diff --git a/CONTENT_BRIDGE.md b/CONTENT_BRIDGE.md
index e1979d8..dadc0ab 100644
--- a/CONTENT_BRIDGE.md
+++ b/CONTENT_BRIDGE.md
@@ -114,6 +114,129 @@ Quarto margin notes such as `[text]{.aside}` were converted to:
 > **Aside:** text
 ```
 
+## Semantic Blocks
+
+Use Pandoc-style fenced attributes for blocks that need to render differently
+in HTML and PDF. This is the preferred form because it works cleanly with both
+Astro and Pandoc/LuaLaTeX.
+
+### Interactive Blocks
+
+An interactive block reserves a place in the post for a React component and
+also supplies fallback text for PDF or non-JavaScript rendering:
+
+````markdown
+```{.interactive #int:tape-layout caption="Tape layout explorer"}
+Drag files along a tape and compare the access cost of each arrangement.
+```
+````
+
+The id after `#` is the semantic label. For interactives, use the `int:` prefix.
+The component id is inferred by removing that prefix, so the example above
+mounts this component when it exists:
+
+```text
+sites/<blog>/src/interactives/tape-layout/index.tsx
+```
+
+The component receives:
+
+```ts
+{
+  id: "tape-layout",
+  label: "int:tape-layout",
+  caption: "Tape layout explorer",
+  description: "Drag files along a tape...",
+  fallback: "Drag files along a tape...",
+  attrs: { caption: "Tape layout explorer" }
+}
+```
+
+If the component is not present, Astro renders the fallback text in the
+interactive frame. For a different PDF fallback, add `pdf="..."`:
+
+````markdown
+```{.interactive #int:tape-layout caption="Tape layout explorer" pdf="The HTML version contains an interactive tape layout explorer."}
+Implementation notes for the interactive can go here.
+```
+````
+
+Astro also accepts the shorter Obsidian-friendly form:
+
+````markdown
+```interactive id="tape-layout" caption="Tape layout explorer"
+Drag files along a tape and compare the access cost.
+```
+````
+
+Use the Pandoc-style form for posts that should export to PDF.
+
+### LaTeX-Style Environments
+
+Use `.env` plus the environment class and a label:
+
+````markdown
+```{.env .theorem #thm:hall title="Hall's theorem" html="callout"}
+Every bipartite graph satisfying Hall's condition has a matching that covers
+the left side.
+```
+````
+
+Supported environment types are:
+
+```text
+theorem, lemma, proposition, corollary, definition, example, remark, proof
+```
+
+In Astro, `html="callout"` renders the block like a callout. `html="plain"`
+renders it as a quieter left-rule block. If `html` is omitted, theorem-like
+blocks default to `callout`, and `proof` defaults to `plain`.
+
+In PDF, the same block becomes a real LuaLaTeX environment:
+
+```tex
+\begin{theorem}[Hall's theorem]
+\label{thm:hall}
+...
+\end{theorem}
+```
+
+Astro also accepts shorter forms when PDF export is not needed:
+
+````markdown
+```theorem id="thm:hall" title="Hall's theorem"
+Every bipartite graph satisfying Hall's condition has a matching...
+```
+````
+
+### Linking To Semantic Blocks
+
+Use ordinary Markdown links to semantic ids:
+
+```markdown
+The proof of [Hall's theorem](#thm:hall) is constructive.
+See the [tape explorer](#int:tape-layout) for an interactive version.
+```
+
+Astro renders these as normal HTML links. The PDF pipeline converts internal
+links whose target starts with `#` into `\cref{...}`, so the first link above
+becomes `\cref{thm:hall}`.
+
+Use these label prefixes consistently:
+
+```text
+thm: theorem
+lem: lemma
+prop: proposition
+cor: corollary
+def: definition
+ex: example
+rem: remark
+prf: proof
+int: interactive
+fig: figure
+```
+
 ## Import Rules
 
 The import script is:
@@ -168,3 +291,23 @@ Publish does three things:
 1. Sync vault content into the local repo.
 2. Run the configured Astro build command.
 3. Commit and push to Forgejo, where Dokploy picks up the change.
+
+## PDF Export
+
+PDF export uses Pandoc plus LuaLaTeX:
+
+```bash
+npm run pdf:post -- sites/research/src/content/research/example/index.md --out /tmp/example.pdf
+```
+
+The command runs:
+
+- `scripts/pandoc-filters/semantic-blocks.lua` to convert interactive and
+  environment fences.
+- `scripts/pandoc-templates/semantic-preamble.tex` to load `amsthm`,
+  `cleveref`, and the shared theorem definitions.
+
+The PDF route is intentionally separate from Astro. Astro owns HTML rendering;
+Pandoc owns PDF rendering. The Markdown conventions above are the shared
+contract between both outputs and can be reused for future site families such
+as `neeldhara.courses` and `books.neeldhara.com`.
diff --git a/package.json b/package.json
index 965a6aa..b2f8745 100644
--- a/package.json
+++ b/package.json
@@ -15,6 +15,7 @@
     "build": "node scripts/build-site-packages.mjs",
     "build:sites": "node scripts/build-site-packages.mjs",
     "build:legacy": "node scripts/build-all-sites.mjs",
+    "pdf:post": "node scripts/export-pdf.mjs",
     "preview": "npm run preview --prefix sites/research",
     "astro": "astro",
     "format": "prettier -w ."
diff --git a/scripts/export-pdf.mjs b/scripts/export-pdf.mjs
new file mode 100644
index 0000000..218dcb5
--- /dev/null
+++ b/scripts/export-pdf.mjs
@@ -0,0 +1,64 @@
+import { existsSync, mkdirSync } from "node:fs";
+import path from "node:path";
+import { spawnSync } from "node:child_process";
+import { fileURLToPath } from "node:url";
+
+const repoRoot = path.resolve(fileURLToPath(new URL("..", import.meta.url)));
+const filterPath = path.join(repoRoot, "scripts", "pandoc-filters", "semantic-blocks.lua");
+const preamblePath = path.join(repoRoot, "scripts", "pandoc-templates", "semantic-preamble.tex");
+
+function usage() {
+  console.error("Usage: node scripts/export-pdf.mjs <post.md> [--out output.pdf]");
+}
+
+function parseArgs(argv) {
+  const args = [...argv];
+  const input = args.find((arg) => !arg.startsWith("--"));
+  const outIndex = args.indexOf("--out");
+  const output = outIndex >= 0 ? args[outIndex + 1] : "";
+  return { input, output };
+}
+
+const { input, output } = parseArgs(process.argv.slice(2));
+
+if (!input) {
+  usage();
+  process.exit(2);
+}
+
+const inputPath = path.resolve(input);
+if (!existsSync(inputPath)) {
+  console.error(`Input file not found: ${inputPath}`);
+  process.exit(2);
+}
+
+const outputPath = path.resolve(
+  output || path.join(path.dirname(inputPath), `${path.basename(inputPath, path.extname(inputPath))}.pdf`),
+);
+mkdirSync(path.dirname(outputPath), { recursive: true });
+
+const pandocArgs = [
+  inputPath,
+  "--from",
+  "markdown+fenced_code_attributes+tex_math_dollars+tex_math_single_backslash+footnotes+raw_html",
+  "--pdf-engine=lualatex",
+  "--lua-filter",
+  filterPath,
+  "--include-in-header",
+  preamblePath,
+  "--output",
+  outputPath,
+];
+
+const result = spawnSync("pandoc", pandocArgs, { stdio: "inherit" });
+
+if (result.error?.code === "ENOENT") {
+  console.error("pandoc is not installed or is not on PATH. Install pandoc and a LuaLaTeX distribution first.");
+  process.exit(127);
+}
+
+if (result.status !== 0) {
+  process.exit(result.status ?? 1);
+}
+
+console.log(`Wrote ${outputPath}`);
diff --git a/scripts/pandoc-filters/semantic-blocks.lua b/scripts/pandoc-filters/semantic-blocks.lua
new file mode 100644
index 0000000..893a018
--- /dev/null
+++ b/scripts/pandoc-filters/semantic-blocks.lua
@@ -0,0 +1,131 @@
+local env_types = {
+  theorem = true,
+  lemma = true,
+  proposition = true,
+  corollary = true,
+  definition = true,
+  example = true,
+  remark = true,
+  proof = true,
+}
+
+local function has_class(el, class_name)
+  for _, value in ipairs(el.classes) do
+    if value == class_name then
+      return true
+    end
+  end
+  return false
+end
+
+local function first_env_class(el)
+  for _, value in ipairs(el.classes) do
+    if env_types[value] then
+      return value
+    end
+  end
+  return nil
+end
+
+local function latex_escape(value)
+  value = tostring(value or "")
+  value = value:gsub("\\", "\\textbackslash{}")
+  value = value:gsub("([{}%%$&#_])", "\\%1")
+  value = value:gsub("%^", "\\textasciicircum{}")
+  value = value:gsub("~", "\\textasciitilde{}")
+  return value
+end
+
+local function internal_link_to_cref(el)
+  if FORMAT:match("latex") and el.target:sub(1, 1) == "#" then
+    local label = el.target:sub(2)
+    if label ~= "" then
+      return pandoc.RawInline("latex", "\\cref{" .. label .. "}")
+    end
+  end
+  return nil
+end
+
+local function markdown_to_latex(markdown)
+  local doc = pandoc.read(
+    markdown or "",
+    "markdown+fenced_code_attributes+tex_math_dollars+tex_math_single_backslash+footnotes+raw_html"
+  )
+  doc = doc:walk({ Link = internal_link_to_cref })
+  return pandoc.write(doc, "latex")
+end
+
+local function label_line(label)
+  if label and label ~= "" then
+    return "\\label{" .. label .. "}\n"
+  end
+  return ""
+end
+
+local function interactive_to_latex(el)
+  local label = el.identifier
+  local caption = el.attributes.caption or el.attributes.title or ""
+  local fallback = el.attributes.pdf or el.attributes.fallback or el.text
+  local fallback_latex = markdown_to_latex(fallback)
+  local caption_line = ""
+
+  if caption ~= "" then
+    caption_line = "\\caption{" .. latex_escape(caption) .. "}\n"
+  end
+
+  return pandoc.RawBlock(
+    "latex",
+    table.concat({
+      "\\begin{figure}[htbp]\n",
+      "\\centering\n",
+      "\\fbox{\\begin{minipage}{0.86\\linewidth}\n",
+      fallback_latex,
+      "\n\\end{minipage}}\n",
+      caption_line,
+      label_line(label),
+      "\\end{figure}",
+    })
+  )
+end
+
+local function env_to_latex(el)
+  local env_type = el.attributes.type or first_env_class(el)
+  if not env_type or not env_types[env_type] then
+    return nil
+  end
+
+  local title = el.attributes.title or el.attributes.name or ""
+  local begin_env = "\\begin{" .. env_type .. "}"
+  if title ~= "" then
+    begin_env = begin_env .. "[" .. latex_escape(title) .. "]"
+  end
+
+  return pandoc.RawBlock(
+    "latex",
+    table.concat({
+      begin_env,
+      "\n",
+      label_line(el.identifier),
+      markdown_to_latex(el.text),
+      "\n\\end{",
+      env_type,
+      "}",
+    })
+  )
+end
+
+function CodeBlock(el)
+  if FORMAT:match("latex") and has_class(el, "interactive") then
+    return interactive_to_latex(el)
+  end
+
+  if FORMAT:match("latex") and (has_class(el, "env") or has_class(el, "latex-env") or first_env_class(el)) then
+    return env_to_latex(el)
+  end
+
+  return nil
+end
+
+function Link(el)
+  return internal_link_to_cref(el)
+end
diff --git a/scripts/pandoc-templates/semantic-preamble.tex b/scripts/pandoc-templates/semantic-preamble.tex
new file mode 100644
index 0000000..821f242
--- /dev/null
+++ b/scripts/pandoc-templates/semantic-preamble.tex
@@ -0,0 +1,44 @@
+\usepackage{amsmath}
+\usepackage{amssymb}
+\usepackage{amsthm}
+
+\theoremstyle{plain}
+\newtheorem{theorem}{Theorem}
+\newtheorem{lemma}[theorem]{Lemma}
+\newtheorem{proposition}[theorem]{Proposition}
+\newtheorem{corollary}[theorem]{Corollary}
+
+\theoremstyle{definition}
+\newtheorem{definition}[theorem]{Definition}
+\newtheorem{example}[theorem]{Example}
+
+\theoremstyle{remark}
+\newtheorem{remark}[theorem]{Remark}
+
+\newcommand{\SemanticLoadCleveref}{%
+  \usepackage{cleveref}%
+  \crefname{theorem}{theorem}{theorems}%
+  \Crefname{theorem}{Theorem}{Theorems}%
+  \crefname{lemma}{lemma}{lemmas}%
+  \Crefname{lemma}{Lemma}{Lemmas}%
+  \crefname{proposition}{proposition}{propositions}%
+  \Crefname{proposition}{Proposition}{Propositions}%
+  \crefname{corollary}{corollary}{corollaries}%
+  \Crefname{corollary}{Corollary}{Corollaries}%
+  \crefname{definition}{definition}{definitions}%
+  \Crefname{definition}{Definition}{Definitions}%
+  \crefname{example}{example}{examples}%
+  \Crefname{example}{Example}{Examples}%
+  \crefname{remark}{remark}{remarks}%
+  \Crefname{remark}{Remark}{Remarks}%
+  \crefname{figure}{figure}{figures}%
+  \Crefname{figure}{Figure}{Figures}%
+}
+
+\makeatletter
+\@ifpackageloaded{hyperref}{%
+  \SemanticLoadCleveref
+}{%
+  \AddToHook{package/hyperref/after}{\SemanticLoadCleveref}%
+}
+\makeatother
diff --git a/sites/art/astro.config.mjs b/sites/art/astro.config.mjs
index 17d8510..254caf9 100644
--- a/sites/art/astro.config.mjs
+++ b/sites/art/astro.config.mjs
@@ -12,6 +12,7 @@ import tailwindcss from "@tailwindcss/vite";
 import remarkCallouts from "./src/remark/callouts.mjs";
 import remarkCodeFenceLanguages from "./src/remark/code-fence-languages.mjs";
 import remarkInlineFootnotes from "./src/remark/inline-footnotes.mjs";
+import remarkSemanticBlocks from "./src/remark/semantic-blocks.mjs";
 import remarkTypography from "./src/remark/typography.mjs";
 import { ACTIVE_BLOG_SITE } from "./src/blog-sites.js";
 
@@ -19,6 +20,7 @@ const remarkPlugins = [
   remarkGfm,
   remarkInlineFootnotes,
   remarkCodeFenceLanguages,
+  remarkSemanticBlocks,
   remarkMath,
   remarkTypography,
   remarkCallouts,
