{Li$\lower.1ex\hbox{\eightsl b}\over\hbox{\acrosl \rlap{\phantom{T}}t}$erate $\raise.5ex\hbox{\acro{\TeX}}\over{\lower.64ex\hbox{\acro{C}}}$ Top part:~\texttt{JSBox}} {Doug McKenna} {A work in progress, \texttt{JSBox} is a self-contained library\Dash written in portable C\Dash that instantiates sandbox-able, \TeX-language interpreters within the memory space of any C, Objective-C, or \Cplusplus\ 32- or 64-bit client program. Built and documented anew, \texttt{JSBox} is faithful to the \TeX\ language's primitives, syntax, typesetting algorithms, measurements, data structures, and speed. At the same time, it fixes\Dash in an upwardly compatible manner\Dash a variety of important problems with or lacun\ae\ in the current \TeX\ engine's implementation. These include integral support for 21-bit Unicode, namespaces, OpenType font tables and metrics, job-specific 8-bit to 21-bit Unicode mapping, run-time settable compatibility levels, full 32-bit fixed-point math, and more. Especially pertinent to interactive applications\Dash such as an eBook reader\Dash is that all of a document's pages can optionally be kept as \TeX\ data structures in memory after a job is done, with direct random access of any requested page exported to the client program's screen without file \acro{I/O} or \DVI\ or \PDF\ conversion if unneeded. Tracing (including recursive expansion, re-tracing interrupted commands, alignments, math, etc.)\ and all error messages have been significantly improved over what \TeX\ does. The author will demo what \texttt{JSBox} can do now, and discuss what it could do in the future.}