diff --git a/test/tus/tus_integration_test.go b/test/tus/tus_integration_test.go
index c923577e3..96f4bd505 100644
--- a/test/tus/tus_integration_test.go
+++ b/test/tus/tus_integration_test.go
@@ -685,6 +685,135 @@ func TestTusCreationWithUpload(t *testing.T) {
 	assert.Equal(t, testData, body)
 }
 
+// TestTusConcatenation tests the concatenation extension: partial uploads
+// assembled into a final upload
+func TestTusConcatenation(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping integration test in short mode")
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 120*time.Second)
+	defer cancel()
+
+	cluster, err := startTestCluster(t, ctx)
+	require.NoError(t, err)
+	defer func() {
+		cluster.Stop()
+		os.RemoveAll(cluster.dataDir)
+	}()
+
+	client := &http.Client{}
+
+	// The extension is announced
+	optionsReq, err := http.NewRequest(http.MethodOptions, cluster.TusURL()+"/", nil)
+	require.NoError(t, err)
+	optionsReq.Header.Set("Tus-Resumable", TusVersion)
+	optionsResp, err := client.Do(optionsReq)
+	require.NoError(t, err)
+	optionsResp.Body.Close()
+	assert.Contains(t, optionsResp.Header.Get("Tus-Extension"), "concatenation")
+
+	partA := []byte("Hello, ")
+	partB := []byte("concatenated TUS world!")
+	targetPath := "/concat/final.txt"
+
+	createPartial := func(size int) string {
+		req, err := http.NewRequest(http.MethodPost, cluster.TusURL()+targetPath, nil)
+		require.NoError(t, err)
+		req.Header.Set("Tus-Resumable", TusVersion)
+		req.Header.Set("Upload-Length", strconv.Itoa(size))
+		req.Header.Set("Upload-Concat", "partial")
+		resp, err := client.Do(req)
+		require.NoError(t, err)
+		defer resp.Body.Close()
+		require.Equal(t, http.StatusCreated, resp.StatusCode)
+		location := resp.Header.Get("Location")
+		require.NotEmpty(t, location)
+		return location
+	}
+
+	patchAll := func(location string, data []byte) {
+		req, err := http.NewRequest(http.MethodPatch, cluster.FullURL(location), bytes.NewReader(data))
+		require.NoError(t, err)
+		req.Header.Set("Tus-Resumable", TusVersion)
+		req.Header.Set("Upload-Offset", "0")
+		req.Header.Set("Content-Type", "application/offset+octet-stream")
+		resp, err := client.Do(req)
+		require.NoError(t, err)
+		resp.Body.Close()
+		require.Equal(t, http.StatusNoContent, resp.StatusCode)
+	}
+
+	locationA := createPartial(len(partA))
+	locationB := createPartial(len(partB))
+	concatHeader := "final;" + locationA + " " + locationB
+
+	patchAll(locationA, partA)
+
+	// Concatenation is rejected while a listed partial is unfinished
+	prematureReq, err := http.NewRequest(http.MethodPost, cluster.TusURL()+targetPath, nil)
+	require.NoError(t, err)
+	prematureReq.Header.Set("Tus-Resumable", TusVersion)
+	prematureReq.Header.Set("Upload-Concat", concatHeader)
+	prematureResp, err := client.Do(prematureReq)
+	require.NoError(t, err)
+	prematureResp.Body.Close()
+	require.Equal(t, http.StatusBadRequest, prematureResp.StatusCode)
+
+	patchAll(locationB, partB)
+
+	// A completed partial reports its status and does not land at the target
+	headReq, err := http.NewRequest(http.MethodHead, cluster.FullURL(locationA), nil)
+	require.NoError(t, err)
+	headReq.Header.Set("Tus-Resumable", TusVersion)
+	headResp, err := client.Do(headReq)
+	require.NoError(t, err)
+	headResp.Body.Close()
+	require.Equal(t, http.StatusOK, headResp.StatusCode)
+	assert.Equal(t, "partial", headResp.Header.Get("Upload-Concat"))
+
+	getResp, err := client.Get(cluster.FilerURL() + targetPath)
+	require.NoError(t, err)
+	getResp.Body.Close()
+	require.Equal(t, http.StatusNotFound, getResp.StatusCode,
+		"completed partials should not land at the target path")
+
+	// Concatenate into the final upload
+	finalReq, err := http.NewRequest(http.MethodPost, cluster.TusURL()+targetPath, nil)
+	require.NoError(t, err)
+	finalReq.Header.Set("Tus-Resumable", TusVersion)
+	finalReq.Header.Set("Upload-Concat", concatHeader)
+	finalReq.Header.Set("Upload-Metadata", encodeTusMetadata(map[string]string{
+		"content-type": "text/plain",
+	}))
+	finalResp, err := client.Do(finalReq)
+	require.NoError(t, err)
+	finalResp.Body.Close()
+	require.Equal(t, http.StatusCreated, finalResp.StatusCode)
+	assert.NotEmpty(t, finalResp.Header.Get("Location"))
+
+	// The target file holds both parts in order
+	expected := append(append([]byte{}, partA...), partB...)
+	getResp2, err := client.Get(cluster.FilerURL() + targetPath)
+	require.NoError(t, err)
+	defer getResp2.Body.Close()
+	require.Equal(t, http.StatusOK, getResp2.StatusCode)
+	body, err := io.ReadAll(getResp2.Body)
+	require.NoError(t, err)
+	assert.Equal(t, expected, body, "Concatenated file should hold both parts in order")
+	assert.Contains(t, getResp2.Header.Get("Content-Type"), "text/plain")
+
+	// The consumed partials are gone
+	headReq2, err := http.NewRequest(http.MethodHead, cluster.FullURL(locationA), nil)
+	require.NoError(t, err)
+	headReq2.Header.Set("Tus-Resumable", TusVersion)
+	headResp2, err := client.Do(headReq2)
+	require.NoError(t, err)
+	headResp2.Body.Close()
+	require.Equal(t, http.StatusNotFound, headResp2.StatusCode,
+		"consumed partial should be removed after concatenation")
+}
+
 // TestTusResumeAfterInterruption simulates resuming an upload after failure
 func TestTusResumeAfterInterruption(t *testing.T) {
 	if testing.Short() {
diff --git a/weed/server/filer_server_tus_concat_test.go b/weed/server/filer_server_tus_concat_test.go
new file mode 100644
index 000000000..a361f3d04
--- /dev/null
+++ b/weed/server/filer_server_tus_concat_test.go
@@ -0,0 +1,345 @@
+package weed_server
+
+import (
+	"context"
+	"encoding/base64"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/seaweedfs/seaweedfs/weed/filer"
+	"github.com/seaweedfs/seaweedfs/weed/util"
+)
+
+const (
+	tusTestPartialAID = "11111111-1111-1111-1111-111111111111"
+	tusTestPartialBID = "22222222-2222-2222-2222-222222222222"
+)
+
+// seedTusChunk writes a chunk marker entry into a session directory.
+func seedTusChunk(t *testing.T, fs *FilerServer, store *renameTestStore, uploadID string, offset, size int64, fileId string) {
+	t.Helper()
+	entry := &filer.Entry{
+		FullPath: util.FullPath(fs.tusChunkPath(uploadID, offset, size, fileId)),
+		Attr:     filer.Attr{Crtime: time.Unix(1700000000, 0)},
+	}
+	if err := store.InsertEntry(context.Background(), entry); err != nil {
+		t.Fatalf("seed chunk for %s: %v", uploadID, err)
+	}
+}
+
+func tusRequest(method, path string, headers map[string]string, body string) *http.Request {
+	var req *http.Request
+	if body == "" {
+		req = httptest.NewRequest(method, path, http.NoBody)
+	} else {
+		req = httptest.NewRequest(method, path, strings.NewReader(body))
+	}
+	req.Header.Set("Tus-Resumable", TusVersion)
+	for k, v := range headers {
+		req.Header.Set(k, v)
+	}
+	return req
+}
+
+// TestFilerServer_tusPatchHandler_PartialSkipsCompletion verifies a completed
+// partial upload keeps its session and does not land at the target path, while
+// the same flow without Upload-Concat completes normally.
+func TestFilerServer_tusPatchHandler_PartialSkipsCompletion(t *testing.T) {
+	tests := []struct {
+		name        string
+		concat      string
