DocumentationParallel ExecutionConfiguring workers

Configuring workers

5 min readLast updated 2026-04-20

Scale from 1 to 250 parallel workers with automatic sharding and resource-aware scheduling.

Check Studio distributes tests across workers using a combination of file-level sharding and test-level splitting. Configure workers via CLI flag or config file.

CLI flag

checkstudio run --workers=8
bash

Config file

// checkstudio.config.js
module.exports = {
  workers: 8,
  maxFailures: 5, // Stop early if too many tests fail
  retries: 1,     // Retry flaky tests once
};
javascript

How sharding works

Check Studio records test duration history and uses weighted round-robin to balance slow and fast tests across workers. This minimizes total wall-clock time.

Resource limits

Each worker uses one browser context. For memory-constrained CI runners, reduce workers or use headless mode with --headless.

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