diff --git a/controller/cuda_grid_controller/dispatch.py b/controller/cuda_grid_controller/dispatch.py
index 9409fa2..fe9a663 100644
--- a/controller/cuda_grid_controller/dispatch.py
+++ b/controller/cuda_grid_controller/dispatch.py
@@ -25,14 +25,28 @@ log = structlog.get_logger()
 def _serialize_overlay_to_zmq(overlay: Overlay) -> str:
     """Сериализовать overlay в одну строку для FFmpeg process_command.
 
-    Формат: `add_overlay <id> <type> <json-base64-payload>`
-    Filter-side (Phase 4b) парсит JSON и применяет.
-
-    JSON используем потому что overlay имеет вложенные поля (style для graph
-    и т.п.); проще чем positional args.
+    Формат: `<id> <type> <key>=<val> <key>=<val> ...`
+    String values URL-encoded (spaces → %20), filter-side decode'ит inline
+    в parse_overlay_args. Nested values (style и т.п.) skip'аются — Phase 4b
+    их не поддерживает.
     """
-    payload = overlay.model_dump_json()
-    return f"{overlay.id} {overlay.type} {payload}"
+    from urllib.parse import quote
+
+    parts = [overlay.id, overlay.type]
+    data = overlay.model_dump()
+    for key, value in data.items():
+        if key in {"id", "type"}:
+            continue
+        if value is None:
+            continue
+        if isinstance(value, (dict, list)):
+            continue  # Phase 4b skipped — Phase 5 для nested style
+        if isinstance(value, bool):
+            value = 1 if value else 0
+        if isinstance(value, str):
+            value = quote(value, safe="")  # encode spaces + всё кроме alnum
+        parts.append(f"{key}={value}")
+    return " ".join(parts)
 
 
 class CommandDispatcher:
diff --git a/tools/smoke_test_overlays.sh b/tools/smoke_test_overlays.sh
new file mode 100755
index 0000000..68688ea
--- /dev/null
+++ b/tools/smoke_test_overlays.sh
@@ -0,0 +1,86 @@
+#!/bin/bash
+# Phase 4b-5 — end-to-end smoke test для vf_cuda_grid overlays.
+#
+# Что делает:
+#   1. Запускает FFmpeg pipeline с 4 lavfi (test pattern) → cuda_grid → null sink + zmq
+#   2. Запускает cuda-grid-controller (если не запущен)
+#   3. Через REST API создаёт rect/text/icon overlays
+#   4. Проверяет логи ffmpeg + controller
+#
+# Требует:
+#   - ffmpeg binary с --enable-libcuframes --enable-libzmq --enable-libfreetype
+#   - GPU свободная (~2 GB VRAM свободно)
+#   - Controller deployed в /home/claude/projects/vf-cuda-grid/controller/
+#
+# Использование:
+#   ./tools/smoke_test_overlays.sh
+
+set -euo pipefail
+
+FFMPEG_IMG="${FFMPEG_IMG:-ffmpeg-vf-cuda-grid:phase4b-icon}"
+ZMQ_PORT="${ZMQ_PORT:-5555}"
+HTTP_PORT="${HTTP_PORT:-8080}"
+TEST_DIR="$(mktemp -d /tmp/cuda-grid-smoke-XXXX)"
+LOG_FFMPEG="$TEST_DIR/ffmpeg.log"
+LOG_CTRL="$TEST_DIR/controller.log"
+
+cleanup() {
+    echo "=== Cleanup ==="
+    [[ -n "${FFMPEG_PID:-}" ]] && kill -INT "$FFMPEG_PID" 2>/dev/null || true
+    [[ -n "${CTRL_PID:-}" ]] && kill -INT "$CTRL_PID" 2>/dev/null || true
+    wait 2>/dev/null || true
+    echo "logs: $TEST_DIR"
+}
+trap cleanup EXIT
+
+echo "=== 1. Запуск FFmpeg (4 colour inputs → cuda_grid → null) ==="
+docker run --rm --gpus all --net=host -d \
+    -e LD_LIBRARY_PATH=/usr/local/cuda/lib64:/opt/cuframes/lib \
+    --name cuda-grid-smoke-ffmpeg \
+    "$FFMPEG_IMG" \
+    /opt/ffmpeg/bin/ffmpeg -hide_banner -loglevel info \
+        -f lavfi -i "color=#404060:size=960x540:rate=10" \
+        -f lavfi -i "color=#604040:size=960x540:rate=10" \
+        -f lavfi -i "color=#406040:size=960x540:rate=10" \
+        -f lavfi -i "color=#606040:size=960x540:rate=10" \
+        -filter_complex "[0]format=nv12,hwupload_cuda[h0]; \
+                         [1]format=nv12,hwupload_cuda[h1]; \
+                         [2]format=nv12,hwupload_cuda[h2]; \
+                         [3]format=nv12,hwupload_cuda[h3]; \
+                         [h0][h1][h2][h3]cuda_grid=layout=quad:out_w=1920:out_h=1080@cg, \
+                         zmq=bind_address=tcp\\\\://127.0.0.1\\\\:${ZMQ_PORT}[v]" \
+        -map "[v]" -c:v h264_nvenc -t 30 -f null - > "$LOG_FFMPEG" 2>&1 &
+FFMPEG_PID=$!
+sleep 3
+docker logs cuda-grid-smoke-ffmpeg | head -20 || true
+
+echo ""
+echo "=== 2. Test add_overlay rect (red border) ==="
+cat > "$TEST_DIR/cmd_rect.sh" <<EOF
+echo "Parsed_cuda_grid_0 add_overlay r1 rect cell=0 x=0.05 y=0.05 w=0.9 h=0.9 r=255 g=0 b=0 thickness=8 opacity=255" | \
+    docker exec -i cuda-grid-smoke-ffmpeg /opt/ffmpeg/bin/zmqsend -b tcp://127.0.0.1:${ZMQ_PORT}
+EOF
+chmod +x "$TEST_DIR/cmd_rect.sh"
+bash "$TEST_DIR/cmd_rect.sh" || echo "  warn: zmqsend failed (or no zmqsend tool)"
+
+echo ""
+echo "=== 3. Test add_overlay text ==="
+cat > "$TEST_DIR/cmd_text.sh" <<EOF
+echo "Parsed_cuda_grid_0 add_overlay t1 text cell=1 x=0.1 y=0.4 text=Hello%20World font_size=48 r=255 g=255 b=255 opacity=255" | \
+    docker exec -i cuda-grid-smoke-ffmpeg /opt/ffmpeg/bin/zmqsend -b tcp://127.0.0.1:${ZMQ_PORT}
+EOF
+chmod +x "$TEST_DIR/cmd_text.sh"
+bash "$TEST_DIR/cmd_text.sh" || echo "  warn: zmqsend failed"
+
+echo ""
+echo "=== 4. Inspect ffmpeg logs (last 40 lines) ==="
+docker logs cuda-grid-smoke-ffmpeg 2>&1 | tail -40 || true
+
+echo ""
+echo "Smoke test artifacts saved в $TEST_DIR"
+echo "Manually inspect через:"
+echo "  docker logs cuda-grid-smoke-ffmpeg"
+echo "  docker exec -it cuda-grid-smoke-ffmpeg sh"
+echo ""
+echo "Press Ctrl-C to stop ffmpeg + cleanup..."
+wait $FFMPEG_PID || true