[Leela Mahalakshmi (Leela0o5)]

Motivation & Context

OllamaChatClient checked that any data content in a user message was an image, then sent all data contents in Ollama's images field. A user message with an image plus a non-image attachment (e.g. a PDF) passed the check, and the PDF bytes were sent to Ollama as an image. Ollama's chat API has no document input, so this can never work and fails later with a confusing error.

Description & Review Guide

• What are the major changes? The check in _format_user_message now requires every data content to be an image (any to all). Added a unit test with an image plus a PDF.
• What is the impact of these changes? Mixed image/non-image messages now fail early with ChatClientInvalidRequestException, matching how a message with only non-image data is already handled. Image-only messages are unchanged.
• What do you want reviewers to focus on? Whether rejecting (rather than dropping the non-image items with a warning) is the preferred behavior.

Related Issue

Fixes #8916

Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
• This PR is linked to an issue and there is no other open PR for this issue (see Related Issue above).
• This is not a breaking change.

[Copilot]

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[Leela Mahalakshmi (Leela0o5)]

@microsoft-github-policy-service agree

[Copilot]

Copilot review overview

🟢 Approval recommended

The validation change directly resolves the reported bug and includes focused regression coverage.

Review effort: Balanced
Findings: None