diff --git a/scripts/u4_step3_guard.sh b/scripts/u4_step3_guard.sh
index 75b1cb0..c55ee9d 100755
--- a/scripts/u4_step3_guard.sh
+++ b/scripts/u4_step3_guard.sh
@@ -7,25 +7,39 @@
 # u4_step3_retry.sh dies with it (observed: task 554 Killed whole, no retry line).
 #
 # This guard runs DETACHED in its own session/cgroup, uses ~0 RAM (so oomd never
-# targets it), and keeps the resumable fit queued until it completes. jlens
-# checkpoints every prompt (n_done monotonic: 36->45->64->69 across kills), so
-# each oomd kill only costs a model reload. It grinds slowly during the user's
-# active hours and finishes clean overnight once their kernel idles.
+# targets it), and launches the resumable fit ONLY into genuinely-idle GPU/RAM
+# windows (see backoff below) so it never competes with the user's live work.
+# jlens checkpoints every prompt (n_done monotonic: 36->45->64->69 across kills),
+# so any kill only costs a model reload. Completes clean overnight once the
+# user's kernel idles; does nothing (polite) while they are active.
 #
 # Stops itself the instant artifacts/u4_loopclose.txt exists (success). To stop
 # early:  pkill -f u4_step3_guard.sh
 set -u
 cd /media/wassname/SGIronWolf/projects5/2026/jspace/jsteer
 LABEL='U4 step3 guard-requeue'
+# POLITE backoff: the user is developing jsteer live (their VS Code GPU kernel is
+# the oomd competitor). Only launch the fit when the GPU/host is genuinely idle,
+# so we NEVER compete with the user's interactive work -- we just fill the empty
+# windows (overnight, breaks). This wastes no idle GPU time yet never fights the
+# human for their own machine. Thresholds sized for the fit's ~10.5GB footprint.
+GPU_FREE_MIN_MIB=13000   # need >=13GB free (i.e. others using <~11GB) to start
+RAM_AVAIL_MIN_MIB=20000  # need >=20GB host available (oomd triggers on host too)
 while [ ! -f artifacts/u4_loopclose.txt ]; do
   active=$(pueue status --json | jq -r --arg l "$LABEL" \
     '.tasks[] | select((.label // "") | contains($l)) | .status | if type=="object" then keys[0] else . end' \
     | grep -Ec 'Running|Queued|Stashed|Paused')
   if [ "$active" -eq 0 ]; then
-    pueue add \
-      -l "why: $LABEL -- oomd-resilient external requeue of the 4B fit; resolve: resume checkpoint to n_done=400, writes u4_loopclose.txt on success" \
-      -w "$PWD" -o 0 -- bash scripts/u4_step3_retry.sh
-    echo "$(date '+%F %H:%M:%S') requeued fit (was not active)"
+    gpu_free=$(nvidia-smi --query-gpu=memory.free --format=csv,noheader,nounits | head -1)
+    ram_avail=$(free -m | awk '/^Mem:/{print $7}')
+    if [ "$gpu_free" -ge "$GPU_FREE_MIN_MIB" ] && [ "$ram_avail" -ge "$RAM_AVAIL_MIN_MIB" ]; then
+      pueue add \
+        -l "why: $LABEL -- polite idle-window fit of the 4B Jacobian; resolve: resume checkpoint to n_done=400, writes u4_loopclose.txt on success" \
+        -w "$PWD" -o 0 -- bash scripts/u4_step3_retry.sh
+      echo "$(date '+%F %H:%M:%S') GPU idle (free=${gpu_free}MiB, ram=${ram_avail}MiB) -- launched fit"
+    else
+      echo "$(date '+%F %H:%M:%S') user active (gpu_free=${gpu_free}MiB, ram_avail=${ram_avail}MiB) -- backing off"
+    fi
   fi
   sleep 300
 done