Build advanced reasoning agents with GPT-5 Nano, 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. Access GPT-5 Nano via the OpenCode Zen API with up to 128K output tokens.
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GPT-5 Nano by OpenCode Zen costs Free per 1M input tokens and Free per 1M output tokens. Cached reads cost Free per 1M tokens.