Hi Hans, When running in \normalizelinemode=0, the \parinitleftskip and \parinitrightskip nodes are either nonexistant or invisible from Lua, causing tex.linebreak to not work correctly. This sample file: \enabledirectives[system.callbacks.permitoverloads] \normalizelinemode=0 \directlua{ callback.register("pre_linebreak_filter", function(head) tex.preparelinebreak(head) local list, info = tex.linebreak(head) print(info) return head end) } \starttext \input knuth \stoptext Produces this output: luatex warning > linebreak: list seems already prepared luatex warning > linebreak: [ leftinit | rightinit | leftfill | rigthfill ] expected nil Thanks, -- Max