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Describe the bug

Description:

GraphRAG fails in Celery worker processes with RuntimeError: threads can only be started once when executing queries that use embedding models.

Root Cause

The run_coroutine_sync() function in graphrag/language_model/providers/fnllm/utils.py is not fork-safe. When Celery creates worker processes by forking:

1. Process Fork: Celery forks the main process to create workers
2. Thread Inheritance: Child processes inherit parent's global thread objects (_thr, _loop, _pid)
3. Dead Threads: Inherited thread objects exist but the actual threads are not running
4. Restart Failure: Code attempts to call _thr.start() on a dead thread object
5. Runtime Error: Python raises "threads can only be started once" because threads have single-use lifecycle

Additional Files to Reference:

• graphrag/language_model/providers/fnllm/utils.py (lines 112-134)
• graphrag/language_model/providers/fnllm/models.py (where run_coroutine_sync is called)

Impact:

• GraphRAG queries fail in Celery workers
• Any async operation using FNLLM models crashes
• Production deployments using Celery are broken

Steps to reproduce

Expected Behavior

No response

GraphRAG Config Used

No Changes in Config

Logs and screenshots

No response

Additional Information

• GraphRAG Version: 2.3.0
• Operating System: Windows
• Python Version: 3.11
• Related Issues: