alpha-rl-mbg2n on H100 failed at LobSimCuda::new with
`CUDA_ERROR_NO_BINARY_FOR_GPU` loading book_update.cubin. Root cause:
ml-backtesting/build.rs read only `FOXHUNT_CUDA_ARCH` (set by
lob-backtest-sweep-template) but NOT `CUDA_COMPUTE_CAP` (set by
alpha-rl-template from `nvidia-smi --query-gpu=compute_cap` inside the
compile pod). On H100 it silently fell through to default sm_86; the
sm_86 cubin contains no PTX → no JIT path on sm_90 device.
The docstring claimed "Mirrors crates/ml-alpha/build.rs" — it didn't
(ml-alpha reads CUDA_COMPUTE_CAP). Completing the mirror now: detect_arch
returns sm_<NN> honoring (in order):
1. CUDA_COMPUTE_CAP numeric env (alpha-rl-template)
2. FOXHUNT_CUDA_ARCH sm_-prefixed env (lob-backtest-sweep-template)
3. nvidia-smi --query-gpu=compute_cap at build time
4. Default sm_86 (RTX 3050 Ti local dev)
Both production argo templates now produce sm_90 cubins on H100 and
sm_89 on L40S without further changes.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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