release: 5.2.0

[stainless-app]

Automated Release PR

5.2.0 (2026-01-14)

Full Changelog: v5.1.0...v5.2.0

Features

• client: add helper functions for raw messages (1781a38)

Bug Fixes

• client: add missing serializer options (73bd7dd)
• client: bad deserialize call for void method (a2a5845)
• client: bad reference (9170476)
• client: dictionary type (ad0d8ff)
• client: ensure deep immutability for deep array/dict structures (fda9700)
• client: freeze models on property access (196bf8e)
• client: missing immutable -> readonly conversion (2afcb10)
• client: throw api enum errors as invalid data exception (9bf8de8)
• client: use readonly type for param (5b2c657)

Performance Improvements

• client: add json deserialization caching (fda9700)

Chores

• client: consistently use serializer options (bc7871a)
• client: refactor union instantiation (ebb48fc)
• client: use mutable collections for union deserialization (2d1ab11)
• internal: regenerate SDK with no functional changes (0aed83e)
• internal: regenerate SDK with no functional changes (d7df223)
• internal: use better namespace aliases (b754fec)
• readme: remove beta warning now that we're in ga (1974856)
• remove custom code (0324583)

Refactors

• client: add JsonDictionary identity methods (588abd9)
• internal: JsonElement constant construction (d9577f1)

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[stainless-app]

🤖 Release is at https://github.com/trycourier/courier-csharp/releases/tag/v5.2.0 🌻