diff --git a/Makefile b/Makefile
index 9df5bae7..96780dd8 100644
--- a/Makefile
+++ b/Makefile
@@ -399,7 +399,7 @@ test-box-refactor: box-refactor
 	./larson_hakmem 10 8 128 1024 1 12345 4
 
 # Phase 4: Tiny Pool benchmarks (properly linked with hakmem)
-TINY_BENCH_OBJS_BASE = hakmem.o hakmem_config.o hakmem_tiny_config.o hakmem_ucb1.o hakmem_bigcache.o hakmem_pool.o hakmem_l25_pool.o hakmem_site_rules.o hakmem_tiny.o hakmem_tiny_superslab.o hakmem_smallmid.o hakmem_smallmid_superslab.o core/box/superslab_expansion_box.o core/box/integrity_box.o core/box/mailbox_box.o core/box/front_gate_box.o core/box/front_gate_classifier.o core/box/free_local_box.o core/box/free_remote_box.o core/box/free_publish_box.o core/box/capacity_box.o core/box/carve_push_box.o core/box/prewarm_box.o core/box/ss_hot_prewarm_box.o core/box/front_metrics_box.o core/box/bench_fast_box.o tiny_sticky.o tiny_remote.o tiny_publish.o tiny_debug_ring.o hakmem_tiny_magazine.o hakmem_tiny_stats.o hakmem_tiny_sfc.o hakmem_tiny_query.o hakmem_tiny_rss.o hakmem_tiny_registry.o hakmem_tiny_remote_target.o hakmem_tiny_bg_spill.o tiny_adaptive_sizing.o hakmem_mid_mt.o hakmem_super_registry.o hakmem_shared_pool.o hakmem_elo.o hakmem_batch.o hakmem_p2.o hakmem_sizeclass_dist.o hakmem_evo.o hakmem_debug.o hakmem_sys.o hakmem_whale.o hakmem_policy.o hakmem_ace.o hakmem_ace_stats.o hakmem_prof.o hakmem_learner.o hakmem_size_hist.o hakmem_learn_log.o hakmem_syscall.o hakmem_ace_metrics.o hakmem_ace_ucb1.o hakmem_ace_controller.o tiny_fastcache.o core/link_stubs.o core/tiny_failfast.o
+TINY_BENCH_OBJS_BASE = hakmem.o hakmem_config.o hakmem_tiny_config.o hakmem_ucb1.o hakmem_bigcache.o hakmem_pool.o hakmem_l25_pool.o hakmem_site_rules.o hakmem_tiny.o hakmem_tiny_superslab.o hakmem_smallmid.o hakmem_smallmid_superslab.o core/box/superslab_expansion_box.o core/box/integrity_box.o core/box/mailbox_box.o core/box/front_gate_box.o core/box/front_gate_classifier.o core/box/free_local_box.o core/box/free_remote_box.o core/box/free_publish_box.o core/box/capacity_box.o core/box/carve_push_box.o core/box/prewarm_box.o core/box/ss_hot_prewarm_box.o core/box/front_metrics_box.o core/box/bench_fast_box.o core/front/tiny_ring_cache.o tiny_sticky.o tiny_remote.o tiny_publish.o tiny_debug_ring.o hakmem_tiny_magazine.o hakmem_tiny_stats.o hakmem_tiny_sfc.o hakmem_tiny_query.o hakmem_tiny_rss.o hakmem_tiny_registry.o