Add Phase 9A: checkpointed handoff — blend(Vec+DFA) outperforms pure DFA

First positive online result: 50% blend of offline-fitted Vec + DFA gives 31.7%
vs 31.1% for pure DFA (+0.55%). This is Case B: pure Vec handoff fails (-1.1%)
but blend works because DFA stabilizes trajectory while Vec adds directional credit.

Offline-fitted Vec at DFA epoch-5 checkpoint: Gamma=0.229, rho=0.262.
Cold-start confirmed as main bottleneck — Vec IS useful on DFA trajectory features.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

1 files changed, 23 insertions, 1 deletions

diff --git a/NOTE.md b/NOTE.md
index 74b75f3..258b20e 100644
--- a/NOTE.md
+++ b/NOTE.md
@@ -5,7 +5,7 @@
 - **pilot**: Controlled iteration (commits 0b9ebb2, 7baf7ae)
 - **frozen**: Code at commit 0b9ebb2 for all reported results
 
-## Status: PHASE 8 SCHEDULE TIMING — ONLINE CO-LEARNING IS THE REMAINING BOTTLENECK
+## Status: PHASE 9A — BLEND HANDOFF OUTPERFORMS DFA (+0.55%)
 
 ---
 
@@ -484,3 +484,25 @@ is ready, the early window is closed.
 
 ### Experiment IDs (Phase 8)
 - `schedule_timing/`: Phase 8 schedule comparison
+
+---
+
+## Phase 9A: Checkpointed Offline Handoff
+
+**Setup**: DFA trajectory with checkpoint at t0=5 (acc=30.4%).
+Offline-fit Vec_M4 on frozen checkpoint (60 epochs). Then branch.
+
+| Branch | final acc | diff vs DFA |
+|--------|-----------|-------------|
+| continue_DFA | 0.311 | baseline |
+| handoff_to_Vec | 0.300 | -0.011 |
+| **handoff_blend_05** | **0.317** | **+0.006** |
+
+**FIRST POSITIVE ONLINE RESULT**: 50% blend (Vec+DFA) outperforms pure DFA by +0.55%.
+
+This is Case B: pure Vec handoff fails, but blend works.
+Vec provides complementary directional credit that DFA alone lacks.
+DFA stabilizes the trajectory while Vec adds learned corrections.
+
+### Experiment IDs (Phase 9)
+- `checkpointed_handoff/`: Phase 9A checkpointed handoff with branches