+		expectEntry bool
+	}{
+		{"plain upload completes", "", true},
+		{"partial upload retained", TusConcatPartial, false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fs, store := newTusTestServer(t, nil)
+			targetPath := "/buckets/data/file.bin"
+			seedTusSession(t, fs, store, TusSession{ID: tusTestUploadID, TargetPath: targetPath, Size: 0, Concat: tt.concat})
+
+			req := tusRequest(http.MethodPatch, "/.tus/.uploads/"+tusTestUploadID, map[string]string{
+				"Authorization": "Bearer " + signFilerToken(t, tusTestWriteKey, nil, nil),
+				"Content-Type":  "application/offset+octet-stream",
+				"Upload-Offset": "0",
+			}, "")
+			rec := httptest.NewRecorder()
+			fs.tusHandler(rec, req)
+
+			if rec.Code != http.StatusNoContent {
+				t.Fatalf("PATCH = %d, want %d; body=%q", rec.Code, http.StatusNoContent, rec.Body.String())
+			}
+			_, entryErr := store.FindEntry(context.Background(), util.FullPath(targetPath))
+			_, sessionErr := store.FindEntry(context.Background(), util.FullPath(fs.tusSessionInfoPath(tusTestUploadID)))
+			if tt.expectEntry && (entryErr != nil || sessionErr == nil) {
+				t.Fatalf("plain upload: entry err=%v, session err=%v; want entry present and session removed", entryErr, sessionErr)
+			}
+			if !tt.expectEntry && (entryErr == nil || sessionErr != nil) {
+				t.Fatalf("partial upload: entry err=%v, session err=%v; want no entry and session retained", entryErr, sessionErr)
+			}
+		})
+	}
+}
+
+// TestFilerServer_tusHeadHandler_EchoesUploadConcat verifies HEAD reports the
+// stored Upload-Concat value for partial sessions and omits it otherwise.
+func TestFilerServer_tusHeadHandler_EchoesUploadConcat(t *testing.T) {
+	fs, store := newTusTestServer(t, map[string]string{tusTestUploadID: "/buckets/data/plain.bin"})
+	seedTusSession(t, fs, store, TusSession{ID: tusTestPartialAID, TargetPath: "/buckets/data/part.bin", Size: 1, Concat: TusConcatPartial})
+
+	head := func(uploadID string) *httptest.ResponseRecorder {
+		req := tusRequest(http.MethodHead, "/.tus/.uploads/"+uploadID, map[string]string{
+			"Authorization": "Bearer " + signFilerToken(t, tusTestReadKey, nil, nil),
+		}, "")
+		rec := httptest.NewRecorder()
+		fs.tusHandler(rec, req)
+		return rec
+	}
+
+	partialRec := head(tusTestPartialAID)
+	if partialRec.Code != http.StatusOK || partialRec.Header().Get("Upload-Concat") != TusConcatPartial {
+		t.Fatalf("partial HEAD = %d, Upload-Concat=%q; want 200 with %q", partialRec.Code, partialRec.Header().Get("Upload-Concat"), TusConcatPartial)
+	}
+	plainRec := head(tusTestUploadID)
+	if plainRec.Code != http.StatusOK || plainRec.Header().Get("Upload-Concat") != "" {
+		t.Fatalf("plain HEAD = %d, Upload-Concat=%q; want 200 without the header", plainRec.Code, plainRec.Header().Get("Upload-Concat"))
+	}
+}
+
+// TestFilerServer_tusConcatFinal_AssemblesPartials drives a full concatenation:
+// two completed partials, referenced as a path and as an absolute URL, land as
+// one entry with re-based chunks, and the consumed sessions are removed.
+func TestFilerServer_tusConcatFinal_AssemblesPartials(t *testing.T) {
+	fs, store := newTusTestServer(t, nil)
+	targetPath := "/buckets/data/final.bin"
+	fidA, fidB := "3,01637037d6", "4,02637037d6"
+	seedTusSession(t, fs, store, TusSession{ID: tusTestPartialAID, TargetPath: targetPath, Size: 8, Concat: TusConcatPartial})
+	seedTusChunk(t, fs, store, tusTestPartialAID, 0, 8, fidA)
+	seedTusSession(t, fs, store, TusSession{ID: tusTestPartialBID, TargetPath: targetPath, Size: 4, Concat: TusConcatPartial})
+	seedTusChunk(t, fs, store, tusTestPartialBID, 0, 4, fidB)
+
+	req := tusRequest(http.MethodPost, "/.tus"+targetPath, map[string]string{
+		"Authorization":   "Bearer " + signFilerToken(t, tusTestWriteKey, nil, nil),
+		"Upload-Concat":   "final;/.tus/.uploads/" + tusTestPartialAID + " http://example.com/.tus/.uploads/" + tusTestPartialBID,
+		"Upload-Metadata": "content-type " + base64.StdEncoding.EncodeToString([]byte("text/plain")),
+	}, "")
+	rec := httptest.NewRecorder()
+	fs.tusHandler(rec, req)
+
+	if rec.Code != http.StatusCreated {
+		t.Fatalf("final POST = %d, want %d; body=%q", rec.Code, http.StatusCreated, rec.Body.String())
+	}
+	if location := rec.Header().Get("Location"); !strings.HasPrefix(location, "/.tus/.uploads/") {
+		t.Fatalf("Location = %q, want an upload URL", location)
+	}
+
+	entry, err := store.FindEntry(context.Background(), util.FullPath(targetPath))
+	if err != nil {
+		t.Fatalf("final entry not created: %v", err)
+	}
+	if entry.Mime != "text/plain" {
+		t.Errorf("entry mime = %q, want %q", entry.Mime, "text/plain")
+	}
+	chunks := entry.GetChunks()
+	if len(chunks) != 2 {
+		t.Fatalf("entry chunks = %d, want 2", len(chunks))
+	}
+	if chunks[0].FileId != fidA || chunks[0].Offset != 0 || chunks[0].Size != 8 {
+		t.Errorf("chunk[0] = %s@%d+%d, want %s@0+8", chunks[0].FileId, chunks[0].Offset, chunks[0].Size, fidA)
+	}
+	if chunks[1].FileId != fidB || chunks[1].Offset != 8 || chunks[1].Size != 4 {
+		t.Errorf("chunk[1] = %s@%d+%d, want %s@8+4", chunks[1].FileId, chunks[1].Offset, chunks[1].Size, fidB)
+	}
+
+	for _, uploadID := range []string{tusTestPartialAID, tusTestPartialBID} {
+		if _, err := store.FindEntry(context.Background(), util.FullPath(fs.tusSessionInfoPath(uploadID))); err == nil {
+			t.Errorf("partial session %s still present after concatenation", uploadID)
+		}
+	}
+}
+
+// TestFilerServer_tusConcatFinal_Validation covers the final upload request
+// guards: header misuse, unusable references, unfinished or foreign partials.
+func TestFilerServer_tusConcatFinal_Validation(t *testing.T) {
+	uploadsRef := func(uploadID string) string { return "/.tus/.uploads/" + uploadID }
+	completePartial := func(fs *FilerServer, store *renameTestStore, t *testing.T, uploadID, targetPath string, size int64) {
+		seedTusSession(t, fs, store, TusSession{ID: uploadID, TargetPath: targetPath, Size: size, Concat: TusConcatPartial})
+		seedTusChunk(t, fs, store, uploadID, 0, size, "3,01637037d6")
+	}
+
+	tests := []struct {
+		name         string
+		seed         func(t *testing.T, fs *FilerServer, store *renameTestStore)
+		headers      map[string]string
+		body         string
+		prefixes     []string
+		expectStatus int
+	}{
+		{
+			name:         "upload length rejected",
+			headers:      map[string]string{"Upload-Concat": "final;" + uploadsRef(tusTestPartialAID), "Upload-Length": "12"},
+			expectStatus: http.StatusBadRequest,
+		},
+		{
+			name:         "body rejected",
+			headers:      map[string]string{"Upload-Concat": "final;" + uploadsRef(tusTestPartialAID)},
+			body:         "x",
+			expectStatus: http.StatusForbidden,
+		},
+		{
+			name:         "reference outside uploads prefix",
+			headers:      map[string]string{"Upload-Concat": "final;/elsewhere/" + tusTestPartialAID},
+			expectStatus: http.StatusBadRequest,
+		},
+		{
+			name:         "duplicate reference",
+			headers:      map[string]string{"Upload-Concat": "final;" + uploadsRef(tusTestPartialAID) + " " + uploadsRef(tusTestPartialAID)},
+			expectStatus: http.StatusBadRequest,
+		},
+		{
+			name:         "empty reference list",
