Benefit Ledger · disputed · Mathematics
In August 2026 Epoch’s open-problems index listed a Hadamard matrix of order 668 as Solved (AI) by a three-human plus Claude team, while the dedicated problem page still appeared to say open. The construction is included as disputed until those sources agree.
Current score
+0.09
A Hadamard matrix of a new order would be notable (tier 2). Human–AI team with unnamed Claude (0.45). Evidence is inconsistent Epoch pages (0.25). Realization is a reported finite matrix, not a converged public record (0.40).
Existence of Hadamard matrices is classical; order 668 was a remaining computational target. Because Epoch’s index and the problem page disagree, this event is disputed with reduced evidence. Claude’s version is undisclosed, so identity is version-unspecified in the Claude family.
Unspecified Claude used by a three-human team in the reported Hadamard 668 construction.
Epoch commentary credits a three-human plus Claude team; no Fable/Opus SKU is given, so Claude stays version-unspecified and attribution stays modest.
Attribution 0.4500 · Credit share 100% · Anthropic
Epoch’s index/changelog has marked Hadamard order 668 as solved by a three-human plus Claude team.
outcome · supported
Epoch’s dedicated Hadamard page and the index currently agree that a matrix is public and verified.
significance · disputed
primary sources
Epoch AI · other · 12 Aug 2026
Epoch AI · other · 12 Aug 2026
Secondary domains: Computer Science
13 Sep 2026 · 0.00 → 0.09
Imported events under methodology 0.1.
