diff --git a/app/assets/javascripts/discourse-markdown-it/src/features/custom-typographer-replacements.js b/app/assets/javascripts/discourse-markdown-it/src/features/custom-typographer-replacements.js
index 6d29476d961..2a3d6bc1e05 100644
--- a/app/assets/javascripts/discourse-markdown-it/src/features/custom-typographer-replacements.js
+++ b/app/assets/javascripts/discourse-markdown-it/src/features/custom-typographer-replacements.js
@@ -14,9 +14,9 @@
 // (r) (R) → ®
 // (p) (P) -> §
 
-let RARE_RE = /\+-|\.\.|\?\?\?\?|!!!!|,,|--|-->|<--|->|<-|<->|<-->/;
+export const RARE_RE = /\+-|\.\.|\?\?\?\?|!!!!|,,|--|-->|<--|->|<-|<->|<-->/;
 
-let SCOPED_ABBR_RE = /\((tm|pa)\)/gi;
+export const SCOPED_ABBR_RE = /\((tm|pa)\)/gi;
 let SCOPED_ABBR = {
   pa: "¶",
   tm: "™",
@@ -32,11 +32,37 @@ function replaceScoped(inlineTokens) {
   for (i = inlineTokens.length - 1; i >= 0; i--) {
     token = inlineTokens[i];
     if (token.type === "text") {
-      token.content = token.content.replace(SCOPED_ABBR_RE, replaceFn);
+      token.content = replaceScopedStr(token.content.replace);
     }
   }
 }
 
+export function replaceScopedStr(str) {
+  return str.replace(SCOPED_ABBR_RE, replaceFn);
+}
+
+export function replaceRareStr(str) {
+  return (
+    str
+      .replace(/\+-/g, "±")
+      // Custom arrows
+      .replace(/(^|\s)-{1,2}>(\s|$)/gm, "\u0020\u2192\u0020")
+      .replace(/(^|\s)<-{1,2}(\s|$)/gm, "\u0020\u2190\u0020")
+      .replace(/(^|\s)<-{1,2}>(\s|$)/gm, "\u0020\u2194\u0020")
+      // .., ..., ....... -> …
+      // but ?..... & !..... -> ?.. & !..
+      .replace(/\.{2,}/g, "…")
+      .replace(/([?!])…/g, "$1..")
+      .replace(/([?!]){4,}/g, "$1$1$1")
+      .replace(/,{2,}/g, ",")
+      // em-dash
+      .replace(/(^|[^-])---(?=[^-]|$)/gm, "$1\u2014")
+      // en-dash
+      .replace(/(^|\s)--(?=\s|$)/gm, "$1\u2013")
+      .replace(/(^|[^-\s])--(?=[^-\s]|$)/gm, "$1\u2013")
+  );
+}
+
 function replaceRare(inlineTokens) {
   let i,
     token,
@@ -47,23 +73,7 @@ function replaceRare(inlineTokens) {
 
     if (token.type === "text" && !inside_autolink) {
       if (RARE_RE.test(token.content)) {
-        token.content = token.content
-          .replace(/\+-/g, "±")
-          // Custom arrows
-          .replace(/(^|\s)-{1,2}>(\s|$)/gm, "\u0020\u2192\u0020")
-          .replace(/(^|\s)<-{1,2}(\s|$)/gm, "\u0020\u2190\u0020")
-          .replace(/(^|\s)<-{1,2}>(\s|$)/gm, "\u0020\u2194\u0020")
-          // .., ..., ....... -> …
-          // but ?..... & !..... -> ?.. & !..
-          .replace(/\.{2,}/g, "…")
-          .replace(/([?!])…/g, "$1..")
-          .replace(/([?!]){4,}/g, "$1$1$1")
-          .replace(/,{2,}/g, ",")
-          // em-dash
-          .replace(/(^|[^-])---(?=[^-]|$)/gm, "$1\u2014")
-          // en-dash
-          .replace(/(^|\s)--(?=\s|$)/gm, "$1\u2013")
-          .replace(/(^|[^-\s])--(?=[^-\s]|$)/gm, "$1\u2013");
+        token.content = replaceRareStr(token.content);
       }
     }
 
diff --git a/app/assets/javascripts/discourse/app/components/composer-container.hbs b/app/assets/javascripts/discourse/app/components/composer-container.hbs
index 21782830dca..8270b60d128 100644
--- a/app/assets/javascripts/discourse/app/components/composer-container.hbs
+++ b/app/assets/javascripts/discourse/app/components/composer-container.hbs
@@ -298,15 +298,17 @@
               </a>
             {{/if}}
 
-            <a
-              href
-              class="btn btn-default no-text mobile-preview"
-              title={{i18n "composer.show_preview"}}
-              {{on "click" this.composer.togglePreview}}
-              aria-label={{i18n "composer.show_preview"}}
-            >
-              {{d-icon "desktop"}}
-            </a>
+            {{#if this.composer.allowPreview}}
+              <a
+                href
+                class="btn btn-default no-text mobile-preview"
+                title={{i18n "composer.show_preview"}}
+                {{on "click" this.composer.togglePreview}}
+                aria-label={{i18n "composer.show_preview"}}
+              >
+                {{d-icon "desktop"}}
+              </a>
+            {{/if}}
 
             {{#if this.composer.showPreview}}
               <DButton
@@ -369,7 +371,7 @@
             {{/if}}
           </div>
 
-          {{#if this.site.desktopView}}
+          {{#if (and this.composer.allowPreview this.site.desktopView)}}
             <DButton
               @action={{this.composer.togglePreview}}
               @translatedTitle={{this.composer.toggleText}}
diff --git a/app/assets/javascripts/discourse/app/components/composer-editor.js b/app/assets/javascripts/discourse/app/components/composer-editor.js
index b8c7995136b..7838aeaff7b 100644
--- a/app/assets/javascripts/discourse/app/components/composer-editor.js
+++ b/app/assets/javascripts/discourse/app/components/composer-editor.js
@@ -208,6 +208,11 @@ export default class ComposerEditor extends Component {
       this._throttledSyncEditorAndPreviewScroll
     );
 
+    if (!this.site.mobileView) {
+      this.composer.set("showPreview", this.textManipulation.allowPreview);
+    }
+    this.composer.set("allowPreview", this.textManipulation.allowPreview);
+
     // Focus on the body unless we have a title
     if (!this.get("composer.model.canEditTitle")) {
       this.textManipulation.putCursorAtEnd();
@@ -862,14 +867,15 @@ export default class ComposerEditor extends Component {
 
   @action
   extraButtons(toolbar) {
-    toolbar.addButton({
-      id: "quote",
-      group: "fontStyles",
-      icon: "far-comment",
-      sendAction: this.composer.importQuote,
-      title: "composer.quote_post_title",
-      unshift: true,
-    });
+    // TODO remove this and all "importQuote" refs
+    // toolbar.addButton({
+    //   id: "quote",
+    //   group: "fontStyles",
+    //   icon: "far-comment",
+    //   sendAction: this.composer.importQuote,
+    //   title: "composer.quote_post_title",
+    //   unshift: true,
+    // });
 
     if (
       this.composer.allowUpload &&
diff --git a/app/assets/javascripts/discourse/app/components/composer/toggle-switch.gjs b/app/assets/javascripts/discourse/app/components/composer/toggle-switch.gjs
new file mode 100644
index 00000000000..970f3f32225
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/components/composer/toggle-switch.gjs
@@ -0,0 +1,35 @@
+import concatClass from "discourse/helpers/concat-class";
+import icon from "discourse-common/helpers/d-icon";
+
+const ComposerToggleSwitch = <template>
+  <div class="composer-toggle-switch">
+    <label class="composer-toggle-switch__label">
+      {{! template-lint-disable no-redundant-role }}
+      <button
+        class="composer-toggle-switch__checkbox"
+        type="button"
+        role="switch"
+        aria-checked={{if @state "true" "false"}}
+        ...attributes
+      ></button>
+      {{! template-lint-enable no-redundant-role }}
+
+      <span class="composer-toggle-switch__checkbox-slider">
+        <span
+          class={{concatClass
+            "composer-toggle-switch__left-icon"
+            (unless @state "--active")
+          }}
+        >{{icon "fab-markdown"}}</span>
+        <span
+          class={{concatClass
+            "composer-toggle-switch__right-icon"
+            (if @state "--active")
+          }}
+        >{{icon "a"}}</span>
+      </span>
+    </label>
+  </div>
+</template>;
+
+export default ComposerToggleSwitch;
diff --git a/app/assets/javascripts/discourse/app/components/d-editor.hbs b/app/assets/javascripts/discourse/app/components/d-editor.hbs
index f509d8e73a9..d09e11a3bb6 100644
--- a/app/assets/javascripts/discourse/app/components/d-editor.hbs
+++ b/app/assets/javascripts/discourse/app/components/d-editor.hbs
@@ -8,7 +8,14 @@
         {{if this.isEditorFocused 'in-focus'}}"
     >
       <div class="d-editor-button-bar" role="toolbar">
-        {{#each this.toolbar.groups as |group|}}
+        {{#if this.siteSettings.experimental_rich_editor}}
+            <Composer::ToggleSwitch
+              @state={{this.isRichEditorEnabled}}
+              {{on "click" this.toggleRichEditor}}
+            />
+          {{/if}}
+
+          {{#each this.toolbar.groups as |group|}}
           {{#each group.buttons as |b|}}
             {{#if (b.condition this)}}
               {{#if b.popupMenu}}
@@ -46,7 +53,7 @@
         @value={{this.value}}
         @placeholder={{this.placeholderTranslated}}
         @disabled={{this.disabled}}
-        @change={{this.change}}
+        @change={{this.onChange}}
         @focusIn={{this.handleFocusIn}}
         @focusOut={{this.handleFocusOut}}
         @id={{this.textAreaId}}
diff --git a/app/assets/javascripts/discourse/app/components/d-editor.js b/app/assets/javascripts/discourse/app/components/d-editor.js
index 5d228de9830..fcbd91405f3 100644
--- a/app/assets/javascripts/discourse/app/components/d-editor.js
+++ b/app/assets/javascripts/discourse/app/components/d-editor.js
@@ -1,3 +1,4 @@
+import { tracked } from "@glimmer/tracking";
 import Component from "@ember/component";
 import { action } from "@ember/object";
 import { getOwner } from "@ember/owner";
@@ -56,8 +57,8 @@ export default class DEditor extends Component {
   @service("emoji-store") emojiStore;
   @service modal;
 
-  editorComponent = TextareaEditor;
-  textManipulation;
+  @tracked editorComponent;
+  @tracked textManipulation;
 
   ready = false;
   lastSel = null;
@@ -73,10 +74,19 @@ export default class DEditor extends Component {
     },
   };
 
-  init() {
+  async init() {
     super.init(...arguments);
 
     this.register = getRegister(this);
+
+    if (
+      this.siteSettings.experimental_rich_editor &&
+      this.keyValueStore.get("d-editor-prefers-rich-editor") === "true"
+    ) {
+      this.editorComponent = await this.loadProsemirrorEditor();
+    } else {
+      this.editorComponent = TextareaEditor;
+    }
   }
 
   @discourseComputed("placeholder")
@@ -188,7 +198,12 @@ export default class DEditor extends Component {
   @discourseComputed()
   toolbar() {
     const toolbar = new Toolbar(
-      this.getProperties("site", "siteSettings", "showLink", "capabilities")
+      this.getProperties(
+        "appEvents",
+        "siteSettings",
+        "showLink",
+        "capabilities"
+      )
     );
     toolbar.context = this;
 
@@ -624,7 +639,7 @@ export default class DEditor extends Component {
 
   @action
   setupEditor(textManipulation) {
-    this.set("textManipulation", textManipulation);
+    this.textManipulation = textManipulation;
 
     const destroyEvents = this.setupEvents();
 
@@ -649,6 +664,40 @@ export default class DEditor extends Component {
     };
   }
 
