CircleCI "Too many concurrent runs" - Plan Concurrency Limit

Each CircleCI plan caps how many jobs run at once. When that cap is hit, new jobs sit queued until capacity frees up; they are not failing, just waiting.

What this error means

Jobs stay queued for a long time, and the UI indicates the concurrency limit has been reached for the plan.

circleci

Too many concurrent runs. Your plan allows 5 concurrent jobs.
This job is queued and will start when capacity is available.

Common causes

Concurrency cap reached

Running jobs already use all the concurrency the plan allows.

Fan-out workflows

Large matrix or parallel workflows consume many slots at once.

How to fix it

Reduce simultaneous demand

Limit fan-out or serialize non-critical jobs to fit within the cap.

Trim matrix sizes or parallelism on non-critical jobs.
Cancel redundant in-progress workflows.
Stagger heavy workflows so they do not all run together.

Raise the plan limit

Open Plan then Usage in the CircleCI app.
Increase the concurrency allowance if needed.
Re-run queued workflows once capacity is available.

How to prevent it

Right-size matrix and parallelism to the plan concurrency.
Auto-cancel redundant workflows on new pushes.
Monitor concurrency usage during peak hours.