diff --git a/CURRENT_TASK.md b/CURRENT_TASK.md
index b149cac4..357dfa94 100644
--- a/CURRENT_TASK.md
+++ b/CURRENT_TASK.md
@@ -244,9 +244,91 @@ ENV変数でTiny/Mid境界を動的調整可能にする機能を追加：
 - **ギャップ解消**: Tiny (6M) と Mid (?) の間を埋める
 - **Box 理論的健全性**: 境界明確、一方向依存、A/B 可能
 
-### 5.6 実装状況
+### 5.6 Phase 17-1 実装結果（2025-11-16完了）
 
-🚧 **IN PROGRESS** - 設計方針確定、実装開始準備中
+**戦略**: TLS Frontend Cache Only（Tiny Backend 委譲）
+- サイズクラス: 5 → 3 に削減（256B/512B/1KB のみ）
+- Backend: Tiny C5/C6/C7 に委譲、Header 変換（0xa0 → 0xb0）
+- TLS 容量: 控えめ（32/24/16 blocks）
+
+**実装ファイル**:
+- `core/hakmem_smallmid.h/c`: TLS freelist + backend delegation
+- `core/hakmem_tiny.c`: `tiny_get_max_size()` 自動調整（Small-Mid ON 時に C0-C5 に制限）
+- `core/box/hak_alloc_api.inc.h`: Small-Mid を Tiny より前に配置（routing 順序）
+
+### 5.7 A/B Benchmark Results（Phase 17-1）
+
+| Size | Config A (OFF) | Config B (ON) | 変化率 | 目標達成 |
+|------|----------------|---------------|--------|----------|
+| **256B** | 5.87M ops/s | 6.06M ops/s | **+3.3%** | ❌ |
+| **512B** | 6.02M ops/s | 5.91M ops/s | **-1.9%** | ❌ |
+| **1024B** | 5.58M ops/s | 5.54M ops/s | **-0.6%** | ❌ |
+| **総合** | 5.82M ops/s | 5.84M ops/s | **+0.3%** | ❌ |
+
+### 5.8 Phase 17-1 の成果と学び
+
+✅ **成功点**:
+1. **層の分離達成** - Small-Mid と Tiny が cleanly 共存
+2. **オーバーヘッド最小** - ±0.3% = 測定誤差内（clean な実装）
+3. **Routing 順序修正** - Small-Mid → Tiny の順で正しく動作
+4. **Auto-adjust 機能** - Small-Mid ON 時に Tiny が自動的に C0-C5 に制限
+5. **基盤完成** - これから最適化で改善のみ！
+
+❌ **失敗点**:
+- **性能改善なし** (+0.3% は目標の 2-4x に遠く及ばず)
+
+**根本原因分析**:
+1. **Delegation オーバーヘッド = TLS 節約分**
+   - Small-Mid TLS alloc: ~3-5 命令
+   - Tiny backend delegation: ~3-5 命令
+   - Header 変換 (0xa0 → 0xb0): ~2 命令
+   - **正味利益: ~0命令** (オーバーヘッドが利益を相殺)
+
+2. **Backend が1ブロックずつ呼ばれる**
+   - Small-Mid は 1:1 で Tiny に delegate (batching なし)
+   - `hak_tiny_alloc()` / `hak_tiny_free()` 呼び出し削減なし
+   - 期待: Batch refills → 実際: Pass-through
+
+**教訓**:
+- **Frontend-only アプローチは効果なし** - Backend delegation コストが大きすぎる
+- **次は専用 Backend が必須** - Tiny から独立した Small-Mid SuperSlab pool 必要
+
+### 5.9 次のステップ: Phase 17-2（専用 Backend）
+
+**戦略**: Small-Mid 専用 SuperSlab Backend（Tiny から完全分離）
+
+**設計**:
+1. **専用 SuperSlab pool** (Tiny と分離)
+   - Tiny delegation なし
+   - Header 変換オーバーヘッドなし
+   - 直接 0xb0 header 書き込み
+
+2. **TLS refill batching**
+   - 1回のrefillで 8-16 blocks 取得
+   - SuperSlab lookup コストを償却
+   - 目標: 50-70% frontend hit rate
+
+3. **最適化 free path**
+   - 直接 0xb0 header 読み取り → Small-Mid TLS push
+   - Cached blocks に backend round-trip なし
+
+**期待性能**:
+- **Frontend hits**: 1-2 命令 (TLS pop/push)
+- **Backend misses**: 5-8 命令 (batch refill)
+- **加重平均** (60% hit): 0.6×2 + 0.4×6 = **~4命令**
+- **現在の Tiny path**: 8-12 命令
+- **期待利益**: 50-67% 削減 → **2-3x throughput** ✅
+
+**目標メトリクス**:
+- 256B: 5.87M → 12-15M ops/s (2.0-2.6x)
+- 512B: 6.02M → 12-15M ops/s (2.0-2.5x)
+- 1024B: 5.58M → 11-14M ops/s (2.0-2.5x)
+
+**実装優先順位**:
+1. Phase 17-2.1: Dedicated SuperSlab backend (Tiny から分離)
+2. Phase 17-2.2: TLS batch refill (8-16 blocks)
+3. Phase 17-2.3: Optimized 0xb0 header fast path
+4. Phase 17-2.4: Benchmark validation (目標: 12-18M ops/s)
 
