diff --git a/app/app.go b/app/app.go
index d335cc432d..99e3e57174 100644
--- a/app/app.go
+++ b/app/app.go
@@ -1911,12 +1911,16 @@ func (app *App) executeEVMTxWithGigaExecutor(ctx sdk.Context, msg *evmtypes.MsgE
 		vmError = execResult.Err.Error()
 	}
 
-	// Create core.Message from ethTx for WriteReceipt
-	// WriteReceipt needs msg for GasPrice, To, From, Data, Nonce fields
+	// Create core.Message from ethTx for WriteReceipt.
+	// GasPrice must be the EIP-1559 effective gas price (min(baseFee+tip,
+	// maxFee)) — that's what the chain actually charges (see line 1866)
+	// and what the receipt's EffectiveGasPrice field needs to report.
+	// ethTx.GasPrice() returns GasFeeCap for dynamic-fee txs, which puts
+	// the wrong value on the receipt and breaks EIP-1559 clients.
 	evmMsg := &core.Message{
 		Nonce:     ethTx.Nonce(),
 		GasLimit:  ethTx.Gas(),
-		GasPrice:  ethTx.GasPrice(),
+		GasPrice:  effectiveGasPrice,
 		GasFeeCap: ethTx.GasFeeCap(),
 		GasTipCap: ethTx.GasTipCap(),
 		To:        ethTx.To(),
diff --git a/giga/deps/xevm/keeper/receipt_test.go b/giga/deps/xevm/keeper/receipt_test.go
index a11fdf1584..a6ea19e48f 100644
--- a/giga/deps/xevm/keeper/receipt_test.go
+++ b/giga/deps/xevm/keeper/receipt_test.go
@@ -1,11 +1,14 @@
 package keeper_test
 
 import (
+	"math/big"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core"
 	ethtypes "github.com/ethereum/go-ethereum/core/types"
 	testkeeper "github.com/sei-protocol/sei-chain/giga/deps/testutil/keeper"
+	"github.com/sei-protocol/sei-chain/giga/deps/xevm/state"
 	"github.com/sei-protocol/sei-chain/giga/deps/xevm/types"
 	sdk "github.com/sei-protocol/sei-chain/sei-cosmos/types"
 	"github.com/stretchr/testify/require"
@@ -39,3 +42,49 @@ func TestDeleteTransientReceipt(t *testing.T) {
 	require.Nil(t, receipt)
 	require.Equal(t, "receipt not found", err.Error())
 }
+
+// TestWriteReceiptStoresMsgGasPriceAsEffectiveGasPrice documents the contract
+// between WriteReceipt and its caller for EIP-1559 dynamic-fee txs:
+// receipt.EffectiveGasPrice is taken from msg.GasPrice verbatim, so the caller
+// is responsible for setting msg.GasPrice = min(baseFee + tipCap, feeCap)
+// (the actual effective gas price the chain charged).
+//
+// The bug this guards against: passing ethTx.GasPrice() into msg for a
+// dynamic-fee tx returns GasFeeCap (i.e., maxFee) — the receipt would then
+// report maxFee even when the tx actually paid baseFee+tip < maxFee, breaking
+// EIP-1559 RPC semantics for clients (e.g. ethers, hardhat-ethers).
+func TestWriteReceiptStoresMsgGasPriceAsEffectiveGasPrice(t *testing.T) {
+	k, ctx := testkeeper.MockEVMKeeper(t)
+	stateDB := state.NewDBImpl(ctx, k, false)
+	txHash := common.HexToHash("0xdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeef")
+
+	// Scenario: tip=1gwei, maxFee=10gwei, baseFee=1gwei →
+	// effectiveGasPrice = baseFee + tip = 2gwei (additive branch).
+	const (
+		effectiveGasPrice uint64 = 2_000_000_000  // 2 gwei
+		feeCap            uint64 = 10_000_000_000 // 10 gwei
+		tipCap            uint64 = 1_000_000_000  // 1 gwei
+		gasUsed           uint64 = 21_000
+	)
+
+	msg := &core.Message{
+		Nonce:     0,
+		GasLimit:  gasUsed,
+		GasPrice:  new(big.Int).SetUint64(effectiveGasPrice),
+		GasFeeCap: new(big.Int).SetUint64(feeCap),
+		GasTipCap: new(big.Int).SetUint64(tipCap),
+		To:        nil,
+		Value:     big.NewInt(0),
+		From:      common.HexToAddress("0x000000000000000000000000000000000000beef"),
+	}
+
+	r, err := k.WriteReceipt(ctx, stateDB, msg, uint32(ethtypes.DynamicFeeTxType), txHash, gasUsed, "")
+	require.NoError(t, err)
+	require.NotNil(t, r)
+	require.Equal(t, effectiveGasPrice, r.EffectiveGasPrice,
+		"receipt.EffectiveGasPrice must equal msg.GasPrice; if the caller passes "+
+			"ethTx.GasPrice() for a dynamic-fee tx, the receipt would wrongly report GasFeeCap (%d) "+
+			"instead of the EIP-1559 effective gas price (%d)", feeCap, effectiveGasPrice)
+	require.Equal(t, uint32(ethtypes.ReceiptStatusSuccessful), r.Status)
+	require.Equal(t, gasUsed, r.GasUsed)
+}