diff --git a/ais/plstcx.go b/ais/plstcx.go
index 85c47af24e9..2c5d33095b5 100644
--- a/ais/plstcx.go
+++ b/ais/plstcx.go
@@ -42,7 +42,7 @@ type (
 		cnt     int
 		lsmsg   apc.LsoMsg
 		altmsg  apc.ActMsg
-		tcomsg  cmn.TCObjsMsg
+		tcomsg  cmn.TCOMsg
 		stopped atomic.Bool
 	}
 )
diff --git a/ais/proxy.go b/ais/proxy.go
index dcd55a48474..380de59b8ff 100644
--- a/ais/proxy.go
+++ b/ais/proxy.go
@@ -1373,7 +1373,7 @@ func (p *proxy) _bckpost(w http.ResponseWriter, r *http.Request, msg *apc.ActMsg
 		}
 	case apc.ActCopyObjects, apc.ActETLObjects:
 		var (
-			tcomsg = &cmn.TCObjsMsg{}
+			tcomsg = &cmn.TCOMsg{}
 			bckTo  *meta.Bck
 			ecode  int
 			eq     bool
diff --git a/ais/prxtxn.go b/ais/prxtxn.go
index 6146f3c6fa6..c038bdef9c7 100644
--- a/ais/prxtxn.go
+++ b/ais/prxtxn.go
@@ -646,7 +646,7 @@ func (p *proxy) tcb(bckFrom, bckTo *meta.Bck, msg *apc.ActMsg, dryRun bool) (xid
 }
 
 // transform or copy a list or a range of objects
-func (p *proxy) tcobjs(bckFrom, bckTo *meta.Bck, config *cmn.Config, msg *apc.ActMsg, tcomsg *cmn.TCObjsMsg) (string, error) {
+func (p *proxy) tcobjs(bckFrom, bckTo *meta.Bck, config *cmn.Config, msg *apc.ActMsg, tcomsg *cmn.TCOMsg) (string, error) {
 	// 1. prep
 	var (
 		_, existsTo = p.owner.bmd.get().Get(bckTo) // cleanup on fail: destroy if created
diff --git a/ais/test/cp_multiobj_test.go b/ais/test/cp_multiobj_test.go
index 1a60bf1e14b..d7958d7379e 100644
--- a/ais/test/cp_multiobj_test.go
+++ b/ais/test/cp_multiobj_test.go
@@ -78,7 +78,7 @@ func TestCopyMultiObjSimple(t *testing.T) {
 		template := "test/a-" + fmt.Sprintf("{%04d..%04d}", rangeStart, rangeStart+copyCnt-1)
 		tlog.Logf("[%s] %s => %s\n", template, bckFrom.Cname(""), bckTo.Cname(""))
 
-		msg := cmn.TCObjsMsg{ToBck: bckTo}
+		msg := cmn.TCOMsg{ToBck: bckTo}
 		msg.Template = template
 		xid, err = api.CopyMultiObj(baseParams, bckFrom, &msg)
 		tassert.CheckFatal(t, err)
@@ -190,7 +190,7 @@ func testCopyMobj(t *testing.T, bck *meta.Bck) {
 						var (
 							err error
 							xid string
-							msg = cmn.TCObjsMsg{ToBck: bckTo}
+							msg = cmn.TCOMsg{ToBck: bckTo}
 						)
 						msg.ObjNames = list
 						if m.bck.IsRemote() && test.evictRemoteSrc {
@@ -224,7 +224,7 @@ func testCopyMobj(t *testing.T, bck *meta.Bck) {
 							err      error
 							xid      string
 							template = fmt.Sprintf(fmtRange, m.prefix, start, start+numToCopy-1)
-							msg      = cmn.TCObjsMsg{ToBck: bckTo}
+							msg      = cmn.TCOMsg{ToBck: bckTo}
 						)
 						msg.Template = template
 						if m.bck.IsRemote() && test.evictRemoteSrc {
diff --git a/ais/test/etl_cp_multiobj_test.go b/ais/test/etl_cp_multiobj_test.go
index 9c6f8e6cf3d..f8baddaa409 100644
--- a/ais/test/etl_cp_multiobj_test.go
+++ b/ais/test/etl_cp_multiobj_test.go
@@ -146,7 +146,7 @@ func testETLMultiObj(t *testing.T, etlName string, bckFrom, bckTo cmn.Bck, fileR
 		objList        = pt.ToSlice()
 		objCnt         = len(objList)
 		requestTimeout = 30 * time.Second
-		tcomsg         = cmn.TCObjsMsg{ToBck: bckTo}
+		tcomsg         = cmn.TCOMsg{ToBck: bckTo}
 	)
 	tcomsg.Transform.Name = etlName
 	tcomsg.Transform.Timeout = cos.Duration(requestTimeout)
diff --git a/ais/tgttxn.go b/ais/tgttxn.go
index c15d7b4aef1..b9cd765f583 100644
--- a/ais/tgttxn.go
+++ b/ais/tgttxn.go
@@ -123,7 +123,7 @@ func (t *target) txnHandler(w http.ResponseWriter, r *http.Request) {
 	case apc.ActCopyObjects, apc.ActETLObjects:
 		var (
 			dp     core.DP
-			tcomsg = &cmn.TCObjsMsg{}
+			tcomsg = &cmn.TCOMsg{}
 		)
 		if err := cos.MorphMarshal(c.msg.Value, tcomsg); err != nil {
 			t.writeErrf(w, r, cmn.FmtErrMorphUnmarshal, t.si, msg.Action, c.msg.Value, err)
@@ -632,7 +632,7 @@ func (t *target) _tcbBegin(c *txnSrv, msg *apc.TCBMsg, dp core.DP) (err error) {
 // Two IDs:
 // - TxnUUID: transaction (txn) ID
 // - xid: xaction ID (will have "tco-" prefix)
-func (t *target) tcobjs(c *txnSrv, msg *cmn.TCObjsMsg, dp core.DP) (xid string, _ error) {
+func (t *target) tcobjs(c *txnSrv, msg *cmn.TCOMsg, dp core.DP) (xid string, _ error) {
 	switch c.phase {
 	case apc.ActBegin:
 		var (
diff --git a/ais/tgtxact.go b/ais/tgtxact.go
index c274eabe970..12425550e03 100644
--- a/ais/tgtxact.go
+++ b/ais/tgtxact.go
@@ -268,7 +268,7 @@ func (t *target) httpxpost(w http.ResponseWriter, r *http.Request) {
 		err    error
 		xctn   core.Xact
 		amsg   *apc.ActMsg
-		tcomsg cmn.TCObjsMsg
+		tcomsg cmn.TCOMsg
 	)
 	if amsg, err = t.readActionMsg(w, r); err != nil {
 		return
diff --git a/ais/txn.go b/ais/txn.go
index 967644738cd..20befea68ac 100644
--- a/ais/txn.go
+++ b/ais/txn.go
@@ -113,7 +113,7 @@ type (
 	}
 	txnTCObjs struct {
 		xtco *xs.XactTCObjs
-		msg  *cmn.TCObjsMsg
+		msg  *cmn.TCOMsg
 		txnBckBase
 	}
 	txnECEncode struct {
@@ -581,7 +581,7 @@ func (txn *txnTCB) String() string {
 // txnTCObjs //
 ///////////////
 
