diff --git a/open-sse/handlers/responseSanitizer.ts b/open-sse/handlers/responseSanitizer.ts
index f7cbb300fc..015f79c234 100644
--- a/open-sse/handlers/responseSanitizer.ts
+++ b/open-sse/handlers/responseSanitizer.ts
@@ -27,8 +27,10 @@ const ALLOWED_RESPONSES_USAGE_FIELDS = new Set([
 
 type JsonRecord = Record<string, unknown>;
 
+const DEEPSEEK_V4_SANITIZER_MODEL_PATTERN = /deepseek[-/]v4/i;
+
 function isDeepSeekV4Model(model: unknown): boolean {
-  return typeof model === "string" && /deepseek[-/]v4/i.test(model);
+  return typeof model === "string" && DEEPSEEK_V4_SANITIZER_MODEL_PATTERN.test(model);
 }
 
 function toRecord(value: unknown): JsonRecord | null {
diff --git a/open-sse/translator/index.ts b/open-sse/translator/index.ts
index 49fb8add0e..d74947c435 100644
--- a/open-sse/translator/index.ts
+++ b/open-sse/translator/index.ts
@@ -111,7 +111,7 @@ function isDeepSeekReplayTarget(provider: unknown, model: unknown): boolean {
   const normalizedModel = String(model ?? "")
     .trim()
     .toLowerCase();
-  return normalizedProvider === "deepseek" || normalizedModel.includes("deepseek");
+  return normalizedProvider === "deepseek" || /(^|\/)deepseek/i.test(normalizedModel);
 }
 
 /** @param options.normalizeToolCallId - When true, use 9-char tool call ids (e.g. Mistral); when false, leave ids as-is */