From 7fbd44cbe0a90b9c8fd3a94a0f0401ac4b1bc719 Mon Sep 17 00:00:00 2001
From: aoshen02 <aoshen@inferact.ai>
Date: Sat, 5 Sep 2026 18:31:04 +0800
Subject: [PATCH] [Bugfix][DSv4] Seed the -1 sentinel in the prefill sparse
 index workspace (#55299)

Signed-off-by: aoshen02 <aoshen02@users.noreply.github.com>
Co-authored-by: aoshen02 <aoshen02@users.noreply.github.com>
---
 vllm/models/deepseek_v4/common/ops/cache_utils.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/vllm/models/deepseek_v4/common/ops/cache_utils.py b/vllm/models/deepseek_v4/common/ops/cache_utils.py
index 6838ef928d..fefc10ec35 100644
--- a/vllm/models/deepseek_v4/common/ops/cache_utils.py
+++ b/vllm/models/deepseek_v4/common/ops/cache_utils.py
@@ -561,6 +561,7 @@ def combine_topk_swa_indices(
         )
     else:
         combined_indices, combined_lens = out
+        combined_indices.fill_(-1)
 
     _COMBINE_TOPK_SWA_INDICES_KERNEL(
         combined_indices,