Prusa firmware 6.5.7 improves filament changes and CoreXY calibration

Filament changes got less clunky across Prusa’s CORE One family when firmware 6.5.7 landed on June 18, 2026, and that is the part owners who print every day will feel first. Prusa framed the package as a stable release with targeted stability improvements and fixes, not a flashy feature drop, and the update spans the CORE One L, CORE One+, CORE One, MK4S, MK4, MK3.9S, MK3.9, MK3.5S and MK3.5.

The biggest practical change is improved filament change between different materials. For anyone switching between PLA, PETG, ASA or other materials during multi-part jobs, that is the kind of fix that cuts down on wasted time at the machine and makes the whole workflow feel less fussy. Prusa also added support for older xBuddy board versions, which broadens compatibility for machines in the field rather than limiting the update to the newest hardware.

The rest of the changelog is all about reliability in real-world use. Firmware 6.5.7 fixes input shaper calibration for CoreXY printers, a detail that matters when motion tuning has to stay tight on machines like the CORE One line. It also fixes a problem with loading custom Prusa Connect certificates, which is the sort of small but important networking issue that can get in the way of remote printing and monitored setups. Another fix addresses a crash that could happen when printing more than 1,024 objects, a corner case that batch-printing users and makers running dense plate layouts will notice immediately.

Prusa repeated the same 6.5.7 changelog across the Prusa Knowledge Base, the CORE One family downloads page, GitHub, and the Prusa3D Forum, reinforcing that this was the company’s stable release announcement for the platform. The CORE One product page picked up firmware 6.5.7 on June 19, 2026, and the broader downloads hub also listed PrusaSlicer 2.9.5. That hub pointed to an earlier 6.5.3 release for the Signature Oak, which “massively speed[ed] up MMU filament changes,” a useful reminder that Prusa has been pushing on filament-change performance as a recurring firmware priority rather than a one-off tweak.

For CORE One owners, that is the real story here: fewer interruptions when materials change, fewer calibration headaches on CoreXY hardware, and fewer surprises in connected or high-object-count jobs.