Decisions

Questions the agent is not allowed to settle, and how the owner settled them

The brief lists the decisions that belong to a human: physics modelling choices, licence and data questions, which properties to prove, use of the compute cluster, and benchmark failures that aren’t explained by a bug. When the agent reaches one, it writes the question down with context and a recommended answer, carries on with whatever isn’t blocked, and waits. Numbers (OQ-n) match the project’s internal record. Newest first within each group.

Awaiting a decision

  • OQ-17: what licence text the package metadata should carry while no release licence is chosen. It blocks nothing while the code is private.

Settled

OQ-16 · Kinetic ranges, ITER shapes and the αMHD cap for the M2 datasets

Decided 2 Oct 2026. The owner set one dataset per machine, MAST-U and ITER. The geometry ranges were measured (OQ-15); the kinetic ranges, the ion species and a cap on the normalised pressure gradient αMHD were proposed by the agent from memory and needed a decision before any data was generated. Three questions: (a) do the kinetic ranges and ions stand per machine; (b) is one ITER plasma shape with the current ramp-up’s q profiles enough, or should 15 MA baseline equilibria be added first; (c) a fixed cap, a cap that depends on the magnetic shear, or sampling αMHD in place of βe.

Decision. (a) Approved as proposed for both machines: D and carbon for MAST-U, D-T as one ion of mean mass and neon for ITER (ranges in datasets). (b) One shape is enough for version 1; the missing baseline is recorded as a limit (K-016) and baseline shapes come before an ITER version 2. (c) Fixed caps for version 1 (MAST-U 4, ITER 2), a shear-dependent cap to follow (K-017). The two datasets were generated the same day (entry 17).

OQ-15 · Sampling ranges and TGLF settings for MAST-U

Decided 2 Oct 2026. MAST-U is outside both surrogates TORAX ships with (aspect ratio fixed at 3, or elongation up to 1.5). The agent proposed ranges from memory, not checked against a source. Decision: the agent measures the geometry ranges on equilibria rather than choosing them, and the kinetic ranges go to a physics check (became OQ-16); a second region besides MAST-U, each tagged so it can be selected alone or pooled (became the ITER dataset); TGLF with the SAT2 saturation rule and both magnetic perturbations; CGYRO spot checks of TGLF at M4. Measured, the MAST-U geometry is narrower in shape than the proposal (triangularity on interior surfaces at most 0.24, not 0.6).

OQ-14 · One cluster job to check TGLF and time it

Decided 2 Oct 2026. TGLF’s licence was settled by the owner’s pointer to the public GACODE repository (Apache-2.0). The remaining install check, TGLF as TORAX’s transport model, could not run on a login node. Approved: one CPU node for at most 30 minutes, running TORAX’s TGLF tests, a TORAX step with TGLF, CGYRO’s regression suite, and TGLF on a few hundred points of the sampling space to measure the cost per case. Outcome (entry 16): TGLF 9/9 regression cases; tglf2py wrapper 11/11; TORAX TGLF transport-model tests 3/3; CGYRO 21/21C-069; 2.2-2.5 s per case alone, 2.6 s median in a 64-worker pool; about 700 core-hours per 10^6 casesC-068; the TORAX step with TGLF failed (fails at the first step: NaN fluxes on the axis face, about 10^6 gyro-Bohm units on the edge face (K-015)C-070, K-015). The first submission failed at start-up on a shell setting in the job script, with no compute used, and was resubmitted.

M1 physicist review

Passed 1 Oct 2026. The last M1 acceptance criterion is a review by a physicist. The owner did the review as reviewer of record. The agent set out six items, each with its evidence and a recommendation; the owner accepted all six recommendations as written.

