RESULT 63: 机制闭合 — amp证书宽度碎裂(cos@1e-3: C512 0.968→C768 0.908),bf16噪声地板随宽度上升(BBP无下界=仅fp32); C768走廊中途反转(amp地板要β≳3e-3,天花板沉到1e-3)→中段后无合法β; 三臂死法全落位含b15未知限制因子; 1.5×amp杠杆宽度失效→COST_MODEL需重报价; 修复=fp32 relax或bf16+fp32抛光扫

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014FAPDWQ49M5Ye3NpTndTpn

1 files changed, 23 insertions, 0 deletions

diff --git a/docs/campaign/CASCADE_ABLATION_PLAN.md b/docs/campaign/CASCADE_ABLATION_PLAN.md
index d467cb0..1606dd2 100644
--- a/docs/campaign/CASCADE_ABLATION_PLAN.md
+++ b/docs/campaign/CASCADE_ABLATION_PLAN.md
@@ -568,6 +568,29 @@ direction), not training-under-fault; wave-2 = co-training with faults injected
 
 
 
+### RESULT 63 (2026-07-27): MECHANISM CLOSED — THE AMP CERTIFICATE BREAKS AT WIDTH AND THE
+C768 CORRIDOR INVERTS MID-RUN; every 135M EP failure mode falls into place.
+Chain of three probes (all GPU0, hours): (1) blockcos @s150000: fp32 EP gradient PERFECT
+(cos 0.9999-1.0000, every block, both channels) -> per-step fidelity exonerated at healthy
+states. (2) K-sweep @s250000/s435000: K=3 == K=8 at 0.999 -> K-sufficiency transfers; K
+exonerated. (3) amp_gate rerun on C768 ckpts — THE SMOKING GUN: amp cos @1e-3 = 0.9079 (C512:
+0.9682 == fp32), @3e-3 ~0.95 (C512: 0.9878), @1e-2 0.9761 (C512: 0.9966). The bf16 state-noise
+is fixed-relative, the nudge displacement ~beta, the states are LOUDER at C768 (sigma 661 vs
+475) -> the amp read-noise floor RISES with width. The BBP "no digital detectability floor"
+result was fp32-ONLY; under amp there is a real, width-scaling floor.
+THE INVERSION: amp floor wants beta >~3e-3 for clean reads; the fp32 ceiling sinks to ~1e-3
+late -> from mid-run onward NO legal beta exists under amp at C768. All three EP arms explained:
+3e-3 = over-ceiling; 1.5e-3/7.5e-4 = under the amp floor (b15's unknown limiter FOUND — its
+in-corridor-but-noise-rotten reads). The 0.294 gap = 200k+ steps of systematically degraded
+reads, not any single blowup.
+RECIPE CONSEQUENCES for width: (a) fp32 relax (tax->0, cost 1.5x) — the safe fix, A/B pending;
+(b) bf16 sweeps + fp32 polish sweeps (~1.2x) — needs a probe variant (naive amp_last is WORSE:
+one fp32 rebuild on bf16-settled states reads the bf16 offset as displacement); (c) large-beta
+escape is CLOSED by the sinking ceiling. The 1.5x amp lever that funded the cost model at 1-3B
+is width-broken — COST_MODEL must be re-quoted (fp32 or polish-mix rates) before any external
+number is repeated. NEXT: 72m_bp_s3 clean (GPU0, closes 72M n=3); amp-vs-fp32 C768 A/B replay
+from s250000 when GPUs free.
+
 ### RESULT 62 (2026-07-27): THE C768 ANCHOR — BP 3.0902; the EP gap EXPLODES 6x at the
 first ladder rung (0.047 -> 0.294, ~34% ppl). Width problem is 100% EP-specific; recipe/data/
 shape exonerated (BP gains the full expected -0.198 from 72M).