Changes to filename_template checks

src/framework/mpas_stream_manager.F

@@ -563,10 +563,96 @@ subroutine MPAS_stream_mgr_validate_streams(manager, streamID, ierr)!{{{
 #endif
 
         end do
+
+        ! Only check filename_template uniqueness when validating all streams 
+        if (.not. present(streamID)) then
+            call MPAS_stream_mgr_check_filename_template(manager, ierr=err_local)
+            if (present(ierr)) ierr = err_local
+        end if
 
     end subroutine MPAS_stream_mgr_validate_streams!}}}
 
 
+    !-----------------------------------------------------------------------
+    !  routine MPAS_stream_mgr_check_filename_template
+    !
+    !> \brief Check for identical filename templates in active output streams.
+    !> \author Abishek Gopal
+    !> \date   June 3 2026
+    !> \details
+    !>  Checks that there are no identical filename templates among active output
+    !>  streams in the stream manager, which may lead to file conflicts. This
+    !>  routine can be called from within MPAS_stream_mgr_validate_streams or
+    !>  separately as needed.
+    !
+    !-----------------------------------------------------------------------
+    subroutine MPAS_stream_mgr_check_filename_template(manager, ierr)!{{{
+
+        implicit none
+
+        type (MPAS_streamManager_type), intent(inout) :: manager
+        integer, intent(out), optional :: ierr
+
+        integer :: threadNum
+        character (len=StrKIND) :: message, streamID
+        type (MPAS_stream_list_type), pointer :: stream1_cursor, stream2_cursor
+        logical :: stream1_pkg_active, stream2_pkg_active
+        logical :: stream1_output, stream2_output
+
+        STREAM_DEBUG_WRITE('-- Called MPAS_stream_mgr_check_filename_template() for all streams')
+
+        if (present(ierr)) ierr = MPAS_STREAM_MGR_NOERR
+
+        threadNum = mpas_threading_get_thread_num()
+
+        if ( threadNum == 0 ) then
+
+            streamID = '.*' !  query all streams
+
+            nullify(stream1_cursor)
+            do while (MPAS_stream_list_query(manager % streams, streamID, stream1_cursor))
+
+                stream1_pkg_active = stream_active_pkg_check(stream1_cursor)
+                stream1_output = (stream1_cursor % direction == MPAS_STREAM_OUTPUT) .or. &
+                                 (stream1_cursor % direction == MPAS_STREAM_INPUT_OUTPUT)
+
+                if (.not. stream1_cursor % active_stream .or. .not. stream1_output .or. .not. stream1_pkg_active) then
+                    cycle
+                end if
+
+                nullify(stream2_cursor)
+                do while (MPAS_stream_list_query(manager % streams, streamID, stream2_cursor))
+
+                    stream2_pkg_active = stream_active_pkg_check(stream2_cursor)
+                    stream2_output = (stream2_cursor % direction == MPAS_STREAM_OUTPUT) .or. &
+                                     (stream2_cursor % direction == MPAS_STREAM_INPUT_OUTPUT)
+
+                    ! uniqueness_check has already checked that two different streams do not have the same name
+                    if (trim(stream1_cursor % name) == trim(stream2_cursor % name) &
+                        .or. .not. stream2_cursor % active_stream &
+                        .or. .not. stream2_output &
+                        .or. .not. stream2_pkg_active) then
+                        cycle
+                    end if
+
+                    if (trim(stream1_cursor % filename_template) == trim(stream2_cursor % filename_template)) then
+                        message = 'Found identical values of the filename_template attribute for multiple active output streams, ' &
+                                  // trim(stream1_cursor % name) // ' and ' // trim(stream2_cursor % name) // &
+                                  ', in streams.<CORE>. This may result in file conflicts.'
+                        call mpas_log_write(message, messageType=MPAS_LOG_ERR)
+                        if (present(ierr)) ierr = MPAS_STREAM_MGR_ERROR
+                        return
+                    end if
+
+                end do
+
+            end do
+
+        end if
+
+    end subroutine MPAS_stream_mgr_check_filename_template!}}}
+
+
     !-----------------------------------------------------------------------
     !  routine MPAS_stream_mgr_destroy_stream
     !

src/framework/xml_stream_parser.c

@@ -486,13 +486,6 @@ int uniqueness_check(ezxml_t stream1, ezxml_t stream2)
 			fmt_err(msgbuf);
 			return 1;
 		}
-		if (strstr(type, "output") != NULL || strstr(type2, "output") != NULL){
-			if (strcmp(filename, filename2) == 0) {
-				snprintf(msgbuf, MSGSIZE, "Output streams \"%s\" and \"%s\" cannot share the filename_template \"%s\".", name, name2, filename);
-				fmt_err(msgbuf);
-				return 1;
-			}
-		}
 	}
 
 	return 0;