diff --git a/scripts/t3-autoupdate.sh b/scripts/t3-autoupdate.sh
index bdd26b87..a3928211 100644
--- a/scripts/t3-autoupdate.sh
+++ b/scripts/t3-autoupdate.sh
@@ -21,7 +21,7 @@
 #   - canary rollout: restart idle instances ONE AT A TIME, verifying pairing
 #     through the real dispatch after each, and roll back (binary + that user's DB)
 #     + self-freeze on the first failure — active-agent instances are deferred,
-#     never killed;
+#     never killed (deferred instances are recorded for t3-migrate-idle to drain);
 #   - rollback target is the recorded LAST-GOOD build, not "whatever was installed".
 # Detection backstop (real-user pairing failure/fallback) lives in the dispatch
 # logs + Loki alerts (T3PairingBroken / T3PairFallbackHigh / T3AutoUpdate*).
@@ -29,24 +29,17 @@
 # Full procedure + manual rollback: docs/runbooks/t3-version-bump.md.
 set -uo pipefail
 
+# ---- autoupdate-specific config (shared config + helpers come from the lib) -----
 T3_TRACK="${T3_TRACK:-nightly}"            # npm dist-tag to follow (nightly | latest)
 T3_PIN="${T3_PIN:-}"                        # optional HARD pin to an exact version (disables tracking)
-FREEZE_FILE="${T3_FREEZE_FILE:-/etc/t3-autoupdate.freeze}"
-STATE_DIR="${T3_STATE_DIR:-/var/lib/t3-autoupdate}"
-LAST_GOOD_FILE="$STATE_DIR/last-good"
-BACKUP_DIR="${T3_BACKUP_DEST:-/var/backups/t3-state}"
 SMOKE_PORT="${T3_SMOKE_PORT:-3799}"
-DISPATCH="${T3_DISPATCH:-127.0.0.1:3780}"
-USER_MAP="${T3_USER_MAP:-/etc/ttyd-user-map}"
 DRY_RUN="${T3_DRY_RUN:-0}"
 TMPROOT="${T3_TMPDIR:-/var/tmp}"           # health-check scratch on DISK — /tmp is a 2G tmpfs and a populated state.sqlite (~hundreds of MB) overflows it
 
-LOG() { logger -t t3-autoupdate "$*"; echo "t3-autoupdate: $*"; }
-ver() { t3 --version 2>/dev/null | awk '{print $NF}' | sed 's/^v//'; }
-# OS users owning a ~/.t3 (RHS of each non-comment "authentik=os_user" map line).
-osusers() { awk -F= '!/^[[:space:]]*#/&&NF==2{gsub(/[[:space:]]/,"",$2);print $2}' "$USER_MAP" 2>/dev/null | sort -u; }
-# authentik username for an OS user (reverse map; first match) — for dispatch verify.
-ak_for() { awk -F= -v u="$1" '!/^[[:space:]]*#/&&NF==2{gsub(/[[:space:]]/,"",$1);gsub(/[[:space:]]/,"",$2);if($2==u){print $1;exit}}' "$USER_MAP" 2>/dev/null; }
+LOG_TAG=t3-autoupdate
+# shellcheck source=scripts/t3-safe-restart.sh
+. "${T3_SAFE_RESTART_LIB:-/usr/local/lib/t3-safe-restart.sh}"
+
 # is $1 a strictly-newer version than $2 (version-sort)?
 newer() { [ "$1" != "$2" ] && [ "$(printf '%s\n%s\n' "$1" "$2" | sort -V | tail -1)" = "$1" ]; }
 
@@ -86,27 +79,21 @@ LOG "candidate: $current -> $target (track=$T3_TRACK, last_good=$last_good, dry_
 # ---- helpers: backup, health-check, rollback, restart-verify --------------------
 # Online consistent per-user snapshot (run AS the owner so WAL stays owned; never
 # stops the serve). Sets $ADMIN_SEED to wizard's backup for the migration health
-# check. Mirrors t3-backup-state.sh.
+# check. Mirrors t3-backup-state.sh. (backup_user lives in the shared lib.)
 ADMIN_SEED=""
 backup_all() {
-  local u src out dst ts; ts="$(date +%Y%m%d-%H%M%S)"
+  local u dst
   for u in $(osusers); do
-    src="/home/$u/.t3/userdata/state.sqlite"; [ -f "$src" ] || continue
-    out="$BACKUP_DIR/$u"; dst="$out/state-prebump-$target-$ts.sqlite"
-    install -d -o "$u" -g "$u" -m700 "$out" 2>/dev/null || mkdir -p "$out"
-    if runuser -u "$u" -- timeout "${T3_BACKUP_TIMEOUT:-900}" sqlite3 "$src" "VACUUM INTO '$dst'" 2>/dev/null && [ -s "$dst" ]; then
+    if dst="$(backup_user "$u")"; then
       LOG "pre-bump backup: $u -> $dst ($(stat -c%s "$dst" 2>/dev/null) bytes)"
       [ "$u" = "wizard" ] && ADMIN_SEED="$dst"
     else
-      LOG "WARN: pre-bump backup FAILED for $u ($src)"; rm -f "$dst"
+      LOG "WARN: pre-bump backup FAILED for $u (/home/$u/.t3/userdata/state.sqlite)"
     fi
   done
   [ -n "$ADMIN_SEED" ] || ADMIN_SEED="$(ls -1t "$BACKUP_DIR"/*/"state-prebump-$target-"*.sqlite 2>/dev/null | head -1)"
 }
 
