diff --git a/ui/app/routes/api-keys/route.tsx b/ui/app/routes/api-keys/route.tsx
index 5324ed74fe..f500c1e7b9 100644
--- a/ui/app/routes/api-keys/route.tsx
+++ b/ui/app/routes/api-keys/route.tsx
@@ -15,7 +15,7 @@ import {
   SectionLayout,
 } from "~/components/layout/PageLayout";
 import { logger } from "~/utils/logger";
-import { PageErrorContent } from "~/components/ui/error";
+import { LayoutErrorBoundary, PageErrorContent } from "~/components/ui/error";
 import {
   getPostgresClient,
   isPostgresAvailable,
@@ -314,6 +314,5 @@ export default function ApiKeysPage({ loaderData }: Route.ComponentProps) {
 }
 
 export function ErrorBoundary({ error }: Route.ErrorBoundaryProps) {
-  logger.error(error);
-  return <PageErrorContent error={error} />;
+  return <LayoutErrorBoundary error={error} />;
 }
diff --git a/ui/app/routes/autopilot/sessions/$session_id/route.tsx b/ui/app/routes/autopilot/sessions/$session_id/route.tsx
index 96d893aecf..91ee2e326d 100644
--- a/ui/app/routes/autopilot/sessions/$session_id/route.tsx
+++ b/ui/app/routes/autopilot/sessions/$session_id/route.tsx
@@ -10,7 +10,6 @@ import {
 import {
   Await,
   data,
-  isRouteErrorResponse,
   useAsyncError,
   useFetcher,
   useNavigate,
@@ -33,6 +32,7 @@ import { useElementHeight } from "~/hooks/useElementHeight";
 import { useInfiniteScrollUp } from "~/hooks/use-infinite-scroll-up";
 import type { AutopilotStatus, GatewayEvent } from "~/types/tensorzero";
 import { useToast } from "~/hooks/use-toast";
+import { LayoutErrorBoundary } from "~/components/ui/error/LayoutErrorBoundary";
 import { SectionErrorNotice } from "~/components/ui/error/ErrorContentPrimitives";
 import { getFeatureFlags } from "~/utils/feature_flags";
 
@@ -810,29 +810,5 @@ export default function AutopilotSessionEventsPage({
 }
 
 export function ErrorBoundary({ error }: Route.ErrorBoundaryProps) {
-  logger.error(error);
-
-  if (isRouteErrorResponse(error)) {
-    return (
-      <div className="flex h-screen flex-col items-center justify-center gap-4 text-red-500">
-        <h1 className="text-2xl font-bold">
-          {error.status} {error.statusText}
-        </h1>
-        <p>{error.data}</p>
-      </div>
-    );
-  } else if (error instanceof Error) {
-    return (
-      <div className="flex h-screen flex-col items-center justify-center gap-4 text-red-500">
-        <h1 className="text-2xl font-bold">Error</h1>
-        <p>{error.message}</p>
-      </div>
-    );
-  } else {
-    return (
-      <div className="flex h-screen items-center justify-center text-red-500">
-        <h1 className="text-2xl font-bold">Unknown Error</h1>
-      </div>
-    );
-  }
+  return <LayoutErrorBoundary error={error} />;
 }
diff --git a/ui/app/routes/autopilot/sessions/route.tsx b/ui/app/routes/autopilot/sessions/route.tsx
index 0319268cfc..195c761444 100644
--- a/ui/app/routes/autopilot/sessions/route.tsx
+++ b/ui/app/routes/autopilot/sessions/route.tsx
@@ -1,12 +1,7 @@
 import { Plus } from "lucide-react";
 import { Suspense, use } from "react";
 import type { Route } from "./+types/route";
-import {
-  data,
-  isRouteErrorResponse,
-  useLocation,
-  useNavigate,
-} from "react-router";
+import { data, useLocation, useNavigate } from "react-router";
 import { useTensorZeroStatusFetcher } from "~/routes/api/tensorzero/status";
 import {
   PageHeader,
@@ -16,7 +11,7 @@ import {
 import { ActionBar } from "~/components/layout/ActionBar";
 import { Button } from "~/components/ui/button";
 import PageButtons from "~/components/utils/PageButtons";
-import { logger } from "~/utils/logger";
+import { LayoutErrorBoundary } from "~/components/ui/error/LayoutErrorBoundary";
 import { SessionsTableRows } from "../AutopilotSessionsTable";
 import { getAutopilotClient } from "~/utils/tensorzero.server";
 import type { Session } from "~/types/tensorzero";
@@ -214,29 +209,5 @@ export default function AutopilotSessionsPage({
 }
 
