asterisk users - Oct 2008 - Asterisk 1.6 pbx_lua not creating any contexts

Howdy, all. I'm trying to use pbx_lua as included in Asterisk 1.6 --
but while it correctly reports an error on startup (but not reload!)
if extensions.lua does not exist, it doesn't appear to actually create
any contexts.

I'm testing in a very minimal configuration with autoload turned off;
"module show" shows only chan_sip, pbx_lua, and app_dial.

"dialplan show" calls only 'app_dial_gosub_virtual_context',
created
by app_dial, and 'parkedcalls', created by 'features'; no
contexts
defined in extensions.lua are visible. This is true even when using
verbatim the extensions.lua.sample included in SVN (trunk as of
r144523). pbx_config, if enabled, works normally.

Where should I start in diagnosing this issue?

Thanks!

To follow up --

pbx_lua from trunk works as advertised when backported to 1.6.

pbx_lua from asterisk 1.6 seems hopelessly broken, and I've given up
on trying to persuade it to work.