 ---
 
@@ -291,43 +373,64 @@ ENV変数でTiny/Mid境界を動的調整可能にする機能を追加：
 
 ---
 
-## 7. Claude Code 君向け TODO（Phase 17 実装リスト）
+## 7. Claude Code 君向け TODO（Phase 17-2 実装リスト）
 
-### 7.1 Phase 17: Small-Mid Box 実装 🚧
+### 7.1 Phase 17-1: TLS Frontend Cache ✅ 完了（2025-11-16）
 
-1. **ヘッダー作成** (`core/hakmem_smallmid.h`)
-   - 5 size classes 定義 (256B/512B/1KB/2KB/4KB)
+1. ✅ **ヘッダー作成** (`core/hakmem_smallmid.h`)
+   - 3 size classes 定義 (256B/512B/1KB)
    - TLS freelist 構造体定義
    - size → class マッピング関数
-   - Fast alloc/free API 宣言
 
-2. **専用 SuperSlab バックエンド** (`core/hakmem_smallmid_superslab.c`)
-   - Small-Mid 専用 SuperSlab プール（Tiny と完全分離）
-   - スパン予約・解放ロジック
-   - refill 関数
+2. ✅ **Backend delegation 実装** (`core/hakmem_smallmid.c`)
+   - Tiny C5/C6/C7 に委譲
+   - Header 変換（0xa0 → 0xb0）
+   - TLS SLL pop/push
 
-3. **Fast alloc/free 実装** (`core/smallmid_alloc_fast.inc.h`, `core/hakmem_smallmid.c`)
-   - Header-based fast free (Phase 7 技術流用)
-   - TLS SLL pop/push (Tiny と同じ構造)
-   - Bump allocation fallback
+3. ✅ **Auto-adjust 機能** (`core/hakmem_tiny.c`)
+   - Small-Mid ON 時に Tiny を C0-C5 に自動制限
+   - `tiny_get_max_size()` 動的調整
+
+4. ✅ **ルーティング統合** (`hak_alloc_api.inc.h`)
+   - Small-Mid を Tiny より前に配置
    - ENV 制御: `HAKMEM_SMALLMID_ENABLE=1`
 
-4. **ルーティング統合** (`hak_alloc_api.inc.h`)
-   - Small-Mid 層の追加（256B-4KB）
-   - ENV で ON/OFF 切り替え
+5. ✅ **A/B ベンチマーク**
+   - Config A/B 実施（3 runs each）
+   - 結果: ±0.3% (性能改善なし)
+   - 教訓: Frontend-only は効果なし、専用 Backend 必須
 
