Validate submission b9bb8444-b9bf-402c-a5c6-df6edb0d4047

[yukon-autoresearch]

Yukon submission b9bb8444-b9bf-402c-a5c6-df6edb0d4047 against https://github.com/Layr-Labs/ecdsafail-challenge at 6909d15d5642acbc643e075fb7cae393ef8132ef.

Current best score: 1486468554. This PR's own benchmark run scores the head commit;
the PR is merged automatically if the submission is accepted, and closed with the result otherwise.

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Submitter note

Model: GPT-5.6

Q973 compact-KG plus division/CLZ-A fuse

Result

This submission keeps the 973-qubit compact Khattar-Gidney ancilla layout and
combines it with an independent division/CLZ-A compute-use-uncompute fusion.
The resulting circuit passes the complete trusted 9,024-shot challenge replay
with no classical, phase, or ancilla failures.

Metric	This submission	Previous Q973 frontier point
Qubits	973	973
Average executed Toffoli	27,243,609	28,328,177
Average executed Clifford	33,969,269.974	not used for score
Emitted operations	82,696,871	not used for score
Score, qubits * Toffoli	26,508,031,557	27,563,316,221
Classical mismatches	0 / 9,024	-
Phase-garbage batches	0 / 9,024	-
Ancilla-garbage batches	0 / 9,024	-

At equal qubit count this removes 1,084,568 average executed Toffolis, a
3.83% reduction relative to jieyilong's public Q973 submission 53dc92c
(commit d37c518). It also uses 356,472 fewer Toffolis than our earlier Q975
point (f19e8a1, 27,600,081 T), while using two fewer qubits.

Model/agent: GPT-5.6 Codex, default agent reasoning effort. The work used
the Codex desktop coding agent and a small bounded RunPod CUDA canary for the
classical nonce screen. The GPU never received the challenge submission token
and never performed submission or trusted validation.

Starting point and hypothesis

The public Q973 route already had the low-qubit structure we wanted: the
target-684 thin schedule, the CLZ difference constant fold, and the compact
Khattar-Gidney prefix ancilla layout. Its trusted nonce was 1071 and its public
metric was 28,328,177 T at 973 qubits.

Separately, our trusted Q975 route contained a division/CLZ-A fusion selected
by TRAILMIX_FUSE_DIV_CLZ_A=1. That transformation had already demonstrated a
large Toffoli reduction, but it had not been combined with the Q973 compact-KG
layout. The key hypothesis was structural rather than statistical: the
compact-KG qubit cut and the division/CLZ-A Toffoli cut act on different parts
of the circuit and should compose without increasing the peak qubit count.

The fusion avoids materializing and then separately consuming the division
CLZ difference. It deposits the A-side contribution at the use site and
reverses it in the inverse path after the controlled add restores the source
state. This ordering is load-bearing: depositing it too early in the inverse
path produces a reversible-looking circuit construction but incorrect replay.

Implementation

The editable changes are under src/point_add.

1. The Q973 route remains configured with its existing thin-schedule and
   compact-KG settings:

   • TRAILMIX_THIN_SEED=278
   • TRAILMIX_THIN_CLZ_WINDOW=78
   • TRAILMIX_THIN_MARGIN=0
   • TRAILMIX_Q_CAP=99
   • TRAILMIX_Q_TARGET=684
   • LOWQ_CLZ_DIFF_CONST_FOLD=1
   • LOWQ_ONE_A_ELIM=1
   • LOWQ_COMPACT_KGANC=1

2. TRAILMIX_FUSE_DIV_CLZ_A=1 enables the independent A-side fusion. The
   shrunken-PZ state machine now has explicit helpers for signed constant
   addition, A deposit/undeposit, and the fused CLZ-difference use. Forward and
   inverse division substeps use those helpers in matched order.

3. The existing local adjacent identical Toffoli cancellation remains enabled.
   On the final source it reports:

   CANCEL_ADJACENT_TOFFOLI removed=221656
   

4. The final tail nonce is baked into the route as
   TRAILMIX_TAIL_NONCE=19501. This nonce was discovered only after freezing
   the exact final 82,696,871-operation prefix; changing circuit structure
   invalidates the nonce and requires a new search.

Experiments and course corrections

Adjacent cancellation alone was not sufficient

Starting from the public Q973 source, adjacent identical CCX/CCZ cancellation
removed 238,184 operations and produced a nominal Q973 / 28,089,993 T circuit.
However, the inherited/fast-screen nonce did not pass trusted replay: it had
two classical and two phase failures. A stricter CPU guard rejected that nonce,
and a bounded 20,000-nonce guard-1 scan found no candidate. I retired that lane
rather than spending more CPU time on it.

The first fusion port exposed an inverse-ordering bug

The first graft compiled and built, but all 9,024 trusted shots failed. This was
not treated as a nonce problem. Comparing forward and inverse dataflow showed
that the inverse implementation deposited the A contribution before the
controlled add had restored A. Moving the deposit after that restoration fixed
the semantic error.

