diff --git a/node/derivation/config.go b/node/derivation/config.go
index 64cde744d..2f73092ce 100644
--- a/node/derivation/config.go
+++ b/node/derivation/config.go
@@ -156,6 +156,11 @@ func (c *Config) SetCliContext(ctx *cli.Context) error {
 		}
 	}
 
+	legacyValidatorMode := ctx.GlobalBool(flags.LegacyValidatorMode.Name)
+	if legacyValidatorMode {
+		log.Warn("--validator is deprecated; use --derivation.verify-mode=layer1")
+		c.VerifyMode = VerifyModeLayer1
+	}
 	if ctx.GlobalIsSet(flags.DerivationVerifyMode.Name) {
 		c.VerifyMode = ctx.GlobalString(flags.DerivationVerifyMode.Name)
 	}
diff --git a/node/derivation/config_test.go b/node/derivation/config_test.go
index e26ce5889..f18819784 100644
--- a/node/derivation/config_test.go
+++ b/node/derivation/config_test.go
@@ -1,8 +1,14 @@
 package derivation
 
 import (
+	"flag"
+	"path/filepath"
 	"strings"
 	"testing"
+
+	"github.com/urfave/cli"
+
+	"morph-l2/node/flags"
 )
 
 // SPEC-005 section 4.2 + 5.1 verify-mode dispatch tests. The mode is bound at
@@ -35,6 +41,31 @@ func TestVerifyMode_AcceptsExplicitModes(t *testing.T) {
 	}
 }
 
+func TestVerifyMode_LegacyValidatorAlias(t *testing.T) {
+	cfg := DefaultConfig()
+	if err := cfg.SetCliContext(newVerifyModeTestContext(t, map[string]string{
+		flags.LegacyValidatorMode.Name: "true",
+	})); err != nil {
+		t.Fatalf("legacy validator alias rejected: %v", err)
+	}
+	if cfg.VerifyMode != VerifyModeLayer1 {
+		t.Fatalf("legacy validator alias resolved to %q, want %q", cfg.VerifyMode, VerifyModeLayer1)
+	}
+}
+
+func TestVerifyMode_ExplicitModeOverridesLegacyValidatorAlias(t *testing.T) {
+	cfg := DefaultConfig()
+	if err := cfg.SetCliContext(newVerifyModeTestContext(t, map[string]string{
+		flags.LegacyValidatorMode.Name:  "true",
+		flags.DerivationVerifyMode.Name: VerifyModeLocal,
+	})); err != nil {
+		t.Fatalf("explicit verify-mode rejected: %v", err)
+	}
+	if cfg.VerifyMode != VerifyModeLocal {
+		t.Fatalf("explicit verify-mode resolved to %q, want %q", cfg.VerifyMode, VerifyModeLocal)
+	}
+}
+
 func TestVerifyMode_RejectsUnknown(t *testing.T) {
 	// "hybrid" was the old default; ensure post-removal it's rejected so
 	// stale operator configs fail loud rather than silently falling back to
@@ -66,3 +97,34 @@ func validateAndDefaultVerifyModeErr(t *testing.T, s string) error {
 	}
 	return err
 }
+
+func newVerifyModeTestContext(t *testing.T, values map[string]string) *cli.Context {
+	t.Helper()
+
+	flagSet := flag.NewFlagSet(t.Name(), flag.ContinueOnError)
+	for _, f := range []cli.Flag{
+		flags.LegacyValidatorMode,
+		flags.DerivationVerifyMode,
+		flags.L1BeaconAddr,
+		flags.L2EngineJWTSecret,
+	} {
+		f.Apply(flagSet)
+	}
+
+	defaults := map[string]string{
+		flags.L1BeaconAddr.Name:      "http://beacon.example",
+		flags.L2EngineJWTSecret.Name: filepath.Join(t.TempDir(), "jwt.hex"),
+	}
+	for name, value := range defaults {
+		if err := flagSet.Set(name, value); err != nil {
+			t.Fatalf("set default flag %s: %v", name, err)
+		}
+	}
+	for name, value := range values {
+		if err := flagSet.Set(name, value); err != nil {
+			t.Fatalf("set flag %s: %v", name, err)
+		}
+	}
+
+	return cli.NewContext(cli.NewApp(), flagSet, nil)
+}
diff --git a/node/flags/flags.go b/node/flags/flags.go
index 3747bf6ee..7ee931d48 100644
--- a/node/flags/flags.go
+++ b/node/flags/flags.go
@@ -156,6 +156,12 @@ var (
 		EnvVar: prefixEnvVar("MOCK_SEQUENCER"),
 	}
 
+	LegacyValidatorMode = cli.BoolFlag{
+		Name:   "validator",
+		Usage:  "Deprecated compatibility alias for --derivation.verify-mode=layer1",
+		EnvVar: prefixEnvVar("VALIDATOR"),
+	}
+
 	// derivation
 	RollupContractAddress = cli.StringFlag{
 		Name:   "derivation.rollupAddress",
@@ -368,6 +374,7 @@ var Flags = []cli.Flag{
 	DevSequencer,
 	TendermintConfigPath,
 	MockEnabled,
+	LegacyValidatorMode,
 
 	// derivation
 	RollupContractAddress,