instrumentation-threading breaks when `Thread.run()` is called without `Thread.start()`

[dinmukhamedm]

Describe your environment

OS: MacOS 15
Python version: 3.13.9
Package version: 0.60b1 / main

What happened?

With ThreadingInstrumentor() enabled, if a thread is created and immediately run, the program will throw an exception.

Steps to Reproduce

from threading import Thread
from opentelemetry.instrumentation.threading import ThreadingInstrumentor

def main():
    ThreadingInstrumentor().instrument()
    t = Thread(target=lambda: print("Hello world!"))
    t.run()

if __name__ == "__main__":
    main()

Expected Result

Program prints out "Hello world!" and exits

Actual Result

Traceback (most recent call last):
  File "/Users/din/threading-repro/main.py", line 10, in <module>
    main()
    ~~~~^^
  File "/Users/din/threading-repro/main.py", line 7, in main
    t.run()
    ~~~~~^^
  File "/Users/din/threading-repro/.venv/lib/python3.13/site-packages/opentelemetry/instrumentation/threading/__init__.py", line 150, in __wrap_threading_run
    token = context.attach(instance._otel_context)
                           ^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Thread' object has no attribute '_otel_context'

Additional context

I know this isn't a completely valid way of using python threading.Threads, and that run() is a base method meant to behave somewhat like protected methods, i.e. can be overriden, but shouldn't be called directly. For example, attempting to join a thread like this will result in RuntimeError: cannot join thread before it is started.

However:

• The repro is still a completely valid Python program and doesn't fail
• The current instrumentation somehow breaks with frameworks like celery, maybe they run threads directly without starting them, and their framework works.

Would you like to implement a fix?

Yes

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