In CSF 2.5 the Session.config setting ParticipantConfiguration/ProxyCacheDirectoryPath is used to specify the directory for the WSDL cache used by CSF when Sessions are created. If you're a developer intent on implementing a particular service contract, forgetting about this cache might cost you a couple of hours of frustration.
Let's say I build a service at http://MyMachine/MyVdir/sl.ashx implementing SOAP action MyAction. I then try to create a Session in which the service is a participant, but unfortunately, the Session expects my service to have SOAP action http://MyCompany/MyAction. CSF will create a cache file consisting of the URI as the top line, and the first draft WSDL as the remainder of the file. Until the cache expires (and the default is 24 hours), nothing done to fix the action will work; not building, not bouncing IIS, etc. Until you delete the cached WSDL or it expires, CSF will find the file based on the URI, and use the WSDL from it.
Relevant Session.config settings:
ParticipantConfiguration/ProxyCacheDirectoryPath
ParticipantConfiguration/ProxyCacheFileExpirationTime
Default cache directories in CSF 2.5:
Developer Edition: C:\Program Files\Microsoft CSF\CSFDeveloper\Temp\
Standard edition:
C:\csf\session\participant\cache\*.*