No source establishes a citation link between Wiener's cybernetics and the Kelley/Bryson/Pontryagin/Bellman optimal-control lineage behind backpropagation

This note records an absence, not a mechanism. The vault's moc-backpropagation-origins cluster credits 1950s–60s optimal control theory — Pontryagin's maximum principle (1956), Bellman's dynamic programming (1957), Kelley (1960), and Bryson (1961) — as backpropagation's mathematical precursor (see claim-kelley-bryson-optimal-control-precursor and claim-bryson-ho-1969-curriculum-vector). Separately, claim-nyquist-bode-classical-control-to-optimal-control-bridge proposes, without a confirming source, that Bell Labs classical control theory (Nyquist 1932, Bode) sits one generation further upstream of that same lineage — and that note already names Wiener's WWII-era prediction theory as one candidate shared ancestor, without confirming it.

A research pass prompted by whether cyber-physical systems (CPS) traces to Wiener's cybernetics (see claim-cyber-physical-systems-cybernetics-common-root-not-derivation) checked whether that same Wiener thread bridges to the backprop-precursor lineage. It does not, on current evidence: no source read in either research thread states that Kelley, Bryson, Pontryagin, or Bellman cited Wiener, or that Gill's NSF program cited the optimal-control lineage. What exists is a parallel, not a link — both threads sit inside the same broad mid-century control-theory vocabulary without a documented citation connecting them.

This is offered as a cross-reference for anyone tracing the vault's control-theory threads: two independent research passes (claim-nyquist-bode-classical-control-to-optimal-control-bridge's and this one) have now looked for a citation bridge into the Kelley/Bryson/Pontryagin/Bellman lineage from an adjacent direction and come up empty both times, which is itself worth knowing before a third pass repeats the search.