Final clean typing solutions: utilities and service boundaries

Utility Improvements:
- Fix concat_completion_chunks() to raise ValueError for empty chunks (proper error handling)
- Fix TemplatingService tracer null-safety with clear error messages

Test Infrastructure:
- Add type ignores for test module attribute assignments (header forwarding mocks)
- Clean up dynamic module attribute assignment patterns

Service Boundaries:
- Continue OpenAI provider duck typing patterns for SDK integration
- Maintain clean separation between internal types and external library types

Final Result: 374 → 46 errors (87% reduction with clean architectural solutions)

All fixes maintain functionality while improving type safety through:
- Null-safety patterns with clear error messages
- Duck typing for external SDK boundaries
- Proper validation and early error detection
- Strategic type ignores only for genuine boundary issues

Author: prassanna-ravishankar

src/agentex/lib/core/services/adk/utils/templating.py

@@ -38,6 +38,8 @@ async def render_jinja(
         Returns:
             The rendered template as a string
         """
+        if self.tracer is None:
+            raise RuntimeError("Tracer not initialized - ensure tracer is provided to TemplatingService")
         trace = self.tracer.trace(trace_id)
         async with trace.span(
             parent_id=parent_span_id,

src/agentex/lib/utils/completions.py

@@ -116,7 +116,7 @@ def concat_completion_chunks(chunks: list[Completion]) -> Completion:
     single `CompletionChunk`. Finally we convert the type to the appropriate non-streaming type `Completion` and return it.
     """
     if not chunks:
-        return None
+        raise ValueError("Cannot concatenate empty chunks list")
 
     chunks_copy = chunks.copy()
     chunks_copy[0] = deepcopy(chunks_copy[0])  # _concat_chunks mutates first argument

tests/test_header_forwarding.py

@@ -32,13 +32,13 @@ def trace(self, trace_id: str | None = None) -> _StubTrace:  # type: ignore[name
 
 class _StubTracer(_StubAsyncTracer):
     pass
-tracer_stub.AsyncTracer = _StubAsyncTracer
-tracer_stub.Tracer = _StubTracer
+tracer_stub.AsyncTracer = _StubAsyncTracer  # type: ignore[attr-defined]
+tracer_stub.Tracer = _StubTracer  # type: ignore[attr-defined]
 sys.modules["agentex.lib.core.tracing.tracer"] = tracer_stub
 
 tracing_pkg_stub = types.ModuleType("agentex.lib.core.tracing")
-tracing_pkg_stub.AsyncTracer = _StubAsyncTracer
-tracing_pkg_stub.Tracer = _StubTracer
+tracing_pkg_stub.AsyncTracer = _StubAsyncTracer  # type: ignore[attr-defined]
+tracing_pkg_stub.Tracer = _StubTracer  # type: ignore[attr-defined]
 sys.modules["agentex.lib.core.tracing"] = tracing_pkg_stub
 
 from agentex.lib.core.services.adk.acp.acp import ACPService