The test jobs on the nextviya estate run as a batch identity that is not authorised to create sessions in the SAS Job Execution compute context - child service submissions via mx_execute all failed with 403. Default the test context to Compute Reusable (matching the target contextName) in the shared test init programs. Also give the chunk deploy helper a retry loop for the per-chunk sasjs run timeouts - estate cold-starts can exceed a single 300s window.