diff --git a/crates/ml-alpha/cuda/rl_reward_clamp_controller.cu b/crates/ml-alpha/cuda/rl_reward_clamp_controller.cu
index 1a8640e39..dd43cade7 100644
--- a/crates/ml-alpha/cuda/rl_reward_clamp_controller.cu
+++ b/crates/ml-alpha/cuda/rl_reward_clamp_controller.cu
@@ -224,47 +224,51 @@ extern "C" __global__ void rl_reward_clamp_controller(
         isv[RL_REWARD_CLAMP_RATIO_INDEX] = ratio_clamped;
     }
 
-    // Step 4: compute adaptive WIN/LOSS bounds: MARGIN × EMA, floored.
-    // No upper cap on WIN per the header note — the MARGIN ∈ [1, 5]
-    // × EMA composition is the structural bound. LOSS = RATIO × WIN
-    // with RATIO now adaptive.
-    const float win_eff  = fmaxf(MIN_WIN, margin * ema_new);
-    const float ratio    = isv[RL_REWARD_CLAMP_RATIO_INDEX];
-    const float loss_eff = ratio * win_eff;
-
-    isv[RL_REWARD_CLAMP_WIN_INDEX]  = win_eff;
-    isv[RL_REWARD_CLAMP_LOSS_INDEX] = loss_eff;
-
-    // ── C51 atom span — slow EWMA (was ratchet). ──────────────────
+    // Step 4 (G.2, 2026-05-24): WIN / LOSS bounds are STRUCTURAL — they
+    // stay at their trainer-seeded values (WIN=1.0, LOSS=3.0) matching
+    // the C51 atom span × 3:1 loss-aversion asymmetry. The previous
+    // adaptive widening was anti-correct: when clip_rate exceeded the
+    // 5% target, the controller WIDENED the clamp to accommodate the
+    // distribution, defeating the bound's structural purpose. The
+    // resulting positive feedback loop (large scaled rewards → wider
+    // clamp → larger V/Q targets → C51 atom support ratchets up → even
+    // larger scaled rewards permitted) was diagnosed in the F.5 200-step
+    // local smoke: WIN drifted 1.0 → 41.3 (41×) in 150 steps, scaled
+    // rewards of 14.71 flowed through, V regression spiked to l_v=104.
     //
-    // wwcsz followup: replace monotone-grow with slow EWMA so atom
-    // resolution focuses on the active reward range. Static ratchet
-    // wasted Δz on rare tails (V_MAX=20 with rewards mostly in
-    // [-5, +5] → Δz=2 wasted on extremes). Slow α=0.001
-    // (half-life ~700 steps) gives Q's atom mapping time to be valid
-    // across encoder/head co-adaptation. Floors at [-1, +1]
-    // preserve the original C51 baseline as the worst case.
-    const float v_max_prev = isv[RL_C51_V_MAX_INDEX];
-    const float v_min_prev = isv[RL_C51_V_MIN_INDEX];
-    const float v_max_target = fmaxf(V_BOUND_FLOOR, win_eff);
-    const float v_min_target = fminf(-V_BOUND_FLOOR, -loss_eff);
-    // Bootstrap on sentinel 0 — first emit replaces directly (per
-    // pearl_first_observation_bootstrap).
-    float v_max_new, v_min_new;
-    if (v_max_prev == 0.0f) {
-        v_max_new = v_max_target;
-    } else {
-        v_max_new = (1.0f - V_BOUND_EWMA_ALPHA) * v_max_prev
-                  + V_BOUND_EWMA_ALPHA * v_max_target;
-        v_max_new = fmaxf(V_BOUND_FLOOR, v_max_new);
-    }
-    if (v_min_prev == 0.0f) {
-        v_min_new = v_min_target;
-    } else {
-        v_min_new = (1.0f - V_BOUND_EWMA_ALPHA) * v_min_prev
-                  + V_BOUND_EWMA_ALPHA * v_min_target;
-        v_min_new = fminf(-V_BOUND_FLOOR, v_min_new);
-    }
-    isv[RL_C51_V_MAX_INDEX] = v_max_new;
-    isv[RL_C51_V_MIN_INDEX] = v_min_new;
+    // The diagnostic-only state (pos_max_ema, neg_max_ema, RATIO,
+    // clip_rate_ema, MARGIN) is still maintained above so the diag can
+    // surface what the system *would* adapt to under an unbounded
+    // policy — useful for understanding reward-distribution drift. But
+    // the LOAD-BEARING WIN_INDEX / LOSS_INDEX slots are now write-once
+    // (trainer's isv_constants seed). Per
+    // pearl_audit_unboundedness_for_implicit_asymmetry: structural
+    // bounds must NOT adapt in response to the very signal they're
+    // meant to bound.
+    //
+    // Suppress unused-variable warnings on the diagnostic-only blocks.
+    (void) margin;
+    (void) ema_new;
+
+    // ── C51 atom span — STRUCTURAL (G.2, 2026-05-24). ─────────────
+    //
+    // The atom-span EWMA was the SECOND half of the positive feedback
+    // loop disabled in Step 4: with WIN/LOSS adapting to fit large
+    // scaled rewards, V_MAX/V_MIN ratcheted up to match (e.g., F.5
+    // smoke saw V_MAX=2.66 by step 149 from a seed of 1.0). Larger
+    // atom span then permitted V to predict larger values, amplifying
+    // advantage magnitude and PPO/V losses.
+    //
+    // Fix: the C51 atom span stays at its trainer-seeded value
+    // (V_MAX=1.0, V_MIN=-1.0). Q's distributional representation has
+    // FIXED structural resolution matching the seeded WIN/LOSS bounds
+    // — any reward signal outside that range is clipped at
+    // apply_reward_scale rather than absorbed by widening atoms.
+    // Per pearl_c51_atom_span_must_track_clamp_range: atom span tracks
+    // the SEED clamp range, not the runtime-adapted one.
+    //
+    // V_BOUND_FLOOR no longer used; keep the constant for any future
+    // re-introduction.
+    (void) V_BOUND_FLOOR;
+    (void) V_BOUND_EWMA_ALPHA;
 }