From b97936385800db5eb5bf4cf464e9bc4cc1998201 Mon Sep 17 00:00:00 2001
From: Alberto Benegiamo <abear@berachain.com>
Date: Fri, 13 Dec 2024 14:31:39 -0500
Subject: [PATCH] fix(state-transition): make `EffectiveBalance` update
 backward compatible (#2261)

---
 .../core/state_processor_staking.go           | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/state-transition/core/state_processor_staking.go b/state-transition/core/state_processor_staking.go
index 4ad29f238e..b7e62de497 100644
--- a/state-transition/core/state_processor_staking.go
+++ b/state-transition/core/state_processor_staking.go
@@ -22,6 +22,7 @@ package core
 
 import (
 	"github.com/berachain/beacon-kit/config/spec"
+	"github.com/berachain/beacon-kit/consensus-types/types"
 	"github.com/berachain/beacon-kit/errors"
 	"github.com/berachain/beacon-kit/primitives/common"
 	"github.com/berachain/beacon-kit/primitives/math"
@@ -119,6 +120,34 @@ func (sp *StateProcessor[
 		return sp.createValidator(st, dep)
 	}
 
+	// The validator already exist and we need to update its balance.
+	// EffectiveBalance must be updated in processEffectiveBalanceUpdates
+	// However before BoonetFork2Height we mistakenly update EffectiveBalance
+	// every slot. We must preserve backward compatibility so we special case
+	// Boonet to allow proper bootstrapping.
+	slot, err := st.GetSlot()
+	if err != nil {
+		return err
+	}
+	if sp.cs.DepositEth1ChainID() == spec.BoonetEth1ChainID &&
+		slot < math.U64(spec.BoonetFork2Height) {
+		var val ValidatorT
+		val, err = st.ValidatorByIndex(idx)
+		if err != nil {
+			return err
+		}
+
+		updatedBalance := types.ComputeEffectiveBalance(
+			val.GetEffectiveBalance()+dep.GetAmount(),
+			math.Gwei(sp.cs.EffectiveBalanceIncrement()),
+			math.Gwei(sp.cs.MaxEffectiveBalance(false)),
+		)
+		val.SetEffectiveBalance(updatedBalance)
+		if err = st.UpdateValidatorAtIndex(idx, val); err != nil {
+			return err
+		}
+	}
+
 	// if validator exist, just update its balance
 	if err = st.IncreaseBalance(idx, dep.GetAmount()); err != nil {
 		return err