hakmem_tiny_remote_target.o hakmem_tiny_bg_spill.o tiny_adaptive_sizing.o hakmem_mid_mt.o hakmem_super_registry.o hakmem_shared_pool.o hakmem_elo.o hakmem_batch.o hakmem_p2.o hakmem_sizeclass_dist.o hakmem_evo.o hakmem_debug.o hakmem_sys.o hakmem_whale.o hakmem_policy.o hakmem_ace.o hakmem_ace_stats.o hakmem_prof.o hakmem_learner.o hakmem_size_hist.o hakmem_learn_log.o hakmem_syscall.o hakmem_ace_metrics.o hakmem_ace_ucb1.o hakmem_ace_controller.o tiny_fastcache.o core/link_stubs.o core/tiny_failfast.o
 TINY_BENCH_OBJS = $(TINY_BENCH_OBJS_BASE)
 ifeq ($(POOL_TLS_PHASE1),1)
 TINY_BENCH_OBJS += pool_tls.o pool_refill.o core/pool_tls_arena.o pool_tls_registry.o pool_tls_remote.o
diff --git a/core/box/front_metrics_box.d b/core/box/front_metrics_box.d
new file mode 100644
index 00000000..8da329c3
--- /dev/null
+++ b/core/box/front_metrics_box.d
@@ -0,0 +1,4 @@
+core/box/front_metrics_box.o: core/box/front_metrics_box.c \
+ core/box/front_metrics_box.h core/box/../hakmem_tiny_stats_api.h
+core/box/front_metrics_box.h:
+core/box/../hakmem_tiny_stats_api.h:
diff --git a/core/box/ss_hot_prewarm_box.d b/core/box/ss_hot_prewarm_box.d
new file mode 100644
index 00000000..58d67ec7
--- /dev/null
+++ b/core/box/ss_hot_prewarm_box.d
@@ -0,0 +1,12 @@
+core/box/ss_hot_prewarm_box.o: core/box/ss_hot_prewarm_box.c \
+ core/box/../hakmem_tiny.h core/box/../hakmem_build_flags.h \
+ core/box/../hakmem_trace.h core/box/../hakmem_tiny_mini_mag.h \
+ core/box/../hakmem_tiny_config.h core/box/ss_hot_prewarm_box.h \
+ core/box/prewarm_box.h
+core/box/../hakmem_tiny.h:
+core/box/../hakmem_build_flags.h:
+core/box/../hakmem_trace.h:
+core/box/../hakmem_tiny_mini_mag.h:
+core/box/../hakmem_tiny_config.h:
+core/box/ss_hot_prewarm_box.h:
+core/box/prewarm_box.h:
diff --git a/core/front/tiny_ring_cache.d b/core/front/tiny_ring_cache.d
new file mode 100644
index 00000000..5edef862
--- /dev/null
+++ b/core/front/tiny_ring_cache.d
@@ -0,0 +1,4 @@
+core/front/tiny_ring_cache.o: core/front/tiny_ring_cache.c \
+ core/front/tiny_ring_cache.h core/front/../hakmem_build_flags.h
+core/front/tiny_ring_cache.h:
+core/front/../hakmem_build_flags.h:
diff --git a/core/front/tiny_ring_cache.h b/core/front/tiny_ring_cache.h
index 9446a22a..37c4533f 100644
--- a/core/front/tiny_ring_cache.h
+++ b/core/front/tiny_ring_cache.h
@@ -130,6 +130,14 @@ static inline int ring_cascade_enabled(void) {
     return g_enable;
 }
 