+  @action
+  async toggleRichEditor() {
+    this.editorComponent = this.isRichEditorEnabled
+      ? TextareaEditor
+      : await this.loadProsemirrorEditor();
+    scheduleOnce("afterRender", this, this.focus);
+
+    this.keyValueStore.set({
+      key: "d-editor-prefers-rich-editor",
+      value: this.isRichEditorEnabled,
+    });
+  }
+
+  async loadProsemirrorEditor() {
+    this.prosemirrorEditorClass ??= (
+      await import("discourse/static/prosemirror/components/prosemirror-editor")
+    ).default;
+    return this.prosemirrorEditorClass;
+  }
+
+  focus() {
+    this.textManipulation.focus();
+  }
+
+  @action
+  onChange(event) {
+    this.set("value", event?.target?.value);
+    this.change?.(event);
+  }
+
+  get isRichEditorEnabled() {
+    return this.editorComponent === this.prosemirrorEditorClass;
+  }
+
   setupEvents() {
     const textManipulation = this.textManipulation;
 
diff --git a/app/assets/javascripts/discourse/app/lib/composer/rich-editor-extensions.js b/app/assets/javascripts/discourse/app/lib/composer/rich-editor-extensions.js
new file mode 100644
index 00000000000..1407fa40cf4
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/lib/composer/rich-editor-extensions.js
@@ -0,0 +1,208 @@
+const CUSTOM_NODE = {};
+const CUSTOM_MARK = {};
+const CUSTOM_PARSER = {};
+const CUSTOM_NODE_SERIALIZER = {};
+const CUSTOM_MARK_SERIALIZER = {};
+const CUSTOM_NODE_VIEW = {};
+const CUSTOM_INPUT_RULES = [];
+const CUSTOM_PLUGINS = [];
+
+const MULTIPLE_ALLOWED = { span: true, wrap_bbcode: false, bbcode: true };
+
+/**
+ * @typedef {import('prosemirror-state').PluginSpec} PluginSpec
+ * @typedef {((pluginClass: typeof import('prosemirror-state').Plugin) => PluginSpec)} RichPluginFn
+ * @typedef {PluginSpec | RichPluginFn} RichPlugin
+ *
+ * @typedef {Object} RichEditorExtension
+ * @property {Object<string, import('prosemirror-model').NodeSpec>} [nodeSpec]
+ *   Map containing Prosemirror node spec definitions, each key being the node name
+ *   See https://prosemirror.net/docs/ref/#model.NodeSpec
+ * @property {Object<string, import('prosemirror-model').MarkSpec>} [markSpec]
+ *   Map containing Prosemirror mark spec definitions, each key being the mark name
+ *   See https://prosemirror.net/docs/ref/#model.MarkSpec
+ * @property {Array<typeof import("prosemirror-inputrules").InputRule>} [inputRules]
+ *   Prosemirror input rules. See https://prosemirror.net/docs/ref/#inputrules.InputRule
+ *   can be a function returning an array or an array of input rules
+ * @property {Object<string, import('prosemirror-markdown').NodeSerializerSpec>} [serializeNode]
+ *   Node serialization definition
+ * @property {Object<string, import('prosemirror-markdown').MarkSerializerSpec>} [serializeMark]
+ *   Mark serialization definition
+ * @property {Object<string, import('prosemirror-markdown').ParseSpec>} [parse]
+ *   Markdown-it token parse definition
+ * @property {Array<RichPlugin>} [plugins]
+ *    ProseMirror plugins
+ * @property {Object<string, import('prosemirror-view').NodeView>} [nodeViews]
+ */
+
+/**
+ * Register an extension for the rich editor
+ *
+ * @param {RichEditorExtension} extension
+ */
+export function registerRichEditorExtension(extension) {
+  if (extension.nodeSpec) {
+    Object.entries(extension.nodeSpec).forEach(([name, spec]) => {
+      addNode(name, spec);
+    });
+  }
+
+  if (extension.markSpec) {
+    Object.entries(extension.markSpec).forEach(([name, spec]) => {
+      addMark(name, spec);
+    });
+  }
+
+  if (extension.inputRules) {
+    addInputRule(extension.inputRules);
+  }
+
+  if (extension.serializeNode) {
+    Object.entries(extension.serializeNode).forEach(([name, serialize]) => {
+      addNodeSerializer(name, serialize);
+    });
+  }
+
+  if (extension.serializeMark) {
+    Object.entries(extension.serializeMark).forEach(([name, serialize]) => {
+      addMarkSerializer(name, serialize);
+    });
+  }
+
+  if (extension.parse) {
+    Object.entries(extension.parse).forEach(([name, parse]) => {
+      addParser(name, parse);
+    });
+  }
+
+  if (extension.plugins instanceof Array) {
+    extension.plugins.forEach(addPlugin);
+  } else if (extension.plugins) {
+    addPlugin(extension.plugins);
+  }
+
+  if (extension.nodeViews) {
+    Object.entries(extension.nodeViews).forEach(([name, nodeViews]) => {
+      addNodeView(name, nodeViews);
+    });
+  }
+}
+
+function addNode(type, spec) {
+  CUSTOM_NODE[type] = spec;
+}
+export function getNodes() {
+  return CUSTOM_NODE;
+}
+
+function addMark(type, spec) {
+  CUSTOM_MARK[type] = spec;
+}
+export function getMarks() {
+  return CUSTOM_MARK;
+}
+
+function addNodeView(type, NodeViewClass) {
+  CUSTOM_NODE_VIEW[type] = (node, view, getPos) =>
+    new NodeViewClass(node, view, getPos);
+}
+export function getNodeViews() {
+  return CUSTOM_NODE_VIEW;
+}
+
+function addInputRule(rule) {
+  CUSTOM_INPUT_RULES.push(rule);
+}
+export function getInputRules() {
+  return CUSTOM_INPUT_RULES;
+}
+
+function addPlugin(plugin) {
+  CUSTOM_PLUGINS.push(plugin);
+}
+export function getPlugins() {
+  return CUSTOM_PLUGINS;
+}
+
+function generateMultipleParser(tokenName, list, isOpenClose) {
+  if (isOpenClose) {
+    return {
+      [`${tokenName}_open`](state, token, tokens, i) {
+        if (!list) {
+          return;
+        }
+
+        for (let parser of list) {
+          if (parser(state, token, tokens, i)) {
+            return;
+          }
+        }
+
+        // No support for nested missing definitions
+        state[`skip${tokenName}Close`] ??= [];
+      },
+      [`${tokenName}_close`](state) {
+        if (!list) {
+          return;
+        }
+
+        if (state[`skip${tokenName}Close`]) {
+          state[`skip${tokenName}Close`] = false;
+          return;
+        }
+
+        state.closeNode();
+      },
+    };
+  } else {
+    return {
+      [tokenName](state, token, tokens, i) {
+        if (!list) {
+          return;
+        }
+
+        for (let parser of list) {
+          if (parser(state, token, tokens, i)) {
+            return;
+          }
+        }
+      },
+    };
+  }
+}
+
+function addParser(token, parse) {
+  if (MULTIPLE_ALLOWED[token] !== undefined) {
+    CUSTOM_PARSER[token] ??= [];
+    CUSTOM_PARSER[token].push(parse);
+    return;
+  }
+  CUSTOM_PARSER[token] = parse;
+}
+
+export function getParsers() {
+  const parsers = { ...CUSTOM_PARSER };
+  for (let [token, isOpenClose] of Object.entries(MULTIPLE_ALLOWED)) {
+    delete parsers[token];
+    Object.assign(
+      parsers,
+      generateMultipleParser(token, CUSTOM_PARSER[token], isOpenClose)
+    );
+  }
+
+  return parsers;
+}
+
+function addNodeSerializer(node, serialize) {
+  CUSTOM_NODE_SERIALIZER[node] = serialize;
+}
+export function getNodeSerializers() {
+  return CUSTOM_NODE_SERIALIZER;
+}
+
+function addMarkSerializer(mark, serialize) {
+  CUSTOM_MARK_SERIALIZER[mark] = serialize;
+}
+export function getMarkSerializers() {
+  return CUSTOM_MARK_SERIALIZER;
+}
diff --git a/app/assets/javascripts/discourse/app/lib/plugin-api.gjs b/app/assets/javascripts/discourse/app/lib/plugin-api.gjs
index 021bc016243..2d6d13d434f 100644
--- a/app/assets/javascripts/discourse/app/lib/plugin-api.gjs
+++ b/app/assets/javascripts/discourse/app/lib/plugin-api.gjs
@@ -3,8 +3,9 @@
 // docs/CHANGELOG-JAVASCRIPT-PLUGIN-API.md whenever you change the version
 // using the format described at https://keepachangelog.com/en/1.0.0/.
 
-export const PLUGIN_API_VERSION = "1.39.2";
+export const PLUGIN_API_VERSION = "1.40.0";
 
+import { registerRichEditorExtension } from "discourse/lib/composer/rich-editor-extensions";
 import $ from "jquery";
 import { h } from "virtual-dom";
 import { addAboutPageActivity } from "discourse/components/about-page";
@@ -3407,6 +3408,10 @@ class PluginApi {
     registeredTabs.push(tab);
   }
 
+  registerRichEditorExtension(extension) {
+    registerRichEditorExtension(extension);
+  }
+
   #deprecatedWidgetOverride(widgetName, override) {
     // insert here the code to handle widget deprecations, e.g. for the header widgets we used:
     // if (DEPRECATED_HEADER_WIDGETS.includes(widgetName)) {
diff --git a/app/assets/javascripts/discourse/app/lib/text.js b/app/assets/javascripts/discourse/app/lib/text.js
index 56cfc70b897..74c17966895 100644
--- a/app/assets/javascripts/discourse/app/lib/text.js
+++ b/app/assets/javascripts/discourse/app/lib/text.js
@@ -56,7 +56,7 @@ export async function parseMentions(markdown, options) {
   return await withEngine("parseMentions", markdown, options);
 }
 
-function emojiOptions() {
+export function emojiOptions() {
   let siteSettings = helperContext().siteSettings;
   let context = helperContext();
   if (!siteSettings.enable_emoji) {
diff --git a/app/assets/javascripts/discourse/app/lib/textarea-text-manipulation.js b/app/assets/javascripts/discourse/app/lib/textarea-text-manipulation.js
index 80e40737563..7c667d41ceb 100644
--- a/app/assets/javascripts/discourse/app/lib/textarea-text-manipulation.js
+++ b/app/assets/javascripts/discourse/app/lib/textarea-text-manipulation.js
@@ -35,7 +35,7 @@ const FOUR_SPACES_INDENT = "4-spaces-indent";
 
 // Our head can be a static string or a function that returns a string
 // based on input (like for numbered lists).
-export function getHead(head, prev) {
+function getHead(head, prev) {
   if (typeof head === "string") {
     return [head, head.length];
   } else {
@@ -76,6 +76,10 @@ export default class TextareaTextManipulation {
     return this.textarea.value;
   }
 
