diff --git a/ui/components/auth/oss/sign-in-form.tsx b/ui/components/auth/oss/sign-in-form.tsx
index 7a9f53edfb..4cf6cd9090 100644
--- a/ui/components/auth/oss/sign-in-form.tsx
+++ b/ui/components/auth/oss/sign-in-form.tsx
@@ -16,6 +16,7 @@ import { Button } from "@/components/shadcn";
 import { useToast } from "@/components/shadcn";
 import { CustomInput } from "@/components/shadcn/custom";
 import { Form } from "@/components/shadcn/form";
+import { stripPasswordManagerHighlight } from "@/lib/password-manager";
 import { SignInFormData, signInSchema } from "@/types";
 
 export const SignInForm = ({
@@ -146,6 +147,7 @@ export const SignInForm = ({
     <AuthLayout title={title}>
       <Form {...form}>
         <form
+          ref={stripPasswordManagerHighlight}
           noValidate
           method="post"
           className="flex flex-col gap-4"
diff --git a/ui/components/auth/oss/sign-up-form.tsx b/ui/components/auth/oss/sign-up-form.tsx
index 7eb8575e47..af52e3e742 100644
--- a/ui/components/auth/oss/sign-up-form.tsx
+++ b/ui/components/auth/oss/sign-up-form.tsx
@@ -25,6 +25,7 @@ import {
   FormField,
   FormMessage,
 } from "@/components/shadcn/form";
+import { stripPasswordManagerHighlight } from "@/lib/password-manager";
 import { ApiError, SignUpFormData, signUpSchema } from "@/types";
 
 const AUTH_ERROR_PATHS = {
@@ -152,6 +153,7 @@ export const SignUpForm = ({
     <AuthLayout title="Sign up">
       <Form {...form}>
         <form
+          ref={stripPasswordManagerHighlight}
           noValidate
           method="post"
           className="flex flex-col gap-4"
diff --git a/ui/lib/password-manager.ts b/ui/lib/password-manager.ts
new file mode 100644
index 0000000000..36ac7996b7
--- /dev/null
+++ b/ui/lib/password-manager.ts
@@ -0,0 +1,45 @@
+// 1Password marks autofilled fields with data-com-onepassword-filled and paints
+// a "filled" background highlight via styles injected outside the author cascade
+// (web component / adopted sheet), so CSS overrides can't win. Removing the
+// attribute makes its selector stop matching, restoring the design styles while
+// leaving autofill itself untouched.
+const ONEPASSWORD_FILLED_ATTR = "data-com-onepassword-filled";
+
+/**
+ * Ref callback for a form (or any container) that strips password-manager
+ * fill highlights from descendant inputs.
+ *
+ * Returns a cleanup function so it works as a React 19 ref-callback cleanup —
+ * no useEffect needed. Cheap by design: the observer is scoped to the container
+ * and filtered to a single attribute, so the browser only invokes it when the
+ * password manager toggles that attribute (once per fill), never per frame.
+ *
+ * @example
+ * <form ref={stripPasswordManagerHighlight}>…</form>
+ */
+export const stripPasswordManagerHighlight = (
+  container: HTMLElement | null,
+): (() => void) | void => {
+  if (!container) return;
+
+  // removeAttribute on an element without the attribute is a no-op and emits no
+  // mutation record, so re-firing the observer on our own removal can't loop.
+  const strip = (element: Element) =>
+    element.removeAttribute(ONEPASSWORD_FILLED_ATTR);
+
+  container.querySelectorAll(`[${ONEPASSWORD_FILLED_ATTR}]`).forEach(strip);
+
+  const observer = new MutationObserver((mutations) => {
+    for (const { target } of mutations) {
+      if (target instanceof Element) strip(target);
+    }
+  });
+
+  observer.observe(container, {
+    subtree: true,
+    attributes: true,
+    attributeFilter: [ONEPASSWORD_FILLED_ATTR],
+  });
+
+  return () => observer.disconnect();
+};
diff --git a/ui/styles/globals.css b/ui/styles/globals.css
index df435a8872..b69db8ebac 100644
--- a/ui/styles/globals.css
+++ b/ui/styles/globals.css
@@ -476,6 +476,27 @@
   }
 }
 
+/* Neutralize the browser's native autofill highlight (Chromium/WebKit paint a
+   forced blue/yellow background on :autofill). box-shadow inset masks it; the
+   long transition stops the native color from flashing before the mask lands.
+   Kept UNLAYERED + !important: the mask is a box-shadow and collides with
+   shadcn's focus:ring (also a box-shadow, in @layer utilities) — a layered
+   rule can't win that, so this sits outside the cascade layers. */
+input:autofill,
+input:autofill:hover,
+input:autofill:focus,
+input:autofill:active,
+input:-webkit-autofill,
+input:-webkit-autofill:hover,
+input:-webkit-autofill:focus,
+input:-webkit-autofill:active {
+  -webkit-text-fill-color: var(--text-neutral-secondary) !important;
+  -webkit-box-shadow: 0 0 0 1000px var(--bg-input-primary) inset !important;
+  box-shadow: 0 0 0 1000px var(--bg-input-primary) inset !important;
+  caret-color: var(--text-neutral-secondary);
+  transition: background-color 5000s ease-in-out 0s;
+}
+
 /* Override vaul's injected user-select: none to allow text selection in drawers */
 @media (hover: hover) and (pointer: fine) {
   [data-vaul-drawer][data-vaul-drawer] {