Initial B-10 commit placed `launch_q_distribution_stats` after the
`dqn_head.forward(h_t)` at line 6615 — but that's inside
`step_with_lobsim`, the legacy non-GPU path. The actual GPU path
exercised by `alpha_rl_train` is `step_with_lobsim_gpu` (line 8402),
which has its own h_t-based Q forward at line 8632. The G1 diag fields
(q_dist_entropy_mean, q_value_range_mean, q_value_abs_max) returned 0
locally because the launch never ran in the GPU path.
Added the same launch_q_distribution_stats call after line 8632.
The non-GPU launch at 6615 is left in place — `step_with_lobsim` is
still callable; per `feedback_no_partial_refactor.md` both paths are
instrumented consistently.
Validated locally (RTX 3050 Ti, 200+50 b=16 fold-1):
q_dist_entropy_mean = 2.6482 (was 0)
q_value_range_mean = 4.9257 (was 0)
q_value_abs_max = 3.8715 (was 0)
The entropy value 2.65 is consistent with a near-uniform softmax over
Q_N_ATOMS=21 atoms with some learned concentration (ln(21)=3.04 = full
uniform, 0 = one-hot delta). Range and abs_max in 4-5 unit scale match
the locally-adapted atom support.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
c1dc84a345