+  get allowPreview() {
+    return true;
+  }
+
   // ensures textarea scroll position is correct
   blurAndFocus() {
     this.textarea?.blur();
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/components/prosemirror-editor.gjs b/app/assets/javascripts/discourse/app/static/prosemirror/components/prosemirror-editor.gjs
new file mode 100644
index 00000000000..4bb0ba6f842
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/components/prosemirror-editor.gjs
@@ -0,0 +1,147 @@
+import Component from "@glimmer/component";
+import { tracked } from "@glimmer/tracking";
+import { action } from "@ember/object";
+import { guidFor } from "@ember/object/internals";
+import { getOwner } from "@ember/owner";
+import didInsert from "@ember/render-modifiers/modifiers/did-insert";
+import willDestroy from "@ember/render-modifiers/modifiers/will-destroy";
+import { service } from "@ember/service";
+import "../extensions";
+import {
+  getNodeViews,
+  getPlugins,
+} from "discourse/lib/composer/rich-editor-extensions";
+import { createHighlight } from "../plugins/code-highlight";
+import { baseKeymap } from "prosemirror-commands";
+import { dropCursor } from "prosemirror-dropcursor";
+import { gapCursor } from "prosemirror-gapcursor";
+import { history } from "prosemirror-history";
+import { keymap } from "prosemirror-keymap";
+import { EditorState, Plugin } from "prosemirror-state";
+import { EditorView } from "prosemirror-view";
+import { bind } from "discourse-common/utils/decorators";
+import { convertFromMarkdown } from "../lib/parser";
+import TextManipulation from "../lib/text-manipulation";
+import { createSchema } from "../lib/schema";
+import { convertToMarkdown } from "../lib/serializer";
+import { buildInputRules } from "../plugins/inputrules";
+import { buildKeymap } from "../plugins/keymap";
+import placeholder from "../plugins/placeholder";
+
+export default class ProsemirrorEditor extends Component {
+  @service appEvents;
+  @service menu;
+  @service siteSettings;
+  @tracked rootElement;
+  editorContainerId = guidFor(this);
+  schema = createSchema();
+  view;
+  state;
+  plugins = this.args.plugins;
+
+  @action
+  async setup() {
+    this.rootElement = document.getElementById(this.editorContainerId);
+
+    const keymapFromArgs = Object.entries(this.args.keymap).reduce(
+      (acc, [key, value]) => {
+        // original keymap uses itsatrap format
+        acc[key.replaceAll("+", "-")] = value;
+        return acc;
+      },
+      {}
+    );
+
+    this.plugins ??= [
+      buildInputRules(this.schema),
+      // TODO buildPasteRules(),
+      keymap(buildKeymap(this.schema, keymapFromArgs)),
+      keymap(baseKeymap),
+      dropCursor({ color: "var(--primary)" }),
+      gapCursor(),
+      history(),
+      placeholder(this.args.placeholder),
+      createHighlight(),
+      ...getPlugins().map((plugin) =>
+        // can be either a function that receives the Plugin class,
+        // or a plugin spec to be passed directly to the Plugin constructor
+        typeof plugin === "function" ? plugin(Plugin) : new Plugin(plugin)
+      ),
+    ];
+
+    this.state = EditorState.create({
+      schema: this.schema,
+      plugins: this.plugins,
+    });
+
+    this.view = new EditorView(this.rootElement, {
+      nodeViews: this.args.nodeViews ?? getNodeViews(),
+      state: this.state,
+      attributes: { class: "d-editor-input d-editor__editable" },
+      dispatchTransaction: (tr) => {
+        this.view.updateState(this.view.state.apply(tr));
+
+        if (tr.docChanged && tr.getMeta("addToHistory") !== false) {
+          // TODO(renato): avoid calling this on every change
+          const value = convertToMarkdown(this.view.state.doc);
+          this.args.change?.({ target: { value } });
+        }
+      },
+      handleDOMEvents: {
+        focus: () => {
+          this.args.focusIn?.();
+          return false;
+        },
+        blur: () => {
+          this.args.focusOut?.();
+          return false;
+        },
+      },
+      handleKeyDown: (view, event) => {
+        // this happens before the autocomplete event, so we check if it's open
+        // TODO(renato): find a better way to handle these events, or just a better check
+        return (
+          event.key === "Enter" && !!document.querySelector(".autocomplete")
+        );
+      },
+    });
+
+    this.textManipulation = new TextManipulation(getOwner(this), {
+      markdownOptions: this.args.markdownOptions,
+      schema: this.schema,
+      view: this.view,
+    });
+
+    this.destructor = this.args.onSetup(this.textManipulation);
+
+    await this.convertFromValue();
+  }
+
+  @bind
+  async convertFromValue() {
+    const doc = await convertFromMarkdown(this.schema, this.args.value);
+
+    // doc.check();
+    // console.log("Resulting doc:", doc);
+
+    const tr = this.state.tr
+      .replaceWith(0, this.state.doc.content.size, doc.content)
+      .setMeta("addToHistory", false);
+    this.view.updateState(this.view.state.apply(tr));
+  }
+
+  @action
+  teardown() {
+    this.destructor?.();
+  }
+
+  <template>
+    <div
+      id={{this.editorContainerId}}
+      class="d-editor__container"
+      {{didInsert this.setup}}
+      {{willDestroy this.teardown}}
+    >
+    </div>
+  </template>
+}
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/code-lang-selector.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/code-lang-selector.js
new file mode 100644
index 00000000000..899feb5e623
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/code-lang-selector.js
@@ -0,0 +1,60 @@
+import { common, createLowlight } from "lowlight";
+
+class CodeBlockWithLangSelectorNodeView {
+  constructor(node, view, getPos) {
+    this.node = node;
+    this.view = view;
+    this.getPos = getPos;
+    this.dom = document.createElement("div");
+    this.dom.style.position = "relative";
+
+    const select = document.createElement("select");
+    select.addEventListener("change", (e) =>
+      this.view.dispatch(
+        this.view.state.tr.setNodeMarkup(this.getPos(), null, {
+          params: e.target.value,
+        })
+      )
+    );
+    select.classList.add("d-editor__code-lang-select");
+
+    const empty = document.createElement("option");
+    empty.textContent = "";
+    select.appendChild(empty);
+
+    createLowlight(common)
+      .listLanguages()
+      .forEach((lang) => {
+        const option = document.createElement("option");
+        option.textContent = lang;
+        option.selected = lang === node.attrs.params;
+        select.appendChild(option);
+      });
+
+    this.dom.appendChild(select);
+
+    // TODO(renato): leaving with the keyboard to before the node doesn't work
+
+    const code = document.createElement("code");
+    this.dom.appendChild(document.createElement("pre")).appendChild(code);
+    this.contentDOM = code;
+  }
+
+  update(node) {
+    if (node.type !== this.node.type) {
+      return false;
+    }
+
+    this.node = node;
+
+    return true;
+  }
+
+  ignoreMutation() {
+    return true;
+  }
+}
+
+export default {
+  nodeViews: { code_block: CodeBlockWithLangSelectorNodeView },
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/emoji.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/emoji.js
new file mode 100644
index 00000000000..14b04ef7a1c
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/emoji.js
@@ -0,0 +1,71 @@
+import { buildEmojiUrl, emojiExists, isCustomEmoji } from "pretty-text/emoji";
+import { emojiOptions } from "discourse/lib/text";
+
+// TODO(renato): we need to avoid the invalid text:emoji: state (reminder to use isPunctChar to avoid deleting the space)
+export default {
+  nodeSpec: {
+    emoji: {
+      attrs: { code: {} },
+      inline: true,
+      group: "inline",
+      draggable: true,
+      selectable: false,
+      parseDOM: [
+        {
+          tag: "img.emoji",
+          getAttrs: (dom) => {
+            return { code: dom.getAttribute("alt").replace(/:/g, "") };
+          },
+        },
+      ],
+      toDOM: (node) => {
+        const opts = emojiOptions();
+        const code = node.attrs.code.toLowerCase();
+        const title = `:${code}:`;
+        const src = buildEmojiUrl(code, opts);
+
+        return [
+          "img",
+          {
+            class: isCustomEmoji(code, opts) ? "emoji emoji-custom" : "emoji",
+            alt: title,
+            title,
+            src,
+          },
+        ];
+      },
+      leafText: (node) => `:${node.attrs.code}:`,
+    },
+  },
+
+  inputRules: [
+    {
+      match: /(?<=^|\W):([^:]+):$/,
+      handler: (state, match, start, end) => {
+        if (emojiExists(match[1])) {
+          return state.tr.replaceWith(
+            start,
+            end,
+            state.schema.nodes.emoji.create({ code: match[1] })
+          );
+        }
+      },
+      options: { undoable: false },
+    },
+  ],
+
+  parse: {
+    emoji: {
+      node: "emoji",
+      getAttrs: (token) => ({
+        code: token.attrGet("alt").slice(1, -1),
+      }),
+    },
+  },
+
+  serializeNode: {
+    emoji: (state, node) => {
+      state.write(`:${node.attrs.code}:`);
+    },
+  },
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/hashtag.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/hashtag.js
new file mode 100644
index 00000000000..ef880673318
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/hashtag.js
@@ -0,0 +1,60 @@
+export default {
+  nodeSpec: {
+    hashtag: {
+      attrs: { name: {} },
+      inline: true,
+      group: "inline",
+      content: "text*",
+      atom: true,
+      draggable: true,
+      selectable: false,
+      parseDOM: [
+        {
+          tag: "a.hashtag-cooked",
+          preserveWhitespace: "full",
+          getAttrs: (dom) => {
+            return { name: dom.getAttribute("data-name") };
+          },
+        },
+      ],
+      toDOM: (node) => {
+        return [
+          "a",
+          { class: "hashtag-cooked", "data-name": node.attrs.name },
+          `#${node.attrs.name}`,
+        ];
+      },
+      leafText: (node) => `#${node.attrs.name}`,
+    },
+  },
+
+  inputRules: [
+    {
+      match: /#([\u00C0-\u1FFF\u2C00-\uD7FF\w:-]{1,101}) $/,
+      handler: (state, match, start, end) =>
+        state.selection.$from.nodeBefore?.type !== state.schema.nodes.hashtag &&
+        state.tr.replaceWith(start, end, [
+          state.schema.nodes.hashtag.create({ name: match[1] }),
+          state.schema.text(" "),
+        ]),
+      options: { undoable: false },
+    },
+  ],
+
+  parse: {
+    span: (state, token, tokens, i) => {
+      if (token.attrGet("class") === "hashtag-raw") {
+        state.openNode(state.schema.nodes.hashtag, {
+          name: tokens[i + 1].content.slice(1),
+        });
+        return true;
+      }
+    },
+  },
+
+  serializeNode: {
+    hashtag: (state, node) => {
+      state.write(`#${node.attrs.name}`);
+    },
+  },
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/heading.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/heading.js
new file mode 100644
index 00000000000..b3cbce766e7
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/heading.js
@@ -0,0 +1,22 @@
+export default {
+  nodeSpec: {
+    heading: {
+      attrs: { level: { default: 1 } },
+      // Overriding ProseMirror's default to allow inline content
+      content: "inline*",
+      group: "block",
+      defining: true,
+      parseDOM: [
+        { tag: "h1", attrs: { level: 1 } },
+        { tag: "h2", attrs: { level: 2 } },
+        { tag: "h3", attrs: { level: 3 } },
+        { tag: "h4", attrs: { level: 4 } },
+        { tag: "h5", attrs: { level: 5 } },
+        { tag: "h6", attrs: { level: 6 } },
+      ],
+      toDOM(node) {
+        return ["h" + node.attrs.level, 0];
+      },
+    },
+  },
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/html-inline.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/html-inline.js
new file mode 100644
index 00000000000..34d23793655
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/html-inline.js
@@ -0,0 +1,92 @@
+const HTML_INLINE_MARKS = {
+  s: "strikethrough",
+  strike: "strikethrough",
+  strong: "strong",
+  b: "strong",
+  em: "em",
+  i: "em",
+  code: "code",
+};
+
+const ALLOWED_INLINE = [
+  "kbd",
+  "sup",
+  "sub",
+  "small",
+  "big",
+  "del",
+  "ins",
+  "mark",
+];
+
+export default {
+  nodeSpec: {
+    // TODO(renato): this node is hard to get past when at the end of a block
+    //   and is added to a newline unintentionally, investigate
+    html_inline: {
+      group: "inline",
+      inline: true,
+      content: "inline*",
+      attrs: { tag: {} },
+      parseDOM: ALLOWED_INLINE.map((tag) => ({ tag })),
+      toDOM: (node) => [node.attrs.tag, 0],
+    },
+  },
+  parse: {
+    // TODO(renato): it breaks if it's missing an end tag
+    html_inline: (state, token) => {
+      const openMatch = token.content.match(/^<([a-z]+)>$/u);
+      const closeMatch = token.content.match(/^<\/([a-z]+)>$/u);
+
+      if (openMatch) {
+        const tagName = openMatch[1];
+        const markName = HTML_INLINE_MARKS[tagName];
+        if (markName) {
+          state.openMark(state.schema.marks[markName].create());
+          return;
+        }
+
+        if (ALLOWED_INLINE.includes(tagName)) {
+          state.openNode(state.schema.nodeType("html_inline"), {
+            tag: tagName,
+          });
+        }
+
+        return;
+      }
+
+      if (closeMatch) {
+        const tagName = closeMatch[1];
+        const markName = HTML_INLINE_MARKS[tagName];
+        if (markName) {
+          state.closeMark(state.schema.marks[markName].create());
+          return;
+        }
+
+        if (ALLOWED_INLINE.includes(tagName)) {
+          state.closeNode();
+        }
+      }
+    },
+  },
+  serializeNode: {
+    html_inline(state, node) {
+      state.write(`<${node.attrs.tag}>`);
+      state.renderInline(node);
+      state.write(`</${node.attrs.tag}>`);
+    },
+  },
+  inputRules: {
+    match: new RegExp(`<(${ALLOWED_INLINE.join("|")})>`),
+    handler: (state, match, start, end) => {
+      const tag = match[1];
+
+      // TODO not finished
+      state.tr.replaceWith(
+        start,
+        end,
+        state.schema.nodes.html_inline.create({ tag })
+      );
+    },
+  },
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/image.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/image.js
new file mode 100644
index 00000000000..a977ea858df
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/image.js
@@ -0,0 +1,170 @@
+import {
+  lookupCachedUploadUrl,
+  lookupUncachedUploadUrls,
+} from "pretty-text/upload-short-url";
+import { ajax } from "discourse/lib/ajax";
+import { isNumeric } from "discourse/lib/utilities";
+
+const PLACEHOLDER_IMG = "/images/transparent.png";
+
+const ALT_TEXT_REGEX =
+  /^(.*?)(?:\|(\d{1,4}x\d{1,4}))?(?:,\s*(\d{1,3})%)?(?:\|(.*))?$/;
+
+export default {
+  nodeSpec: {
+    image: {
+      inline: true,
+      attrs: {
+        src: {},
+        alt: { default: null },
+        title: { default: null },
+        // Overriding ProseMirror's default node to support these attrs
+        width: { default: null },
+        height: { default: null },
+        "data-orig-src": { default: null },
+        "data-thumbnail": { default: false },
+        "data-scale": { default: null },
+        "data-placeholder": { default: null },
+      },
+      group: "inline",
+      draggable: true,
+      parseDOM: [
+        {
+          tag: "img[src]",
+          getAttrs(dom) {
+            return {
+              src: dom.getAttribute("src"),
+              title: dom.getAttribute("title"),
+              alt: dom.getAttribute("alt"),
+              width: dom.getAttribute("width"),
+              height: dom.getAttribute("height"),
+              "data-orig-src": dom.getAttribute("data-orig-src"),
+              "data-thumbnail": dom.hasAttribute("data-thumbnail"),
+            };
+          },
+        },
+      ],
+      toDOM(node) {
+        const width = node.attrs.width
+          ? (node.attrs.width * (node.attrs["data-scale"] || 100)) / 100
+          : undefined;
+        const height = node.attrs.height
+          ? (node.attrs.height * (node.attrs["data-scale"] || 100)) / 100
+          : undefined;
+
+        return ["img", { ...node.attrs, width, height }];
+      },
+    },
+  },
+
+  parse: {
+    image: {
+      node: "image",
+      getAttrs(token) {
+        const [, altText, dimensions, percent, extras] =
+          token.content.match(ALT_TEXT_REGEX);
+
+        const [width, height] = dimensions?.split("x") ?? [];
+
+        return {
+          src: token.attrGet("src"),
+          title: token.attrGet("title"),
+          alt: altText,
+          "data-orig-src": token.attrGet("data-orig-src"),
+          width,
+          height,
+          "data-scale":
+            percent && isNumeric(percent) ? parseInt(percent, 10) : undefined,
+          "data-thumbnail": extras === "thumbnail",
+        };
+      },
+    },
+  },
+
+  serializeNode: {
+    image(state, node) {
+      if (node.attrs["data-placeholder"]) {
+        return;
+      }
+
+      const alt = (node.attrs.alt || "").replace(/([\\[\]`])/g, "\\$1");
+      const scale = node.attrs["data-scale"]
+        ? `, ${node.attrs["data-scale"]}%`
+        : "";
+      const dimensions =
+        node.attrs.width && node.attrs.height
+          ? `|${node.attrs.width}x${node.attrs.height}${scale}`
+          : "";
+      const thumbnail = node.attrs["data-thumbnail"] ? "|thumbnail" : "";
+      const src = node.attrs["data-orig-src"] ?? node.attrs.src ?? "";
+      const escapedSrc = src.replace(/[\(\)]/g, "\\$&");
+      const title = node.attrs.title
+        ? ' "' + node.attrs.title.replace(/"/g, '\\"') + '"'
+        : "";
+
+      state.write(`![${alt}${dimensions}${thumbnail}](${escapedSrc}${title})`);
+    },
+  },
+
+  plugins: (Plugin) => {
+    const shortUrlResolver = new Plugin({
+      state: {
+        init() {
+          return [];
+        },
+        apply(tr, value) {
+          let updated = value.slice();
+
+          tr.doc.descendants((node, pos) => {
+            if (node.type.name === "image" && node.attrs["data-orig-src"]) {
+              if (node.attrs.src === PLACEHOLDER_IMG) {
+                updated.push({ pos, src: node.attrs["data-orig-src"] });
+              } else {
+                updated = updated.filter(
+                  (u) => u.src !== node.attrs["data-orig-src"]
+                );
+              }
+            }
+          });
+
+          return updated;
+        },
+      },
+
+      view() {
+        return {
+          update: async (view, prevState) => {
+            if (prevState.doc.eq(view.state.doc)) {
+              return;
+            }
+
+            const unresolvedUrls = shortUrlResolver.getState(view.state);
+
+            // Process only unresolved URLs
+            for (const unresolved of unresolvedUrls) {
+              const cachedUrl = lookupCachedUploadUrl(unresolved.src).url;
+              const url =
+                cachedUrl ||
+                (await lookupUncachedUploadUrls([unresolved.src], ajax))[0]
+                  ?.url;
+
+              if (url) {
+                const node = view.state.doc.nodeAt(unresolved.pos);
+                if (node) {
+                  const attrs = { ...node.attrs, src: url };
+                  const transaction = view.state.tr
+                    .setNodeMarkup(unresolved.pos, null, attrs)
+                    .setMeta("addToHistory", false);
+
+                  view.dispatch(transaction);
+                }
+              }
+            }
+          },
+        };
+      },
+    });
+
+    return shortUrlResolver;
+  },
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/index.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/index.js
new file mode 100644
index 00000000000..5cb299733fe
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/index.js
@@ -0,0 +1,35 @@
+import { registerRichEditorExtension } from "discourse/lib/composer/rich-editor-extensions";
+import codeLangSelector from "./code-lang-selector";
+import emojiExtension from "./emoji";
+import hashtagExtension from "./hashtag";
+import headingExtension from "./heading";
+import htmlInlineExtension from "./html-inline";
+import imageExtension from "./image";
+import linkExtension from "./link";
+import mentionExtension from "./mention";
+import quoteExtension from "./quote";
+import strikethroughExtension from "./strikethrough";
+import tableExtension from "./table";
+import typographerReplacements from "./typographer-replacements";
+import underlineExtension from "./underline";
+
+const defaultExtensions = [
+  emojiExtension,
+  // image must be after emoji
+  imageExtension,
+  hashtagExtension,
+  mentionExtension,
+  strikethroughExtension,
+  underlineExtension,
+  htmlInlineExtension,
+  linkExtension,
+  headingExtension,
+  typographerReplacements,
+  codeLangSelector,
+  quoteExtension,
+
+  // table must  be last
+  tableExtension,
+];
+
+defaultExtensions.forEach(registerRichEditorExtension);
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/link.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/link.js
new file mode 100644
index 00000000000..5c8ea12ae8c
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/link.js
@@ -0,0 +1,32 @@
+const HTTP_MAILTO_REGEX = new RegExp(
+  /(?:(?:(https|http|ftp)+):\/\/)?(?:\S+(?::\S*)?(@))?(?:(?:([a-z0-9][a-z0-9\-]*)?[a-z0-9]+)(?:\.(?:[a-z0-9\-])*[a-z0-9]+)*(?:\.(?:[a-z]{2,})(:\d{1,5})?))(?:\/[^\s]*)?\s $/
+);
+
+// TODO use site settings
+
+export default {
+  inputRules: [
+    {
+      match: HTTP_MAILTO_REGEX,
+      handler: (state, match, start, end) => {
+        const markType = state.schema.marks.link;
+
+        const resolvedStart = state.doc.resolve(start);
+        if (!resolvedStart.parent.type.allowsMarkType(markType)) {
+          return null;
+        }
+
+        const link = match[0].substring(0, match[0].length - 1);
+        const linkAttrs =
+          match[2] === "@"
+            ? { href: "mailto:" + link }
+            : { href: link, target: "_blank" };
+        const linkTo = markType.create(linkAttrs);
+        return state.tr
+          .removeMark(start, end, markType)
+          .addMark(start, end, linkTo)
+          .insertText(match[5], start);
+      },
+    },
+  ],
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/mention.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/mention.js
new file mode 100644
index 00000000000..4a5a13cc748
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/mention.js
@@ -0,0 +1,65 @@
+// TODO(renato): similar to emoji, avoid joining anything@mentions, as it's invalid markdown
+
+import { mentionRegex } from "pretty-text/mentions";
+
+export default {
+  nodeSpec: {
+    mention: {
+      attrs: { name: {} },
+      inline: true,
+      group: "inline",
+      content: "text*",
+      atom: true,
