diff --git a/devlog/_plan/260905_admin_token_local_ux/assets/admin-token-dialog-before-after.png b/devlog/_plan/260905_admin_token_local_ux/assets/admin-token-dialog-before-after.png
new file mode 100644
index 0000000000..8a81f43c8d
Binary files /dev/null and b/devlog/_plan/260905_admin_token_local_ux/assets/admin-token-dialog-before-after.png differ
diff --git a/gui/src/admin-token-dialog.ts b/gui/src/admin-token-dialog.ts
index af3cdc80e0..f02fed97fb 100644
--- a/gui/src/admin-token-dialog.ts
+++ b/gui/src/admin-token-dialog.ts
@@ -94,6 +94,18 @@ export function promptForAdminToken(
     form.append(heading, accountField, tokenField, validationError, actions);
     dialog.append(form);
 
+    /*
+     * #3483: the notice must carry no text while it is hidden.
+     *
+     * The element is mounted up front so `role="alert"` has a stable target, and the CSS
+     * now scopes `.notice`'s `display` to `:not([hidden])`. Clearing the text alongside the
+     * `hidden` flag keeps the two halves of "there is no error" from drifting apart.
+     */
+    const setValidationError = (text: string | null): void => {
+      validationError.textContent = text ?? "";
+      validationError.hidden = text === null;
+    };
+
     const finish = (value: string | null): void => {
       if (settled) return;
       settled = true;
@@ -113,7 +125,7 @@ export function promptForAdminToken(
       }
       password.disabled = true;
       submit.disabled = true;
-      validationError.hidden = true;
+      setValidationError(null);
 
       void verifyToken(token).then((result) => {
         if (settled) return;
@@ -124,18 +136,16 @@ export function promptForAdminToken(
         password.value = "";
         password.disabled = false;
         submit.disabled = false;
-        validationError.textContent = result === "rejected"
+        setValidationError(result === "rejected"
           ? messages["auth.adminTokenRejected"]
-          : messages["auth.adminTokenUnavailable"];
-        validationError.hidden = false;
+          : messages["auth.adminTokenUnavailable"]);
         password.focus();
       }).catch(() => {
         if (settled) return;
         password.value = "";
         password.disabled = false;
         submit.disabled = false;
-        validationError.textContent = messages["auth.adminTokenUnavailable"];
-        validationError.hidden = false;
+        setValidationError(messages["auth.adminTokenUnavailable"]);
         password.focus();
       });
     });
diff --git a/gui/src/styles.css b/gui/src/styles.css
index 027b055c3a..d95ca0c48e 100644
--- a/gui/src/styles.css
+++ b/gui/src/styles.css
@@ -1304,7 +1304,17 @@ select.input { appearance: none; }
 .empty svg { width: 30px; height: 30px; color: var(--faint); margin-bottom: 12px; }
 .empty .title { color: var(--text); font-weight: var(--weight-semibold); margin-bottom: 6px; }
 
-.notice { font-size: var(--text-control); line-height: var(--leading-body); padding: 9px 12px; border-radius: var(--radius-sm); margin-bottom: 14px; display: flex; align-items: center; gap: 8px; max-width: var(--prose-measure); }
+/*
+ `:not([hidden])`, not a bare `display: flex` — same cascade trap the combos panels hit.
+
+ The admin-token dialog mounts its error notice up front and hides it with the `hidden`
+ attribute until a token is actually rejected. `[hidden] { display: none }` is a
+ USER-AGENT rule, so an author `display: flex` here beat it and painted an empty red
+ bordered box the moment the dialog opened (#3483). Specificity never got a vote; origin
+ decided it. Scoping the display to `:not([hidden])` lets the UA rule win again.
+*/
+.notice:not([hidden]) { display: flex; }
+.notice { font-size: var(--text-control); line-height: var(--leading-body); padding: 9px 12px; border-radius: var(--radius-sm); margin-bottom: 14px; align-items: center; gap: 8px; max-width: var(--prose-measure); }
 .notice svg { width: 15px; height: 15px; flex-shrink: 0; }
 