  1. Benchmark tolerance, against RAPTOR on the published ITER L-mode case (OQ-12): the t = 10 s profiles within 2% for Ti, Te, ψ and q, and within 0.1% for the densities; the line-averaged temperature and density traces within 5% over 0–10 s. The fusion and Ohmic powers are reported, not gated: the paper’s two codes differ by 13–22% on the alpha ion/electron split. Result at the published settings: T_i 1.23% (1.1%), T_e 0.28% (0.71%), n_e 0.03% (0.03%), psi 0.49% (0.41%), q 0.69% (0.70%)C-050; transient 2.4% at dt = 0.05 s, 2.9% at dt = 0.00625 s (1.0% at t = 10 s)C-053. Both pass.
  2. TORAX version. The differences between the paper’s TORAX run and TORAX 1.4.3 (T_i 0.13%, T_e 0.50%, n_e 0.01%, psi 0.08%, q 0.16%; Ohmic power density 3.6%C-051) are accepted as a code-version effect.
  3. Pedestal. The fixed-pedestal model’s pinning source removes 87–98%C-038 of the heating in the ITER hybrid ramp-up. Accepted for core profiles inside ρ = 0.9; power crossing the edge is not taken from these runs (K-010). Revisited at M3.
  4. Time step. The ITER hybrid example settings are not converged in time (entry 3). They are used only to check the wrapper. Runs used as a physics reference use a step at which halving it changes the core temperature by at most 1% after the first 5 s. Solver stalls stay reported (OQ-5).
  5. ASCOT5 alpha source. Orbit tolerance 10-7 (0.348 at 10-6, 0.331 at 10-7C-058 of the birth power to ions at 10-6 and 10-7); 640 markers give the total (72.2 MW vs 70.5 MWC-059 against TORAX’s local model) and the electron/ion split, and the radial shape waits for the production run (OQ-13). Holding the source fixed for 2 s is accepted (+0.03% in stored energy (central T_e +0.5%, T_e and T_i profiles 0.6%)C-060). The small excess in the markers’ birth power (K-011) is to be explained before neutral-beam ions are added.
  6. Fallback, pedestal and sawtooth models: OQ-1 below.

The claims these items judged are marked reviewed in the claims register.

OQ-1 · The fallback transport model

Decided 1 Oct 2026, at the M1 physicist review. M0 needed a toy transport model to exercise the loop, and a smooth critical-gradient form was used. The trusted fallback for real runs is TORAX’s Bohm/gyro-Bohm model, which is already the fallback behind the guard inside TORAX. The critical-gradient form stays as the closure of the Tokamak Toolkit’s own analytic test loop only. For M1 the pedestal is TORAX’s fixed pedestal, and sawtooth mixing is represented by a constant diffusivity near the axis (the ITER examples have no sawtooth model); a sawtooth model is added when a case needs one.

OQ-13 · A third ASCOT5 job, for the production run

Decided 1 Oct 2026. The second ASCOT5 job (entry 12) finished its tolerance check but not its production run: a per-marker time limit, set too short by the agent, stopped 2823 of 6400 markers, 18% of the birth powerC-057. A third job is approved: up to eight hours on one node, the production run at the tighter tolerance with no time limit, and a check at a tighter one still. The M1 physicist review is not held for it.

Outcome, 2 Oct 2026 (entry 15). The job ran in 3 h 37 min and every alpha finished. Total heating: 71.8 MW vs 70.5 MWC-064. The tighter check changed the heating by electrons -0.16%, ions +0.08%C-066, so the working tolerance stands. No further job is requested.

OQ-12 · Which published profiles the benchmark is compared with

Decided 1 Oct 2026. M1 asks for a match to published profiles. The ITER hybrid scenarios have no published profiles from a second code. The TORAX paper publishes one quantitative comparison with an independent code, RAPTOR, on an ITER L-mode case, with its full configuration and the profiles as vector figures. That case is the M1 physics benchmark, compared with both RAPTOR’s and the paper’s own TORAX curves, first at the published time step and then at a converged one (entry 11). The ITER hybrid runs remain the stiff-transport and pedestal case. The tolerance was set at the M1 physicist review.

OQ-11 · A second ASCOT5 cluster job

Decided 1 Oct 2026. The first ASCOT5 job (entry 10) showed that the orbit tolerance chosen for speed loses alphas that should be confined (C-043), and that at the tighter tolerance 640 markers resolve the total alpha heating but not its radial shape (C-045). A second job is approved: one node for up to four hours, ten times more markers at the tighter tolerance, and a check at a tighter one still. Further jobs need their own approval. Outcome: entry 12 and OQ-13.

