Desktop app: SendUserFile file cards (PDF/HTML) always force download — display:'render' ignored, no side-panel preview

Environment

• Claude desktop app (Claude Code Desktop): 1.32885.1
• OS: macOS (Darwin 25.5.0)
• Model/session: Claude Code session inside the desktop app

Description

File cards delivered to the user via SendUserFile always open the macOS "Save As" download dialog when clicked — they never render in the side panel, regardless of file type or the display parameter.

Tested in one session today:

1. PDF sent with display: "render" → click opens download dialog (no preview)
2. PDF sent with display omitted → same
3. Self-contained HTML file (images inlined as data URIs) sent with display: "render" → same, download dialog only
4. ASCII-only filenames vs CJK filenames → no difference

Expected

Per the tool contract, display: "render" should open the file inline in the side panel ("for HTML, SVG, Mermaid, images, PDFs — anything the user wants to look at now").

Actual

Clicking any file card triggers a download dialog. There appears to be no user-facing setting to enable side-panel preview (checked ~/.claude/settings.json keys).

Why it matters

The natural review loop for document deliverables (contracts, client letters, reports) is: preview in the side panel → request edits → iterate → only download the final version. With every click forcing a download, users accumulate half-finished files in their Downloads folder and lose the fast review loop. Current workaround is re-rendering documents as inline chat widgets, which loses fidelity and bloats the conversation.

Request

• Make display: "render" actually render PDFs/HTML/images in the side panel on the desktop app, or
• Provide a per-card "Preview" affordance next to "Download".