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Fix media type inference for URLs with query parameters #3501

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8dd4492
chore: Parse the url before inferring type
Nov 21, 2025
0e3c089
test: verify the url handles query strings
Nov 21, 2025
38db162
chore: remove comments
Nov 21, 2025
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40 changes: 22 additions & 18 deletions pydantic_ai_slim/pydantic_ai/messages.py
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@Viicos Viicos Nov 21, 2025

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Why aren't we using the mimetypes stdlib module? mimetypes.guess_type() already parses URLs and the current implementation doesn't take into account case insensitivity, etc.

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@DouweM DouweM Nov 21, 2025

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@Viicos Interestingly we already use that in DocumentUrl._infer_media_type, after checking a bunch of types ourselves :/

@fedexman Can you see if we can use mimetypes.guess_type() for all of these?

The method can be changed to just return str rather than XMediaType, as I don't think that type is used on any public fields.

Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@
from os import PathLike
from pathlib import Path
from typing import TYPE_CHECKING, Annotated, Any, Literal, TypeAlias, cast, overload
from urllib.parse import urlparse

import pydantic
import pydantic_core
Expand Down Expand Up @@ -228,21 +229,22 @@ def __init__(

def _infer_media_type(self) -> VideoMediaType:
"""Return the media type of the video, based on the url."""
if self.url.endswith('.mkv'):
path = urlparse(self.url).path
if path.endswith('.mkv'):
return 'video/x-matroska'
elif self.url.endswith('.mov'):
elif path.endswith('.mov'):
return 'video/quicktime'
elif self.url.endswith('.mp4'):
elif path.endswith('.mp4'):
return 'video/mp4'
elif self.url.endswith('.webm'):
elif path.endswith('.webm'):
return 'video/webm'
elif self.url.endswith('.flv'):
elif path.endswith('.flv'):
return 'video/x-flv'
elif self.url.endswith(('.mpeg', '.mpg')):
elif path.endswith(('.mpeg', '.mpg')):
return 'video/mpeg'
elif self.url.endswith('.wmv'):
elif path.endswith('.wmv'):
return 'video/x-ms-wmv'
elif self.url.endswith('.three_gp'):
elif path.endswith('.three_gp'):
return 'video/3gpp'
# Assume that YouTube videos are mp4 because there would be no extension
# to infer from. This should not be a problem, as Gemini disregards media
Expand Down Expand Up @@ -308,17 +310,18 @@ def _infer_media_type(self) -> AudioMediaType:
References:
- Gemini: https://ai.google.dev/gemini-api/docs/audio#supported-formats
"""
if self.url.endswith('.mp3'):
path = urlparse(self.url).path
if path.endswith('.mp3'):
return 'audio/mpeg'
if self.url.endswith('.wav'):
if path.endswith('.wav'):
return 'audio/wav'
if self.url.endswith('.flac'):
if path.endswith('.flac'):
return 'audio/flac'
if self.url.endswith('.oga'):
if path.endswith('.oga'):
return 'audio/ogg'
if self.url.endswith('.aiff'):
if path.endswith('.aiff'):
return 'audio/aiff'
if self.url.endswith('.aac'):
if path.endswith('.aac'):
return 'audio/aac'

raise ValueError(
Expand Down Expand Up @@ -367,13 +370,14 @@ def __init__(

def _infer_media_type(self) -> ImageMediaType:
"""Return the media type of the image, based on the url."""
if self.url.endswith(('.jpg', '.jpeg')):
path = urlparse(self.url).path
if path.endswith(('.jpg', '.jpeg')):
return 'image/jpeg'
elif self.url.endswith('.png'):
elif path.endswith('.png'):
return 'image/png'
elif self.url.endswith('.gif'):
elif path.endswith('.gif'):
return 'image/gif'
elif self.url.endswith('.webp'):
elif path.endswith('.webp'):
return 'image/webp'
else:
raise ValueError(
Expand Down
72 changes: 72 additions & 0 deletions tests/test_messages.py
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Original file line number Diff line number Diff line change
Expand Up @@ -333,6 +333,78 @@ def test_video_url_invalid():
VideoUrl('foobar.potato').media_type


@pytest.mark.parametrize(
'url,media_type,format',
[
pytest.param(
'https://example.com/video.mp4?query=param',
'video/mp4',
'mp4',
id='mp4_with_query',
),
pytest.param(
'https://example.com/video.webm?X-Amz-Algorithm=AWS4-HMAC-SHA256',
'video/webm',
'webm',
id='webm_with_aws_params',
),
],
)
def test_video_url_with_query_parameters(url: str, media_type: str, format: str):
"""Test that VideoUrl correctly infers media type from URLs with query parameters (e.g., presigned URLs)."""
video_url = VideoUrl(url)
assert video_url.media_type == media_type
assert video_url.format == format


@pytest.mark.parametrize(
'url,media_type,format',
[
pytest.param(
'https://example.com/audio.mp3?query=param',
'audio/mpeg',
'mp3',
id='mp3_with_query',
),
pytest.param(
'https://example.com/audio.wav?X-Amz-Algorithm=AWS4-HMAC-SHA256',
'audio/wav',
'wav',
id='wav_with_aws_params',
),
],
)
def test_audio_url_with_query_parameters(url: str, media_type: str, format: str):
"""Test that AudioUrl correctly infers media type from URLs with query parameters (e.g., presigned URLs)."""
audio_url = AudioUrl(url)
assert audio_url.media_type == media_type
assert audio_url.format == format


@pytest.mark.parametrize(
'url,media_type,format',
[
pytest.param(
'https://example.com/image.png?query=param',
'image/png',
'png',
id='png_with_query',
),
pytest.param(
'https://example.com/image.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256',
'image/jpeg',
'jpeg',
id='jpg_with_aws_params',
),
],
)
def test_image_url_with_query_parameters(url: str, media_type: str, format: str):
"""Test that ImageUrl correctly infers media type from URLs with query parameters (e.g., presigned URLs)."""
image_url = ImageUrl(url)
assert image_url.media_type == media_type
assert image_url.format == format


def test_thinking_part_delta_apply_to_thinking_part_delta():
"""Test lines 768-775: Apply ThinkingPartDelta to another ThinkingPartDelta."""
original_delta = ThinkingPartDelta(
Expand Down