+			headers:      map[string]string{"Upload-Concat": "final;"},
+			expectStatus: http.StatusBadRequest,
+		},
+		{
+			name:         "missing partial",
+			headers:      map[string]string{"Upload-Concat": "final;" + uploadsRef(tusTestPartialAID)},
+			expectStatus: http.StatusNotFound,
+		},
+		{
+			name: "non-partial session rejected",
+			seed: func(t *testing.T, fs *FilerServer, store *renameTestStore) {
+				seedTusSession(t, fs, store, TusSession{ID: tusTestPartialAID, TargetPath: "/buckets/data/a.bin", Size: 1})
+			},
+			headers:      map[string]string{"Upload-Concat": "final;" + uploadsRef(tusTestPartialAID)},
+			expectStatus: http.StatusBadRequest,
+		},
+		{
+			name: "unfinished partial rejected",
+			seed: func(t *testing.T, fs *FilerServer, store *renameTestStore) {
+				seedTusSession(t, fs, store, TusSession{ID: tusTestPartialAID, TargetPath: "/buckets/data/a.bin", Size: 4, Concat: TusConcatPartial})
+			},
+			headers:      map[string]string{"Upload-Concat": "final;" + uploadsRef(tusTestPartialAID)},
+			expectStatus: http.StatusBadRequest,
+		},
+		{
+			name: "cross-prefix partial denied",
+			seed: func(t *testing.T, fs *FilerServer, store *renameTestStore) {
+				completePartial(fs, store, t, tusTestPartialAID, "/buckets/secret/victim.bin", 4)
+			},
+			headers:      map[string]string{"Upload-Concat": "final;" + uploadsRef(tusTestPartialAID)},
+			prefixes:     []string{"/buckets/data"},
+			expectStatus: http.StatusUnauthorized,
+		},
+		{
+			name: "combined size over maximum",
+			seed: func(t *testing.T, fs *FilerServer, store *renameTestStore) {
+				completePartial(fs, store, t, tusTestPartialAID, "/buckets/data/a.bin", TusDefaultMaxSize)
+				seedTusSession(t, fs, store, TusSession{ID: tusTestPartialBID, TargetPath: "/buckets/data/b.bin", Size: 1, Concat: TusConcatPartial})
+			},
+			headers:      map[string]string{"Upload-Concat": "final;" + uploadsRef(tusTestPartialAID) + " " + uploadsRef(tusTestPartialBID)},
+			expectStatus: http.StatusRequestEntityTooLarge,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fs, store := newTusTestServer(t, nil)
+			if tt.seed != nil {
+				tt.seed(t, fs, store)
+			}
+			headers := map[string]string{
+				"Authorization": "Bearer " + signFilerToken(t, tusTestWriteKey, tt.prefixes, nil),
+			}
+			for k, v := range tt.headers {
+				headers[k] = v
+			}
+			req := tusRequest(http.MethodPost, "/.tus/buckets/data/final.bin", headers, tt.body)
+			rec := httptest.NewRecorder()
+			fs.tusHandler(rec, req)
+
+			if rec.Code != tt.expectStatus {
+				t.Fatalf("final POST = %d, want %d; body=%q", rec.Code, tt.expectStatus, rec.Body.String())
+			}
+			if _, err := store.FindEntry(context.Background(), util.FullPath("/buckets/data/final.bin")); err == nil {
+				t.Fatal("rejected concatenation still created the target entry")
+			}
+		})
+	}
+}
+
+// TestFilerServer_tusConcatFinal_ClaimedPartialRejected verifies a partial
+// already claimed by a concurrent final cannot be consumed again, and that the
+// foreign claim is left in place.
+func TestFilerServer_tusConcatFinal_ClaimedPartialRejected(t *testing.T) {
+	fs, store := newTusTestServer(t, nil)
+	seedTusSession(t, fs, store, TusSession{ID: tusTestPartialAID, TargetPath: "/buckets/data/a.bin", Size: 4, Concat: TusConcatPartial})
+	seedTusChunk(t, fs, store, tusTestPartialAID, 0, 4, "3,01637037d6")
+	markerPath := util.FullPath(fs.tusSessionConsumedPath(tusTestPartialAID))
+	if err := store.InsertEntry(context.Background(), &filer.Entry{FullPath: markerPath}); err != nil {
+		t.Fatalf("seed consumed marker: %v", err)
+	}
+
+	req := tusRequest(http.MethodPost, "/.tus/buckets/data/final.bin", map[string]string{
+		"Authorization": "Bearer " + signFilerToken(t, tusTestWriteKey, nil, nil),
+		"Upload-Concat": "final;/.tus/.uploads/" + tusTestPartialAID,
+	}, "")
+	rec := httptest.NewRecorder()
+	fs.tusHandler(rec, req)
+
+	if rec.Code != http.StatusConflict {
+		t.Fatalf("final POST = %d, want %d; body=%q", rec.Code, http.StatusConflict, rec.Body.String())
+	}
+	if _, err := store.FindEntry(context.Background(), markerPath); err != nil {
+		t.Fatal("foreign claim was released by the losing request")
+	}
+}
+
+// TestFilerServer_tusDeleteHandler_ConsumedSessionKeepsChunks verifies deleting
+// a consumed session removes its metadata without freeing its chunks. The test
+// filer has no chunk deletion queue, so an attempt to free chunks would panic.
+func TestFilerServer_tusDeleteHandler_ConsumedSessionKeepsChunks(t *testing.T) {
+	fs, store := newTusTestServer(t, nil)
+	seedTusSession(t, fs, store, TusSession{ID: tusTestPartialAID, TargetPath: "/buckets/data/a.bin", Size: 4, Concat: TusConcatPartial})
+	seedTusChunk(t, fs, store, tusTestPartialAID, 0, 4, "3,01637037d6")
+	if err := store.InsertEntry(context.Background(), &filer.Entry{FullPath: util.FullPath(fs.tusSessionConsumedPath(tusTestPartialAID))}); err != nil {
+		t.Fatalf("seed consumed marker: %v", err)
+	}
+
+	req := tusRequest(http.MethodDelete, "/.tus/.uploads/"+tusTestPartialAID, map[string]string{
+		"Authorization": "Bearer " + signFilerToken(t, tusTestWriteKey, nil, nil),
+	}, "")
+	rec := httptest.NewRecorder()
+	fs.tusHandler(rec, req)
+
+	if rec.Code != http.StatusNoContent {
+		t.Fatalf("DELETE = %d, want %d; body=%q", rec.Code, http.StatusNoContent, rec.Body.String())
+	}
+	if _, err := store.FindEntry(context.Background(), util.FullPath(fs.tusSessionInfoPath(tusTestPartialAID))); err == nil {
+		t.Fatal("consumed session metadata still present after DELETE")
+	}
+}
+
+// TestFilerServer_tusPatchHandler_FinalRejected verifies PATCH against a final
+// upload URL is refused, per the concatenation extension.
+func TestFilerServer_tusPatchHandler_FinalRejected(t *testing.T) {
+	fs, store := newTusTestServer(t, nil)
+	seedTusSession(t, fs, store, TusSession{ID: tusTestUploadID, TargetPath: "/buckets/data/final.bin", Size: 4, Concat: "final;/.tus/.uploads/" + tusTestPartialAID})
+
+	req := tusRequest(http.MethodPatch, "/.tus/.uploads/"+tusTestUploadID, map[string]string{
+		"Authorization": "Bearer " + signFilerToken(t, tusTestWriteKey, nil, nil),
+		"Content-Type":  "application/offset+octet-stream",
+		"Upload-Offset": "0",
+	}, "")
+	rec := httptest.NewRecorder()
+	fs.tusHandler(rec, req)
+
+	if rec.Code != http.StatusForbidden {
+		t.Fatalf("PATCH final = %d, want %d; body=%q", rec.Code, http.StatusForbidden, rec.Body.String())
+	}
+}
diff --git a/weed/server/filer_server_tus_handlers.go b/weed/server/filer_server_tus_handlers.go
index 5b72e45a8..598e45e0b 100644
--- a/weed/server/filer_server_tus_handlers.go
+++ b/weed/server/filer_server_tus_handlers.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"net/url"
 	"path"
 	"strconv"
 	"strings"
@@ -112,7 +113,7 @@ func (fs *FilerServer) tusHandler(w http.ResponseWriter, r *http.Request) {
 			writeJsonError(w, r, http.StatusUnauthorized, errors.New("wrong jwt"))
 			return
 		}
-		fs.tusCreateHandler(w, r)
+		fs.tusCreateHandler(w, r, claims)
 	default:
 		w.WriteHeader(http.StatusMethodNotAllowed)
 	}
@@ -180,12 +181,22 @@ func (fs *FilerServer) tusOptionsHandler(w http.ResponseWriter, r *http.Request)
 }
 
