A new scratchpad directory location can now be announced to Claude alongside platform and shell info.
A new scratchpadDirectory field is added to the environment-context schema alongside workingDirectory, platform, and shell. When present, the system prompt gets a line: 'Scratchpad directory: — always use it for temporary files... instead of /tmp', and it also appears in the initial environment info block. The directory is computed as <tmpdir>/<sessionId>/scratchpad.
Context-change messages sent to the model support a scratchpadDirectory case for announcing the location, and a removal case telling the model 'The scratchpad directory announced earlier is no longer available; use it no further.'