diff --git a/sites/art/src/components/InteractiveRuntime.astro b/sites/art/src/components/InteractiveRuntime.astro
new file mode 100644
index 0000000..0ee92fc
--- /dev/null
+++ b/sites/art/src/components/InteractiveRuntime.astro
@@ -0,0 +1,3 @@
+<script>
+  import "@/interactives/runtime";
+</script>
diff --git a/sites/art/src/interactives/runtime.tsx b/sites/art/src/interactives/runtime.tsx
new file mode 100644
index 0000000..f6191e2
--- /dev/null
+++ b/sites/art/src/interactives/runtime.tsx
@@ -0,0 +1,77 @@
+import React from "react";
+import { createRoot } from "react-dom/client";
+
+type InteractiveProps = {
+  id: string;
+  label: string;
+  caption?: string;
+  description?: string;
+  fallback?: string;
+  attrs?: Record<string, string>;
+};
+
+type InteractiveModule = {
+  default: React.ComponentType<InteractiveProps>;
+};
+
+const modules = import.meta.glob<InteractiveModule>("./*/index.tsx");
+
+function readProps(element: HTMLElement): InteractiveProps {
+  const encoded = element.dataset.interactiveProps;
+  if (!encoded) {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+    };
+  }
+
+  try {
+    return JSON.parse(decodeURIComponent(encoded)) as InteractiveProps;
+  } catch {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+      fallback: element.textContent?.trim() ?? "",
+    };
+  }
+}
+
+async function mountInteractive(element: HTMLElement) {
+  const id = element.dataset.interactiveId;
+  if (!id || element.dataset.interactiveMounted) return;
+
+  const modulePath = `./${id}/index.tsx`;
+  const loader = modules[modulePath];
+  if (!loader) {
+    element.dataset.interactiveState = "missing-component";
+    return;
+  }
+
+  element.dataset.interactiveMounted = "true";
+  element.dataset.interactiveState = "loading";
+
+  try {
+    const props = readProps(element);
+    const { default: Component } = await loader();
+    element.replaceChildren();
+    createRoot(element).render(<Component {...props} />);
+    element.dataset.interactiveState = "ready";
+  } catch (error) {
+    element.dataset.interactiveState = "failed";
+    console.error(`Failed to mount interactive "${id}"`, error);
+  }
+}
+
+function mountAllInteractives() {
+  document
+    .querySelectorAll<HTMLElement>(".interactive-mount[data-interactive-id]")
+    .forEach((element) => {
+      void mountInteractive(element);
+    });
+}
+
+if (document.readyState === "loading") {
+  document.addEventListener("DOMContentLoaded", mountAllInteractives, { once: true });
+} else {
+  mountAllInteractives();
+}
diff --git a/sites/art/src/pages/[...slug].astro b/sites/art/src/pages/[...slug].astro
index 4b14673..2d2e6f2 100644
--- a/sites/art/src/pages/[...slug].astro
+++ b/sites/art/src/pages/[...slug].astro
@@ -1,6 +1,7 @@
 ---
 import { getCollection, render } from 'astro:content';
 import CoralComments from '@/components/CoralComments.astro';
+import InteractiveRuntime from '@/components/InteractiveRuntime.astro';
 import DefaultLayout from '@/layouts/DefaultLayout.astro';
 import { BlogPost } from '@/components/sections/blog-post';
 import { ACTIVE_BLOG_SITE } from '@/blog-sites.js';
@@ -26,5 +27,6 @@ const coralStoryURL = new URL(`/${postSlug}/`, ACTIVE_BLOG_SITE.url).toString();
 		<Content />
 	</BlogPost>
 
+	<InteractiveRuntime />
 	<CoralComments storyID={coralStoryID} storyURL={coralStoryURL} />
 </DefaultLayout>
diff --git a/sites/art/src/remark/semantic-blocks.mjs b/sites/art/src/remark/semantic-blocks.mjs
new file mode 100644
index 0000000..fe86b96
--- /dev/null
+++ b/sites/art/src/remark/semantic-blocks.mjs
@@ -0,0 +1,232 @@
+import { fromMarkdown } from "mdast-util-from-markdown";
+
+const ENV_TYPES = new Set([
+  "theorem",
+  "lemma",
+  "proposition",
+  "corollary",
+  "definition",
+  "example",
+  "remark",
+  "proof",
+]);
+
+const ENV_LABELS = {
+  theorem: "Theorem",
+  lemma: "Lemma",
+  proposition: "Proposition",
+  corollary: "Corollary",
+  definition: "Definition",
+  example: "Example",
+  remark: "Remark",
+  proof: "Proof",
+};
+
+function tokenizeInfo(info) {
+  return (
+    info.match(/[^\s=]+=(?:"[^"]*"|'[^']*'|[^\s]+)|"[^"]*"|'[^']*'|[^\s]+/g) ?? []
+  );
+}
+
+function stripQuotes(value) {
+  if (!value) return "";
+  const first = value[0];
+  const last = value[value.length - 1];
+  if ((first === '"' && last === '"') || (first === "'" && last === "'")) {
+    return value.slice(1, -1);
+  }
+  return value;
+}
+
+function parseFenceInfo(node) {
+  const lang = node.lang ?? "";
+  const meta = node.meta ?? "";
+  const raw = `${lang} ${meta}`.trim();
+  const attrs = {
+    classes: [],
+    id: "",
+    values: {},
+    raw,
+  };
+
+  if (!raw) return attrs;
+
+  let body = raw;
+  if (body.startsWith("{")) {
+    body = body.slice(1);
+    if (body.endsWith("}")) body = body.slice(0, -1);
+  } else if (lang) {
+    attrs.classes.push(lang);
+    body = meta;
+  }
+
+  for (let token of tokenizeInfo(body.trim())) {
+    if (token.endsWith("}") && !token.includes("=")) token = token.slice(0, -1);
+    if (!token) continue;
+
+    if (token.startsWith(".")) {
+      attrs.classes.push(token.slice(1));
+      continue;
+    }
+
+    if (token.startsWith("#")) {
+      attrs.id = token.slice(1);
+      continue;
+    }
+
+    const eq = token.indexOf("=");
+    if (eq > 0) {
+      const key = token.slice(0, eq);
+      const value = stripQuotes(token.slice(eq + 1));
+      if (key === "id") attrs.id = value;
+      attrs.values[key] = value;
+    }
+  }
+
+  return attrs;
+}
+
+function escapeHtml(value) {
+  return String(value)
+    .replaceAll("&", "&amp;")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;")
+    .replaceAll('"', "&quot;");
+}
+
+function attribute(value) {
+  return escapeHtml(value).replaceAll("\n", " ");
+}
+
+function encodedJson(value) {
+  return encodeURIComponent(JSON.stringify(value));
+}
+
+function firstClass(attrs, excluded) {
+  return attrs.classes.find((className) => !excluded.has(className));
+}
+
+function interactiveFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  if (!attrs.classes.includes("interactive")) return null;
+
+  const declaredId = attrs.id || attrs.values.component || attrs.values.name || "";
+  const componentId =
+    attrs.values.component ||
+    (declaredId.startsWith("int:") ? declaredId.slice("int:".length) : declaredId);
+  const label = attrs.values.label || (declaredId.startsWith("int:") ? declaredId : `int:${declaredId}`);
+  const caption = attrs.values.caption || attrs.values.title || "";
+  const description = node.value.trim();
+  const fallback = attrs.values.pdf || attrs.values.fallback || description || caption;
+
+  if (!componentId) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Interactive block missing an id. Add <code>#int:name</code> or <code>id="name"</code>.</aside>',
+    };
+  }
+
+  const props = {
+    id: componentId,
+    label,
+    caption,
+    description,
+    fallback,
+    attrs: attrs.values,
+  };
+
+  return {
+    type: "html",
+    value: [
+      `<figure class="semantic-interactive" id="${attribute(label)}" data-interactive-label="${attribute(label)}">`,
+      `<div class="interactive-mount" data-interactive-id="${attribute(componentId)}" data-interactive-props="${attribute(encodedJson(props))}">`,
+      fallback ? `<p class="interactive-fallback">${escapeHtml(fallback)}</p>` : "",
+      "</div>",
+      caption ? `<figcaption>${escapeHtml(caption)}</figcaption>` : "",
+      "</figure>",
+    ].join(""),
+  };
+}
+
+function envFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  const shorthandType = firstClass(attrs, new Set(["env", "latex-env"]));
+  const explicitType = attrs.values.type || shorthandType;
+  const type = ENV_TYPES.has(explicitType) ? explicitType : "";
+  const isEnv = attrs.classes.includes("env") || attrs.classes.includes("latex-env") || Boolean(type);
+
+  if (!isEnv) return null;
+
+  if (!type) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Environment block missing a type. Add <code>.theorem</code>, <code>.definition</code>, or <code>type="theorem"</code>.</aside>',
+    };
+  }
+
+  const title = attrs.values.title || attrs.values.name || "";
+  const label = attrs.id || attrs.values.label || "";
+  const renderMode = attrs.values.html || (type === "proof" ? "plain" : "callout");
+  const heading = title ? `${ENV_LABELS[type]} (${title})` : ENV_LABELS[type];
+  const parsed = fromMarkdown(node.value || "");
+  const className = [
+    "semantic-env",
+    `semantic-env-${type}`,
+    `semantic-env-${renderMode}`,
+    renderMode === "callout" ? "callout" : "",
+  ].filter(Boolean);
+
+  return {
+    type: "blockquote",
+    data: {
+      hName: "section",
+      hProperties: {
+        id: label || undefined,
+        className,
+        "data-env-type": type,
+        "data-env-title": title || undefined,
+        "data-env-render": renderMode,
+      },
+    },
+    children: [
+      {
+        type: "paragraph",
+        data: {
+          hProperties: {
+            className: ["semantic-env-heading"],
+          },
+        },
+        children: [
+          {
+            type: "strong",
+            children: [{ type: "text", value: heading }],
+          },
+        ],
+      },
+      ...parsed.children,
+    ],
+  };
+}
+
+function transformTree(parent) {
+  if (!parent?.children) return;
+
+  for (let index = 0; index < parent.children.length; index += 1) {
+    const child = parent.children[index];
+    if (child.type === "code") {
+      const replacement = interactiveFromCode(child) || envFromCode(child);
+      if (replacement) {
+        parent.children[index] = replacement;
+        continue;
+      }
+    }
+
+    transformTree(child);
+  }
+}
+
+export default function remarkSemanticBlocks() {
+  return (tree) => transformTree(tree);
+}
diff --git a/sites/art/src/styles/article.css b/sites/art/src/styles/article.css
index 798a3b9..e39264f 100644
--- a/sites/art/src/styles/article.css
+++ b/sites/art/src/styles/article.css
@@ -216,6 +216,48 @@
   margin-bottom: 0.35rem;
 }
 
+.article-content :where(.semantic-env) {
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.semantic-env-heading) {
+  margin: 0 0 0.75rem;
+  color: color-mix(in srgb, hsl(var(--primary)) 78%, hsl(var(--foreground)));
+  font-family: var(--font-mono);
+  font-size: 0.78rem;
+  font-weight: 700;
+  letter-spacing: 0.08em;
+  line-height: 1.3;
+  text-transform: uppercase;
+}
+
+.article-content :where(.semantic-env-heading strong) {
+  font-weight: inherit;
+}
+
+.article-content :where(.semantic-env-plain) {
+  margin-block: 1.6rem;
+  border-left: 3px solid hsl(var(--primary));
+  padding: 0.15rem 0 0.15rem 1rem;
+}
+
+.article-content :where(.semantic-env-plain > *:first-child) {
+  margin-top: 0;
+}
+
+.article-content :where(.semantic-env-plain > *:last-child) {
+  margin-bottom: 0;
+}
+
+.article-content :where(.semantic-error) {
+  margin-block: 1.5rem;
+  border: 1px solid color-mix(in srgb, hsl(var(--destructive)) 50%, hsl(var(--border)));
+  border-radius: 0.55rem;
+  background: color-mix(in srgb, hsl(var(--destructive)) 8%, transparent);
+  padding: 1rem;
+  color: hsl(var(--foreground));
+}
+
 .article-content :where(.callout hr) {
   margin-block: 1rem;
   border-top-color: color-mix(in srgb, hsl(var(--border)) 70%, transparent);
@@ -248,6 +290,33 @@
   margin-inline: 0;
 }
 
+.article-content :where(.semantic-interactive) {
+  margin-block: 2rem;
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.interactive-mount) {
+  min-height: 12rem;
+  border: 1px solid hsl(var(--border));
+  border-radius: 0.65rem;
+  background: color-mix(in srgb, hsl(var(--accent)) 20%, transparent);
+  padding: 1rem;
+}
+
+.article-content :where(.interactive-mount[data-interactive-state="missing-component"]) {
+  display: grid;
+  min-height: 8rem;
+  place-items: center;
+  color: hsl(var(--muted-foreground));
+  font-size: 0.95rem;
+  text-align: center;
+}
+
+.article-content :where(.interactive-fallback) {
+  margin: 0;
+  color: hsl(var(--muted-foreground));
+}
+
 .article-content :where(figcaption) {
   color: hsl(var(--muted-foreground));
   font-size: 0.92rem;
diff --git a/sites/poetry/astro.config.mjs b/sites/poetry/astro.config.mjs
index 17d8510..254caf9 100644
--- a/sites/poetry/astro.config.mjs
+++ b/sites/poetry/astro.config.mjs
@@ -12,6 +12,7 @@ import tailwindcss from "@tailwindcss/vite";
 import remarkCallouts from "./src/remark/callouts.mjs";
 import remarkCodeFenceLanguages from "./src/remark/code-fence-languages.mjs";
 import remarkInlineFootnotes from "./src/remark/inline-footnotes.mjs";
+import remarkSemanticBlocks from "./src/remark/semantic-blocks.mjs";
 import remarkTypography from "./src/remark/typography.mjs";
 import { ACTIVE_BLOG_SITE } from "./src/blog-sites.js";
 
@@ -19,6 +20,7 @@ const remarkPlugins = [
   remarkGfm,
   remarkInlineFootnotes,
   remarkCodeFenceLanguages,
+  remarkSemanticBlocks,
   remarkMath,
   remarkTypography,
   remarkCallouts,
