Well, I know that vfs shims can be nested. However, the problem here is that if a user specifies a different vfs using the vfs URI parameter, the parameter is handled by SQLite internally. For example, if "vfstrace" is enabled in the SQLite shell, the tracing vfs shim is set as the default vfs, typically using the previous default vfs as the underlying vfs. However, if the user now uses the vfs URI parameter to select a different vfs, e.g. "unix-excl", tracing will no longer occur. My question is whether there is a way to let the user select a vfs via URI, but still keep the vfs shim enabled. In the example, the effect should be that "trace" vfs shim uses "unix-excl" as the underlying vfs, if the user specifies the URI parameter "vfs=unix-excl". Currently, "unix-excl" would be used without "trace".