diff --git a/docs/re/BACKLOG.md b/docs/re/BACKLOG.md
index df4689dc..fd89f7de 100644
--- a/docs/re/BACKLOG.md
+++ b/docs/re/BACKLOG.md
@@ -670,6 +670,19 @@ search cannot find a *schedule*.
   no more kills. ❔ **The earlier 4→8→12 rise is NOT reproduced** — both readings
   were HUD-confirmed, so the rise is not a stable property of the first five
   minutes; recorded as unreproduced rather than explained away.
+* ✅🔴 **(2026-08-25) THE MISSION BLACK-SCREENS AT ~4.5 MIN — that is what ends
+  every run.** Two-segment OB watch: segment 1 clean (**0/50 stalled**, OB steady
+  at 4 for 250 s); segment 2 on the same live emulator got **`NOT IN A MISSION`**.
+  Player never died (**hull 1500 throughout**), pilot log stops at **t=267 s** with
+  byte-identical lines, screen now **entirely black** (`mean=(0,0,0)`). This is the
+  known pre-existing mission-end freeze, caught in the act.
+  🔴 **Corrects "chained attaches extend the window"** — the emulator surviving is
+  not the *mission* surviving; ~4.5 min is a hard per-mission bound and chaining
+  does not cross it. ⇒ **Anything needing >4.5 min of one mission is not doable on
+  this build**, including clearing 16 marked fighters at ~2 kills/5 min. The
+  freeze is now the highest-value target: fixing it unblocks arrivals, phase
+  advance and the OB series at once. ❔ The 4→8→12 OB rise is now unreproduced in
+  **3 of 4** runs.
 * ~~🚧 BLOCKER: t=210/240 unreachable in one turn~~ — **superseded, see above**;
   it rested on an untested assumption that a turn is one shell call. 595 s shell cap − ~220 s boot (a ~190 s title movie that cannot be
   tapped through) − ~25 s startup = **~350 s observation ≈ 193 game-seconds**.
diff --git a/docs/re/guest-stalls.md b/docs/re/guest-stalls.md
index 294c68cb..8b79c984 100644
--- a/docs/re/guest-stalls.md
+++ b/docs/re/guest-stalls.md
@@ -413,3 +413,50 @@ it is the only remaining lever worth pulling if longer windows are needed.
 Do not treat a single frozen run as evidence of anything. Run, check the witness,
 discard the frozen ones, and keep the clean runs — about three in four are usable
 now, which is workable where it previously was not.
+
+---
+
+# ✅ What actually ends these runs: the mission black-screens at ~4.5 min (2026-08-25)
+
+A two-segment OB watch made the mechanism visible for the first time.
+
+**Segment 1** ran clean — witness reporting **0 stalled samples of 50**, OB steady
+at 4 for 250 s. **Segment 2**, attaching to the same emulator, got:
+
+```
+NOT IN A MISSION (no unit definitions)
+```
+
+The emulator was still alive. The *mission* was gone. Looking at why:
+
+* the pilot's **hull is 1500 in every line** — the player never died;
+* the pilot log stops at **t = 267 s** with consecutive byte-identical lines
+  (`spd=78`, same aim) — the freeze signature;
+* the screen is now **entirely black**: `mean=(0.0, 0.0, 0.0)`.
+
+This is the **pre-existing mission-end black-screen freeze** already recorded in
+the corpus, caught in the act. Segment 1's clean witness is not a contradiction:
+it sampled to t ≈ 250 s and the freeze came at ≈ 267 s.
+
+## 🔴 Correction: chained attaches do NOT extend a mission
+
+[mission-arrival-watch.md](mission-arrival-watch.md) records "BLOCKER REMOVED:
+the emulator survives between calls", and that is true — but it was stated as if
+observation could be extended indefinitely within a turn. It cannot. **The
+emulator surviving is not the mission surviving.** The binding limit is the
+game's own black-screen at roughly four and a half minutes, and no amount of
+chaining crosses it.
+
+The earlier chained run that reached 435 s of cumulative verified-live
+observation did so across *two* segments of one mission — consistent with this,
+since its second segment froze at t = 135 s.
+
+## What it means for the open questions
+
+* Any experiment needing more than ~4.5 minutes of one continuous mission is
+  **not doable** on this build, chained or not. That includes clearing 16 marked
+  fighters at two kills per five minutes.
+* The freeze is now the highest-value target in its own right: fixing it would
+  unblock the arrival question, the phase-advance question and the OB series at
+  once. It is also, per the corpus, a long-standing known defect rather than
+  something this work introduced.
diff --git a/tools/re-capture/obwatch_attach.sh b/tools/re-capture/obwatch_attach.sh
new file mode 100755
index 00000000..a168c8c1
--- /dev/null
+++ b/tools/re-capture/obwatch_attach.sh
@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+set -u
+export HOME=/sylph-home/re SDL_AUDIODRIVER=dummy DISPLAY=:98
+export PYTHONPATH=/sylph-home/.local/lib/python3.12/site-packages
+SD="$(cd "$(dirname "$0")" && pwd)"
+pgrep -x xenia_canary >/dev/null || { echo "NO EMULATOR"; exit 1; }
+CFG=/tmp/nav-obhud2.json
+for try in 1 2 3; do
+  python3 "$SD/pad.py" set "rt=1" >/dev/null 2>&1 || true; sleep 3
+  python3 "$SD/pad.py" clear >/dev/null 2>&1 || true
+  if python3 "$SD/entities2.py" self 0x130 "$CFG" >/dev/null 2>&1; then
+    SYLPH_HUNT=1 SYLPH_KILL_TURRETS=1 SYLPH_KEEPOUT=1400 SYLPH_PREFER=e010 \
+      nohup python3 "$SD/pilot.py" "$CFG" "${1:-400}" </dev/null >/tmp/obhud2-pilot.log 2>&1 &
+    P=$!; echo "--- pilot re-attached"; break
+  fi
+done
+python3 "$SD/ob_watch.py" "${1:-400}" "${2:-25}"
+[ -n "${P:-}" ] && kill "$P" 2>/dev/null
+echo "OBHUD ATTACH DONE"