func TestProviderChat_PreservesReasoningContentInHistory(t *testing.T) {
    var requestBody map[string]any

    server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        if err := json.NewDecoder(r.Body).Decode(&requestBody); err != nil {
            http.Error(w, err.Error(), http.StatusBadRequest)
            return
        }
        resp := map[string]any{
            "choices": []map[string]any{
                {"message": map[string]any{"content": "ok"}, "finish_reason": "stop"},
            },
        }
        w.Header().Set("Content-Type", "application/json")
        json.NewEncoder(w).Encode(resp)
    }))
    defer server.Close()

    p := NewProvider("key", server.URL, "")
    
    // Send conversation history with reasoning_content
    messages := []Message{
        {Role: "user", Content: "What is 1+1?"},
        {Role: "assistant", Content: "2", ReasoningContent: "Let me think... 1+1=2"},
        {Role: "user", Content: "What about 2+2?"},
    }
    
    _, err := p.Chat(t.Context(), messages, nil, "kimi-k2.5", nil)
    if err != nil {
        t.Fatalf("Chat() error = %v", err)
    }

    // Verify reasoning_content is preserved in the request
    reqMessages := requestBody["messages"].([]any)
    assistantMsg := reqMessages[1].(map[string]any)
    if assistantMsg["reasoning_content"] != "Let me think... 1+1=2" {
        t.Errorf("reasoning_content not preserved in request: got %v", assistantMsg["reasoning_content"])
    }
}