[banjerluke]

Human comments

On my Android 13 eInk tablet (Boox Note Max), PDF links would open a side panel browser but wouldn't display, I assume due to platform limitations. The ideal flow on that device is to download the PDF, which sends it right into the Notes app where I can review and/or annotate it. (Re-submission of #2689)

What was wrong

The file-opener system could select the built-in preview or a plugin viewer, but had no download action. Users whose browsers could not display PDFs lacked a persistent preference or one-off action to download them instead.

What changed

• Added Download as a built-in opener choice for .pdf files under Settings → File openers, preserving existing default opener behavior.
• Added one-off Download PDF and Open preview actions to thread file-link context menus, including long-press menus.
• Applied the saved preference to file-opening flows while allowing explicit preview actions to override it.
• Implemented downloads entirely in the app: fetch the existing file-content endpoint, create a browser blob URL, and supply the filename through the download link.
• Validated HTTP responses and showed an error toast instead of saving failed responses as PDFs.
• Explained unsupported file locations with a toast and allowed callers to fall back to preview.

This is an app-only change. It adds no server endpoint or contract changes, host-daemon protocol changes, or public Plugin SDK surface.

How you verified

• pnpm exec turbo run typecheck --filter=@bb/app
• pnpm exec turbo run test --filter=@bb/app -- file-download useThreadFileTabs FileOpenersSettingsSection plugin-slot-resolvers
• All 48 focused tests across four files passed.
• Coverage includes saved and one-off download selection, explicit preview overrides, workspace/host/thread-storage routing and filenames, failed HTTP responses, unsupported host targets, and unresolved workspace routing.
• git diff --check origin/main...HEAD passed.

AGENT GENERATED

[SawyerHood]

This is an automated message. We have closed this pull request because it has been open for more than two weeks.