diff --git a/extern/storage-sealing/precommit_batch.go b/extern/storage-sealing/precommit_batch.go
new file mode 100644
index 000000000..93846fbef
--- /dev/null
+++ b/extern/storage-sealing/precommit_batch.go
@@ -0,0 +1,298 @@
+package sealing
+
+import (
+	"bytes"
+	"context"
+	"sort"
+	"sync"
+	"time"
+
+	"github.com/ipfs/go-cid"
+	"golang.org/x/xerrors"
+
+	"github.com/filecoin-project/go-address"
+	"github.com/filecoin-project/go-state-types/abi"
+	"github.com/filecoin-project/go-state-types/big"
+	miner0 "github.com/filecoin-project/specs-actors/actors/builtin/miner"
+	miner5 "github.com/filecoin-project/specs-actors/v5/actors/builtin/miner"
+
+	"github.com/filecoin-project/lotus/api"
+	"github.com/filecoin-project/lotus/chain/actors/builtin/miner"
+)
+
+var (
+	// TODO: config
+
+	PreCommitBatchMax  uint64 = 100 // adjust based on real-world gas numbers, actors limit at 10k
+	PreCommitBatchMin  uint64 = 1
+	PreCommitBatchWait        = 5 * time.Minute
+)
+
+type PreCommitBatcherApi interface {
+	SendMsg(ctx context.Context, from, to address.Address, method abi.MethodNum, value, maxFee abi.TokenAmount, params []byte) (cid.Cid, error)
+	StateMinerInfo(context.Context, address.Address, TipSetToken) (miner.MinerInfo, error)
+	ChainHead(ctx context.Context) (TipSetToken, abi.ChainEpoch, error)
+}
+
+type PreCommitBatcher struct {
+	api       PreCommitBatcherApi
+	maddr     address.Address
+	mctx      context.Context
+	addrSel   AddrSel
+	feeCfg    FeeConfig
+	getConfig GetSealingConfigFunc
+
+	deadlines map[abi.SectorNumber]time.Time
+	todo      map[abi.SectorNumber]*miner0.SectorPreCommitInfo
+	waiting   map[abi.SectorNumber][]chan cid.Cid
+
+	notify, stop, stopped chan struct{}
+	force                 chan chan *cid.Cid
+	lk                    sync.Mutex
+}
+
+func NewPreCommitBatcher(mctx context.Context, maddr address.Address, api PreCommitBatcherApi, addrSel AddrSel, feeCfg FeeConfig, getConfig GetSealingConfigFunc) *PreCommitBatcher {
+	b := &PreCommitBatcher{
+		api:       api,
+		maddr:     maddr,
+		mctx:      mctx,
+		addrSel:   addrSel,
+		feeCfg:    feeCfg,
+		getConfig: getConfig,
+
+		deadlines: map[abi.SectorNumber]time.Time{},
+		todo:      map[abi.SectorNumber]*miner0.SectorPreCommitInfo{},
+		waiting:   map[abi.SectorNumber][]chan cid.Cid{},
+
+		notify:  make(chan struct{}, 1),
+		force:   make(chan chan *cid.Cid),
+		stop:    make(chan struct{}),
+		stopped: make(chan struct{}),
+	}
+
+	go b.run()
+
+	return b
+}
+
+func (b *PreCommitBatcher) run() {
+	var forceRes chan *cid.Cid
+	var lastMsg *cid.Cid
+
+	cfg, err := b.getConfig()
+	if err != nil {
+		panic(err)
+	}
+
+	for {
+		if forceRes != nil {
+			forceRes <- lastMsg
+			forceRes = nil
+		}
+		lastMsg = nil
+
+		var sendAboveMax, sendAboveMin bool
+		select {
+		case <-b.stop:
+			close(b.stopped)
+			return
+		case <-b.notify:
+			sendAboveMax = true
+		case <-time.After(b.batchWait(cfg.PreCommitBatchWait, cfg.PreCommitBatchSlack)):
+			sendAboveMin = true
+		case fr := <-b.force: // user triggered
+			forceRes = fr
+		}
+
+		var err error
+		lastMsg, err = b.processBatch(sendAboveMax, sendAboveMin)
+		if err != nil {
+			log.Warnw("TerminateBatcher processBatch error", "error", err)
+		}
+	}
+}
+
+func (b *PreCommitBatcher) batchWait(maxWait, slack time.Duration) time.Duration {
+	now := time.Now()
+
+	b.lk.Lock()
+	defer b.lk.Unlock()
+
+	var deadline time.Time
+	for sn := range b.todo {
+		sectorDeadline := b.deadlines[sn]
+		if deadline.IsZero() || (!sectorDeadline.IsZero() && sectorDeadline.Before(deadline)) {
+			deadline = sectorDeadline
+		}
+	}
+	for sn := range b.waiting {
+		sectorDeadline := b.deadlines[sn]
+		if deadline.IsZero() || (!sectorDeadline.IsZero() && sectorDeadline.Before(deadline)) {
+			deadline = sectorDeadline
