s3api: fix ListObjectsV2 NextContinuationToken duplication for nested prefix (#8294)

* s3api: fix duplicate ListObjectsV2 continuation token for nested prefix

* s3api: include prefix in common-prefix continuation token

weed/s3api/s3api_object_handlers_list.go

@@ -351,25 +351,8 @@ func (s3a *S3ApiServer) listFilerEntries(bucket string, originalPrefix string, m
 			}
 
 			// Adjust nextMarker for CommonPrefixes to include trailing slash (AWS S3 compliance)
-			if cursor.isTruncated && lastEntryWasCommonPrefix && lastCommonPrefixName != "" {
-				// For CommonPrefixes, NextMarker should include the trailing slash
-				if requestDir != "" {
-					if prefix != "" {
-						nextMarker = requestDir + "/" + prefix + "/" + lastCommonPrefixName + "/"
-					} else {
-						nextMarker = requestDir + "/" + lastCommonPrefixName + "/"
-					}
-				} else {
-					nextMarker = lastCommonPrefixName + "/"
-				}
-			} else if cursor.isTruncated {
-				if requestDir != "" {
-					if prefix != "" {
-						nextMarker = requestDir + "/" + prefix + "/" + nextMarker
-					} else {
-						nextMarker = requestDir + "/" + nextMarker
-					}
-				}
+			if cursor.isTruncated {
+				nextMarker = buildTruncatedNextMarker(requestDir, prefix, nextMarker, lastEntryWasCommonPrefix, lastCommonPrefixName)
 			}
 
 			if cursor.isTruncated {
@@ -480,6 +463,28 @@ func toParentAndDescendants(dirAndName string) (dir, name string) {
 	return
 }
 
+func buildTruncatedNextMarker(requestDir, prefix, nextMarker string, lastEntryWasCommonPrefix bool, lastCommonPrefixName string) string {
+	if lastEntryWasCommonPrefix && lastCommonPrefixName != "" {
+		// For CommonPrefixes, NextMarker should include the trailing slash
+		if requestDir != "" {
+			if prefix != "" {
+				return requestDir + "/" + prefix + "/" + lastCommonPrefixName + "/"
+			}
+			return requestDir + "/" + lastCommonPrefixName + "/"
+		}
+		if prefix != "" {
+			return prefix + "/" + lastCommonPrefixName + "/"
+		}
+		return lastCommonPrefixName + "/"
+	}
+
+	if requestDir != "" {
+		return requestDir + "/" + nextMarker
+	}
+
+	return nextMarker
+}
+
 func (s3a *S3ApiServer) doListFilerEntries(client filer_pb.SeaweedFilerClient, dir, prefix string, cursor *ListingCursor, marker, delimiter string, inclusiveStartFrom bool, bucket string, eachEntryFn func(dir string, entry *filer_pb.Entry)) (nextMarker string, err error) {
 	// invariants
 	//   prefix and marker should be under dir, marker may contain "/"

weed/s3api/s3api_object_handlers_list_test.go

@@ -148,6 +148,26 @@ func Test_normalizePrefixMarker(t *testing.T) {
 	}
 }
 
+func TestBuildTruncatedNextMarker(t *testing.T) {
+	t.Run("does not duplicate prefix segment in next continuation token", func(t *testing.T) {
+		prefix := "export_2026-02-10_17-00-23"
+		nextMarker := "export_2026-02-10_17-00-23/4156000e.jpg"
+
+		actual := buildTruncatedNextMarker("xemu", prefix, nextMarker, false, "")
+		assert.Equal(t, "xemu/export_2026-02-10_17-00-23/4156000e.jpg", actual)
+	})
+
+	t.Run("keeps common prefix marker trailing slash", func(t *testing.T) {
+		actual := buildTruncatedNextMarker("xemu", "export_2026-02-10_17-00-23", "", true, "nested")
+		assert.Equal(t, "xemu/export_2026-02-10_17-00-23/nested/", actual)
+	})
+
+	t.Run("includes prefix for common prefix marker when request dir is empty", func(t *testing.T) {
+		actual := buildTruncatedNextMarker("", "foo", "", true, "bar")
+		assert.Equal(t, "foo/bar/", actual)
+	})
+}
+
 func TestAllowUnorderedParameterValidation(t *testing.T) {
 	// Test getListObjectsV1Args with allow-unordered parameter
 	t.Run("getListObjectsV1Args with allow-unordered", func(t *testing.T) {