diff --git a/CLAUDE.md b/CLAUDE.md
index 7c19ee2..b939705 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -1217,6 +1217,14 @@ via `PlayerMovementController.ApplyServerRunRate`) or from
   change: old → new cell, world position, reason tag
   (`resolver` / `teleport`). Low volume — only fires on actual cell
   crossings. Runtime-toggleable via the same DebugPanel section.
+- `ACDREAM_PROBE_PUSH_BACK=1` — A6.P1 cdb probe spike (2026-05-21).
+  Emits three line types per physics tick: `[push-back]` (per
+  `BSPQuery.AdjustSphereToPlane` call), `[push-back-disp]` (per
+  `BSPQuery.FindCollisions` dispatch), `[push-back-cell]` (per
+  `Transition.CheckOtherCells` off-cell hit). Heavy under motion
+  (~100–500 lines/sec). Pair with retail's cdb breakpoint set at
+  `tools/cdb/a6-probe.cdb` for the A6.P1 capture protocol.
+  Runtime-toggleable via the DebugPanel "Diagnostics" section.
 - *(retired 2026-05-05 by L.3 M2/M3)* `ACDREAM_INTERP_MANAGER` was an
   env-var gate on an experimental per-tick remote motion path. L.3 M2
   (commit 40d88b9) replaced both gates (`OnLivePositionUpdated` +