+      draggable: true,
+      selectable: false,
+      parseDOM: [
+        {
+          tag: "a.mention",
+          preserveWhitespace: "full",
+          getAttrs: (dom) => {
+            return { name: dom.getAttribute("data-name") };
+          },
+        },
+      ],
+      toDOM: (node) => {
+        return [
+          "a",
+          { class: "mention", "data-name": node.attrs.name },
+          `@${node.attrs.name}`,
+        ];
+      },
+      leafText: (node) => `@${node.attrs.name}`,
+    },
+  },
+
+  inputRules: [
+    {
+      // TODO: pass unicodeUsernames?
+      match: new RegExp(`(${mentionRegex().source}) $`),
+      handler: (state, match, start, end) =>
+        state.selection.$from.nodeBefore?.type !== state.schema.nodes.mention &&
+        state.tr.replaceWith(start, end, [
+          state.schema.nodes.mention.create({ name: match[1].slice(1) }),
+          state.schema.text(" "),
+        ]),
+      options: { undoable: false },
+    },
+  ],
+
+  parse: {
+    mention: {
+      block: "mention",
+      getAttrs: (token, tokens, i) => ({
+        // this is not ideal, but working around the mention_open/close structure
+        // a text is expected just after the mention_open token
+        name: tokens[i + 1].content.slice(1),
+      }),
+    },
+  },
+
+  serializeNode: {
+    mention: (state, node) => {
+      state.write(`@${node.attrs.name}`);
+    },
+  },
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/quote.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/quote.js
new file mode 100644
index 00000000000..ea897e64d51
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/quote.js
@@ -0,0 +1,90 @@
+export default {
+  nodeSpec: {
+    quote: {
+      content: "block+",
+      group: "block",
+      defining: true,
+      inline: false,
+      attrs: {
+        username: {},
+        postNumber: { default: null },
+        topicId: { default: null },
+        full: { default: null },
+      },
+      parseDOM: [
+        {
+          tag: "aside.quote",
+          getAttrs(dom) {
+            return {
+              username: dom.getAttribute("data-username"),
+              postNumber: dom.getAttribute("data-post"),
+              topicId: dom.getAttribute("data-topic"),
+              full: dom.getAttribute("data-full"),
+            };
+          },
+        },
+      ],
+      toDOM(node) {
+        const { username, postNumber, topicId, full } = node.attrs;
+        const attrs = { class: "quote" };
+        attrs["data-username"] = username;
+        attrs["data-post"] = postNumber;
+        attrs["data-topic"] = topicId;
+        attrs["data-full"] = full ? "true" : "false";
+
+        return ["aside", attrs, 0];
+      },
+    },
+    quote_title: {
+      content: "inline*",
+      group: "block",
+      inline: false,
+      parseDOM: [{ tag: "aside[data-username] > div.title" }],
+      atom: true,
+      draggable: false,
+      selectable: false,
+      toDOM() {
+        return ["div", { class: "title" }, 0];
+      },
+    },
+  },
+
+  parse: {
+    quote_header: { block: "quote_title" },
+    quote_controls: { ignore: true },
+    bbcode(state, token) {
+      if (token.tag === "aside") {
+        state.openNode(state.schema.nodes.quote, {
+          username: token.attrGet("data-username"),
+          postNumber: token.attrGet("data-post"),
+          topicId: token.attrGet("data-topic"),
+          full: token.attrGet("data-full"),
+        });
+        return true;
+      }
+
+      if (token.tag === "blockquote") {
+        state.openNode(state.schema.nodes.blockquote);
+        return true;
+      }
+    },
+  },
+
+  serializeNode: {
+    quote(state, node) {
+      const postNumber = node.attrs.postNumber
+        ? `, post:${node.attrs.postNumber}`
+        : "";
+      const topicId = node.attrs.topicId ? `, topic:${node.attrs.topicId}` : "";
+
+      state.write(`[quote="${node.attrs.username}${postNumber}${topicId}"]\n`);
+      node.forEach((n) => {
+        if (n.type.name === "blockquote") {
+          state.renderContent(n);
+        }
+      });
+      state.write("[/quote]\n");
+    },
+    quote_title() {},
+  },
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/strikethrough.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/strikethrough.js
new file mode 100644
index 00000000000..94042bccba8
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/strikethrough.js
@@ -0,0 +1,30 @@
+export default {
+  markSpec: {
+    strikethrough: {
+      parseDOM: [
+        { tag: "s" },
+        { tag: "del" },
+        {
+          getAttrs: (value) =>
+            /(^|[\s])line-through([\s]|$)/u.test(value) && null,
+          style: "text-decoration",
+        },
+      ],
+      toDOM() {
+        return ["s"];
+      },
+    },
+  },
+  parse: {
+    s: { mark: "strikethrough" },
+    bbcode_s: { mark: "strikethrough" },
+  },
+  serializeMark: {
+    strikethrough: {
+      open: "~~",
+      close: "~~",
+      mixable: true,
+      expelEnclosingWhitespace: true,
+    },
+  },
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/table.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/table.js
new file mode 100644
index 00000000000..591d1829a40
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/table.js
@@ -0,0 +1,176 @@
+// It makes sense to use prosemirror-tables for some of the table functionality,
+// but it has some differences from our structure (e.g. no thead/tbody).
+//
+// The main missing part of this extension for now is a UI companion
+
+// Example:
+//
+// | Left-aligned | Center-aligned | Right-aligned |
+// | :---         |     :---:      |          ---: |
+// | git status   | git status     | git status    |
+// | git diff     | git diff       | git diff      |
+
+export default {
+  nodeSpec: {
+    table: {
+      content: "(table_head | table_body)+",
+      group: "block",
+      tableRole: "table",
+      isolating: true,
+      parseDOM: [{ tag: "table" }],
+      toDOM() {
+        return ["table", 0];
+      },
+    },
+    table_head: {
+      content: "table_row",
+      tableRole: "head",
+      isolating: true,
+      parseDOM: [{ tag: "thead" }],
+      toDOM() {
+        return ["thead", 0];
+      },
+    },
+    table_body: {
+      content: "table_row*",
+      tableRole: "body",
+      isolating: true,
+      parseDOM: [{ tag: "tbody" }],
+      toDOM() {
+        return ["tbody", 0];
+      },
+    },
+    table_row: {
+      content: "(table_header_cell | table_cell)*",
+      tableRole: "row",
+      parseDOM: [{ tag: "tr" }],
+      toDOM() {
+        return ["tr", 0];
+      },
+    },
+    table_header_cell: {
+      content: "inline*",
+      tableRole: "header_cell",
+      attrs: { alignment: { default: null } },
+      parseDOM: [
+        {
+          tag: "th",
+          getAttrs(dom) {
+            return { alignment: dom.style.textAlign };
+          },
+        },
+      ],
+      toDOM(node) {
+        return ["th", { style: `text-align: ${node.attrs.alignment}` }, 0];
+      },
+    },
+    table_cell: {
+      content: "inline*",
+      tableRole: "cell",
+      attrs: { alignment: { default: null } },
+      parseDOM: [
+        {
+          tag: "td",
+          getAttrs(dom) {
+            return { alignment: dom.style.textAlign };
+          },
+        },
+      ],
+      toDOM(node) {
+        return [
+          "td",
+          {
+            style: node.attrs.alignment
+              ? `text-align: ${node.attrs.alignment}`
+              : undefined,
+          },
+          0,
+        ];
+      },
+    },
+  },
+  parse: {
+    table: { block: "table" },
+    thead: { block: "table_head" },
+    tbody: { block: "table_body" },
+    tr: { block: "table_row" },
+    th: {
+      block: "table_header_cell",
+      getAttrs(token) {
+        return {
+          alignment: token.attrGet("style")?.match(/text-align:(\w+)/)?.[1],
+        };
+      },
+    },
+    td: {
+      block: "table_cell",
+      getAttrs(token) {
+        return {
+          alignment: token.attrGet("style")?.match(/text-align:(\w+)/)?.[1],
+        };
+      },
+    },
+  },
+  serializeNode: {
+    // TODO(renato): state.renderInline should escape `|` if `state.inTable`
+    table(state, node) {
+      state.flushClose(1);
+
+      let headerBuffer = state.delim && state.atBlank() ? state.delim : "";
+      const prevInTable = state.inTable;
+      state.inTable = true;
+
+      // group is table_head or table_body
+      node.forEach((group, groupOffset, groupIndex) => {
+        group.forEach((row) => {
+          row.forEach((cell, cellOffset, cellIndex) => {
+            if (state.delim && state.atBlank()) {
+              state.out += state.delim;
+            }
+            state.out += cellIndex === 0 ? "| " : " | ";
+
+            cell.forEach((cellNode) => {
+              if (
+                cellNode.textContent === "" &&
+                cellNode.content.size === 0 &&
+                cellNode.type.name === "paragraph"
+              ) {
+                state.out += "  ";
+              } else {
+                state.closed = false;
+                state.render(cellNode, row, cellIndex);
+              }
+            });
+
+            // if table_head
+            if (groupIndex === 0) {
+              if (cell.attrs.alignment === "center") {
+                headerBuffer += "|:---:";
+              } else if (cell.attrs.alignment === "left") {
+                headerBuffer += "|:---";
+              } else if (cell.attrs.alignment === "right") {
+                headerBuffer += "|---:";
+              } else {
+                headerBuffer += "|----";
+              }
+            }
+          });
+
+          state.out += " |\n";
+
+          if (headerBuffer) {
+            state.out += `${headerBuffer}|\n`;
+            headerBuffer = undefined;
+          }
+        });
+      });
+      state.out += "\n";
+      state.inTable = prevInTable;
+    },
+    table_head() {},
+    table_body() {},
+    table_row() {},
+    table_header_cell() {},
+    table_cell() {},
+  },
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/typographer-replacements.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/typographer-replacements.js
new file mode 100644
index 00000000000..55766b82826
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/typographer-replacements.js
@@ -0,0 +1,33 @@
+import {
+  RARE_RE,
+  replaceRareStr,
+  replaceScopedStr,
+  SCOPED_ABBR_RE,
+} from "discourse-markdown-it/features/custom-typographer-replacements";
+
+// TODO(renato): should respect `enable_markdown_typographer`
+
+export default {
+  inputRules: [
+    {
+      match: new RegExp(`(${RARE_RE.source})$`),
+      handler: (state, match, start, end) => {
+        return state.tr.replaceWith(
+          start,
+          end,
+          state.schema.text(replaceRareStr(match[0]).trim())
+        );
+      },
+    },
+    {
+      match: new RegExp(`(${SCOPED_ABBR_RE.source})$`, "i"),
+      handler: (state, match, start, end) => {
+        return state.tr.replaceWith(
+          start,
+          end,
+          state.schema.text(replaceScopedStr(match[0]))
+        );
+      },
+    },
+  ],
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/underline.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/underline.js
new file mode 100644
index 00000000000..64f09b615a4
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/underline.js
@@ -0,0 +1,21 @@
+export default {
+  markSpec: {
+    underline: {
+      toDOM() {
+        return ["u", 0];
+      },
+      parseDOM: [{ tag: "u" }],
+    },
+  },
+  parse: {
+    bbcode_u: { mark: "underline" },
+  },
+  serializeMark: {
+    underline: {
+      open: "[u]",
+      close: "[/u]",
+      mixable: true,
+      expelEnclosingWhitespace: true,
+    },
+  },
+};
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/lib/parser.js b/app/assets/javascripts/discourse/app/static/prosemirror/lib/parser.js
new file mode 100644
index 00000000000..2caea7a20ec
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/lib/parser.js
@@ -0,0 +1,52 @@
+import { defaultMarkdownParser, MarkdownParser } from "prosemirror-markdown";
+import { getParsers } from "discourse/lib/composer/rich-editor-extensions";
+import { parseAsync } from "discourse/lib/text";
+
+// TODO(renato): We need a workaround for this parsing issue:
+//   https://github.com/ProseMirror/prosemirror-markdown/issues/82
+//   a solution may be a markStack in the state ignoring nested marks
+
+const [parseFunctions, parseDefinitions] = Object.entries(getParsers()).reduce(
+  ([funcs, nonFuncs], [key, value]) => {
+    if (typeof value === "function") {
+      funcs[key] = value;
+    } else {
+      nonFuncs[key] = value;
+    }
+    return [funcs, nonFuncs];
+  },
+  [{}, {}]
+);
+
+const parseTokens = {
+  ...defaultMarkdownParser.tokens,
+
+  // Custom
+  bbcode_b: { mark: "strong" },
+  bbcode_i: { mark: "em" },
+  // TODO(renato): html_block should be like a passthrough code block
+  html_block: { block: "paragraph", noCloseToken: true },
+  ...parseDefinitions,
+};
+
+// Overriding Prosemirror default parse definitions
+const postParseTokens = {
+  softbreak: (state) => state.addText("\n"),
+  ...parseFunctions,
+};
+
+export async function convertFromMarkdown(schema, text) {
+  const tokens = await parseAsync(text);
+
+  console.log("Converting tokens", tokens);
+
+  const dummyTokenizer = { parse: () => tokens };
+  const parser = new MarkdownParser(schema, dummyTokenizer, parseTokens);
+
+  // workaround for custom (fn) handlers
+  for (const [key, callback] of Object.entries(postParseTokens)) {
+    parser.tokenHandlers[key] = callback;
+  }
+
+  return parser.parse(text);
+}
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/lib/schema.js b/app/assets/javascripts/discourse/app/static/prosemirror/lib/schema.js
new file mode 100644
index 00000000000..0d1cb42e5cb
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/lib/schema.js
@@ -0,0 +1,21 @@
+import { schema as defaultMarkdownSchema } from "prosemirror-markdown";
+import { Schema } from "prosemirror-model";
+import {
+  getMarks,
+  getNodes,
+} from "discourse/lib/composer/rich-editor-extensions";
+
+export function createSchema() {
+  let nodes = defaultMarkdownSchema.spec.nodes;
+  let marks = defaultMarkdownSchema.spec.marks;
+
+  for (const [type, spec] of Object.entries(getNodes())) {
+    nodes = nodes.addToEnd(type, spec);
+  }
+
+  for (const [type, spec] of Object.entries(getMarks())) {
+    marks = marks.addToEnd(type, spec);
+  }
+
+  return new Schema({ nodes, marks });
+}
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/lib/serializer.js b/app/assets/javascripts/discourse/app/static/prosemirror/lib/serializer.js
new file mode 100644
index 00000000000..bddb334b170
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/lib/serializer.js
@@ -0,0 +1,31 @@
+import {
+  defaultMarkdownSerializer,
+  MarkdownSerializer,
+} from "prosemirror-markdown";
+import {
+  getMarkSerializers,
+  getNodeSerializers,
+} from "discourse/lib/composer/rich-editor-extensions";
+
+const serializeNodes = {
+  ...defaultMarkdownSerializer.nodes,
+
+  // Custom
+  hard_break(state) {
+    state.write("\n");
+  },
+  ...getNodeSerializers(),
+};
+
+const serializeMarks = {
+  ...defaultMarkdownSerializer.marks,
+
+  // Custom
+  ...getMarkSerializers(),
+};
+
+export function convertToMarkdown(doc) {
+  // console.log("Doc to serialize", doc);
+
+  return new MarkdownSerializer(serializeNodes, serializeMarks).serialize(doc);
+}
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/lib/text-manipulation.js b/app/assets/javascripts/discourse/app/static/prosemirror/lib/text-manipulation.js
new file mode 100644
index 00000000000..275ecc048d8
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/lib/text-manipulation.js
@@ -0,0 +1,446 @@
+import { setOwner } from "@ember/owner";
+import $ from "jquery";
+import { lift, setBlockType, toggleMark, wrapIn } from "prosemirror-commands";
+import { convertFromMarkdown } from "discourse/static/prosemirror/lib/parser";
+import { bind } from "discourse-common/utils/decorators";
+import { i18n } from "discourse-i18n";
+
+export default class TextManipulation {
+  markdownOptions;
+  /** @type {import("prosemirror-model").Schema} */
+  schema;
+  /** @type {import("prosemirror-view").EditorView} */
+  view;
+  $editorElement;
+  placeholder;
+  autocompleteHandler;
+
+  constructor(owner, { markdownOptions, schema, view }) {
+    setOwner(this, owner);
+    this.markdownOptions = markdownOptions;
+    this.schema = schema;
+    this.view = view;
+    this.$editorElement = $(view.dom);
+
+    this.placeholder = new PlaceholderHandler({ schema, view });
+    this.autocompleteHandler = new AutocompleteHandler({ schema, view });
+  }
+
+  /**
+   * The textual value of the selected text block
+   * @returns {string}
+   */
+  get value() {
+    const parent = this.view.state.selection.$head.parent;
+
+    return parent.textBetween(0, parent.nodeSize - 2, " ", " ");
+  }
+
+  getSelected(trimLeading, opts) {
+    const start = this.view.state.selection.from;
+    const end = this.view.state.selection.to;
+    const value = this.view.state.doc.textBetween(start, end, " ", " ");
+    return {
+      start,
+      end,
+      pre: "",
+      value,
+      post: "",
+    };
+  }
+
+  focus() {
+    this.view.focus();
+  }
+
+  blurAndFocus() {
+    this.focus();
+  }
+
+  putCursorAtEnd() {
+    // this.view.dispatch(
+    //   this.view.state.tr.setSelection(
+    //     TextSelection.create(this.view.state.doc, 0)
+    //   )
+    // );
+  }
+
+  autocomplete(options) {
+    return this.$editorElement.autocomplete(
+      options instanceof Object
+        ? { textHandler: this.autocompleteHandler, ...options }
+        : options
+    );
+  }
+
+  applySurroundSelection(head, tail, exampleKey, opts) {
+    this.applySurround(this.getSelected(), head, tail, exampleKey, opts);
+  }
+
+  applySurround(sel, head, tail, exampleKey, opts) {
+    const applySurroundMap = {
+      italic_text: this.schema.marks.em,
+      bold_text: this.schema.marks.strong,
+      code_title: this.schema.marks.code,
+    };
+
+    if (applySurroundMap[exampleKey]) {
+      toggleMark(applySurroundMap[exampleKey])(
+        this.view.state,
+        this.view.dispatch
+      );
+
+      return;
+    }
+
+    // TODO other cases, probably through md parser
+  }
+
+  async addText(sel, text, options) {
+    const doc = await convertFromMarkdown(
+      this.schema,
+      text,
+      this.markdownOptions
+    );
+
+    // assumes it returns a single block node
+    const content = doc.content.firstChild.content;
+
+    this.view.dispatch(
+      this.view.state.tr.replaceWith(sel.start, sel.end, content)
+    );
+  }
+
+  async insertBlock(block) {
+    const doc = await convertFromMarkdown(this.schema, block);
+
+    this.view.dispatch(
+      this.view.state.tr.replaceWith(
+        this.view.state.selection.from - 1,
+        this.view.state.selection.to,
+        doc.content.firstChild
+      )
+    );
+  }
+
+  applyList(_selection, head, exampleKey, opts) {
+    // This is similar to applySurround, but doing it line by line
+    // We may use markdown parsing as a fallback if we don't identify the exampleKey
+    // similarly to applySurround
+    // TODO to check actual applyList uses in the wild
+
+    let command;
+
+    const isInside = (type) => {
+      const $from = this.view.state.selection.$from;
+      for (let depth = $from.depth; depth > 0; depth--) {
+        const parent = $from.node(depth);
+        if (parent.type === type) {
+          return true;
+        }
+      }
+      return false;
+    };
+
+    if (exampleKey === "list_item") {
+      if (head === "* ") {
+        command = isInside(this.schema.nodes.bullet_list)
+          ? lift
+          : wrapIn(this.schema.nodes.bullet_list);
+      } else {
+        command = isInside(this.schema.nodes.ordered_list)
+          ? lift
+          : wrapIn(this.schema.nodes.ordered_list);
+      }
+    } else {
+      const applyListMap = {
+        blockquote_text: this.schema.nodes.blockquote,
+      };
+
+      if (applyListMap[exampleKey]) {
+        command = isInside(applyListMap[exampleKey])
+          ? lift
+          : wrapIn(applyListMap[exampleKey]);
+      }
+    }
+
+    command?.(this.view.state, this.view.dispatch);
+  }
+
+  formatCode() {
+    let command;
+
+    const selection = this.view.state.selection;
+
+    if (selection.$from.parent.type === this.schema.nodes.code_block) {
+      command = setBlockType(this.schema.nodes.paragraph);
+    } else if (
+      selection.$from.pos !== selection.$to.pos &&
+      selection.$from.parent === selection.$to.parent
+    ) {
+      command = toggleMark(this.schema.marks.code);
+    } else {
+      command = setBlockType(this.schema.nodes.code_block);
+    }
+
+    command?.(this.view.state, this.view.dispatch);
+  }
+
+  @bind
+  emojiSelected(code) {
+    const text = this.value.slice(0, this.getCaretPosition());
+    const captures = text.match(/\B:(\w*)$/);
+
+    if (!captures) {
+      if (text.match(/\S$/)) {
+        this.view.dispatch(
+          this.view.state.tr
+            .insertText(" ", this.view.state.selection.from)
+            .replaceSelectionWith(this.schema.nodes.emoji.create({ code }))
+        );
+      } else {
+        this.view.dispatch(
+          this.view.state.tr.replaceSelectionWith(
+            this.schema.nodes.emoji.create({ code })
+          )
+        );
+      }
+    } else {
+      let numOfRemovedChars = captures[1].length;
+      this.view.dispatch(
+        this.view.state.tr
+          .delete(
+            this.view.state.selection.from - numOfRemovedChars - 1,
+            this.view.state.selection.from
+          )
+          .replaceSelectionWith(this.schema.nodes.emoji.create({ code }))
+      );
+    }
+    this.focus();
+  }
+
+  @bind
+  paste(e) {
+    // TODO
+    console.log("paste");
+    // let { clipboard, canPasteHtml, canUpload } = clipboardHelpers(e, {
+    //   siteSettings: this.siteSettings,
+    //   canUpload: true,
+    // });
+
+    // console.log(clipboard);
+
+    e.preventDefault();
+    e.stopPropagation();
+    e.stopImmediatePropagation();
+  }
+
+  selectText() {
+    // TODO
+  }
+
+  @bind
+  inCodeBlock() {
+    return (
+      this.view.state.selection.$from.parent.type ===
+      this.schema.nodes.code_block
+    );
+  }
+
+  /**
+   * Gets the textual caret position within the selected text block
+   *
+   * @returns {number}
+   */
+  getCaretPosition() {
+    const { $anchor } = this.view.state.selection;
+
+    return $anchor.pos - $anchor.start();
+  }
+}
+
+class AutocompleteHandler {
+  /** @type {import("prosemirror-view").EditorView} */
+  view;
+  /** @type {import("prosemirror-model").Schema} */
+  schema;
+
+  constructor({ schema, view }) {
+    this.schema = schema;
