[Desktop app] File viewer shows "Couldn't find this file" for files sent with SendUserFile outside the working directory

Product: Claude desktop app (macOS), Code tab

What happens

1. Claude writes a Markdown file outside the session's working directory (for example ~/Desktop/claude/plan.md).
2. Claude sends it with SendUserFile (display: "render"). A file card shows up in the chat.
3. Clicking the card opens the side panel, which shows "Couldn't find this file. It may have been deleted, or it lives outside the working directory." and a "Show in Finder" button.

The file exists. "Show in Finder" finds it.

What I expected

A file Claude sends on purpose with SendUserFile should open in the viewer, wherever it lives on disk. Or, if the location really isn't allowed, the tool should refuse the send (or tell the agent), so it doesn't hand me a card that can't open.

Why it matters

• It happens again and again. Plans and handover docs are often kept outside the repo on purpose, so they don't clutter git.
• The agent gets "1 file delivered", so it believes the send worked and keeps sending files the same way.
• The only workaround is adding the folder to the session by hand, which nobody would know to do.

Workaround

Add the folder to the session (the request_directory tool, or "add directory"). After that the file opens.

Environment

• macOS (Darwin 27.0.0), Claude desktop app, Code tab, 2026-10-02
• Model: Claude Opus 5.5