diff --git a/scripts/progress-watchdog.sh b/scripts/progress-watchdog.sh
new file mode 100755
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+++ b/scripts/progress-watchdog.sh
@@ -0,0 +1,94 @@
+#!/usr/bin/env bash
+# forge-loop forward-progress watchdog.
+#
+# WHY: event watchers (PR_OPEN / STALL / DEAD) are blind to "busy but not
+# progressing" — a loop can spin for hours re-reviewing one approved-but-blocked
+# PR while every liveness check stays green (this cost ~9h once). The invariant
+# that matters is FORWARD PROGRESS (merges landing), not liveness. This script
+# watches that invariant and exits non-zero on a tripwire so a supervisor (cron,
+# systemd, an operator, or an agent re-invoked on exit) can react.
+#
+# USAGE:
+#   REPO_PATH=/path/to/checkout GH_REPO=owner/name scripts/progress-watchdog.sh
+#
+# ENV (all optional except the two above):
+#   REPO_PATH    local checkout the loop runs in        (default: cwd)
+#   GH_REPO      GitHub slug owner/name for merge polling (required for stall check)
+#   STALL_SECS   no-merge window before a stall          (default: 5400 = 90min)
+#   QUIET_SECS   event-log silence to confirm "stuck"    (default: 1800 = 30min)
+#   POLL_SECS    seconds between checks                  (default: 600 = 10min)
+#   COMMENT_CAP  open-PR comment count = comment-storm   (default: 18)
+#   EVENTLOG     path to loop-runner-events.jsonl        (default: $REPO_PATH/docs/ops/loop-runner-events.jsonl)
+#   STOPFILE     path to the loop stop-file              (default: $REPO_PATH/docs/ops/loop-runner.stop)
+#
+# EXIT CODES (tripwires):
+#   10  loop entrypoint absent (DEAD)
+#   11  stop-file present
+#   12  no merge in STALL_SECS AND event log quiet QUIET_SECS (STUCK)
+#   13  an open PR is piling up comments past COMMENT_CAP (busy-but-stuck)
+#    2  misconfiguration
+#
+# NOTE on liveness detection: match the real installed entrypoint "bin/forge-loop"
+# (NOT the string "forge-loop run", which self-matches an interactive shell that
+# happens to contain that literal). Retry briefly to tolerate a tick boundary.
+set -u
+
+REPO_PATH="${REPO_PATH:-$PWD}"
+GH_REPO="${GH_REPO:-}"
+STALL_SECS="${STALL_SECS:-5400}"
+QUIET_SECS="${QUIET_SECS:-1800}"
+POLL_SECS="${POLL_SECS:-600}"
+COMMENT_CAP="${COMMENT_CAP:-18}"
+EVENTLOG="${EVENTLOG:-$REPO_PATH/docs/ops/loop-runner-events.jsonl}"
+STOPFILE="${STOPFILE:-$REPO_PATH/docs/ops/loop-runner.stop}"
+
+cd "$REPO_PATH" || { echo "WATCHDOG: cannot cd $REPO_PATH"; exit 2; }
+command -v gh >/dev/null 2>&1 || { echo "WATCHDOG: gh CLI not found"; exit 2; }
+
+# gh needs an empty GH_TOKEN to use its own stored auth (a loop-exported GH_TOKEN
+# breaks the gh CLI). Poll merges via ls-remote so no token is needed at all.
+remote_main_sha() { git ls-remote "https://github.com/$GH_REPO.git" main 2>/dev/null | awk '{print $1}'; }
+
+base_sha=""
+[ -n "$GH_REPO" ] && base_sha="$(remote_main_sha)"
+last_advance="$(date +%s)"
+
+echo "WATCHDOG: watching $REPO_PATH (repo=${GH_REPO:-<none>}) stall=${STALL_SECS}s quiet=${QUIET_SECS}s poll=${POLL_SECS}s"
+
+while true; do
+  now="$(date +%s)"
+
+  # 1. loop alive? (real entrypoint, brief retry window for tick boundaries)
+  alive=0
+  for _ in 1 2 3; do
+    if pgrep -af "bin/forge-loop" 2>/dev/null | grep -qv -e pgrep -e watchdog; then alive=1; break; fi
+    sleep 10
+  done
+  [ "$alive" = "0" ] && { echo "TRIPWIRE(10): forge-loop entrypoint absent (DEAD)"; exit 10; }
+
+  # 2. stop-file
+  [ -f "$STOPFILE" ] && { echo "TRIPWIRE(11): stop-file present ($STOPFILE)"; exit 11; }
+
+  # 3. forward progress: merge advanced OR loop still actively ticking
+  if [ -n "$GH_REPO" ]; then
+    cur_sha="$(remote_main_sha)"
+    [ -n "$cur_sha" ] && [ "$cur_sha" != "$base_sha" ] && { base_sha="$cur_sha"; last_advance="$now"; }
+    ev_age=999999
+    [ -f "$EVENTLOG" ] && ev_age=$(( now - $(stat -c %Y "$EVENTLOG" 2>/dev/null || echo 0) ))
+    # Two-factor: a fresh event log means the loop is working (building/repairing a
+    # risk-gated PR that parks for human review IS progress) — only a frozen log
+    # plus no merge is a genuinely stuck loop.
+    if [ $(( now - last_advance )) -ge "$STALL_SECS" ] && [ "$ev_age" -ge "$QUIET_SECS" ]; then
+      echo "TRIPWIRE(12): no merge in $((STALL_SECS/60))min AND event log quiet ${ev_age}s (STUCK)"; exit 12
+    fi
+  fi
+
+  # 4. a PR piling up comments without merging (busy-but-stuck signature)
+  if [ -n "$GH_REPO" ]; then
+    stuck="$(GH_TOKEN= gh pr list --repo "$GH_REPO" --state open \
+              --json number,comments --jq ".[]|select((.comments|length)>$COMMENT_CAP)|.number" 2>/dev/null | head -1)"
+    [ -n "$stuck" ] && { echo "TRIPWIRE(13): PR #$stuck piling up >$COMMENT_CAP comments without merging"; exit 13; }
+  fi
+
+  sleep "$POLL_SECS"
+done