diff --git a/ini/host_stream.ini b/ini/host_stream.ini
index 5ce55ab..e164066 100644
--- a/ini/host_stream.ini
+++ b/ini/host_stream.ini
@@ -19,7 +19,8 @@ GetImageBufMode = 0         # 0: block mode 1: non-block mode
 RoiEnable = 0               # Enable ROI for nnm detect
 RoiX = 0                    # ROI start x
 RoiY = 0                    # ROI start y
-DrawBoxEnable = 0           # draw object bounding box on stream0 (also enables STDC seg overlay)
+DrawBoxEnable = 1           # draw object bounding box on stream0 (also enables STDC seg overlay)
+SegOverlayEnable = 0        # 0: outline only, 1: also paint per-class colour overlay (requires DrawBoxEnable=1)
 OnlyPerson = 1              # only draw person bounding box when DrawBoxEnable
                             #(so far for yolo only, JobId = 11)
 DrawOnResize = 0;           # If InferenceStream is 0. This setting needs to be enabled. The box will be drawn on all resize streams.
diff --git a/src/host_stream/kdp2_host_stream.c b/src/host_stream/kdp2_host_stream.c
index 3b2984b..5a061ba 100644
--- a/src/host_stream/kdp2_host_stream.c
+++ b/src/host_stream/kdp2_host_stream.c
@@ -99,6 +99,7 @@ float g_fHeightRatio = 1.0;
 EIS_T g_tEis;
 unsigned int g_dwDrawBoxType = 0; //! 0: isp primary mask, 1: dma
 static unsigned int g_dwDrawOnResize = 0;
+extern unsigned int g_dwSegOverlayEnable; /* defined in kp_firmware.c */
 
 int g_iTerminate = 0;
 bool _blRecvRunning = true;
@@ -863,8 +864,9 @@ void* kdp2_host_stream_draw_box(void *arg)
             need_flush = 1;
         }
 
-        /* Paint STDC segmentation colour overlay (50% alpha blend into YM12) */
-        if (g_stdc_seg_w > 0) {
+        /* Paint STDC segmentation colour overlay (50% alpha blend into YM12).
+         * Requires SegOverlayEnable=1 in host_stream.ini (default 0 = outline only). */
+        if (g_dwSegOverlayEnable && g_stdc_seg_w > 0) {
             stdc_paint_seg_overlay(tWriterSsmBuffer.buffer, &vsrc_ssm_reader_info,
                                    dwWidth, dwHeight);
             need_flush = 1;
diff --git a/src/host_stream/kp_firmware.c b/src/host_stream/kp_firmware.c
index 0e08879..5bb4c23 100644
--- a/src/host_stream/kp_firmware.c
+++ b/src/host_stream/kp_firmware.c
@@ -77,6 +77,7 @@ unsigned int g_dwVocEnable = 0;
 unsigned int g_dwVocPixFmt = 0;
 unsigned int g_dwOnlyPerson = 0;
 unsigned int g_dwDrawBoxEnable = 0;
+unsigned int g_dwSegOverlayEnable = 0; /* 1: paint per-class colour overlay; 0: outline only */
 unsigned int g_verbose_log = 0;    /* 0=quiet, 1=per-frame class ratio log (web UI toggle) */
 
 bool _blMainStanby = true;
@@ -154,6 +155,7 @@ int loadConfig(HOST_STREAM_INIT_OPT_T* pHostStreamInit)
 	pHostStreamInit->dwOnlyPerson = iniparser_getint(ini, "nnm:OnlyPerson", 0);
     g_dwOnlyPerson = pHostStreamInit->dwOnlyPerson;
     g_verbose_log  = (unsigned int)iniparser_getint(ini, "nnm:verbose_log", 0);
+    g_dwSegOverlayEnable = (unsigned int)iniparser_getint(ini, "nnm:SegOverlayEnable", 0);
     pHostStreamInit->dwDrawOnResize = iniparser_getint(ini, "nnm:DrawOnResize", 0);
     if (pHostStreamInit->bDrawBoxEnable && (pHostStreamInit->dwInferenceStream == 0) && (pHostStreamInit->dwDrawOnResize == 0)) {
         pHostStreamInit->dwDrawOnResize = 1;