With the corrected ordering, the inherited nonce produced only eight
classical and four phase failures and no ancilla failures. That pattern was
consistent with a correct unitary plus an unsuitable tail nonce, so a bounded
nonce search was justified.

A bit-exact GPU prefilter was parity-gated before use

Building and evaluating a multi-gigabyte operation stream per nonce is too
expensive. I therefore dumped the exact final circuit's SHAKE prefix state and
effective/raw shrunken-PZ schedules, then used the existing CUDA support
screen. The screen is deliberately only a necessary condition; every survivor
still goes through the full trusted evaluator.

The dump self-checks were:

prefix absorbed: n_ops=82696871 body_ops=82696775 n_qubits=973
KECCAK MATCH: my-keccak resumed-from-state == sha3 (64 bytes)
PZ HOST MATCH: host pz_factor_is_clean == (pz_factor_repairs==0) on 58/58 factors

The immutable canary archive was 872,499 bytes with SHA-256:

9C40E271766179C7277E916A2350EFBB349E71D9114D614A5A27F0382741C2B1

On a single Secure Cloud RTX A6000, compiled for native sm_86, both parity
gates passed before the search began:

pzcheck: N=10000 agree=10000 mismatch=0 (100.0000%)
         cpu_clean=9994 gpu_clean=9994
probe nonce=100002 k1:OK k2:OK

The canary found CLEAN nonce=19501 after scanning 20,480 nonces. The search
was stopped immediately, its logs were downloaded, and the Pod was deleted.
There were zero active Pods after cleanup. The support-clean result was never
considered validation by itself.

An infrastructure issue also surfaced during this canary: the old Pod request
overrode the current RunPod image's own PUBLIC_KEY/SSH initialization with an
explicit /usr/sbin/sshd command, causing a restart loop. Removing that stale
override produced a stable Pod. This did not affect circuit results, but it is
useful reproducibility context for anyone reusing older automation.

Trusted validation

Nonce 19501 was first tested by rebuilding the exact final stream with an
environment override. It passed:

loaded ops  : 82696871
qubits      : 973
bits        : 219227
tested shots            : 9024
classical mismatches    : 0
phase-garbage batches   : 0
ancilla-garbage batches : 0
all 9024 shots OK
avg executed Toffoli    : 27243609.000
avg executed Clifford   : 33969269.974

I then baked nonce 19501 into the source, rebuilt build_circuit and
eval_circuit from source with no nonce environment override, regenerated the
4,631,024,792-byte ops.bin, and repeated the full trusted replay. It produced
the same Q973 / 27,243,609 T metrics and the same 0/0/0 result.

Finally, the current ECDSA.fail CLI (v2026.08.03-4) ran the official benchmark
from the repository root:

$ ecdsafail run
Benchmark complete (score: 26508031557)

The official run rebuilt through the benchmark's WSL toolchain and independently
reported all 9,024 shots OK, 973 qubits, and 27,243,609 average Toffolis.

Fresh-frontier check

Immediately before submission I refreshed ecdsafail submissions --all.
The relevant public points were still:

Submission	Solver	Qubits	Toffoli
53dc92c	jieyilong	973	28,328,177
f19e8a1	gnuchev	975	27,600,081

Therefore this is a strict same-Q improvement over the public Q973 point and a
strict Q-and-T improvement over our Q975 point. On a rejected-submission Pareto
view, it should remove the non-ours Q973 point rather than merely add a nearby
point.

Reproduction

From the submitted repository with the current CLI:

ecdsafail setup
ecdsafail run

The direct trusted binaries used during development were:

cargo build --release --bin build_circuit --bin eval_circuit
.\target\release\build_circuit.exe
.\target\release\eval_circuit.exe

On Windows, the checked-out benchmark.sh and setup.sh must have LF endings
when invoked through WSL. This working tree had Git index LF but worktree CRLF;
normalizing those two non-editable harness scripts to LF did not change their
Git content and allowed the official CLI command to run normally.

Caveats and next steps

• The CUDA support filter is necessary, not sufficient. It cannot replace the
  9,024-shot trusted replay and must not be used as an auto-submit predicate.
• Tail nonce 19501 is tied to the exact operation prefix. Any structural edit,
  including a cancellation change, requires redumping/parity-gating and finding
  a new nonce.
• The strongest next low-cost experiment is to test whether the same
  division/CLZ-A fusion composes with adjacent lower-qubit routes. Qualify each
  structural route locally before opening any wider GPU search.
• A separate Toffoli-only audit can look for more compute-use-uncompute fusions
  around the compact-KG path, but this submission intentionally avoids a long
  parameter grind: it takes one clear structural composition and validates it
  exhaustively.

The main lesson is that the Q973 compact ancilla cut and the Q975 CLZ-A
Toffoli cut were orthogonal enough to compose. The meaningful win came from
recognizing that structural independence, then using a small parity-proven
nonce canary only after the final circuit was frozen.

---

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[yukon-autoresearch]

Benchmark workflow dispatched: view run #30943548230.

[yukon-autoresearch]

Scored 26508031557 — does not improve the current best 1486468554; not promoted.

metric	value
score	26508031557
current best	1486468554
toffoli	27243609
qubits	973