 export function ErrorBoundary({ error }: Route.ErrorBoundaryProps) {
-  logger.error(error);
-
-  if (isRouteErrorResponse(error)) {
-    return (
-      <div className="flex h-screen flex-col items-center justify-center gap-4 text-red-500">
-        <h1 className="text-2xl font-bold">
-          {error.status} {error.statusText}
-        </h1>
-        <p>{error.data}</p>
-      </div>
-    );
-  } else if (error instanceof Error) {
-    return (
-      <div className="flex h-screen flex-col items-center justify-center gap-4 text-red-500">
-        <h1 className="text-2xl font-bold">Error</h1>
-        <p>{error.message}</p>
-      </div>
-    );
-  } else {
-    return (
-      <div className="flex h-screen items-center justify-center text-red-500">
-        <h1 className="text-2xl font-bold">Unknown Error</h1>
-      </div>
-    );
-  }
+  return <LayoutErrorBoundary error={error} />;
 }
diff --git a/ui/app/routes/evaluations/$evaluation_name/$datapoint_id/route.tsx b/ui/app/routes/evaluations/$evaluation_name/$datapoint_id/route.tsx
index d67fedbb1f..4afdfdcbe8 100644
--- a/ui/app/routes/evaluations/$evaluation_name/$datapoint_id/route.tsx
+++ b/ui/app/routes/evaluations/$evaluation_name/$datapoint_id/route.tsx
@@ -17,13 +17,13 @@ import { getTensorZeroClient } from "~/utils/tensorzero.server";
 import {
   Await,
   data,
-  isRouteErrorResponse,
   Link,
   redirect,
   useFetcher,
   useLocation,
   type RouteHandle,
 } from "react-router";
+import { LayoutErrorBoundary } from "~/components/ui/error/LayoutErrorBoundary";
 import { Suspense } from "react";
 import { InputElement } from "~/components/input_output/InputElement";
 import { ChatOutputElement } from "~/components/input_output/ChatOutputElement";
@@ -662,31 +662,7 @@ const MetricRow = ({
 };
 
 export function ErrorBoundary({ error }: Route.ErrorBoundaryProps) {
-  logger.error(error);
-
-  if (isRouteErrorResponse(error)) {
-    return (
-      <div className="flex h-screen flex-col items-center justify-center gap-4 text-red-500">
-        <h1 className="text-2xl font-bold">
-          {error.status} {error.statusText}
-        </h1>
-        <p>{error.data}</p>
-      </div>
-    );
-  } else if (error instanceof Error) {
-    return (
-      <div className="flex h-screen flex-col items-center justify-center gap-4 text-red-500">
-        <h1 className="text-2xl font-bold">Error</h1>
-        <p>{error.message}</p>
-      </div>
-    );
-  } else {
-    return (
-      <div className="flex h-screen items-center justify-center text-red-500">
-        <h1 className="text-2xl font-bold">Unknown Error</h1>
-      </div>
-    );
-  }
+  return <LayoutErrorBoundary error={error} />;
 }
 
 type OutputsSectionProps = {
diff --git a/ui/app/routes/observability/functions/route.tsx b/ui/app/routes/observability/functions/route.tsx
index 20154bac45..8794f2b336 100644
--- a/ui/app/routes/observability/functions/route.tsx
+++ b/ui/app/routes/observability/functions/route.tsx
@@ -1,5 +1,4 @@
 import type { Route } from "./+types/route";
-import { isRouteErrorResponse } from "react-router";
 import FunctionsTable from "./FunctionsTable";
 import { useConfig } from "~/context/config";
 import {
@@ -7,7 +6,7 @@ import {
   PageLayout,
   SectionLayout,
 } from "~/components/layout/PageLayout";
-import { logger } from "~/utils/logger";
+import { LayoutErrorBoundary } from "~/components/ui/error/LayoutErrorBoundary";
 import { useMemo, useState } from "react";
 import { getTensorZeroClient } from "~/utils/tensorzero.server";
 
@@ -66,29 +65,5 @@ export default function FunctionsPage({ loaderData }: Route.ComponentProps) {
 }
 
 export function ErrorBoundary({ error }: Route.ErrorBoundaryProps) {
-  logger.error(error);
-
-  if (isRouteErrorResponse(error)) {
-    return (
-      <div className="flex h-screen flex-col items-center justify-center gap-4 text-red-500">
-        <h1 className="text-2xl font-bold">
-          {error.status} {error.statusText}
-        </h1>
-        <p>{error.data}</p>
-      </div>
-    );
-  } else if (error instanceof Error) {
-    return (
-      <div className="flex h-screen flex-col items-center justify-center gap-4 text-red-500">
-        <h1 className="text-2xl font-bold">Error</h1>
-        <p>{error.message}</p>
-      </div>
-    );
-  } else {
-    return (
-      <div className="flex h-screen items-center justify-center text-red-500">
-        <h1 className="text-2xl font-bold">Unknown Error</h1>
-      </div>
-    );
-  }
+  return <LayoutErrorBoundary error={error} />;
 }
diff --git a/ui/app/routes/playground/route.tsx b/ui/app/routes/playground/route.tsx
index 1d010a77b7..130f6efe84 100644
--- a/ui/app/routes/playground/route.tsx
+++ b/ui/app/routes/playground/route.tsx
@@ -4,9 +4,9 @@ import {
   Link,
   type RouteHandle,
   type ShouldRevalidateFunctionArgs,
-  isRouteErrorResponse,
   useNavigation,
 } from "react-router";
+import { LayoutErrorBoundary } from "~/components/ui/error/LayoutErrorBoundary";
 import { DatasetCombobox } from "~/components/dataset/DatasetCombobox";
 import { FunctionSelector } from "~/components/function/FunctionSelector";
 import { PageHeader, PageLayout } from "~/components/layout/PageLayout";
@@ -575,70 +575,7 @@ export default function PlaygroundPage({ loaderData }: Route.ComponentProps) {
 }
 
