How a page runs

menu
  └─ /page/run?param={page id}
        ├─ read the JSON from sys.page_def
        ├─ collect sql_id values into this session’s allowlist
        └─ plus/ loads a component for each Body[].Type and renders it

when a component needs data
  └─ POST /sql/run  { sql_id, ...params }
        ├─ sql_id not on the allowlist → rejected
        └─ otherwise → pre_sql, main_sql, post_sql in one transaction

Each layer owns one job:

Layer	What it holds	When you change it
sys.page_def	Layout JSON	Page editor /page_editor
sys.page_sql	Query and save SQL	SQL editor /sql_editor
plus/	Turns JSON into grids, forms, and the rest	Change the engine script and bump the asset version
/sql/run	Runs SQL that is on the allowlist	The SQL engine on the server

Page JSON is JSON5-like: trailing commas are allowed, and the browser parses it with eval. Any string value may be "js:" plus an expression, evaluated at runtime. See Page JSON.

/sql/run does not accept arbitrary SQL. The user has to open the page first. Only then does the server put that page’s declared sql_id values into the session. A call made without opening the page is rejected. A popup child page must also be listed in the parent’s SubPages. See Permissions and the SQL allowlist.