This script is used to reproduce the bug that existed before where `pydantic_ai._mcp.map_from_pai_messages()` was calling `base64.b64decode(chunk.data)` on `chunk.data: bytes`

pydantic-ai-mcp-decoding-bytes.py

#!/usr/bin/env python
"""Quick script to verify base64 encoding/decoding for MCP content using actual classes."""

from pydantic_ai._mcp import map_from_pai_messages
from pydantic_ai.messages import BinaryContent, ModelRequest, UserPromptPart

# Test image content
raw_image_bytes = b'some image data here'
image_message = ModelRequest(
    parts=[
        UserPromptPart(
            content=[BinaryContent(data=raw_image_bytes, media_type='image/png')]
        )
    ]
)

print('=== Testing map_from_pai_messages with image content ===')
print(f'Input BinaryContent.data: {raw_image_bytes!r}')
try:
    _, sampling_msgs = map_from_pai_messages([image_message])
    print(f'Success! Content: {sampling_msgs[0].content}')
except Exception as e:
    print(f'ERROR: {type(e).__name__}: {e}')

print()

# Test audio content
raw_audio_bytes = b'some audio data here'
audio_message = ModelRequest(
    parts=[
        UserPromptPart(
            content=[BinaryContent(data=raw_audio_bytes, media_type='audio/wav')]
        )
    ]
)

print('=== Testing map_from_pai_messages with audio content ===')
print(f'Input BinaryContent.data: {raw_audio_bytes!r}')
try:
    _, sampling_msgs = map_from_pai_messages([audio_message])
    print(f'Success! Content: {sampling_msgs[0].content}')
except Exception as e:
    print(f'ERROR: {type(e).__name__}: {e}')