-5. **A/B ベンチマーク**
-   - Config A: Small-Mid OFF（現状）
-   - Config B: Small-Mid ON（新実装）
-   - 256B/512B/1KB/2KB/4KB で性能測定
+### 7.2 Phase 17-2: Dedicated Backend 🚧 次のタスク
 
-6. **ドキュメント作成**
-   - `PHASE17_SMALLMID_BOX_DESIGN.md` - 設計書
-   - `PHASE17_SMALLMID_AB_RESULTS.md` - A/B テスト結果
+**目標**: Small-Mid 専用 SuperSlab backend で 2-3x 性能改善
 
-### 7.2 その他タスク（Phase 17 後）
+1. **専用 SuperSlab backend** (`core/hakmem_smallmid_superslab.c`)
+   - Small-Mid 専用 SuperSlab プール（Tiny と完全分離）
+   - Slab metadata 構造定義
+   - スパン予約・解放ロジック
 
-1. **Phase 16 結果の詳細分析**
+2. **TLS batch refill** (`core/smallmid_refill_box.c`)
+   - 1回のrefillで 8-16 blocks 取得
+   - SuperSlab lookup コストを償却
+   - Refill 失敗時の fallback 処理
+
+3. **Optimized alloc/free path** (`core/hakmem_smallmid.c`)
+   - 直接 0xb0 header 書き込み（Tiny delegation なし）
+   - TLS hit: 1-2 命令
+   - TLS miss: batch refill (5-8 命令)
+
+4. **A/B ベンチマーク**
+   - Config A: Phase 17-2 OFF（現状 5.82M ops/s）
+   - Config B: Phase 17-2 ON（目標 12-15M ops/s）
+   - 256B/512B/1KB で性能測定
+
+5. **ドキュメント作成**
+   - `PHASE17_2_SMALLMID_BACKEND_DESIGN.md` - 設計書
+   - `PHASE17_2_AB_RESULTS.md` - A/B テスト結果
+
+### 7.3 その他タスク（Phase 17-2 後）
+
+1. **Phase 16/17-1 結果の詳細分析**
    - ✅ 完了 - CURRENT_TASK.md に記録済み
 
 2. **C2/C3 UltraHot のコード掃除**
@@ -342,11 +445,17 @@ ENV変数でTiny/Mid境界を動的調整可能にする機能を追加：
 
 ---
 
-## 8. Phase 17 実装ログ（進行中）
+## 8. Phase 17 実装ログ
 
-### 2025-11-16
+### 2025-11-16（Phase 17-1 完了）
 - ✅ Phase 16 完了・A/B テスト結果分析
 - ✅ ChatGPT 先生の Small-Mid Box 提案レビュー
-- ✅ CURRENT_TASK.md 更新（Phase 17 設計方針確定）
-- 🚧 次: `core/hakmem_smallmid.h` ヘッダー作成開始
+- ✅ Phase 17-1 実装完了（TLS Frontend + Tiny Backend delegation）
+  - `core/hakmem_smallmid.h/c`: TLS freelist + backend delegation
+  - `core/hakmem_tiny.c`: Auto-adjust 機能
+  - `core/box/hak_alloc_api.inc.h`: Routing 順序修正
+- ✅ A/B ベンチマーク完了（結果: ±0.3%, 性能改善なし）
+- ✅ 根本原因分析: Delegation overhead = TLS savings (正味利益ゼロ)
+- ✅ CURRENT_TASK.md 更新（Phase 17-1 結果 + Phase 17-2 計画）
+- 🚧 次: Phase 17-2 専用 Backend 実装開始
 
diff --git a/Makefile b/Makefile
index 9092b642..34cf067e 100644
--- a/Makefile
+++ b/Makefile
@@ -190,12 +190,12 @@ LDFLAGS += $(EXTRA_LDFLAGS)
 
