Currently $changeStream pipelines error when the pipeline collation is non-simple. $changeStream pipelines should support non-simple collations. Comparisons within the $changeStream stage itself should use binary comparison (e.g. comparing namespace string, shard key, _id (comparing _id can also use the collection default collation)), but subsequent stages in the pipeline should use the pipeline collation as usual. This will allow users to do collation-aware comparisons in $match stages in a $changeStream pipeline, which is essential for users using collation.