bug: orchestrator_stubs missing GemmaClassificationAgent fallback → ImportError when classification agent unavailable #11390

Root cause (corrects the #11248 concurrent_limiter triage)

orchestration/orchestrator_stubs.py provides except ImportError fallback classes for AgentManager (line 28) and WorkflowStep (line 46), but the GemmaClassificationAgent try/except (lines 14-19) only sets CLASSIFICATION_AVAILABLE = False — no fallback class. Yet GemmaClassificationAgent is re-exported in __all__ and imported by orchestrator.py:80 (from orchestration.orchestrator_stubs import ..., GemmaClassificationAgent, ...).

So in any environment where agents.gemma_classification_agent can't import, from orchestration.orchestrator_stubs import GemmaClassificationAgent raises ImportError: cannot import name 'GemmaClassificationAgent', breaking the whole orchestrator import chain.

This is the actual first blocker of tests/services/test_concurrent_limiter.py collection (which imports services.workflow_automation → manager → orchestrator) — NOT the "py3.14 asyncio.Event artifact" the earlier #11248 triage assumed (collection never reached the test logic).

Fix

Add the missing except ImportError fallback class for GemmaClassificationAgent, matching the AgentManager/WorkflowStep pattern. It is only instantiated behind a CLASSIFICATION_AVAILABLE guard (orchestrator.py:178), so a minimal placeholder is sufficient — it just needs to exist as an importable name.

Note

test_concurrent_limiter collection is still blocked further down the chain by knowledge/base.py's unguarded from llama_index.core import ... (llama_index is in no requirements file) — tracked separately.