-func newTxnTCObjs(c *txnSrv, bckFrom *meta.Bck, xtco *xs.XactTCObjs, msg *cmn.TCObjsMsg) (txn *txnTCObjs) {
+func newTxnTCObjs(c *txnSrv, bckFrom *meta.Bck, xtco *xs.XactTCObjs, msg *cmn.TCOMsg) (txn *txnTCObjs) {
 	txn = &txnTCObjs{xtco: xtco, msg: msg}
 	txn.init(bckFrom)
 	txn.fillFromCtx(c)
diff --git a/api/apc/blob.go b/api/apc/blob.go
index 51826988e84..d01eb697c47 100644
--- a/api/apc/blob.go
+++ b/api/apc/blob.go
@@ -16,12 +16,14 @@ import (
 const _bldl = "blob-downloader"
 
 type BlobMsg struct {
-	ChunkSize  int64 `json:"chunk-size"`
-	FullSize   int64 `json:"full-size"`
-	NumWorkers int   `json:"num-workers"`
-	LatestVer  bool  `json:"latest-ver"`
+	ChunkSize  int64 `json:"chunk-size"`  // as in: chunk size
+	FullSize   int64 `json:"full-size"`   // user-specified (full) size of the object to download
+	NumWorkers int   `json:"num-workers"` // number of concurrent downloading workers (readers); `dfltNumWorkers` when zero
+	LatestVer  bool  `json:"latest-ver"`  // when true and in-cluster: check with remote whether (deleted | version-changed)
 }
 
+// in re LatestVer, see also: `QparamLatestVer`, 'versioning.validate_warm_get'
+
 // using textproto.CanonicalMIMEHeaderKey() to check presence -
 // if a given key is present and is an empty string, it's an error
 func (msg *BlobMsg) FromHeader(hdr http.Header) error {
diff --git a/api/apc/multiobj.go b/api/apc/multiobj.go
index 8b40d277732..afcd340d0fd 100644
--- a/api/apc/multiobj.go
+++ b/api/apc/multiobj.go
@@ -4,50 +4,56 @@
  */
 package apc
 