 // tusCreateHandler handles POST requests to create new uploads
-func (fs *FilerServer) tusCreateHandler(w http.ResponseWriter, r *http.Request) {
+func (fs *FilerServer) tusCreateHandler(w http.ResponseWriter, r *http.Request, claims *security.SeaweedFilerClaims) {
 	// Use a context that ignores cancellation from the request context.
 	// Internal operations (creating TUS session, writing data, completing uploads)
 	// may exceed the filer's client connection inactivity timeout.
 	ctx := context.WithoutCancel(r.Context())
 
+	concat := r.Header.Get("Upload-Concat")
+	if strings.HasPrefix(concat, TusConcatFinalPrefix) {
+		fs.tusConcatFinalHandler(w, r, claims, concat)
+		return
+	}
+	if concat != "" && concat != TusConcatPartial {
+		http.Error(w, "Invalid Upload-Concat", http.StatusBadRequest)
+		return
+	}
+
 	// Parse Upload-Length header (required)
 	uploadLengthStr := r.Header.Get("Upload-Length")
 	if uploadLengthStr == "" {
@@ -205,9 +216,6 @@ func (fs *FilerServer) tusCreateHandler(w http.ResponseWriter, r *http.Request)
 	// Parse Upload-Metadata header (optional)
 	metadata := parseTusMetadata(r.Header.Get("Upload-Metadata"))
 
