Clicking a local .html path in chat opens the File/source viewer instead of rendering in the Browser pane

Summary

Clicking a local .html file path in chat opens the file in the File/source viewer (syntax-highlighted raw markup) instead of rendering it in the Browser pane.

The desktop docs state: "Click an HTML, PDF, image, or video path in the chat to open it there" — referring to the Browser pane, which renders. Rendering is what actually happens for the same file through every other entry point (see below), so the renderer works; only the click routing appears to be wrong.

Environment

| | |
|---|---|
| App | Claude desktop 1.24012.9 (Code tab) |
| OS | macOS (Darwin 25.5) |
| Files | self-contained static HTML, no external assets, located outside the session's project folder (a synced iCloud Drive folder) |

Steps to reproduce

1. Have a self-contained .html file outside the current session's project folder.
2. Ask the assistant to reference it, so a file path appears as a link in chat.
3. Click the link.

Expected: the page opens rendered in the Browser pane.
Actual: the File viewer opens showing raw HTML source.

Same file, other entry points — all render correctly

• Pasting the identical path into the Browser pane's address bar → renders.
• preview_start / navigate via the browser MCP tools → renders (verified by screenshot).
• Opening the file in Safari → renders.

Regression window

The click behaviour changed mid-session on 2026-07-31, at roughly 20:00 local time. Clicked links had rendered as pages throughout that day and for weeks prior.

Nothing changed locally in that window:

• No app update — the app bundle and main binary are dated 24 July, a week earlier.
• No app restart — the running app processes had uptimes of 4 and 30 days, spanning the behaviour change.
• Not the link format — relative, absolute, and file:// forms were each tested and all now behave identically (source viewer). Before the change, those same formats rendered.
• Not file content — files that rendered earlier in the day now open as source, unmodified.

Secondary observation

When a file is opened in the Browser pane by the working methods above, it renders as a static snapshot: <a href="file://..."> links inside that page do not navigate when clicked (verified both by coordinate click and by clicking the resolved element reference). This makes a local HTML index/gallery page non-navigable inside the pane, though it works normally in an external browser.

Impact

Local HTML files are a primary way of reviewing generated diagrams, dashboards, and reports without leaving the app. With clicks routing to source, every such review requires either an external browser or manually copying the path into the pane's address bar.