Python: Bug: SendEvents Enum Causes Pydantic Literal Validation Error on macOS – Requires .value for Compatibility

[mohaom]

Describe the bug
When using the SDK to send a RealtimeAudioEvent, the code fails due to a Pydantic validation error. The event_type is passed as an instance of SendEvents.INPUT_AUDIO_BUFFER_APPEND, which is an Enum, but downstream validation requires a literal string ("input_audio_buffer.append"). This causes a literal_error

The issue does not occur on Windows with Semantic-kernel 1.27.1, but fails on macOS with both 1.27.1 and latest version of SDK Semantic-kernel 1.27.2, likely due to stricter validation or platform differences in how values are handled or validated.

To Reproduce
Steps to reproduce the behavior:
1. Create a RealtimeAudioEvent with AudioContent, passing base64-encoded audio data as data.
2. Call realtime_client.send(event) on macOS.
3. Internally, the send() method calls _create_openai_realtime_client_event(...) with event_type=SendEvents.INPUT_AUDIO_BUFFER_APPEND.
4. throws a validation error:

error: Input should be 'input_audio_buffer.append' [type=literal_error, input_value=<SendEvents.INPUT_AUDIO_B...ut_audio_buffer.append'>, input_type=SendEvents]
    For further information visit https://errors.pydantic.dev/2.8/v/literal_error
2025-04-08 23:49:57,521 - ERROR - Error processing WebSocket message: 1 validation error for InputAudioBufferAppendEvent
type

Expected behavior
The SDK should work consistently across platforms and not raise validation errors when using SendEvents.INPUT_AUDIO_BUFFER_APPEND, since it inherits from str. Pydantic should recognize it as a valid literal match, or the Enum’s .value should be passed to avoid strict type mismatch.

Screenshots
N/A

Platform

• Language: Python
• Source: pip package semantic-kernel==1.27.2
• AI model: N/A
• IDE: VS Code
• OS: macOS

Additional context
Although SendEvents inherits from str, passing the Enum directly still fails validation under stricter enforcement (as observed on macOS).

• Solution that fixed the issue on macOS:
  Changing this line in the internal send() method:

  `event_type = SendEvents.INPUT_AUDIO_BUFFER_APPEND`
  to:
  `event_type = SendEvents.INPUT_AUDIO_BUFFER_APPEND.value`
  

  This ensures that a raw string ("input_audio_buffer.append") is passed, which satisfies the Literal[...] type check enforced by Pydantic.

  Recommendation: update internal calls to always use .value when passing SendEvents values into anything validated with Pydantic.

[mohaom]

After further investigation, the root cause turned out to be a mismatch between the Python environment configured in VS Code and the one actually used to run the code. VS Code itself was still using the globally installed Python interpreter, which had an outdated version of semantic-kernel. (1.72.1)

Upgrading the global environment to match version 1.72.2 resolved the issue on macOS.