From 39d8f010d61d191d200e9c0ed588893b3891946b Mon Sep 17 00:00:00 2001
From: "posthog[bot]" <206114724+posthog[bot]@users.noreply.github.com>
Date: Mon, 28 Sep 2026 14:55:48 +0000
Subject: [PATCH 1/2] fix(router): stop reporting browser network failures from
 route loaders

A route loader fetch that gets no response rejects with a bare TypeError, for example when the browser cancels the request during a full-page navigation. The router defaultOnCatch sent these to error tracking as new issues. Skip capture for known browser network-failure TypeErrors.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Generated-By: PostHog Desktop
Task-Id: bcaca723-7de3-463d-a541-1453786b8141
---
 src/lib/network-error.test.ts | 19 +++++++++++++++++++
 src/lib/network-error.ts      | 12 ++++++++++++
 src/router.tsx                |  5 +++++
 3 files changed, 36 insertions(+)
 create mode 100644 src/lib/network-error.test.ts
 create mode 100644 src/lib/network-error.ts

diff --git a/src/lib/network-error.test.ts b/src/lib/network-error.test.ts
new file mode 100644
index 000000000..af28d7b30
--- /dev/null
+++ b/src/lib/network-error.test.ts
@@ -0,0 +1,19 @@
+import { describe, expect, it } from "vitest";
+
+import { isNetworkError } from "#/lib/network-error";
+
+describe("isNetworkError", () => {
+	it("matches browser fetch network failures", () => {
+		expect(isNetworkError(new TypeError("Failed to fetch"))).toBe(true);
+		expect(isNetworkError(new TypeError("NetworkError when attempting to fetch resource."))).toBe(
+			true,
+		);
+		expect(isNetworkError(new TypeError("Load failed"))).toBe(true);
+	});
+
+	it("does not match other errors", () => {
+		expect(isNetworkError(new Error("Failed to fetch"))).toBe(false);
+		expect(isNetworkError(new TypeError("Cannot read properties of undefined"))).toBe(false);
+		expect(isNetworkError("Failed to fetch")).toBe(false);
+	});
+});
diff --git a/src/lib/network-error.ts b/src/lib/network-error.ts
new file mode 100644
index 000000000..481dddcff
--- /dev/null
+++ b/src/lib/network-error.ts
@@ -0,0 +1,12 @@
+// Browsers reject fetch with a bare TypeError when a request gets no response,
+// including requests cancelled by a page unload. Messages vary by engine.
+const networkErrorMessages = new Set([
+	"Failed to fetch",
+	"NetworkError when attempting to fetch resource.",
+	"Load failed",
+	"Network request failed",
+]);
+
+export function isNetworkError(error: unknown) {
+	return error instanceof TypeError && networkErrorMessages.has(error.message);
+}
diff --git a/src/router.tsx b/src/router.tsx
index ec256561f..80b6cd0bc 100644
--- a/src/router.tsx
+++ b/src/router.tsx
@@ -4,6 +4,7 @@ import AppErrorScreen from "./components/AppErrorScreen";
 import AppNotFoundScreen from "./components/AppNotFoundScreen";
 import { capturePostHogClientException } from "./integrations/posthog/provider";
 import { getContext } from "./integrations/tanstack-query/root-provider";
+import { isNetworkError } from "./lib/network-error";
 import { routeTree } from "./routeTree.gen";
 
 export function getRouter() {
@@ -16,6 +17,10 @@ export function getRouter() {
 		defaultPreloadStaleTime: 0,
 		defaultErrorComponent: AppErrorScreen,
 		defaultOnCatch: (error, errorInfo) => {
+			if (isNetworkError(error)) {
+				return;
+			}
+
 			capturePostHogClientException(error, {
 				component_stack: errorInfo.componentStack,
 				error_boundary: "TanStackRouter",

From fe49390ce5afc0675ced2dac4ec563c992162521 Mon Sep 17 00:00:00 2001
From: "posthog[bot]" <206114724+posthog[bot]@users.noreply.github.com>
Date: Mon, 28 Sep 2026 14:56:26 +0000
Subject: [PATCH 2/2] refactor(router): drop non-browser network error message

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Generated-By: PostHog Desktop
Task-Id: bcaca723-7de3-463d-a541-1453786b8141
---
 src/lib/network-error.ts | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/lib/network-error.ts b/src/lib/network-error.ts
index 481dddcff..f4d00012f 100644
--- a/src/lib/network-error.ts
+++ b/src/lib/network-error.ts
@@ -4,7 +4,6 @@ const networkErrorMessages = new Set([
 	"Failed to fetch",
 	"NetworkError when attempting to fetch resource.",
 	"Load failed",
-	"Network request failed",
 ]);
 
 export function isNetworkError(error: unknown) {