Adds a module-level docstring at the top of header_propagation.py that explains in plain
English what the module does (forwards CopilotKit request-context x-* headers onto
outbound LLM/provider HTTP calls so downstream services like the aimock test server and
proxies can correlate the outbound call with the original inbound request), the precise
scope (only headers the application itself set via set_forwarded_headers; no request
bodies, cookies, user data, credentials, or telemetry), and the mechanics (walks the
._client chain to find the httpx client and attaches an async hook for AsyncClient or a
sync hook for Client). Also softens a few comments and docstrings whose wording could
read as surveillance language ("inject" / "installing an async hook ... silently dropped")
to neutral engineering phrasing ("attach" / "the forwarded headers would not be attached
to the outbound request") without losing any technical meaning or warnings. No executable
logic, signatures, conditionals, or string literals in code paths were changed; the diff
is comments and docstrings only.
In response to review feedback on PR #5088.
Forwarded headers (e.g. X-AIMock-Context) were dropped before reaching the
wire in two cases. First, install_httpx_hook only attached to the immediate
client, missing an httpx client nested one or more ._client hops deep; it now
walks the ._client chain (bounded) to find the object that carries
event_hooks. Second, a sync def hook installed on an httpx.AsyncClient was
invoked as a coroutine and never awaited, silently dropping headers; the hook
is now async def for AsyncClient and sync def for Client. Async detection
prefers isinstance against the real httpx classes and falls back to an EXACT
"AsyncClient" MRO class-name match (not startswith("Async"), which would
misclassify a sync client whose MRO includes an Async*-named base).
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.
ContextVar-based ambient state + httpx event hook. Incoming
x-aimock-* headers from AG-UI requests are forwarded to outgoing
LLM API calls. Keys normalized to lowercase. Warning emitted when
install_httpx_hook receives an unrecognized client type.
Jordan Ritter