+// (common for all multi-object operations)
 type (
 	// List of object names _or_ a template specifying { optional Prefix, zero or more Ranges }
 	ListRange struct {
 		Template string   `json:"template"`
 		ObjNames []string `json:"objnames"`
 	}
-	PrefetchMsg struct {
-		ListRange
-		BlobThreshold   int64 `json:"blob-threshold"`
-		ContinueOnError bool  `json:"coer"`
-		LatestVer       bool  `json:"latest-ver"` // see also: QparamLatestVer, 'versioning.validate_warm_get'
-	}
-
-	// ArchiveMsg contains the parameters (all except the destination bucket)
-	// for archiving mutiple objects as one of the supported archive.FileExtensions types
-	// at the specified (bucket) destination.
-	// See also: api.PutApndArchArgs
-	// --------------------  terminology   ---------------------
-	// here and elsewhere "archive" is any (.tar, .tgz/.tar.gz, .zip, .tar.lz4) formatted object.
-	ArchiveMsg struct {
-		TxnUUID     string `json:"-"`        // internal use
-		FromBckName string `json:"-"`        // ditto
-		ArchName    string `json:"archname"` // one of the archive.FileExtensions
-		Mime        string `json:"mime"`     // user-specified mime type (NOTE: takes precedence if defined)
-		ListRange
-		BaseNameOnly    bool `json:"bnonly"` // only extract the base name of objects as names of archived objects
-		InclSrcBname    bool `json:"isbn"`   // include source bucket name into the names of archived objects
-		AppendIfExists  bool `json:"aate"`   // adding a list or a range of objects to an existing archive
-		ContinueOnError bool `json:"coer"`   // on err, keep running arc xaction in a any given multi-object transaction
-	}
-	//  Multi-object copy & transform (see also: TCBMsg)
-	TCObjsMsg struct {
-		ListRange
-		TxnUUID string // (plstcx client, internal use)
-		TCBMsg
-		ContinueOnError bool `json:"coer"`
-	}
 )
 
-///////////////
-// ListRange //
-///////////////
-
-// empty `ListRange{}` implies operating on an entire bucket ("all objects in the source bucket")
+// [NOTE]
+// - empty `ListRange{}` implies operating on an entire bucket ("all objects in the source bucket")
+// - in re `LatestVer`, see related: `QparamLatestVer`, 'versioning.validate_warm_get'
 
 func (lrm *ListRange) IsList() bool      { return len(lrm.ObjNames) > 0 }
 func (lrm *ListRange) HasTemplate() bool { return lrm.Template != "" }
+
+// prefetch
+type PrefetchMsg struct {
+	ListRange
+	BlobThreshold   int64 `json:"blob-threshold"` // when greater than threshold prefetch using blob-downloader; otherwise cold GET
+	NumWorkers      int   `json:"num-workers"`    // number of concurrent workers; 0 - number of mountpaths (default); (-1) none
+	ContinueOnError bool  `json:"coer"`           // ignore non-critical errors, keep going
+	LatestVer       bool  `json:"latest-ver"`     // when true & in-cluster: check with remote whether (deleted | version-changed)
+}
+
+// ArchiveMsg contains the parameters (all except the destination bucket)
+// for archiving mutiple objects as one of the supported archive.FileExtensions types
+// at the specified (bucket) destination.
+// See also: api.PutApndArchArgs
+// --------------------  terminology   ---------------------
+// here and elsewhere "archive" is any (.tar, .tgz/.tar.gz, .zip, .tar.lz4) formatted object.
+// [NOTE] see cmn/api for cmn.ArchiveMsg (that also contains ToBck)
+type ArchiveMsg struct {
+	TxnUUID     string `json:"-"`        // internal use
+	FromBckName string `json:"-"`        // ditto
+	ArchName    string `json:"archname"` // one of the archive.FileExtensions
+	Mime        string `json:"mime"`     // user-specified mime type (NOTE: takes precedence if defined)
+	ListRange
+	BaseNameOnly    bool `json:"bnonly"` // only extract the base name of objects as names of archived objects
+	InclSrcBname    bool `json:"isbn"`   // include source bucket name into the names of archived objects
+	AppendIfExists  bool `json:"aate"`   // adding a list or a range of objects to an existing archive
+	ContinueOnError bool `json:"coer"`   // on err, keep running arc xaction in a any given multi-object transaction
+}
+
+// multi-object copy & transform
+// [NOTE] see cmn/api for cmn.TCOMsg (that also contains ToBck); see also TCBMsg
+type TCOMsg struct {
+	ListRange
+	TxnUUID    string // (plstcx client, internal use)
+	NumWorkers int    `json:"num-workers"` // number of concurrent workers; 0 - number of mountpaths (default); (-1) none
+	TCBMsg
+	ContinueOnError bool `json:"coer"`
+}
diff --git a/api/multiobj.go b/api/multiobj.go
index 65418f37c40..f4ee37d75a8 100644
--- a/api/multiobj.go
+++ b/api/multiobj.go
@@ -34,7 +34,7 @@ func ArchiveMultiObj(bp BaseParams, bckFrom cmn.Bck, msg *cmn.ArchiveBckMsg) (st
 // `fltPresence` applies exclusively to remote `bckFrom` (is ignored if the source is ais://)
 // and is one of: { apc.FltExists, apc.FltPresent, ... } - for complete enum, see api/apc/query.go
 
-func CopyMultiObj(bp BaseParams, bckFrom cmn.Bck, msg *cmn.TCObjsMsg, fltPresence ...int) (xid string, err error) {
+func CopyMultiObj(bp BaseParams, bckFrom cmn.Bck, msg *cmn.TCOMsg, fltPresence ...int) (xid string, err error) {
 	bp.Method = http.MethodPost
 	q := bckFrom.NewQuery()
 	if len(fltPresence) > 0 {
@@ -43,7 +43,7 @@ func CopyMultiObj(bp BaseParams, bckFrom cmn.Bck, msg *cmn.TCObjsMsg, fltPresenc
 	return dolr(bp, bckFrom, apc.ActCopyObjects, msg, q)
 }
 
