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Vals publishes a buildable Lean proof for the shortest-path algorithm its ten agents wrote

Ten Claude Opus 5.5 agents produced the algorithm and a machine-checked proof of its runtime bound in about 15 hours. The theorem covers sparse directed graphs, and the margin over Dijkstra grows as the twelfth root of log n.

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Illustration accompanying Vals publishes a buildable Lean proof for the shortest-path algorithm its ten agents wrote

What happened

  • Vals AI published a research post on September 20th in which researcher Geby Jaff said ten Claude Opus 5.5 agents devised a shortest-path algorithm, C-HD, and a Lean proof of its correctness and runtime bound in about 15 hours.
  • For graphs with roughly m = n(log n)^(3/4) edges, Vals says C-HD's proved upper bound is O(n(log n)^(11/12)) against O(n log n) for Dijkstra, with no elapsed-time result for a real graph.
  • The formal program certifies that bound only where m <= n floor((floor(log2 n))^(3/4)), and falls back to Bellman-Ford on graphs denser than the certified condition allows.
  • Vals released the Lean package with the theorem, an informal paper, build instructions and verification records, and the repository says the frozen project builds and proves its statements with no remaining theorem hypotheses.

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Why it matters

  • precedent Anyone else claiming their agents did research now has a published example of what a submission a reader can check looks like, down to build instructions and verification records.
  • constraint The proof cannot support a buying decision about speed. A team that wants faster shortest paths has to implement C-HD and time it on graphs inside the certified density band.
  • cost Lean does not check novelty, so validating the interesting part of the claim falls to algorithm specialists, and their time is scarcer than a leaderboard reader's.

The two bounds differ by a factor of (log n)^(1/12) at the density Vals chose for its comparison [5]. That factor grows slowly. Take a graph with 2^20 vertices: log2 n is 20, and 20^(1/12) is about 1.28 [16]. So around a million vertices the proved bound sits roughly 22 percent below Dijkstra's, and Vals says practical speed still needs separate scrutiny [16][19].

Density is where the claim gets narrow. The formal program's certified condition is m <= n floor((floor(log2 n))^(3/4)) [6]. At 2^20 vertices, floor(20^(3/4)) is 9, so the theorem covers graphs of at most nine edges per vertex, about 9.4 million edges on 1,048,576 vertices [17]. Vals says the comparison targets a band of densities where a 2025 paper and a 2026 follow-up on deterministic directed shortest paths left room to improve [14].

I would check the accounting first, and it holds up. The method runs bounded searches from a frontier of discovered vertices, and a newly encountered vertex can count against a local search limit even when the edge leading to it fails to improve a distance estimate [8]. Search trees and pivots then organize the work that follows [8]. The stated bound also charges sorting outgoing edges, reading the input and producing the output [7]. Vals makes the point itself: a proposed algorithm can appear faster if preparation is treated as free [7].

Krishnan and Nashold built Vals on the premise that model buyers need evaluations grounded in actual work [15]. The record of this run is researcher Geby Jaff's own account. He gave the agents roles and a message board where they could exchange ideas, challenge proposed approaches and redirect their work, and he counted 733 messages before they finished C-HD [9]. Over about 15 hours that is roughly 49 messages an hour, one every 74 seconds [18]. He also instructed them to compare the result against recent research and obtain reproducible verification before claiming success [10]. The run was not a controlled comparison of agent teams against human researchers; Vals presents it as Jaff's description of how the work was conducted [10].

C-HD itself solves a well-defined problem: exact shortest paths from a single starting vertex in a directed graph with non-negative real edge weights, deterministically [3]. The yardstick is Dijkstra's algorithm at O(m + n log n) with a suitable priority queue [4]. Jaff said he asked the agents for two reviews; the repository identifies one completed internal agent review and describes the second as provisional, with reproduction fields pending [13]. Lean certifies the theorem inside its own formal computational model, and it does not settle whether the algorithms being compared charge work in equivalent ways [12].

What to watch

  • Whether algorithm specialists comparing C-HD with the 2025 and 2026 deterministic bounds agree the result is new.
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