diff --git a/app/packages/rehype-github-embed/index.ts b/app/packages/rehype-github-embed/index.ts
index aa080d7..62a167b 100644
--- a/app/packages/rehype-github-embed/index.ts
+++ b/app/packages/rehype-github-embed/index.ts
@@ -1,7 +1,14 @@
 import type { Element, Root } from "hast";
 import type { Plugin, Transformer } from "unified";
 import { visit } from "unist-util-visit";
-import { type Lines, buildRequestURL, createCodeBlock, extractCodeByLines, extractRepoDataFromURL } from "./utils";
+import {
+  type Lines,
+  buildRequestURL,
+  createCodeBlock,
+  createErrBlock,
+  extractCodeByLines,
+  extractRepoDataFromURL,
+} from "./utils";
 
 type Option = {
   githubPAT: string;
@@ -11,10 +18,6 @@ const rehypeGithubEmbed: Plugin<Option[], Root> = (options): Transformer<Root> =
   const { githubPAT } = options;
 
   const transform: Transformer<Root> = async (tree) => {
-    const regex = new RegExp(
-      /https:\/\/github\.com\/[a-zA-Z0-9._-]+\/[a-zA-Z0-9._-]+\/blob\/[a-zA-Z0-9._-]+\/?[^\s]*/g,
-    );
-
     const githubEmbedPromises: Promise<void>[] = [];
 
     const headers = {
@@ -24,11 +27,15 @@ const rehypeGithubEmbed: Plugin<Option[], Root> = (options): Transformer<Root> =
     };
 
     visit(tree, "element", (node, index, parent) => {
+      const regex = new RegExp(
+        /https:\/\/github\.com\/[a-zA-Z0-9._-]+\/[a-zA-Z0-9._-]+\/blob\/[a-zA-Z0-9._-]+\/?[^\s]*/g,
+      );
+
       if (
         node.tagName !== "a" ||
-        node.properties.href === undefined ||
-        typeof node.properties.href !== "string" ||
-        !regex.test(node.properties.href)
+        node.children.length === 0 ||
+        node.children[0].type !== "text" ||
+        !regex.test(node.children[0].value)
       ) {
         return;
       }
@@ -37,39 +44,69 @@ const rehypeGithubEmbed: Plugin<Option[], Root> = (options): Transformer<Root> =
         return;
       }
 
+      if (parent.type === "mdxJsxFlowElement" || parent.type === "mdxJsxTextElement") {
+        return;
+      }
+
       type Props = {
-        node: Element;
+        parent: Root | Element;
         href: string;
+        owner: string;
         repoName: string;
         ref: string;
         path: string;
         lines?: Lines;
       };
 
-      const githubEmbedPromise = async ({ repoName, ref, href, path, lines }: Props): Promise<void> => {
-        const requestUrl = buildRequestURL(repoName, ref, path);
+      const githubEmbedPromise = async ({ parent, owner, repoName, ref, href, path, lines }: Props): Promise<void> => {
+        const requestUrl = buildRequestURL(owner, repoName, ref, path);
+
         try {
-          const response = await fetch(requestUrl, { headers });
+          const response = await fetch(requestUrl, {
+            headers,
+          });
           if (!response.ok) {
+            if (response.status === 404) {
+              const element = createErrBlock("404 Not Found");
+              parent.children[index] = element;
+              return;
+            }
+
             throw new Error(`Failed to fetch code from GitHub: ${response.status}`);
           }
-          const content = (await response.json()) as { content: string };
+          const content = (await response.json()) as {
+            content: string;
+          };
           const codeBase64 = content.content;
           const code = extractCodeByLines(Buffer.from(codeBase64, "base64").toString("utf-8"), lines);
 
-          const title = `${repoName}/${path}${lines ? `#L${lines.startLine}-L${lines.endLine}` : ""}`;
-          const codeBlockElement = createCodeBlock(title, href, code);
+          const title = `${repoName}/${path}${
+            lines
+              ? `#${lines.startLine && lines.endLine ? `L${lines.startLine}-L${lines.endLine}` : `L${lines.startLine}`}`
+              : ""
+          }`;
 
-          parent.children[index] = codeBlockElement;
+          const element = createCodeBlock(title, href, code);
+          parent.children[index] = element;
         } catch (error) {
           throw new Error("Failed to fetch code from GitHub", { cause: error });
         }
       };
 
