Redirect Get Feedback to the canonical subscript.to origin

app/src/App.tsx

@@ -29,6 +29,7 @@ import {
   type ScreenplayParagraph,
   serializeFdx,
 } from "./lib/fdx";
+import { feedbackRedirectUrl } from "./lib/feedback";
 import { type DeviceIdentity, loadIdentity, renameIdentity } from "./lib/identity";
 import { paginateScreenplay } from "./lib/pagination";
 import { loadPanelPreferences, savePanelPreferences } from "./lib/panel_preferences";
@@ -528,7 +529,9 @@ function App({ config: configOverrides }: { config?: Partial<WriteConfig> } = {}
       });
       const result = (await response.json()) as { redirect_url?: string; error?: string };
       if (!response.ok || !result.redirect_url) throw new Error(result.error || "Upload failed");
-      window.location.assign(result.redirect_url);
+      window.location.assign(
+        feedbackRedirectUrl(result.redirect_url, config.homepage, window.location.origin),
+      );
     } catch {
       setFeedbackStatus("error");
     }

app/src/lib/feedback.test.ts

@@ -0,0 +1,47 @@
+import { describe, expect, it } from "vitest";
+import { feedbackRedirectUrl } from "./feedback";
+
+describe("feedback redirect", () => {
+  it("resolves relative redirects against the Subscript homepage", () => {
+    expect(
+      feedbackRedirectUrl(
+        "/scripts/42/feedback?x=1",
+        "https://subscript.to",
+        "https://write.subscript.to",
+      ),
+    ).toBe("https://subscript.to/scripts/42/feedback?x=1");
+  });
+
+  it("moves redirects built from the editor host onto the Subscript homepage", () => {
+    expect(
+      feedbackRedirectUrl(
+        "https://write.subscript.to/scripts/42/feedback#top",
+        "https://subscript.to",
+        "https://write.subscript.to",
+      ),
+    ).toBe("https://subscript.to/scripts/42/feedback#top");
+  });
+
+  it("keeps redirects that already point at another origin", () => {
+    expect(
+      feedbackRedirectUrl(
+        "https://subscript.to/scripts/42",
+        "https://subscript.to",
+        "https://write.subscript.to",
+      ),
+    ).toBe("https://subscript.to/scripts/42");
+    expect(
+      feedbackRedirectUrl(
+        "https://auth.example.com/login",
+        "https://subscript.to",
+        "https://write.subscript.to",
+      ),
+    ).toBe("https://auth.example.com/login");
+  });
+
+  it("leaves redirects alone when the editor is embedded on the homepage", () => {
+    expect(feedbackRedirectUrl("/scripts/42", "https://subscript.to", "https://subscript.to")).toBe(
+      "https://subscript.to/scripts/42",
+    );
+  });
+});

app/src/lib/feedback.ts

@@ -0,0 +1,15 @@
+// Get Feedback must land on the canonical Subscript site, where SSO works,
+// even when the editor is served from another host such as write.subscript.to.
+export const feedbackRedirectUrl = (
+  redirectUrl: string,
+  homepage: string,
+  currentOrigin: string,
+): string => {
+  const canonical = new URL(homepage);
+  const target = new URL(redirectUrl, canonical);
+  if (target.origin === currentOrigin && currentOrigin !== canonical.origin) {
+    target.protocol = canonical.protocol;
+    target.host = canonical.host;
+  }
+  return target.toString();
+};