Blog
Notes from the research programme: what was tried, what was measured, what failed.
Five failures in the long stage, and a blind tempo test
Of 56 decided candidates, 5 passed the oracle's short stage and failed the long one. What they cost, and how a blind, pre-registered test of search speed found no hint of a time tax.
The first edge case: mate with bishop and knight
On 2026-10-16 the oracle adopted its first edge case: a change that concerns only king, bishop and knight against a bare king. What an edge case is, what the change does, and what was shown before and in the oracle.
The Arena, and why its latest values are probably a little low
The Arena measures Coherent against other engines. The published value for 0.2.10 comes from a build without the processor switch and is probably a little low compared with a corrected build under the same conditions. When to expect a value without this error.
What version 0.2.0 lost: a regression report
Parts of Coherent's search had run without their optimised processor variant for days. Three properties lost silently with version 0.2.0 were established on 2026-10-15; this entry covers the losses, the measurements and the changes.
Coherent 0.2.10: 3670 ± 52 over 7 anchors
Project measurement, not in the register. After 3,584 games against 7 foreign engines Coherent 0.2.10 stands at 3670 ± 52 (anchored to CCRL Computer Chess Rating Lists, a public ranking of chess engines from games under standard conditions. blitz ratings) and replaces 0.2.6 at 3620 ± 52 as the published figure; over the 7 shared anchors the measured gain is +51 ± 8.
From 5 to 4 nElo: what a finer oracle test would cost
A model calculation, not a measurement: if the oracle's sequential test lowered its upper bound from 5 to 4 nElo Normalised Elo: the Elo difference divided by the spread of the game results, so that the SPRT bounds mean the same at different time controls., it would need roughly a quarter more oracle time on the real candidate mix, with few additional adoptions.
Inside the network of Coherent 0.2.13
How the neural network in Coherent 0.2.13 sees a position, how large it is, how it computes with integers, and where it comes from: fine-tuned from the previous network and tested against it in the oracle.
A smaller ReLU network for the maximum of 6 numbers
An exact ReLU network 6 → 16 → 36 → 1 with two hidden layers computes the maximum of 6 numbers. It is smaller than the previously published 17 and 41 widths; the full network and an exact checker are included.
Peaceable queens on 17 by 17: at most 62
On a 17 by 17 board, the largest number m of white and of black queens that can coexist without attacking across colours is at most 62. The complete proof is included, with the table from its one computer step.
Completing queens on a board 21 by 21
On a 21 by 21 board, one position of five queens that do not attack each other cannot be completed, while every placement of four non-attacking queens can. The result is qc(21) = 4, shown by a weighted-line calculation and an enumeration.
The domatic number of the queens graph for 11 and 12
For the queens graph on 11 by 11 and 12 by 12 boards, the domatic number is 19 and 21. Both decompositions are shown in full, along with the set S used for the upper bound on the smaller board.
Found while searching for Elo
A research session of agents looked for open maths questions near chess engine algorithms, aiming at playing strength. It ended with 4 side findings: 3 about queens, 1 about ReLU networks. No gain in playing strength has been shown.
A day without a verdict
For about 22 hours the oracle gave no verdict. Monitoring recorded no outage; the candidates did not reach it. The fast path found no winner, and the clock path was sent back and had few machines.
Epochs 9 and 10: a proof for the clock, a rule for the load
Epochs 9 and 10 changed little in what the oracle measures. They changed how it decides when it may measure: a clock proof that found no user, a release held up by its own rhythm, and a load rule that replaced the old one.
Epoch 8: a stricter oracle
Epoch 8 changed no line of the engine. It changed how the oracle reaches a verdict: exact values instead of rounded ones, watched measuring cores, and a first attempt at the switch that failed.
Epochs 1 to 7: how the oracle's rules took shape
The oracle's measuring rules are grouped into epochs. This entry covers the first seven, from 28 August to 9 October 2026: what changed at each anchor, and what the table of runs does and does not show.
Mutants turn red
A passing test says little if it would also pass on broken code. The agents behind Coherent break their own code on purpose. Cases where mutants stayed green, where everything was red and still wrong, and where the method itself erred.
Coherent 0.2.6: 3620 ± 52 over 7 anchors
Project measurement, not in the register. After 3,150 games against 7 foreign engines Coherent 0.2.6 stands at 3620 ± 52 (anchored to CCRL blitz ratings) and replaces 0.2.0 at 3600 ± 52 as the published figure; over the 7 shared anchors the measured gain is +21 ± 8.
Test positions in the training data
A check on 7 October 2026 found that Coherent's own self-play data contain positions from its test sets: about 3 in every million. How it was found, what was decided, and one larger point that is still open.
Faster, but not stronger
Four rejections in a row for Coherent. One change was meant to make the engine faster: it passed the short stage and showed no gain in the long stage. What the numbers say, and what they leave open.