Set DSH_E2E_MAX_WORKERS=4 for the credentialed e2e workflow and pin that environment contract in the workflow test. Profile-launched SDK and ACP scenarios each boot a complete subprocess tree, so the previous file-level fan-out could multiply process and provider pressure far beyond the runner's useful concurrency.
The bound changes scheduling only: every e2e file still runs, the Vitest configuration retains its explicit override knob, and local callers can choose a different positive worker count when their resources allow it.
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