Single source of truth
Protocol
Contracts define the request shape, token model, state machine, and transport abstraction. Every Hotline inherits the same outer rules from that source.
Local runtime group
Client
Caller Controller and Responder Controller live in the user's own runtime. A team can run one side or both sides on the same machine for local proof loops.
Hosted control plane
Platform
Catalog, token, delivery metadata, and metrics belong to the control plane. Platform is the hosted public form of that surface.
Private control plane
Selfhost
Selfhost is the same control-plane shape deployed on your own infrastructure. The protocol stays the same; the operating boundary changes.
OPERATING SURFACE
Control plane
HTTPS requests to Platform or Selfhost handle catalog lookup, token issuance, delivery metadata, and metrics. This is where operating policy lives.
OPERATING SURFACE
Data plane
TaskContract and ResultPackage move between Caller and Responder through TransportAdapter. The important boundary is that Platform does not relay the business payload hop-by-hop.
PAGE FAQ
3 questions engineers usually ask first
These are the boundary questions that matter before you decide whether to integrate, self-host, or compare the model against adjacent tool protocols.
What does the protocol architecture page explain?
It isolates the roles of Protocol, Client, Platform, and Selfhost, and explains why CALL ANYTHING separates control-plane operating policy from the data-plane capability exchange.
Why move this off the homepage?
Because the homepage should anchor product meaning first. The architecture page is for engineering-intent reading and answer-engine retrieval when the question is about system boundaries, not brand narrative.
What is the relationship between Platform and Selfhost?
They are the same control-plane shape in different deployment forms. Platform is hosted and public-facing; Selfhost is private infrastructure running the same operating surface under your own boundary.
NEXT
Where to continue
Once the control-plane split is clear, move to one stable evidence page or one runnable proof path.
Protocol Examples
See the minimal request, result_package, error, and registration payload shapes.
Request · result_package · error
Glossary
Lock down the canonical meanings of Hotline, Caller, Responder, and Template Bundle.
Definitions · canonical terms
Caller Quick Start
Map the architecture back to one real local loop with commands and one result_package.
Quick Start · local loop
Hotline vs MCP
Use the compare page when the real question is whether this is just another tool invocation surface.
Compare · positioning