-func ETLMultiObj(bp BaseParams, bckFrom cmn.Bck, msg *cmn.TCObjsMsg, fltPresence ...int) (xid string, err error) {
+func ETLMultiObj(bp BaseParams, bckFrom cmn.Bck, msg *cmn.TCOMsg, fltPresence ...int) (xid string, err error) {
 	bp.Method = http.MethodPost
 	q := bckFrom.NewQuery()
 	if len(fltPresence) > 0 {
diff --git a/cmd/cli/cli/blob_hdlr.go b/cmd/cli/cli/blob_hdlr.go
index 2edf1de42ae..bfa108f7071 100644
--- a/cmd/cli/cli/blob_hdlr.go
+++ b/cmd/cli/cli/blob_hdlr.go
@@ -55,8 +55,8 @@ func blobDownloadHandler(c *cli.Context) error {
 			return err
 		}
 	}
-	if flagIsSet(c, numWorkersFlag) {
-		msg.NumWorkers = parseIntFlag(c, numWorkersFlag)
+	if flagIsSet(c, numBlobWorkersFlag) {
+		msg.NumWorkers = parseIntFlag(c, numBlobWorkersFlag)
 	}
 	msg.LatestVer = flagIsSet(c, latestVerFlag)
 
diff --git a/cmd/cli/cli/const.go b/cmd/cli/cli/const.go
index b6f857db319..3f8a9dab8b1 100644
--- a/cmd/cli/cli/const.go
+++ b/cmd/cli/cli/const.go
@@ -835,13 +835,22 @@ var (
 		Usage: "utilize built-in blob-downloader (and the corresponding alternative datapath) to read very large remote objects",
 	}
 
-	numWorkersFlag = cli.IntFlag{
+	// num-workers
+	numBlobWorkersFlag = cli.IntFlag{
 		Name:  "num-workers",
 		Usage: "number of concurrent blob-downloading workers (readers); system default when omitted or zero",
 	}
+	numListRangeWorkersFlag = cli.IntFlag{
+		Name: "num-workers",
+		Usage: "number of concurrent workers (readers); number of target mountpaths if omitted or zero;\n" +
+			indent4 + "\t(-1) is a special value indicating no workers (ie., single-threaded execution);\n" +
+			indent4 + "\tany positive value will be adjusted not to exceed the number of CPUs",
+	}
 
+	// validate
 	cksumFlag = cli.BoolFlag{Name: "checksum", Usage: "validate checksum"}
 
+	// ais put
 	putObjCksumText     = indent4 + "\tand provide it as part of the PUT request for subsequent validation on the server side"
 	putObjCksumFlags    = initPutObjCksumFlags()
 	putObjDfltCksumFlag = cli.BoolFlag{
diff --git a/cmd/cli/cli/get.go b/cmd/cli/cli/get.go
index 26118c9c5a4..be03e078a37 100644
--- a/cmd/cli/cli/get.go
+++ b/cmd/cli/cli/get.go
@@ -466,10 +466,10 @@ func getObject(c *cli.Context, bck cmn.Bck, objName, outFile string, a qparamArc
 			}
 			hdr.Set(apc.HdrBlobChunk, parseStrFlag(c, chunkSizeFlag))
 		}
-		if flagIsSet(c, numWorkersFlag) {
-			nw := parseIntFlag(c, numWorkersFlag)
+		if flagIsSet(c, numBlobWorkersFlag) {
+			nw := parseIntFlag(c, numBlobWorkersFlag)
 			if nw <= 0 || nw > 128 {
-				return fmt.Errorf("invalid %s=%d: expecting (1..128) range", flprn(numWorkersFlag), nw)
+				return fmt.Errorf("invalid %s=%d: expecting (1..128) range", flprn(numBlobWorkersFlag), nw)
 			}
 			hdr.Set(apc.HdrBlobWorkers, strconv.Itoa(nw))
 		}
@@ -477,9 +477,9 @@ func getObject(c *cli.Context, bck cmn.Bck, objName, outFile string, a qparamArc
 		if !quiet {
 			now = mono.NanoTime()
 		}
-	} else if flagIsSet(c, chunkSizeFlag) || flagIsSet(c, numWorkersFlag) {
+	} else if flagIsSet(c, chunkSizeFlag) || flagIsSet(c, numBlobWorkersFlag) {
 		return fmt.Errorf("command line options (%s, %s) can be used only together with %s",
-			qflprn(chunkSizeFlag), qflprn(numWorkersFlag), qflprn(blobDownloadFlag))
+			qflprn(chunkSizeFlag), qflprn(numBlobWorkersFlag), qflprn(blobDownloadFlag))
 	}
 
 	var getArgs api.GetArgs
diff --git a/cmd/cli/cli/job_hdlr.go b/cmd/cli/cli/job_hdlr.go
index 785b261c655..bf8b5b90fe1 100644
--- a/cmd/cli/cli/job_hdlr.go
+++ b/cmd/cli/cli/job_hdlr.go
@@ -26,16 +26,16 @@ import (
 	"github.com/urfave/cli"
 )
 
