Hi Luigi,

forget my last post. I was in a hurry last week and put a

  \def\autoinsertnextspace{}

in my document just to get it compiling on context 2009.11.24. If I remove
that, it stops working with "texexec --lua" (as well as just "context") with
the same undefined control sequence error. It still works with just "texexec"
(e.g., with MkII).

So, it works for me with 2009.10.28, and gives errors with 2009.11.24. There
is no version where it silently fails, that was my own fault :-)

Actually, it does in fact seem the macro has completely disappeared. With the
old version:

  /usr/share/texmf/tex/context/base$ grep def.autoinsertnextspace *
  spac-gen.mkii:\def\autoinsertnextspace{\futurelet\nexttoken\doautoinsertnextspace}
  spac-hor.mkiv:\def\autoinsertnextspace{\futurelet\nexttoken\doautoinsertnextspace}

With the new version:

  /usr/share/texmf/tex/context/base$ grep def.autoinsertnextspace *
  spac-gen.mkii:\def\autoinsertnextspace{\futurelet\nexttoken\doautoinsertnextspace}

The comment in the old version does say:

  %D This is a dangerous feature because it makes the \TEX\ source
  %D less portable, i.e. any parser now needs to apply exactly the
  %D same algorithm when it wants to interpret the source. We
  %D strongly recommend not to mention this feature in manuals! It's
  %D provided for users who are hooked to such a mechanism.

So perhaps this is removed intentionally? Perhaps Hans can comment?

Gr.

Matthijs