diff --git a/sites/poetry/src/components/InteractiveRuntime.astro b/sites/poetry/src/components/InteractiveRuntime.astro
new file mode 100644
index 0000000..0ee92fc
--- /dev/null
+++ b/sites/poetry/src/components/InteractiveRuntime.astro
@@ -0,0 +1,3 @@
+<script>
+  import "@/interactives/runtime";
+</script>
diff --git a/sites/poetry/src/interactives/runtime.tsx b/sites/poetry/src/interactives/runtime.tsx
new file mode 100644
index 0000000..f6191e2
--- /dev/null
+++ b/sites/poetry/src/interactives/runtime.tsx
@@ -0,0 +1,77 @@
+import React from "react";
+import { createRoot } from "react-dom/client";
+
+type InteractiveProps = {
+  id: string;
+  label: string;
+  caption?: string;
+  description?: string;
+  fallback?: string;
+  attrs?: Record<string, string>;
+};
+
+type InteractiveModule = {
+  default: React.ComponentType<InteractiveProps>;
+};
+
+const modules = import.meta.glob<InteractiveModule>("./*/index.tsx");
+
+function readProps(element: HTMLElement): InteractiveProps {
+  const encoded = element.dataset.interactiveProps;
+  if (!encoded) {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+    };
+  }
+
+  try {
+    return JSON.parse(decodeURIComponent(encoded)) as InteractiveProps;
+  } catch {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+      fallback: element.textContent?.trim() ?? "",
+    };
+  }
+}
+
+async function mountInteractive(element: HTMLElement) {
+  const id = element.dataset.interactiveId;
+  if (!id || element.dataset.interactiveMounted) return;
+
+  const modulePath = `./${id}/index.tsx`;
+  const loader = modules[modulePath];
+  if (!loader) {
+    element.dataset.interactiveState = "missing-component";
+    return;
+  }
+
+  element.dataset.interactiveMounted = "true";
+  element.dataset.interactiveState = "loading";
+
+  try {
+    const props = readProps(element);
+    const { default: Component } = await loader();
+    element.replaceChildren();
+    createRoot(element).render(<Component {...props} />);
+    element.dataset.interactiveState = "ready";
+  } catch (error) {
+    element.dataset.interactiveState = "failed";
+    console.error(`Failed to mount interactive "${id}"`, error);
+  }
+}
+
+function mountAllInteractives() {
+  document
+    .querySelectorAll<HTMLElement>(".interactive-mount[data-interactive-id]")
+    .forEach((element) => {
+      void mountInteractive(element);
+    });
+}
+
+if (document.readyState === "loading") {
+  document.addEventListener("DOMContentLoaded", mountAllInteractives, { once: true });
+} else {
+  mountAllInteractives();
+}
diff --git a/sites/poetry/src/pages/[...slug].astro b/sites/poetry/src/pages/[...slug].astro
index 60add23..32b2041 100644
--- a/sites/poetry/src/pages/[...slug].astro
+++ b/sites/poetry/src/pages/[...slug].astro
@@ -1,6 +1,7 @@
 ---
 import { getCollection, render } from 'astro:content';
 import CoralComments from '@/components/CoralComments.astro';
+import InteractiveRuntime from '@/components/InteractiveRuntime.astro';
 import DefaultLayout from '@/layouts/DefaultLayout.astro';
 import { BlogPost } from '@/components/sections/blog-post';
 import { ACTIVE_BLOG_SITE } from '@/blog-sites.js';
@@ -28,5 +29,6 @@ const coralStoryURL = new URL(`/${postSlug}/`, ACTIVE_BLOG_SITE.url).toString();
 		</BlogPost>
 	</div>
 
+	<InteractiveRuntime />
 	<CoralComments storyID={coralStoryID} storyURL={coralStoryURL} />
 </DefaultLayout>
diff --git a/sites/poetry/src/remark/semantic-blocks.mjs b/sites/poetry/src/remark/semantic-blocks.mjs
new file mode 100644
index 0000000..fe86b96
--- /dev/null
+++ b/sites/poetry/src/remark/semantic-blocks.mjs
@@ -0,0 +1,232 @@
+import { fromMarkdown } from "mdast-util-from-markdown";
+
+const ENV_TYPES = new Set([
+  "theorem",
+  "lemma",
+  "proposition",
+  "corollary",
+  "definition",
+  "example",
+  "remark",
+  "proof",
+]);
+
+const ENV_LABELS = {
+  theorem: "Theorem",
+  lemma: "Lemma",
+  proposition: "Proposition",
+  corollary: "Corollary",
+  definition: "Definition",
+  example: "Example",
+  remark: "Remark",
+  proof: "Proof",
+};
+
+function tokenizeInfo(info) {
+  return (
+    info.match(/[^\s=]+=(?:"[^"]*"|'[^']*'|[^\s]+)|"[^"]*"|'[^']*'|[^\s]+/g) ?? []
+  );
+}
+
+function stripQuotes(value) {
+  if (!value) return "";
+  const first = value[0];
+  const last = value[value.length - 1];
+  if ((first === '"' && last === '"') || (first === "'" && last === "'")) {
+    return value.slice(1, -1);
+  }
+  return value;
+}
+
+function parseFenceInfo(node) {
+  const lang = node.lang ?? "";
+  const meta = node.meta ?? "";
+  const raw = `${lang} ${meta}`.trim();
+  const attrs = {
+    classes: [],
+    id: "",
+    values: {},
+    raw,
+  };
+
+  if (!raw) return attrs;
+
+  let body = raw;
+  if (body.startsWith("{")) {
+    body = body.slice(1);
+    if (body.endsWith("}")) body = body.slice(0, -1);
+  } else if (lang) {
+    attrs.classes.push(lang);
+    body = meta;
+  }
+
+  for (let token of tokenizeInfo(body.trim())) {
+    if (token.endsWith("}") && !token.includes("=")) token = token.slice(0, -1);
+    if (!token) continue;
+
+    if (token.startsWith(".")) {
+      attrs.classes.push(token.slice(1));
+      continue;
+    }
+
+    if (token.startsWith("#")) {
+      attrs.id = token.slice(1);
+      continue;
+    }
+
+    const eq = token.indexOf("=");
+    if (eq > 0) {
+      const key = token.slice(0, eq);
+      const value = stripQuotes(token.slice(eq + 1));
+      if (key === "id") attrs.id = value;
+      attrs.values[key] = value;
+    }
+  }
+
+  return attrs;
+}
+
+function escapeHtml(value) {
+  return String(value)
+    .replaceAll("&", "&amp;")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;")
+    .replaceAll('"', "&quot;");
+}
+
+function attribute(value) {
+  return escapeHtml(value).replaceAll("\n", " ");
+}
+
+function encodedJson(value) {
+  return encodeURIComponent(JSON.stringify(value));
+}
+
+function firstClass(attrs, excluded) {
+  return attrs.classes.find((className) => !excluded.has(className));
+}
+
+function interactiveFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  if (!attrs.classes.includes("interactive")) return null;
+
+  const declaredId = attrs.id || attrs.values.component || attrs.values.name || "";
+  const componentId =
+    attrs.values.component ||
+    (declaredId.startsWith("int:") ? declaredId.slice("int:".length) : declaredId);
+  const label = attrs.values.label || (declaredId.startsWith("int:") ? declaredId : `int:${declaredId}`);
+  const caption = attrs.values.caption || attrs.values.title || "";
+  const description = node.value.trim();
+  const fallback = attrs.values.pdf || attrs.values.fallback || description || caption;
+
+  if (!componentId) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Interactive block missing an id. Add <code>#int:name</code> or <code>id="name"</code>.</aside>',
+    };
+  }
+
+  const props = {
+    id: componentId,
+    label,
+    caption,
+    description,
+    fallback,
+    attrs: attrs.values,
+  };
+
+  return {
+    type: "html",
+    value: [
+      `<figure class="semantic-interactive" id="${attribute(label)}" data-interactive-label="${attribute(label)}">`,
+      `<div class="interactive-mount" data-interactive-id="${attribute(componentId)}" data-interactive-props="${attribute(encodedJson(props))}">`,
+      fallback ? `<p class="interactive-fallback">${escapeHtml(fallback)}</p>` : "",
+      "</div>",
+      caption ? `<figcaption>${escapeHtml(caption)}</figcaption>` : "",
+      "</figure>",
+    ].join(""),
+  };
+}
+
+function envFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  const shorthandType = firstClass(attrs, new Set(["env", "latex-env"]));
+  const explicitType = attrs.values.type || shorthandType;
+  const type = ENV_TYPES.has(explicitType) ? explicitType : "";
+  const isEnv = attrs.classes.includes("env") || attrs.classes.includes("latex-env") || Boolean(type);
+
+  if (!isEnv) return null;
+
+  if (!type) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Environment block missing a type. Add <code>.theorem</code>, <code>.definition</code>, or <code>type="theorem"</code>.</aside>',
+    };
+  }
+
+  const title = attrs.values.title || attrs.values.name || "";
+  const label = attrs.id || attrs.values.label || "";
+  const renderMode = attrs.values.html || (type === "proof" ? "plain" : "callout");
+  const heading = title ? `${ENV_LABELS[type]} (${title})` : ENV_LABELS[type];
+  const parsed = fromMarkdown(node.value || "");
+  const className = [
+    "semantic-env",
+    `semantic-env-${type}`,
+    `semantic-env-${renderMode}`,
+    renderMode === "callout" ? "callout" : "",
+  ].filter(Boolean);
+
+  return {
+    type: "blockquote",
+    data: {
+      hName: "section",
+      hProperties: {
+        id: label || undefined,
+        className,
+        "data-env-type": type,
+        "data-env-title": title || undefined,
+        "data-env-render": renderMode,
+      },
+    },
+    children: [
+      {
+        type: "paragraph",
+        data: {
+          hProperties: {
+            className: ["semantic-env-heading"],
+          },
+        },
+        children: [
+          {
+            type: "strong",
+            children: [{ type: "text", value: heading }],
+          },
+        ],
+      },
+      ...parsed.children,
+    ],
+  };
+}
+
+function transformTree(parent) {
+  if (!parent?.children) return;
+
+  for (let index = 0; index < parent.children.length; index += 1) {
+    const child = parent.children[index];
+    if (child.type === "code") {
+      const replacement = interactiveFromCode(child) || envFromCode(child);
+      if (replacement) {
+        parent.children[index] = replacement;
+        continue;
+      }
+    }
+
+    transformTree(child);
+  }
+}
+
+export default function remarkSemanticBlocks() {
+  return (tree) => transformTree(tree);
+}
diff --git a/sites/poetry/src/styles/article.css b/sites/poetry/src/styles/article.css
index 798a3b9..e39264f 100644
--- a/sites/poetry/src/styles/article.css
+++ b/sites/poetry/src/styles/article.css
@@ -216,6 +216,48 @@
   margin-bottom: 0.35rem;
 }
 
+.article-content :where(.semantic-env) {
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.semantic-env-heading) {
+  margin: 0 0 0.75rem;
+  color: color-mix(in srgb, hsl(var(--primary)) 78%, hsl(var(--foreground)));
+  font-family: var(--font-mono);
+  font-size: 0.78rem;
+  font-weight: 700;
+  letter-spacing: 0.08em;
+  line-height: 1.3;
+  text-transform: uppercase;
+}
+
+.article-content :where(.semantic-env-heading strong) {
+  font-weight: inherit;
+}
+
+.article-content :where(.semantic-env-plain) {
+  margin-block: 1.6rem;
+  border-left: 3px solid hsl(var(--primary));
+  padding: 0.15rem 0 0.15rem 1rem;
+}
+
+.article-content :where(.semantic-env-plain > *:first-child) {
+  margin-top: 0;
+}
+
+.article-content :where(.semantic-env-plain > *:last-child) {
+  margin-bottom: 0;
+}
+
+.article-content :where(.semantic-error) {
+  margin-block: 1.5rem;
+  border: 1px solid color-mix(in srgb, hsl(var(--destructive)) 50%, hsl(var(--border)));
+  border-radius: 0.55rem;
+  background: color-mix(in srgb, hsl(var(--destructive)) 8%, transparent);
+  padding: 1rem;
+  color: hsl(var(--foreground));
+}
+
 .article-content :where(.callout hr) {
   margin-block: 1rem;
   border-top-color: color-mix(in srgb, hsl(var(--border)) 70%, transparent);
@@ -248,6 +290,33 @@
   margin-inline: 0;
 }
 
+.article-content :where(.semantic-interactive) {
+  margin-block: 2rem;
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.interactive-mount) {
+  min-height: 12rem;
+  border: 1px solid hsl(var(--border));
+  border-radius: 0.65rem;
+  background: color-mix(in srgb, hsl(var(--accent)) 20%, transparent);
+  padding: 1rem;
+}
+
+.article-content :where(.interactive-mount[data-interactive-state="missing-component"]) {
+  display: grid;
+  min-height: 8rem;
+  place-items: center;
+  color: hsl(var(--muted-foreground));
+  font-size: 0.95rem;
+  text-align: center;
+}
+
+.article-content :where(.interactive-fallback) {
+  margin: 0;
+  color: hsl(var(--muted-foreground));
+}
+
 .article-content :where(figcaption) {
   color: hsl(var(--muted-foreground));
   font-size: 0.92rem;
diff --git a/sites/puzzles/astro.config.mjs b/sites/puzzles/astro.config.mjs
index 17d8510..254caf9 100644
--- a/sites/puzzles/astro.config.mjs
+++ b/sites/puzzles/astro.config.mjs
@@ -12,6 +12,7 @@ import tailwindcss from "@tailwindcss/vite";
 import remarkCallouts from "./src/remark/callouts.mjs";
 import remarkCodeFenceLanguages from "./src/remark/code-fence-languages.mjs";
 import remarkInlineFootnotes from "./src/remark/inline-footnotes.mjs";
+import remarkSemanticBlocks from "./src/remark/semantic-blocks.mjs";
 import remarkTypography from "./src/remark/typography.mjs";
 import { ACTIVE_BLOG_SITE } from "./src/blog-sites.js";
 
@@ -19,6 +20,7 @@ const remarkPlugins = [
   remarkGfm,
   remarkInlineFootnotes,