-const (
-	prefetchUsage = "prefetch one remote bucket, multiple remote buckets, or\n" +
-		indent1 + "selected objects in a given remote bucket or buckets, e.g.:\n" +
-		indent1 + "\t- 'prefetch gs://abc'\t- prefetch entire bucket (all gs://abc objects that are _not_ present in the cluster);\n" +
-		indent1 + "\t- 'prefetch gs:'\t- prefetch all visible/accessible GCP buckets;\n" +
-		indent1 + "\t- 'prefetch gs://abc --template images/'\t- prefetch all objects from the virtual subdirectory \"images\";\n" +
-		indent1 + "\t- 'prefetch gs://abc/images/'\t- same as above;\n" +
-		indent1 + "\t- 'prefetch gs://abc --template \"shard-{0000..9999}.tar.lz4\"'\t- prefetch the matching range (prefix + brace expansion);\n" +
-		indent1 + "\t- 'prefetch \"gs://abc/shard-{0000..9999}.tar.lz4\"'\t- same as above (notice double quotes)"
-)
+const prefetchUsage = "prefetch one remote bucket, multiple remote buckets, or\n" +
+	indent1 + "selected objects in a given remote bucket or buckets, e.g.:\n" +
+	indent1 + "\t- 'prefetch gs://abc'\t- prefetch entire bucket (all gs://abc objects that are _not_ in-cluster);\n" +
+	indent1 + "\t- 'prefetch gs://abc --num-workers 32'\t- same as above with 32 concurrent (prefetching) workers;\n" +
+	indent1 + "\t- 'prefetch gs:'\t- prefetch all visible/accessible GCP buckets;\n" +
+	indent1 + "\t- 'prefetch gs: --num-workers=48'\t- same as above employing 48 workers;\n" +
+	indent1 + "\t- 'prefetch gs://abc --template images/'\t- prefetch all objects from the virtual subdirectory \"images\";\n" +
+	indent1 + "\t- 'prefetch gs://abc/images/'\t- same as above;\n" +
+	indent1 + "\t- 'prefetch gs://abc --template \"shard-{0000..9999}.tar.lz4\"'\t- prefetch the matching range (prefix + brace expansion);\n" +
+	indent1 + "\t- 'prefetch \"gs://abc/shard-{0000..9999}.tar.lz4\"'\t- same as above (notice double quotes)"
 
 // top-level job command
 var (
@@ -85,13 +85,14 @@ var (
 			verbObjPrefixFlag, // to disambiguate bucket/prefix vs bucket/objName
 			latestVerFlag,
 			blobThresholdFlag,
+			numListRangeWorkersFlag,
 		),
 		cmdBlobDownload: {
 			refreshFlag,
 			progressFlag,
 			listFlag,
 			chunkSizeFlag,
-			numWorkersFlag,
+			numBlobWorkersFlag,
 			waitFlag,
 			waitJobXactFinishedFlag,
 			latestVerFlag,
diff --git a/cmd/cli/cli/multiobj.go b/cmd/cli/cli/multiobj.go
index 9458a99543f..ae42a67e2a3 100644
--- a/cmd/cli/cli/multiobj.go
+++ b/cmd/cli/cli/multiobj.go
@@ -62,7 +62,7 @@ func runTCO(c *cli.Context, bckFrom, bckTo cmn.Bck, listObjs, tmplObjs, etlName
 	}
 
 	// 2. TCO message
-	msg := cmn.TCObjsMsg{ToBck: bckTo}
+	msg := cmn.TCOMsg{ToBck: bckTo}
 	{
 		msg.ListRange = lrMsg
 		msg.DryRun = flagIsSet(c, copyDryRunFlag)
@@ -444,11 +444,14 @@ func (lr *lrCtx) _do(c *cli.Context, fileList []string) (xid, kind, action strin
 			msg.ObjNames = fileList
 			msg.Template = lr.tmplObjs
 			msg.LatestVer = flagIsSet(c, latestVerFlag)
-		}
-		if flagIsSet(c, blobThresholdFlag) {
-			msg.BlobThreshold, err = parseSizeFlag(c, blobThresholdFlag)
-			if err != nil {
-				return
+			if flagIsSet(c, blobThresholdFlag) {
+				msg.BlobThreshold, err = parseSizeFlag(c, blobThresholdFlag)
+				if err != nil {
+					return
+				}
+			}
+			if flagIsSet(c, numListRangeWorkersFlag) {
+				msg.NumWorkers = parseIntFlag(c, numListRangeWorkersFlag)
 			}
 		}
 		xid, err = api.Prefetch(apiBP, lr.bck, msg)
@@ -462,7 +465,7 @@ func (lr *lrCtx) _do(c *cli.Context, fileList []string) (xid, kind, action strin
 		kind = apc.ActEvictObjects
 		action = "evict"
 	default:
-		debug.Assert(false, verb)
+		debug.Assert(false, "invalid subcommand: ", verb)
 	}
 	return xid, kind, action, err
 }
diff --git a/cmd/cli/cli/object_hdlr.go b/cmd/cli/cli/object_hdlr.go
index d21334d1481..3f83d43d36b 100644
--- a/cmd/cli/cli/object_hdlr.go
+++ b/cmd/cli/cli/object_hdlr.go
@@ -44,7 +44,7 @@ var (
 			// blob-downloader
 			blobDownloadFlag,
 			chunkSizeFlag,
-			numWorkersFlag,
+			numBlobWorkersFlag,
 			// archive
 			archpathGetFlag,
 			archmimeFlag,
diff --git a/cmd/cli/go.mod b/cmd/cli/go.mod
index 3e366160ad4..71d3bb28d2a 100644
--- a/cmd/cli/go.mod
+++ b/cmd/cli/go.mod
@@ -3,7 +3,7 @@ module github.com/NVIDIA/aistore/cmd/cli
 go 1.22.3
 
