Add CVDIAG logging + x-diag-hops breadcrumb (route-<fw>/backend-<fw>) at each forwarding hop across LangGraph (py/ts/fastapi), google-adk, the self-contained Node + Python shims, spring-ai (Java) and ms-agent (.NET). Breadcrumb append is gated on diagnostic-header presence so non-diagnostic traffic stays byte-identical; surfaces previously-silent forwarding misses (empty configurable, missing httpx event-hooks target, swallowed hook-install errors).
Matches the CopilotKit runtime's extractForwardableHeaders() which already forwards all x-* prefixed headers. Enables any custom x-* header to propagate from browser through AG-UI to LLM calls.
Integration-level AsyncLocal + ASP.NET middleware + PipelinePolicy. Forwards x-aimock-* headers from incoming AG-UI requests to outgoing OpenAI calls. Stopgap until copilotkit-sdk-dotnet ships.