Extract incoming x-* headers from LangGraph's runtime config and republish
them via the forwarded-headers ContextVar so the httpx hook can attach
them to outbound provider requests. Apply documented precedence
(context > configurable, wrapper-dict > raw x-*) by processing sources
in order with first-write-wins and lowercasing keys at insertion so
mixed-case headers do not silently overwrite each other downstream.
Always clear the ContextVar on early exits so stale headers from a prior
request never leak into the next: explicit set_forwarded_headers({}) on
the RuntimeError no-active-runnable path and on the generic exception
fallback. The happy path already overwrites the ContextVar
unconditionally, even with an empty dict.
The change also installs the httpx event hook once per chat-model client
via a module-level set keyed by id(client), so models reused across
requests pick up fresh per-request headers without re-hooking.
Jordan Ritter