-      const nodeHref = node.properties.href;
-      const { repoName, ref, path, lines } = extractRepoDataFromURL(nodeHref);
-
-      githubEmbedPromises.push(githubEmbedPromise({ node, repoName, href: nodeHref, ref, path, lines }));
+      const nodeHref = node.children[0].value;
+      const { repoName, owner, ref, path, lines } = extractRepoDataFromURL(nodeHref);
+
+      githubEmbedPromises.push(
+        githubEmbedPromise({
+          parent,
+          repoName,
+          owner,
+          href: nodeHref,
+          ref,
+          path,
+          lines,
+        }),
+      );
     });
 
     await Promise.all(githubEmbedPromises);
diff --git a/app/packages/rehype-github-embed/utils.ts b/app/packages/rehype-github-embed/utils.ts
index a35c65e..704ce5f 100644
--- a/app/packages/rehype-github-embed/utils.ts
+++ b/app/packages/rehype-github-embed/utils.ts
@@ -1,61 +1,66 @@
 import { h } from "hastscript";
 
-const extractRepoName = (urlParts: string[]): string => {
-  return urlParts.slice(0, 2).join("/");
+const extractOwner = (pathname: string): string => {
+  const pathnameParts = pathname.split("/");
+  return pathnameParts[1];
 };
 
-const extractFilePath = (urlParts: string[]): string => {
-  const result = urlParts.slice(4).join("/");
-  const hashIndex = result.indexOf("#");
-  if (hashIndex === -1) {
-    return result;
-  }
-  return result.slice(0, hashIndex);
+const extractRepoName = (pathname: string): string => {
+  const pathnameParts = pathname.split("/");
+  return pathnameParts[2];
+};
+
+const extractFilePath = (pathname: string): string => {
+  const pathnameParts = pathname.split("/");
+  return pathnameParts.slice(5).join("/");
 };
 
-const extractRef = (urlParts: string[]): string => {
-  return urlParts[3];
+const extractRef = (pathname: string): string => {
+  const pathnameParts = pathname.split("/");
+  return pathnameParts[4];
 };
 
 export type Lines = {
   startLine: number;
-  endLine: number;
+  endLine?: number;
 };
 
-const extractLines = (urlParts: string[]): Lines | undefined => {
-  const result = urlParts.slice(4).join("/");
-  const hashIndex = result.indexOf("#");
-  if (hashIndex === -1) {
-    return;
-  }
-  const hash = result.slice(hashIndex + 1);
-  const numbers = hash.match(/\d+/g);
-  if (!numbers) return;
-  return {
-    startLine: Number.parseInt(numbers[0]),
-    endLine: Number.parseInt(numbers[1]),
-  };
+const extractLines = (hash: string): Lines | undefined => {
+  const matches = hash.match(/\d+/g);
+  if (!matches) return;
+
+  return matches[0] && matches[1]
+    ? {
+        startLine: Number.parseInt(matches[0]),
+        endLine: Number.parseInt(matches[1]),
+      }
+    : { startLine: Number.parseInt(matches[0]) };
 };
 
 const extractRepoDataFromURL = (url: string) => {
-  const base = url.replace("https://github.com/", "");
-  const urlParts = base.split("/");
+  const base = new URL(url);
   return {
-    repoName: extractRepoName(urlParts),
-    ref: extractRef(urlParts),
-    path: extractFilePath(urlParts),
-    lines: extractLines(urlParts),
+    repoName: extractRepoName(base.pathname),
+    owner: extractOwner(base.pathname),
+    ref: extractRef(base.pathname),
+    path: extractFilePath(base.pathname),
+    lines: extractLines(base.hash),
   };
 };
 
 const extractCodeByLines = (code: string, lines: Lines | undefined): string => {
   if (!lines) return code;
   const codeLines = code.split("\n");
-  return codeLines.slice(lines.startLine - 1, lines.endLine).join("\n");
+
+  if (lines.startLine && lines.endLine) {
+    return codeLines.slice(lines.startLine - 1, lines.endLine).join("\n");
+  }
+
+  return codeLines[lines.startLine - 1];
 };
 
-const buildRequestURL = (repo: string, ref: string, path: string): string => {
-  return `https://api.github.com/repos/${repo}/contents/${path}?ref=${ref}`;
+const buildRequestURL = (owner: string, repoName: string, ref: string, path: string): string => {
+  return `https://api.github.com/repos/${owner}/${repoName}/contents/${path}?ref=${ref}`;
 };
 
 const createCodeBlock = (title: string, href: string, code: string) => {
@@ -67,4 +72,8 @@ const createCodeBlock = (title: string, href: string, code: string) => {
   ]);
 };
 
-export { extractRepoDataFromURL, buildRequestURL, extractCodeByLines, createCodeBlock };
+const createErrBlock = (message: string) => {
+  return h("div", [h("span", [h(null, [{ type: "text", value: message }])])]);
+};
+
+export { extractRepoDataFromURL, buildRequestURL, extractCodeByLines, createCodeBlock, createErrBlock };