diff --git a/commands_test.go b/commands_test.go
index cb01f7c..5927317 100644
--- a/commands_test.go
+++ b/commands_test.go
@@ -7,6 +7,8 @@ package blockchain
 
 import (
 	"context"
+	"errors"
+	"net"
 	"testing"
 	"time"
 
@@ -133,3 +135,72 @@ func TestRunChainSyncOnce_Bad_RespectsCancelledContext(t *testing.T) {
 	require.Error(t, err)
 	assert.Less(t, time.Since(start), 2*time.Second)
 }
+
+func TestRunChainSyncOnce_Bad_ReportsPeerIDReadError(t *testing.T) {
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	require.NoError(t, err)
+	defer listener.Close()
+
+	done := make(chan struct{})
+	defer close(done)
+	go func() {
+		conn, err := listener.Accept()
+		if err != nil {
+			return
+		}
+		defer conn.Close()
+		<-done
+	}()
+
+	oldReadPeerID := readPeerID
+	readPeerID = func([]byte) (int, error) {
+		return 0, errors.New("peer id failed")
+	}
+	defer func() {
+		readPeerID = oldReadPeerID
+	}()
+
+	err = runChainSyncOnce(context.Background(), nil, &config.ChainConfig{}, chain.SyncOptions{}, listener.Addr().String())
+	require.Error(t, err)
+	assert.ErrorContains(t, err, "read peer ID")
+	assert.ErrorContains(t, err, "peer id failed")
+}
+
+func TestRunChainSyncOnce_Bad_ReportsHeightLookupError(t *testing.T) {
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	require.NoError(t, err)
+	defer listener.Close()
+
+	done := make(chan struct{})
+	defer close(done)
+	go func() {
+		conn, err := listener.Accept()
+		if err != nil {
+			return
+		}
+		defer conn.Close()
+		<-done
+	}()
+
+	oldReadPeerID := readPeerID
+	readPeerID = func(buf []byte) (int, error) {
+		copy(buf, []byte{1, 2, 3, 4, 5, 6, 7, 8})
+		return len(buf), nil
+	}
+	defer func() {
+		readPeerID = oldReadPeerID
+	}()
+
+	oldChainHeight := chainHeight
+	chainHeight = func(*chain.Chain) (uint64, error) {
+		return 0, errors.New("height failed")
+	}
+	defer func() {
+		chainHeight = oldChainHeight
+	}()
+
+	err = runChainSyncOnce(context.Background(), nil, &config.ChainConfig{}, chain.SyncOptions{}, listener.Addr().String())
+	require.Error(t, err)
+	assert.ErrorContains(t, err, "read local height")
+	assert.ErrorContains(t, err, "height failed")
+}
diff --git a/sync_loop.go b/sync_loop.go
index abca123..136e3d0 100644
--- a/sync_loop.go
+++ b/sync_loop.go
@@ -22,6 +22,11 @@ import (
 	levin "dappco.re/go/core/p2p/node/levin"
 )
 
+var readPeerID = rand.Read
+var chainHeight = func(blockchain *chain.Chain) (uint64, error) {
+	return blockchain.Height()
+}
+
 func runChainSyncLoop(ctx context.Context, blockchain *chain.Chain, chainConfig *config.ChainConfig, hardForks []config.HardFork, seed string) {
 	opts := chain.SyncOptions{
 		VerifySignatures: false,
@@ -75,10 +80,15 @@ func runChainSyncOnce(ctx context.Context, blockchain *chain.Chain, chainConfig
 	levinConnection := levin.NewConnection(tcpConn)
 
 	var peerIDBuf [8]byte
-	rand.Read(peerIDBuf[:])
+	if _, err := readPeerID(peerIDBuf[:]); err != nil {
+		return coreerr.E("runChainSyncOnce", "read peer ID", err)
+	}
 	peerID := binary.LittleEndian.Uint64(peerIDBuf[:])
 
-	localHeight, _ := blockchain.Height()
+	localHeight, err := chainHeight(blockchain)
+	if err != nil {
+		return coreerr.E("runChainSyncOnce", "read local height", err)
+	}
 
 	handshakeReq := p2p.HandshakeRequest{
 		NodeData: p2p.NodeData{