+    this.view = view;
+  }
+
+  /**
+   * The textual value of the selected text block
+   * @returns {string}
+   */
+  get value() {
+    return this.view.state.selection.$head.nodeBefore?.textContent ?? "";
+  }
+
+  /**
+   * Replaces the term between start-end in the currently selected text block
+   *
+   * It uses input rules to convert it to a node if possible
+   *
+   * @param {number} start
+   * @param {number} end
+   * @param {String} term
+   */
+  async replaceTerm({ start, end, term }) {
+    const node = this.view.state.selection.$head.nodeBefore;
+    const from = this.view.state.selection.from - node.nodeSize + start;
+    const to = this.view.state.selection.from - node.nodeSize + end + 1;
+
+    // Alternative approach using inputRules, if `convertFromMarkdown` is too expensive
+    //
+    // let replaced;
+    // for (const plugin of this.view.state.plugins) {
+    //   if (plugin.spec.isInputRules) {
+    //     replaced ||= plugin.props.handleTextInput(this.view, from, to, term, null);
+    //   }
+    // }
+    //
+    // if (!replaced) {
+    //   this.view.dispatch(
+    //     this.view.state.tr.replaceWith(from, to, this.schema.text(term))
+    //   );
+    // }
+
+    const doc = await convertFromMarkdown(this.schema, term);
+
+    const tr = this.view.state.tr.replaceWith(
+      from,
+      to,
+      doc.content.firstChild.content
+    );
+    tr.insertText(" ", tr.selection.from);
+
+    this.view.dispatch(tr);
+  }
+
+  /**
+   * Gets the textual caret position within the selected text block
+   *
+   * @returns {number}
+   */
+  getCaretPosition() {
+    const node = this.view.state.selection.$head.nodeBefore;
+
+    if (!node?.isText) {
+      return 0;
+    }
+
+    return node.nodeSize;
+  }
+
+  /**
+   * Gets the caret coordinates within the selected text block
+   *
+   * @param {number} start
+   *
+   * @returns {{top: number, left: number}}
+   */
+  getCaretCoords(start) {
+    const node = this.view.state.selection.$head.nodeBefore;
+    const pos = this.view.state.selection.from - node.nodeSize + start;
+    const { left, top } = this.view.coordsAtPos(pos);
+
+    const rootRect = this.view.dom.getBoundingClientRect();
+
+    return {
+      left: left - rootRect.left,
+      top: top - rootRect.top,
+    };
+  }
+
+  inCodeBlock() {
+    // TODO
+    return false;
+  }
+}
+
+class PlaceholderHandler {
+  view;
+  schema;
+
+  constructor({ schema, view }) {
+    this.schema = schema;
+    this.view = view;
+  }
+
+  insert(file) {
+    const isEmptyParagraph =
+      this.view.state.selection.$from.parent.type.name === "paragraph" &&
+      this.view.state.selection.$from.parent.nodeSize === 2;
+
+    const imageNode = this.schema.nodes.image.create({
+      src: URL.createObjectURL(file.data),
+      alt: i18n("uploading_filename", { filename: file.name }),
+      title: file.id,
+      width: 120,
+      "data-placeholder": true,
+    });
+
+    this.view.dispatch(
+      this.view.state.tr.insert(
+        this.view.state.selection.from,
+        isEmptyParagraph
+          ? imageNode
+          : this.schema.nodes.paragraph.create(null, imageNode)
+      )
+    );
+  }
+
+  progress() {}
+  progressComplete() {}
+
+  cancelAll() {
+    this.view.state.doc.descendants((node, pos) => {
+      if (
+        node.type === this.schema.nodes.image &&
+        node.attrs["data-placeholder"]
+      ) {
+        this.view.dispatch(this.view.state.tr.delete(pos, pos + node.nodeSize));
+      }
+    });
+  }
+
+  cancel(file) {
+    this.view.state.doc.descendants((node, pos) => {
+      if (
+        node.type === this.schema.nodes.image &&
+        node.attrs["data-placeholder"] &&
+        node.attrs?.title === file.id
+      ) {
+        this.view.dispatch(this.view.state.tr.delete(pos, pos + node.nodeSize));
+      }
+    });
+  }
+
+  async success(file, markdown) {
+    let nodeToReplace = null;
+    this.view.state.doc.descendants((node, pos) => {
+      if (
+        node.type === this.schema.nodes.image &&
+        node.attrs["data-placeholder"] &&
+        node.attrs?.title === file.id
+      ) {
+        nodeToReplace = { node, pos };
+        return false;
+      }
+      return true;
+    });
+
+    // keeping compatibility with plugins that change the image node via markdown
+    const doc = await convertFromMarkdown(this.schema, markdown);
+
+    this.view.dispatch(
+      this.view.state.tr.replaceWith(
+        nodeToReplace.pos,
+        nodeToReplace.pos + nodeToReplace.node.nodeSize,
+        doc.content.firstChild.content
+      )
+    );
+  }
+}
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/plugins/code-highlight.js b/app/assets/javascripts/discourse/app/static/prosemirror/plugins/code-highlight.js
new file mode 100644
index 00000000000..6d77ece0d26
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/plugins/code-highlight.js
@@ -0,0 +1,13 @@
+import { common, createLowlight } from "lowlight";
+import { createHighlightPlugin } from "prosemirror-highlight";
+import { createParser } from "prosemirror-highlight/lowlight";
+
+export function createHighlight() {
+  const lowlight = createLowlight(common);
+  const parser = createParser(lowlight);
+
+  return createHighlightPlugin({
+    parser,
+    languageExtractor: (node) => node.attrs.params,
+  });
+}
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/plugins/inputrules.js b/app/assets/javascripts/discourse/app/static/prosemirror/plugins/inputrules.js
new file mode 100644
index 00000000000..ace19d2fc15
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/plugins/inputrules.js
@@ -0,0 +1,136 @@
+import {
+  InputRule,
+  inputRules,
+  smartQuotes,
+  textblockTypeInputRule,
+  wrappingInputRule,
+} from "prosemirror-inputrules";
+import { getInputRules } from "discourse/lib/composer/rich-editor-extensions";
+
+function orderedListRule(nodeType) {
+  return wrappingInputRule(
+    /^(\d+)\.\s$/,
+    nodeType,
+    (match) => ({ order: +match[1] }),
+    (match, node) => node.childCount + node.attrs.order === +match[1]
+  );
+}
+
+function bulletListRule(nodeType) {
+  return wrappingInputRule(/^\s*([-+*])\s$/, nodeType);
+}
+
+function headingRule(nodeType, maxLevel) {
+  return textblockTypeInputRule(
+    new RegExp("^(#{1," + maxLevel + "})\\s$"),
+    nodeType,
+    (match) => ({ level: match[1].length })
+  );
+}
+
+// https://discuss.prosemirror.net/t/input-rules-for-wrapping-marks/537
+function markInputRule(regexp, markType, getAttrs) {
+  return new InputRule(regexp, (state, match, start, end) => {
+    const attrs = getAttrs instanceof Function ? getAttrs(match) : getAttrs;
+    const tr = state.tr;
+
+    if (match[1]) {
+      let textStart = start + match[0].indexOf(match[1]);
+      let textEnd = textStart + match[1].length;
+      if (textEnd < end) {
+        tr.delete(textEnd, end);
+      }
+      if (textStart > start) {
+        tr.delete(start, textStart);
+      }
+      end = start + match[1].length;
+    }
+
+    tr.addMark(start, end, markType.create(attrs));
+    tr.removeStoredMark(markType);
+    return tr;
+  });
+}
+
+export function buildInputRules(schema) {
+  // TODO(renato) smartQuotes should respect `markdown_typographer_quotation_marks`
+  let rules = [...smartQuotes],
+    type;
+
+  if ((type = schema.nodes.blockquote)) {
+    rules.push(wrappingInputRule(/^\s*>\s$/, type));
+  }
+
+  if ((type = schema.nodes.ordered_list)) {
+    rules.push(orderedListRule(type));
+  }
+
+  if ((type = schema.nodes.bullet_list)) {
+    rules.push(bulletListRule(type));
+  }
+
+  if ((type = schema.nodes.code_block)) {
+    rules.push(textblockTypeInputRule(/^```$/, type));
+    rules.push(textblockTypeInputRule(/^ {4}$/, type));
+  }
+
+  if ((type = schema.nodes.heading)) {
+    rules.push(headingRule(type, 6));
+  }
+
+  const marks = schema.marks;
+  const markInputRules = [
+    markInputRule(/\*\*([^*]+)\*\*$/, marks.strong),
+    markInputRule(/(?<=^|\s)__([^_]+)__$/, marks.strong),
+
+    markInputRule(/(?:^|(?<!\*))\*([^*]+)\*$/, marks.em),
+    markInputRule(/(?<=^|\s)_([^_]+)_$/, marks.em),
+
+    markInputRule(
+      /\[([^\]]+)]\(([^)\s]+)(?:\s+[“"']([^“"']+)[”"'])?\)$/,
+      marks.link,
+      (match) => {
+        return { href: match[2], title: match[3] };
+      }
+    ),
+
+    markInputRule(/`([^`]+)`$/, marks.code),
+
+    markInputRule(/~~([^~]+)~~$/, marks.strikethrough),
+
+    markInputRule(/\[u]([^[]+)\[\/u]$/, marks.underline),
+  ];
+
+  rules = rules
+    .concat(markInputRules)
+    .concat(
+      getInputRules().flatMap((inputRule) =>
+        processInputRule(inputRule, schema)
+      )
+    );
+
+  return inputRules({ rules });
+}
+
+function processInputRule(inputRule, schema) {
+  if (inputRule instanceof Array) {
+    return inputRule.map(processInputRule);
+  }
+
+  if (inputRule instanceof Function) {
+    inputRule = inputRule({ schema, markInputRule });
+  }
+
+  if (inputRule instanceof InputRule) {
+    return inputRule;
+  }
+
+  if (
+    inputRule.match instanceof RegExp &&
+    inputRule.handler instanceof Function
+  ) {
+    return new InputRule(inputRule.match, inputRule.handler, inputRule.options);
+  }
+
+  throw new Error("Input rule must have a match regex and a handler function");
+}
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/plugins/keymap.js b/app/assets/javascripts/discourse/app/static/prosemirror/plugins/keymap.js
new file mode 100644
index 00000000000..909c137aa26
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/plugins/keymap.js
@@ -0,0 +1,101 @@
+import {
+  chainCommands,
+  exitCode,
+  joinDown,
+  joinUp,
+  lift,
+  selectParentNode,
+  setBlockType,
+  toggleMark,
+  wrapIn,
+} from "prosemirror-commands";
+import { redo, undo } from "prosemirror-history";
+import { undoInputRule } from "prosemirror-inputrules";
+import {
+  liftListItem,
+  sinkListItem,
+  splitListItem,
+} from "prosemirror-schema-list";
+
+const isMac =
+  typeof navigator !== "undefined"
+    ? /Mac|iP(hone|[oa]d)/.test(navigator.platform)
+    : false;
+
+// Updated from
+// https://github.com/ProseMirror/prosemirror-example-setup/blob/master/src/keymap.ts
+
+export function buildKeymap(schema, initialKeymap = {}, suppressKeys) {
+  let keys = initialKeymap,
+    type;
+  function bind(key, cmd) {
+    if (suppressKeys) {
+      let mapped = suppressKeys[key];
+      if (mapped === false) {
+        return;
+      }
+      if (mapped) {
+        key = mapped;
+      }
+    }
+    keys[key] = cmd;
+  }
+
+  bind("Mod-z", undo);
+  bind("Shift-Mod-z", redo);
+  bind("Backspace", undoInputRule);
+  if (!isMac) {
+    bind("Mod-y", redo);
+  }
+
+  bind("Alt-ArrowUp", joinUp);
+  bind("Alt-ArrowDown", joinDown);
+  bind("Mod-BracketLeft", lift);
+  bind("Escape", selectParentNode);
+
+  if ((type = schema.marks.code)) {
+    bind("Mod-`", toggleMark(type));
+  }
+
+  if ((type = schema.nodes.blockquote)) {
+    bind("Ctrl->", wrapIn(type));
+  }
+  if ((type = schema.nodes.hard_break)) {
+    let br = type,
+      cmd = chainCommands(exitCode, (state, dispatch) => {
+        if (dispatch) {
+          dispatch(state.tr.replaceSelectionWith(br.create()).scrollIntoView());
+        }
+        return true;
+      });
+    bind("Mod-Enter", cmd);
+    bind("Shift-Enter", cmd);
+    if (isMac) {
+      bind("Ctrl-Enter", cmd);
+    }
+  }
+  if ((type = schema.nodes.list_item)) {
+    bind("Enter", splitListItem(type));
+    bind("Mod-[", liftListItem(type));
+    bind("Mod-]", sinkListItem(type));
+  }
+  if ((type = schema.nodes.paragraph)) {
+    bind("Shift-Ctrl-0", setBlockType(type));
+  }
+  if ((type = schema.nodes.code_block)) {
+    bind("Shift-Ctrl-\\", setBlockType(type));
+  }
+  if ((type = schema.nodes.heading)) {
+    for (let i = 1; i <= 6; i++) {
+      bind("Shift-Ctrl-" + i, setBlockType(type, { level: i }));
+    }
+  }
+  if ((type = schema.nodes.horizontal_rule)) {
+    bind("Mod-_", (state, dispatch) => {
+      dispatch?.(state.tr.replaceSelectionWith(type.create()).scrollIntoView());
+      return true;
+    });
+  }
+
+  return keys;
+}
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/plugins/placeholder.js b/app/assets/javascripts/discourse/app/static/prosemirror/plugins/placeholder.js
new file mode 100644
index 00000000000..86bdc1469fd
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/plugins/placeholder.js
@@ -0,0 +1,27 @@
+import { Plugin } from "prosemirror-state";
+import { Decoration, DecorationSet } from "prosemirror-view";
+
+const isEmptyParagraph = (node) => {
+  return node.type.name === "paragraph" && node.nodeSize === 2;
+};
+
+export default (placeholder) => {
+  return new Plugin({
+    props: {
+      decorations(state) {
+        const { $from } = state.selection;
+
+        if (
+          state.doc.childCount === 1 &&
+          state.doc.firstChild === $from.parent &&
+          isEmptyParagraph($from.parent)
+        ) {
+          const decoration = Decoration.node($from.before(), $from.after(), {
+            "data-placeholder": placeholder,
+          });
+          return DecorationSet.create(state.doc, [decoration]);
+        }
+      },
+    },
+  });
+};
diff --git a/app/assets/javascripts/discourse/package.json b/app/assets/javascripts/discourse/package.json
index a9de2e43f5b..62dadac07ae 100644
--- a/app/assets/javascripts/discourse/package.json
+++ b/app/assets/javascripts/discourse/package.json
@@ -31,8 +31,21 @@
     "highlight.js": "11.11.1",
     "immer": "^10.1.1",
     "jspreadsheet-ce": "^4.15.0",
+    "lowlight": "^3.2.0",
     "morphlex": "^0.0.16",
-    "pretty-text": "workspace:1.0.0"
+    "pretty-text": "workspace:1.0.0",
+    "prosemirror-commands": "^1.6.0",
+    "prosemirror-dropcursor": "^1.8.1",
+    "prosemirror-gapcursor": "^1.3.2",
+    "prosemirror-highlight": "^0.11.0",
+    "prosemirror-history": "^1.4.1",
+    "prosemirror-inputrules": "^1.4.0",
+    "prosemirror-keymap": "^1.2.2",
+    "prosemirror-markdown": "^1.13.1",
+    "prosemirror-model": "^1.23.0",
+    "prosemirror-schema-list": "^1.4.1",
+    "prosemirror-state": "^1.4.3",
+    "prosemirror-view": "^1.34.3"
   },
   "devDependencies": {
     "@babel/core": "^7.26.0",
diff --git a/app/assets/stylesheets/common.scss b/app/assets/stylesheets/common.scss
index 57e76d81116..1ae638a0fac 100644
--- a/app/assets/stylesheets/common.scss
+++ b/app/assets/stylesheets/common.scss
@@ -18,6 +18,7 @@
 @import "common/topic-timeline";
 @import "common/loading-slider";
 @import "common/float-kit/_index";
+@import "common/rich-editor";
 @import "common/login/_index";
 @import "common/table-builder/_index";
 @import "common/post-action-feedback";
diff --git a/app/assets/stylesheets/common/components/_index.scss b/app/assets/stylesheets/common/components/_index.scss
index d8eb9592fb6..691c0d78f8b 100644
--- a/app/assets/stylesheets/common/components/_index.scss
+++ b/app/assets/stylesheets/common/components/_index.scss
@@ -12,6 +12,7 @@
 @import "char-counter";
 @import "conditional-loading-section";
 @import "calendar-date-time-input";
+@import "composer-toggle-switch";
 @import "convert-to-public-topic-modal";
 @import "d-lightbox";
 @import "d-toggle-switch";
diff --git a/app/assets/stylesheets/common/components/composer-toggle-switch.scss b/app/assets/stylesheets/common/components/composer-toggle-switch.scss
new file mode 100644
index 00000000000..b5100d805f3
--- /dev/null
+++ b/app/assets/stylesheets/common/components/composer-toggle-switch.scss
@@ -0,0 +1,146 @@
+.composer-toggle-switch {
+  $root: &;
+
+  --toggle-switch-width: 48px;
+  --toggle-switch-height: 24px;
+
+  grid-column: span 2;
+  justify-content: center;
+
+  &:focus {
+    &__checkbox-slider {
+      outline: 2px solid var(--tertiary);
+      outline-offset: 2px;
+    }
+  }
+
+  &:hover {
+    &__checkbox-slider {
+      background-color: var(--primary-high);
+    }
+
+    &__checkbox[aria-checked="true"]:not([disabled])
+      + #{$root}__checkbox-slider {
+      background-color: var(--tertiary-hover);
+    }
+  }
+
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+
+  &__label {
+    position: relative;
+    display: inline-block;
+    cursor: pointer;
+    margin: 0;
+  }
+
+  &__checkbox {
+    position: absolute;
+    border: 0;
+    padding: 0;
+    background: transparent;
+
+    &:focus {
+      + #{$root}__checkbox-slider {
+        outline: 2px solid var(--tertiary);
+        outline-offset: 2px;
+      }
+
+      // Outline should show only when tabbing, not clicking
+      &:not(:focus-visible) {
+        + #{$root}__checkbox-slider {
+          outline: none;
+        }
+      }
+    }
+  }
+
+  &__checkbox[aria-checked="true"] + &__checkbox-slider::before {
+    left: calc(var(--toggle-switch-width) - var(--toggle-switch-height));
+  }
+
+  &__checkbox[disabled] + &__checkbox-slider {
+    opacity: 0.5;
+    cursor: not-allowed;
+
+    &::before {
+      cursor: not-allowed;
+    }
+  }
+
+  &__checkbox-slider {
+    display: inline-block;
+    cursor: pointer;
+    background: var(--primary-low-mid);
+    width: var(--toggle-switch-width);
+    height: var(--toggle-switch-height);
+    position: relative;
+    vertical-align: middle;
+    transition: background 0.25s;
+  }
+
+  &__left-icon {
+    opacity: 0;
+    transition: opacity 0.25s;
+
+    @media (prefers-reduced-motion: reduce) {
+      transition-duration: 0ms;
+    }
+
+    &.--active {
+      opacity: 1;
+    }
+
+    & .d-icon {
+      font-size: var(--font-down-1);
+      color: var(--primary);
+      left: 5px;
+      top: 6px;
+      position: absolute;
+    }
+  }
+
+  &__right-icon {
+    opacity: 0;
+    transition: opacity 0.25s;
+
+    @media (prefers-reduced-motion: reduce) {
+      transition-duration: 0ms;
+    }
+
+    & .d-icon {
+      font-size: var(--font-down-1);
+      color: var(--primary);
+      right: 5px;
+      top: 6px;
+      position: absolute;
+    }
+
+    &.--active {
+      opacity: 1;
+    }
+  }
+
+  &__checkbox-slider::before,
+  &__checkbox-slider::after {
+    content: "";
+    display: block;
+    position: absolute;
+    cursor: pointer;
+  }
+
+  &__checkbox-slider::before {
+    background-color: var(--tertiary-low);
+    width: var(--toggle-switch-height);
+    height: var(--toggle-switch-height);
+    top: 0;
+    left: 0;
+    transition: left 0.25s;
+
+    @media (prefers-reduced-motion: reduce) {
+      transition-duration: 0ms;
+    }
+  }
+}
diff --git a/app/assets/stylesheets/common/rich-editor/_index.scss b/app/assets/stylesheets/common/rich-editor/_index.scss
new file mode 100644
index 00000000000..31b532f02a9
--- /dev/null
+++ b/app/assets/stylesheets/common/rich-editor/_index.scss
@@ -0,0 +1 @@
+@import "rich-editor";
diff --git a/app/assets/stylesheets/common/rich-editor/rich-editor.scss b/app/assets/stylesheets/common/rich-editor/rich-editor.scss
new file mode 100644
index 00000000000..d025c7af37b
--- /dev/null
+++ b/app/assets/stylesheets/common/rich-editor/rich-editor.scss
@@ -0,0 +1,198 @@
+.d-editor__container {
+  margin: 0;
+  overscroll-behavior: contain;
+  overflow-anchor: none;
+  flex-direction: column;
+  overflow-y: auto;
+  overflow-x: hidden;
+  display: flex;
+  height: 100%;
+}
+
+.d-editor__editable {
+  outline: 0;
+  padding: 0 0.625rem;
+
+  h1,
+  h2,
+  h3,
+  h4,
+  h5,
+  h6 {
+    margin: 30px 0 10px;
+    &:first-child {
+      margin-top: 10px;
+    }
+  }
+
+  h1 {
+    font-size: var(--font-up-3-rem);
+  }
+
+  h2 {
+    font-size: var(--font-up-2-rem);
+  }
+
+  h3 {
+    font-size: var(--font-up-1-rem);
+  }
+
+  img {
+    display: inline-block;
+    margin: 0 auto;
+    max-width: 100%;
+
+    &[data-placeholder="true"] {
+      animation: placeholder 1.5s infinite;
+
+      @keyframes placeholder {
+        0% {
+          opacity: 0.6;
+        }
+        50% {
+          opacity: 0.4;
+        }
+        100% {
+          opacity: 0.6;
+        }
+      }
+    }
+  }
+
+  ul,
+  ol {
+    padding-left: 1.25em;
+
+    &[data-tight="true"] > li > p {
+      margin-top: 0;
+      margin-bottom: 0;
+    }
+  }
+
+  p {
+    line-height: 1.5;
+
+    &:first-child {
+      margin-top: 0.59rem;
+    }
+  }
+
+  p[data-placeholder]::before {
+    pointer-events: none;
+    position: absolute;
+    padding-top: 2px;
+    padding-right: 0.5rem;
+    content: attr(data-placeholder);
+    color: var(--primary-400);
+    line-height: 1.1;
+  }
+
+  del {
+    background-color: var(--danger-low);
+  }
+
+  ins {
+    background-color: var(--success-low);
+  }
+
+  mark {
+    background-color: var(--highlight);
+  }
+
+  td {
+    padding: 3px 3px 3px 0.5em;
+  }
+
+  th {
+    padding-bottom: 2px;
+    font-weight: bold;
+    color: var(--primary);
+  }
+
+  kbd {
+    // I believe this shouldn't be `inline-flex` in posts either (test with emojis before/after text to see why),
+    // but overriding just for the editor for now
+    display: inline;
+    padding-top: 0.2rem;
+  }
+}
+
+.d-editor__code-lang-select {
+  position: absolute;
+  right: 0.25rem;
+  top: -0.6rem;
+  border: 1px solid var(--primary-low);
+  border-radius: var(--border-radius);
+  background-color: var(--primary-very-low);
+  color: var(--primary-medium);
+  font-size: var(--font-down-1-rem);
+}
+
+/*
+ Everything below was copied from prosemirror-view/style/prosemirror.css
+ */
+
+.ProseMirror {
+  position: relative;
+}
+
+.ProseMirror {
+  word-wrap: break-word;
+  white-space: pre-wrap;
+  white-space: break-spaces;
+  -webkit-font-variant-ligatures: none;
+  font-variant-ligatures: none;
+  font-feature-settings: "liga" 0; /* the above doesn't seem to work in Edge */
+}
+
+.ProseMirror pre {
+  white-space: pre-wrap;
+}
+
+.ProseMirror li {
+  position: relative;
+}
+
+.ProseMirror-hideselection *::selection {
+  background: transparent;
+}
+.ProseMirror-hideselection *::-moz-selection {
+  background: transparent;
+}
+.ProseMirror-hideselection {
+  caret-color: transparent;
+}
+
+/* See https://github.com/ProseMirror/prosemirror/issues/1421#issuecomment-1759320191 */
+.ProseMirror [draggable][contenteditable="false"] {
+  user-select: text;
+}
+
+.ProseMirror-selectednode {
+  outline: 2px solid #8cf;
+}
+
+/* Make sure li selections wrap around markers */
+
+li.ProseMirror-selectednode {
+  outline: none;
+}
+
+li.ProseMirror-selectednode:after {
+  content: "";
+  position: absolute;
+  left: -32px;
+  right: -2px;
+  top: -2px;
+  bottom: -2px;
+  border: 2px solid #8cf;
+  pointer-events: none;
+}
+
+/* Protect against generic img rules */
+
+img.ProseMirror-separator {
+  display: inline !important;
+  border: none !important;
+  margin: 0 !important;
+}
diff --git a/app/assets/stylesheets/mobile/compose.scss b/app/assets/stylesheets/mobile/compose.scss
index dcb7b0228fb..8e329483221 100644
--- a/app/assets/stylesheets/mobile/compose.scss
+++ b/app/assets/stylesheets/mobile/compose.scss
@@ -13,6 +13,7 @@
     padding: 6px;
     padding-bottom: unquote("max(env(safe-area-inset-bottom), 6px)");
     flex-grow: 1;
+    min-height: 0;
   }
 
   &.open {
diff --git a/config/site_settings.yml b/config/site_settings.yml
index 6f439651416..3482ed64e9c 100644
--- a/config/site_settings.yml
+++ b/config/site_settings.yml
@@ -3368,3 +3368,7 @@ experimental:
     default: ""
     type: group_list
     list_type: compact
+  experimental_rich_editor:
+    client: true
+    default: false
+    hidden: true
diff --git a/docs/CHANGELOG-JAVASCRIPT-PLUGIN-API.md b/docs/CHANGELOG-JAVASCRIPT-PLUGIN-API.md
index 623745a74e0..311429f9a4d 100644
--- a/docs/CHANGELOG-JAVASCRIPT-PLUGIN-API.md
+++ b/docs/CHANGELOG-JAVASCRIPT-PLUGIN-API.md
@@ -7,6 +7,10 @@ in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.40.0] - 2024-12-16
+
+- Added `registerRichEditorExtension` which allows plugins/TCs to register an extension for the rich text editor.
+
 ## [1.39.2] - 2024-12-19
 
 - Removed the deprecation of `includePostAttributes` for now.
diff --git a/lib/svg_sprite.rb b/lib/svg_sprite.rb
index 3c26ba54cb5..fa8f271e304 100644
--- a/lib/svg_sprite.rb
+++ b/lib/svg_sprite.rb
@@ -4,6 +4,7 @@ module SvgSprite
   SVG_ICONS =
     Set.new(
       %w[
+        a
         address-book
         align-left
         anchor
@@ -105,6 +106,7 @@ module SvgSprite
         fab-instagram
         fab-linkedin-in
         fab-linux
+        fab-markdown
         fab-threads
         fab-threads-square
         fab-twitter
diff --git a/plugins/chat/assets/javascripts/discourse/initializers/chat-keyboard-shortcuts.js b/plugins/chat/assets/javascripts/discourse/initializers/chat-keyboard-shortcuts.js
index 6b5bda472ce..427304c2d2d 100644
--- a/plugins/chat/assets/javascripts/discourse/initializers/chat-keyboard-shortcuts.js
+++ b/plugins/chat/assets/javascripts/discourse/initializers/chat-keyboard-shortcuts.js
@@ -58,10 +58,10 @@ export default {
       const inputs = ["input", "textarea", "select", "button"];
       const elementTagName = el?.tagName.toLowerCase();
 
