Document parameterized markdown snippets feature

fern/products/docs/pages/changelog/2025-11-08.mdx

@@ -0,0 +1,23 @@
+## Parameterized markdown snippets
+
+Reusable markdown snippets can now accept arbitrary parameters that can be used as variables in the snippet. This enables flexible, reusable content templates.
+
+Create a snippet with parameter placeholders using curly braces:
+
+```mdx fern/snippets/feature.mdx
+This feature is only available on the {plan} plan.
+```
+
+Pass parameters when including the snippet:
+
+```mdx page.mdx
+<Markdown src="/snippets/feature.mdx" plan="pro" />
+```
+
+This renders as:
+
+```
+This feature is only available on the pro plan.
+```
+
+Learn more about [reusable markdown snippets](/learn/docs/content/markdown#reusable-markdown-snippets).

fern/products/docs/pages/component-library/writing-content/markdown.mdx

@@ -51,6 +51,70 @@ The value for `page` is used as the content of the top `<h1>` element of this pa
 
 Fern has a built-in component library you can use in Markdown. [Explore the components.](/learn/docs/content/components/overview)
 
+## Reusable markdown snippets
+
+You can create reusable markdown snippets and include them in multiple pages using the `<Markdown>` component. This is useful for content that appears in multiple places, such as warnings, common instructions, or version numbers.
+
+### Basic usage
+
+Create a snippet file in your `fern/snippets/` folder:
+
+<CodeBlock title='fern/snippets/common-warning.mdx'>
+```mdx
+<Warning>
+This feature is in beta and may change in future releases.
+</Warning>
+```
+</CodeBlock>
+
+Then include it in any page using the `<Markdown>` component:
+
+<CodeBlock title='page.mdx'>
+```mdx
+<Markdown src="/snippets/common-warning.mdx" />
+```
+</CodeBlock>
+
+### Parameterized snippets
+
+Snippets can accept arbitrary parameters that can be used as variables within the snippet content. This allows you to create flexible, reusable content templates.
+
+Create a snippet with parameter placeholders using curly braces:
+
+<CodeBlock title='fern/snippets/feature.mdx'>
+```mdx
+This feature is only available on the {plan} plan.
+```
+</CodeBlock>
+
+Pass parameters when including the snippet:
+
+<CodeBlock title='page.mdx'>
+```mdx
+<Markdown src="/snippets/feature.mdx" plan="pro" />
+```
+</CodeBlock>
+
+This renders as:
+
+```
+This feature is only available on the pro plan.
+```
+
+You can use multiple parameters in a single snippet:
+
+<CodeBlock title='fern/snippets/sdk-install.mdx'>
+```mdx
+Install the {language} SDK version {version} using {packageManager}.
+```
+</CodeBlock>
+
+<CodeBlock title='page.mdx'>
+```mdx
+<Markdown src="/snippets/sdk-install.mdx" language="TypeScript" version="3.28.1" packageManager="npm" />
+```
+</CodeBlock>
+
 ## Links in Markdown
 
 ### Link target