Sahal's identity names the exact condition under which the EUV mirror moat must be calendar-time tacit knowledge, not a production-volume learning curve

The bridge between the two seed notes is real, but not because they're "about the same thing." Sahal's identity states the precondition under which Wright's Law (cost falls with cumulative production) and Moore's Law (cost falls with calendar time) become the same curve: "the combination of exponentially increasing cumulative production and exponentially decreasing costs gives Wright's law" (Lafond et al. 2017, arXiv:1703.05979, quoting Sahal 1979). That precondition is a testable fact about a technology's production history — and EUV lithography fails it badly.

ASML's own account: "That same year we established our existing partnership with lens manufacturer Carl Zeiss" (1986) — a full 24 years before "In 2010, we shipped the first prototype extreme ultraviolet (EUV) lithography tool (TWINSCAN NXE:3100)." Cumulative EUV shipments then took a full decade to reach "the 100th EUV system shipment," celebrated "at the beginning of 2020" (asml.com/en/company/about-asml/history, Tier 1). That is a handful of units per year for a decade, not the sustained doubling that Sahal's identity requires.

When cumulative production is this low and this far from exponential, Wright's Law and Moore's Law do not collapse into one curve — Sahal's own math says they diverge. So the EUV note's claim that Nikon/Canon "have been unable to enter EUV after 15+ years" despite no patent wall reads correctly on the calendar-time axis (institutional experience accumulated since 1986) rather than the production-volume axis Wright's Law describes. The tacit-knowledge mechanism (learning by doing, Arrow 1962) is real in both cases — but EUV is a case where that learning is time-shaped, not volume-shaped, precisely because Sahal's own precondition fails for it.

Why this was hop-worthy

It turns a 0.75-cosine coincidence into a falsifiable structural claim: Sahal's own equation tells you which axis (time or volume) a given moat should be read on.

Further leads

• Devendra Sahal himself (person behind the 1979 identity) — unexamined, could be a person-hook.
• Whether Nikon/Canon's own (much larger) DUV production volumes are closer to the exponential regime, which would sharpen the contrast.

Entity candidates

• Devendra Sahal — person — coined the 1979 identity the vault already cites secondhand via Lafond et al.; no primary of his own read yet.
• Kenneth Arrow (1962, "learning by doing") — person — named the mechanism (tacit, non-transferable production experience) underlying Wright's Law; not yet an entity page.

Hop chain

Hop 1 — Lafond, Bailey, Bakker, Rebois, Zadourian, McSharry & Farmer, "How well do experience curves predict technological progress?" (2017), https://arxiv.org/abs/1703.05979

• Hook type: Mechanism question (re-reading the vault's own primary source for the exact wording of Sahal's precondition)
• Hook: The identity is conditional — "in the deterministic limit" and "exponentially increasing cumulative production" — not a universal equivalence.
• Why followed: To check whether the seed pairing rests on the identity's condition holding generally, or specifically.
• Key findings: The condition is explicit and testable against any given technology's real production history.

Hop 2 — Kenneth Arrow, "The Economic Implications of Learning by Doing" (1962), https://www.haverford.edu/sites/default/files/Arrow1962.pdf

• Hook type: Mechanism question / the person behind the thing
• Hook: Wright's Law describes that cost falls with cumulative production; Arrow's paper is the classic account of why — learning is embodied in the people and organization doing the producing, i.e., tacit.
• Why followed: To confirm the tacit-knowledge mechanism is the standard economic explanation for Wright's-Law-type curves, not a coincidence of vocabulary with the EUV note.
• Key findings: "Learning by doing" (Arrow's coinage) is exactly the same species of non-codifiable, experience-accumulated knowledge the EUV note calls tacit know-how.

Hop 3 — ASML company history, https://www.asml.com/en/company/about-asml/history

• Hook type: Surprising claim (quantitative) — checking whether EUV production is actually exponential
• Hook: The Zeiss partnership (1986) predates the first EUV shipment (2010) by 24 years, and cumulative shipments only reached 100 units after another decade.
• Why followed: Sahal's identity is only as good as its precondition; EUV's real production numbers are the test.
• Key findings: EUV production is low-N and slow-ramping (~100 cumulative units over a decade), nowhere near the sustained exponential growth Sahal's identity requires — meaning the ASML/Zeiss advantage is better read as calendar-time tacit accumulation than production-volume learning.

Surprise: expected the bridge (if real) to say Wright's Law and the EUV moat are "the same mechanism" — found instead that Sahal's own math predicts they should diverge for a technology this low-volume, and that divergence is what makes the EUV note's "15+ years" framing correct.

Saved hooks not followed:

• Devendra Sahal's own 1979 paper (person-behind-the-thing, unfamiliar name — vault only has him secondhand via Lafond et al.) — saved for a future hop.
• Nikon/Canon's DUV production-volume history — would let the contrast be quantified on both sides, not just ASML's.

post-worthy: maybe — a clean resolution of a flagged unlinked pair with a falsifiable mechanism, but it's an internal vault-connection payoff more than a standalone story on its own.