   remarkCodeFenceLanguages,
+  remarkSemanticBlocks,
   remarkMath,
   remarkTypography,
   remarkCallouts,
diff --git a/sites/puzzles/src/components/InteractiveRuntime.astro b/sites/puzzles/src/components/InteractiveRuntime.astro
new file mode 100644
index 0000000..0ee92fc
--- /dev/null
+++ b/sites/puzzles/src/components/InteractiveRuntime.astro
@@ -0,0 +1,3 @@
+<script>
+  import "@/interactives/runtime";
+</script>
diff --git a/sites/puzzles/src/interactives/runtime.tsx b/sites/puzzles/src/interactives/runtime.tsx
new file mode 100644
index 0000000..f6191e2
--- /dev/null
+++ b/sites/puzzles/src/interactives/runtime.tsx
@@ -0,0 +1,77 @@
+import React from "react";
+import { createRoot } from "react-dom/client";
+
+type InteractiveProps = {
+  id: string;
+  label: string;
+  caption?: string;
+  description?: string;
+  fallback?: string;
+  attrs?: Record<string, string>;
+};
+
+type InteractiveModule = {
+  default: React.ComponentType<InteractiveProps>;
+};
+
+const modules = import.meta.glob<InteractiveModule>("./*/index.tsx");
+
+function readProps(element: HTMLElement): InteractiveProps {
+  const encoded = element.dataset.interactiveProps;
+  if (!encoded) {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+    };
+  }
+
+  try {
+    return JSON.parse(decodeURIComponent(encoded)) as InteractiveProps;
+  } catch {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+      fallback: element.textContent?.trim() ?? "",
+    };
+  }
+}
+
+async function mountInteractive(element: HTMLElement) {
+  const id = element.dataset.interactiveId;
+  if (!id || element.dataset.interactiveMounted) return;
+
+  const modulePath = `./${id}/index.tsx`;
+  const loader = modules[modulePath];
+  if (!loader) {
+    element.dataset.interactiveState = "missing-component";
+    return;
+  }
+
+  element.dataset.interactiveMounted = "true";
+  element.dataset.interactiveState = "loading";
+
+  try {
+    const props = readProps(element);
+    const { default: Component } = await loader();
+    element.replaceChildren();
+    createRoot(element).render(<Component {...props} />);
+    element.dataset.interactiveState = "ready";
+  } catch (error) {
+    element.dataset.interactiveState = "failed";
+    console.error(`Failed to mount interactive "${id}"`, error);
+  }
+}
+
+function mountAllInteractives() {
+  document
+    .querySelectorAll<HTMLElement>(".interactive-mount[data-interactive-id]")
+    .forEach((element) => {
+      void mountInteractive(element);
+    });
+}
+
+if (document.readyState === "loading") {
+  document.addEventListener("DOMContentLoaded", mountAllInteractives, { once: true });
+} else {
+  mountAllInteractives();
+}
diff --git a/sites/puzzles/src/pages/[...slug].astro b/sites/puzzles/src/pages/[...slug].astro
index 4b14673..2d2e6f2 100644
--- a/sites/puzzles/src/pages/[...slug].astro
+++ b/sites/puzzles/src/pages/[...slug].astro
@@ -1,6 +1,7 @@
 ---
 import { getCollection, render } from 'astro:content';
 import CoralComments from '@/components/CoralComments.astro';
+import InteractiveRuntime from '@/components/InteractiveRuntime.astro';
 import DefaultLayout from '@/layouts/DefaultLayout.astro';
 import { BlogPost } from '@/components/sections/blog-post';
 import { ACTIVE_BLOG_SITE } from '@/blog-sites.js';
@@ -26,5 +27,6 @@ const coralStoryURL = new URL(`/${postSlug}/`, ACTIVE_BLOG_SITE.url).toString();
 		<Content />
 	</BlogPost>
 
+	<InteractiveRuntime />
 	<CoralComments storyID={coralStoryID} storyURL={coralStoryURL} />
 </DefaultLayout>
diff --git a/sites/puzzles/src/remark/semantic-blocks.mjs b/sites/puzzles/src/remark/semantic-blocks.mjs
new file mode 100644
index 0000000..fe86b96
--- /dev/null
+++ b/sites/puzzles/src/remark/semantic-blocks.mjs
@@ -0,0 +1,232 @@
+import { fromMarkdown } from "mdast-util-from-markdown";
+
+const ENV_TYPES = new Set([
+  "theorem",
+  "lemma",
+  "proposition",
+  "corollary",
+  "definition",
+  "example",
+  "remark",
+  "proof",
+]);
+
+const ENV_LABELS = {
+  theorem: "Theorem",
+  lemma: "Lemma",
+  proposition: "Proposition",
+  corollary: "Corollary",
+  definition: "Definition",
+  example: "Example",
+  remark: "Remark",
+  proof: "Proof",
+};
+
+function tokenizeInfo(info) {
+  return (
+    info.match(/[^\s=]+=(?:"[^"]*"|'[^']*'|[^\s]+)|"[^"]*"|'[^']*'|[^\s]+/g) ?? []
+  );
+}
+
+function stripQuotes(value) {
+  if (!value) return "";
+  const first = value[0];
+  const last = value[value.length - 1];
+  if ((first === '"' && last === '"') || (first === "'" && last === "'")) {
+    return value.slice(1, -1);
+  }
+  return value;
+}
+
+function parseFenceInfo(node) {
+  const lang = node.lang ?? "";
+  const meta = node.meta ?? "";
+  const raw = `${lang} ${meta}`.trim();
+  const attrs = {
+    classes: [],
+    id: "",
+    values: {},
+    raw,
+  };
+
+  if (!raw) return attrs;
+
+  let body = raw;
+  if (body.startsWith("{")) {
+    body = body.slice(1);
+    if (body.endsWith("}")) body = body.slice(0, -1);
+  } else if (lang) {
+    attrs.classes.push(lang);
+    body = meta;
+  }
+
+  for (let token of tokenizeInfo(body.trim())) {
+    if (token.endsWith("}") && !token.includes("=")) token = token.slice(0, -1);
+    if (!token) continue;
+
+    if (token.startsWith(".")) {
+      attrs.classes.push(token.slice(1));
+      continue;
+    }
+
+    if (token.startsWith("#")) {
+      attrs.id = token.slice(1);
+      continue;
+    }
+
+    const eq = token.indexOf("=");
+    if (eq > 0) {
+      const key = token.slice(0, eq);
+      const value = stripQuotes(token.slice(eq + 1));
+      if (key === "id") attrs.id = value;
+      attrs.values[key] = value;
+    }
+  }
+
+  return attrs;
+}
+
+function escapeHtml(value) {
+  return String(value)
+    .replaceAll("&", "&amp;")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;")
+    .replaceAll('"', "&quot;");
+}
+
+function attribute(value) {
+  return escapeHtml(value).replaceAll("\n", " ");
+}
+
+function encodedJson(value) {
+  return encodeURIComponent(JSON.stringify(value));
+}
+
+function firstClass(attrs, excluded) {
+  return attrs.classes.find((className) => !excluded.has(className));
+}
+
+function interactiveFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  if (!attrs.classes.includes("interactive")) return null;
+
+  const declaredId = attrs.id || attrs.values.component || attrs.values.name || "";
+  const componentId =
+    attrs.values.component ||
+    (declaredId.startsWith("int:") ? declaredId.slice("int:".length) : declaredId);
+  const label = attrs.values.label || (declaredId.startsWith("int:") ? declaredId : `int:${declaredId}`);
+  const caption = attrs.values.caption || attrs.values.title || "";
+  const description = node.value.trim();
+  const fallback = attrs.values.pdf || attrs.values.fallback || description || caption;
+
+  if (!componentId) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Interactive block missing an id. Add <code>#int:name</code> or <code>id="name"</code>.</aside>',
+    };
+  }
+
+  const props = {
+    id: componentId,
+    label,
+    caption,
+    description,
+    fallback,
+    attrs: attrs.values,
+  };
+
+  return {
+    type: "html",
+    value: [
+      `<figure class="semantic-interactive" id="${attribute(label)}" data-interactive-label="${attribute(label)}">`,
+      `<div class="interactive-mount" data-interactive-id="${attribute(componentId)}" data-interactive-props="${attribute(encodedJson(props))}">`,
+      fallback ? `<p class="interactive-fallback">${escapeHtml(fallback)}</p>` : "",
+      "</div>",
+      caption ? `<figcaption>${escapeHtml(caption)}</figcaption>` : "",
+      "</figure>",
+    ].join(""),
+  };
+}
+
+function envFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  const shorthandType = firstClass(attrs, new Set(["env", "latex-env"]));
+  const explicitType = attrs.values.type || shorthandType;
+  const type = ENV_TYPES.has(explicitType) ? explicitType : "";
+  const isEnv = attrs.classes.includes("env") || attrs.classes.includes("latex-env") || Boolean(type);
+
+  if (!isEnv) return null;
+
+  if (!type) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Environment block missing a type. Add <code>.theorem</code>, <code>.definition</code>, or <code>type="theorem"</code>.</aside>',
+    };
+  }
+
+  const title = attrs.values.title || attrs.values.name || "";
+  const label = attrs.id || attrs.values.label || "";
+  const renderMode = attrs.values.html || (type === "proof" ? "plain" : "callout");
+  const heading = title ? `${ENV_LABELS[type]} (${title})` : ENV_LABELS[type];
+  const parsed = fromMarkdown(node.value || "");
+  const className = [
+    "semantic-env",
+    `semantic-env-${type}`,
+    `semantic-env-${renderMode}`,
+    renderMode === "callout" ? "callout" : "",
+  ].filter(Boolean);
+
+  return {
+    type: "blockquote",
+    data: {
+      hName: "section",
+      hProperties: {
+        id: label || undefined,
+        className,
+        "data-env-type": type,
+        "data-env-title": title || undefined,
+        "data-env-render": renderMode,
+      },
+    },
+    children: [
+      {
+        type: "paragraph",
+        data: {
+          hProperties: {
+            className: ["semantic-env-heading"],
+          },
+        },
+        children: [
+          {
+            type: "strong",
+            children: [{ type: "text", value: heading }],
+          },
+        ],
+      },
+      ...parsed.children,
+    ],
+  };
+}
+
+function transformTree(parent) {
+  if (!parent?.children) return;
+
+  for (let index = 0; index < parent.children.length; index += 1) {
+    const child = parent.children[index];
+    if (child.type === "code") {
+      const replacement = interactiveFromCode(child) || envFromCode(child);
+      if (replacement) {
+        parent.children[index] = replacement;
+        continue;
+      }
+    }
+
+    transformTree(child);
+  }
+}
+
+export default function remarkSemanticBlocks() {
+  return (tree) => transformTree(tree);
+}
diff --git a/sites/puzzles/src/styles/article.css b/sites/puzzles/src/styles/article.css
index 798a3b9..e39264f 100644
--- a/sites/puzzles/src/styles/article.css
+++ b/sites/puzzles/src/styles/article.css
@@ -216,6 +216,48 @@
   margin-bottom: 0.35rem;
 }
 
+.article-content :where(.semantic-env) {
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.semantic-env-heading) {
+  margin: 0 0 0.75rem;
+  color: color-mix(in srgb, hsl(var(--primary)) 78%, hsl(var(--foreground)));
+  font-family: var(--font-mono);
+  font-size: 0.78rem;
+  font-weight: 700;
+  letter-spacing: 0.08em;
+  line-height: 1.3;
+  text-transform: uppercase;
+}
+
+.article-content :where(.semantic-env-heading strong) {
+  font-weight: inherit;
+}
+
+.article-content :where(.semantic-env-plain) {
+  margin-block: 1.6rem;
+  border-left: 3px solid hsl(var(--primary));
+  padding: 0.15rem 0 0.15rem 1rem;
+}
+
+.article-content :where(.semantic-env-plain > *:first-child) {
+  margin-top: 0;
+}
+
+.article-content :where(.semantic-env-plain > *:last-child) {
+  margin-bottom: 0;
+}
+
+.article-content :where(.semantic-error) {
+  margin-block: 1.5rem;
+  border: 1px solid color-mix(in srgb, hsl(var(--destructive)) 50%, hsl(var(--border)));
+  border-radius: 0.55rem;
+  background: color-mix(in srgb, hsl(var(--destructive)) 8%, transparent);
+  padding: 1rem;
+  color: hsl(var(--foreground));
+}
+
 .article-content :where(.callout hr) {
   margin-block: 1rem;
   border-top-color: color-mix(in srgb, hsl(var(--border)) 70%, transparent);
@@ -248,6 +290,33 @@
   margin-inline: 0;
 }
 
+.article-content :where(.semantic-interactive) {
+  margin-block: 2rem;
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.interactive-mount) {
+  min-height: 12rem;
+  border: 1px solid hsl(var(--border));
+  border-radius: 0.65rem;
+  background: color-mix(in srgb, hsl(var(--accent)) 20%, transparent);
+  padding: 1rem;
+}
+
+.article-content :where(.interactive-mount[data-interactive-state="missing-component"]) {
+  display: grid;
+  min-height: 8rem;
+  place-items: center;
+  color: hsl(var(--muted-foreground));
+  font-size: 0.95rem;
+  text-align: center;
+}
+
+.article-content :where(.interactive-fallback) {
+  margin: 0;
+  color: hsl(var(--muted-foreground));
+}
+
 .article-content :where(figcaption) {
   color: hsl(var(--muted-foreground));
   font-size: 0.92rem;
diff --git a/sites/reflections/astro.config.mjs b/sites/reflections/astro.config.mjs
index 17d8510..254caf9 100644
--- a/sites/reflections/astro.config.mjs
+++ b/sites/reflections/astro.config.mjs
@@ -12,6 +12,7 @@ import tailwindcss from "@tailwindcss/vite";
 import remarkCallouts from "./src/remark/callouts.mjs";
 import remarkCodeFenceLanguages from "./src/remark/code-fence-languages.mjs";
 import remarkInlineFootnotes from "./src/remark/inline-footnotes.mjs";
+import remarkSemanticBlocks from "./src/remark/semantic-blocks.mjs";
 import remarkTypography from "./src/remark/typography.mjs";
 import { ACTIVE_BLOG_SITE } from "./src/blog-sites.js";
 
@@ -19,6 +20,7 @@ const remarkPlugins = [
   remarkGfm,
   remarkInlineFootnotes,
   remarkCodeFenceLanguages,
+  remarkSemanticBlocks,
   remarkMath,
   remarkTypography,
   remarkCallouts,
diff --git a/sites/reflections/src/components/InteractiveRuntime.astro b/sites/reflections/src/components/InteractiveRuntime.astro
new file mode 100644
index 0000000..0ee92fc
--- /dev/null
+++ b/sites/reflections/src/components/InteractiveRuntime.astro
@@ -0,0 +1,3 @@
+<script>
+  import "@/interactives/runtime";
+</script>
diff --git a/sites/reflections/src/interactives/runtime.tsx b/sites/reflections/src/interactives/runtime.tsx
new file mode 100644
index 0000000..f6191e2
--- /dev/null
+++ b/sites/reflections/src/interactives/runtime.tsx
@@ -0,0 +1,77 @@
+import React from "react";
+import { createRoot } from "react-dom/client";
+
+type InteractiveProps = {
+  id: string;
+  label: string;
+  caption?: string;
+  description?: string;
+  fallback?: string;
+  attrs?: Record<string, string>;
+};
+
+type InteractiveModule = {
+  default: React.ComponentType<InteractiveProps>;
+};
+
+const modules = import.meta.glob<InteractiveModule>("./*/index.tsx");
+
+function readProps(element: HTMLElement): InteractiveProps {
+  const encoded = element.dataset.interactiveProps;
+  if (!encoded) {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+    };
+  }
+
+  try {
+    return JSON.parse(decodeURIComponent(encoded)) as InteractiveProps;
+  } catch {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+      fallback: element.textContent?.trim() ?? "",
+    };
+  }
+}
+
+async function mountInteractive(element: HTMLElement) {
+  const id = element.dataset.interactiveId;
+  if (!id || element.dataset.interactiveMounted) return;
+
+  const modulePath = `./${id}/index.tsx`;
+  const loader = modules[modulePath];
+  if (!loader) {
+    element.dataset.interactiveState = "missing-component";
+    return;
+  }
+
+  element.dataset.interactiveMounted = "true";
+  element.dataset.interactiveState = "loading";
+
+  try {
+    const props = readProps(element);
+    const { default: Component } = await loader();
+    element.replaceChildren();
+    createRoot(element).render(<Component {...props} />);
+    element.dataset.interactiveState = "ready";
+  } catch (error) {
+    element.dataset.interactiveState = "failed";
+    console.error(`Failed to mount interactive "${id}"`, error);
+  }
+}
+
+function mountAllInteractives() {
+  document
+    .querySelectorAll<HTMLElement>(".interactive-mount[data-interactive-id]")
+    .forEach((element) => {
+      void mountInteractive(element);
+    });
+}
+
+if (document.readyState === "loading") {
+  document.addEventListener("DOMContentLoaded", mountAllInteractives, { once: true });
+} else {
+  mountAllInteractives();
+}
diff --git a/sites/reflections/src/pages/[...slug].astro b/sites/reflections/src/pages/[...slug].astro
index 4b14673..2d2e6f2 100644
--- a/sites/reflections/src/pages/[...slug].astro
+++ b/sites/reflections/src/pages/[...slug].astro
@@ -1,6 +1,7 @@
 ---
 import { getCollection, render } from 'astro:content';
 import CoralComments from '@/components/CoralComments.astro';
+import InteractiveRuntime from '@/components/InteractiveRuntime.astro';
 import DefaultLayout from '@/layouts/DefaultLayout.astro';
 import { BlogPost } from '@/components/sections/blog-post';
 import { ACTIVE_BLOG_SITE } from '@/blog-sites.js';
@@ -26,5 +27,6 @@ const coralStoryURL = new URL(`/${postSlug}/`, ACTIVE_BLOG_SITE.url).toString();
 		<Content />
 	</BlogPost>
 
+	<InteractiveRuntime />
 	<CoralComments storyID={coralStoryID} storyURL={coralStoryURL} />
 </DefaultLayout>
diff --git a/sites/reflections/src/remark/semantic-blocks.mjs b/sites/reflections/src/remark/semantic-blocks.mjs
new file mode 100644
index 0000000..fe86b96
--- /dev/null
+++ b/sites/reflections/src/remark/semantic-blocks.mjs
@@ -0,0 +1,232 @@
+import { fromMarkdown } from "mdast-util-from-markdown";
+
+const ENV_TYPES = new Set([
+  "theorem",
+  "lemma",
+  "proposition",
+  "corollary",
+  "definition",
+  "example",
+  "remark",
+  "proof",
+]);
+
+const ENV_LABELS = {
+  theorem: "Theorem",
+  lemma: "Lemma",
+  proposition: "Proposition",
+  corollary: "Corollary",
+  definition: "Definition",
+  example: "Example",
+  remark: "Remark",
+  proof: "Proof",
+};
+
+function tokenizeInfo(info) {
+  return (
+    info.match(/[^\s=]+=(?:"[^"]*"|'[^']*'|[^\s]+)|"[^"]*"|'[^']*'|[^\s]+/g) ?? []
+  );
+}
+
+function stripQuotes(value) {
+  if (!value) return "";
+  const first = value[0];
+  const last = value[value.length - 1];
+  if ((first === '"' && last === '"') || (first === "'" && last === "'")) {
+    return value.slice(1, -1);
+  }
+  return value;
+}
+
+function parseFenceInfo(node) {
+  const lang = node.lang ?? "";
+  const meta = node.meta ?? "";
+  const raw = `${lang} ${meta}`.trim();
+  const attrs = {
+    classes: [],
+    id: "",
+    values: {},
+    raw,
+  };
+
+  if (!raw) return attrs;
+
+  let body = raw;
+  if (body.startsWith("{")) {
+    body = body.slice(1);
+    if (body.endsWith("}")) body = body.slice(0, -1);
+  } else if (lang) {
+    attrs.classes.push(lang);
+    body = meta;
+  }
+
+  for (let token of tokenizeInfo(body.trim())) {
+    if (token.endsWith("}") && !token.includes("=")) token = token.slice(0, -1);
+    if (!token) continue;
+
+    if (token.startsWith(".")) {
+      attrs.classes.push(token.slice(1));
+      continue;
+    }
+
+    if (token.startsWith("#")) {
+      attrs.id = token.slice(1);
+      continue;
+    }
+
+    const eq = token.indexOf("=");
+    if (eq > 0) {
+      const key = token.slice(0, eq);
+      const value = stripQuotes(token.slice(eq + 1));
+      if (key === "id") attrs.id = value;
+      attrs.values[key] = value;
+    }
+  }
+
+  return attrs;
+}
+
+function escapeHtml(value) {
+  return String(value)
+    .replaceAll("&", "&amp;")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;")
+    .replaceAll('"', "&quot;");
+}
+
+function attribute(value) {
+  return escapeHtml(value).replaceAll("\n", " ");
+}
+
+function encodedJson(value) {
+  return encodeURIComponent(JSON.stringify(value));
+}
+
+function firstClass(attrs, excluded) {
+  return attrs.classes.find((className) => !excluded.has(className));
+}
+
+function interactiveFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  if (!attrs.classes.includes("interactive")) return null;
+
+  const declaredId = attrs.id || attrs.values.component || attrs.values.name || "";
+  const componentId =
+    attrs.values.component ||
+    (declaredId.startsWith("int:") ? declaredId.slice("int:".length) : declaredId);
+  const label = attrs.values.label || (declaredId.startsWith("int:") ? declaredId : `int:${declaredId}`);
+  const caption = attrs.values.caption || attrs.values.title || "";
+  const description = node.value.trim();
+  const fallback = attrs.values.pdf || attrs.values.fallback || description || caption;
+
+  if (!componentId) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Interactive block missing an id. Add <code>#int:name</code> or <code>id="name"</code>.</aside>',
+    };
+  }
+
+  const props = {
+    id: componentId,
+    label,
+    caption,
+    description,
+    fallback,
+    attrs: attrs.values,
+  };
+
+  return {
+    type: "html",
+    value: [
+      `<figure class="semantic-interactive" id="${attribute(label)}" data-interactive-label="${attribute(label)}">`,
+      `<div class="interactive-mount" data-interactive-id="${attribute(componentId)}" data-interactive-props="${attribute(encodedJson(props))}">`,
+      fallback ? `<p class="interactive-fallback">${escapeHtml(fallback)}</p>` : "",
+      "</div>",
+      caption ? `<figcaption>${escapeHtml(caption)}</figcaption>` : "",
+      "</figure>",
+    ].join(""),
+  };
+}
+
+function envFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  const shorthandType = firstClass(attrs, new Set(["env", "latex-env"]));
+  const explicitType = attrs.values.type || shorthandType;
+  const type = ENV_TYPES.has(explicitType) ? explicitType : "";
+  const isEnv = attrs.classes.includes("env") || attrs.classes.includes("latex-env") || Boolean(type);
+
+  if (!isEnv) return null;
+
+  if (!type) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Environment block missing a type. Add <code>.theorem</code>, <code>.definition</code>, or <code>type="theorem"</code>.</aside>',
+    };
+  }
+
+  const title = attrs.values.title || attrs.values.name || "";
+  const label = attrs.id || attrs.values.label || "";
+  const renderMode = attrs.values.html || (type === "proof" ? "plain" : "callout");
+  const heading = title ? `${ENV_LABELS[type]} (${title})` : ENV_LABELS[type];
+  const parsed = fromMarkdown(node.value || "");
+  const className = [
+    "semantic-env",
+    `semantic-env-${type}`,
+    `semantic-env-${renderMode}`,
+    renderMode === "callout" ? "callout" : "",
+  ].filter(Boolean);
+
+  return {
+    type: "blockquote",
+    data: {
+      hName: "section",
+      hProperties: {
+        id: label || undefined,
+        className,
+        "data-env-type": type,
+        "data-env-title": title || undefined,
+        "data-env-render": renderMode,
+      },
+    },
+    children: [
+      {
+        type: "paragraph",
+        data: {
+          hProperties: {
+            className: ["semantic-env-heading"],
+          },
+        },
+        children: [
+          {
+            type: "strong",
+            children: [{ type: "text", value: heading }],
+          },
+        ],
+      },
+      ...parsed.children,
+    ],
+  };
+}
+
+function transformTree(parent) {
+  if (!parent?.children) return;
+
+  for (let index = 0; index < parent.children.length; index += 1) {
+    const child = parent.children[index];
+    if (child.type === "code") {
+      const replacement = interactiveFromCode(child) || envFromCode(child);
+      if (replacement) {
+        parent.children[index] = replacement;
+        continue;
+      }
+    }
+
+    transformTree(child);
+  }
+}
+
+export default function remarkSemanticBlocks() {
+  return (tree) => transformTree(tree);
+}
diff --git a/sites/reflections/src/styles/article.css b/sites/reflections/src/styles/article.css
index 798a3b9..e39264f 100644
--- a/sites/reflections/src/styles/article.css
+++ b/sites/reflections/src/styles/article.css
@@ -216,6 +216,48 @@
   margin-bottom: 0.35rem;
 }
 
+.article-content :where(.semantic-env) {
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.semantic-env-heading) {
+  margin: 0 0 0.75rem;
+  color: color-mix(in srgb, hsl(var(--primary)) 78%, hsl(var(--foreground)));
+  font-family: var(--font-mono);
+  font-size: 0.78rem;
+  font-weight: 700;
+  letter-spacing: 0.08em;
+  line-height: 1.3;
+  text-transform: uppercase;
+}
+
+.article-content :where(.semantic-env-heading strong) {
+  font-weight: inherit;
+}
+
+.article-content :where(.semantic-env-plain) {
+  margin-block: 1.6rem;
+  border-left: 3px solid hsl(var(--primary));
+  padding: 0.15rem 0 0.15rem 1rem;
+}
+
+.article-content :where(.semantic-env-plain > *:first-child) {
+  margin-top: 0;
+}
+
+.article-content :where(.semantic-env-plain > *:last-child) {
+  margin-bottom: 0;
+}
+
+.article-content :where(.semantic-error) {
+  margin-block: 1.5rem;
+  border: 1px solid color-mix(in srgb, hsl(var(--destructive)) 50%, hsl(var(--border)));
+  border-radius: 0.55rem;
+  background: color-mix(in srgb, hsl(var(--destructive)) 8%, transparent);
+  padding: 1rem;
+  color: hsl(var(--foreground));
+}
+
 .article-content :where(.callout hr) {
   margin-block: 1rem;
   border-top-color: color-mix(in srgb, hsl(var(--border)) 70%, transparent);
@@ -248,6 +290,33 @@
   margin-inline: 0;
 }
 
+.article-content :where(.semantic-interactive) {
+  margin-block: 2rem;
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.interactive-mount) {
+  min-height: 12rem;
+  border: 1px solid hsl(var(--border));
+  border-radius: 0.65rem;
+  background: color-mix(in srgb, hsl(var(--accent)) 20%, transparent);
+  padding: 1rem;
+}
+
+.article-content :where(.interactive-mount[data-interactive-state="missing-component"]) {
+  display: grid;
+  min-height: 8rem;
+  place-items: center;
+  color: hsl(var(--muted-foreground));
+  font-size: 0.95rem;
+  text-align: center;
+}
+
+.article-content :where(.interactive-fallback) {
+  margin: 0;
+  color: hsl(var(--muted-foreground));
+}
+
 .article-content :where(figcaption) {
   color: hsl(var(--muted-foreground));
   font-size: 0.92rem;
diff --git a/sites/research/astro.config.mjs b/sites/research/astro.config.mjs
index 17d8510..254caf9 100644
--- a/sites/research/astro.config.mjs
+++ b/sites/research/astro.config.mjs
@@ -12,6 +12,7 @@ import tailwindcss from "@tailwindcss/vite";
 import remarkCallouts from "./src/remark/callouts.mjs";
 import remarkCodeFenceLanguages from "./src/remark/code-fence-languages.mjs";
