Angular Material changes behaviour without a version change

[aleoniz]

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

Angular Material has changed behaviour multiple times without updating its version in the application where it is used (not doing a single npm install, using exactly the same version). Specifically, using @angular/material@20.2.7, MatDrawer has changed from not having an animation to having it multiple times:

• Did not have animation at some point before 06/10/2025 (don't remember the exact date, in this case with @angular/material@20.2.5)
• Had an animation at 06/10/2025, 9:50 UTC (with @angular/material@20.2.5 or @angular/material@20.2.7)
• Did not have an animation at 08/10/2025, 11:48 UTC (with @angular/material@20.2.7)
• Did have an animation at 10/10/2025, 12:19 UTC (with @angular/material@20.2.7)

I have also observed these changes in the examples in https://material.angular.dev/components/sidenav/examples, which have suffered the same changes in animations in the same dates, but I cannot assure they have not changed the @angular/material version used.

Reproduction

Steps to reproduce:

• Create an Angular application that uses MatDrawer, install dependencies just once, and check how the drawer changes from having an animation to not having it in different dates.
• Or check how https://material.angular.dev/components/sidenav/examples changes from having an animation to not having it in different dates (in some cases without a release).

I know this is not easy to check if nobody else has noticed and it does not happen in the future (that would be fine). But if it happens again in the future, this will help resolve it.

Expected Behavior

Angular Material changes behaviour only with a version change

Actual Behavior

Angular Material changes behaviour without a version change

Environment

• Angular: 20.3.3
• CDK/Material: 20.2.7
• Browser(s): Edge/Chrome
• Operating System (e.g. Windows, macOS, Ubuntu): Windows

[crisbeto]

We haven't really changed the behavior of the drawer in a while and it has always had an animation by default. You might be observing #30796 if you've set up your OS to reduce motion.