What causes a CancellationToken ignored in a Unity task?

Passing a CancellationToken does not stop work by itself; if the loop never calls ThrowIfCancellationRequested or checks IsCancellationRequested, the task runs to completion despite cancellation.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix a CancellationToken Being Ignored in a Unity Task

Quick answer: Check the token inside loops and at await points, pass it to every awaitable that accepts one, and tie a token to OnDestroy so tasks stop when the object dies.

You cancel a loading task on scene change, but it keeps running and then writes results into destroyed objects. Cancellation is cooperative: the token does nothing unless your code observes it. Here is how to make cancellation actually work.

How to fix it

1. Check the token in loops

Inside long loops call token.ThrowIfCancellationRequested(); each iteration so the task stops promptly when cancellation is requested.

2. Pass the token down

Forward the token to every awaitable that accepts one, for example await Task.Delay(ms, token), so awaits also unblock on cancellation.

3. Tie cancellation to lifetime

Create a CancellationTokenSource in Awake and call cts.Cancel() in OnDestroy so tasks bound to a MonoBehaviour stop when it is destroyed.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every Unity error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.

The errors you never hear about are the ones quietly costing you players. Visibility turns them into a worklist.