diff --git a/crates/ml-alpha/cuda/rl_reward_clamp_controller.cu b/crates/ml-alpha/cuda/rl_reward_clamp_controller.cu
index dd43cade7..d9bfe7daa 100644
--- a/crates/ml-alpha/cuda/rl_reward_clamp_controller.cu
+++ b/crates/ml-alpha/cuda/rl_reward_clamp_controller.cu
@@ -224,51 +224,51 @@ extern "C" __global__ void rl_reward_clamp_controller(
         isv[RL_REWARD_CLAMP_RATIO_INDEX] = ratio_clamped;
     }
 
-    // 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.
-    //
-    // 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.
+    // Step 4 (G.2): WIN / LOSS clamp bounds remain STRUCTURAL — the
+    // G.2 feedback loop required BOTH clamp widening AND span widening.
+    // With clamp frozen here, only the atom span adapts (Step 5 below).
+    // Suppress unused warnings on diagnostic-only state.
     (void) margin;
-    (void) ema_new;
 
-    // ── C51 atom span — STRUCTURAL (G.2, 2026-05-24). ─────────────
+    // ── Step 5: C51 atom span adaptation from observed reward EMAs. ──
     //
-    // 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.
+    // G.2 disabled this because atom-span growth + clamp-bound growth
+    // created a positive feedback loop. With clamp bounds FROZEN (Step
+    // 4), the loop can't form — the clamp caps the reward magnitude
+    // regardless of atom span.
     //
-    // 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.
+    // The span slowly tracks the observed reward tail EMAs so Q's
+    // distributional resolution covers the ACTUAL reward range. Without
+    // this, rewards exceeding the static span project to edge atoms and
+    // Q loses magnitude discrimination (wr plateaus at ~0.46).
     //
-    // V_BOUND_FLOOR no longer used; keep the constant for any future
-    // re-introduction.
-    (void) V_BOUND_FLOOR;
-    (void) V_BOUND_EWMA_ALPHA;
+    // Floor at V_BOUND_FLOOR (1.0) preserves baseline resolution.
+    // Ceiling at clamp bounds (WIN=1.0, LOSS=3.0) prevents runaway.
+    // Slow EWMA (α=0.001, half-life ~700 steps) lets Q's atom mapping
+    // adapt gradually without whipsawing.
+    // Atom span anchors on the CLAMP bounds — the post-clamp reward
+    // range that Q's Bellman targets actually see. Pre-clamp EMAs
+    // (pos_ema ≈ 50) would blow atoms to [-50, +50] with Δ_z=5,
+    // destroying resolution. The clamp bounds (WIN, LOSS) are the
+    // structural ceiling on what rewards enter Q.
+    const float win_bound  = isv[RL_REWARD_CLAMP_WIN_INDEX];   // 1.0
+    const float loss_bound = isv[RL_REWARD_CLAMP_LOSS_INDEX];  // 3.0
+    {
+        const float v_max_prev = isv[RL_C51_V_MAX_INDEX];
+        const float v_max_target = fmaxf(V_BOUND_FLOOR, win_bound);
+        const float v_max_new = (v_max_prev == 0.0f)
+            ? v_max_target
+            : (1.0f - V_BOUND_EWMA_ALPHA) * v_max_prev
+              + V_BOUND_EWMA_ALPHA * v_max_target;
+        isv[RL_C51_V_MAX_INDEX] = fmaxf(V_BOUND_FLOOR, v_max_new);
+    }
+    {
+        const float v_min_prev = isv[RL_C51_V_MIN_INDEX];
+        const float v_min_target = fminf(-V_BOUND_FLOOR, -loss_bound);
+        const float v_min_new = (v_min_prev == 0.0f)
+            ? v_min_target
+            : (1.0f - V_BOUND_EWMA_ALPHA) * v_min_prev
+              + V_BOUND_EWMA_ALPHA * v_min_target;
+        isv[RL_C51_V_MIN_INDEX] = fminf(-V_BOUND_FLOOR, v_min_new);
+    }
 }