OpenAI Agents SDK 0.20.0 changes the default model and takes a breaking MCP v2 dependency.

Released early August 11, the implicit default model becomes gpt-5.6-luna, and local MCP support now spans Python SDK v1 and v2 across stdio, SSE, and Streamable HTTP. If you have custom MCP HTTP auth or client factories, you match the installed MCP major version's HTTP types or pin mcp<2. Also adds RunState.add_input() for staging durable user input before a resumed model call, plus sandbox hardening including explicit credential-exposure acknowledgements on mounts.