 # Targets
 TARGET = test_hakmem
-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 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/box/superslab_expansion_box.o core/box/integrity_box.o core/box/free_local_box.o core/box/free_remote_box.o core/box/free_publish_box.o core/box/mailbox_box.o core/box/front_gate_box.o core/box/front_gate_classifier.o core/box/capacity_box.o core/box/carve_push_box.o core/box/prewarm_box.o core/link_stubs.o core/tiny_failfast.o test_hakmem.o
+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 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/box/superslab_expansion_box.o core/box/integrity_box.o core/box/free_local_box.o core/box/free_remote_box.o core/box/free_publish_box.o core/box/mailbox_box.o core/box/front_gate_box.o core/box/front_gate_classifier.o core/box/capacity_box.o core/box/carve_push_box.o core/box/prewarm_box.o core/link_stubs.o core/tiny_failfast.o test_hakmem.o
 OBJS = $(OBJS_BASE)
 
 # Shared library
 SHARED_LIB = libhakmem.so
-SHARED_OBJS = hakmem_shared.o hakmem_config_shared.o hakmem_tiny_config_shared.o hakmem_ucb1_shared.o hakmem_bigcache_shared.o hakmem_pool_shared.o hakmem_l25_pool_shared.o hakmem_site_rules_shared.o hakmem_tiny_shared.o hakmem_tiny_superslab_shared.o core/box/superslab_expansion_box_shared.o core/box/integrity_box_shared.o core/box/mailbox_box_shared.o core/box/front_gate_box_shared.o core/box/free_local_box_shared.o core/box/free_remote_box_shared.o core/box/free_publish_box_shared.o core/box/capacity_box_shared.o core/box/carve_push_box_shared.o core/box/prewarm_box_shared.o tiny_sticky_shared.o tiny_remote_shared.o tiny_publish_shared.o tiny_debug_ring_shared.o hakmem_tiny_magazine_shared.o hakmem_tiny_stats_shared.o hakmem_tiny_sfc_shared.o hakmem_tiny_query_shared.o hakmem_tiny_rss_shared.o hakmem_tiny_registry_shared.o hakmem_tiny_remote_target_shared.o hakmem_tiny_bg_spill_shared.o tiny_adaptive_sizing_shared.o hakmem_mid_mt_shared.o hakmem_super_registry_shared.o hakmem_elo_shared.o hakmem_batch_shared.o hakmem_p2_shared.o hakmem_sizeclass_dist_shared.o hakmem_evo_shared.o hakmem_debug_shared.o hakmem_sys_shared.o hakmem_whale_shared.o hakmem_policy_shared.o hakmem_ace_shared.o hakmem_ace_stats_shared.o hakmem_ace_controller_shared.o hakmem_ace_metrics_shared.o hakmem_ace_ucb1_shared.o hakmem_prof_shared.o hakmem_learner_shared.o hakmem_size_hist_shared.o hakmem_learn_log_shared.o hakmem_syscall_shared.o tiny_fastcache_shared.o
+SHARED_OBJS = hakmem_shared.o hakmem_config_shared.o hakmem_tiny_config_shared.o hakmem_ucb1_shared.o hakmem_bigcache_shared.o hakmem_pool_shared.o hakmem_l25_pool_shared.o hakmem_site_rules_shared.o hakmem_tiny_shared.o hakmem_tiny_superslab_shared.o hakmem_smallmid_shared.o core/box/superslab_expansion_box_shared.o core/box/integrity_box_shared.o core/box/mailbox_box_shared.o core/box/front_gate_box_shared.o core/box/free_local_box_shared.o core/box/free_remote_box_shared.o core/box/free_publish_box_shared.o core/box/capacity_box_shared.o core/box/carve_push_box_shared.o core/box/prewarm_box_shared.o tiny_sticky_shared.o tiny_remote_shared.o tiny_publish_shared.o tiny_debug_ring_shared.o hakmem_tiny_magazine_shared.o hakmem_tiny_stats_shared.o hakmem_tiny_sfc_shared.o hakmem_tiny_query_shared.o hakmem_tiny_rss_shared.o hakmem_tiny_registry_shared.o hakmem_tiny_remote_target_shared.o hakmem_tiny_bg_spill_shared.o tiny_adaptive_sizing_shared.o hakmem_mid_mt_shared.o hakmem_super_registry_shared.o hakmem_elo_shared.o hakmem_batch_shared.o hakmem_p2_shared.o hakmem_sizeclass_dist_shared.o hakmem_evo_shared.o hakmem_debug_shared.o hakmem_sys_shared.o hakmem_whale_shared.o hakmem_policy_shared.o hakmem_ace_shared.o hakmem_ace_stats_shared.o hakmem_ace_controller_shared.o hakmem_ace_metrics_shared.o hakmem_ace_ucb1_shared.o hakmem_prof_shared.o hakmem_learner_shared.o hakmem_size_hist_shared.o hakmem_learn_log_shared.o hakmem_syscall_shared.o tiny_fastcache_shared.o
 
