fix(evm): don't create single sequencer for non-aggregator nodes

apps/evm/cmd/run.go

@@ -160,6 +160,12 @@ func createSequencer(
 	daClient block.FullDAClient,
 	executor execution.Executor,
 ) (coresequencer.Sequencer, error) {
+	// Only aggregators and promotable nodes need a sequencer; promotable
+	// followers must have one ready before they are promoted to proposer.
+	if !nodeConfig.Node.Aggregator && !nodeConfig.Node.Promotable {
+		return nil, nil
+	}
+
 	if nodeConfig.Node.BasedSequencer {
 		// Based sequencer mode - fetch transactions only from DA
 		if !nodeConfig.Node.Aggregator {

apps/testapp/cmd/run.go

@@ -113,7 +113,9 @@ func createSequencer(
 	genesis genesis.Genesis,
 	executor execution.Executor,
 ) (coresequencer.Sequencer, error) {
-	if !nodeConfig.Node.Aggregator {
+	// Only aggregators and promotable nodes need a sequencer; promotable
+	// followers must have one ready before they are promoted to proposer.
+	if !nodeConfig.Node.Aggregator && !nodeConfig.Node.Promotable {
 		return nil, nil
 	}
 

pkg/cmd/run_node.go

@@ -48,8 +48,8 @@ func ParseStartConfig(cmd *cobra.Command) (rollconf.Config, error) {
 	if err != nil {
 		return rollconf.Config{}, err
 	}
-	if nodeConfig.Node.Aggregator && nodeConfig.GetDAAddress() == "" {
-		return rollconf.Config{}, fmt.Errorf("DA address is required when aggregator mode is enabled")
+	if (nodeConfig.Node.Aggregator || nodeConfig.Node.Promotable) && nodeConfig.GetDAAddress() == "" {
+		return rollconf.Config{}, fmt.Errorf("DA address is required when aggregator or promotable mode is enabled")
 	}
 
 	return nodeConfig, nil

pkg/cmd/run_node_test.go

@@ -175,20 +175,22 @@ func TestAggregatorFlagInvariants(t *testing.T) {
 }
 
 func TestParseStartConfig_AggregatorRequiresDAAddress(t *testing.T) {
-	executor, sequencer, keyProvider, nodeKey, ds, stopDAHeightTicker := createTestComponents(context.Background(), t)
-	defer stopDAHeightTicker()
+	for _, flag := range []string{"--rollkit.node.aggregator", "--rollkit.node.promotable"} {
+		executor, sequencer, keyProvider, nodeKey, ds, stopDAHeightTicker := createTestComponents(context.Background(), t)
+		defer stopDAHeightTicker()
 
-	nodeConfig := rollconf.DefaultConfig()
-	nodeConfig.RootDir = t.TempDir()
+		nodeConfig := rollconf.DefaultConfig()
+		nodeConfig.RootDir = t.TempDir()
 
-	cmd := newRunNodeCmd(t.Context(), executor, sequencer, keyProvider, nodeKey, ds, nodeConfig)
-	require.NoError(t, cmd.ParseFlags([]string{"start", "--rollkit.node.aggregator"}))
+		cmd := newRunNodeCmd(t.Context(), executor, sequencer, keyProvider, nodeKey, ds, nodeConfig)
+		require.NoError(t, cmd.ParseFlags([]string{"start", flag}))
 
-	_, err := ParseConfig(cmd)
-	require.NoError(t, err)
+		_, err := ParseConfig(cmd)
+		require.NoError(t, err)
 
-	_, err = ParseStartConfig(cmd)
-	require.EqualError(t, err, "DA address is required when aggregator mode is enabled")
+		_, err = ParseStartConfig(cmd)
+		require.EqualError(t, err, "DA address is required when aggregator or promotable mode is enabled")
+	}
 }
 
 func TestPromotableFlagInvariants(t *testing.T) {

pkg/sequencers/single/sequencer.go

@@ -78,6 +78,10 @@ func NewSequencer(
 	genesis genesis.Genesis,
 	executor execution.Executor,
 ) (*Sequencer, error) {
+	if daClient == nil {
+		return nil, errors.New("single sequencer requires a DA client")
+	}
+
 	s := &Sequencer{
 		db:               db,
 		logger:           logger,

pkg/sequencers/single/sequencer_test.go

@@ -114,6 +114,13 @@ func newTestSequencer(t *testing.T, db ds.Batching, daClient block.FullDAClient)
 	return seq
 }
 
+func TestNewSequencer_NilDAClient(t *testing.T) {
+	mockExec := createDefaultMockExecutor(t)
+	seq, err := NewSequencer(zerolog.Nop(), ds.NewMapDatastore(), nil, config.DefaultConfig(), []byte("test"), 1000, genesis.Genesis{}, mockExec)
+	require.Error(t, err)
+	require.Nil(t, seq)
+}
+
 func TestSequencer_SubmitBatchTxs(t *testing.T) {
 	dummyDA := newDummyDA(100_000_000)
 	db := ds.NewMapDatastore()