fix: only call scripts one per page

quartz/components/registry.ts

@@ -18,6 +18,7 @@ export interface RegisteredComponent {
 
 class ComponentRegistry {
   private components = new Map<string, RegisteredComponent>()
+  private instanceCache = new Map<string, QuartzComponent>()
 
   register(
     name: string,
@@ -40,6 +41,30 @@ class ComponentRegistry {
     return new Map(this.components)
   }
 
+  /**
+   * Instantiate a component constructor with options, returning a cached instance
+   * if the same constructor was already called with equivalent options.
+   * This prevents duplicate afterDOMLoaded scripts when the same component
+   * appears in multiple page-type layouts.
+   */
+  instantiate(constructor: QuartzComponentConstructor, options?: unknown): QuartzComponent {
+    const optsKey = options !== undefined ? JSON.stringify(options) : ""
+    // Use constructor identity + serialized options as cache key
+    // We store constructor name as a hint but rely on a unique id for identity
+    const ctorId =
+      (constructor as unknown as { __cacheId?: string }).__cacheId ??
+      ((constructor as unknown as { __cacheId: string }).__cacheId =
+        `ctor_${this.instanceCache.size}`)
+    const cacheKey = `${ctorId}:${optsKey}`
+
+    const cached = this.instanceCache.get(cacheKey)
+    if (cached) return cached
+
+    const instance = constructor(options)
+    this.instanceCache.set(cacheKey, instance)
+    return instance
+  }
+
   getAllComponents(): QuartzComponent[] {
     // Deduplicate by component reference (same constructor may be registered under multiple keys)
     const seen = new Set<QuartzComponent | QuartzComponentConstructor>()
@@ -50,7 +75,7 @@ class ComponentRegistry {
       try {
         let instance: QuartzComponent
         if (typeof r.component === "function") {
-          instance = (r.component as QuartzComponentConstructor)(undefined)
+          instance = this.instantiate(r.component as QuartzComponentConstructor, undefined)
         } else {
           instance = r.component as QuartzComponent
         }

quartz/plugins/loader/config-loader.ts

@@ -3,7 +3,7 @@ import path from "path"
 import YAML from "yaml"
 import { styleText } from "util"
 import { QuartzConfig, GlobalConfiguration, FullPageLayout } from "../../cfg"
-import { QuartzComponent } from "../../components/types"
+import { QuartzComponent, QuartzComponentConstructor } from "../../components/types"
 import { PluginTypes } from "../types"
 import {
   PluginManifest,
@@ -561,11 +561,12 @@ export async function loadQuartzLayout(layoutOverrides?: {
     const footerReg = componentRegistry.get("footer") ?? componentRegistry.get("Footer")
     if (footerReg) {
       if (typeof footerReg.component === "function" && !("displayName" in footerReg.component)) {
-        // It's a constructor, instantiate with options
+        // It's a constructor — use registry cache for consistent instances
         const opts = { ...footerEntry.options }
-        footer = (footerReg.component as Function)(
+        footer = componentRegistry.instantiate(
+          footerReg.component as QuartzComponentConstructor,
           Object.keys(opts).length > 0 ? opts : undefined,
-        ) as QuartzComponent
+        )
       } else {
         footer = footerReg.component as QuartzComponent
       }
@@ -648,11 +649,14 @@ function buildLayoutForEntries(
 
     let component: QuartzComponent
     if (typeof reg.component === "function" && !("displayName" in reg.component)) {
-      // It's a constructor, instantiate with options
+      // It's a constructor — use registry cache to avoid duplicate instances
+      // (and duplicate afterDOMLoaded scripts) across page-type layouts
       const opts = { ...entry.options }
-      component = (reg.component as Function)(
+      const optsArg = Object.keys(opts).length > 0 ? opts : undefined
-        Object.keys(opts).length > 0 ? opts : undefined,
+      component = componentRegistry.instantiate(
-      ) as QuartzComponent
+        reg.component as QuartzComponentConstructor,
+        optsArg,
+      )
     } else {
       component = reg.component as QuartzComponent
     }