Rider fails to start after upgrade — Toolbox version fallback and settings persistence

Rider upgrades can fail during installation or first startup. The goal is to understand the documented recovery behavior when a new build does not start, particularly how version availability and user data persistence are handled.

Installations managed by JetBrains Toolbox App are reported to retain previous builds, while user settings, caches and plugin data are stored separately from application binaries. Standalone installer behavior may differ, and update mechanisms have changed across major releases. There is no consistently documented automatic rollback to a prior build on startup failure, and recovery is described as user-initiated and installation-method dependent.

What is the documented startup behavior when Rider fails to start after an upgrade in a Toolbox-managed installation? Is manual selection of a previous build required, or is any automatic fallback defined? Are settings and caches guaranteed to persist across a failed upgrade for both Toolbox-managed and standalone installations?