diff --git a/.gitignore b/.gitignore
index 6da9605..b20d04d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,6 @@ web/sites/default/files/*
 .env
 
 node_modules/
+
+# Downloaded at image build (Dockerfile)
+web/modules/custom/riverside_pt/js/vendor/
diff --git a/Dockerfile b/Dockerfile
index 7ef7702..7636c9d 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -113,10 +113,21 @@ COPY --from=node-build /build/web/modules/custom/riverside_pt/css/app.css \
     web/modules/custom/riverside_pt/css/app.css
 COPY config/sync/ config/sync/
 
-# Download FullCalendar and lock settings.php in one layer
+# Download FullCalendar and Preact, and lock settings.php in one layer.
+# Preact (with its hooks and htm's html``) is htm's single-file standalone
+# build, served from the site: the components used to import Preact, its
+# hooks and htm/preact from esm.sh separately, and when htm/preact started
+# resolving to Preact 11 while the rest stayed on 10, every component
+# rendered nothing. Pinned by version and checksum.
 ARG FULLCALENDAR_VERSION=6.1.15
+ARG HTM_VERSION=3.1.1
+ARG HTM_PREACT_STANDALONE_SHA256=72284e8e9079c87817145df1110f74e8a2aa040b2fc384922e18dfcb46fc1fd7
 RUN curl -fsSL "https://cdn.jsdelivr.net/npm/fullcalendar@${FULLCALENDAR_VERSION}/index.global.min.js" \
          -o web/modules/custom/riverside_pt/js/fullcalendar.min.js \
+    && mkdir -p web/modules/custom/riverside_pt/js/vendor \
+    && curl -fsSL "https://cdn.jsdelivr.net/npm/htm@${HTM_VERSION}/preact/standalone.module.js" \
+         -o web/modules/custom/riverside_pt/js/vendor/preact-standalone.js \
+    && echo "${HTM_PREACT_STANDALONE_SHA256}  web/modules/custom/riverside_pt/js/vendor/preact-standalone.js" | sha256sum -c - \
     && chmod 444 web/sites/default/settings.php
 
 EXPOSE 80
diff --git a/web/modules/custom/riverside_pt/js/components/rpt-appt-type.js b/web/modules/custom/riverside_pt/js/components/rpt-appt-type.js
index 27fd45b..4d327d3 100644
--- a/web/modules/custom/riverside_pt/js/components/rpt-appt-type.js
+++ b/web/modules/custom/riverside_pt/js/components/rpt-appt-type.js
@@ -1,6 +1,4 @@
-import { h, render } from "https://esm.sh/preact@10";
-import { useState } from "https://esm.sh/preact@10/hooks";
-import { html } from "https://esm.sh/htm@3/preact";
+import { h, render, useState, html } from "../vendor/preact-standalone.js";
 
 const TYPES = [
   { id: "diagnostic", label: "Diagnostic Assessment", duration: "60 MINS" },
diff --git a/web/modules/custom/riverside_pt/js/components/rpt-booking.js b/web/modules/custom/riverside_pt/js/components/rpt-booking.js
index 07d8982..2f309a7 100644
--- a/web/modules/custom/riverside_pt/js/components/rpt-booking.js
+++ b/web/modules/custom/riverside_pt/js/components/rpt-booking.js
@@ -1,6 +1,4 @@
-import { h, render } from "https://esm.sh/preact@10";
-import { useState, useEffect, useRef, useMemo } from "https://esm.sh/preact@10/hooks";
-import { html } from "https://esm.sh/htm@3/preact";
+import { h, render, useState, useEffect, useRef, useMemo, html } from "../vendor/preact-standalone.js";
 
 const TYPES = [
   { id: "diagnostic", label: "Diagnostic Assessment", duration: "60 MINS" },
diff --git a/web/modules/custom/riverside_pt/js/components/rpt-carousel.js b/web/modules/custom/riverside_pt/js/components/rpt-carousel.js
index 74d4aa8..d1d4ef5 100644
--- a/web/modules/custom/riverside_pt/js/components/rpt-carousel.js
+++ b/web/modules/custom/riverside_pt/js/components/rpt-carousel.js
@@ -1,6 +1,4 @@
-import { h, render } from 'https://esm.sh/preact@10';
-import { useState, useLayoutEffect, useRef } from 'https://esm.sh/preact@10/hooks';
-import { html } from 'https://esm.sh/htm@3/preact';
+import { h, render, useState, useLayoutEffect, useRef, html } from '../vendor/preact-standalone.js';
 
 const IMAGES = [
   { src: '/modules/custom/riverside_pt/images/hero.jpg', alt: 'Physical therapy session' },
diff --git a/web/modules/custom/riverside_pt/js/components/rpt-faq.js b/web/modules/custom/riverside_pt/js/components/rpt-faq.js
index b02d124..1ba3d0c 100644
--- a/web/modules/custom/riverside_pt/js/components/rpt-faq.js
+++ b/web/modules/custom/riverside_pt/js/components/rpt-faq.js
@@ -1,6 +1,4 @@
-import { h, render } from "https://esm.sh/preact@10";
-import { useState } from "https://esm.sh/preact@10/hooks";
-import { html } from "https://esm.sh/htm@3/preact";
+import { h, render, useState, html } from "../vendor/preact-standalone.js";
 
 const FAQS = [
   {
diff --git a/web/modules/custom/riverside_pt/js/components/rpt-testimonials.js b/web/modules/custom/riverside_pt/js/components/rpt-testimonials.js
index e97a1fc..1c72e0c 100644
--- a/web/modules/custom/riverside_pt/js/components/rpt-testimonials.js
+++ b/web/modules/custom/riverside_pt/js/components/rpt-testimonials.js
@@ -1,6 +1,4 @@
-import { h, render } from "https://esm.sh/preact@10";
-import { useState, useEffect, useReducer, useRef } from "https://esm.sh/preact@10/hooks";
-import { html } from "https://esm.sh/htm@3/preact";
+import { h, render, useState, useEffect, useReducer, useRef, html } from "../vendor/preact-standalone.js";
 
 const TESTIMONIALS = [
   {
diff --git a/web/modules/custom/riverside_pt/js/components/rpt-toggle.js b/web/modules/custom/riverside_pt/js/components/rpt-toggle.js
index b1acd7f..ba72944 100644
--- a/web/modules/custom/riverside_pt/js/components/rpt-toggle.js
+++ b/web/modules/custom/riverside_pt/js/components/rpt-toggle.js
@@ -1,6 +1,4 @@
-import { h, render } from 'https://esm.sh/preact@10';
-import { useState } from 'https://esm.sh/preact@10/hooks';
-import { html } from 'https://esm.sh/htm@3/preact';
+import { h, render, useState, html } from '../vendor/preact-standalone.js';
 
 function Toggle({ label = 'Toggle' }) {
   const [checked, setChecked] = useState(false);