s3api: include prefix in common-prefix continuation token

weed/s3api/s3api_object_handlers_list.go

@@ -472,6 +472,9 @@ func buildTruncatedNextMarker(requestDir, prefix, nextMarker string, lastEntryWa
 			}
 			return requestDir + "/" + lastCommonPrefixName + "/"
 		}
+		if prefix != "" {
+			return prefix + "/" + lastCommonPrefixName + "/"
+		}
 		return lastCommonPrefixName + "/"
 	}
 

weed/s3api/s3api_object_handlers_list_test.go

@@ -161,6 +161,11 @@ func TestBuildTruncatedNextMarker(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) {