 /* Portaled status toast — out of document flow so Providers (etc.) do not reflow. */
@@ -1950,12 +1960,13 @@ dialog.modal-overlay::backdrop {
   background: light-dark(#fffbeb, color-mix(in oklab, var(--amber) 20%, var(--surface)));
   color: light-dark(#92400e, #fef3c7);
   border: 1px solid color-mix(in srgb, var(--amber) 32%, transparent);
-  display: flex;
   align-items: center;
   gap: 6px;
   margin-bottom: 12px;
   max-width: var(--prose-measure);
 }
+/* Same UA-vs-author `[hidden]` rule as `.notice` above: `.notice-warn` is used on its own. */
+.notice-warn:not([hidden]) { display: flex; }
 .notice-warn svg { width: 14px; height: 14px; flex-shrink: 0; color: var(--amber); }
 
 .startup-runtime-notice__text,
@@ -1998,8 +2009,10 @@ dialog.modal-overlay::backdrop {
   box-sizing: border-box;
 }
 /* Message above, command+copy below. */
-.notice.notice-warn.startup-runtime-notice {
+.notice.notice-warn.startup-runtime-notice:not([hidden]) {
   display: flex;
+}
+.notice.notice-warn.startup-runtime-notice {
   flex-direction: column;
   align-items: stretch;
   gap: 8px;
diff --git a/gui/tests/admin-token-dialog.test.ts b/gui/tests/admin-token-dialog.test.ts
index 09f237e412..767d348d35 100644
--- a/gui/tests/admin-token-dialog.test.ts
+++ b/gui/tests/admin-token-dialog.test.ts
@@ -126,3 +126,56 @@ test("uses the active UI locale instead of re-detecting browser storage", async
   dialog.dispatchEvent(new testWindow.Event("cancel", { cancelable: true }));
   expect(await pending).toBeNull();
 });
+
+/*
+ * #3483 — the dialog opened with an empty red bordered notice already painted.
+ *
+ * The DOM half: while there is no error the alert must be hidden AND carry no text, so
+ * "hidden" and "empty" cannot drift apart.
+ */
+test("the validation alert is hidden and empty until a token is actually rejected", async () => {
+  const pending = promptForAdminToken(async () => "rejected");
+  const dialog = document.querySelector<HTMLDialogElement>("#opencodex-admin-token-dialog")!;
+  const form = dialog.querySelector<HTMLFormElement>("form")!;
+  const alert = dialog.querySelector<HTMLElement>('[role="alert"]')!;
+
+  expect(alert.hidden).toBe(true);
+  expect(alert.textContent).toBe("");
+
+  const password = form.elements.namedItem("password") as HTMLInputElement;
+  password.value = "wrong-token";
+  form.dispatchEvent(new testWindow.Event("submit", { bubbles: true, cancelable: true }));
+  await Promise.resolve();
+  await Promise.resolve();
+
+  expect(alert.hidden).toBe(false);
+  expect(alert.textContent).toContain("rejected");
+
+  dialog.dispatchEvent(new testWindow.Event("cancel", { cancelable: true }));
+  expect(await pending).toBeNull();
+});
+
+/*
+ * The CSS half, and the one that actually reproduces the report.
+ *
+ * happy-dom applies no author stylesheet and does no layout, so `alert.hidden === true`
+ * passes even while a real browser paints the box: `[hidden] { display: none }` is a
+ * USER-AGENT rule and a bare `.notice { display: flex }` outranks it by origin. The
+ * stylesheet is the only place this contract can be checked — same oracle the combos
+ * workspace uses after the identical bug (gui/tests/combos-detail-tabs-dom.test.tsx).
+ */
+test("notice display rules are scoped so a hidden notice cannot paint", async () => {
+  const css = await Bun.file(new URL("../src/styles.css", import.meta.url)).text();
+
+  expect(css).toContain(".notice:not([hidden])");
+  expect(css).toContain(".notice-warn:not([hidden])");
+  expect(css).toContain(".notice.notice-warn.startup-runtime-notice:not([hidden])");
+
+  // No notice rule may set `display` without the :not([hidden]) guard.
+  for (const block of css.matchAll(/(^|\})\s*([^{}]*\.notice[^{}]*)\{([^}]*)\}/g)) {
+    const selector = block[2]!.trim();
+    const body = block[3]!;
+    if (!/(^|[\s,])display\s*:/.test(body)) continue;
+    expect(selector).toContain(":not([hidden])");
+  }
+});