carry the invite's device name in the link so the phone can prefill it

src/servers/sidecar/headscale/invites.ts

@@ -95,6 +95,25 @@ async function relay(res: Response | string, wrap: (body: Record<string, unknown
   return Response.json(wrap(body));
 }
 
+/**
+ * Carry the admin's device name in the link's fragment, as `n=<percent-encoded>`.
+ *
+ * The companion already knows the name — it stores the note and hands it back as `suggestedHostname` on
+ * claim — but a claim only happens when the person taps Join, which is one step AFTER the screen that asks
+ * them to name the device. So the name has to arrive with the link if the field is to be prefilled, and the
+ * link is the last thing that passes through here.
+ *
+ * Safe at every hop: the fragment is never sent to a server, the companion's /join page copies it verbatim
+ * into the `officer-offscale://` deep link, and a build of the app that predates this ignores an unknown
+ * parameter and still gets the name from `suggestedHostname` at claim time. Percent-encoded rather than
+ * base64url (which `s` uses) because the app's fragment parser already decodeURIComponent()s every value,
+ * and because base64url of a non-ASCII name would decode to mojibake on Hermes.
+ */
+function withNameHint(url: unknown, name: string | undefined): unknown {
+  if (typeof url !== 'string' || !name || !url.includes('#')) return url;
+  return `${url}&n=${encodeURIComponent(name)}`;
+}
+
 /**
  * `POST /_officer/enroll/invites` — mint an invite. The response carries the link, and only this once.
  *
@@ -112,7 +131,7 @@ async function create(creds: HeadscaleServerCredentials, ctx: OfficerContext): P
     const raw = body.invite ?? body;
     const invite = raw && typeof raw === 'object' ? (raw as Record<string, unknown>) : {};
     const { deepLink: _deepLink, ...rest } = invite;
-    return { available: true, invite: rest };
+    return { available: true, invite: { ...rest, url: withNameHint(rest.url, input.note) } };
   });
 }