Hi — good question. The cleanest way to do this is with task values, no REST API needed.

Approach: Task Values (Recommended)

In Child 1's notebook, capture its own run_id and set it as a task value:

import json

ctx = json.loads(

    dbutils.notebook.entry_point.getDbutils().notebook().getContext().toJson()

)

child1_run_id = ctx["currentRunId"]["id"]

dbutils.jobs.taskValues.set(key="child1_run_id", value=str(child1_run_id))

Then in your orchestrator job, when configuring Parent 2's job parameters, reference it with:

{{tasks.Parent1.values.child1_run_id}}

Task values set inside a child job are propagated back through the run_job task, so the orchestrator can access them via {{tasks.<run_job_task_name>.values.<key>}}.

Why not {{tasks.Parent1.run_id}}?

As you noticed, {{tasks.Parent1.run_id}} gives you the orchestrator's task run_id for the runjob task itself — not the child job's internal task runid. That's why task values are the right tool here: they let the child task explicitly publish its own metadata for upstream consumption.

REST API Fallback

If you can't modify Child 1's notebook, then yes, the REST API approach works:

1. Pass {{tasks.Parent1.run_id}} into an intermediate notebook task
2. Use the Runs Get API to fetch the triggered child job's run details and extract Child 1's task run_id from the tasks array

But if you can add a couple of lines to Child 1, the task values approach is simpler and avoids API calls entirely.

Docs:

• Task Values
• Dynamic Value References

Hope that helps!