Attach hf_config metadata to AutoBridge

[yaoyu-33]

Summary

• ensure AutoBridge passes hf_config into bridge dispatch
• allow model bridges to persist hf_config when instantiated via dispatcher

Testing

• not run (not requested)

Summary by CodeRabbit

• Bug Fixes
  • Improved model bridge configuration handling to better preserve and apply configuration settings during model conversion.

[copy-pr-bot]

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[yaoyu-33]

/ok to test 49ff815

[coderabbitai]

📝 Walkthrough

Walkthrough

The changes extend the bridge factory to accept and propagate an optional hf_config parameter. The auto_bridge module now resolves hf_config from the pretrained model and passes it through to the bridge factory, enabling more complete configuration initialization during bridge instantiation.

Changes

Cohort / File(s)	Summary
Auto Bridge Configuration Resolution src/megatron/bridge/models/conversion/auto_bridge.py, src/megatron/bridge/models/conversion/model_bridge.py	Extended bridge factory to accept optional hf_config parameter. Auto_bridge now resolves hf_config from self.hf_pretrained (prioritizing hf_config attribute, then config attribute for PreTrainedCausalLM, then the object itself) and passes it through get_model_bridge, which assigns it to the bridge instance before returning.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Attach hf_config metadata to AutoBridge' clearly and concisely describes the main change: adding hf_config metadata handling to the AutoBridge mechanism.
Test Results For Major Changes	✅ Passed	Minor internal changes (~12 net lines) for metadata passing through bridge dispatch mechanism with full backward compatibility and no algorithmic impact.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feature/autobridge-hf-config

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[yaoyu-33]

/ok to test f42142a