AI SDK 3.4

The AI SDK 3.4 release introduces several new features including language model middleware, data stream protocol, structured outputs, multi-step calls, tracing improvements, and mock models for testing. Language model middleware allows developers to intercept and modify language model calls, while the data stream protocol enables use of AI SDK UI with any backend in any programming language. Structured outputs provide object, array, or enum-based output modes, and multi-step calls allow for real-time streaming responses that can interact with tools. Tracing improvements align more closely with OpenTelemetry Semantic Conventions for GenAI operations, and mock providers and test helpers enable unit testing of code without actually calling a language model provider.