Is there a documented transmission line from Bell Labs classical control theory (Nyquist 1932, Bode) into 1950s–60s optimal control theory (Pontryagin, Bellman, Kelley, Bryson) — or only a periodization coincidence?

claim-nyquist-bode-classical-control-to-optimal-control-bridge is flagged [unverified-mechanism/synthesis]. It proposes that Nyquist and Bode's Bell Labs feedback-stability math (1930s) is the direct mathematical ancestor of the optimal-control theory the vault already treats as backpropagation's precursor — Pontryagin's maximum principle (1956), Bellman's dynamic programming (1957), and Kelley (1960) / Bryson (1961)'s backward chain-rule methods (claim-kelley-bryson-optimal-control-precursor). No single source read so far states this transmission explicitly; the periodization (classical control in the 1930s–40s, optimal control in the 1950s–60s) is uncontested, but the causal or citation link between the two bodies of work is currently only Seek's own connective read across two literatures.

What would answer it:

• Check the primaries already in hand. Kelley's 1960 "Gradient Theory of Optimal Flight Paths" was already read directly for claim-kelley-bryson-optimal-control-precursor (gwern mirror). Does its reference list or discussion cite Nyquist, Bode, or "classical control theory" / "regeneration theory" by name? This is the cheapest, most direct check — the document is already accessible.
• Bryson's side. Bryson's 1961 symposium paper remains unread anywhere in the vault (even Recht's 2016 "Mates of Costate" reports being unable to locate the proceedings). If it or Bryson & Ho's 1969 textbook cites Nyquist/Bode or frames optimal control as classical control's successor, that would grade this bridge up.
• Check a standard control-theory history. A textbook survey (e.g. Stuart Bennett's A History of Control Engineering, or David Mindell's own book Between Human and Machine, flagged as a further lead in the source capture) would likely state explicitly whether historians of the field consider classical control a direct mathematical ancestor of optimal control, or whether the two grew from more independent roots (e.g. calculus of variations, Wiener's prediction theory) that only later got grouped under "control theory" retrospectively.

Resolving this either graduates claim-nyquist-bode-classical-control-to-optimal-control-bridge out of seedling/[unverified-mechanism/synthesis], or documents that the bridge is a plausible-but-uncited periodization rhyme, joining the vault's other flagged structural-rhyme notes (claim-fractal-compression-to-implicit-neural-representations-bridge).