[Bug] Claude Desktop 1.3883.0: present_files rejects non-primary userSelectedFolders

Bug Description
Subject: present_files access-check regression in Claude Desktop 1.3883.0 — rejects user-mounted folders What's broken The mcp__cowork__present_files MCP tool, bundled in the Claude Desktop app, has been narrowed to accept paths in only two locations: The session's outputs scratchpad (/sessions/<vm-name>/mnt/outputs/) The single "primary" workspace folder the session was launched into Any other folder mounted via userSelectedFolders is rejected with the error: not accessible on the user's computer. Expected behavior (worked until ~mid-April 2026): all folders in userSelectedFolders should be accepted. Actual behavior: only the primary workspace folder + scratchpad are accepted; secondary mounts are rejected even though the same paths are reachable via Read, Bash ls, and Glob from the same session. Repro Launch a Cowork session with multiple folders in userSelectedFolders (e.g. ~/Desktop/Claude Content Files/Doctor Media Group AND ~/Desktop/Claude Content Files/The Neurogenesis Project) From the session, call present_files with a path under either non-primary mount Tool returns not accessible on the user's computer Confirmed the file exists with ls from the same session Workaround discovered Copy the file to /sessions/<vm-name>/mnt/outputs/ first, then call present_files with the scratchpad path. The tool auto-copies it back to the user's outputs folder. This works but defeats the multi-folder workspace model and forces every cross-folder presentation to be a 2-step bash + tool call instead of one direct call. Environment Claude Desktop app version: 1.3883.0 (build 1.3883.0) macOS host Affects Cowork web sessions launched from this Desktop install Started failing approximately mid-April 2026; previously worked reliably across all mounted folders Why this matters For users with multi-project workspaces (the documented userSelectedFolders pattern), every file presentation outside the primary mount now requires manual workaround code in the session — or the session falls back to a bare path string and the user has to manually navigate. Significantly degrades the "click the file card to open it" workflow that previously worked.

Environment Info

• Platform: darwin
• Terminal: Apple_Terminal
• Version: 2.1.117
• Feedback ID: 3bde9030-6b98-4fca-a375-4bd8926a1454

Errors

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