PRODUCTION SCENARIO
A SaaS product lets each customer upload PDFs through the Files API and later ask questions about them. The frontend currently posts the customer's chosen file_id straight into the Messages request.
What should the team change to keep customer files isolated?
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Answer: Keep file IDs server-side, map them to users, and give each tenant its own workspace
Uploaded files are accessible to the entire workspace, so a user-supplied file_id would let one user read another's content. The docs say to treat file IDs as server-side references and to create a separate workspace per tenant, since the workspace is the isolation boundary; filenames, expiration, and citations do not restrict access.
Official Source: https://platform.claude.com/docs/en/build-with-claude/files ↗