RemoteGraph, and what every other framework does instead
LangGraph ships a class that turns an agent running on another machine into a node in your graph. You construct a RemoteGraph, pass it to builder.add_node(...), and the call site reads exactly like a local subgraph. It subclasses PregelProtocol, so as far as your parent graph is concerned there is no network there at all.
I wanted to know what that costs, and what the other frameworks offer in its place. Two of them can be measured: the same parent-and-child pair runs against a real LangGraph server and against a LlamaIndex workflow server, with the same five contract mismatches pushed through each boundary. CrewAI, the OpenAI Agents SDK and A2A are read from their docs and specs, because two of the three turn out to have no remote-agent primitive to measure.
The headline result is an inversion. RemoteGraph looks typed and validates nothing at the boundary: I renamed one field in the child, redeployed it, left the parent untouched, and the parent returned its own input with no error and no warning — a result indistinguishable from the child never running. LlamaIndex has no RemoteGraph at all; its server-and-client pair looks like a raw HTTP call, publishes a JSON Schema, and rejects a malformed request with a 400 and per-field errors. The same rename throws a KeyError on the line I wrote.