diff --git a/firmware/lib/cv/cv.cpp b/firmware/lib/cv/cv.cpp
index 552b84d..ca4186c 100644
--- a/firmware/lib/cv/cv.cpp
+++ b/firmware/lib/cv/cv.cpp
@@ -17,6 +17,8 @@ void cv_reset_counts(CVState& state) {
 
 struct Point { int x, y; };
 
+// Note: queue may grow to CV_PIXELS entries (~72KB) on large blobs.
+// Requires PSRAM (enabled via -DBOARD_HAS_PSRAM in platformio.ini).
 // BFS flood fill. Marks visited pixels (sets fg to 0). Returns {-1,-1} if blob < CV_MIN_BLOB_PX.
 static std::pair<float,float> extract_blob(uint8_t* fg, int start_x, int start_y) {
     std::vector<Point> queue;
@@ -49,7 +51,7 @@ static std::pair<float,float> extract_blob(uint8_t* fg, int start_x, int start_y
 
 static std::vector<std::pair<float,float>> find_centroids(const uint8_t* fg) {
     std::vector<std::pair<float,float>> result;
-    uint8_t fg_copy[CV_PIXELS];
+    static uint8_t fg_copy[CV_PIXELS];  // static to avoid 9KB stack allocation
     memcpy(fg_copy, fg, CV_PIXELS);
 
     for (int y = 0; y < CV_H; y++) {