cmd/geth, eth/ethconfig: preserve zero engine reorg depth

cmd/geth/config_test.go

@@ -0,0 +1,40 @@
+// Copyright 2026 The go-ethereum Authors
+// This file is part of go-ethereum.
+//
+// go-ethereum is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// go-ethereum is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
+
+package main
+
+import (
+	"testing"
+
+	"github.com/ethereum/go-ethereum/eth/ethconfig"
+)
+
+func TestEngineMaxReorgDepthConfigRoundTrip(t *testing.T) {
+	original := ethconfig.Defaults
+	original.EngineMaxReorgDepth = 0
+
+	encoded, err := tomlSettings.Marshal(&original)
+	if err != nil {
+		t.Fatalf("failed to encode config: %v", err)
+	}
+	decoded := ethconfig.Defaults
+	if err := tomlSettings.Unmarshal(encoded, &decoded); err != nil {
+		t.Fatalf("failed to decode config: %v", err)
+	}
+	if decoded.EngineMaxReorgDepth != original.EngineMaxReorgDepth {
+		t.Fatalf("reorg depth changed across config round-trip: have %d, want %d", decoded.EngineMaxReorgDepth, original.EngineMaxReorgDepth)
+	}
+}

eth/ethconfig/config.go

@@ -207,7 +207,7 @@ type Config struct {
 	// EngineMaxReorgDepth is the maximum depth the chain head can be rewound
 	// to an already-canonical ancestor by engine API forkchoiceUpdated calls
 	// (0 = no limit).
-	EngineMaxReorgDepth uint64 `toml:",omitempty"`
+	EngineMaxReorgDepth uint64
 
 	// OverrideOsaka (TODO: remove after the fork)
 	OverrideOsaka *uint64 `toml:",omitempty"`

eth/ethconfig/gen_config.go

@@ -63,7 +63,7 @@ func (c Config) MarshalTOML() (interface{}, error) {
 		RPCGasCap               uint64
 		RPCEVMTimeout           time.Duration
 		RPCTxFeeCap             float64
-		EngineMaxReorgDepth     uint64        `toml:",omitempty"`
+		EngineMaxReorgDepth     uint64
 		OverrideOsaka           *uint64       `toml:",omitempty"`
 		OverrideAmsterdam       *uint64       `toml:",omitempty"`
 		OverrideBPO1            *uint64       `toml:",omitempty"`
@@ -181,7 +181,7 @@ func (c *Config) UnmarshalTOML(unmarshal func(interface{}) error) error {
 		RPCGasCap               *uint64
 		RPCEVMTimeout           *time.Duration
 		RPCTxFeeCap             *float64
-		EngineMaxReorgDepth     *uint64        `toml:",omitempty"`
+		EngineMaxReorgDepth     *uint64
 		OverrideOsaka           *uint64        `toml:",omitempty"`
 		OverrideAmsterdam       *uint64        `toml:",omitempty"`
 		OverrideBPO1            *uint64        `toml:",omitempty"`