[BUG] Desktop (Windows): clicking a file/preview link in a detached session window does nothing — the preview pane never opens (works in the main window)

Preflight

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

What's Wrong?

In the Claude Code desktop app on Windows, when a session is opened in its own detached window (Open in -> New window), clicking a clickable file/preview link that Claude posted in the transcript does nothing in that detached window. The preview pane never opens.

The exact same link, clicked in the main Claude Code window, works correctly: it opens the file in the right-hand preview pane (e.g. a .png opens in the preview/browser pane). Clicked in the detached window, the click appears completely dead - no preview pane, no overlay, no focus change, no error, no indication whatsoever that the click was registered.

Steps to reproduce:

1. In a session, have Claude produce a response containing a clickable link to a local file - e.g. a link to a generated image or file under the project's claude files/temp/ folder. (These render as clickable file:// links / preview links in the transcript.)
2. In the main window, click the link -> the file opens in the right-hand preview pane. Works.
3. Open the same session in its own window via Open in -> New window.
4. In the detached window, click the same link.
5. Expected: the file opens in the preview pane of the detached window.
6. Actual: nothing happens in the detached window. The preview pane does not open.

To the user this reads as a broken/dead link and looks like a bug in the product - the identical link works in one window and silently does nothing in the other.

This looks like the same class of window-scoping defect already reported (and in one case already fixed) for other surfaces in detached windows:

• #86010 - Desktop (Windows): clicking an image in a detached window opened the viewer in the MAIN window; the detached window showed no response at all. Closed as completed - but the fix appears to have covered only the inline-image viewer, not the file-link -> preview-pane path this report is about.
• #82366 - detached session windows are missing the pane buttons (Views menu). If the detached window has no preview pane at all, a link whose action is "open in the preview pane" has nowhere to go, which may be the root cause here.
• #82924 - /btw side chat does not work in detached windows (Windows).
• #62449 - detached/pop-out windows ignore zoom level.

In each of these, some piece of UI state or input handling is bound to the main window rather than to the window that owns the session. The file-link -> preview-pane action appears to have the same root cause: either the click is routed to the main window's preview pane (as the image viewer was before #86010 was fixed), or the detached window has no preview pane to open into (per #82366).

What Should Happen?

Clicking a file/preview link inside a detached session window should open that file in the preview pane of that same detached window, exactly as it does in the main window, and that window should keep focus. Link handling and the preview pane should be scoped per-window, like the session they belong to - no dead clicks, no silent routing to another window.

Environment

• Claude Code desktop app, Windows 11
• Claude Code version 2.1.72
• Reproduced by opening an existing session in a new window (Open in -> New window) and clicking a file link that works in the main window.

Additional Notes

I have screenshots of the working (main window) vs non-working (detached window) behavior but they contain private workspace content, so they are omitted here. I can provide redacted versions on request if they would help triage.