Build advanced reasoning agents with gpt-oss-120b (free), 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 gpt-oss-120b (free) via the OpenRouter API with up to 33K output tokens.
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gpt-oss-120b (free) by OpenRouter costs Free per 1M input tokens and Free per 1M output tokens.