diff --git a/nodes/decklinkin/main.cpp b/nodes/decklinkin/main.cpp
index cf1dd0f..ed5e06d 100644
--- a/nodes/decklinkin/main.cpp
+++ b/nodes/decklinkin/main.cpp
@@ -34,6 +34,7 @@ class DeckLinkInNode : public dmf::NodeBase {
         log("Detected: %dx%d @ %d/%d fps", vi.width, vi.height, vi.fps_num, vi.fps_den);
 
         // --- Video writer ---
+        if (!config().contains("video_flow_id")) { log("no video output connected — exiting"); return; }
         const auto  video_flow_info = config().at("video_flow_id");
         const auto  video_flow_id   = video_flow_info.at("id").get<std::string>();
         const int   width   = video_flow_info.value("width",   vi.width);
diff --git a/nodes/ndiin/main.cpp b/nodes/ndiin/main.cpp
index 71196bf..387bcbc 100644
--- a/nodes/ndiin/main.cpp
+++ b/nodes/ndiin/main.cpp
@@ -27,6 +27,7 @@ class NDIInNode : public dmf::NodeBase {
         }
 
         // --- video flow ---
+        if (!config().contains("video_flow_id")) { log("no video output connected — exiting"); return; }
         const auto video_flow_info = config().at("video_flow_id");
         const auto video_flow_id   = video_flow_info.at("id").get<std::string>();
         const int  width           = video_flow_info.value("width",   src.width);
diff --git a/nodes/testpattern/main.cpp b/nodes/testpattern/main.cpp
index 84ca0fa..bbe1b26 100644
--- a/nodes/testpattern/main.cpp
+++ b/nodes/testpattern/main.cpp
@@ -10,6 +10,7 @@
 class TestPatternNode : public dmf::NodeBase {
     void run() override {
         // --- video flow ---
+        if (!config().contains("video_flow_id")) { log("no video output connected — exiting"); return; }
         const auto flow_info = config().at("video_flow_id");
         const auto flow_id   = flow_info.at("id").get<std::string>();
         const int  width     = flow_info.value("width",   1920);