Installed builds already register a handler (MSI ProgIDs, the Linux
.desktop MimeType, the macOS Info.plist), but the portable .exe and the
AppImage register nothing, so they never appear in the OS "Open with"
list. Add a best-effort, idempotent runtime registration that runs
silently on a detached thread at startup:
* Windows — writes HKCU\Software\Classes\Applications\OpenCADStudio.exe
(open command + FriendlyAppName + SupportedTypes .dwg/.dxf), which is
what lists the exe in "Open with → Choose another app".
* Linux — writes a user-level .desktop pointing at the running binary
($APPIMAGE when set) and refreshes the desktop database. Skipped when
a system package already provides the desktop entry, so we never
shadow a distro install.
* macOS — no-op; .app bundles auto-register with LaunchServices.
Unlike the default-app prompt this changes no defaults and shows no UI;
it only makes the binary discoverable as a handler.
https://claude.ai/code/session_01DFVSKgViFaxEjZD2KsTdtt
On the first launch that hasn't answered it yet, the app shows a small
dialog offering to become the default handler for .dwg and .dxf files.
The choice is persisted (default_assoc_prompted) so the prompt never
reappears.
The platform plumbing lives in io/file_association.rs:
* Windows — opens the OS's own per-app default-programs dialog via
IApplicationAssociationRegistrationUI::LaunchAdvancedAssociationUI,
passing the "Open CAD Studio" RegisteredApplications name the MSI
registers. Modern Windows guards the actual default behind a
UserChoice hash, so this is the supported consent path.
* Linux — xdg-mime default against the installed .desktop file, whose
MimeType entries already cover image/vnd.dwg and image/vnd.dxf.
* macOS — LSSetDefaultRoleHandlerForContentType binds the DWG/DXF UTIs
declared in Info.plist to the app bundle id.
The work runs on a dedicated thread (the Windows dialog is modal) with
the result delivered back through a oneshot channel and surfaced in the
command line.
https://claude.ai/code/session_01DFVSKgViFaxEjZD2KsTdtt
