From 7515dc27f13dac451b4f05f6b8439b1a271a0de2 Mon Sep 17 00:00:00 2001
From: Anarkis Gaming <serialkicked@gmail.com>
Date: Sun, 19 Oct 2025 16:13:51 +0200
Subject: [PATCH] Fixes #1281 Extended grammar optimization mode would crash if
 TopK sampling is set to zero.

---
 LLama/Sampling/DefaultSamplingPipeline.cs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/LLama/Sampling/DefaultSamplingPipeline.cs b/LLama/Sampling/DefaultSamplingPipeline.cs
index 27a4243c8..77d20e36a 100644
--- a/LLama/Sampling/DefaultSamplingPipeline.cs
+++ b/LLama/Sampling/DefaultSamplingPipeline.cs
@@ -246,7 +246,8 @@ public override LLamaToken Sample(SafeLLamaContextHandle ctx, int index)
                 }
                     
                 // Extended optimization : Apply the grammar to the TopK tokens and check if the selected token is valid
-                if (GrammarOptimization == GrammarOptimizationMode.Extended)
+                // Only run if TopK > 0
+                if (GrammarOptimization == GrammarOptimizationMode.Extended && TopK > 0)
                 {
                     // Calculate a safe TopK value
                     var safeTopK = Math.Min(TopK, nativeAll.Data.Length);