+// ============================================================================
+// Init/Shutdown Forward Declarations (needed by pop/push)
+// ============================================================================
+
+void ring_cache_init(void);
+void ring_cache_shutdown(void);
+void ring_cache_print_stats(void);
+
 // ============================================================================
 // Ultra-Fast Pop/Push (1-2 instructions)
 // ============================================================================
@@ -137,8 +145,19 @@ static inline int ring_cascade_enabled(void) {
 // Pop from ring (alloc fast path)
 // Returns: BASE pointer (caller must convert to USER with +1)
 static inline void* ring_cache_pop(int class_idx) {
+    // Fast path: Ring disabled or wrong class → return NULL immediately
+    if (__builtin_expect(!ring_cache_enabled(), 0)) return NULL;
+    if (__builtin_expect(class_idx != 2 && class_idx != 3, 0)) return NULL;
+
     TinyRingCache* ring = (class_idx == 2) ? &g_ring_cache_c2 : &g_ring_cache_c3;
 
+    // Lazy init check (once per thread)
+    if (__builtin_expect(ring->slots == NULL, 0)) {
+        ring_cache_init();  // First call in this thread
+        // Re-check after init (may fail if allocation failed)
+        if (ring->slots == NULL) return NULL;
+    }
+
     // Empty check
     if (__builtin_expect(ring->head == ring->tail, 0)) {
         return NULL;  // Empty
@@ -155,8 +174,19 @@ static inline void* ring_cache_pop(int class_idx) {
 // Input: BASE pointer (caller must pass BASE, not USER)
 // Returns: 1=SUCCESS, 0=FULL
 static inline int ring_cache_push(int class_idx, void* base) {
+    // Fast path: Ring disabled or wrong class → return 0 (not handled)
+    if (__builtin_expect(!ring_cache_enabled(), 0)) return 0;
+    if (__builtin_expect(class_idx != 2 && class_idx != 3, 0)) return 0;
+
     TinyRingCache* ring = (class_idx == 2) ? &g_ring_cache_c2 : &g_ring_cache_c3;
 
+    // Lazy init check (once per thread)
+    if (__builtin_expect(ring->slots == NULL, 0)) {
+        ring_cache_init();  // First call in this thread
+        // Re-check after init (may fail if allocation failed)
+        if (ring->slots == NULL) return 0;
+    }
+
     uint16_t next_tail = (ring->tail + 1) & ring->mask;
 
     // Full check (leave 1 slot empty to distinguish full/empty)
@@ -178,12 +208,4 @@ static inline int ring_cache_push(int class_idx, void* base) {
 // Forward declaration (defined in tiny_ring_cache.c)
 int ring_refill_from_sll(int class_idx, int target_count);
 
-// ============================================================================
-// Init/Shutdown (called from hakmem_tiny.c)
-// ============================================================================
-
-void ring_cache_init(void);
-void ring_cache_shutdown(void);
-void ring_cache_print_stats(void);
-
 #endif // HAK_FRONT_TINY_RING_CACHE_H
diff --git a/core/hakmem.c b/core/hakmem.c
index 19e18de5..b4761e23 100644
--- a/core/hakmem.c
+++ b/core/hakmem.c
@@ -31,6 +31,7 @@
 #include "hakmem_syscall.h"     // NEW Phase 6.X P0 FIX: Box 3 (dlsym direct libc)
 #include "hakmem_ace_controller.h"  // NEW Phase ACE: Adaptive Control Engine
 #include "hakmem_ace_metrics.h"     // NEW Phase ACE: Metrics tracking (inline helpers)
+#include "box/bench_fast_box.h"     // NEW Phase 20-2: BenchFast Mode (structural ceiling measurement)
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
diff --git a/core/hakmem_tiny.d b/core/hakmem_tiny.d
index 6d91f4de..ae956676 100644
--- a/core/hakmem_tiny.d
+++ b/core/hakmem_tiny.d
@@ -44,8 +44,9 @@ core/hakmem_tiny.o: core/hakmem_tiny.c core/hakmem_tiny.h \
  core/tiny_atomic.h core/tiny_alloc_fast.inc.h \
  core/tiny_alloc_fast_sfc.inc.h core/hakmem_tiny_fastcache.inc.h \
  core/front/tiny_front_c23.h core/front/../hakmem_build_flags.h \
- core/front/tiny_heap_v2.h core/front/tiny_ultra_hot.h \
- core/front/../box/tls_sll_box.h core/tiny_alloc_fast_inline.h \
+ core/front/tiny_ring_cache.h core/front/tiny_heap_v2.h \
+ core/front/tiny_ultra_hot.h core/front/../box/tls_sll_box.h \
+ core/box/front_metrics_box.h core/tiny_alloc_fast_inline.h \
  core/tiny_free_fast.inc.h core/hakmem_tiny_alloc.inc \
  core/hakmem_tiny_slow.inc core/hakmem_tiny_free.inc \
  core/box/free_publish_box.h core/mid_tcache.h \
@@ -153,9 +154,11 @@ core/tiny_alloc_fast_sfc.inc.h:
 core/hakmem_tiny_fastcache.inc.h:
 core/front/tiny_front_c23.h:
 core/front/../hakmem_build_flags.h:
+core/front/tiny_ring_cache.h:
 core/front/tiny_heap_v2.h:
 core/front/tiny_ultra_hot.h:
 core/front/../box/tls_sll_box.h:
+core/box/front_metrics_box.h:
 core/tiny_alloc_fast_inline.h:
 core/tiny_free_fast.inc.h:
 core/hakmem_tiny_alloc.inc:
diff --git a/core/tiny_alloc_fast.inc.h b/core/tiny_alloc_fast.inc.h
index 472ae6cc..41500a20 100644
--- a/core/tiny_alloc_fast.inc.h
+++ b/core/tiny_alloc_fast.inc.h
@@ -28,6 +28,7 @@
 #include "hakmem_tiny_integrity.h"     // PRIORITY 1-4: Corruption detection
 #ifdef HAKMEM_TINY_HEADER_CLASSIDX
 #include "front/tiny_front_c23.h"      // Phase B: Ultra-simple C2/C3 front
+#include "front/tiny_ring_cache.h"     // Phase 21-1: Ring cache (C2/C3 array-based TLS cache)
 #include "front/tiny_heap_v2.h"        // Phase 13-A: TinyHeapV2 magazine front
 #include "front/tiny_ultra_hot.h"      // Phase 14: TinyUltraHot C1/C2 ultra-fast path
 #endif
@@ -605,6 +606,19 @@ static inline void* tiny_alloc_fast(size_t size) {
     }
 #endif
 
