papers/kai/sections/01-introduction.tex

\section{Introduction}
\label{sec:intro}

Agents ask the same small questions thousands of times per session: which
context the next turn sees, which tool fits, whether a command may
run~\cite{jevnote}. A generative model answers in prose with no probability to
threshold; a fixed rule sees only what its author foresaw. A \emph{typed
decision} sits between: the caller states a question, lists the admissible
answers and passes the evidence, and the model returns a distribution over
exactly those answers, which can be type-checked, thresholded, logged and
replayed.

Three planes: the \emph{generative} writes (Zen), the \emph{decision} answers
typed questions over evidence (Kai), and the \emph{policy} is deterministic,
written by people, and final. A decision is a program, not a prompt
(Figure~\ref{fig:program}): Zen reasons inside it, Kai judges, code and solvers
compute, policy and people hold authority, and each run leaves a package.

\input{figures/program}

Two decision models exist to compare against, and both are baselines, never
Kai revisions. Laya~\cite{laya} is a family of open encoder checkpoints that
pack the question, every option and the state into one sequence; TypeSafe's
Jev~\cite{typesafejev} is a hosted model behind OpenRouter's Decisions
API~\cite{openrouterdecisions}. Status tags: \meas{} run by us, with the kept
artifact named; \reported{} published by others; \shipped{} on the main branch
of \texttt{hanzoai/decision} at the revision on the title page; \proposed{}
designed, not built.

\paragraph{Contributions.}
\begin{enumerate}[leftmargin=1.5em]
  \item \textbf{One model}: an evidence record for any modality with its
    sensor metadata, adapters into one encoder's width, and evidence, questions
    and options each encoded once per session; one checkpoint line trained in
    stages
    (Section~\ref{sec:model}).
  \item \textbf{Factorized choice}: options encoded alone and scored against
    shared evidence by two cross-attention blocks, a law per type, and
    retrieval that keeps the mass it cuts, so option count, order and question
    count are not bounded by one sequence (Section~\ref{sec:factor}).
  \item \textbf{Typed-variable diffusion}: a program's questions as masked
    slots decoded jointly over the program graph, refined in waves bounded by
    its depth and projected exactly onto its rules (Section~\ref{sec:diffusion}).
  \item \textbf{A training system} in pure Rust: local SGD with an outer
    Nesterov step across Metal, CUDA and ROCm machines, bf16 deltas with error
    feedback, bit-identical resume, token-budgeted batches under a memory
    floor, license classes and a contamination barrier
    (Section~\ref{sec:training}).
  \item \textbf{What went wrong}: stage A's encoder stopped relating two texts;
    the measurements, the ablations that locate the cause, and the fix; how
    much of the typed-decisions test set Laya's checkpoint had seen in near
    form, and that it did not help it; and a score head that lost thirty
    points to a softmax over level texts on the same encoder and data
    (Section~\ref{sec:findings}).
  \item \textbf{Policy precedence} as a lattice join, with a proof that
    enforcing a model only adds friction, and \textbf{programs and packages}
    that replay, diff, refresh and say what flips a decision, with SysML~v2
    import and an engineering knowledge graph
    (Sections~\ref{sec:authority} and~\ref{sec:programs}).
  \item \textbf{Benchmarks} of accuracy on a frozen harness, of capabilities
    the baselines lack by construction, and of speed, each table written by
    the command that measures it (Section~\ref{sec:evaluation}).
\end{enumerate}

\paragraph{What is claimed.}
The baselines' structural limits are measured: Laya rejects every question of
1{,}000 or more options and Jev every question over 255; answering five
dependent questions independently, Laya breaks one of the program's rules in
64\% of states and Jev in 25\%; reordering 16 options changes Laya's top
answer on 25.5\% of questions \meas{} (\texttt{hanzoai/benchmarks}
\texttt{4e57fb2}). The final checkpoint's numbers enter only through the
tables of Section~\ref{sec:evaluation}; no sentence states them, and the first stage-A run's numbers appear
only where Section~\ref{sec:findings} explains what went wrong. Kai trains on the
train splits of the harness's sources behind a barrier against its test
states, so a lead on a suite whose baseline never saw its source is
in-distribution for Kai, and Section~\ref{sec:limits} says what that does not
show.