diff --git a/web/app/components/base/markdown/index.tsx b/web/app/components/base/markdown/index.tsx
index 0e0dc41cf..1e50e6745 100644
--- a/web/app/components/base/markdown/index.tsx
+++ b/web/app/components/base/markdown/index.tsx
@@ -7,7 +7,7 @@ import RemarkGfm from 'remark-gfm'
 import RehypeRaw from 'rehype-raw'
 import { flow } from 'lodash-es'
 import cn from '@/utils/classnames'
-import { preprocessLaTeX, preprocessThinkTag } from './markdown-utils'
+import { customUrlTransform, preprocessLaTeX, preprocessThinkTag } from './markdown-utils'
 import {
   AudioBlock,
   CodeBlock,
@@ -65,6 +65,7 @@ export function Markdown(props: { content: string; className?: string; customDis
             }
           },
         ]}
+        urlTransform={customUrlTransform}
         disallowedElements={['iframe', 'head', 'html', 'meta', 'link', 'style', 'body', ...(props.customDisallowedElements || [])]}
         components={{
           code: CodeBlock,
diff --git a/web/app/components/base/markdown/markdown-utils.ts b/web/app/components/base/markdown/markdown-utils.ts
index d77b2ddcc..0aa385a1d 100644
--- a/web/app/components/base/markdown/markdown-utils.ts
+++ b/web/app/components/base/markdown/markdown-utils.ts
@@ -36,3 +36,52 @@ export const preprocessThinkTag = (content: string) => {
     (str: string) => str.replace(/(<\/details>)(?![^\S\r\n]*[\r\n])(?![^\S\r\n]*$)/g, '$1\n'),
   ])(content)
 }
+
+/**
+ * Transforms a URI for use in react-markdown, ensuring security and compatibility.
+ * This function is designed to work with react-markdown v9+ which has stricter
+ * default URL handling.
+ *
+ * Behavior:
+ * 1. Always allows the custom 'abbr:' protocol.
+ * 2. Always allows page-local fragments (e.g., "#some-id").
+ * 3. Always allows protocol-relative URLs (e.g., "//example.com/path").
+ * 4. Always allows purely relative paths (e.g., "path/to/file", "/abs/path").
+ * 5. Allows absolute URLs if their scheme is in a permitted list (case-insensitive):
+ *    'http:', 'https:', 'mailto:', 'xmpp:', 'irc:', 'ircs:'.
+ * 6. Intelligently distinguishes colons used for schemes from colons within
+ *    paths, query parameters, or fragments of relative-like URLs.
+ * 7. Returns the original URI if allowed, otherwise returns `undefined` to
+ *    signal that the URI should be removed/disallowed by react-markdown.
+ */
+export const customUrlTransform = (uri: string): string | undefined => {
+  const PERMITTED_SCHEME_REGEX = /^(https?|ircs?|mailto|xmpp|abbr):$/i
+
+  if (uri.startsWith('#'))
+    return uri
+
+  if (uri.startsWith('//'))
+    return uri
+
+  const colonIndex = uri.indexOf(':')
+
+  if (colonIndex === -1)
+    return uri
+
+  const slashIndex = uri.indexOf('/')
+  const questionMarkIndex = uri.indexOf('?')
+  const hashIndex = uri.indexOf('#')
+
+  if (
+    (slashIndex !== -1 && colonIndex > slashIndex)
+    || (questionMarkIndex !== -1 && colonIndex > questionMarkIndex)
+    || (hashIndex !== -1 && colonIndex > hashIndex)
+  )
+    return uri
+
+  const scheme = uri.substring(0, colonIndex + 1).toLowerCase()
+  if (PERMITTED_SCHEME_REGEX.test(scheme))
+    return uri
+
+  return undefined
+}