While it’s not a good practice, Project allows me to put a Finish No Later Than (FNLT) constraint on a summary task. Assume the project starts on May 1, has one summary task with a FNLT of June 30 and there is one lower level 5 day task with an As Late As Possible (ALAP) constraint. If the Calculate Multiple Critical paths option is enabled then the start/finish of the task is May 1 through May 5. However, if I disable Calculate Multiple Critical paths then the task jumps to June 26 through June 30. So with the Calculate Multiple Critical paths disabled, Project is creating slack through Jun 30 (based on the FNLT constraint on the summary). This seems wrong to me. Thoughts? Here’s my example: Example File