-	// TusBasePath is pre-normalized in filer_server.go (leading slash, no trailing slash)
-	tusPrefix := fs.option.TusBasePath
-
 	// Determine target path from request URL (leading slash guaranteed)
 	targetPath := fs.tusTargetPath(r)
 	if targetPath == "" || targetPath == "/" {
@@ -226,18 +234,14 @@ func (fs *FilerServer) tusCreateHandler(w http.ResponseWriter, r *http.Request)
 	uploadID := uuid.New().String()
 
 	// Create upload session
-	session, err := fs.createTusSession(ctx, uploadID, targetPath, uploadLength, metadata)
+	session, err := fs.createTusSession(ctx, uploadID, targetPath, uploadLength, metadata, concat)
 	if err != nil {
 		glog.Errorf("Failed to create TUS session: %v", err)
 		http.Error(w, "Failed to create upload", http.StatusInternalServerError)
 		return
 	}
 
-	// Build upload location URL (ensure it starts with single /)
-	uploadLocation := path.Clean(fmt.Sprintf("%s/.uploads/%s", tusPrefix, uploadID))
-	if !strings.HasPrefix(uploadLocation, "/") {
-		uploadLocation = "/" + uploadLocation
-	}
+	uploadLocation := fs.tusUploadLocation(uploadID)
 
 	// Handle creation-with-upload extension
 	// TUS requires Content-Length for uploads; reject chunked encoding
@@ -265,8 +269,9 @@ func (fs *FilerServer) tusCreateHandler(w http.ResponseWriter, r *http.Request)
 			// Update offset in response header
 			w.Header().Set("Upload-Offset", strconv.FormatInt(bytesWritten, 10))
 
-			// Check if upload is complete
-			if bytesWritten == session.Size {
+			// Check if upload is complete; a partial upload keeps its chunks for
+			// a later concatenation instead of landing at the target path.
+			if bytesWritten == session.Size && !session.isPartial() {
 				// Ensure the pinned session still exists, then refresh its chunks.
 				if err = fs.refreshTusSessionChunks(ctx, session); err != nil {
 					glog.Errorf("Failed to get updated TUS session: %v", err)
@@ -287,8 +292,185 @@ func (fs *FilerServer) tusCreateHandler(w http.ResponseWriter, r *http.Request)
 	w.WriteHeader(http.StatusCreated)
 }
 