 # Pool TLS Phase 1 (enable with POOL_TLS_PHASE1=1)
 ifeq ($(POOL_TLS_PHASE1),1)
@@ -222,7 +222,7 @@ endif
 # Benchmark targets
 BENCH_HAKMEM = bench_allocators_hakmem
 BENCH_SYSTEM = bench_allocators_system
-BENCH_HAKMEM_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 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_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/box/superslab_expansion_box.o core/box/integrity_box.o core/box/free_local_box.o core/box/free_remote_box.o core/box/free_publish_box.o core/box/mailbox_box.o core/box/front_gate_box.o core/box/front_gate_classifier.o core/box/capacity_box.o core/box/carve_push_box.o core/box/prewarm_box.o core/link_stubs.o core/tiny_failfast.o bench_allocators_hakmem.o
+BENCH_HAKMEM_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 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_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/box/superslab_expansion_box.o core/box/integrity_box.o core/box/free_local_box.o core/box/free_remote_box.o core/box/free_publish_box.o core/box/mailbox_box.o core/box/front_gate_box.o core/box/front_gate_classifier.o core/box/capacity_box.o core/box/carve_push_box.o core/box/prewarm_box.o core/link_stubs.o core/tiny_failfast.o bench_allocators_hakmem.o
 BENCH_HAKMEM_OBJS = $(BENCH_HAKMEM_OBJS_BASE)
 ifeq ($(POOL_TLS_PHASE1),1)
 BENCH_HAKMEM_OBJS += pool_tls.o pool_refill.o pool_tls_arena.o pool_tls_registry.o pool_tls_remote.o
@@ -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 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 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 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 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/hak_alloc_api.inc.h b/core/box/hak_alloc_api.inc.h
index 74acc37e..20e38cfe 100644
--- a/core/box/hak_alloc_api.inc.h
+++ b/core/box/hak_alloc_api.inc.h
@@ -2,7 +2,8 @@
 #ifndef HAK_ALLOC_API_INC_H
 #define HAK_ALLOC_API_INC_H
 
-#include "../hakmem_tiny.h"  // For tiny_get_max_size() (Phase 16)
+#include "../hakmem_tiny.h"     // For tiny_get_max_size() (Phase 16)
+#include "../hakmem_smallmid.h" // For Small-Mid Front Box (Phase 17-1)
 
 #ifdef HAKMEM_POOL_TLS_PHASE1
 #include "../pool_tls.h"
@@ -31,8 +32,29 @@ inline void* hak_alloc_at(size_t size, hak_callsite_t site) {
 
     uintptr_t site_id = (uintptr_t)site;
 
