Missing APIs and compatibility

What follows is about the embedding contract — what’s available to your application from the outside: session commands and the browser surface. Inside the desktop SumDoc application itself, its shell can do more, but that’s its internal exchange, and you can’t rely on it for integration.

What’s missing	What to use instead
Click and double-click	Not in the public surface contract. Inside the product, text, tables, borders, and autofit width are handled — what of this will make it into the contract
Right-click and custom menu items	Not in the contract. Inside the product, the text and table menus work over their own internal channel, but a way to plug in your own hasn’t been settled yet — Readiness and boundaries
A public “what’s under this point” call	Not in the session or the surface; available as a separate processor command: hit-test-docx
Editing an arbitrary node	There’s no single universal command
Stable version numbering	No: the contract is marked 1.0.0-draft
WebSocket from outside, without a token	Not allowed: only a local interface, with a token
Binary WebSocket frames	Requests travel only as UTF-8 text frames. A binary frame gets the refusal “session WebSocket requests must be UTF-8 text frames”, and the connection stays open
Your own copy of the document in the editor window	Not allowed: the model, history, and file writing belong to the core

While the contract is marked 1.0.0-draft, pin the checksum and version of the executable together with the type declarations, and on startup check the schema of the greeting message and the supported_commands list — both arrive in the very first line of the session.