-      if (inputs.includes(elementTagName)) {
-        return false;
-      }
-      return true;
+      return (
+        inputs.includes(elementTagName) ||
+        !!el?.closest('[contenteditable="true"]')
+      );
     };
     const modifyComposerSelection = (event, type) => {
       if (!isChatComposer(event.target)) {
@@ -87,7 +87,7 @@ export default {
     };
 
     const openChatDrawer = (event) => {
-      if (!isInputSelection(event.target)) {
+      if (isInputSelection(event.target)) {
         return;
       }
       event.preventDefault();
diff --git a/plugins/checklist/assets/javascripts/discourse/initializers/checklist.js b/plugins/checklist/assets/javascripts/discourse/initializers/checklist.js
index 89f6d9ece90..8524ff52c9b 100644
--- a/plugins/checklist/assets/javascripts/discourse/initializers/checklist.js
+++ b/plugins/checklist/assets/javascripts/discourse/initializers/checklist.js
@@ -3,12 +3,14 @@ import { popupAjaxError } from "discourse/lib/ajax-error";
 import { withPluginApi } from "discourse/lib/plugin-api";
 import { iconHTML } from "discourse-common/lib/icon-library";
 import { i18n } from "discourse-i18n";
+import richEditorExtension from "../../lib/rich-editor-extension";
 
