GPT-OSS 20B/120B models available; 131K context, structured outputs

Added GPT-OSS 20B and GPT-OSS 120B are OpenAI's open-source Mixture-of-Experts models performing on par with o4-mini/o3-mini, with reasoning, built-in browser search and code execution, and structured outputs support.

Key Features: 131K context window; 32K max output tokens; ~1000+/~500+ TPS; MoE with 32/128 experts respectively; surpasses o4-mini on many benchmarks.

Performance (20B): 85.3% MMLU, 60.7% SWE-Bench Verified, 98.7% AIME 2025, 75.7% avg MMMLU. Performance (120B): 90.0% MMLU, 62.4% SWE-Bench Verified, 57.6% HealthBench Realistic, 81.3% avg MMMLU.

Also added: Responses API (Beta) — fully compatible with OpenAI's Responses API, supporting text/image inputs, stateful conversations, and function calling.

Changed Python SDK v0.30.0/v0.31.0, TypeScript SDK v0.27.0 — added reasoning_effort (high/medium/low) for GPT-OSS models; added browser_search and code_interpreter tool types; added optional include_reasoning boolean for chat completions.