Unified-routing A+B ablation: decode-aware LMetric + v3 anti-hotspot

cache_aware_proxy: add lmetric_decode_weight (decode-load penalty in the
LMetric fallback score) and a v3 anti-hotspot recent-migration penalty
(effective_load = num_req + recent-migration count over a sliding window),
preventing back-to-back migration clustering. UNIFIED_ABLATION.md documents
the A (overload_factor=1.3) + B' (decode-weight, max(num_req,1)) + RaceFix
sweep: A+B'+RaceFix reaches TTFT p90 7770ms, beating v3 PD-sep migration by
~20%. Runners/analyzer for the b3 trace replay included.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

microbench/connector_tax/cache_sweep/run_v3_replay.sh

@@ -0,0 +1,66 @@
+#!/usr/bin/env bash
+# Trace replay for the new unified_v3 (offload-decode) policy.
+#
+# Runs the same trace as run_b3_replay.sh on a single policy:
+#   unified_v3 — prefill on session-affinity host (uses prefix cache),
+#                decode migrated to a low-load target via Mooncake
+#                KV transfer (kv_role=kv_both). Session affinity rotates
+#                to decode_target after migration so next turn lands
+#                where the KV now lives.
+#
+# Applies CT_DR_FIX so the run uses the "best Mooncake state" we have
+# today (post-e3a1d70 + DR sync skipped).
+#
+# Usage: bash run_v3_replay.sh
+
+set -uo pipefail
+
+PROJ_DIR="${PROJ_DIR:-/home/admin/cpfs/wjh/agentic-kv}"
+TRACE="${TRACE:-$PROJ_DIR/traces/w600_r0.0015_st30.jsonl}"
+DATE="$(date +%Y%m%d_%H%M)"
+OUTROOT="${OUTROOT:-$PROJ_DIR/outputs/b3_v3_${DATE}}"
+PYTHON="$PROJ_DIR/.venv/bin/python"
+DR_FIX_SCRIPT="$PROJ_DIR/microbench/connector_tax/cache_sweep/apply_direct_read_fix.py"
+VLLM_ROOT="${VLLM_ROOT:-$PROJ_DIR/.venv/lib/python3.12/site-packages/vllm}"
+
+mkdir -p "$OUTROOT"
+echo "=== unified_v3 (offload-decode) trace replay ==="
+echo "Trace : $TRACE"
+echo "Out   : $OUTROOT"
+echo ""
+
+cleanup_all() {
+    pkill -9 -f cache_aware_proxy 2>/dev/null || true
+    pkill -9 -f "vllm serve" 2>/dev/null || true
+    pkill -9 -f "EngineCore" 2>/dev/null || true
+    sleep 5
+    "$PYTHON" "$DR_FIX_SCRIPT" --revert --vllm-root "$VLLM_ROOT" 2>/dev/null || true
+}
+trap cleanup_all EXIT
+cleanup_all
+
+echo "[stage 0] applying CT_DR_FIX (env-gated)"
+"$PYTHON" "$DR_FIX_SCRIPT" --apply --vllm-root "$VLLM_ROOT"
+
+cfg_dir="$OUTROOT/unified_v3"
+mkdir -p "$cfg_dir"
+
+# Activate the DR-fix env-gate (unified_v3 uses Mooncake kv_both)
+export VLLM_MOONCAKE_DISABLE_DIRECT_READ_SYNC=1
+
+echo ""
+echo "====== unified_v3 ; DR_SYNC_DISABLED=1 ======"
+bash "$PROJ_DIR/scripts/b3_isolated_policy.sh" "unified_v3" "$TRACE" "$cfg_dir" \
+    2>&1 | tee "$cfg_dir/orchestrator.log" | tail -30
+
+pkill -9 -f cache_aware_proxy 2>/dev/null || true
+pkill -9 -f "vllm serve" 2>/dev/null || true
+pkill -9 -f "EngineCore" 2>/dev/null || true
+sleep 5
+
+echo ""
+echo "[stage Z] reverting CT_DR_FIX"
+"$PYTHON" "$DR_FIX_SCRIPT" --revert --vllm-root "$VLLM_ROOT"
+
+echo ""
+echo "Done. Artifacts: $OUTROOT/unified_v3/metrics.jsonl"