diff --git a/image_analysis/bragg_integration/BraggIntegrationEngine.cpp b/image_analysis/bragg_integration/BraggIntegrationEngine.cpp
index 3fd804a0..07dbf6d3 100644
--- a/image_analysis/bragg_integration/BraggIntegrationEngine.cpp
+++ b/image_analysis/bragg_integration/BraggIntegrationEngine.cpp
@@ -109,9 +109,9 @@ BraggIntegrationEngine::BraggIntegrationEngine(const DiffractionExperiment &expe
     // n_kern is the largest row BraggStencilKernelIndex can select, plus one.
     r_max = std::hypot(std::max<double>(beam_x, static_cast<double>(xpixel) - beam_x),
                        std::max<double>(beam_y, static_cast<double>(ypixel) - beam_y));
-    const float grow_max = (bkg_radial || bkg_radial_auto)
-                               ? BraggStencilGrow_px(static_cast<float>(r_max), stencil)
-                               : 0.0f;
+    bkg_radial_built = bkg_radial || bkg_radial_auto;
+    const float grow_max = bkg_radial_built ? BraggStencilGrow_px(static_cast<float>(r_max), stencil)
+                                            : 0.0f;
     n_kern = static_cast<int>(std::lround(grow_max)) + 1;
     // Every row must fit: the last one is built at grow = n_kern - 1, which rounding can put just
     // above grow_max.
diff --git a/image_analysis/bragg_integration/BraggIntegrationEngine.h b/image_analysis/bragg_integration/BraggIntegrationEngine.h
index f5bf14cd..7deca572 100644
--- a/image_analysis/bragg_integration/BraggIntegrationEngine.h
+++ b/image_analysis/bragg_integration/BraggIntegrationEngine.h
@@ -156,6 +156,7 @@ protected:
     // radius. What an elongated ring rules out is one kernel for ALL of them, not the average.
     bool  bkg_radial = false;
     bool  bkg_radial_auto = false;   // settings left it unset: decide per image from the ice score
+    bool  bkg_radial_built = false;  // the kernel table was sized for the rings this engine uses
     int   k_off = 0;                 // index of offset 0 within one kernel
     int   k_len = 0;                 // entries per kernel
     int   n_kern = 1;                // kernels in the table (1 = circular stencil)
@@ -188,6 +189,10 @@ public:
 
     // Turn the radial background correction on or off for the images that follow. The caller owns
     // the decision; in the auto mode the analysis sets it per image from that image's ice score.
-    void BackgroundRadial(bool on) { bkg_radial = on; }
+    //
+    // It cannot be raised on an engine the constructor did not build the kernel table for: that
+    // table would hold a single CIRCULAR kernel for rings that may be elongated, and on the GPU the
+    // radial buffers were never allocated, so the CPU would correct and the GPU would not.
+    void BackgroundRadial(bool on) { bkg_radial = on && bkg_radial_built; }
     [[nodiscard]] bool IsBackgroundRadialAuto() const { return bkg_radial_auto; }
 };
diff --git a/image_analysis/bragg_integration/BraggStencil.h b/image_analysis/bragg_integration/BraggStencil.h
index 5e60bd85..d4191988 100644
--- a/image_analysis/bragg_integration/BraggStencil.h
+++ b/image_analysis/bragg_integration/BraggStencil.h
@@ -59,7 +59,7 @@ struct BraggStencilParams {
     float r2 = 6.0f, r3 = 10.0f;
     float bw_sigma = 0.0f;    // radial streak per pixel of radius (bandwidth sigma, dimensionless)
     float k_sigma = 0.0f;     // radial sigmas to push the ring out by; 0 = the old circular stencil
-    float max_grow = 0.0f;    // hard cap on the radial growth [px]. 0 disables growth, not the cap.
+    float max_grow = 0.0f;    // hard cap on the radial growth [px]; <= 0 means uncapped
 };
 
 // One reflection's stencil, in its own radial/tangential frame.
@@ -76,9 +76,10 @@ struct BraggStencil {
 // so the stencil and the radial-background kernel table agree on what "grown by this much" means.
 BRAGG_STENCIL_HD float BraggStencilGrow_px(float Rpx, const BraggStencilParams &p) {
     if (!(p.k_sigma > 0.0f)) return 0.0f;
-    // The cap bounds what a mis-declared bandwidth can do to the bounding box.
+    // The cap bounds what a mis-declared bandwidth can do to the bounding box. A caller that
+    // forgets to set it gets the uncapped growth rather than silently no growth at all.
     const float grow = p.k_sigma * p.bw_sigma * Rpx;
-    return grow > p.max_grow ? p.max_grow : grow;
+    return (p.max_grow > 0.0f && grow > p.max_grow) ? p.max_grow : grow;
 }
 
 BRAGG_STENCIL_HD BraggStencil MakeBraggStencil(float px_x, float px_y, const BraggStencilParams &p) {