Python: Bug: `TypeError: cannot pickle '_thread.RLock' object` when cloning Kernel with OpenTelemetry enabled

[MMoshtaghi]

Describe the bug
When using features that internally clone a semantic_kernel.Kernel instance (such as agent orchestrations like HandoffOrchestration), a TypeError is raised if OpenTelemetry metrics are enabled. The error, TypeError: cannot pickle '_thread.RLock' object, originates from a deepcopy operation on the kernel's plugins.

The root cause appears to be the invocation_duration_histogram and streaming_duration_histogram fields on the KernelFunction model. These fields are OpenTelemetry Histogram objects which contain thread locks and are therefore not serializable or deep-copyable.

While there have been previous attempts to fix a similar error, such as in PR #9292, by marking the fields with exclude=True and providing a default_factory, this does not prevent copy.deepcopy() from attempting to copy them, leading to the crash.

To Reproduce
Add observability ( you can use the sample in MS Learn ) to an agent orchestration that clones the kernel for its members, for example HandoffOrchestration

Expected behavior
The kernel should be cloned successfully without raising a TypeError, allowing orchestrations and other features to work correctly with observability enabled.

Screenshots
Not applicable

Stack Trace

Traceback (most recent call last):
  File "...", in <module>
    asyncio.run(main())
  File "...", in main
    await handoff.invoke("test")
  File "/.../semantic_kernel/agents/orchestration/orchestrator_base.py", line 125, in invoke
    ...
  File "/.../semantic_kernel/agents/orchestration/handoffs.py", line 174, in __init__
    self._kernel = agent.kernel.clone()
  File "/.../semantic_kernel/kernel.py", line 541, in clone
    plugins=deepcopy(self.plugins),
  File "/.../copy.py", line 136, in deepcopy
    y = copier(x, memo)
  ...
  File "/.../copy.py", line 151, in deepcopy
    rv = reductor(4)
TypeError: cannot pickle '_thread.RLock' object

Platform

• Python version: 3.12
• Semantic-Kernel version: >=1.32.2
• OS: Mac

[TaoChenOSU]

Hi @MMoshtaghi,

I am curious if you ran into the same issue running this sample: https://github.com/microsoft/semantic-kernel/blob/main/python/samples/getting_started_with_agents/multi_agent_orchestration/step4_handoff.py?