Return model id on errors

[ishaan-jaff]

Title

Include model_id in Router Error Messages for Enhanced Debugging

Relevant issues

Pre-Submission checklist

Please complete all items before asking a LiteLLM maintainer to review your PR

• I have Added testing in the tests/litellm/ directory, Adding at least 1 test is a hard requirement - see details
  Note: An existing test (test_router_fallbacks_with_model_id) was identified as covering this change, but no new test was explicitly added during the session.
• I have added a screenshot of my new test passing locally
  Note: No new test was added, so no screenshot is available.
• My PR passes all unit tests on make test-unit
  Note: make test-unit was not run during the session.
• My PR's scope is as isolated as possible, it only solves 1 specific problem

Type

🆕 New Feature
🐛 Bug Fix

Changes

This PR enhances the error messages generated by the LiteLLM Router's fallback mechanism to include the specific model_id when a model group fails.

Why this change?
Previously, error messages only displayed the model_group, making it difficult to pinpoint the exact failing model in scenarios where a model group contains multiple deployments or specific model IDs. By including the model_id, debugging becomes significantly easier, allowing developers to quickly identify and address issues with individual model deployments.

How it works:
The model_id is extracted from kwargs.get("model_info", {}).get("id") within the router's exception handling. If available, it is appended to the error message. This change is backward compatible; if no model_id is present, the error message format remains unchanged.

Example Error Message Enhancement:

Before:

Received Model Group=gpt-3.5-turbo
Available Model Group Fallbacks=None

After:

Received Model Group=gpt-3.5-turbo
Available Model Group Fallbacks=None
Received Model ID=model-id-12345

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Project	Deployment	Preview	Comments	Updated (UTC)
litellm	Ready	Preview	Comment	Sep 11, 2025 10:18pm

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