diff --git a/changelog.d/fixed-355-sync-sibling-docs-mdx-route.md b/changelog.d/fixed-355-sync-sibling-docs-mdx-route.md
new file mode 100644
index 0000000..f092ca0
--- /dev/null
+++ b/changelog.d/fixed-355-sync-sibling-docs-mdx-route.md
@@ -0,0 +1,4 @@
+- `scripts/sync-sibling-docs.ts` now strips `.mdx` as well as `.md` when
+  mapping a synced page to its `/docs/<project>/…` route, so links to pages
+  synced as MDX no longer resolve to `/docs/<project>/<page>.mdx`
+  (hivecommons/docs#355).
diff --git a/scripts/sync-sibling-docs.test.ts b/scripts/sync-sibling-docs.test.ts
index d7a1767..8afa9e9 100644
--- a/scripts/sync-sibling-docs.test.ts
+++ b/scripts/sync-sibling-docs.test.ts
@@ -116,6 +116,18 @@ describe("rewriteLinks", () => {
     );
   });
 
+  it("strips .mdx as well as .md from a synced target's route", () => {
+    const mdx: ProjectSync = {
+      ...spek,
+      files: [
+        { source: "docs/guide.md", target: "guide.mdx", required: false },
+      ],
+    };
+    expect(rewriteLinks("[g](docs/guide.md#top)", mdx)).toBe(
+      "[g](/docs/spektacular/guide#top)"
+    );
+  });
+
   it("matches synced pages case-insensitively", () => {
     expect(rewriteLinks("[kb](Docs/Knowledge-Base.MD)", spek)).toBe(
       "[kb](/docs/spektacular/knowledge-base)"
diff --git a/scripts/sync-sibling-docs.ts b/scripts/sync-sibling-docs.ts
index 1b53681..d36e95b 100644
--- a/scripts/sync-sibling-docs.ts
+++ b/scripts/sync-sibling-docs.ts
@@ -423,7 +423,7 @@ export function rewriteLinks(
   for (const s of p.files) {
     syncedRoutes.set(
       s.source.toLowerCase(),
-      `/docs/${p.project}/${s.target.replace(/\.md$/i, "")}`
+      `/docs/${p.project}/${s.target.replace(/\.mdx?$/i, "")}`
     );
   }
   const r = f ? fileRepo(p, f) : p;