+    // Phase 17-1: Small-Mid Front Box (256B-1KB) - TRY FIRST!
+    // Strategy: Thin TLS cache layer, no backend (falls through on miss)
+    // ENV: HAKMEM_SMALLMID_ENABLE=1 to enable (default: OFF)
+    // CRITICAL: Must come BEFORE Tiny to avoid routing conflict
+    // When enabled, auto-adjusts Tiny to C0-C5 (0-255B only)
+    if (smallmid_is_enabled() && smallmid_is_in_range(size)) {
+#if HAKMEM_DEBUG_TIMING
+        HKM_TIME_START(t_smallmid);
+#endif
+        void* sm_ptr = smallmid_alloc(size);
+#if HAKMEM_DEBUG_TIMING
+        HKM_TIME_END(HKM_CAT_TINY_ALLOC, t_smallmid);
+#endif
+        if (sm_ptr) {
+            hkm_ace_track_alloc();
+            return sm_ptr;
+        }
+        // TLS miss: Fall through to Mid/ACE (Tiny skipped due to auto-adjust)
+    }
+
     // Phase 16: Dynamic Tiny max size (ENV: HAKMEM_TINY_MAX_CLASS)
-    // Default: 1023B (C0-C7), can be reduced to 255B (C0-C5) to delegate 512/1024B to Mid
+    // Default: 1023B (C0-C7), reduced to 255B (C0-C5) when Small-Mid enabled
+    // Phase 17-1: Auto-adjusted to avoid overlap with Small-Mid
     if (__builtin_expect(size <= tiny_get_max_size(), 1)) {
 #if HAKMEM_DEBUG_TIMING
         HKM_TIME_START(t_tiny);
diff --git a/core/hakmem_smallmid.c b/core/hakmem_smallmid.c
index 21ef5648..8de3ff76 100644
--- a/core/hakmem_smallmid.c
+++ b/core/hakmem_smallmid.c
@@ -170,40 +170,84 @@ static inline bool smallmid_tls_push(int class_idx, void* ptr) {
 }
 
 // ============================================================================
-// Backend: Use Tiny Allocator APIs (Phase 17-1)
+// Backend Delegation (Phase 17-1: Reuse Tiny infrastructure)
 // ============================================================================
 
 /**
- * smallmid_backend_alloc - Allocate from Tiny backend
+ * smallmid_backend_alloc - Allocate from Tiny backend and convert header
  *
- * @param size  Allocation size
- * @return      Allocated pointer (user pointer, no Small-Mid header)
+ * @param size  Allocation size (256-1024)
+ * @return      User pointer with Small-Mid header (0xb0), or NULL on failure
  *
- * Phase 17-1: Delegate to existing Tiny allocator infrastructure
- * This reuses Tiny's SuperSlab/SharedPool without building dedicated backend
+ * Strategy:
+ * - Call Tiny allocator (handles C5/C6/C7 = 256B/512B/1KB)
+ * - Tiny writes header: 0xa5/0xa6/0xa7
+ * - Overwrite with Small-Mid header: 0xb0/0xb1/0xb2
  */
-static inline void* smallmid_backend_alloc(size_t size) {
+static void* smallmid_backend_alloc(size_t size) {
     #ifdef HAKMEM_SMALLMID_STATS
     __atomic_fetch_add(&g_smallmid_stats.tls_misses, 1, __ATOMIC_RELAXED);
+    __atomic_fetch_add(&g_smallmid_stats.superslab_refills, 1, __ATOMIC_RELAXED);
     #endif
 
-    // Call Tiny allocator (reuses existing SuperSlab/SharedPool)
+    // Call Tiny allocator
     void* ptr = hak_tiny_alloc(size);
-    SMALLMID_LOG("smallmid_backend_alloc(%zu) = %p (via Tiny)", size, ptr);
+    if (!ptr) {
+        SMALLMID_LOG("smallmid_backend_alloc(%zu): Tiny allocation failed", size);
+        return NULL;
+    }
+
+    // Overwrite header: Tiny (0xa0 | tiny_class) → Small-Mid (0xb0 | sm_class)
+    // Tiny class mapping: C5=256B, C6=512B, C7=1KB
+    // Small-Mid class mapping: SM0=256B, SM1=512B, SM2=1KB
+    uint8_t* base = (uint8_t*)ptr - 1;
+    uint8_t tiny_header = *base;
+    uint8_t tiny_class = tiny_header & 0x0f;
+
+    // Convert Tiny class (5/6/7) to Small-Mid class (0/1/2)
+    int sm_class = tiny_class - 5;
+    if (sm_class < 0 || sm_class >= SMALLMID_NUM_CLASSES) {
+        // Should never happen - Tiny allocated wrong class
+        SMALLMID_LOG("smallmid_backend_alloc(%zu): Invalid Tiny class %d", size, tiny_class);
+        // Revert header and free
+        hak_tiny_free(ptr);
+        return NULL;
+    }
+
+    // Write Small-Mid header
+    *base = 0xb0 | sm_class;
+
+    SMALLMID_LOG("smallmid_backend_alloc(%zu) = %p (Tiny C%d → SM C%d)", size, ptr, tiny_class, sm_class);
     return ptr;
 }
 
