diff --git a/src/content/docs/en/guides/upgrade-to/v6.mdx b/src/content/docs/en/guides/upgrade-to/v6.mdx
index 59b159dff19e9..ca2021b56d1c9 100644
--- a/src/content/docs/en/guides/upgrade-to/v6.mdx
+++ b/src/content/docs/en/guides/upgrade-to/v6.mdx
@@ -547,6 +547,63 @@ export const server = {
 
 <ReadMore>Learn more about [rewrites](/en/guides/routing/#rewrites).</ReadMore>
 
+### Removed: exposed `astro:actions` internals
+
+<SourcePR number="14844" title="refactor: cleanup public actions API"/>
+
+In Astro 5.x, some internals were exported from `astro:actions` that were not meant to be exposed for public use.
+
+Astro 6.0 removes the following functions, classes and types that may no longer be used:
+
+- `ACTION_ERROR_CODES`
+- `ActionInputError`
+- `appendForwardSlash`
+- `astroCalledServerError`
+- `callSafely`
+- `deserializeActionResult`
+- `formDataToObject`
+- `getActionQueryString`
+- `serializeActionResult`
+- `type Actions`
+- `type ActionAccept`
+- `type AstroActionContext`
+- `type SerializedActionResult`
+
+#### What should I do?
+
+Replace all occurrences of the `serializeActionResult()` and `deserializeActionResult()` with `getActionContext()`:
+
+```ts title="src/middleware.ts" del={2} ins={3,6}
+import { defineMiddleware } from 'astro:middleware';
+import { serializeActionResult, deserializeActionResult } from 'astro:actions';
+import { getActionContext } from 'astro:actions';
+
+export const onRequest = defineMiddleware(async (context, next) => {
+  const { serializeActionResult, deserializeActionResult } = getActionContext(context);
+  // ...
+});
+```
+
+Remove any occurrences of the other removed exports:
+
+```ts del={1-13}
+import {
+  ACTION_ERROR_CODES,
+  ActionInputError,
+  appendForwardSlash,
+  astroCalledServerError,
+  callSafely,
+  formDataToObject,
+  getActionQueryString,
+  type Actions,
+  type ActionAccept,
+  type AstroActionContext,
+  type SerializedActionResult,
+} from 'astro:actions';
+```
+
+<ReadMore>Learn more about all utilities available in the [Actions API Reference](/en/reference/modules/astro-actions/).</ReadMore>
+
 ### Experimental Flags
 
 Experimental flags allow you to opt in to features while they are in early development. Astro may also use experimental flags to test breaking changes to default behavior. The following experimental flags have been removed in Astro 6.0 and are now stable, or the new default behavior.