In-app Browser preview reports "not enabled on this install" despite setting being ON

\preview_start\ on a URL-attach server config (\{"name": ..., "port": ..., "url": "http://localhost:<port>"}\) fails with:
\\\
"<name>" attaches to a URL, which needs the in-app Browser preview — it is not enabled on this install. Add a command ("runtimeExecutable"/"program") to start the server instead, which previews at http://localhost:<port>.
\\\

This config worked reliably for weeks (including across sleeps/reboots) prior to this session. Steps tried, none resolved it:

• Fully quit and restarted the desktop app — no change.
• Toggled the Browser Preview setting OFF → ON in Settings, then fully restarted the app — no change.
• Retried in bypass-permissions mode — no change.
• Rebooted the machine and updated to the latest macOS — no change.

The suggested workaround (switch to a command-mode config with \runtimeExecutable\) doesn't work either in this case, since the target server runs inside a podman container; podman's \gvproxy\ always owns the published port, so command mode instead fails with \"Port <port> is required by this server but is in use by 'gvproxy'"\ — there's no config that lets a podman-backed dev server attach either way.

Environment: macOS (just updated to latest), Claude desktop app, dev server running via podman/docker compose.