Fix langfuse import paths for version 3.3.0+

[Copilot]

Langfuse 3.3.0+ restructured its module exports, removing langfuse.callback in favor of langfuse.langchain. The old import paths caused startup crashes with ModuleNotFoundError: No module named 'langfuse.callback'.

Changes

Updated imports across 5 files:

# Before
from langfuse.callback import CallbackHandler as LangfuseCallbackHandler
from langfuse.callback.langchain import LangchainCallbackHandler

# After
from langfuse.langchain import CallbackHandler as LangfuseCallbackHandler
from langfuse.langchain.CallbackHandler import LangchainCallbackHandler

Modified files:

• services/observability/observabilty_service.py
• services/langchain/factories/langchain_factory.py
• services/langchain/factories/callback_handlers/langfuse_callback_handler_factory.py
• services/langchain/factories/callback_handlers/callback_handlers_factory.py
• services/langchain/rag_chain.py

Note: CallbackHandler and LangchainCallbackHandler reference the same class; the latter is used where type annotations explicitly require the concrete class name.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[GenAI orchestrator] Container gen-ai-orchestrator-server Crash at startup with error No module named 'langfuse.callback'</issue_title>
<issue_description>On kubernetes, the version 25.10.3 of gen-ai-orchestrator-server container (docker.io/tock/gen-ai-orchestrator-server:25.10.3) crash with the following error No module named 'langfuse.callback' at startup.

logs tockocloud-genai-orchestrator-74c49d659b-s5m85 | more                                                                                                                      15:46:42 
Traceback (most recent call last):
  File "/usr/local/bin/uvicorn", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 1161, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 1082, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 1443, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 788, in invoke
    return __callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/uvicorn/main.py", line 412, in main
    run(
  File "/usr/local/lib/python3.11/site-packages/uvicorn/main.py", line 579, in run
    server.run()
  File "/usr/local/lib/python3.11/site-packages/uvicorn/server.py", line 66, in run
    return asyncio.run(self.serve(sockets=sockets))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/asyncio/runners.py", line 190, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/asyncio/base_events.py", line 654, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/uvicorn/server.py", line 70, in serve
    await self._serve(sockets)
  File "/usr/local/lib/python3.11/site-packages/uvicorn/server.py", line 77, in _serve
    config.load()
  File "/usr/local/lib/python3.11/site-packages/uvicorn/config.py", line 435, in load
    self.loaded_app = import_from_string(self.app)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/uvicorn/importer.py", line 22, in import_from_string
    raise exc from None
  File "/usr/local/lib/python3.11/site-packages/uvicorn/importer.py", line 19, in import_from_string
    module = importlib.import_module(module_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen importlib._bootstrap>", line 1204, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1176, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1147, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 690, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 940, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/gen_ai_orchestrator/main.py", line 32, in <module>
    from gen_ai_orchestrator.routers.completion_router import completion_router
  File "/gen_ai_orchestrator/routers/completion_router.py", line 39, in <module>
    from gen_ai_orchestrator.services.completion.completion_service import (
  File "/gen_ai_orchestrator/services/completion/completion_service.py", line 37, in <module>
    from gen_ai_orchestrator.services.langchain.factories.langchain_factory import (
  File "/gen_ai_orchestrator/services/langchain/factories/langchain_factory.py", line 29, in <module>
    from langfuse.callback import CallbackHandler as LangfuseCallbackHandler
ModuleNotFoundError: No module named 'langfuse.callback'

I had an issue in the validation process of tock helm chart 0.60 (for 25.10.3). In the test deployment, the gen-ai-orchestrator-server parameters are the same as those used for 25.3.10 version.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [GenAI orchestrator] Container gen-ai-orchestrator-server Crash at startup with error No module named 'langfuse.callback' #1973

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[assouktim]

@vsct-jburet This is deeply rooted in #1954
Because it's not just a problem with importing, but also with using the callback itself, and Langfuse V3 API

[vsct-jburet]

@vsct-jburet This is deeply rooted in #1954 Because it's not just a problem with importing, but also with using the callback itself, and Langfuse V3 API

@assouktim It seems that this PR fixes the issue - at least for the pod startup :). What do you think ? Is it a good idea to merge it right now, or do we need to wait #1954 ?

[assouktim]

ok i agree