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Firmware 6.5.6 Removed Already  

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Ruebarb
(@ruebarb)
Estimable Member
Firmware 6.5.6 Removed Already

What the deal? The firmware was released only for a few hours and then taken down.

Core One L MMU3, MK3S

Posted : 03/06/2026 2:32 pm
Kachidoki
(@kachidoki)
Estimable Member
RE: Firmware 6.5.6 Removed Already
Posted by: @ruebarb

What the deal? The firmware was released only for a few hours and then taken down.

Arrghh, just updated the whole fleet few minutes ago...

Posted : 03/06/2026 2:34 pm
hyiger
(@hyiger)
Famed Member
RE: Firmware 6.5.6 Removed Already

Guess they found a last minute show-stopper bug. @kachidoki you should probably revert. 

Posted : 03/06/2026 3:07 pm
Ruebarb
(@ruebarb)
Estimable Member
Topic starter answered:
RE:

Glad Prusa pays attention to the forum

https://www.reddit.com/r/prusa3d/comments/1tvtw9d/prusa_buddy_fw_656_retracted/

https://www.reddit.com/r/prusa3d/comments/1tvsk49/dont_install_the_github_fw_for_mk4s_from_today/

Core One L MMU3, MK3S

Posted : 03/06/2026 4:53 pm
1 people liked
Kachidoki
(@kachidoki)
Estimable Member
RE: Firmware 6.5.6 Removed Already

It looks like the issue is specific to the MK4S. Mine starts up normally, so I’ll wait for the next version.

Version 6.4.2 was released at the same time for the XL. The release notes are brief, but I’ve noticed an improvement in the user interface. When you select tools to rearrange the filaments, the selected print head lights up. But I also found a bug right at the start of the first print, when switching to the left screen, the printer status overlaps the information.

Posted : 03/06/2026 5:27 pm
Kachidoki
(@kachidoki)
Estimable Member
RE: Firmware 6.5.6 Removed Already

The first hint from the dev team points to older xBuddy revisions.

Fortunately, since I’ve already sold my first MK4, my oldest remaining printer is an MK4S. Wait'n'see.

Posted : 05/06/2026 5:41 am
chmax
(@chmax)
Reputable Member
RE: Firmware 6.5.6 Removed Already

I wonder why Prusa people answers on reddit but never waste a second on their own forum...

Posted : 05/06/2026 12:36 pm
2 people liked
Eds_3D_Odyssey
(@eds_3d_odyssey)
Estimable Member
RE: Firmware 6.5.6 Removed Already

 

Posted by: @chmax

I wonder why Prusa people answers on reddit but never waste a second on their own forum...

Hopefully that changes when we get new forum software!!

https://www.printables.com/@Eds3dOdyssey
Posted : 05/06/2026 2:56 pm
Kachidoki
(@kachidoki)
Estimable Member
RE: Firmware 6.5.6 Removed Already

It has been a week since the firmware was removed. It looks like the bug requires more than a simple hotfix...

Posted : 10/06/2026 11:30 am
Ruebarb
(@ruebarb)
Estimable Member
Topic starter answered:
RE: Firmware 6.5.6 Removed Already

This is Prusa, nothing is done fast, even if it can be. Plus they were about to drop the HT firmware this month, they may just wait and do a 6.5.7 release.

Core One L MMU3, MK3S

Posted : 10/06/2026 12:29 pm
chmax
(@chmax)
Reputable Member
RE: Firmware 6.5.6 Removed Already

... and the INDX firmware, prusaslicer 3.0 and 2.9.6 final, ...

sw releases became quite slow and, to be honest, every fw release seem to have bad regressions for the non-core platforms, in itself consuming even more dev resources ...

there are bugs logged in the repo that have been sitting there ignored for months  (eg canceling an object makes a mess of the other objects on the plate), so don't expect any fast fix...

Posted by: @ruebarb

This is Prusa, nothing is done fast, even if it can be. Plus they were about to drop the HT firmware this month, they may just wait and do a 6.5.7 release.

 

Posted : 10/06/2026 1:35 pm
hyiger
(@hyiger)
Famed Member
RE: Firmware 6.5.6 Removed Already

 

Posted by: @chmax

sw releases became quite slow and, to be honest, every fw release seem to have bad regressions for the non-core platforms, in itself consuming even more dev resources ...

I'm just speculating but wonder if they are not allowed to use a LLM like Claude in-house? At my work it's been a game-changer for finding bugs. We still do human inspection of the code that produced. It can't be any worse than what we are seeing now? Subjectively, each firmware update seems to provide less in terms of enhancements and introduces yet more issues. 

Posted : 10/06/2026 1:43 pm
Ruebarb
(@ruebarb)
Estimable Member
Topic starter answered:
RE: Firmware 6.5.6 Removed Already

For a company that is proud it produces everything in house, it often feels like it has all been subbed out to China to build and India to program it.

Posted by: @hyiger

 

Posted by: @chmax

sw releases became quite slow and, to be honest, every fw release seem to have bad regressions for the non-core platforms, in itself consuming even more dev resources ...

I'm just speculating but wonder if they are not allowed to use a LLM like Claude in-house? At my work it's been a game-changer for finding bugs. We still do human inspection of the code that produced. It can't be any worse than what we are seeing now? Subjectively, each firmware update seems to provide less in terms of enhancements and introduces yet more issues. 

 

Core One L MMU3, MK3S

Posted : 10/06/2026 1:48 pm
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