 export function ErrorBoundary({ error }: Route.ErrorBoundaryProps) {
-  if (isRouteErrorResponse(error)) {
-    return (
-      <PageLayout>
-        <div className="flex min-h-[50vh] flex-col items-center justify-center">
-          <div className="text-center">
-            <h1 className="text-4xl font-bold text-gray-900">
-              {error.status} {error.statusText}
-            </h1>
-            <p className="mt-4 text-lg text-gray-600">{error.data}</p>
-            <Link
-              to="/playground"
-              className="mt-6 inline-block rounded bg-blue-600 px-4 py-2 text-white hover:bg-blue-700"
-            >
-              Go to Playground
-            </Link>
-          </div>
-        </div>
-      </PageLayout>
-    );
-  } else if (error instanceof Error) {
-    return (
-      <PageLayout>
-        <div className="flex min-h-[50vh] flex-col items-center justify-center">
-          <div className="text-center">
-            <h1 className="text-4xl font-bold text-gray-900">Error</h1>
-            <p className="mt-4 text-lg text-gray-600">{error.message}</p>
-            <details className="mt-4 max-w-2xl text-left">
-              <summary className="cursor-pointer text-sm text-gray-500">
-                Stack trace
-              </summary>
-              <pre className="mt-2 overflow-auto rounded bg-gray-100 p-4 text-xs">
-                {error.stack}
-              </pre>
-            </details>
-            <Link
-              to="/playground"
-              className="mt-6 inline-block rounded bg-blue-600 px-4 py-2 text-white hover:bg-blue-700"
-            >
-              Go to Playground
-            </Link>
-          </div>
-        </div>
-      </PageLayout>
-    );
-  } else {
-    return (
-      <PageLayout>
-        <div className="flex min-h-[50vh] flex-col items-center justify-center">
-          <div className="text-center">
-            <h1 className="text-4xl font-bold text-gray-900">Unknown Error</h1>
-            <p className="mt-4 text-lg text-gray-600">
-              An unexpected error occurred. Please try again.
-            </p>
-            <Link
-              to="/playground"
-              className="mt-6 inline-block rounded bg-blue-600 px-4 py-2 text-white hover:bg-blue-700"
-            >
-              Go to Playground
-            </Link>
-          </div>
-        </div>
-      </PageLayout>
-    );
-  }
+  return <LayoutErrorBoundary error={error} />;
 }
 
 function GridRow({
diff --git a/ui/app/utils/tensorzero/errors.ts b/ui/app/utils/tensorzero/errors.ts
index 26f06c5c00..6a6eee0b40 100644
--- a/ui/app/utils/tensorzero/errors.ts
+++ b/ui/app/utils/tensorzero/errors.ts
@@ -824,59 +824,77 @@ export interface PageErrorInfo {
 
 /**
  * Returns user-friendly error info for page-level errors.
- * Maps status codes to sanitized messages - never exposes raw server strings.
+ * Uses custom error.data message if provided (string), otherwise falls back
+ * to generic status-based messages.
  */
 export function getPageErrorInfo(error: unknown): PageErrorInfo {
   if (isRouteErrorResponse(error)) {
+    // Use custom message from error.data if it's a string
+    const customMessage =
+      typeof error.data === "string" && error.data.length > 0
+        ? error.data
+        : null;
+
     switch (error.status) {
       case 400:
         return {
           title: "Bad Request",
           message:
+            customMessage ??
             "The request was invalid. Please check your input and try again.",
           status: 400,
         };
       case 401:
         return {
           title: "Unauthorized",
-          message: "Authentication is required to access this resource.",
+          message:
+            customMessage ??
+            "Authentication is required to access this resource.",
           status: 401,
         };
       case 403:
         return {
           title: "Forbidden",
-          message: "You don't have permission to access this resource.",
+          message:
+            customMessage ??
+            "You don't have permission to access this resource.",
           status: 403,
         };
       case 404:
         return {
           title: "Not Found",
-          message: "The requested resource could not be found.",
+          message:
+            customMessage ?? "The requested resource could not be found.",
           status: 404,
         };
       case 500:
         return {
           title: "Server Error",
-          message: "The server encountered an error. Please try again later.",
+          message:
+            customMessage ??
+            "The server encountered an error. Please try again later.",
           status: 500,
         };
       case 502:
         return {
           title: "Bad Gateway",
-          message: "Unable to reach the server. Please try again later.",
+          message:
+            customMessage ??
+            "Unable to reach the server. Please try again later.",
           status: 502,
         };
       case 503:
         return {
           title: "Service Unavailable",
           message:
+            customMessage ??
             "The service is temporarily unavailable. Please try again later.",
           status: 503,
         };
       default:
         return {
           title: "Error",
-          message: "An unexpected error occurred.",
+          message: customMessage ?? "An unexpected error occurred.",
           status: error.status,
         };
     }