-# newest pre-bump backup taken THIS run for a user (for restore-on-rollback).
-prebump_of() { ls -1t "$BACKUP_DIR/$1/state-prebump-$target-"*.sqlite 2>/dev/null | head -1; }
-
 # health_check <t3bin> [seed_db]: start a throwaway serve (seeded with a copy of a
 # real populated DB if given, so the forward migration runs on real data), then do
 # the real mint -> credential-exchange -> t3_session pairing handshake with the
@@ -143,27 +130,12 @@ health_check() {
   rm -rf "$dir"; return 1
 }
 
-# roll the GLOBAL binary back to last-good. Pre-restart failures need only this
-# (no real DB migrated yet); post-restart failures also restore the user's DB.
-rollback_binary() {
-  LOG "rolling back binary $target -> $last_good"
-  if npm i -g "t3@$last_good" >/dev/null 2>&1; then LOG "rolled back to $last_good"; return 0; fi
-  LOG "ROLLBACK FAILED — could not reinstall t3@$last_good (t3 may be broken; manual fix per runbook)"; return 1
-}
-
 # is this t3-serve@<unit> running an active agent (claude/codex/opencode)? never restart those.
 unit_busy() {
   local unit="$1" pid; pid="$(systemctl show -p MainPID --value "$unit" 2>/dev/null)"
   [ -n "$pid" ] && [ "$pid" != "0" ] && pgrep -aP "$pid" 2>/dev/null | grep -qiE 'claude|codex|opencode'
 }
 
-# verify a user's pairing through the REAL dispatch (mint -> exchange -> cookie).
-verify_pairing() {
-  local u="$1" ak out; ak="$(ak_for "$u")"; [ -n "$ak" ] || { LOG "no authentik mapping for $u — skipping dispatch verify"; return 0; }
-  out="$(curl -s -i --max-time 10 -H "X-authentik-username: $ak" -H 'Sec-Fetch-Dest: document' "http://$DISPATCH/" 2>/dev/null)"
-  printf '%s' "$out" | grep -qi '^set-cookie:[[:space:]]*t3_session='
-}
-
 # ---- 3. DRY RUN: preview only (install candidate to temp prefix, gate it) -------
 if [ "$DRY_RUN" = "1" ]; then
   LOG "DRY_RUN: would back up [$(osusers | tr '\n' ' ')]; testing candidate $target in a temp prefix (no global change, no restarts)"
@@ -196,31 +168,15 @@ restarted=0; deferred=0
 for unit in $(systemctl list-units --type=service --state=running --no-legend 't3-serve@*' 2>/dev/null | awk '{print $1}'); do
   u="$(printf '%s' "$unit" | sed -n 's/^t3-serve@\(.*\)\.service$/\1/p')"; [ -n "$u" ] || continue
   if unit_busy "$unit"; then
-    LOG "deferring $unit (active agent) — migrates on its next idle restart"; deferred=$((deferred+1)); continue
+    LOG "deferring $unit (active agent) — migrates on its next idle restart"
+    mkdir -p "$DEFER_DIR" 2>/dev/null && printf '%s\n' "$target" >"$DEFER_DIR/$u"   # record for t3-migrate-idle
+    deferred=$((deferred+1)); continue
   fi
-  systemctl restart "$unit" || LOG "WARN: systemctl restart $unit returned non-zero"
-  ok=0
-  for _ in $(seq 1 15); do
-    if verify_pairing "$u"; then ok=1; break; fi
-    sleep 2
-  done
-  if [ "$ok" = "1" ]; then
-    LOG "restarted $unit -> $target (pairing verified via dispatch)"; restarted=$((restarted+1))
+  if safe_restart_unit "$unit" "$u"; then
+    restarted=$((restarted+1))
+    rm -f "$DEFER_DIR/$u" 2>/dev/null            # now current — clear any stale marker
   else
-    LOG "HEALTH-CHECK FAILED: $u pairing broken AFTER restart onto $target — rolling back + restoring its DB"
-    rollback_binary
-    bak="$(prebump_of "$u")"
-    if [ -n "$bak" ]; then
-      systemctl stop "$unit" 2>/dev/null
-      if install -o "$u" -g "$u" -m600 "$bak" "/home/$u/.t3/userdata/state.sqlite" 2>/dev/null; then
-        rm -f "/home/$u/.t3/userdata/state.sqlite-wal" "/home/$u/.t3/userdata/state.sqlite-shm"
-        LOG "restored $u state.sqlite from $bak"
-      fi
-      systemctl start "$unit" 2>/dev/null
-    fi
-    touch "$FREEZE_FILE" 2>/dev/null
-    LOG "FROZEN ($FREEZE_FILE) after canary $u failed on $target; last_good stays $last_good — investigate, then remove the freeze file to resume"
-    exit 1
+    exit 1                                        # frozen by safe_restart_unit — preserve today's behavior
   fi
 done