OQ-10 · Which radial variable the guard’s features use

Deferred 1 Oct 2026, to M3. The guard checks whether a plasma state is inside the region the surrogate was trained on, using features such as normalised temperature gradients. The Tokamak Toolkit computes those gradients with respect to the normalised flux radius, scaled by the geometric minor radius; QLKNN, as TORAX feeds it, uses the midplane minor radius of each surface. On the ITER hybrid scenario the two differ from +19%C-032 in the core to about a third at the edge (K-008). No run is affected yet. The convention will be chosen when the first trained surrogate exists (M3), and in any case before a verified domain is certified (M4).

OQ-9 · Fast-ion sources from ASCOT5

Decided 1 Oct 2026. Fusion alphas first, born from the plasma profiles TORAX computes, as a direct check against TORAX’s own alpha heating. Neutral-beam ions follow once a physicist has approved the injector geometry. One short test job on the compute cluster is approved; each further job needs its own approval.

OQ-5 · What “reproduces the benchmark” means

Decided 1 Oct 2026. Two comparisons: the Tokamak Toolkit’s loop against TORAX’s own output at the same settings (a check of the wrapper), and against the published cross-code comparison (a physics statement). The wrapper check must agree to 10-10 (it passes at round-off: C-006, C-007). The physics tolerance is set by the physicist reviewer at the M1 gate (set: see the M1 physicist review). Because the published reference runs are not converged in time (entry 3, C-012, C-013), the physics comparison is made at the published settings first, then at a converged time step, with the difference reported as its own line in the discrepancy budget. Solver stalls stay reported, not tuned away by relaxing a line-search setting (entry 5, C-011). Energy and particles must balance to 10-6 per step on converged steps (entry 8, C-035, C-036); the flat-top reference solver’s defect (C-037) is reported, not required to close.

OQ-3 · Where the code will live

Decided 1 Oct 2026. A private hosted repository, where the continuous-integration workflow runs on every change. The code stays private; this log is how the work is shown. Until the workflow has passed, “tested” in the claims register still means “asserted by a named test, run before each publish”.

OQ-8 · Which machine description for the equilibrium solver

Decided 30 Sep 2026. MAST-U. FreeGSNKE’s repository already ships a MAST-U-like machine description (coils, passive structures, limiter, wall; credited to UKAEA) under the same open licence, so nothing had to be assembled from published drawings. It is fetched from a pinned upstream version with a checksum per file. This covers the equilibrium work only: the M1 transport benchmark stays with the ITER scenario, because no published TORAX MAST-U scenario exists and QLKNN was not trained on spherical-tokamak conditions.

OQ-7 · Input data for a STEP extension

Deferred 30 Sep 2026. Extending the benchmark to a STEP power-plant flat-top is a future extension, not part of M1. The work stays with the ITER benchmark and MAST-U for now; the data question reopens if and when the extension is picked up.

OQ-6 · Which benchmark

Decided 21 Sep 2026, amended 30 Sep 2026. The ITER hybrid scenario that ships with TORAX: an 80-second current ramp-up, and a 5-second flat-top as the quicker check. A planned STEP extension was deferred on 30 Sep (OQ-7).

OQ-4 · Newton-Raphson for the coupling loop

Decided 21 Sep 2026. Approved. The M0 loop used relaxed Picard iteration, which oscillates instead of converging once transport becomes stiff: on the toy model’s original settings the residual sat between 3 × 10⁻² and 8 × 10⁻² after 12 iterations. The owner approved a Newton-Raphson solver with derivatives from automatic differentiation and a fixed iteration count, keeping Picard as the fallback, and stall reporting for both (entry 1).

OQ-2 · Where to run

Decided 21 Sep 2026. Tests and the early milestones run on an interactive node with one datacentre GPU. Anything longer goes through the cluster’s batch system on an allocation the owner named, and every job is announced to the owner before it is submitted.

Code and first draft by Claude (Anthropic), working to a brief by Vignesh Gopakumar, who reviewed and approved this page. How this is built · Tokamak Toolkit home