+    // Phase 21-1: Ring Cache (C2/C3 only) - Array-based TLS cache
+    // ENV-gated: HAKMEM_TINY_HOT_RING_ENABLE=1
+    // Target: +15-20% (54.4M → 62-65M ops/s) by eliminating pointer chasing
+    // Design: Ring (L0) → SLL (L1) → SuperSlab (L2) cascade hierarchy
+    if (class_idx == 2 || class_idx == 3) {
+        void* base = ring_cache_pop(class_idx);
+        if (base) {
+            // Ring hit - return USER pointer (BASE + 1)
+            HAK_RET_ALLOC(class_idx, base);
+        }
+        // Ring miss - fall through to existing path (TLS SLL/UltraHot/HeapV2)
+    }
+
     // Phase 14-C: TinyUltraHot Borrowing Design (正史から借りる設計)
     // ENV-gated: HAKMEM_TINY_ULTRA_HOT=1 (internal control)
     // Phase 19-4: HAKMEM_TINY_FRONT_ENABLE_ULTRAHOT=1 to enable (DEFAULT: OFF for +12.9% perf)
diff --git a/core/tiny_free_fast_v2.inc.h b/core/tiny_free_fast_v2.inc.h
index 73c52d1a..c4194c37 100644
--- a/core/tiny_free_fast_v2.inc.h
+++ b/core/tiny_free_fast_v2.inc.h
@@ -23,6 +23,7 @@
 #include "hakmem_tiny_integrity.h"  // PRIORITY 1-4: Corruption detection
 #include "front/tiny_heap_v2.h"     // Phase 13-B: TinyHeapV2 magazine supply
 #include "front/tiny_ultra_hot.h"   // Phase 14: TinyUltraHot C1/C2 ultra-fast path
+#include "front/tiny_ring_cache.h"  // Phase 21-1: Ring cache (C2/C3 array-based TLS cache)
 
 // Phase 7: Header-based ultra-fast free
 #if HAKMEM_TINY_HEADER_CLASSIDX
@@ -136,6 +137,18 @@ static inline int hak_tiny_free_fast_v2(void* ptr) {
     // → 正史（TLS SLL）の在庫を正しく保つ
     // → UltraHot refill は alloc 側で TLS SLL から借りる
 
