Currently, the GoogleCloudStorageAdapter::listContents() method automatically appends a / to the provided path to build the prefix option for the underlying Bucket::objects() call:

if (! empty($prefixedPath)) { $options = ['prefix' => sprintf('%s/', rtrim($prefixedPath, '/'))]; }

This means that listContents('incoming') correctly lists objects under incoming/, but calling:
listContents('incoming/prefix_file_', false)

does not list objects whose names start with prefix_file_, because the adapter is forcing a “directory-like” behavior by appending /.

This is a limitation, because Google Cloud Storage natively supports prefix filtering for arbitrary filename prefixes, not just directory prefixes.

Why this matters
• This matches GCS’s native capabilities (prefix filtering is powerful & efficient server-side).
• It avoids listing entire buckets and filtering client-side for common patterns.
• It allows Flysystem users to use listContents() for real-world scenarios with file prefixes at scale.