 /**
- * smallmid_backend_free - Free to Tiny backend
+ * smallmid_backend_free - Convert header and delegate to Tiny backend
  *
- * @param ptr   User pointer (no Small-Mid header)
- * @param size  Allocation size
+ * @param ptr   User pointer (must have Small-Mid header 0xb0)
+ * @param size  Allocation size (unused, Tiny reads header)
  *
- * Phase 17-1: Delegate to existing Tiny allocator infrastructure
+ * Strategy:
+ * - Convert header: Small-Mid (0xb0 | sm_class) → Tiny (0xa0 | tiny_class)
+ * - Call Tiny free to handle deallocation
  */
-static inline void smallmid_backend_free(void* ptr, size_t size) {
-    (void)size;  // Unused: Tiny free reads header, doesn't need size
-    SMALLMID_LOG("smallmid_backend_free(%p) (via Tiny)", ptr);
+static void smallmid_backend_free(void* ptr, size_t size) {
+    (void)size;  // Unused - Tiny reads size from header
+
+    // Read Small-Mid header
+    uint8_t* base = (uint8_t*)ptr - 1;
+    uint8_t sm_header = *base;
+    uint8_t sm_class = sm_header & 0x0f;
+
+    // Convert Small-Mid class (0/1/2) to Tiny class (5/6/7)
+    uint8_t tiny_class = sm_class + 5;
+
+    // Write Tiny header
+    *base = 0xa0 | tiny_class;
+
+    SMALLMID_LOG("smallmid_backend_free(%p): SM C%d → Tiny C%d", ptr, sm_class, tiny_class);
+
+    // Call Tiny free
     hak_tiny_free(ptr);
 }
 
@@ -247,16 +291,16 @@ void* smallmid_alloc(size_t size) {
         return (uint8_t*)ptr + 1;  // Return user pointer (skip header)
     }
 
-    // Slow path: Allocate from Tiny backend (no refill, direct delegation)
-    // Phase 17-1: Simplified - no TLS refill, just pass through to Tiny
-    void* backend_ptr = smallmid_backend_alloc(size);
-    if (!backend_ptr) {
-        SMALLMID_LOG("smallmid_alloc(%zu) = NULL (backend alloc failed)", size);
+    // TLS miss: Allocate from Tiny backend
+    // Phase 17-1: Reuse Tiny infrastructure (C5/C6/C7) instead of dedicated SuperSlab
+    ptr = smallmid_backend_alloc(size);
+    if (!ptr) {
+        SMALLMID_LOG("smallmid_alloc(%zu) = NULL (backend failed)", size);
         return NULL;
     }
 
-    SMALLMID_LOG("smallmid_alloc(%zu) = %p (backend alloc, class=%d)", size, backend_ptr, class_idx);
-    return backend_ptr;  // Backend returns user pointer directly
+    SMALLMID_LOG("smallmid_alloc(%zu) = %p (backend alloc, class=%d)", size, ptr, class_idx);
+    return ptr;
 }
 
 // ============================================================================
diff --git a/core/hakmem_tiny.c b/core/hakmem_tiny.c
index 4db9d1b5..31f66f8e 100644
--- a/core/hakmem_tiny.c
+++ b/core/hakmem_tiny.c
@@ -50,10 +50,15 @@ const size_t g_tiny_class_sizes[TINY_NUM_CLASSES] = {
 
 // ============================================================================
 // Phase 16: Dynamic Tiny Max Size (ENV: HAKMEM_TINY_MAX_CLASS)
+// Phase 17-1: Auto-adjust when Small-Mid enabled
 // ============================================================================
 
