every plugin route renders a workspace, and it is not a rule you can forget

an exclusionary rule, made structural. a plugin does not render a screen: it
contributes panels and says how they are arranged, and the shell renders
WorkspaceView around them.

    web/panels.ts   appRegistryMetas — at least one panel
    web/layout.ts   defaultLayout — how they are arranged

both required the moment web/ exists, and missing either is refused at discovery
by name and with the reason. tested:

    probeplug: has a web/ directory but is missing web/layout.ts.
    Every plugin route renders a Workspace: contribute panels and a layout,
    not a screen.

there is deliberately no way to export a component. one that could would be free
to render a bare div, a full-page form, or its own navigation, and the platform
would become a shell hosting strangers' layouts rather than one application.
non-compliance is not so much refused as unrepresentable — there is nowhere to
put a screen.

the shell registers <prefix> and <prefix>/:section, exactly as the core screens
do, so a plugin's sections stay addressable and cmd-clickable, and panels read
useParams independently rather than passing state between themselves.
appTypes.allowed is pinned to that plugin's own keys, so a persisted layout
naming something else falls back instead of rendering another plugin's panel
inside this screen.

the example plugin is rebuilt to model it — two panels, a layout, one of them
calling its own /api/example/ping through useClient — because the reference
implementation is what everyone copies.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/servers/plugins/discover.ts

@@ -19,8 +19,8 @@ import { manifestProblems, type DiscoveredPlugin, type PluginManifest } from './
 //   api/router.ts      a backend router
 //   db/schema.ts       tables
 //   sidecar/index.ts   a process (`.mjs` instead means node — see below)
-//   web/Router.tsx     a frontend
-//   web/panels.ts      panel apps
+//   web/panels.ts      panel apps — REQUIRED with web/
+//   web/layout.ts      how they are arranged — REQUIRED with web/
 //
 // Nothing here reads the database. This answers "what is on disk", which is a different question from
 // "what is installed" — the install table answers that, and the two disagreeing is a state the app store
@@ -45,11 +45,29 @@ function findSidecar(dir: string): DiscoveredPlugin['sidecar'] {
   return null;
 }
 
-function findWeb(dir: string): DiscoveredPlugin['web'] {
-  const router = join(dir, 'web', 'Router.tsx');
-  if (!existsSync(router)) return null;
-  const panels = join(dir, 'web', 'panels.ts');
-  return { router, panels: existsSync(panels) ? panels : null };
+/**
+ * A plugin's frontend, or a reason it is refused.
+ *
+ * `web/` present means BOTH `panels.ts` and `layout.ts` must be. That is how "every route renders a
+ * workspace with at least one panel" is enforced: there is no way to ship a frontend that is not a
+ * workspace, because the plugin never renders the screen — it hands over panels and an arrangement.
+ */
+function findWeb(dir: string, appName: string): { web: DiscoveredPlugin['web']; error?: string } {
+  const webDir = join(dir, 'web');
+  if (!existsSync(webDir)) return { web: null };
+
+  const panels = join(webDir, 'panels.ts');
+  const layout = join(webDir, 'layout.ts');
+  const missing = [!existsSync(panels) && 'web/panels.ts', !existsSync(layout) && 'web/layout.ts'].filter(Boolean);
+  if (missing.length) {
+    return {
+      web: null,
+      error:
+        `${appName}: has a web/ directory but is missing ${missing.join(' and ')}. ` +
+        `Every plugin route renders a Workspace: contribute panels and a layout, not a screen.`,
+    };
+  }
+  return { web: { panels, layout } };
 }
 
 const fileOrNull = (path: string): string | null => (existsSync(path) ? path : null);
@@ -75,6 +93,9 @@ export async function loadPlugin(dir: string, appName: string): Promise<Discover
   const problems = manifestProblems(appName, manifest);
   if (problems.length) throw new Error(`${appName}: ${problems.join('; ')}`);
 
+  const web = findWeb(dir, appName);
+  if (web.error) throw new Error(web.error);
+
   return {
     appName,
     dir,
@@ -82,7 +103,7 @@ export async function loadPlugin(dir: string, appName: string): Promise<Discover
     api: fileOrNull(join(dir, 'api', 'router.ts')),
     schema: fileOrNull(join(dir, 'db', 'schema.ts')),
     sidecar: findSidecar(dir),
-    web: findWeb(dir),
+    web: web.web,
   };
 }