 require (
-	github.com/NVIDIA/aistore v1.3.24-0.20240911183340-8fd68450c4bc
+	github.com/NVIDIA/aistore v1.3.24-0.20240913135903-a3912a7b3c07
 	github.com/fatih/color v1.17.0
 	github.com/json-iterator/go v1.1.12
 	github.com/onsi/ginkgo/v2 v2.20.0
diff --git a/cmd/cli/go.sum b/cmd/cli/go.sum
index e70853da059..5d80a5815b5 100644
--- a/cmd/cli/go.sum
+++ b/cmd/cli/go.sum
@@ -1,7 +1,7 @@
 code.cloudfoundry.org/bytefmt v0.0.0-20190710193110-1eb035ffe2b6/go.mod h1:wN/zk7mhREp/oviagqUXY3EwuHhWyOvAdsn5Y4CzOrc=
 github.com/BurntSushi/toml v1.3.2/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
-github.com/NVIDIA/aistore v1.3.24-0.20240911183340-8fd68450c4bc h1:EZnKo05NVLt6rDsAzCrjv/nft44uOvDb0LZ41jiqO1E=
-github.com/NVIDIA/aistore v1.3.24-0.20240911183340-8fd68450c4bc/go.mod h1:si83S9r29vwIC0f0CE2Mk+25bFiaN6mmVlmuBpP4hHM=
+github.com/NVIDIA/aistore v1.3.24-0.20240913135903-a3912a7b3c07 h1:cQnI9RQ+4qdN4co4Vr60WmNIPuAAede//MVtGooZVkU=
+github.com/NVIDIA/aistore v1.3.24-0.20240913135903-a3912a7b3c07/go.mod h1:si83S9r29vwIC0f0CE2Mk+25bFiaN6mmVlmuBpP4hHM=
 github.com/OneOfOne/xxhash v1.2.8 h1:31czK/TI9sNkxIKfaUfGlU47BAxQ0ztGgd9vPyqimf8=
 github.com/OneOfOne/xxhash v1.2.8/go.mod h1:eZbhyaAYD41SGSSsnmcpxVoRiQ/MPUTjUdIIOT9Um7Q=
 github.com/VividCortex/ewma v1.1.1/go.mod h1:2Tkkvm3sRDVXaiyucHiACn4cqf7DpdyLvmxzcbUokwA=
diff --git a/cmn/api.go b/cmn/api.go
index 6ea4ddbbe9b..2fa993e3b23 100644
--- a/cmn/api.go
+++ b/cmn/api.go
@@ -366,9 +366,9 @@ type (
 	}
 
 	//  Multi-object copy & transform (see also: TCBMsg)
-	TCObjsMsg struct {
+	TCOMsg struct {
 		ToBck Bck `json:"tobck"`
-		apc.TCObjsMsg
+		apc.TCOMsg
 	}
 )
 
diff --git a/xact/xs/archive.go b/xact/xs/archive.go
index d5883889a08..a9065eb8c78 100644
--- a/xact/xs/archive.go
+++ b/xact/xs/archive.go
@@ -244,7 +244,10 @@ func (r *XactArch) Do(msg *cmn.ArchiveBckMsg) {
 		r.cleanup()
 	}
 	var lrit = &lriterator{}
-	err := lrit.init(r, &msg.ListRange, r.Bck(), true)
+
+	// lrpWorkersNone since we need a single writer to serialize adding files
+	// into an eventual `archlom`
+	err := lrit.init(r, &msg.ListRange, r.Bck(), lrpWorkersNone)
 	if err != nil {
 		r.Abort(err)
 		r.DecPending()
diff --git a/xact/xs/blob_download.go b/xact/xs/blob_download.go
index 48f498def84..183a6ecd3bd 100644
--- a/xact/xs/blob_download.go
+++ b/xact/xs/blob_download.go
@@ -137,6 +137,8 @@ func RenewBlobDl(xid string, params *core.BlobParams, oa *cmn.ObjAttrs) xreg.Ren
 			cos.ToSizeIEC(maxChunkSize, 0))
 		pre.chunkSize = maxChunkSize
 	}
+
+	// [NOTE] factor in num CPUs and num chunks to tuneup num workers (heuristic)
 	if pre.numWorkers == 0 {
 		pre.numWorkers = dfltNumWorkers
 	}
@@ -149,6 +151,7 @@ func RenewBlobDl(xid string, params *core.BlobParams, oa *cmn.ObjAttrs) xreg.Ren
 	if a := cmn.MaxParallelism(); a < pre.numWorkers {
 		pre.numWorkers = a
 	}
+
 	return xreg.RenewBucketXact(apc.ActBlobDl, lom.Bck(), xreg.Args{UUID: xid, Custom: pre})
 }
 
