[Bug]: Reveal in File Explorer does not reveal chat-linked files on Windows (desktop 0.0.40)

[Bug]: Reveal in File Explorer does not reveal chat-linked files on Windows (desktop 0.0.40)

Area

apps/desktop

Description

The Reveal in File Explorer action is present in the context menu for a local file link in a chat response, but selecting it does not reveal the file as expected in the Windows desktop app.

This is a report of the desktop UI failure. The cause has not been isolated, and the native context-menu interaction has not been independently reproduced during report preparation.

Steps to reproduce

1. Open T3 Code Alpha 0.0.40 on Windows.
2. Open a conversation containing a local file link in an assistant response.
3. Right-click the file link.
4. Select Reveal in File Explorer.

These describe the reported interaction, not a verified minimal reproduction. The exact failing path and whether its link contains a line-number suffix have not yet been captured.

Expected behavior

Windows File Explorer opens the containing folder and selects the linked file. If the operation fails, the app shows an actionable error.

Actual behavior

The action does not reveal the linked file as expected. Whether Explorer does not open at all, opens a different location, or an error toast appears has not yet been confirmed.

Impact

The shortcut for locating a chat-linked file outside the app is unusable in the reported case. Frequency and affected path patterns are not yet established.

Version and environment

• T3 Code (Alpha), installed Windows desktop executable: file version 0.0.40, product version 0.0.40.0.
• Windows 11 Home, 25H2, 64-bit, OS build 26200.9445. Verified from the running system rather than the legacy registry product-name string.
• Report date: 2026-09-14.
• A native Windows T3 desktop process is running. The selected conversation's backend location has not been confirmed.

Logs and investigation notes

The local server.trace.ndjson* logs contain the following reveal-related spans on the report date. This is a summary of the logged fields, with durations rounded:

UTC time                 Span                                 Duration   Result
2026-09-14 18:47:21.487   resolveFileManagerRevealLaunch         1.192 ms  Success
2026-09-14 18:47:21.488   externalLauncher.launchEditorProcess 332.501 ms Success
2026-09-14 18:47:21.489   externalLauncher.launchAndUnref      331.934 ms Success

These spans share trace ID 20381c8ca826ea85de0c3b34cbf89c4b. The selected spans contain no target path or helper exit status. They have not been conclusively matched to the failing click, and Success does not establish that Explorer opened or selected the file.

In the v0.0.40 launcher source, launchAndUnref spawns and unreferences the helper without checking its exit status. The Windows reveal helper uses PowerShell to launch Explorer. These are investigation starting points, not a confirmed cause of this report.

Related: #11172 covers Windows reveal error reporting and explicitly says the original failure to open Explorer remained unexplained. Its linked PR #11173 was closed without merging. This report concerns the observed desktop action failure; it does not assume that the error-reporting proposal fixes it.

Screenshot context

The supplied screenshot shows the file-link context menu with Open in VS Code, Reveal in File Explorer, Copy relative path, and Copy full path. It confirms the action is available, but does not show the result after clicking. The image is not attached to this issue because an authenticated browser upload was unavailable during filing.

Workaround

No workaround has been verified. Copying the full path and navigating to its containing folder manually is a possible temporary alternative.

Reproduce the action on Windows, then inspect apps/server/src/process/externalLauncher.ts around the Windows reveal helper at line 588 and launchAndUnref at line 685. Trace the linked-file path and helper result, and verify that Reveal in File Explorer selects the file or shows an actionable error.