diff --git a/apps/server/src/http.test.ts b/apps/server/src/http.test.ts
index ef75d9446158..4f6b6e3d2535 100644
--- a/apps/server/src/http.test.ts
+++ b/apps/server/src/http.test.ts
@@ -382,14 +382,16 @@ describe("assetResponseHeaders", () => {
       assetResponseHeaders("/attachments/upload.bin", { mimeType: "text/html" }),
     ).toMatchObject({
       "Content-Type": "text/html; charset=utf-8",
-      "Content-Security-Policy": "sandbox allow-scripts allow-forms allow-popups allow-modals",
+      "Content-Security-Policy":
+        "sandbox allow-scripts allow-forms allow-popups allow-modals allow-downloads",
     });
   });
   it("serves HTML assets as utf-8 inside a sandboxed origin", () => {
     for (const path of ["/workspace/page.html", "/workspace/PAGE.HTM", "/tmp/report.html"]) {
       expect(assetResponseHeaders(path)).toMatchObject({
         "Content-Type": "text/html; charset=utf-8",
-        "Content-Security-Policy": "sandbox allow-scripts allow-forms allow-popups allow-modals",
+        "Content-Security-Policy":
+          "sandbox allow-scripts allow-forms allow-popups allow-modals allow-downloads",
       });
     }
   });
diff --git a/apps/server/src/http.ts b/apps/server/src/http.ts
index 30b368e62167..7d839e7cae89 100644
--- a/apps/server/src/http.ts
+++ b/apps/server/src/http.ts
@@ -55,7 +55,9 @@ const SVG_CONTENT_SECURITY_POLICY = "default-src 'none'; style-src 'unsafe-inlin
 // HTML previews are agent output, not the app. The sandbox gives the document an
 // opaque origin: scripts run, but same-origin cookies, storage, and API calls are
 // out of reach. Relative sibling assets still load through their signed URLs.
-const HTML_CONTENT_SECURITY_POLICY = "sandbox allow-scripts allow-forms allow-popups allow-modals";
+// Downloads stay allowed, so a page's own download button can save a file.
+const HTML_CONTENT_SECURITY_POLICY =
+  "sandbox allow-scripts allow-forms allow-popups allow-modals allow-downloads";
 
 // Types a browser may render as a document if a proxy strips the disposition
 // header. Downloads of these fall back to octet-stream.
diff --git a/apps/web/src/components/files/BrowserDocumentFrame.tsx b/apps/web/src/components/files/BrowserDocumentFrame.tsx
index 0be9c724ca00..cc4b1796a936 100644
--- a/apps/web/src/components/files/BrowserDocumentFrame.tsx
+++ b/apps/web/src/components/files/BrowserDocumentFrame.tsx
@@ -34,7 +34,7 @@ export function BrowserDocumentFrame(props: {
       src={props.src}
       title={props.title}
       className={className}
-      sandbox="allow-scripts allow-forms allow-popups allow-modals"
+      sandbox="allow-scripts allow-forms allow-popups allow-modals allow-downloads"
     />
   );
 }