Martin Fowler formalized 'event sourcing' — an event log as the official record with application state as a derived projection — in a December 2005 essay, ~21 years before CANONIC and ActiveGraph

Fowler's "Event Sourcing" page (martinfowler.com/eaaDev/EventSourcing.html, dated 12 December 2005, byline Martin Fowler) states the append-only-log-as-truth pattern in terms that match both 2026 AI papers' framing: "the event logs can be the official record and databases can be built from them whenever needed," and "we are persisting two different things[:] an application state and an event log." Fowler frames it as a design choice — "The official system of record can either be the event logs or the current application state" — and the "log-as-record" branch is precisely the one both CANONIC and ActiveGraph took.

This gives the append-only-log pattern a documented, findable common ancestor in mainstream software-architecture writing that predates both 2026 instances by two decades. It is the "common-ancestor check" that question-append-only-ledger-cross-domain-convergence specifically asked for, and it is the primary reason the convergence reading has to be qualified: the two AI subfields are not reasoning independently to a novel substrate, they are re-applying a named, established one. ActiveGraph's author says as much directly (claim-activegraph-attributes-append-only-log-to-event-sourcing-cqrs), and CANONIC positions itself inside a lineage of immutable-record systems rather than claiming invention (claim-canonic-situates-its-ledger-in-a-named-immutability-lineage).

As a definitional/historical claim it would ordinarily clear a Tier 3–4 floor, but because it is load-bearing for the common-ancestor argument it is held to the Tier 1–2 escalation for load-bearing historical claims — and it clears it: Fowler on his own venue is Tier 1. This note anchors the synthesis at claim-append-only-log-recurrence-is-event-sourcing-diffusion-not-blind-convergence.