Eval fails for non-English languages

[lifnaja]

Describe the bug
When evaluating text in other languages (e.g., Thai, etc.), the eval logic incorrectly returns mismatches (Match score: 0)— even when the evaluated expression should be valid or identical in meaning.

To Reproduce

root_agent = Agent(
    name="sample_agent",
    model="gemini-2.5-flash",
    description="Greeting agent",
    instruction="""
    You are an assistant that will reply to the user with only the word 'สวัสดี'
    """,
)

Expected behavior
Eval should correctly handle input in other languages.

Screenshots

Desktop (please complete the following information):

• OS: macOS
• Python : 3.12.8
• ADK version: 1.15.1

Model Information:

• Are you using LiteLLM: No
• Which model is being used : gemini-2.5-flash

Additional context
Add any other context about the problem here.