fix(core): match DeepSeek provider by model name for sglang/vllm (#3613) (#3620)

Some OpenAI-compatible servers (notably sglang's deepseek-v4 jinja
template) crash on the array form of message content even when it
carries a single text block, with `TypeError: sequence item 0:
expected str instance, list found` at `encoding_dsv4.py:336`.

The DeepSeekOpenAICompatibleProvider already flattens content arrays
into joined strings in buildRequest, but isDeepSeekProvider only
matched on the official api.deepseek.com baseUrl. DeepSeek models
served behind sglang / vllm / ollama / etc. bypass the workaround
and hit the bug.

Extend the matcher to also detect by model name (case-insensitive
substring 'deepseek'), so any OpenAI-compatible endpoint serving a
DeepSeek model picks up the same content-format flattening.

Fixes #3613

Co-authored-by: wenshao <wenshao@U-K7F6PQY3-2157.local>

packages/core/src/core/openaiContentGenerator/provider/deepseek.test.ts

@@ -49,16 +49,41 @@ describe('DeepSeekOpenAICompatibleProvider', () => {
       expect(result).toBe(true);
     });
 
-    it('returns false for non deepseek baseUrl', () => {
+    it('returns false when neither baseUrl nor model match deepseek', () => {
       const config = {
         ...mockContentGeneratorConfig,
         baseUrl: 'https://api.example.com/v1',
+        model: 'gpt-4o',
       } as ContentGeneratorConfig;
 
       const result =
         DeepSeekOpenAICompatibleProvider.isDeepSeekProvider(config);
       expect(result).toBe(false);
     });
+
+    it('returns true for deepseek model on a non-deepseek baseUrl (e.g. sglang) — issue #3613', () => {
+      const config = {
+        ...mockContentGeneratorConfig,
+        baseUrl: 'https://my-sglang.example.com:8000/v1',
+        model: 'deepseek-v4-pro',
+      } as ContentGeneratorConfig;
+
+      const result =
+        DeepSeekOpenAICompatibleProvider.isDeepSeekProvider(config);
+      expect(result).toBe(true);
+    });
+
+    it('matches model name case-insensitively', () => {
+      const config = {
+        ...mockContentGeneratorConfig,
+        baseUrl: 'https://my-vllm.example.com/v1',
+        model: 'DeepSeek-R1',
+      } as ContentGeneratorConfig;
+
+      const result =
+        DeepSeekOpenAICompatibleProvider.isDeepSeekProvider(config);
+      expect(result).toBe(true);
+    });
   });
 
   describe('buildRequest', () => {

packages/core/src/core/openaiContentGenerator/provider/deepseek.ts

@@ -22,8 +22,17 @@ export class DeepSeekOpenAICompatibleProvider extends DefaultOpenAICompatiblePro
     contentGeneratorConfig: ContentGeneratorConfig,
   ): boolean {
     const baseUrl = contentGeneratorConfig.baseUrl ?? '';
+    if (baseUrl.toLowerCase().includes('api.deepseek.com')) {
+      return true;
+    }
 
-    return baseUrl.toLowerCase().includes('api.deepseek.com');
+    // DeepSeek models served behind any OpenAI-compatible endpoint (sglang,
+    // vllm, ollama, etc.) share the same content-format constraint that the
+    // official api.deepseek.com endpoint has. Detect them by model name so
+    // the buildRequest flattening below kicks in.
+    // See https://github.com/QwenLM/qwen-code/issues/3613
+    const model = contentGeneratorConfig.model ?? '';
+    return model.toLowerCase().includes('deepseek');
   }
 
   /**