fix(LiteLlm): add fallback user message to prevent empty content error with include_contents='none'

[ishanrajsingh]

This fix addresses an issue in the LiteLlm integration where setting include_contents='none' causes the content payload sent to the LLM provider to be empty, resulting in a BadRequestError. The patch adds a minimal fallback user message in the generate_content_async method when no messages are included, ensuring a non-empty content array is always sent. This prevents errors from providers that require non-empty input and improves compatibility when using LiteLlm with the Agent Development Kit.

GitHub Issue:
This PR addresses the bug reported in issue #3242 titled "LiteLlm + include_contents='none' results in empty content sent to the provider -> Error". The issue is already created and linked here: #3242

Testing Plan:

I verified the fix by running a scenario where an LlmAgent uses LiteLlm with include_contents='none'.

The test confirms that the LLM request no longer sends empty content, preventing the BadRequestError from the LLM provider.

Additionally, I ran existing LiteLlm unit tests to ensure no regressions occur.

For thoroughness, a new test can be added simulating include_contents='none' to confirm fallback content insertion.

[gemini-code-assist]

Summary of Changes

Hello @ishanrajsingh, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a BadRequestError within the LiteLlm integration by preventing empty content payloads from being sent to Large Language Model providers. The fix ensures that even when include_contents='none' is specified, a default user message is included, thereby maintaining compatibility with LLM APIs that require non-empty input and improving the overall robustness of the Agent Development Kit's LiteLlm component.

Highlights

• Fixes Empty Content Error: Addresses a BadRequestError in LiteLlm that occurred when include_contents='none' resulted in an empty content payload being sent to LLM providers.
• Introduces Fallback User Message: A minimal fallback user message is now added in the generate_content_async method if no messages are included, ensuring the content array is never empty.
• Improves Compatibility: This change prevents errors from providers that require non-empty input and enhances compatibility when using LiteLlm with the Agent Development Kit.

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[adk-bot]

Response from ADK Triaging Agent

Hello @ishanrajsingh, thank you for creating this PR!

To help reviewers to review your PR more efficiently, could you please provide the followings:

• a Github issue associated with this PR. If there is no existing issue, could you please create one?
• a testing plan for your changes.
• logs or screenshot after the fix is applied.

Thanks!

[gemini-code-assist]

Code Review

This pull request addresses an issue where the LiteLlm integration would error when include_contents='none' due to an empty content payload. The fix adds a fallback user message to ensure a non-empty content array is always sent to the LLM provider. I have identified a potential issue with the placement of the fallback logic that could lead to unexpected behavior.

[ishanrajsingh]

handle empty file content

[ishanrajsingh]

GitHub Issue:
This PR addresses the bug reported in issue #3242 titled "LiteLlm + include_contents='none' results in empty content sent to the provider -> Error". The issue is already created and linked here: #3242

Testing Plan:

I verified the fix by running a scenario where an LlmAgent uses LiteLlm with include_contents='none'.

The test confirms that the LLM request no longer sends empty content, preventing the BadRequestError from the LLM provider.

Additionally, I ran existing LiteLlm unit tests to ensure no regressions occur.

For thoroughness, a new test can be added simulating include_contents='none' to confirm fallback content insertion.

[ishanrajsingh]

/gemini review

[gemini-code-assist]

Code Review

This pull request addresses a critical issue where the LiteLlm integration fails when include_contents='none' due to an empty content payload. The fix introduces a fallback user message to ensure a non-empty content array is always sent to the LLM provider. I have added a review comment to suggest a minor improvement to the fallback message.

[ishanrajsingh]

/gemini review

[gemini-code-assist]

Code Review

This pull request addresses a critical issue where LiteLlm integration with include_contents='none' results in an empty content payload, causing a BadRequestError. The fix introduces a fallback user message when no messages are included, ensuring a non-empty content array is always sent. This review focuses on the correctness and maintainability of the implemented solution, ensuring it effectively prevents the error and adheres to best practices.