Trace back to an upstream project pipeline via API

Is it possible to trace back to an upstream project via GitLab API?
From the source field I can identify whether the pipeline is part of a multi-project pipeline but I cannot find any id that links upstream and downstream projects.

Pipeline Bridges API only shows downstream projects.

I have multiple projects that may or may not trigger the same downstream project. What I would like to do is go through the pipelines of the downstream project and find the upstream project that triggered it.


I recently had this problem as well and came up with the following solution.
Using the GraphQL Api you can reach the upstream project, which triggered the pipeline.

You can iterate over all pipelines in a project and read the upstream project there.

  project(fullPath: "%s") {
    pipelines(first: 100, after: %s) {
      pageInfo {
      nodes {
        upstream {
          project {

Further readings:

You might also have a look at this issue: