diff --git a/test/edge-cases.js b/test/edge-cases.js
new file mode 100644
index 0000000..66f2e81
--- /dev/null
+++ b/test/edge-cases.js
@@ -0,0 +1,116 @@
+// Edge cases: math, special chars, Markdown HTML — non-destructive model.
+"use strict";
+
+const { JSDOM } = require("jsdom");
+const fs = require("fs");
+const path = require("path");
+const src = fs.readFileSync(path.join(__dirname, "../src/content.js"), "utf8");
+
+let passed = 0, failed = 0;
+function assert(label, cond, got) {
+  if (cond) { console.log("PASS " + label); passed++; }
+  else { console.log("FAIL " + label + (got !== undefined ? " — got: " + JSON.stringify(String(got).slice(0, 80)) : "")); failed++; }
+}
+
+function makeDOM(bodyHTML, settings) {
+  settings = Object.assign({ enabled: true, fixDirection: true, useFont: true, fixInputs: true, disabledSites: [] }, settings || {});
+  const dom = new JSDOM("<!DOCTYPE html><html><body>" + bodyHTML + "</body></html>",
+    { url: "https://example.com/", runScripts: "dangerously" });
+  const win = dom.window;
+  win.chrome = {
+    runtime: { getURL: (p) => "chrome-extension://test/" + p, lastError: null },
+    storage: { local: { get: (d, cb) => cb(settings), set: () => {} }, onChanged: { addListener: () => {} } }
+  };
+  const s = win.document.createElement("script");
+  s.textContent = src;
+  win.document.head.appendChild(s);
+  return dom;
+}
+
+console.log("=== Math Characters ===");
+{
+  const dom = makeDOM("<p id='t'>The formula is ∑(n=0..∞) = π × r² ± ε</p>");
+  const p = dom.window.document.getElementById("t");
+  assert("math-only: no dir", !p.hasAttribute("dir"), p.getAttribute("dir"));
+  assert("math-only: no font change", !p.style.fontFamily);
+  assert("math-only: text unchanged", p.textContent === "The formula is ∑(n=0..∞) = π × r² ± ε");
+}
+{
+  const dom = makeDOM("<p id='t'>مساحت دایره برابر است با π × r²</p>");
+  const p = dom.window.document.getElementById("t");
+  assert("persian+math: dir=rtl", p.getAttribute("dir") === "rtl", p.getAttribute("dir"));
+  assert("persian+math: Vazirmatn applied", p.style.fontFamily.toLowerCase().includes("vazirmatn"));
+  assert("persian+math: π preserved in text", p.textContent.includes("π"));
+}
+
+console.log("\n=== Special Characters ===");
+{
+  const dom = makeDOM("<p id='t'>Copyright © 2024 → All rights reserved ™</p>");
+  const p = dom.window.document.getElementById("t");
+  assert("special-only: no dir", !p.hasAttribute("dir"));
+  assert("special-only: no font change", !p.style.fontFamily);
+}
+{
+  const dom = makeDOM("<p id='t'>محصول جدید ما → قیمت: ۱۲۰ تومان ©</p>");
+  const p = dom.window.document.getElementById("t");
+  assert("persian+special: dir=rtl", p.getAttribute("dir") === "rtl", p.getAttribute("dir"));
+  assert("persian+special: © and → preserved", p.textContent.includes("©") && p.textContent.includes("→"));
+}
+
+console.log("\n=== ZWNJ (Persian word joiner) ===");
+{
+  const ZWNJ = "‌";
+  const dom = makeDOM("<p id='t'>می" + ZWNJ + "خواهم برگردم</p>");
+  const p = dom.window.document.getElementById("t");
+  // No wrapping → ZWNJ can never split a word now. Text is byte-identical.
+  assert("ZWNJ: text byte-identical (no splitting possible)", p.textContent === "می" + ZWNJ + "خواهم برگردم");
+  assert("ZWNJ: dir=rtl", p.getAttribute("dir") === "rtl");
+}
+
+console.log("\n=== Markdown-rendered HTML ===");
+{
+  const dom = makeDOM("<pre><code id='t'>const سلام = 'hello'; // فارسی</code></pre>");
+  const code = dom.window.document.getElementById("t");
+  assert("MD code block: no dir", !code.hasAttribute("dir"));
+  assert("MD code block: no font change", !code.style.fontFamily);
+}
+{
+  const dom = makeDOM("<p id='t'>Use <code id='c'>تابع()</code> to call it. این متن فارسی است.</p>");
+  const p = dom.window.document.getElementById("t");
+  const code = dom.window.document.getElementById("c");
+  assert("inline code: code element no font change", !code.style.fontFamily);
+  assert("inline code: English-leading mixed block dir=auto", p.getAttribute("dir") === "auto", p.getAttribute("dir"));
+}
+{
+  const dom = makeDOM("<p><strong id='t'>متن فارسی پررنگ</strong> and English text here</p>");
+  const strong = dom.window.document.getElementById("t");
+  const p = strong.parentElement;
+  assert("MD bold: font applied to <strong> (text's parent)", strong.style.fontFamily.toLowerCase().includes("vazirmatn"), strong.style.fontFamily);
+  assert("MD bold: dir on block <p>", p.hasAttribute("dir"), p.getAttribute("dir"));
+}
+{
+  const dom = makeDOM("<h1 id='t'>راهنمای استفاده</h1>");
+  const h1 = dom.window.document.getElementById("t");
+  assert("MD heading: dir=rtl", h1.getAttribute("dir") === "rtl", h1.getAttribute("dir"));
+  assert("MD heading: Vazirmatn applied", h1.style.fontFamily.toLowerCase().includes("vazirmatn"));
+}
+{
+  const dom = makeDOM("<blockquote><p id='t'>این یک نقل‌قول فارسی است</p></blockquote>");
+  const p = dom.window.document.getElementById("t");
+  assert("MD blockquote: dir=rtl", p.getAttribute("dir") === "rtl", p.getAttribute("dir"));
+}
+{
+  const dom = makeDOM('<svg xmlns="http://www.w3.org/2000/svg"><text id="t">متن فارسی</text></svg>');
+  const svgText = dom.window.document.getElementById("t");
+  if (svgText) assert("SVG text: no dir (skipped)", !svgText.hasAttribute("dir"));
+  else assert("SVG element found", false, "null");
+}
+{
+  const dom = makeDOM('<math xmlns="http://www.w3.org/1998/Math/MathML"><mi id="t">متغیر</mi></math>');
+  const mi = dom.window.document.getElementById("t");
+  if (mi) assert("MathML mi: no dir (skipped)", !mi.hasAttribute("dir"));
+  else assert("MathML element found (jsdom may lack support)", true);
+}
+
+console.log("\n" + passed + "/" + (passed + failed) + " passed" + (failed ? " — " + failed + " FAILED" : ""));
+process.exit(failed ? 1 : 0);