q:application

A web app in Quantum is not a q:application: it is a folder of pages in components/, served by quantum start. See Getting Started and the Quick Start.

q:application is the root element for programs that are not web pages. None of them is part of the supported core (see SUPPORT_TIERS.md):

type	Tier	What quantum run app.q does
game	Laboratory	builds a 2D game (a Godot 4 project): see Games
hive	Laboratory	writes the rules and the whitelist of Quantum OS's Hive: see The Hive's rules
screen	Laboratory	writes the scene the Hive of Quantum OS shows on the machine's screen: see The Hive's screen
terminal	Experimental	builds a terminal UI
ui	Experimental	builds a UI, layout only (--target html or textual; mobile is Laboratory)

Running an experimental or Laboratory application prints a one-time warning saying so. Their tags and output can change in any release.

Removed: type="html", type="api", type="microservices"

Earlier versions documented web servers and JSON APIs declared as q:application with q:route blocks. They never ran their routes — html failed on start, and api answered with the literal text of the first q:return — and were removed in 0.11. q:application without a type meant type="html", so it is refused too. type="testing" (the qtest: engine) was removed in 0.22; its replacement is quantum test.

The parser now stops with directions:

<q:application> type="html" was removed in Quantum 0.11: it never ran its
routes. Build a web app as pages in components/ (components/index.q is /) and
run `quantum start`. See https://quantumframework.net/guide/getting-started

What each route becomes:

Before	Now
<q:route path="/about" method="GET">	components/about.q
<q:route path="/" method="GET">	components/index.q
<q:route path="/users" method="POST">	a q:action in components/users.q
JSON API route	not available