 import remarkInlineFootnotes from "./src/remark/inline-footnotes.mjs";
+import remarkSemanticBlocks from "./src/remark/semantic-blocks.mjs";
 import remarkTypography from "./src/remark/typography.mjs";
 import { ACTIVE_BLOG_SITE } from "./src/blog-sites.js";
 
@@ -19,6 +20,7 @@ const remarkPlugins = [
   remarkGfm,
   remarkInlineFootnotes,
   remarkCodeFenceLanguages,
+  remarkSemanticBlocks,
   remarkMath,
   remarkTypography,
   remarkCallouts,
diff --git a/sites/research/src/components/InteractiveRuntime.astro b/sites/research/src/components/InteractiveRuntime.astro
new file mode 100644
index 0000000..0ee92fc
--- /dev/null
+++ b/sites/research/src/components/InteractiveRuntime.astro
@@ -0,0 +1,3 @@
+<script>
+  import "@/interactives/runtime";
+</script>
diff --git a/sites/research/src/interactives/runtime.tsx b/sites/research/src/interactives/runtime.tsx
new file mode 100644
index 0000000..f6191e2
--- /dev/null
+++ b/sites/research/src/interactives/runtime.tsx
@@ -0,0 +1,77 @@
+import React from "react";
+import { createRoot } from "react-dom/client";
+
+type InteractiveProps = {
+  id: string;
+  label: string;
+  caption?: string;
+  description?: string;
+  fallback?: string;
+  attrs?: Record<string, string>;
+};
+
+type InteractiveModule = {
+  default: React.ComponentType<InteractiveProps>;
+};
+
+const modules = import.meta.glob<InteractiveModule>("./*/index.tsx");
+
+function readProps(element: HTMLElement): InteractiveProps {
+  const encoded = element.dataset.interactiveProps;
+  if (!encoded) {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+    };
+  }
+
+  try {
+    return JSON.parse(decodeURIComponent(encoded)) as InteractiveProps;
+  } catch {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+      fallback: element.textContent?.trim() ?? "",
+    };
+  }
+}
+
+async function mountInteractive(element: HTMLElement) {
+  const id = element.dataset.interactiveId;
+  if (!id || element.dataset.interactiveMounted) return;
+
+  const modulePath = `./${id}/index.tsx`;
+  const loader = modules[modulePath];
+  if (!loader) {
+    element.dataset.interactiveState = "missing-component";
+    return;
+  }
+
+  element.dataset.interactiveMounted = "true";
+  element.dataset.interactiveState = "loading";
+
+  try {
+    const props = readProps(element);
+    const { default: Component } = await loader();
+    element.replaceChildren();
+    createRoot(element).render(<Component {...props} />);
+    element.dataset.interactiveState = "ready";
+  } catch (error) {
+    element.dataset.interactiveState = "failed";
+    console.error(`Failed to mount interactive "${id}"`, error);
+  }
+}
+
+function mountAllInteractives() {
+  document
+    .querySelectorAll<HTMLElement>(".interactive-mount[data-interactive-id]")
+    .forEach((element) => {
+      void mountInteractive(element);
+    });
+}
+
+if (document.readyState === "loading") {
+  document.addEventListener("DOMContentLoaded", mountAllInteractives, { once: true });
+} else {
+  mountAllInteractives();
+}
diff --git a/sites/research/src/pages/[...slug].astro b/sites/research/src/pages/[...slug].astro
index 4b14673..2d2e6f2 100644
--- a/sites/research/src/pages/[...slug].astro
+++ b/sites/research/src/pages/[...slug].astro
@@ -1,6 +1,7 @@
 ---
 import { getCollection, render } from 'astro:content';
 import CoralComments from '@/components/CoralComments.astro';
+import InteractiveRuntime from '@/components/InteractiveRuntime.astro';
 import DefaultLayout from '@/layouts/DefaultLayout.astro';
 import { BlogPost } from '@/components/sections/blog-post';
 import { ACTIVE_BLOG_SITE } from '@/blog-sites.js';
@@ -26,5 +27,6 @@ const coralStoryURL = new URL(`/${postSlug}/`, ACTIVE_BLOG_SITE.url).toString();
 		<Content />
 	</BlogPost>
 
+	<InteractiveRuntime />
 	<CoralComments storyID={coralStoryID} storyURL={coralStoryURL} />
 </DefaultLayout>
diff --git a/sites/research/src/remark/semantic-blocks.mjs b/sites/research/src/remark/semantic-blocks.mjs
new file mode 100644
index 0000000..fe86b96
--- /dev/null
+++ b/sites/research/src/remark/semantic-blocks.mjs
@@ -0,0 +1,232 @@
+import { fromMarkdown } from "mdast-util-from-markdown";
+
+const ENV_TYPES = new Set([
+  "theorem",
+  "lemma",
+  "proposition",
+  "corollary",
+  "definition",
+  "example",
+  "remark",
+  "proof",
+]);
+
+const ENV_LABELS = {
+  theorem: "Theorem",
+  lemma: "Lemma",
+  proposition: "Proposition",
+  corollary: "Corollary",
+  definition: "Definition",
+  example: "Example",
+  remark: "Remark",
+  proof: "Proof",
+};
+
+function tokenizeInfo(info) {
+  return (
+    info.match(/[^\s=]+=(?:"[^"]*"|'[^']*'|[^\s]+)|"[^"]*"|'[^']*'|[^\s]+/g) ?? []
+  );
+}
+
+function stripQuotes(value) {
+  if (!value) return "";
+  const first = value[0];
+  const last = value[value.length - 1];
+  if ((first === '"' && last === '"') || (first === "'" && last === "'")) {
+    return value.slice(1, -1);
+  }
+  return value;
+}
+
+function parseFenceInfo(node) {
+  const lang = node.lang ?? "";
+  const meta = node.meta ?? "";
+  const raw = `${lang} ${meta}`.trim();
+  const attrs = {
+    classes: [],
+    id: "",
+    values: {},
+    raw,
+  };
+
+  if (!raw) return attrs;
+
+  let body = raw;
+  if (body.startsWith("{")) {
+    body = body.slice(1);
+    if (body.endsWith("}")) body = body.slice(0, -1);
+  } else if (lang) {
+    attrs.classes.push(lang);
+    body = meta;
+  }
+
+  for (let token of tokenizeInfo(body.trim())) {
+    if (token.endsWith("}") && !token.includes("=")) token = token.slice(0, -1);
+    if (!token) continue;
+
+    if (token.startsWith(".")) {
+      attrs.classes.push(token.slice(1));
+      continue;
+    }
+
+    if (token.startsWith("#")) {
+      attrs.id = token.slice(1);
+      continue;
+    }
+
+    const eq = token.indexOf("=");
+    if (eq > 0) {
+      const key = token.slice(0, eq);
+      const value = stripQuotes(token.slice(eq + 1));
+      if (key === "id") attrs.id = value;
+      attrs.values[key] = value;
+    }
+  }
+
+  return attrs;
+}
+
+function escapeHtml(value) {
+  return String(value)
+    .replaceAll("&", "&amp;")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;")
+    .replaceAll('"', "&quot;");
+}
+
+function attribute(value) {
+  return escapeHtml(value).replaceAll("\n", " ");
+}
+
+function encodedJson(value) {
+  return encodeURIComponent(JSON.stringify(value));
+}
+
+function firstClass(attrs, excluded) {
+  return attrs.classes.find((className) => !excluded.has(className));
+}
+
+function interactiveFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  if (!attrs.classes.includes("interactive")) return null;
+
+  const declaredId = attrs.id || attrs.values.component || attrs.values.name || "";
+  const componentId =
+    attrs.values.component ||
+    (declaredId.startsWith("int:") ? declaredId.slice("int:".length) : declaredId);
+  const label = attrs.values.label || (declaredId.startsWith("int:") ? declaredId : `int:${declaredId}`);
+  const caption = attrs.values.caption || attrs.values.title || "";
+  const description = node.value.trim();
+  const fallback = attrs.values.pdf || attrs.values.fallback || description || caption;
+
+  if (!componentId) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Interactive block missing an id. Add <code>#int:name</code> or <code>id="name"</code>.</aside>',
+    };
+  }
+
+  const props = {
+    id: componentId,
+    label,
+    caption,
+    description,
+    fallback,
+    attrs: attrs.values,
+  };
+
+  return {
+    type: "html",
+    value: [
+      `<figure class="semantic-interactive" id="${attribute(label)}" data-interactive-label="${attribute(label)}">`,
+      `<div class="interactive-mount" data-interactive-id="${attribute(componentId)}" data-interactive-props="${attribute(encodedJson(props))}">`,
+      fallback ? `<p class="interactive-fallback">${escapeHtml(fallback)}</p>` : "",
+      "</div>",
+      caption ? `<figcaption>${escapeHtml(caption)}</figcaption>` : "",
+      "</figure>",
+    ].join(""),
+  };
+}
+
+function envFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  const shorthandType = firstClass(attrs, new Set(["env", "latex-env"]));
+  const explicitType = attrs.values.type || shorthandType;
+  const type = ENV_TYPES.has(explicitType) ? explicitType : "";
+  const isEnv = attrs.classes.includes("env") || attrs.classes.includes("latex-env") || Boolean(type);
+
+  if (!isEnv) return null;
+
+  if (!type) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Environment block missing a type. Add <code>.theorem</code>, <code>.definition</code>, or <code>type="theorem"</code>.</aside>',
+    };
+  }
+
+  const title = attrs.values.title || attrs.values.name || "";
+  const label = attrs.id || attrs.values.label || "";
+  const renderMode = attrs.values.html || (type === "proof" ? "plain" : "callout");
+  const heading = title ? `${ENV_LABELS[type]} (${title})` : ENV_LABELS[type];
+  const parsed = fromMarkdown(node.value || "");
+  const className = [
+    "semantic-env",
+    `semantic-env-${type}`,
+    `semantic-env-${renderMode}`,
+    renderMode === "callout" ? "callout" : "",
+  ].filter(Boolean);
+
+  return {
+    type: "blockquote",
+    data: {
+      hName: "section",
+      hProperties: {
+        id: label || undefined,
+        className,
+        "data-env-type": type,
+        "data-env-title": title || undefined,
+        "data-env-render": renderMode,
+      },
+    },
+    children: [
+      {
+        type: "paragraph",
+        data: {
+          hProperties: {
+            className: ["semantic-env-heading"],
+          },
+        },
+        children: [
+          {
+            type: "strong",
+            children: [{ type: "text", value: heading }],
+          },
+        ],
+      },
+      ...parsed.children,
+    ],
+  };
+}
+
+function transformTree(parent) {
+  if (!parent?.children) return;
+
+  for (let index = 0; index < parent.children.length; index += 1) {
+    const child = parent.children[index];
+    if (child.type === "code") {
+      const replacement = interactiveFromCode(child) || envFromCode(child);
+      if (replacement) {
+        parent.children[index] = replacement;
+        continue;
+      }
+    }
+
+    transformTree(child);
+  }
+}
+
+export default function remarkSemanticBlocks() {
+  return (tree) => transformTree(tree);
+}
diff --git a/sites/research/src/styles/article.css b/sites/research/src/styles/article.css
index 798a3b9..e39264f 100644
--- a/sites/research/src/styles/article.css
+++ b/sites/research/src/styles/article.css
@@ -216,6 +216,48 @@
   margin-bottom: 0.35rem;
 }
 
+.article-content :where(.semantic-env) {
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.semantic-env-heading) {
+  margin: 0 0 0.75rem;
+  color: color-mix(in srgb, hsl(var(--primary)) 78%, hsl(var(--foreground)));
+  font-family: var(--font-mono);
+  font-size: 0.78rem;
+  font-weight: 700;
+  letter-spacing: 0.08em;
+  line-height: 1.3;
+  text-transform: uppercase;
+}
+
+.article-content :where(.semantic-env-heading strong) {
+  font-weight: inherit;
+}
+
+.article-content :where(.semantic-env-plain) {
+  margin-block: 1.6rem;
+  border-left: 3px solid hsl(var(--primary));
+  padding: 0.15rem 0 0.15rem 1rem;
+}
+
+.article-content :where(.semantic-env-plain > *:first-child) {
+  margin-top: 0;
+}
+
+.article-content :where(.semantic-env-plain > *:last-child) {
+  margin-bottom: 0;
+}
+
+.article-content :where(.semantic-error) {
+  margin-block: 1.5rem;
+  border: 1px solid color-mix(in srgb, hsl(var(--destructive)) 50%, hsl(var(--border)));
+  border-radius: 0.55rem;
+  background: color-mix(in srgb, hsl(var(--destructive)) 8%, transparent);
+  padding: 1rem;
+  color: hsl(var(--foreground));
+}
+
 .article-content :where(.callout hr) {
   margin-block: 1rem;
   border-top-color: color-mix(in srgb, hsl(var(--border)) 70%, transparent);
@@ -248,6 +290,33 @@
   margin-inline: 0;
 }
 
+.article-content :where(.semantic-interactive) {
+  margin-block: 2rem;
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.interactive-mount) {
+  min-height: 12rem;
+  border: 1px solid hsl(var(--border));
+  border-radius: 0.65rem;
+  background: color-mix(in srgb, hsl(var(--accent)) 20%, transparent);
+  padding: 1rem;
+}
+
+.article-content :where(.interactive-mount[data-interactive-state="missing-component"]) {
+  display: grid;
+  min-height: 8rem;
+  place-items: center;
+  color: hsl(var(--muted-foreground));
+  font-size: 0.95rem;
+  text-align: center;
+}
+
+.article-content :where(.interactive-fallback) {
+  margin: 0;
+  color: hsl(var(--muted-foreground));
+}
+
 .article-content :where(figcaption) {
   color: hsl(var(--muted-foreground));
   font-size: 0.92rem;
diff --git a/sites/reviews/astro.config.mjs b/sites/reviews/astro.config.mjs
index 17d8510..254caf9 100644
--- a/sites/reviews/astro.config.mjs
+++ b/sites/reviews/astro.config.mjs
@@ -12,6 +12,7 @@ import tailwindcss from "@tailwindcss/vite";
