If you paint a fur density map in Texture Paint, switch to Particle Edit to groom the strands, then hit `Ctrl+Z`, Blender 4.5.0 through 4.5.12 can corrupt the .blend file on that undo step. Blender 4.5.13 LTS, released August 25, 2026, fixes it. If you're on the 4.5 LTS branch and your workflow touches both modes on the same asset, update before your next grooming session.
The bug is tracked as issue #161532: "Switching from texture paint to particle edit mode by undo corrupts .blend file." The fix landed as pull request !161542, "Restore Particle Edit mode correctly during undo," merged into Blender's main branch on July 21, 2026, then backported into the 4.5 LTS maintenance branch 35 days later. 4.5.13 also patches a second, unrelated bug — the Extensions tab failing to load behind an SSL handshake problem — and pulls forward several core library updates for the branch.
Who actually hits this
Particle Edit is the mode you use to comb, clump, and cut a particle hair system by hand once it's generated — it's how creature fur, feathers, and hand-placed grass scatter get their final shape, as opposed to leaving everything to the raw simulation. Texture Paint into Particle Edit isn't an edge case for anyone building that kind of asset. It's the standard loop: paint a density or length map on the mesh in Texture Paint, jump to Particle Edit to groom the resulting hair system, check the result, undo a stroke that went wrong, repeat. A wolf pelt, a griffin's wing feathers, a hillside of grass cards — all of it runs through that exact mode switch dozens of times a session.
BitSoul's Dire Wolf is a working example of the asset type this sits under: fur groomed with particle hair rather than baked as static geometry, which is exactly the paint-then-groom loop the bug lives inside. If you're building something similar and undoing across that mode boundary on 4.5.12 or earlier, the file can come back corrupted — in the reports behind #161532, the .blend either fails to reopen cleanly or reloads with the particle system in a state that no longer matches the paint layers underneath it.
The fix, in numbers
| Item | Before 4.5.13 | In 4.5.13 (Aug 25, 2026) |
|---|---|---|
| Texture Paint to Particle Edit undo (#161532) | Corrupts the .blend on undo | Fixed via PR !161542 |
| Extensions tab | Fails to load (SSL problem) | Fixed |
| Core dependencies | Stale for the 4.5 branch | Updated |
| Time from fix merge to LTS backport | — | 35 days (Jul 21 to Aug 25) |
That 35-day gap is normal for how Blender ships LTS fixes: they land on main first, soak there for a few weeks, then get cherry-picked into the maintenance branch once they've proven stable. If your studio tracks main instead of 4.5 LTS, you've had this fix since late July. If you're pinned to 4.5 LTS specifically — which most production pipelines are, because that's the whole point of an LTS branch — August 25 is when it reached you.
If you can't update today
Studios pin DCC versions mid-project for good reason, so dropping everything to update isn't always realistic. Until you're on 4.5.13:
- Save (`Ctrl+S`, or a numbered incremental save) before switching from Texture Paint into Particle Edit on any asset with a hair or particle system, not after.
- Avoid chaining undo across the mode switch itself. Undo your paint strokes while still in Texture Paint, and undo your grooming while still in Particle Edit, rather than backing out through both modes in one undo run.
- If a file does come back corrupted, check your last incremental save before assuming the grooming pass is gone. The corruption reported in #161532 hits the live undo stack in that session, not necessarily every prior save on disk.
None of this replaces updating. It's a way to keep working on 4.5.12 for the rest of the week without losing a session's worth of grooming.
Where this fits with everything else that changed
The Extensions tab fix matters to the same crowd for a different reason: it's how you install and update glTF/GLB exporter add-ons, rigging utilities, and third-party particle-hair tools in the first place. If your Extensions tab has been blank or hanging on load over the past few weeks, that was the SSL handshake problem, not your network or a firewall rule. It clears up in 4.5.13 alongside the undo fix.
If you're also seeing export weirdness on top of this — shape keys vanishing on GLB export, or rigs coming out squashed — those are separate bugs in Blender's glTF exporter and in glTF's own 4-bone weight limit, not anything 4.5.13 touches. Worth ruling out separately rather than assuming one update fixes both — a corrupted grooming session and a broken export are two different failure points in the same pipeline.
This is also the second DCC maintenance release this month built around silent corruption rather than missing features. Marmoset Toolbag 5.03 shipped in mid-August fixing a UV bug that corrupted baked textures. If your pipeline runs Blender for grooming and Marmoset for baking, both tools had silent-corruption bugs patched within two weeks of each other — worth checking both version numbers in the same sitting rather than one at a time.
Check `Help > About Blender` for your build number before your next grooming session. If it reads 4.5.12 or earlier and the project touches particle hair or fur, update first, groom second.
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*This post is part of the Ultimate Guide to Free 3D Game Assets — BitSoul's complete reference for formats, texturing, rigging, optimization, and engine integration.*