diff --git a/CURRENT_TASK.md b/CURRENT_TASK.md
index 608c913a..9e5a11e9 100644
--- a/CURRENT_TASK.md
+++ b/CURRENT_TASK.md
@@ -1,6 +1,36 @@
 # 本線タスク（現在）
 
-## 現在地: Phase MID-V35-HOTPATH-OPT-1 完了 → 次フェーズ選定待ち
+## 現在地: Phase POOL-MID-DN-BATCH 完了 ✅ → 次フェーズ選定待ち
+
+---
+
+### Status: Phase POOL-MID-DN-BATCH 完了 ✅ (2025-12-12)
+
+**Summary**:
+- **Goal**: Eliminate `mid_desc_lookup` from pool_free_v1 hot path by deferring inuse_dec
+- **Mixed (bench_mid_large_mt_hakmem)**: **+2.8%** improvement ✅ (7.94M → 8.16M ops/s, median)
+- **Strategy**: TLS map batching (~32 pages/drain) + thread exit cleanup
+- **Decision**: Default OFF (ENV gate),可用于生产环境测试
+
+**Key Achievements**:
+- Hot path: Zero lookups (O(1) TLS map update only)
+- Cold path: Batched lookup + atomic subtract (32x reduction in lookup frequency)
+- Thread-safe: pthread_key cleanup ensures pending ops drained on thread exit
+- Stats: 82K deferred hits, 2.5K drain calls, 3.5K empty transitions
+
+**Deliverables**:
+- `core/box/pool_mid_inuse_deferred_env_box.h` (ENV gate: HAKMEM_POOL_MID_INUSE_DEFERRED)
+- `core/box/pool_mid_inuse_tls_pagemap_box.h` (32-entry TLS map)
+- `core/box/pool_mid_inuse_deferred_box.h` (deferred API + drain logic)
+- `core/box/pool_mid_inuse_deferred_stats_box.h` (counters + dump)
+- `core/box/pool_free_v1_box.h` (integration: fast + slow paths)
+- Benchmark: +2.8% median, within target range (+2-4%)
+
+**ENV Control**:
+```bash
+HAKMEM_POOL_MID_INUSE_DEFERRED=0  # Default (immediate dec)
+HAKMEM_POOL_MID_INUSE_DEFERRED=1  # Enable deferred batching
+```
 
 ---