+// tusUploadLocation builds the upload URL path for a session id (single leading /)
+func (fs *FilerServer) tusUploadLocation(uploadID string) string {
+	// TusBasePath is pre-normalized in filer_server.go (leading slash, no trailing slash)
+	uploadLocation := path.Clean(fmt.Sprintf("%s/.uploads/%s", fs.option.TusBasePath, uploadID))
+	if !strings.HasPrefix(uploadLocation, "/") {
+		uploadLocation = "/" + uploadLocation
+	}
+	return uploadLocation
+}
+
+// parseTusConcatFinal extracts the partial upload ids from an Upload-Concat
+// final header. Each reference may be an absolute URL or a path, must point at
+// this server's upload location, and may appear only once since concatenation
+// consumes the partial.
+func (fs *FilerServer) parseTusConcatFinal(concat string) ([]string, error) {
+	uploadsPrefix := fs.option.TusBasePath + "/.uploads/"
+	var partialIDs []string
+	seen := make(map[string]bool)
+	for _, ref := range strings.Fields(strings.TrimPrefix(concat, TusConcatFinalPrefix)) {
+		refURL, err := url.Parse(ref)
+		if err != nil {
+			return nil, fmt.Errorf("invalid partial upload reference %q", ref)
+		}
+		partialID := strings.TrimPrefix(refURL.Path, uploadsPrefix)
+		if partialID == refURL.Path || !isCanonicalTusUploadID(partialID) {
+			return nil, fmt.Errorf("invalid partial upload reference %q", ref)
+		}
+		if seen[partialID] {
+			return nil, fmt.Errorf("duplicate partial upload reference %q", ref)
+		}
+		seen[partialID] = true
+		partialIDs = append(partialIDs, partialID)
+	}
+	if len(partialIDs) == 0 {
+		return nil, errors.New("no partial uploads listed")
+	}
+	return partialIDs, nil
+}
+
+// tusConcatFinalHandler handles POST requests carrying Upload-Concat final. It
+// stitches the listed completed partial uploads, in order, into one entry at
+// the request's target path.
+func (fs *FilerServer) tusConcatFinalHandler(w http.ResponseWriter, r *http.Request, claims *security.SeaweedFilerClaims, concat string) {
+	ctx := context.WithoutCancel(r.Context())
+
+	// The final upload's length is the sum of the partial lengths.
+	if r.Header.Get("Upload-Length") != "" {
+		http.Error(w, "Upload-Length not allowed for a final upload", http.StatusBadRequest)
+		return
+	}
+	if r.ContentLength > 0 {
+		http.Error(w, "Cannot upload data to a final upload", http.StatusForbidden)
+		return
+	}
+
+	partialIDs, err := fs.parseTusConcatFinal(concat)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	targetPath := fs.tusTargetPath(r)
+	if targetPath == "" || targetPath == "/" {
+		http.Error(w, "Target path required", http.StatusBadRequest)
+		return
+	}
+	if fs.filer.FilerConf.MatchStorageRule(targetPath).ReadOnly {
+		http.Error(w, ErrReadOnly.Error(), http.StatusInsufficientStorage)
+		return
+	}
+
+	// Every partial must exist, be authorized for this credential, and be
+	// complete; concatenation-unfinished is not offered. Each one is claimed
+	// with an exclusive consumed marker before its chunks are read, so a
+	// concurrent final cannot consume the same partial and a concurrent DELETE
+	// or expiry cleanup cannot free chunks that move to the final entry.
+	var partials []*TusSession
+	var claimedIDs []string
+	var totalSize int64
+	releaseClaims := func() {
+		for _, claimedID := range claimedIDs {
+			fs.rollbackTusSessionConsumed(ctx, claimedID)
+		}
+	}
+	for _, partialID := range partialIDs {
+		partial, err := fs.readTusSessionInfo(ctx, partialID)
+		if err != nil {
+			glog.V(1).Infof("TUS partial %s not resolved: %v", partialID, err)
+			releaseClaims()
+			http.Error(w, "Partial upload not found", http.StatusNotFound)
+			return
+		}
+		if !authorizeFilerJwtPaths(r, claims, []string{partial.TargetPath}) {
+			releaseClaims()
+			writeJsonError(w, r, http.StatusUnauthorized, errors.New("wrong jwt"))
+			return
+		}
+		if !partial.isPartial() {
+			releaseClaims()
+			http.Error(w, "Not a partial upload: "+partialID, http.StatusBadRequest)
+			return
+		}
+		totalSize += partial.Size
+		if totalSize > fs.option.TusMaxSize {
+			releaseClaims()
+			http.Error(w, "Combined upload size exceeds maximum", http.StatusRequestEntityTooLarge)
+			return
+		}
+		if err := fs.claimTusPartial(ctx, partial); err != nil {
+			releaseClaims()
+			switch {
+			case errors.Is(err, filer_pb.ErrEntryAlreadyExists):
+				http.Error(w, "Partial upload already consumed: "+partialID, http.StatusConflict)
+			case errors.Is(err, filer_pb.ErrNotFound):
+				glog.V(1).Infof("TUS partial %s changed before concatenation: %v", partialID, err)
+				http.Error(w, "Partial upload not found", http.StatusNotFound)
+			default:
+				glog.Errorf("Failed to claim TUS partial %s: %v", partialID, err)
+				http.Error(w, "Failed to create upload", http.StatusInternalServerError)
+			}
+			return
+		}
+		claimedIDs = append(claimedIDs, partialID)
+		if partial.Offset != partial.Size {
+			releaseClaims()
+			http.Error(w, "Partial upload not finished: "+partialID, http.StatusBadRequest)
+			return
+		}
+		partials = append(partials, partial)
+	}
+
+	metadata := parseTusMetadata(r.Header.Get("Upload-Metadata"))
+	uploadID := uuid.New().String()
+	session, err := fs.createTusSession(ctx, uploadID, targetPath, totalSize, metadata, concat)
+	if err != nil {
+		glog.Errorf("Failed to create TUS session: %v", err)
+		releaseClaims()
+		http.Error(w, "Failed to create upload", http.StatusInternalServerError)
+		return
+	}
+
+	// Re-base each partial's chunks onto the final upload's offset space.
+	for _, partial := range partials {
+		for _, chunk := range partial.Chunks {
+			session.Chunks = append(session.Chunks, &TusChunkInfo{
+				Offset:   session.Offset + chunk.Offset,
+				Size:     chunk.Size,
+				FileId:   chunk.FileId,
+				UploadAt: chunk.UploadAt,
+			})
+		}
+		session.Offset += partial.Size
+	}
+
+	if err := fs.completeTusUpload(ctx, session); err != nil {
+		fs.deleteTusSession(ctx, uploadID)
+		releaseClaims()
+		glog.Errorf("Failed to complete TUS concatenation: %v", err)
+		writeTusCompleteError(w, err)
+		return
+	}
+
+	// The chunks now belong to the final entry, so remove only the partials'
+	// session metadata.
+	for _, partial := range partials {
+		if err := fs.filer.DeleteEntryMetaAndData(ctx, util.FullPath(fs.tusSessionPath(partial.ID)), true, false, false, false, nil, 0); err != nil {
+			glog.V(1).Infof("Failed to cleanup TUS partial session %s: %v", partial.ID, err)
+		}
+	}
+
+	w.Header().Set("Location", fs.tusUploadLocation(uploadID))
+	w.WriteHeader(http.StatusCreated)
+}
+
 // tusHeadHandler handles HEAD requests to get current upload offset
 func (fs *FilerServer) tusHeadHandler(w http.ResponseWriter, session *TusSession) {
+	if session.Concat != "" {
+		w.Header().Set("Upload-Concat", session.Concat)
+	}
 	w.Header().Set("Upload-Offset", strconv.FormatInt(session.Offset, 10))
 	w.Header().Set("Upload-Length", strconv.FormatInt(session.Size, 10))
 	w.Header().Set("Cache-Control", "no-store")
@@ -297,6 +479,11 @@ func (fs *FilerServer) tusHeadHandler(w http.ResponseWriter, session *TusSession
 
 // tusPatchHandler handles PATCH requests to upload data
 func (fs *FilerServer) tusPatchHandler(w http.ResponseWriter, r *http.Request, session *TusSession) {
+	if session.isFinal() {
+		http.Error(w, "Cannot PATCH a final upload", http.StatusForbidden)
+		return
+	}
+
 	// Use a context that ignores cancellation from the request context.
 	// The filer's connection has an inactivity timeout: after the request body is fully read,
 	// internal operations (assigning file IDs, uploading to volume servers, completing uploads)
@@ -348,8 +535,9 @@ func (fs *FilerServer) tusPatchHandler(w http.ResponseWriter, r *http.Request, s
 
 	newOffset := uploadOffset + bytesWritten
 
-	// Check if upload is complete
-	if newOffset == session.Size {
+	// Check if upload is complete; a partial upload keeps its chunks for a later
+	// concatenation instead of landing at the target path.
+	if newOffset == session.Size && !session.isPartial() {
 		// Ensure the authorized session still exists, then refresh its chunks.
 		if err = fs.refreshTusSessionChunks(ctx, session); err != nil {
 			glog.Errorf("Failed to get updated TUS session: %v", err)
diff --git a/weed/server/filer_server_tus_jwt_test.go b/weed/server/filer_server_tus_jwt_test.go
index c8291ed2b..875a3ef84 100644
--- a/weed/server/filer_server_tus_jwt_test.go
+++ b/weed/server/filer_server_tus_jwt_test.go
@@ -46,9 +46,10 @@ func newTusTestServer(t *testing.T, sessions map[string]string) (*FilerServer, *
 	t.Helper()
 	store := newRenameTestStore()
 	fs := &FilerServer{
-		filer:      newRenameTestFiler(t, store),
-		filerGuard: security.NewGuard(nil, tusTestWriteKey, 0, tusTestReadKey, 0),
-		option:     &FilerOption{TusBasePath: "/.tus", TusMaxSize: TusDefaultMaxSize},
+		filer:          newRenameTestFiler(t, store),
+		filerGuard:     security.NewGuard(nil, tusTestWriteKey, 0, tusTestReadKey, 0),
+		option:         &FilerOption{TusBasePath: "/.tus", TusMaxSize: TusDefaultMaxSize},
+		entryLockTable: util.NewLockTable[util.FullPath](),
 	}
 	for uploadID, targetPath := range sessions {
 		seedTusSession(t, fs, store, TusSession{ID: uploadID, TargetPath: targetPath, Size: 1})
diff --git a/weed/server/filer_server_tus_session.go b/weed/server/filer_server_tus_session.go
index 5c0494d44..e530ed7d8 100644
--- a/weed/server/filer_server_tus_session.go
+++ b/weed/server/filer_server_tus_session.go
@@ -25,8 +25,11 @@ const (
 	TusDefaultSessionExpiry = 24 * time.Hour
 	TusUploadsFolder        = ".uploads.tus"
 	TusInfoFileName         = ".info"
+	TusConsumedFileName     = ".consumed"
 	TusChunkExt             = ".chunk"
-	TusExtensions           = "creation,creation-with-upload,termination"
+	TusExtensions           = "creation,creation-with-upload,termination,concatenation"
+	TusConcatPartial        = "partial"
+	TusConcatFinalPrefix    = "final;"
 )
 
 // ErrWormEnforced marks a TUS completion rejected because the target entry is
@@ -43,9 +46,20 @@ type TusSession struct {
 	Metadata   map[string]string `json:"metadata,omitempty"`
 	CreatedAt  time.Time         `json:"created_at"`
 	ExpiresAt  time.Time         `json:"expires_at,omitempty"`
+	Concat     string            `json:"concat,omitempty"`
 	Chunks     []*TusChunkInfo   `json:"chunks,omitempty"`
 }
 
+// isPartial reports whether the session is a concatenation partial upload: it
+// holds chunks for a later final upload instead of landing at its target path.
+func (session *TusSession) isPartial() bool {
+	return session.Concat == TusConcatPartial
+}
+
+func (session *TusSession) isFinal() bool {
+	return strings.HasPrefix(session.Concat, TusConcatFinalPrefix)
+}
+
 // TusChunkInfo tracks individual chunk uploads within a session
 type TusChunkInfo struct {
 	Offset   int64  `json:"offset"`
@@ -69,6 +83,68 @@ func (fs *FilerServer) tusSessionInfoPath(uploadID string) string {
 	return fmt.Sprintf("/%s/%s/%s", TusUploadsFolder, uploadID, TusInfoFileName)
 }
 
+// tusSessionConsumedPath returns the path of the marker recording that a
+// session's chunks belong to a completed upload and must not be freed with it.
+func (fs *FilerServer) tusSessionConsumedPath(uploadID string) string {
+	return fmt.Sprintf("/%s/%s/%s", TusUploadsFolder, uploadID, TusConsumedFileName)
+}
+
+// markTusSessionConsumed claims a session's chunks for a completed upload. With
+// exclusive set, a session already claimed by a concurrent request fails with
+// filer_pb.ErrEntryAlreadyExists so one partial cannot be consumed twice.
+func (fs *FilerServer) markTusSessionConsumed(ctx context.Context, uploadID string, exclusive bool) error {
+	return fs.filer.CreateEntry(ctx, &filer.Entry{
+		FullPath: util.FullPath(fs.tusSessionConsumedPath(uploadID)),
+		Attr: filer.Attr{
+			Mode:   0644,
+			Crtime: time.Now(),
+			Mtime:  time.Now(),
+			Uid:    OS_UID,
+			Gid:    OS_GID,
+		},
+	}, nil, exclusive, false, nil, true, fs.filer.MaxFilenameLength)
+}
+
+// isTusSessionConsumed fails closed: when the marker cannot be looked up, the
+// caller must not treat the session's chunks as free.
+// claimTusPartial claims a partial for one final upload, serialized per session
+// on this filer, and re-verifies the pinned session under the claim. A failed
+// verification releases the claim before returning.
+func (fs *FilerServer) claimTusPartial(ctx context.Context, partial *TusSession) error {
+	sessionPath := util.FullPath(fs.tusSessionPath(partial.ID))
+	pathLock := fs.entryLockTable.AcquireLock("tusClaim", sessionPath, util.ExclusiveLock)
+	defer fs.entryLockTable.ReleaseLock(sessionPath, pathLock)
+
+	if err := fs.markTusSessionConsumed(ctx, partial.ID, true); err != nil {
+		return err
+	}
+	if err := fs.refreshTusSessionChunks(ctx, partial); err != nil {
+		fs.rollbackTusSessionConsumed(ctx, partial.ID)
+		return err
+	}
+	return nil
+}
+
+// rollbackTusSessionConsumed releases a consumed marker after a failed claim or
+// completion. A failed rollback wedges the session as consumed: DELETE and
+// expiry then preserve its chunks, which leak until removed by fsck.
+func (fs *FilerServer) rollbackTusSessionConsumed(ctx context.Context, uploadID string) {
+	if err := fs.filer.DeleteEntryMetaAndData(ctx, util.FullPath(fs.tusSessionConsumedPath(uploadID)), false, false, false, false, nil, 0); err != nil && !errors.Is(err, filer_pb.ErrNotFound) {
+		glog.Errorf("TUS session %s wedged as consumed, marker rollback failed: %v", uploadID, err)
+	}
+}
+
+func (fs *FilerServer) isTusSessionConsumed(ctx context.Context, uploadID string) (bool, error) {
+	_, err := fs.filer.FindEntry(ctx, util.FullPath(fs.tusSessionConsumedPath(uploadID)))
+	if err == nil {
+		return true, nil
+	}
+	if errors.Is(err, filer_pb.ErrNotFound) {
+		return false, nil
+	}
+	return false, err
+}
+
 // tusChunkPath returns the path to store a chunk info file
 // Format: /{TusUploadsFolder}/{uploadID}/chunk_{offset}_{size}_{encodedFileId}
 func (fs *FilerServer) tusChunkPath(uploadID string, offset, size int64, fileId string) string {
@@ -117,7 +193,7 @@ func parseTusChunkPath(entry *filer.Entry) (*TusChunkInfo, error) {
 }
 
