What's Changed
- [NA] [FE] Add invite users popover to collaborators tab by @anastasiapyzhik in #4485
- [OPIK-3248] [SDK] Enforce strict OpenAI-like messages structure validation for chat messages by @petrotiurin in #4493
- [OPIK-3529][FE][BE] Support for Gemini 3 Flash in playground and online scoring by @AndreiCautisanu in #4492
- [OPIK-3530] [SDK] Fix Hierarchical optimizer recreating optimizations by @ldaugusto in #4505
- [NA] [DOCS] Add test requirements quickstart by @petrotiurin in #4510
- [OPIK-3502] [BE] Add opikApiKey to CORS allowed headers and bump optimizer by @ldaugusto in #4512
Full Changelog: 1.9.58...1.9.59