes Apr 20, 2026

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calbera added 5 commits April 21, 2026 13:27

clarifying comment for hysteresis downward multiplier not using times…

3cdc138

…tamp

Merge branch 'claude/implement-brip-0008-pol-vnext-p043C' of github.c…

adeb522

…om:berachain/beacon-kit into claude/implement-brip-0008-pol-vnext-p043C

nit

b8bad56

fork ordering nit

4d88d47

Merge branch 'main' into claude/implement-brip-0008-pol-vnext-p043C

872e2dc

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feat(chain): implement BRIP-0008 hysteresis update for Fulu fork#3081

feat(chain): implement BRIP-0008 hysteresis update for Fulu fork#3081
calbera wants to merge 14 commits intomainfrom
claude/implement-brip-0008-pol-vnext-p043C

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	case version.EqualsOrIsAfter(fv, version.Fulu()):
	case version.Equals(fv, version.Fulu()):

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