 import remarkCallouts from "./src/remark/callouts.mjs";
 import remarkCodeFenceLanguages from "./src/remark/code-fence-languages.mjs";
 import remarkInlineFootnotes from "./src/remark/inline-footnotes.mjs";
+import remarkSemanticBlocks from "./src/remark/semantic-blocks.mjs";
 import remarkTypography from "./src/remark/typography.mjs";
 import { ACTIVE_BLOG_SITE } from "./src/blog-sites.js";
 
@@ -19,6 +20,7 @@ const remarkPlugins = [
   remarkGfm,
   remarkInlineFootnotes,
   remarkCodeFenceLanguages,
+  remarkSemanticBlocks,
   remarkMath,
   remarkTypography,
   remarkCallouts,
diff --git a/sites/reviews/src/components/InteractiveRuntime.astro b/sites/reviews/src/components/InteractiveRuntime.astro
new file mode 100644
index 0000000..0ee92fc
--- /dev/null
+++ b/sites/reviews/src/components/InteractiveRuntime.astro
@@ -0,0 +1,3 @@
+<script>
+  import "@/interactives/runtime";
+</script>
diff --git a/sites/reviews/src/interactives/runtime.tsx b/sites/reviews/src/interactives/runtime.tsx
new file mode 100644
index 0000000..f6191e2
--- /dev/null
+++ b/sites/reviews/src/interactives/runtime.tsx
@@ -0,0 +1,77 @@
+import React from "react";
+import { createRoot } from "react-dom/client";
+
+type InteractiveProps = {
+  id: string;
+  label: string;
+  caption?: string;
+  description?: string;
+  fallback?: string;
+  attrs?: Record<string, string>;
+};
+
+type InteractiveModule = {
+  default: React.ComponentType<InteractiveProps>;
+};
+
+const modules = import.meta.glob<InteractiveModule>("./*/index.tsx");
+
+function readProps(element: HTMLElement): InteractiveProps {
+  const encoded = element.dataset.interactiveProps;
+  if (!encoded) {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+    };
+  }
+
+  try {
+    return JSON.parse(decodeURIComponent(encoded)) as InteractiveProps;
+  } catch {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+      fallback: element.textContent?.trim() ?? "",
+    };
+  }
+}
+
+async function mountInteractive(element: HTMLElement) {
+  const id = element.dataset.interactiveId;
+  if (!id || element.dataset.interactiveMounted) return;
+
+  const modulePath = `./${id}/index.tsx`;
+  const loader = modules[modulePath];
+  if (!loader) {
+    element.dataset.interactiveState = "missing-component";
+    return;
+  }
+
+  element.dataset.interactiveMounted = "true";
+  element.dataset.interactiveState = "loading";
+
+  try {
+    const props = readProps(element);
+    const { default: Component } = await loader();
+    element.replaceChildren();
+    createRoot(element).render(<Component {...props} />);
+    element.dataset.interactiveState = "ready";
+  } catch (error) {
+    element.dataset.interactiveState = "failed";
+    console.error(`Failed to mount interactive "${id}"`, error);
+  }
+}
+
+function mountAllInteractives() {
+  document
+    .querySelectorAll<HTMLElement>(".interactive-mount[data-interactive-id]")
+    .forEach((element) => {
+      void mountInteractive(element);
+    });
+}
+
+if (document.readyState === "loading") {
+  document.addEventListener("DOMContentLoaded", mountAllInteractives, { once: true });
+} else {
+  mountAllInteractives();
+}
diff --git a/sites/reviews/src/pages/[...slug].astro b/sites/reviews/src/pages/[...slug].astro
index 4b14673..2d2e6f2 100644
--- a/sites/reviews/src/pages/[...slug].astro
+++ b/sites/reviews/src/pages/[...slug].astro
@@ -1,6 +1,7 @@
 ---
 import { getCollection, render } from 'astro:content';
 import CoralComments from '@/components/CoralComments.astro';
+import InteractiveRuntime from '@/components/InteractiveRuntime.astro';
 import DefaultLayout from '@/layouts/DefaultLayout.astro';
 import { BlogPost } from '@/components/sections/blog-post';
 import { ACTIVE_BLOG_SITE } from '@/blog-sites.js';
@@ -26,5 +27,6 @@ const coralStoryURL = new URL(`/${postSlug}/`, ACTIVE_BLOG_SITE.url).toString();
 		<Content />
 	</BlogPost>
 
+	<InteractiveRuntime />
 	<CoralComments storyID={coralStoryID} storyURL={coralStoryURL} />
 </DefaultLayout>
diff --git a/sites/reviews/src/remark/semantic-blocks.mjs b/sites/reviews/src/remark/semantic-blocks.mjs
new file mode 100644
index 0000000..fe86b96
--- /dev/null
+++ b/sites/reviews/src/remark/semantic-blocks.mjs
@@ -0,0 +1,232 @@
+import { fromMarkdown } from "mdast-util-from-markdown";
+
+const ENV_TYPES = new Set([
+  "theorem",
+  "lemma",
+  "proposition",
+  "corollary",
+  "definition",
+  "example",
+  "remark",
+  "proof",
+]);
+
+const ENV_LABELS = {
+  theorem: "Theorem",
+  lemma: "Lemma",
+  proposition: "Proposition",
+  corollary: "Corollary",
+  definition: "Definition",
+  example: "Example",
+  remark: "Remark",
+  proof: "Proof",
+};
+
+function tokenizeInfo(info) {
+  return (
+    info.match(/[^\s=]+=(?:"[^"]*"|'[^']*'|[^\s]+)|"[^"]*"|'[^']*'|[^\s]+/g) ?? []
+  );
+}
+
+function stripQuotes(value) {
+  if (!value) return "";
+  const first = value[0];
+  const last = value[value.length - 1];
+  if ((first === '"' && last === '"') || (first === "'" && last === "'")) {
+    return value.slice(1, -1);
+  }
+  return value;
+}
+
+function parseFenceInfo(node) {
+  const lang = node.lang ?? "";
+  const meta = node.meta ?? "";
+  const raw = `${lang} ${meta}`.trim();
+  const attrs = {
+    classes: [],
+    id: "",
+    values: {},
+    raw,
+  };
+
+  if (!raw) return attrs;
+
+  let body = raw;
+  if (body.startsWith("{")) {
+    body = body.slice(1);
+    if (body.endsWith("}")) body = body.slice(0, -1);
+  } else if (lang) {
+    attrs.classes.push(lang);
+    body = meta;
+  }
+
+  for (let token of tokenizeInfo(body.trim())) {
+    if (token.endsWith("}") && !token.includes("=")) token = token.slice(0, -1);
+    if (!token) continue;
+
+    if (token.startsWith(".")) {
+      attrs.classes.push(token.slice(1));
+      continue;
+    }
+
+    if (token.startsWith("#")) {
+      attrs.id = token.slice(1);
+      continue;
+    }
+
+    const eq = token.indexOf("=");
+    if (eq > 0) {
+      const key = token.slice(0, eq);
+      const value = stripQuotes(token.slice(eq + 1));
+      if (key === "id") attrs.id = value;
+      attrs.values[key] = value;
+    }
+  }
+
+  return attrs;
+}
+
+function escapeHtml(value) {
+  return String(value)
+    .replaceAll("&", "&amp;")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;")
+    .replaceAll('"', "&quot;");
+}
+
+function attribute(value) {
+  return escapeHtml(value).replaceAll("\n", " ");
+}
+
+function encodedJson(value) {
+  return encodeURIComponent(JSON.stringify(value));
+}
+
+function firstClass(attrs, excluded) {
+  return attrs.classes.find((className) => !excluded.has(className));
+}
+
+function interactiveFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  if (!attrs.classes.includes("interactive")) return null;
+
+  const declaredId = attrs.id || attrs.values.component || attrs.values.name || "";
+  const componentId =
+    attrs.values.component ||
+    (declaredId.startsWith("int:") ? declaredId.slice("int:".length) : declaredId);
+  const label = attrs.values.label || (declaredId.startsWith("int:") ? declaredId : `int:${declaredId}`);
+  const caption = attrs.values.caption || attrs.values.title || "";
+  const description = node.value.trim();
+  const fallback = attrs.values.pdf || attrs.values.fallback || description || caption;
+
+  if (!componentId) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Interactive block missing an id. Add <code>#int:name</code> or <code>id="name"</code>.</aside>',
+    };
+  }
+
+  const props = {
+    id: componentId,
+    label,
+    caption,
+    description,
+    fallback,
+    attrs: attrs.values,
+  };
+
+  return {
+    type: "html",
+    value: [
+      `<figure class="semantic-interactive" id="${attribute(label)}" data-interactive-label="${attribute(label)}">`,
+      `<div class="interactive-mount" data-interactive-id="${attribute(componentId)}" data-interactive-props="${attribute(encodedJson(props))}">`,
+      fallback ? `<p class="interactive-fallback">${escapeHtml(fallback)}</p>` : "",
+      "</div>",
+      caption ? `<figcaption>${escapeHtml(caption)}</figcaption>` : "",
+      "</figure>",
+    ].join(""),
+  };
+}
+
+function envFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  const shorthandType = firstClass(attrs, new Set(["env", "latex-env"]));
+  const explicitType = attrs.values.type || shorthandType;
+  const type = ENV_TYPES.has(explicitType) ? explicitType : "";
+  const isEnv = attrs.classes.includes("env") || attrs.classes.includes("latex-env") || Boolean(type);
+
+  if (!isEnv) return null;
+
+  if (!type) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Environment block missing a type. Add <code>.theorem</code>, <code>.definition</code>, or <code>type="theorem"</code>.</aside>',
+    };
+  }
+
+  const title = attrs.values.title || attrs.values.name || "";
+  const label = attrs.id || attrs.values.label || "";
+  const renderMode = attrs.values.html || (type === "proof" ? "plain" : "callout");
+  const heading = title ? `${ENV_LABELS[type]} (${title})` : ENV_LABELS[type];
+  const parsed = fromMarkdown(node.value || "");
+  const className = [
+    "semantic-env",
+    `semantic-env-${type}`,
+    `semantic-env-${renderMode}`,
+    renderMode === "callout" ? "callout" : "",
+  ].filter(Boolean);
+
+  return {
+    type: "blockquote",
+    data: {
+      hName: "section",
+      hProperties: {
+        id: label || undefined,
+        className,
+        "data-env-type": type,
+        "data-env-title": title || undefined,
+        "data-env-render": renderMode,
+      },
+    },
+    children: [
+      {
+        type: "paragraph",
+        data: {
+          hProperties: {
+            className: ["semantic-env-heading"],
+          },
+        },
+        children: [
+          {
+            type: "strong",
+            children: [{ type: "text", value: heading }],
+          },
+        ],
+      },
+      ...parsed.children,
+    ],
+  };
+}
+
+function transformTree(parent) {
+  if (!parent?.children) return;
+
+  for (let index = 0; index < parent.children.length; index += 1) {
+    const child = parent.children[index];
+    if (child.type === "code") {
+      const replacement = interactiveFromCode(child) || envFromCode(child);
+      if (replacement) {
+        parent.children[index] = replacement;
+        continue;
+      }
+    }
+
+    transformTree(child);
+  }
+}
+
+export default function remarkSemanticBlocks() {
+  return (tree) => transformTree(tree);
+}
diff --git a/sites/reviews/src/styles/article.css b/sites/reviews/src/styles/article.css
index 798a3b9..e39264f 100644
--- a/sites/reviews/src/styles/article.css
+++ b/sites/reviews/src/styles/article.css
@@ -216,6 +216,48 @@
   margin-bottom: 0.35rem;
 }
 
+.article-content :where(.semantic-env) {
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.semantic-env-heading) {
+  margin: 0 0 0.75rem;
+  color: color-mix(in srgb, hsl(var(--primary)) 78%, hsl(var(--foreground)));
+  font-family: var(--font-mono);
+  font-size: 0.78rem;
+  font-weight: 700;
+  letter-spacing: 0.08em;
+  line-height: 1.3;
+  text-transform: uppercase;
+}
+
+.article-content :where(.semantic-env-heading strong) {
+  font-weight: inherit;
+}
+
+.article-content :where(.semantic-env-plain) {
+  margin-block: 1.6rem;
+  border-left: 3px solid hsl(var(--primary));
+  padding: 0.15rem 0 0.15rem 1rem;
+}
+
+.article-content :where(.semantic-env-plain > *:first-child) {
+  margin-top: 0;
+}
+
+.article-content :where(.semantic-env-plain > *:last-child) {
+  margin-bottom: 0;
+}
+
+.article-content :where(.semantic-error) {
+  margin-block: 1.5rem;
+  border: 1px solid color-mix(in srgb, hsl(var(--destructive)) 50%, hsl(var(--border)));
+  border-radius: 0.55rem;
+  background: color-mix(in srgb, hsl(var(--destructive)) 8%, transparent);
+  padding: 1rem;
+  color: hsl(var(--foreground));
+}
+
 .article-content :where(.callout hr) {
   margin-block: 1rem;
   border-top-color: color-mix(in srgb, hsl(var(--border)) 70%, transparent);
@@ -248,6 +290,33 @@
   margin-inline: 0;
 }
 
+.article-content :where(.semantic-interactive) {
+  margin-block: 2rem;
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.interactive-mount) {
+  min-height: 12rem;
+  border: 1px solid hsl(var(--border));
+  border-radius: 0.65rem;
+  background: color-mix(in srgb, hsl(var(--accent)) 20%, transparent);
+  padding: 1rem;
+}
+
+.article-content :where(.interactive-mount[data-interactive-state="missing-component"]) {
+  display: grid;
+  min-height: 8rem;
+  place-items: center;
+  color: hsl(var(--muted-foreground));
+  font-size: 0.95rem;
+  text-align: center;
+}
+
+.article-content :where(.interactive-fallback) {
+  margin: 0;
+  color: hsl(var(--muted-foreground));
+}
+
 .article-content :where(figcaption) {
   color: hsl(var(--muted-foreground));
   font-size: 0.92rem;
diff --git a/sites/vibes/astro.config.mjs b/sites/vibes/astro.config.mjs
index 17d8510..254caf9 100644
--- a/sites/vibes/astro.config.mjs
