Which conditions trigger the creation of .save files during a nano crash?

GNU nano utilizes a temporary file system to manage unsaved changes, allowing users to attempt data restoration via the -R or --recover flag after an unexpected session termination.

While the editor implements emergency backup mechanisms, buffer management is primarily memory-resident. This creates uncertainty regarding the exact triggers that force a write to a .save file versus scenarios where data remains exclusively in volatile memory until a manual save is initiated.

Specifically, it is unclear if certain termination signals (such as SIGKILL versus SIGTERM) or specific system states consistently guarantee the generation of a recovery file.

• Does nano consistently generate a .save file during a SIGKILL event?
• What specific internal buffer thresholds or timers trigger an automatic emergency save to disk?