Concerns: pushword/admin-block-editor, pushword/core
The generated Dockerfile rebuilds FrankenPHP with Go 1.26.9, golang.org/x/net 0.60.0 and golang.org/x/crypto 0.57.0. For sites using the Docker skeleton: regenerate it with pw:docker:init --force, then rebuild the image. If you customized the Dockerfile, apply those builder settings manually instead of overwriting it.
The heading tool now offers the levels listed under tools.header.config.levels in the editor widget, H2 to H6 by default; a heading keeps its own level even when the list leaves it out. For sites overriding the editorjs_config block of editorjs_widget.html.twig: set levels: [2, 3, 4, 5, 6] there to keep offering H5 and H6.
The block editor saved a block with both an anchor and a class (or an alignment) as {#anchor.class}, which renders as id="anchor.class" and no class; it now writes {#anchor .class}. Editing such a block rewrites it. For sites whose pages hold such lines: open and save those pages in the block editor, or replace {#anchor.class} by {#anchor .class} in their content.