diff --git a/crates/shaders/src/cpu/flatten.rs b/crates/shaders/src/cpu/flatten.rs
index cce140dc9..bd501d396 100644
--- a/crates/shaders/src/cpu/flatten.rs
+++ b/crates/shaders/src/cpu/flatten.rs
@@ -333,7 +333,7 @@ fn flatten_euler(
                 let n_frac = scaled_int;
                 (n_frac, EspcRobust::Normal)
             };
-            let n = (n_frac * scale_multiplier).ceil().max(1.0);
+            let n = (n_frac * scale_multiplier).ceil().clamp(1.0, 100.0);
 
             // Flatten line segments
             log!("@@@   loop: lines: {n}");
diff --git a/shader/flatten.wgsl b/shader/flatten.wgsl
index 80da1880c..9371061d1 100644
--- a/shader/flatten.wgsl
+++ b/shader/flatten.wgsl
@@ -434,7 +434,10 @@ fn flatten_euler(
                 let integrand_peak = sqrt(abs(k_peak * (k_peak * dist_scaled + 1.0)));
                 n_frac = integral * integrand_peak / a;
             }
-            let n = max(ceil(n_frac * scale_multiplier), 1.0);
+            // Bound number of subdivisions to a reasonable number when the scale is huge.
+            // This may give slightly incorrect rendering but avoids hangs.
+            // TODO: aggressively cull to viewport
+            let n = clamp(ceil(n_frac * scale_multiplier), 1.0, 100.0);
             for (var i = 0u; i < u32(n); i++) {
                 var lp1: vec2f;
                 if i + 1u == u32(n) && t1 == 1.0 {