+++ b/sites/vibes/astro.config.mjs
@@ -12,6 +12,7 @@ import tailwindcss from "@tailwindcss/vite";
 import remarkCallouts from "./src/remark/callouts.mjs";
 import remarkCodeFenceLanguages from "./src/remark/code-fence-languages.mjs";
 import remarkInlineFootnotes from "./src/remark/inline-footnotes.mjs";
+import remarkSemanticBlocks from "./src/remark/semantic-blocks.mjs";
 import remarkTypography from "./src/remark/typography.mjs";
 import { ACTIVE_BLOG_SITE } from "./src/blog-sites.js";
 
@@ -19,6 +20,7 @@ const remarkPlugins = [
   remarkGfm,
   remarkInlineFootnotes,
   remarkCodeFenceLanguages,
+  remarkSemanticBlocks,
   remarkMath,
   remarkTypography,
   remarkCallouts,
diff --git a/sites/vibes/src/components/InteractiveRuntime.astro b/sites/vibes/src/components/InteractiveRuntime.astro
new file mode 100644
index 0000000..0ee92fc
--- /dev/null
+++ b/sites/vibes/src/components/InteractiveRuntime.astro
@@ -0,0 +1,3 @@
+<script>
+  import "@/interactives/runtime";
+</script>
diff --git a/sites/vibes/src/interactives/runtime.tsx b/sites/vibes/src/interactives/runtime.tsx
new file mode 100644
index 0000000..f6191e2
--- /dev/null
+++ b/sites/vibes/src/interactives/runtime.tsx
@@ -0,0 +1,77 @@
+import React from "react";
+import { createRoot } from "react-dom/client";
+
+type InteractiveProps = {
+  id: string;
+  label: string;
+  caption?: string;
+  description?: string;
+  fallback?: string;
+  attrs?: Record<string, string>;
+};
+
+type InteractiveModule = {
+  default: React.ComponentType<InteractiveProps>;
+};
+
+const modules = import.meta.glob<InteractiveModule>("./*/index.tsx");
+
+function readProps(element: HTMLElement): InteractiveProps {
+  const encoded = element.dataset.interactiveProps;
+  if (!encoded) {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+    };
+  }
+
+  try {
+    return JSON.parse(decodeURIComponent(encoded)) as InteractiveProps;
+  } catch {
+    return {
+      id: element.dataset.interactiveId ?? "",
+      label: "",
+      fallback: element.textContent?.trim() ?? "",
+    };
+  }
+}
+
+async function mountInteractive(element: HTMLElement) {
+  const id = element.dataset.interactiveId;
+  if (!id || element.dataset.interactiveMounted) return;
+
+  const modulePath = `./${id}/index.tsx`;
+  const loader = modules[modulePath];
+  if (!loader) {
+    element.dataset.interactiveState = "missing-component";
+    return;
+  }
+
+  element.dataset.interactiveMounted = "true";
+  element.dataset.interactiveState = "loading";
+
+  try {
+    const props = readProps(element);
+    const { default: Component } = await loader();
+    element.replaceChildren();
+    createRoot(element).render(<Component {...props} />);
+    element.dataset.interactiveState = "ready";
+  } catch (error) {
+    element.dataset.interactiveState = "failed";
+    console.error(`Failed to mount interactive "${id}"`, error);
+  }
+}
+
+function mountAllInteractives() {
+  document
+    .querySelectorAll<HTMLElement>(".interactive-mount[data-interactive-id]")
+    .forEach((element) => {
+      void mountInteractive(element);
+    });
+}
+
+if (document.readyState === "loading") {
+  document.addEventListener("DOMContentLoaded", mountAllInteractives, { once: true });
+} else {
+  mountAllInteractives();
+}
diff --git a/sites/vibes/src/pages/[...slug].astro b/sites/vibes/src/pages/[...slug].astro
index 4b14673..2d2e6f2 100644
--- a/sites/vibes/src/pages/[...slug].astro
+++ b/sites/vibes/src/pages/[...slug].astro
@@ -1,6 +1,7 @@
 ---
 import { getCollection, render } from 'astro:content';
 import CoralComments from '@/components/CoralComments.astro';
+import InteractiveRuntime from '@/components/InteractiveRuntime.astro';
 import DefaultLayout from '@/layouts/DefaultLayout.astro';
 import { BlogPost } from '@/components/sections/blog-post';
 import { ACTIVE_BLOG_SITE } from '@/blog-sites.js';
@@ -26,5 +27,6 @@ const coralStoryURL = new URL(`/${postSlug}/`, ACTIVE_BLOG_SITE.url).toString();
 		<Content />
 	</BlogPost>
 
+	<InteractiveRuntime />
 	<CoralComments storyID={coralStoryID} storyURL={coralStoryURL} />
 </DefaultLayout>
diff --git a/sites/vibes/src/remark/semantic-blocks.mjs b/sites/vibes/src/remark/semantic-blocks.mjs
new file mode 100644
index 0000000..fe86b96
--- /dev/null
+++ b/sites/vibes/src/remark/semantic-blocks.mjs
@@ -0,0 +1,232 @@
+import { fromMarkdown } from "mdast-util-from-markdown";
+
+const ENV_TYPES = new Set([
+  "theorem",
+  "lemma",
+  "proposition",
+  "corollary",
+  "definition",
+  "example",
+  "remark",
+  "proof",
+]);
+
+const ENV_LABELS = {
+  theorem: "Theorem",
+  lemma: "Lemma",
+  proposition: "Proposition",
+  corollary: "Corollary",
+  definition: "Definition",
+  example: "Example",
+  remark: "Remark",
+  proof: "Proof",
+};
+
+function tokenizeInfo(info) {
+  return (
+    info.match(/[^\s=]+=(?:"[^"]*"|'[^']*'|[^\s]+)|"[^"]*"|'[^']*'|[^\s]+/g) ?? []
+  );
+}
+
+function stripQuotes(value) {
+  if (!value) return "";
+  const first = value[0];
+  const last = value[value.length - 1];
+  if ((first === '"' && last === '"') || (first === "'" && last === "'")) {
+    return value.slice(1, -1);
+  }
+  return value;
+}
+
+function parseFenceInfo(node) {
+  const lang = node.lang ?? "";
+  const meta = node.meta ?? "";
+  const raw = `${lang} ${meta}`.trim();
+  const attrs = {
+    classes: [],
+    id: "",
+    values: {},
+    raw,
+  };
+
+  if (!raw) return attrs;
+
+  let body = raw;
+  if (body.startsWith("{")) {
+    body = body.slice(1);
+    if (body.endsWith("}")) body = body.slice(0, -1);
+  } else if (lang) {
+    attrs.classes.push(lang);
+    body = meta;
+  }
+
+  for (let token of tokenizeInfo(body.trim())) {
+    if (token.endsWith("}") && !token.includes("=")) token = token.slice(0, -1);
+    if (!token) continue;
+
+    if (token.startsWith(".")) {
+      attrs.classes.push(token.slice(1));
+      continue;
+    }
+
+    if (token.startsWith("#")) {
+      attrs.id = token.slice(1);
+      continue;
+    }
+
+    const eq = token.indexOf("=");
+    if (eq > 0) {
+      const key = token.slice(0, eq);
+      const value = stripQuotes(token.slice(eq + 1));
+      if (key === "id") attrs.id = value;
+      attrs.values[key] = value;
+    }
+  }
+
+  return attrs;
+}
+
+function escapeHtml(value) {
+  return String(value)
+    .replaceAll("&", "&amp;")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;")
+    .replaceAll('"', "&quot;");
+}
+
+function attribute(value) {
+  return escapeHtml(value).replaceAll("\n", " ");
+}
+
+function encodedJson(value) {
+  return encodeURIComponent(JSON.stringify(value));
+}
+
+function firstClass(attrs, excluded) {
+  return attrs.classes.find((className) => !excluded.has(className));
+}
+
+function interactiveFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  if (!attrs.classes.includes("interactive")) return null;
+
+  const declaredId = attrs.id || attrs.values.component || attrs.values.name || "";
+  const componentId =
+    attrs.values.component ||
+    (declaredId.startsWith("int:") ? declaredId.slice("int:".length) : declaredId);
+  const label = attrs.values.label || (declaredId.startsWith("int:") ? declaredId : `int:${declaredId}`);
+  const caption = attrs.values.caption || attrs.values.title || "";
+  const description = node.value.trim();
+  const fallback = attrs.values.pdf || attrs.values.fallback || description || caption;
+
+  if (!componentId) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Interactive block missing an id. Add <code>#int:name</code> or <code>id="name"</code>.</aside>',
+    };
+  }
+
+  const props = {
+    id: componentId,
+    label,
+    caption,
+    description,
+    fallback,
+    attrs: attrs.values,
+  };
+
+  return {
+    type: "html",
+    value: [
+      `<figure class="semantic-interactive" id="${attribute(label)}" data-interactive-label="${attribute(label)}">`,
+      `<div class="interactive-mount" data-interactive-id="${attribute(componentId)}" data-interactive-props="${attribute(encodedJson(props))}">`,
+      fallback ? `<p class="interactive-fallback">${escapeHtml(fallback)}</p>` : "",
+      "</div>",
+      caption ? `<figcaption>${escapeHtml(caption)}</figcaption>` : "",
+      "</figure>",
+    ].join(""),
+  };
+}
+
+function envFromCode(node) {
+  const attrs = parseFenceInfo(node);
+  const shorthandType = firstClass(attrs, new Set(["env", "latex-env"]));
+  const explicitType = attrs.values.type || shorthandType;
+  const type = ENV_TYPES.has(explicitType) ? explicitType : "";
+  const isEnv = attrs.classes.includes("env") || attrs.classes.includes("latex-env") || Boolean(type);
+
+  if (!isEnv) return null;
+
+  if (!type) {
+    return {
+      type: "html",
+      value:
+        '<aside class="semantic-error">Environment block missing a type. Add <code>.theorem</code>, <code>.definition</code>, or <code>type="theorem"</code>.</aside>',
+    };
+  }
+
+  const title = attrs.values.title || attrs.values.name || "";
+  const label = attrs.id || attrs.values.label || "";
+  const renderMode = attrs.values.html || (type === "proof" ? "plain" : "callout");
+  const heading = title ? `${ENV_LABELS[type]} (${title})` : ENV_LABELS[type];
+  const parsed = fromMarkdown(node.value || "");
+  const className = [
+    "semantic-env",
+    `semantic-env-${type}`,
+    `semantic-env-${renderMode}`,
+    renderMode === "callout" ? "callout" : "",
+  ].filter(Boolean);
+
+  return {
+    type: "blockquote",
+    data: {
+      hName: "section",
+      hProperties: {
+        id: label || undefined,
+        className,
+        "data-env-type": type,
+        "data-env-title": title || undefined,
+        "data-env-render": renderMode,
+      },
+    },
+    children: [
+      {
+        type: "paragraph",
+        data: {
+          hProperties: {
+            className: ["semantic-env-heading"],
+          },
+        },
+        children: [
+          {
+            type: "strong",
+            children: [{ type: "text", value: heading }],
+          },
+        ],
+      },
+      ...parsed.children,
+    ],
+  };
+}
+
+function transformTree(parent) {
+  if (!parent?.children) return;
+
+  for (let index = 0; index < parent.children.length; index += 1) {
+    const child = parent.children[index];
+    if (child.type === "code") {
+      const replacement = interactiveFromCode(child) || envFromCode(child);
+      if (replacement) {
+        parent.children[index] = replacement;
+        continue;
+      }
+    }
+
+    transformTree(child);
+  }
+}
+
+export default function remarkSemanticBlocks() {
+  return (tree) => transformTree(tree);
+}
diff --git a/sites/vibes/src/styles/article.css b/sites/vibes/src/styles/article.css
index 798a3b9..e39264f 100644
--- a/sites/vibes/src/styles/article.css
+++ b/sites/vibes/src/styles/article.css
@@ -216,6 +216,48 @@
   margin-bottom: 0.35rem;
 }
 
+.article-content :where(.semantic-env) {
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.semantic-env-heading) {
+  margin: 0 0 0.75rem;
+  color: color-mix(in srgb, hsl(var(--primary)) 78%, hsl(var(--foreground)));
+  font-family: var(--font-mono);
+  font-size: 0.78rem;
+  font-weight: 700;
+  letter-spacing: 0.08em;
+  line-height: 1.3;
+  text-transform: uppercase;
+}
+
+.article-content :where(.semantic-env-heading strong) {
+  font-weight: inherit;
+}
+
+.article-content :where(.semantic-env-plain) {
+  margin-block: 1.6rem;
+  border-left: 3px solid hsl(var(--primary));
+  padding: 0.15rem 0 0.15rem 1rem;
+}
+
+.article-content :where(.semantic-env-plain > *:first-child) {
+  margin-top: 0;
+}
+
+.article-content :where(.semantic-env-plain > *:last-child) {
+  margin-bottom: 0;
+}
+
+.article-content :where(.semantic-error) {
+  margin-block: 1.5rem;
+  border: 1px solid color-mix(in srgb, hsl(var(--destructive)) 50%, hsl(var(--border)));
+  border-radius: 0.55rem;
+  background: color-mix(in srgb, hsl(var(--destructive)) 8%, transparent);
+  padding: 1rem;
+  color: hsl(var(--foreground));
+}
+
 .article-content :where(.callout hr) {
   margin-block: 1rem;
   border-top-color: color-mix(in srgb, hsl(var(--border)) 70%, transparent);
@@ -248,6 +290,33 @@
   margin-inline: 0;
 }
 
+.article-content :where(.semantic-interactive) {
+  margin-block: 2rem;
+  scroll-margin-top: 5rem;
+}
+
+.article-content :where(.interactive-mount) {
+  min-height: 12rem;
+  border: 1px solid hsl(var(--border));
+  border-radius: 0.65rem;
+  background: color-mix(in srgb, hsl(var(--accent)) 20%, transparent);
+  padding: 1rem;
+}
+
+.article-content :where(.interactive-mount[data-interactive-state="missing-component"]) {
+  display: grid;
+  min-height: 8rem;
+  place-items: center;
+  color: hsl(var(--muted-foreground));
+  font-size: 0.95rem;
+  text-align: center;
+}
+
+.article-content :where(.interactive-fallback) {
+  margin: 0;
+  color: hsl(var(--muted-foreground));
+}
+
 .article-content :where(figcaption) {
   color: hsl(var(--muted-foreground));
   font-size: 0.92rem;