fix(langchain): Extract model name from 'model' field for non-OpenAI providers

[NikitaVoitov]

Summary

Fixes model name extraction to support providers that use model instead of model_name in invocation params. This enables proper model identification for Snowflake Cortex, Anthropic, Google, and other non-OpenAI providers.

Fixes #124

The Bug (Before)

Span name: chat unknown_model
gen_ai.request.model: unknown_model

The Fix (After)

Span name: chat claude-3-5-sonnet
gen_ai.request.model: claude-3-5-sonnet

Changes

callback_handler.py

Updated model name extraction with fallback chain:

# Before - only checks OpenAI convention
model = invocation_params.get("model_name", "unknown_model")

# After - fallback chain supporting multiple providers
model = (
    invocation_params.get("model_name") or  # OpenAI
    invocation_params.get("model") or        # Snowflake, Anthropic, Google
    "unknown_model"
)

Testing

• test_model_name_extraction_from_model_field - verifies model field extraction
• test_model_name_extraction_priority - verifies model_name takes precedence over model
• test_model_name_fallback_to_unknown - verifies fallback when neither field present
• All existing tests pass

Files Changed

File	Changes
instrumentation-genai/opentelemetry-instrumentation-langchain/src/opentelemetry/instrumentation/langchain/callback_handler.py	Updated model extraction with fallback chain
instrumentation-genai/opentelemetry-instrumentation-langchain/tests/test_callback_handler_agent.py	Added 3 tests for model name extraction

[github-actions]

Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

---

I have read the CLA Document and I hereby sign the CLA

---

_{You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.}

[NikitaVoitov]

I have read the CLA Document and I hereby sign the CLA