+// Forward declaration for Small-Mid check
+extern bool smallmid_is_enabled(void);
+
 // Get dynamic max size for Tiny allocator based on ENV configuration
 // Default: 1023B (C0-C7), can be reduced to 255B (C0-C5)
+// Phase 17-1: Auto-reduces to 255B when Small-Mid is enabled
 size_t tiny_get_max_size(void) {
     static int g_max_class = -1;
     if (__builtin_expect(g_max_class == -1, 0)) {
@@ -70,12 +75,19 @@ size_t tiny_get_max_size(void) {
         }
     }
 
+    // Phase 17-1: Auto-adjust when Small-Mid enabled
+    // Small-Mid handles 256B-1KB, so Tiny should only handle 0-255B
+    int effective_class = g_max_class;
+    if (smallmid_is_enabled() && effective_class > 5) {
+        effective_class = 5;  // Limit to C0-C5 (0-255B)
+    }
+
     // Map class to max usable size (stride - 1)
     // C0=8B, C1=16B, C2=32B, C3=64B, C4=128B, C5=256B, C6=512B, C7=1024B
     static const size_t class_to_max_size[TINY_NUM_CLASSES] = {
         7, 15, 31, 63, 127, 255, 511, 1023
     };
-    return class_to_max_size[g_max_class];
+    return class_to_max_size[effective_class];
 }
 
 // ============================================================================
diff --git a/hakmem.d b/hakmem.d
index 30aef2cd..624751bd 100644
--- a/hakmem.d
+++ b/hakmem.d
@@ -17,7 +17,8 @@ hakmem.o: core/hakmem.c core/hakmem.h core/hakmem_build_flags.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/box/hak_alloc_api.inc.h core/box/hak_free_api.inc.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 \
  core/box/../tiny_region_id.h core/box/../hakmem_build_flags.h \
  core/box/../tiny_box_geometry.h \
@@ -83,6 +84,8 @@ core/box/hak_kpi_util.inc.h:
 core/box/hak_core_init.inc.h:
 core/hakmem_phase7_config.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:
diff --git a/hakmem_mid_mt.d b/hakmem_mid_mt.d
index 0336a756..4bfe7fbe 100644
--- a/hakmem_mid_mt.d
+++ b/hakmem_mid_mt.d
@@ -1,2 +1,8 @@
-hakmem_mid_mt.o: core/hakmem_mid_mt.c core/hakmem_mid_mt.h
+hakmem_mid_mt.o: core/hakmem_mid_mt.c core/hakmem_mid_mt.h \
+ core/hakmem_tiny.h core/hakmem_build_flags.h core/hakmem_trace.h \
+ core/hakmem_tiny_mini_mag.h
 core/hakmem_mid_mt.h:
+core/hakmem_tiny.h:
+core/hakmem_build_flags.h:
+core/hakmem_trace.h:
+core/hakmem_tiny_mini_mag.h:
diff --git a/hakmem_smallmid.d b/hakmem_smallmid.d
new file mode 100644
index 00000000..48c77148
--- /dev/null
+++ b/hakmem_smallmid.d
@@ -0,0 +1,15 @@
+hakmem_smallmid.o: core/hakmem_smallmid.c core/hakmem_smallmid.h \
+ core/hakmem_build_flags.h core/hakmem_tiny.h core/hakmem_trace.h \
+ core/hakmem_tiny_mini_mag.h core/tiny_region_id.h \
+ core/tiny_box_geometry.h core/hakmem_tiny_superslab_constants.h \
+ core/hakmem_tiny_config.h core/ptr_track.h
+core/hakmem_smallmid.h:
+core/hakmem_build_flags.h:
+core/hakmem_tiny.h:
+core/hakmem_trace.h:
+core/hakmem_tiny_mini_mag.h:
+core/tiny_region_id.h:
+core/tiny_box_geometry.h:
+core/hakmem_tiny_superslab_constants.h:
+core/hakmem_tiny_config.h:
+core/ptr_track.h: