\section{Background and Motivation}
\label{sec:background}

\subsection{One work world, several fact cuts}

We use \emph{real-world agent work} to mean work in which agents help users
manage concrete tasks rather than only produce isolated model outputs. Such
work may involve local state, repositories, remote terminals, GUI and TUI
controls, model calls, releases, documents, and human decisions. The product
problem is not only how to run an agent. It is how to keep the work legible
when no session or interface contains its complete identity.

Return to the cross-session task. The repository may prove which files changed.
The remote runtime may contain later execution facts. The local GUI may have
accepted only an earlier remote range. A build service may know that one
artifact failed after the first session ended. The transcript may explain an
intention without proving that the intended action occurred. None of these
sources is automatically the whole world, and combining their timestamps does
not remove their different authority, freshness, and consequence boundaries.

A useful view therefore needs more than recorded facts. It needs to say which
facts it accepted, what it omitted, how it ordered concurrent material, and for
which participant and action context the projection is being shown. Otherwise
two participants can appear to disagree about reality when they actually hold
different cuts or apply different policies.

\subsection{The global-clock temptation}

Distributed systems theory has long shown that causal order is not equivalent
to physical time. Lamport's happened-before relation separates causality from
wall-clock order \cite{lamport1978time}; vector-clock style systems make
concurrency explicit \cite{mattern1989virtual}; and distributed snapshots show
that a useful global state is a constructed consistent cut rather than a
simultaneous physical observation \cite{chandy1985snapshots}.

Yet product surfaces often sort mixed-source facts by timestamp and render one
history. That may be sufficient for casual logs. It is not sufficient when a
human or agent must audit a claim, recover after interruption, challenge an
ordering assumption, or decide what action is safe. A deterministic global
sequence can still be misleading if the product does not declare which facts
entered it and which policy resolved concurrency.

Observer declaration is not a replacement for clocks, consensus, tracing, or
replication. It is a product-level obligation above them. Even a centrally
sequenced view has an accepted input boundary and a consumer for whom the view
has consequences.

\subsection{The KFD-4 obligation}

The Foundation Triad can be summarized as:

\begin{quote}
KFD-1: facts must not drift.\\
KFD-2: trust must start from facts.\\
KFD-3: cooperation must start from trusted value.
\end{quote}

KFD-4 applies those responsibilities to perspective-bearing surfaces:

\begin{quote}
KFD-4: timelines must declare their observer.
\end{quote}

The word \emph{observer} does not mean that truth is subjective. It marks the
position from which a bounded fact world becomes a view. A declaration must
preserve source identity and known causality, expose the evidence boundary for
trust, and make the view's action relevance and limitations inspectable to the
participant expected to use it. Different observers may legitimately receive
different projections; they may not silently invent facts or invert known
causal relations.

\subsection{The observer is not immortal}

Once a view has an observer, long-lived work exposes another boundary. The
component producing the view may restart, a frontend may upgrade, a process
identifier may be reused, or a new agent may attach to surviving work. Reusing
the same name does not prove that the successor accepted the same fact cut,
reconstructed the same projection, or applies compatible semantics.

Failure-detector theory separates suspicions about process failure from
stronger guarantees \cite{chandra1996failure}. At the product layer, liveness
is likewise weaker than continuity. A replacement may continue a logical
perspective only after it identifies the authority it accepted, rejects stale
claims, rebuilds or verifies derived state, and declares the semantics under
which it presents the result. Otherwise the product should expose a
discontinuity or degraded view.

This incarnation problem refines KFD-4 after the basic perspective obligation
is established. It must not obscure the simpler first claim: before asking
whether an observer continued, the system must say which observer's view it is.
