Bits of .NET

🖌️ The Undo That Stopped Working Way Earlier Than Expected

The History panel only keeps a limited number of undo states by default, and once an editing session crosses that count, the oldest states simply fall off the list to make room for new ones with no warning that it is happening. A long, detailed session full of small brush strokes and repeated selection adjustments can burn through the default limit far faster than expected, and the moment you need to undo back past where the list now starts, there is nothing left to undo to – the earliest available state is just wherever the sliding window currently begins, not the actual start of your session.

🔎 The Problem

Setup: a long retouching session - dozens of small brush strokes,
repeated selection tweaks, several filter re-applications - with the
History panel left at its default state count.

Symptom: scrolling to the top of the History panel does not reach the
original opened file anymore - the earliest entry is already several
steps into the session, and the states before it are simply gone,
with nothing in the panel indicating any were ever discarded.

The default state count lives in Preferences > Performance, and
raising it there (several hundred, on a machine with enough memory)
keeps far more of a long session's history available - but a named
Snapshot, taken at a meaningful checkpoint, survives regardless of how
many more states follow it, which a raised limit alone does not
guarantee for a session long enough to exceed even the new number.

✅ Fix: Raise the State Limit and Use Snapshots at Real Checkpoints

• Raise the History States value in Preferences, under the Performance tab, to a higher number – several hundred is reasonable on a machine with enough memory – rather than leaving it at the conservative default meant for older, more memory-constrained machines.
• Use named Snapshots, taken at meaningful checkpoints during a long editing session – unlike a regular history state, a snapshot does not get silently evicted as you keep working, so it survives as a reliable fallback no matter how many more edits follow it.
• Save incremental versions of the file at major milestones rather than relying on History states alone as the only safety net – History is explicitly meant as a within-session convenience, not a durable undo log, and it resets completely the moment the file is closed anyway.

⚠️ Why This Is Easy to Miss

• Nothing in the History panel visually signals that you are approaching the limit – the panel just quietly stops showing the earliest states as new ones get added, with no moment where Photoshop tells you that you are about to lose the ability to undo back to the start.
• A shorter editing session, or one with fewer total discrete actions, never comes close to the default limit at all, so the problem is specific to long, detailed sessions – exactly the kind of work where losing the ability to undo back to an earlier point is most costly.