 function initializePlugin(api) {
   const siteSettings = api.container.lookup("service:site-settings");
 
   if (siteSettings.checklist_enabled) {
     api.decorateCookedElement(checklistSyntax);
+    api.registerRichEditorExtension(richEditorExtension);
   }
 }
 
diff --git a/plugins/checklist/assets/javascripts/lib/rich-editor-extension.js b/plugins/checklist/assets/javascripts/lib/rich-editor-extension.js
new file mode 100644
index 00000000000..f239847648e
--- /dev/null
+++ b/plugins/checklist/assets/javascripts/lib/rich-editor-extension.js
@@ -0,0 +1,67 @@
+export default {
+  // TODO(renato): make the checkbox clickable
+  // TODO(renato): auto-continue checkbox list on ENTER
+  // TODO(renato): apply .has-checkbox style to the <li> to avoid :has
+  nodeSpec: {
+    check: {
+      attrs: { checked: { default: false } },
+      inline: true,
+      group: "inline",
+      draggable: true,
+      selectable: false,
+      toDOM(node) {
+        return [
+          "span",
+          {
+            class: node.attrs.checked
+              ? "chcklst-box checked fa fa-square-check-o fa-fw"
+              : "chcklst-box fa fa-square-o fa-fw",
+          },
+        ];
+      },
+      parseDOM: [
+        {
+          tag: "span.chcklst-box",
+          getAttrs: (dom) => {
+            return { checked: hasCheckedClass(dom.className) };
+          },
+        },
+      ],
+    },
+  },
+
+  inputRules: [
+    {
+      match: /(?<=^|\s)\[(x? ?)]$/,
+      handler: (state, match, start, end) =>
+        state.tr.replaceWith(
+          start,
+          end,
+          state.schema.nodes.check.create({ checked: match[1] === "x" })
+        ),
+      options: { undoable: false },
+    },
+  ],
+
+  parse: {
+    check_open: {
+      node: "check",
+      getAttrs: (token) => ({
+        checked: hasCheckedClass(token.attrGet("class")),
+      }),
+    },
+    check_close: { noCloseToken: true, ignore: true },
+  },
+
+  serializeNode: {
+    check: (state, node) => {
+      state.write(node.attrs.checked ? "[x]" : "[ ]");
+    },
+  },
+};
+
+const CHECKED_REGEX = /\bchecked\b/;
+
+function hasCheckedClass(className) {
+  return CHECKED_REGEX.test(className);
+}
diff --git a/plugins/checklist/assets/stylesheets/checklist.scss b/plugins/checklist/assets/stylesheets/checklist.scss
index b4b9752d87e..8ecde9a75b0 100644
--- a/plugins/checklist/assets/stylesheets/checklist.scss
+++ b/plugins/checklist/assets/stylesheets/checklist.scss
@@ -68,6 +68,17 @@ ul li.has-checkbox {
   }
 }
 
+.d-editor__editable {
+  // TODO(renato): this is temporary, we should use `has-checkbox` instead
+  li:has(p:first-of-type > span.chcklst-box) {
+    list-style-type: none;
+
+    .chcklst-box:first-of-type {
+      margin-left: -1.33em;
+    }
+  }
+}
+
 .fa-spin {
   display: inline-flex;
   vertical-align: text-bottom;
diff --git a/plugins/discourse-details/assets/javascripts/initializers/apply-details.js b/plugins/discourse-details/assets/javascripts/initializers/apply-details.js
index bd7a2d505d4..fd2ef6da623 100644
--- a/plugins/discourse-details/assets/javascripts/initializers/apply-details.js
+++ b/plugins/discourse-details/assets/javascripts/initializers/apply-details.js
@@ -1,6 +1,7 @@
 import $ from "jquery";
 import { withPluginApi } from "discourse/lib/plugin-api";
 import { i18n } from "discourse-i18n";
+import richEditorExtension from "../lib/rich-editor-extension";
 
 function initializeDetails(api) {
   api.decorateCooked(($elem) => $("details", $elem), {
@@ -19,6 +20,8 @@ function initializeDetails(api) {
     icon: "caret-right",
     label: "details.title",
   });
+
+  api.registerRichEditorExtension(richEditorExtension);
 }
 
 export default {
diff --git a/plugins/discourse-details/assets/javascripts/lib/rich-editor-extension.js b/plugins/discourse-details/assets/javascripts/lib/rich-editor-extension.js
new file mode 100644
index 00000000000..e89bc06eb23
--- /dev/null
+++ b/plugins/discourse-details/assets/javascripts/lib/rich-editor-extension.js
@@ -0,0 +1,41 @@
+export default {
+  nodeSpec: {
+    details: {
+      content: "summary block+",
+      group: "block",
+      defining: true,
+      parseDOM: [{ tag: "details" }],
+      toDOM: () => ["details", { open: true }, 0],
+    },
+    summary: {
+      content: "inline*",
+      group: "block",
+      parseDOM: [{ tag: "summary" }],
+      toDOM: () => ["summary", 0],
+    },
+  },
+  parse: {
+    bbcode(state, token) {
+      if (token.tag === "details") {
+        state.openNode(state.schema.nodes.details);
+        return true;
+      }
+
+      if (token.tag === "summary") {
+        state.openNode(state.schema.nodes.summary);
+        return true;
+      }
+    },
+  },
+  serializeNode: {
+    details(state, node) {
+      state.renderContent(node);
+      state.write("[/details]\n");
+    },
+    summary(state, node) {
+      state.write("[details=");
+      state.renderContent(node);
+      state.write("]\n");
+    },
+  },
+};
diff --git a/plugins/discourse-details/assets/stylesheets/details.scss b/plugins/discourse-details/assets/stylesheets/details.scss
index 741464acc55..e657869c115 100644
--- a/plugins/discourse-details/assets/stylesheets/details.scss
+++ b/plugins/discourse-details/assets/stylesheets/details.scss
@@ -3,7 +3,8 @@ details {
 
   .topic-body .cooked &,
   .d-editor-preview,
-  &.details__boxed {
+  &.details__boxed,
+  .d-editor__editable & {
     background-color: var(--primary-very-low);
     padding: 0.25rem 0.75rem;
     margin-bottom: 0.5rem;
diff --git a/plugins/discourse-local-dates/assets/javascripts/initializers/discourse-local-dates.js b/plugins/discourse-local-dates/assets/javascripts/initializers/discourse-local-dates.js
index 41fafecf706..3ec0c26a84b 100644
--- a/plugins/discourse-local-dates/assets/javascripts/initializers/discourse-local-dates.js
+++ b/plugins/discourse-local-dates/assets/javascripts/initializers/discourse-local-dates.js
@@ -13,6 +13,7 @@ import { i18n } from "discourse-i18n";
 import generateDateMarkup from "discourse/plugins/discourse-local-dates/lib/local-date-markup-generator";
 import LocalDatesCreateModal from "../discourse/components/modal/local-dates-create";
 import LocalDateBuilder from "../lib/local-date-builder";
+import richEditorExtension from "../lib/rich-editor-extension";
 
 // Import applyLocalDates from discourse/lib/local-dates instead
 export function applyLocalDates(dates, siteSettings) {
@@ -236,6 +237,8 @@ function initializeDiscourseLocalDates(api) {
       return "";
     }
   });
+
+  api.registerRichEditorExtension(richEditorExtension);
 }
 
 function buildHtmlPreview(element, siteSettings) {
diff --git a/plugins/discourse-local-dates/assets/javascripts/lib/rich-editor-extension.js b/plugins/discourse-local-dates/assets/javascripts/lib/rich-editor-extension.js
new file mode 100644
index 00000000000..4dacfd405f6
--- /dev/null
+++ b/plugins/discourse-local-dates/assets/javascripts/lib/rich-editor-extension.js
@@ -0,0 +1,132 @@
+export default {
+  // TODO the rendered date needs to be localized to better match the cooked content
+  nodeSpec: {
+    local_date: {
+      attrs: { date: {}, time: {}, timezone: { default: null } },
+      content: "text*",
+      group: "inline",
+      atom: true,
+      inline: true,
+      parseDOM: [
+        {
+          tag: "span.discourse-local-date[data-date]",
+          getAttrs: (dom) => {
+            return {
+              date: dom.getAttribute("data-date"),
+              time: dom.getAttribute("data-time"),
+              timezone: dom.getAttribute("data-timezone"),
+            };
+          },
+        },
+      ],
+      toDOM: (node) => {
+        const optionalTime = node.attrs.time ? ` ${node.attrs.time}` : "";
+        return [
+          "span",
+          {
+            class: "discourse-local-date cooked-date",
+            "data-date": node.attrs.date,
+            "data-time": node.attrs.time,
+            "data-timezone": node.attrs.timezone,
+          },
+          `${node.attrs.date}${optionalTime}`,
+        ];
+      },
+    },
+    local_date_range: {
+      attrs: { from: {}, to: { default: null }, timezone: { default: null } },
+      content: "text*",
+      group: "inline",
+      atom: true,
+      inline: true,
+      parseDOM: [
+        {
+          tag: "span.discourse-local-date[data-from]",
+          getAttrs: (dom) => {
+            return {
+              from: dom.getAttribute("data-from"),
+              to: dom.getAttribute("data-to"),
+              timezone: dom.getAttribute("data-timezone"),
+            };
+          },
+        },
+      ],
+      toDOM: (node) => {
+        return [
+          "span",
+          { class: "discourse-local-date-wrapper" },
+          [
+            "span",
+            {
+              class: "discourse-local-date cooked-date",
+              "data-range": "from",
+              "data-date": node.attrs.from,
+              "data-timezone": node.attrs.timezone,
+            },
+            `${node.attrs.from}`,
+          ],
+          " → ",
+          [
+            "span",
+            {
+              class: "discourse-local-date cooked-date",
+              "data-range": "to",
+              "data-date": node.attrs.to,
+              "data-timezone": node.attrs.timezone,
+            },
+            `${node.attrs.to}`,
+          ],
+        ];
+      },
+    },
+  },
+  parse: {
+    span: (state, token) => {
+      if (token.attrGet("class") !== "discourse-local-date") {
+        return;
+      }
+
+      if (token.attrGet("data-range") === "from") {
+        state.openNode(state.schema.nodes.local_date_range, {
+          from: token.attrGet("data-date"),
+          to: token.attrGet("data-date"),
+          timezone: token.attrGet("data-timezone"),
+        });
+        return;
+      }
+
+      if (token.attrGet("data-range") === "to") {
+        // we're not supposed to mutate attrs, but we're still building the doc
+        state.top().attrs.to = token.attrGet("data-date");
+        return true;
+      }
+
+      state.openNode(state.schema.nodes.local_date, {
+        date: token.attrGet("data-date"),
+        time: token.attrGet("data-time"),
+        timezone: token.attrGet("data-timezone"),
+      });
+      return true;
+    },
+  },
+  serializeNode: {
+    local_date: (state, node) => {
+      const optionalTime = node.attrs.time ? ` time=${node.attrs.time}` : "";
+      const optionalTimezone = node.attrs.timezone
+        ? ` timezone="${node.attrs.timezone}"`
+        : "";
+
+      state.write(
+        `[date=${node.attrs.date}${optionalTime}${optionalTimezone}]`
+      );
+    },
+    local_date_range: (state, node) => {
+      const optionalTimezone = node.attrs.timezone
+        ? ` timezone="${node.attrs.timezone}"`
+        : "";
+      state.write(
+        `[date-range from=${node.attrs.from} to=${node.attrs.to}${optionalTimezone}]`
+      );
+    },
+  },
+};