The desktop app's chat-completions stream relies on a raw browser
fetch from the Tauri webview to the FastAPI backend, so it is
subject to CORS. The default allowlist only contained
`tauri://localhost`, which is the production webview origin on
macOS, Linux, and iOS. On Windows and Android, Tauri 2 serves the
app from `http://tauri.localhost` (or `https://tauri.localhost`
when `windows.useHttpsScheme` is enabled), so the preflight for
`POST /v1/chat/completions` was rejected and the streaming fetch
threw `TypeError: Failed to fetch` before any byte was read.
Symptom users reported: in the Logs tab the request appears to
succeed up to "Request sent", followed immediately by
"Stream error: Failed to fetch" and "Response: 22 chars" -- which
is exactly the length of the synthesized fallback string
`Error: Failed to fetch` written by InputArea.tsx when streamChat
throws.
Add `http://tauri.localhost` and `https://tauri.localhost` to both
default origin lists (`ServerConfig.cors_origins` and the
`create_app` fallback), and add a regression test that drives a
real preflight against `/v1/chat/completions` for each of the
three Tauri origin schemes.
Browser model loading kept working because it is routed through
the Rust `tauriInvoke('fetch_models')` command, which is a
server-to-server HTTP call not subject to browser CORS -- only
streaming chat goes through the webview's fetch.
- BoundaryGuard degrades gracefully when Rust scanners unavailable
- BoundaryGuard tests use lightweight mock scanners (no Rust needed)
- Server-dependent tests use pytest.importorskip for starlette/fastapi
- Fix import ordering in test files
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
