[Feature]: Support passthrough for generated file download in Gemini

[ishaan-jaff]

[Feature]: Support passthrough for generated file download in Gemini
LiteLLM currently lacks support for passthrough functionality for generated file downloads in Gemini.

1. Use LiteLLM in Gemini environment.
2. Attempt to download a generated file.
3. Observe that passthrough support is not available, leading to potential issues with file handling.
   Implement passthrough support for generated file downloads in LiteLLM within Gemini.
   Supporting passthrough would improve file download handling and user experience in Gemini. No specific error messages provided.

[TeddyAmkie]

This is the same underlying problem as #13557 (Veo video downloads) — LiteLLM passthrough can issue generation requests, but returns 302 error and cannot download.

Script to Repro

`BASE_URL="https://litellm-REDACT/gemini/v1beta"
GEMINI_API_KEY="sk-LITELLM-REDACT"

Send request to generate video and capture the operation name into a variable.

operation_name=$(curl -s "${BASE_URL}/models/veo-3.0-generate-preview:predictLongRunning"
-H "x-goog-api-key: $GEMINI_API_KEY"
-H "Content-Type: application/json"
-X "POST"
-d '{
"instances": [{
"prompt": "A close up of two people staring at a cryptic drawing on a wall, torchlight flickering. A man murmurs, "This must be it. That'''s the secret code." The woman looks at him and whispering excitedly, "What did you find?""
}
]
}' | jq -r .name)
echo "Operation started with name: ${operation_name}"

Poll the operation status until the video is ready

while true; do

Get the full JSON status and store it in a variable.

litellm_operation_url="${BASE_URL}/${operation_name}"
echo "Polling litellm operation status url: ${litellm_operation_url}"
status_response=$(curl -s -H "x-goog-api-key: $GEMINI_API_KEY" "${litellm_operation_url}")

Check the "done" field from the JSON stored in the variable.

is_done=$(echo "${status_response}" | jq .done)
echo "Operation status: ${is_done}"
if [ "${is_done}" = "true" ]; then
# Extract the download URI from the final response.
video_uri=$(echo "${status_response}" | jq -r '.response.generateVideoResponse.generatedSamples[0].video.uri')

echo "Google asked to download from: ${video_uri}"
litellm_video_uri=$(printf '%s' "${video_uri}" | sed "s|https://generativelanguage.googleapis.com/v1beta|${BASE_URL}|")
echo "Litellm passthrough download url: ${litellm_video_uri}"
# Download the video using the URI and API key and follow redirects.
curl -L -o dialogue_example.mp4 -H "x-goog-api-key: $GEMINI_API_KEY" "${litellm_video_uri}"
break

fi

Wait for 5 seconds before checking again.

sleep 10
done`

[ishaan-jaff]

this is to google AI studio