From 2b28b22055d1bd45224af179490fcfbe8f5e9a6b Mon Sep 17 00:00:00 2001
From: S-jooyoung <jooyoung.dev@gmail.com>
Date: Thu, 3 Sep 2026 14:48:30 +0900
Subject: [PATCH] fix(preact-query): retry on mount for falsy errors when
 throwOnError returns false

`ensurePreventErrorBoundaryRetry` only evaluated a function-valued
`throwOnError` when `query.state.error` was truthy. For a query that
rejected with a falsy value (e.g. `undefined`), the callback was skipped
and the function itself was treated as truthy, so `retryOnMount` was
disabled even though `throwOnError` would have returned `false`.

Check `query.state.status === 'error'` instead so the callback runs for
every failed query. Ports #11328 to preact-query.
---
 .../preact-falsy-error-retry-on-mount.md      |  5 ++++
 .../src/__tests__/useQuery.test.tsx           | 29 +++++++++++++++++++
 .../preact-query/src/errorBoundaryUtils.ts    | 12 +++++---
 3 files changed, 42 insertions(+), 4 deletions(-)
 create mode 100644 .changeset/preact-falsy-error-retry-on-mount.md

diff --git a/.changeset/preact-falsy-error-retry-on-mount.md b/.changeset/preact-falsy-error-retry-on-mount.md
new file mode 100644
index 00000000000..221f243fa55
--- /dev/null
+++ b/.changeset/preact-falsy-error-retry-on-mount.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/preact-query': patch
+---
+
+Allow queries with falsy errors to retry on mount when `throwOnError` returns false.
diff --git a/packages/preact-query/src/__tests__/useQuery.test.tsx b/packages/preact-query/src/__tests__/useQuery.test.tsx
index 554a4787fad..2e524940dee 100644
--- a/packages/preact-query/src/__tests__/useQuery.test.tsx
+++ b/packages/preact-query/src/__tests__/useQuery.test.tsx
@@ -6951,4 +6951,33 @@ describe('useQuery', () => {
     expect(fetchCount).toBe(initialFetchCount + 1)
     expect(queryFn).toHaveBeenCalledTimes(2)
   })
+
+  it('should retry on mount when throwOnError returns false for a falsy error', async () => {
+    const key = queryKey()
+    const queryFn = vi.fn(() => Promise.reject())
+
+    function Component() {
+      const { status } = useQuery({
+        queryKey: key,
+        queryFn,
+        throwOnError: () => false,
+        retryOnMount: () => true,
+        staleTime: Infinity,
+        retry: false,
+      })
+
+      return <div data-testid="status">{status}</div>
+    }
+
+    const rendered1 = renderWithClient(queryClient, <Component />)
+    await vi.advanceTimersByTimeAsync(0)
+    expect(rendered1.getByTestId('status')).toHaveTextContent('error')
+    expect(queryFn).toHaveBeenCalledTimes(1)
+    rendered1.unmount()
+
+    const rendered2 = renderWithClient(queryClient, <Component />)
+    await vi.advanceTimersByTimeAsync(0)
+    expect(rendered2.getByTestId('status')).toHaveTextContent('error')
+    expect(queryFn).toHaveBeenCalledTimes(2)
+  })
 })
diff --git a/packages/preact-query/src/errorBoundaryUtils.ts b/packages/preact-query/src/errorBoundaryUtils.ts
index 98cab52351c..cff311741a2 100644
--- a/packages/preact-query/src/errorBoundaryUtils.ts
+++ b/packages/preact-query/src/errorBoundaryUtils.ts
@@ -27,10 +27,14 @@ export const ensurePreventErrorBoundaryRetry = <
   errorResetBoundary: QueryErrorResetBoundaryValue,
   query: Query<TQueryFnData, TError, TQueryData, TQueryKey> | undefined,
 ) => {
-  const throwOnError =
-    query?.state.error && typeof options.throwOnError === 'function'
-      ? shouldThrowError(options.throwOnError, [query.state.error, query])
-      : options.throwOnError
+  let throwOnError = options.throwOnError
+
+  if (query?.state.status === 'error' && typeof throwOnError === 'function') {
+    throwOnError = shouldThrowError(throwOnError, [
+      query.state.error as TError,
+      query,
+    ])
+  }
 
   if (options.suspense || throwOnError) {
     // Prevent retrying failed query if the error boundary has not been reset yet