diff --git a/docs/ISSUES.md b/docs/ISSUES.md
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@@ -46,6 +46,64 @@ Copy this block when adding a new issue:
 
 ---
 
+## #174 — Door Use dies after the first attempt: close-range deferred uses silently swallowed (player MoveToManager never completes)
+
+**Status:** OPEN — root under investigation (wire + log evidence in hand; needs one `ACDREAM_PROBE_AUTOWALK=1` round to pick between the two candidate mechanisms)
+**Severity:** HIGH (can't open doors reliably → blocks the #137 door acceptance + normal play)
+**Filed:** 2026-07-05
+**Component:** interaction — B.4b Use pipeline / AP-23 speculative moveto deferral (R5-V5 facade)
+
+**Description (user, Facility Hub 0x8A02, door guid 0x78A020C7 Setup 0x02000C9D
+useRadius=0.50):** double-clicking / R-using the door does nothing. The same
+door opens fine from the retail client on the same ACE, and acdream renders
+the observed swing correctly (inbound path healthy).
+
+**Evidence (3 wire captures + app log, 2026-07-05):**
+1. First attempt (log): `use-deferred seq=624` fired (the close-range
+   deferral COMPLETED once — arrival callback ran), then 625 + 642–647 sent
+   far-range. Door never opened. ACE's replies to those weren't captured.
+2. Retail control (capture `door-use3.pcapng`): retail sent
+   `[0xF7B1][seq][0x36][guid]` ×5 — ACE responded EVERY time with door
+   `0xF74C` UpdateMotion + `0xF74B` SetState (ETHEREAL toggling 0x1001C ↔
+   0x10018), broadcast to BOTH clients. Message format identical to ours.
+3. acdream re-try (capture `door-use4.pcapng` + log): 2× DoubleClick + 4× R
+   — picks land, but ZERO `[B.4b] use` lines and ZERO door-guid packets on
+   the wire. The Use is swallowed CLIENT-SIDE before the send.
+
+**Mechanism (code trace):** `SendUse` close-range branch (≤2 m by the AP-23
+bucket — this door's flags → 2.0 m, overriding its real 0.5 m) parks the
+action in `_pendingPostArrivalAction` and fires it ONLY from
+`MoveToComplete(WeenieError.None)` (natural completion of the speculative
+TurnToObject installed through the R5-V5 facade). A cancel (user input) or a
+never-starting turn silently eats the use — no toast, no log (the deferral
+prints are probe-gated). Candidates for "never completes": (a) the
+`BeginTurnToHeading` `MotionsPending()` early-return starving the turn (the
+#170 class, local-player edition — the log shows a steady
+`MOTIONDONE pending=True` stream); (b) every attempt instantly cancelled by
+concurrent user movement input (retail-faithful per-attempt, but the user
+also clicked while standing still). Also noted: `GameEventType.UseDone`
+(0x01C7) is parsed nowhere (not registered in `GameEventWiring`) — ACE
+rejection reasons are invisible; and the first attempt's 7 sent uses never
+opened the door either (suspect: concurrent outbound movement cancelling
+ACE's MoveToChain server-side — unproven, replies not captured).
+
+**Files:** `src/AcDream.App/Rendering/GameWindow.cs` (`SendUse` ~12607,
+`OnAutoWalkArrivedSendDeferredAction` ~12761, `InstallSpeculativeTurnToTarget`
+~12842, `MoveToFactory` callback wiring ~13530);
+`src/AcDream.Core/Physics/Motion/MoveToManager.cs` (`BeginNextNode` /
+`BeginTurnToHeading` gates). Captures in the session scratchpad
+(`door-use3.pcapng`, `door-use4.pcapng`).
+
+**Next:** relaunch with `ACDREAM_PROBE_AUTOWALK=1`; user clicks the door
+(a) standing still, (b) right after moving. `[autowalk-end reason=complete
+err=…]` vs silence discriminates cancel-vs-starved. Fix per retail: the use
+flow must either complete the turn and fire, or surface the cancel
+(retail re-queues/cancels visibly — decomp the client use flow §9a/§9b before
+patching). DO NOT band-aid by skipping the deferral (the turn-to-face is
+retail behavior).
+
+---
+
 ## #173 — Observed character jumping into a ceiling hovers at the roof until the arc decays (no collision-velocity response on remotes)
 
 **Status:** 🟡 FIX SHIPPED 2026-07-05 (this commit) — pending user visual gate (watch a second client jump into the 0x0007 dungeon roof; it should bounce down immediately like the local player).