diff --git a/xact/xs/evict.go b/xact/xs/evict.go
index e540900d9e4..c100ac86e55 100644
--- a/xact/xs/evict.go
+++ b/xact/xs/evict.go
@@ -57,7 +57,7 @@ func (*evdFactory) WhenPrevIsRunning(xreg.Renewable) (xreg.WPR, error) {
 
 func newEvictDelete(xargs *xreg.Args, kind string, bck *meta.Bck, msg *apc.ListRange) (ed *evictDelete, err error) {
 	ed = &evictDelete{config: cmn.GCO.Get()}
-	if err = ed.lriterator.init(ed, msg, bck); err != nil {
+	if err = ed.lriterator.init(ed, msg, bck, lrpWorkersDflt); err != nil {
 		return nil, err
 	}
 	ed.InitBase(xargs.UUID, kind, bck)
diff --git a/xact/xs/lrit.go b/xact/xs/lrit.go
index 06e1febfdf0..124d96c9c91 100644
--- a/xact/xs/lrit.go
+++ b/xact/xs/lrit.go
@@ -35,6 +35,14 @@ const (
 	lrpPrefix
 )
 
+// when number of workers is not defined in a respective control message
+// (see e.g. PrefetchMsg.NumWorkers)
+// we have two special values
+const (
+	lrpWorkersNone = -1 // no workers at all - iterated LOMs get executed by the (iterating) goroutine
+	lrpWorkersDflt = 0  // num workers = number of mountpaths
+)
+
 // common for all list-range
 type (
 	// one multi-object operation work item
@@ -94,9 +102,11 @@ var (
 // lriterator //
 ////////////////
 
-func (r *lriterator) init(xctn lrxact, msg *apc.ListRange, bck *meta.Bck, blocking ...bool) error {
-	avail := fs.GetAvail()
-	l := len(avail)
+func (r *lriterator) init(xctn lrxact, msg *apc.ListRange, bck *meta.Bck, numWorkers int) error {
+	var (
+		avail = fs.GetAvail()
+		l     = len(avail)
+	)
 	if l == 0 {
 		return cmn.ErrNoMountpaths
 	}
@@ -104,28 +114,49 @@ func (r *lriterator) init(xctn lrxact, msg *apc.ListRange, bck *meta.Bck, blocki
 	r.msg = msg
 	r.bck = bck
 
-	// list is the simplest and always single-threaded
 	if msg.IsList() {
 		r.lrp = lrpList
-		return nil
-	}
-	if err := r._inipr(msg); err != nil {
-		return err
+	} else {
+		if err := r._inipr(msg); err != nil {
+			return err
+		}
 	}
-	if l == 1 {
+
+	// run single-threaded
+	if numWorkers == lrpWorkersNone {
 		return nil
 	}
-	if len(blocking) > 0 && blocking[0] {
-		return nil
+
+	// tuneup number of concurrent workers (heuristic)
+	if numWorkers == lrpWorkersDflt {
+		numWorkers = l
+	}
+	if a := cmn.MaxParallelism(); a > numWorkers+8 {
+		var bump bool
+		a <<= 1
+		switch r.lrp {
+		case lrpList:
+			bump = len(msg.ObjNames) > a
+		case lrpRange:
+			bump = int(r.pt.Count()) > a
+		case lrpPrefix:
+			bump = true // err on that other side
+		}
+		if bump {
+			numWorkers += 2
+		}
+	} else {
+		numWorkers = min(numWorkers, a)
 	}
 
-	// num-workers == num-mountpaths but note:
-	// these are not _joggers_
-	r.workers = make([]*lrworker, 0, l)
-	for range avail {
+	// but note: these are _not_ joggers
+	r.workers = make([]*lrworker, 0, numWorkers)
+	for range numWorkers {
 		r.workers = append(r.workers, &lrworker{r})
 	}
-	r.workCh = make(chan lrpair, l)
+
+	// work channel capacity: up to 4 pending work items per
+	r.workCh = make(chan lrpair, min(numWorkers<<2, 512))
 	return nil
 }
 
