File cards ("Download and open") fail in Cowork and local desktop sessions; Cowork has no /bug to report it

Summary

File cards in the chat transcript ("Download" / "Download and open") do not deliver files in either Cowork sessions or local Claude Code sessions in the desktop app. The only reliable delivery is the agent writing the file to a real path on the host and revealing it in Finder.

Environment

• Claude desktop app 1.25927.0 (macOS)
• Claude Code CLI 2.1.222
• macOS 26.6 (Darwin 25.6.0)

Behavior

Cowork sessions: clicking "Download and open" on a file card shows the error toast "Unable to open file." This happens even when the session correctly wrote the file to a synced host folder before ending. Best guess at the cause: the card points at the path where the file was created inside the session VM, and that path stops existing when the VM shuts down. The host copy is fine; the card can't reach it.

Local Claude Code sessions (desktop app): the file card renders with no working Download and no "Show in folder" button at all, so there is no way to act on the card. First verified 2026-07-24, still true today.

Repro (Cowork)

1. Start a Cowork session, have it produce any file deliverable and write it to a workspace folder that syncs to the host.
2. Let the session end (VM stops).
3. Click "Download and open" on the file card in the transcript.
4. Error toast: "Unable to open file." The file exists on the host and opens fine from Finder.

Expected

The card should resolve to the host copy of the file when one exists, or state clearly that the file is no longer available, instead of a dead button.

Workaround

Instruct the agent (via CLAUDE.md) to always write deliverables to a real host folder, run open -R, and give the full path in the reply, treating the card as decoration. This works but shouldn't be necessary.

Filed from a Claude Code session because /bug is not available inside Cowork sessions, which is its own small gap: the surface with the bug has no way to report the bug.