diff --git a/tools/autoplay-batch.sh b/tools/autoplay-batch.sh
index c8746350..eb45ee2c 100755
--- a/tools/autoplay-batch.sh
+++ b/tools/autoplay-batch.sh
@@ -140,6 +140,19 @@ echo "Parallel: $PARALLEL concurrent seed(s)"
 echo "Safety timeout: ${SAFETY_TIMEOUT}s per game"
 echo "============================================================"
 
+# p1-45: Rebuild GDExtension before every local batch so the .so is never stale.
+# Remote mode delegates to run_ap3.sh on the remote host, which is expected to
+# have a fresh build already (or the caller ran build-gdext.sh manually).
+# Uses a timestamped CARGO_TARGET_DIR to avoid collisions on multi-tenant hosts.
+if [ -z "$AUTOPLAY_HOST" ]; then
+    echo "--- p1-45: rebuilding GDExtension before batch (CARGO_TARGET_DIR isolation) ---"
+    MC_BUILD_STAMP="$(date +%s)"
+    export CARGO_TARGET_DIR="/tmp/mc-build-${MC_BUILD_STAMP}/target"
+    (cd "$PROJECT_DIR/src/simulator" && bash build-gdext.sh)
+    unset CARGO_TARGET_DIR
+    echo "--- GDExtension rebuild complete ---"
+fi
+
 # Start the MCTS service (idempotent — no-op if already running).
 # Runs only for local batches; remote batches rely on the remote host's
 # run-services.sh invocation (or service already running on apricot).