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Two new gauges on the Merge Queue Prometheus endpoint make it easy to track CI capacity separately from the number of PRs under test. Previously, testing activity was reported as a single number, which conflated CI slot usage with the number of PRs in flight when batching was on. The endpoint now exposes:
  • mq_testing_slots_active — number of active CI slots currently in use. A batch counts as one slot, so this maps directly to CI concurrency.
  • mq_prs_testing — number of PRs currently in the TESTING state. With batching enabled, this can exceed mq_testing_slots_active because several PRs share a slot.
Use mq_testing_slots_active for CI utilization alerts against your configured concurrency, and mq_prs_testing when you want to see how many PRs are being validated at once. Both metrics carry the standard repo, branch, and queue_type labels and are available at GET /v1/getMergeQueueMetrics alongside the existing point-in-time gauges and 1-hour window metrics. See Merge Queue metrics for the full metric reference and example PromQL queries.