diff --git a/single_shot_inference.py b/single_shot_inference.py
index 62d4786f..18d6bcde 100644
--- a/single_shot_inference.py
+++ b/single_shot_inference.py
@@ -1361,6 +1361,13 @@ def main():
         input_ids = [bos, USER_TOKEN]
         input_ids += tokenizer.encode('\n\n' + PROMPT, add_special_tokens=False)
         input_ids.append(ASSISTANT_TOKEN)
+        # DSV4 reasoning model: must prime with ◇ (think_start) after Assistant token.
+        # Without this, the model is out-of-distribution — it expects to be inside a
+        # thinking block but never received the think-start sentinel.
+        # Symptom: degenerate output from step 0 (e.g. "France" instead of "Paris",
+        # looping on newlines/repeated tokens). With ◇, the model generates thinking
+        # content, emits ◇ (think_end), then produces the actual answer.
+        input_ids.append(THINK_START)
         generated = input_ids
     all_tokens = generated.copy()
     print(f"Input: {len(generated)} tokens")