[Bug]: Unexpected field as JSON String instead of number

[jpalvarezl]

Describe the bug

While generating the client library for the Azure OpenAI Realtime Audio client library, I noticed that the fields prefix_padding_ms and silence_duration_ms are serialized as JSON Strings, but the service actually expects a JSON number, failing the request.

The TSP definition for the model in question can be found here: https://github.com/joseharriaga/openai-in-typespec/blob/0cd29e191a157fe4356fed68707a2c43a5f728be/.typespec/realtime/custom.tsp#L106-L115

We are fully aware that we might not be using duration correctly. So this could very well be a spec definition issue from our side.

Reproduction

• Re-add the @Generated annotation to the fields prefixPaddingMs and silenceDurationMs in RealtimeServerVadTurnDetection class as well as to the toJson method.
• The member variables should now be generated as Java Duration types
• toJson will try to serialize these as String using jsonWriter.writeStringField

Checklist

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• The provided reproduction is a minimal reproducible example of the bug.