core/txpool: guard nil head subscription

core/txpool/txpool.go

@@ -152,7 +152,9 @@ func (p *TxPool) loop(head *types.Header) {
 		newHeadCh  = make(chan core.ChainHeadEvent)
 		newHeadSub = p.chain.SubscribeChainHeadEvent(newHeadCh)
 	)
-	defer newHeadSub.Unsubscribe()
+	if newHeadSub != nil {
+		defer newHeadSub.Unsubscribe()
+	}
 
 	// Track the previous and current head to feed to an idle reset
 	var (

core/txpool/txpool_test.go

@@ -0,0 +1,76 @@
+// Copyright 2026 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library 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 Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package txpool
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/event"
+	"github.com/ethereum/go-ethereum/params"
+)
+
+type nilHeadSubChain struct{}
+
+func (nilHeadSubChain) Config() *params.ChainConfig { return params.TestChainConfig }
+
+func (nilHeadSubChain) CurrentBlock() *types.Header { return &types.Header{} }
+
+func (nilHeadSubChain) SubscribeChainHeadEvent(chan<- core.ChainHeadEvent) event.Subscription {
+	return nil
+}
+
+func (nilHeadSubChain) StateAt(common.Hash) (*state.StateDB, error) {
+	return nil, errors.New("not implemented")
+}
+
+func TestTxPoolLoopNilHeadSubscription(t *testing.T) {
+	t.Parallel()
+
+	pool := &TxPool{
+		chain: nilHeadSubChain{},
+		quit:  make(chan chan error),
+		term:  make(chan struct{}),
+		sync:  make(chan chan error),
+	}
+	go pool.loop(nil)
+
+	errc := make(chan error, 1)
+	select {
+	case pool.quit <- errc:
+	case <-time.After(time.Second):
+		t.Fatal("timed out waiting for txpool loop to accept quit signal")
+	}
+	select {
+	case err := <-errc:
+		if err != nil {
+			t.Fatalf("unexpected close error: %v", err)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("timed out waiting for txpool loop to stop")
+	}
+	select {
+	case <-pool.term:
+	case <-time.After(time.Second):
+		t.Fatal("timed out waiting for txpool loop termination")
+	}
+}