@@ -158,6 +189,8 @@ pref:
 	return nil
 }
 
+func (r *lriterator) numWorkers() int { return len(r.workers) }
+
 func (r *lriterator) run(wi lrwi, smap *meta.Smap) (err error) {
 	for _, worker := range r.workers {
 		r.wg.Add(1)
@@ -251,7 +284,7 @@ func (r *lriterator) _prefix(wi lrwi, smap *meta.Smap) error {
 			lst = &npg.page
 		}
 		if err != nil {
-			nlog.Errorln(core.T.String()+":", err, ecode)
+			nlog.Errorln(core.T.String(), "[", err, "ecode", ecode, "]")
 			freeLsoEntries(lst.Entries)
 			return err
 		}
diff --git a/xact/xs/prefetch.go b/xact/xs/prefetch.go
index 1c6bdedbc08..175120b041c 100644
--- a/xact/xs/prefetch.go
+++ b/xact/xs/prefetch.go
@@ -89,7 +89,7 @@ func (*prfFactory) WhenPrevIsRunning(xreg.Renewable) (xreg.WPR, error) {
 func newPrefetch(xargs *xreg.Args, kind string, bck *meta.Bck, msg *apc.PrefetchMsg) (r *prefetch, err error) {
 	r = &prefetch{config: cmn.GCO.Get(), msg: msg}
 
-	err = r.lriterator.init(r, &msg.ListRange, bck)
+	err = r.lriterator.init(r, &msg.ListRange, bck, msg.NumWorkers)
 	if err != nil {
 		return nil, err
 	}
@@ -103,7 +103,14 @@ func newPrefetch(xargs *xreg.Args, kind string, bck *meta.Bck, msg *apc.Prefetch
 }
 
 func (r *prefetch) Run(wg *sync.WaitGroup) {
+	if nw := r.lriterator.numWorkers(); nw > 1 {
+		nlog.Infoln(r.Name(), "[", nw, "workers ]")
+	} else {
+		nlog.Infoln(r.Name())
+	}
+
 	wg.Done()
+
 	err := r.lriterator.run(r, core.T.Sowner().Get())
 	if err != nil {
 		r.AddErr(err, 5, cos.SmoduleXs) // duplicated?
diff --git a/xact/xs/tcobjs.go b/xact/xs/tcobjs.go
index db36aa37dfd..be29093d7ea 100644
--- a/xact/xs/tcobjs.go
+++ b/xact/xs/tcobjs.go
@@ -40,14 +40,14 @@ type (
 			mtx sync.RWMutex
 		}
 		args     *xreg.TCObjsArgs
-		workCh   chan *cmn.TCObjsMsg
+		workCh   chan *cmn.TCOMsg
 		chanFull atomic.Int64
 		streamingX
 		owt cmn.OWT
 	}
 	tcowi struct {
 		r   *XactTCObjs
-		msg *cmn.TCObjsMsg
+		msg *cmn.TCOMsg
 		// finishing
 		refc atomic.Int32
 	}
@@ -81,7 +81,7 @@ func (p *tcoFactory) Start() error {
 	p.Args.UUID = PrefixTcoID + uuid
 
 	// new x-tco
-	workCh := make(chan *cmn.TCObjsMsg, maxNumInParallel)
+	workCh := make(chan *cmn.TCOMsg, maxNumInParallel)
 	r := &XactTCObjs{streamingX: streamingX{p: &p.streamingF, config: cmn.GCO.Get()}, args: p.args, workCh: workCh}
 	r.pending.m = make(map[string]*tcowi, maxNumInParallel)
 	r.owt = cmn.OwtCopy
@@ -134,7 +134,7 @@ func (r *XactTCObjs) Snap() (snap *core.Snap) {
 	return
 }
 
-func (r *XactTCObjs) Begin(msg *cmn.TCObjsMsg) {
+func (r *XactTCObjs) Begin(msg *cmn.TCOMsg) {
 	wi := &tcowi{r: r, msg: msg}
 	r.pending.mtx.Lock()
 	r.pending.m[msg.TxnUUID] = wi
@@ -175,7 +175,7 @@ func (r *XactTCObjs) Run(wg *sync.WaitGroup) {
 
 			// run
 			var wg *sync.WaitGroup
-			if err = lrit.init(r, &msg.ListRange, r.Bck()); err == nil {
+			if err = lrit.init(r, &msg.ListRange, r.Bck(), lrpWorkersDflt); err == nil {
 				if msg.Sync && lrit.lrp != lrpList {
 					wg = &sync.WaitGroup{}
 					wg.Add(1)
@@ -213,7 +213,7 @@ fin:
 }
 
 // more work
-func (r *XactTCObjs) Do(msg *cmn.TCObjsMsg) {
+func (r *XactTCObjs) Do(msg *cmn.TCOMsg) {
 	r.IncPending()
 	r.workCh <- msg
 
@@ -372,7 +372,7 @@ func (r *XactTCObjs) prune(lrit *lriterator, smap *meta.Smap, pt *cos.ParsedTemp
 	var syncit lriterator
 	debug.Assert(lrit.lrp == lrpRange)
 
-	err := syncit.init(lrit.parent, lrit.msg, rp.bckTo)
+	err := syncit.init(lrit.parent, lrit.msg, rp.bckTo, lrpWorkersDflt)
 	debug.AssertNoErr(err)
 	syncit.pt = pt
 	syncwi := &syncwi{&rp} // reusing only prune.do (and not init/run/wait)