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\section{Physics Runtime Task List (Phase 1 Record)}

This document records the task list that guided Phase 1 physics runtime development.
It served as the primary instruction sheet for both human and AI contributors. Tasks
are presented here as a historical record; completion status is noted where known.

\subsection{Agent Working Rules}

Contributors worked on one checkbox task per session, presented all changes as diffs
before any commit, and halted immediately on test failure with a precise failure report.
Architecture changes, dependency introductions, and non-C99 language conversions were
explicitly prohibited. All new behaviour was required to be deterministic, explicit, and
transparent, without background threads or undocumented async I/O.

\subsection{Task Areas}

\paragraph{Immediate stability tasks.}
Clarifying comments on heat, decay, window, and prefetch code paths; null-safety audit
of \texttt{prev\_word}, \texttt{transition\_metrics}, and dictionary entries; verification
that rolling window, pipeline metrics, and execution heat paths cannot dereference NULL;
compile-time guards around physics features; and ensuring DoE mode writes exactly one
CSV line to \texttt{stdout}.

\paragraph{VM signal and wire identification.}
Creation of a \texttt{PHYSICS\_SIGNALS.md} document cataloguing every potential signal
point (execution, temporal, and DoE) cross-referenced to the source file and function
that would emit it, classified as MUST-HAVE, HIGH-VALUE, or FUTURE.

\paragraph{VM event bus foundation.}
Definition of a \texttt{vm\_event\_type\_t} enum, a \texttt{vm\_event\_t} struct with a
tagged-union payload, a single-callback \texttt{vm\_publish\_event()} implementation, and
a registration API. No full wiring; proof-of-concept only.

\paragraph{Adaptive heartbeat.}
Measurement foundations (pressure metrics struct and
\texttt{physics\_compute\_pressure()}), followed by rate-control logic clamped between
configurable minimum and maximum tick intervals, disabled by default to preserve
deterministic test behaviour.

\paragraph{Feedback loops standardisation (FL1--FL4).}
Inline labelling and documentation of the four core loops: heat accumulation and decay
(FL1), hotwords cache promotion (FL2), inference to decay slope (FL3), and inference
to rolling window tuning and prefetch ROI (FL4).

\paragraph{DoE subsystem overhaul.}
Clean CLI handling, a typed \texttt{DoeMetrics} struct with named fields, stable CSV
field order, \texttt{metrics\_from\_vm()} extractor, and header and row write functions.

\paragraph{Metrics and logging hygiene.}
Standardised log prefixes, single-line CSV output in DoE mode, separation of logs to
stderr and CSV to stdout, and an option to suppress non-error logs during DoE runs.

\paragraph{Testing and documentation.}
Unit tests for event dispatch and pressure computation; regression tests for DoE mode;
\texttt{PHYSICS\_RUNTIME.md}, \texttt{PHYSICS\_SIGNALS.md}, and \texttt{PUBSUB\_DESIGN.md}
documentation deliverables.

%% TODO(bob): record which tasks were completed before this file was archived.