+    // Phase 21-1: Ring Cache (C2/C3 only) - Array-based TLS cache
+    // ENV-gated: HAKMEM_TINY_HOT_RING_ENABLE=1
+    // Target: +15-20% (54.4M → 62-65M ops/s) by eliminating pointer chasing
+    // Design: Ring (L0) → SLL (L1) → SuperSlab (L2) cascade hierarchy
+    if (class_idx == 2 || class_idx == 3) {
+        if (ring_cache_push(class_idx, base)) {
+            // Ring push success - done!
+            return 1;
+        }
+        // Ring full - fall through to existing path (TLS SLL/HeapV2)
+    }
+
     // Phase 13-B: TinyHeapV2 magazine supply (C0-C3 only)
     // Two supply modes (controlled by HAKMEM_TINY_HEAP_V2_LEFTOVER_MODE):
     //   Mode 0 (default): L0 gets blocks first ("stealing" design)
diff --git a/hakmem.d b/hakmem.d
index 624751bd..4019527f 100644
--- a/hakmem.d
+++ b/hakmem.d
@@ -14,9 +14,10 @@ hakmem.o: core/hakmem.c core/hakmem.h core/hakmem_build_flags.h \
  core/hakmem_elo.h core/hakmem_ace_stats.h core/hakmem_batch.h \
  core/hakmem_evo.h core/hakmem_debug.h core/hakmem_prof.h \
  core/hakmem_syscall.h core/hakmem_ace_controller.h \
- core/hakmem_ace_metrics.h core/hakmem_ace_ucb1.h core/ptr_trace.h \
- core/box/hak_exit_debug.inc.h core/box/hak_kpi_util.inc.h \
- core/box/hak_core_init.inc.h core/hakmem_phase7_config.h \
+ core/hakmem_ace_metrics.h core/hakmem_ace_ucb1.h \
+ core/box/bench_fast_box.h core/ptr_trace.h core/box/hak_exit_debug.inc.h \
+ core/box/hak_kpi_util.inc.h core/box/hak_core_init.inc.h \
+ core/hakmem_phase7_config.h core/box/ss_hot_prewarm_box.h \
  core/box/hak_alloc_api.inc.h core/box/../hakmem_tiny.h \
  core/box/../hakmem_smallmid.h core/box/hak_free_api.inc.h \
  core/hakmem_tiny_superslab.h core/box/../tiny_free_fast_v2.inc.h \
@@ -33,7 +34,9 @@ hakmem.o: core/hakmem.c core/hakmem.h core/hakmem_build_flags.h \
  core/box/../box/tls_sll_box.h core/box/../box/free_local_box.h \
  core/box/../hakmem_tiny_integrity.h core/box/../front/tiny_heap_v2.h \
  core/box/../front/../hakmem_tiny.h core/box/../front/tiny_ultra_hot.h \
- core/box/../front/../box/tls_sll_box.h core/box/front_gate_v2.h \
+ core/box/../front/../box/tls_sll_box.h \
+ core/box/../front/tiny_ring_cache.h \
+ core/box/../front/../hakmem_build_flags.h core/box/front_gate_v2.h \
  core/box/external_guard_box.h core/box/hak_wrappers.inc.h \
  core/box/front_gate_classifier.h
 core/hakmem.h:
@@ -78,11 +81,13 @@ core/hakmem_syscall.h:
 core/hakmem_ace_controller.h:
 core/hakmem_ace_metrics.h:
 core/hakmem_ace_ucb1.h:
+core/box/bench_fast_box.h:
 core/ptr_trace.h:
 core/box/hak_exit_debug.inc.h:
 core/box/hak_kpi_util.inc.h:
 core/box/hak_core_init.inc.h:
 core/hakmem_phase7_config.h:
+core/box/ss_hot_prewarm_box.h:
 core/box/hak_alloc_api.inc.h:
 core/box/../hakmem_tiny.h:
 core/box/../hakmem_smallmid.h:
@@ -112,6 +117,8 @@ core/box/../front/tiny_heap_v2.h:
 core/box/../front/../hakmem_tiny.h:
 core/box/../front/tiny_ultra_hot.h:
 core/box/../front/../box/tls_sll_box.h:
+core/box/../front/tiny_ring_cache.h:
+core/box/../front/../hakmem_build_flags.h:
 core/box/front_gate_v2.h:
 core/box/external_guard_box.h:
 core/box/hak_wrappers.inc.h:
diff --git a/hakmem_smallmid_superslab.d b/hakmem_smallmid_superslab.d
new file mode 100644
index 00000000..9aded8ff
--- /dev/null
+++ b/hakmem_smallmid_superslab.d
@@ -0,0 +1,4 @@
+hakmem_smallmid_superslab.o: core/hakmem_smallmid_superslab.c \
+ core/hakmem_smallmid_superslab.h core/hakmem_smallmid.h
+core/hakmem_smallmid_superslab.h:
+core/hakmem_smallmid.h: