Build advanced reasoning agents with Qwen/Qwen3.5-4B, a specialized AI model optimized for complex logic and chain-of-thought tasks. This model delivers available completely free of charge, native tool calling support, open weights architecture. Access Qwen/Qwen3.5-4B via the SiliconFlow (China) API with up to 66K output tokens.
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Qwen/Qwen3.5-4B by SiliconFlow (China) costs Free per 1M input tokens and Free per 1M output tokens.