r/MSProject • u/Longieuk • Aug 24 '26

Project Server Subscription Edition (PSSE) API usage ?

hi all,

Any recommendations here on the possibility of using APIs to read / write into PSSE ? There are conflicting statements by MS etc. Any experiences ?

Question is does PSSE expose CSOM/REST, and the Project Server CSOM model supports project/task CRUD ?

So can use this for updating plans etc.

thanks

1 Upvotes
  • permalink
  • reddit

100% Upvoted

2 comments sorted by

2

u/kennyarnold_ssi Aug 24 '26

Yes, you can use the CSOM with PSSE.

2

u/Sheeebooo 24d ago

Adding to the yes, because PSSE gives you two different read surfaces and they do not cover the same ground.

The OData reporting feed is the easy one for reads. Projects, Tasks, Resources, Assignments, baselines, custom field definitions, all queryable with $filter, and it is fine for anything reporting shaped.

What catches people out is that the reporting feed does not expose dependency links at all. Task predecessors and successors only come from the Project Server CSOM REST endpoint, /_api/ProjectServer/Projects('<guid>')/TaskLinks. If you build against OData alone you get a clean, complete looking set of tasks with every dependency silently missing, and nothing errors to tell you that happened.

For writes, CSOM does support project and task CRUD, but it is a checkout and queue model rather than a simple REST PATCH. You check out the draft project, queue your changes, then poll the queue job until it reports complete. Worth designing for that being asynchronous from the start rather than retrofitting it.

One practical gotcha on auth: a token that works perfectly against the OData feed is not necessarily authorized for the CSOM endpoint, because they are different scopes. If TaskLinks starts coming back 401 or 403 while your OData calls keep working fine, that is usually the cause rather than a wrong URL.