 // createTusSession creates a new TUS upload session
-func (fs *FilerServer) createTusSession(ctx context.Context, uploadID, targetPath string, size int64, metadata map[string]string) (*TusSession, error) {
+func (fs *FilerServer) createTusSession(ctx context.Context, uploadID, targetPath string, size int64, metadata map[string]string, concat string) (*TusSession, error) {
 	session := &TusSession{
 		ID:         uploadID,
 		TargetPath: targetPath,
@@ -126,6 +202,7 @@ func (fs *FilerServer) createTusSession(ctx context.Context, uploadID, targetPat
 		Metadata:   metadata,
 		CreatedAt:  time.Now(),
 		ExpiresAt:  time.Now().Add(fs.option.TusSessionExpiry),
+		Concat:     concat,
 		Chunks:     []*TusChunkInfo{},
 	}
 
@@ -288,11 +365,9 @@ func (fs *FilerServer) loadTusSessionChunks(ctx context.Context, session *TusSes
 	return nil
 }
 
-// refreshTusSessionChunks verifies the pinned session still exists and still
-// identifies the same upload before refreshing its chunk state, so a PATCH
-// cannot complete after a concurrent DELETE or metadata replacement and land at
-// a TargetPath other than the one that was authorized.
-func (fs *FilerServer) refreshTusSessionChunks(ctx context.Context, session *TusSession) error {
+// verifyTusSessionUnchanged confirms the stored .info still identifies the same
+// pinned session.
+func (fs *FilerServer) verifyTusSessionUnchanged(ctx context.Context, session *TusSession) error {
 	stored, err := fs.readTusSessionInfo(ctx, session.ID)
 	if err != nil {
 		return err
@@ -300,6 +375,17 @@ func (fs *FilerServer) refreshTusSessionChunks(ctx context.Context, session *Tus
 	if stored.TargetPath != session.TargetPath || stored.Size != session.Size || !stored.CreatedAt.Equal(session.CreatedAt) {
 		return fmt.Errorf("TUS session identity changed: %s", session.ID)
 	}
+	return nil
+}
+
+// refreshTusSessionChunks verifies the pinned session still exists and still
+// identifies the same upload before refreshing its chunk state, so a PATCH
+// cannot complete after a concurrent DELETE or metadata replacement and land at
+// a TargetPath other than the one that was authorized.
+func (fs *FilerServer) refreshTusSessionChunks(ctx context.Context, session *TusSession) error {
+	if err := fs.verifyTusSessionUnchanged(ctx, session); err != nil {
+		return err
+	}
 	return fs.loadTusSessionChunks(ctx, session)
 }
 
@@ -333,6 +419,9 @@ func (fs *FilerServer) saveTusChunk(ctx context.Context, uploadID string, chunk
 
 // deleteTusSession removes a TUS upload session and all its data
 func (fs *FilerServer) deleteTusSession(ctx context.Context, uploadID string) error {
+	sessionPath := util.FullPath(fs.tusSessionPath(uploadID))
+	pathLock := fs.entryLockTable.AcquireLock("tusDelete", sessionPath, util.ExclusiveLock)
+	defer fs.entryLockTable.ReleaseLock(sessionPath, pathLock)
 
 	session, err := fs.getTusSession(ctx, uploadID)
 	if err != nil {
@@ -341,8 +430,21 @@ func (fs *FilerServer) deleteTusSession(ctx context.Context, uploadID string) er
 		return nil
 	}
 
-	// Batch delete all uploaded chunks from volume servers
-	if len(session.Chunks) > 0 {
+	// Remove the .info before deciding about chunk data: a final request claims
+	// its consumed marker before re-verifying the .info, so once the .info is
+	// gone no new claim can pass verification, and a claim that did pass was
+	// created earlier and is visible at the check below.
+	if err := fs.filer.DeleteEntryMetaAndData(ctx, util.FullPath(fs.tusSessionInfoPath(uploadID)), false, false, false, false, nil, 0); err != nil && !errors.Is(err, filer_pb.ErrNotFound) {
+		return fmt.Errorf("delete session info: %w", err)
+	}
+
+	// Batch delete all uploaded chunks from volume servers, unless the session
+	// was consumed: then the chunks belong to a completed upload's entry.
+	consumed, err := fs.isTusSessionConsumed(ctx, uploadID)
+	if err != nil {
+		return fmt.Errorf("check consumed marker: %w", err)
+	}
+	if len(session.Chunks) > 0 && !consumed {
 		var chunksToDelete []*filer_pb.FileChunk
 		for _, chunk := range session.Chunks {
 			if chunk.FileId != "" {
@@ -370,6 +472,12 @@ func (fs *FilerServer) completeTusUpload(ctx context.Context, session *TusSessio
 		return fmt.Errorf("upload incomplete: offset=%d, expected=%d", session.Offset, session.Size)
 	}
 
+	// Serialize the ownership transition with deleteTusSession on this filer;
+	// the marker/.info handshake below covers a delete served by another filer.
+	sessionPath := util.FullPath(fs.tusSessionPath(session.ID))
+	pathLock := fs.entryLockTable.AcquireLock("tusComplete", sessionPath, util.ExclusiveLock)
+	defer fs.entryLockTable.ReleaseLock(sessionPath, pathLock)
+
 	// Sort chunks by offset to ensure correct order
 	sort.Slice(session.Chunks, func(i, j int) bool {
 		return session.Chunks[i].Offset < session.Chunks[j].Offset
@@ -428,6 +536,23 @@ func (fs *FilerServer) completeTusUpload(ctx context.Context, session *TusSessio
 		return ErrWormEnforced
 	}
 
+	// Claim the chunks for the entry before creating it: once the marker is
+	// durable, a failed cleanup below cannot lead DELETE or expiry to free the
+	// entry's chunks. If the entry creation then fails, the client retry re-runs
+	// completion; an abandoned marked session leaks its chunks instead of
+	// corrupting a live entry.
+	if err := fs.markTusSessionConsumed(ctx, session.ID, false); err != nil {
+		return fmt.Errorf("mark session consumed: %w", err)
+	}
+
+	// Handshake with deleteTusSession, which removes the .info before checking
+	// the marker: a session whose .info is still present here cannot have its
+	// chunks freed by a delete that missed the marker just made durable.
+	if err := fs.verifyTusSessionUnchanged(ctx, session); err != nil {
+		fs.rollbackTusSessionConsumed(ctx, session.ID)
+		return fmt.Errorf("session deleted before completion: %w", err)
+	}
+
 	entry := &filer.Entry{
 		FullPath: targetPath,
 		Attr: filer.Attr{