Undo history retention limits

Limit stored snapshots across all branches while preserving the current entry.

Use

User Preferences > General > Undo history has Maximum entries (all branches). Values are limited to 0-100000; 0 selects the default of 20 rather than disabling undo. The limit counts snapshots across branches, not just the current path. Changing it can prune history immediately.

Caveats

The current entry is always kept, even if it alone exceeds the available budget. History reports pruned snapshots and an oversized current snapshot. Old branches are not guaranteed to remain indefinitely. Show history memory tally in Debug preferences helps inspect retention cost; it does not change the drawing. See [ FPS and history-memory diagnostics ] and [ Save or clear embedded undo history ].