Reproduction:

https://prettier.io/playground/#N4Igxg9gdgLgprEAuEA6AZhCACYAdKbbAWmIFsBPYgNwEMAnJbAS0IgGsAbWgIwBoA3AQC+IPiAgAHGM2gBnZKAb0IAdwAKDBApS1Oq2hQXie9WmHZwYAZVpk4AGVZxk6PXLgmzFq9cnnWAHNkGHoAV08QDzJmEPDIuAAPSTh6ZntYPQAVVKgGZjgdN04PcTkgzjgARTCIeFd3SIArOUTrCura+qRi0pAARy64dRVJHRBaOWIoODgAE3mxEFDaZk4ggGEIMjJaZAnOTiXyqEDKgEEYUOYeMPh1VKcZhpLIgAsYMk4AdTfmeDk-jAcGs2n+zGo-wo+zAcmMIGoEQAklAFrBrGA0tJzqjrDAKJUXn1JCoPN8zJJ9iTCqlqC5xKwPPQYCNaIFdkTIv56EyYXCliTWDBvsw5jA3sgABwABnE9Dgg2Y8tZ7L2PUa4hgvBFYolSAATOIwh4srwihqQHAyDx5gs5g5aKcwmy4AAxCD0XZXIL7Wh3CAgYTCIA

Prettier strips trailing commas from CSS variables which changes the actual value of the CSS variable:

/* Input */
.foo {
  --my-var: in oklab,;
}

/* Output */

.foo {
  --my-var: in oklab;
}

This breaks situations like this, where the comma needs to be included when resolving the variable at run-time:

.in-oklab {
  --interpolation-method: in oklab,;
}

.radial-gradient {
  background-image: radial-gradient(var(--interpolation-method,) black, white));
}

In that example the comma is necessary if --interpolation-method is defined, but if it's not defined you need to make sure the comma is not there.