+		}
+	}
+
+	if deadline.IsZero() {
+		return maxWait
+	}
+
+	deadline = deadline.Add(-slack)
+	if deadline.Before(now) {
+		return time.Nanosecond // can't return 0
+	}
+
+	wait := deadline.Sub(now)
+	if wait > maxWait {
+		wait = maxWait
+	}
+
+	return wait
+}
+
+func (b *PreCommitBatcher) processBatch(notif, after bool) (*cid.Cid, error) {
+	b.lk.Lock()
+	defer b.lk.Unlock()
+	params := miner5.PreCommitSectorBatchParams{}
+
+	total := len(b.todo)
+	if total == 0 {
+		return nil, nil // nothing to do
+	}
+
+	cfg, err := b.getConfig()
+	if err != nil {
+		return nil, xerrors.Errorf("getting config: %w", err)
+	}
+
+	if notif && total < cfg.MaxPreCommitBatch {
+		return nil, nil
+	}
+
+	if after && total < cfg.MinPreCommitBatch {
+		return nil, nil
+	}
+
+	for _, p := range b.todo {
+		params.Sectors = append(params.Sectors, p)
+	}
+
+	enc := new(bytes.Buffer)
+	if err := params.MarshalCBOR(enc); err != nil {
+		return nil, xerrors.Errorf("couldn't serialize PreCommitSectorBatchParams: %w", err)
+	}
+
+	mi, err := b.api.StateMinerInfo(b.mctx, b.maddr, nil)
+	if err != nil {
+		return nil, xerrors.Errorf("couldn't get miner info: %w", err)
+	}
+
+	from, _, err := b.addrSel(b.mctx, mi, api.PreCommitAddr, b.feeCfg.MaxPreCommitGasFee, b.feeCfg.MaxPreCommitGasFee)
+	if err != nil {
+		return nil, xerrors.Errorf("no good address found: %w", err)
+	}
+
+	mcid, err := b.api.SendMsg(b.mctx, from, b.maddr, miner.Methods.PreCommitSectorBatch, big.Zero(), b.feeCfg.MaxPreCommitGasFee, enc.Bytes())
+	if err != nil {
+		return nil, xerrors.Errorf("sending message failed: %w", err)
+	}
+
+	log.Infow("Sent ProveCommitAggregate message", "cid", mcid, "from", from, "sectors", total)
+
+	for _, sector := range params.Sectors {
+		sn := sector.SectorNumber
+
+		for _, ch := range b.waiting[sn] {
+			ch <- mcid // buffered
+		}
+		delete(b.waiting, sn)
+		delete(b.todo, sn)
+		delete(b.deadlines, sn)
+	}
+
+	return &mcid, nil
+}
+
+// register PreCommit, wait for batch message, return message CID
+func (b *PreCommitBatcher) AddPreCommit(ctx context.Context, s SectorInfo, in *miner0.SectorPreCommitInfo) (mcid cid.Cid, err error) {
+	_, curEpoch, err := b.api.ChainHead(b.mctx)
+	if err != nil {
+		log.Errorf("getting chain head: %s", err)
+		return cid.Undef, nil
+	}
+
+	sn := s.SectorNumber
+
+	b.lk.Lock()
+	b.deadlines[sn] = getSectorDeadline(curEpoch, s)
+	b.todo[sn] = in
+
+	sent := make(chan cid.Cid, 1)
+	b.waiting[sn] = append(b.waiting[sn], sent)
+
+	select {
+	case b.notify <- struct{}{}:
+	default: // already have a pending notification, don't need more
+	}
+	b.lk.Unlock()
+
+	select {
+	case c := <-sent:
+		return c, nil
+	case <-ctx.Done():
+		return cid.Undef, ctx.Err()
+	}
+}
+
+func (b *PreCommitBatcher) Flush(ctx context.Context) (*cid.Cid, error) {
+	resCh := make(chan *cid.Cid, 1)
+	select {
+	case b.force <- resCh:
+		select {
+		case res := <-resCh:
+			return res, nil
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		}
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+}
+
+func (b *PreCommitBatcher) Pending(ctx context.Context) ([]abi.SectorID, error) {
+	b.lk.Lock()
+	defer b.lk.Unlock()
+
+	mid, err := address.IDFromAddress(b.maddr)
+	if err != nil {
+		return nil, err
+	}
+
+	res := make([]abi.SectorID, 0)
+	for _, s := range b.todo {
+		res = append(res, abi.SectorID{
+			Miner:  abi.ActorID(mid),
+			Number: s.SectorNumber,
+		})
+	}
+
+	sort.Slice(res, func(i, j int) bool {
+		if res[i].Miner != res[j].Miner {
+			return res[i].Miner < res[j].Miner
+		}
+
+		return res[i].Number < res[j].Number
+	})
+
+	return res, nil
+}
+
+func (b *PreCommitBatcher) Stop(ctx context.Context) error {
+	close(b.stop)
+
+	select {
+	case <-b.stopped:
+		return nil
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+}