From 74e232b85316a0711732b37c4a8493a2e3ea52a2 Mon Sep 17 00:00:00 2001
From: Cursor Agent <cursoragent@cursor.com>
Date: Thu, 24 Sep 2026 16:40:30 +0000
Subject: [PATCH 1/2] fix(test): Run mount effects when renderDataHook suspends

A suspending first render inside synchronous act() drops React's passive-effect task, so provider mount effects never run. Schedule one sibling setState after mount so React flushes those effects.

Co-authored-by: Nathaniel Tucker <me@ntucker.me>
---
 .../render-data-hook-suspend-effects.md       |  7 +++++++
 .../test/src/makeRenderDataClient/index.tsx   | 21 ++++++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/render-data-hook-suspend-effects.md

diff --git a/.changeset/render-data-hook-suspend-effects.md b/.changeset/render-data-hook-suspend-effects.md
new file mode 100644
index 000000000000..51fa328c9bff
--- /dev/null
+++ b/.changeset/render-data-hook-suspend-effects.md
@@ -0,0 +1,7 @@
+---
+'@data-client/test': patch
+---
+
+Fix mount effects when `renderDataHook()` suspends on the first render
+
+`renderDataHook()` and `makeRenderDataHook()` now run provider mount effects when the first render suspends, including `use(useFetch())`. The hook result stays unresolved until the data arrives.
diff --git a/packages/test/src/makeRenderDataClient/index.tsx b/packages/test/src/makeRenderDataClient/index.tsx
index 0bd587ab2be5..662817876328 100644
--- a/packages/test/src/makeRenderDataClient/index.tsx
+++ b/packages/test/src/makeRenderDataClient/index.tsx
@@ -8,7 +8,7 @@ import {
   GenericDispatch,
   DataClientDispatch,
 } from '@data-client/react';
-import React, { memo, Suspense } from 'react';
+import React, { memo, Suspense, useLayoutEffect, useState } from 'react';
 
 import {
   renderHook,
@@ -23,6 +23,17 @@ import { MockProps } from '../mockTypes.js';
 
 const activeCleanups = new Set<() => void>();
 
+/** Sibling that commits even when the hook suspends, so we can schedule a real update. */
+function Kick({ kickRef }: { kickRef: { current: (() => void) | null } }) {
+  const [, setKick] = useState(0);
+  useLayoutEffect(() => {
+    kickRef.current = () => {
+      setKick(count => count + 1);
+    };
+  }, [kickRef]);
+  return null;
+}
+
 if (typeof afterEach === 'function') {
   afterEach(() => {
     for (const fn of activeCleanups) fn();
@@ -138,12 +149,15 @@ export default function makeRenderDataHook(
         }
       : ProviderWithResolver;
 
+    // Captured in Kick's layout effect, which still runs inside the sync mount act.
+    const kickRef: { current: (() => void) | null } = { current: null };
     const wrapper: React.ComponentType<any> = ({
       children,
       ...props
     }: React.PropsWithChildren<P>) => (
       <ProviderWithWrapper {...(props as any)}>
         <Suspense fallback={null}>{children}</Suspense>
+        <Kick kickRef={kickRef} />
       </ProviderWithWrapper>
     );
 
@@ -151,6 +165,11 @@ export default function makeRenderDataHook(
       ...options,
       wrapper,
     });
+    // A suspending first render inside sync act() drops the passive-effect task.
+    // A real setState gives React a task that flushes those effects. An empty act() does not.
+    act(() => {
+      kickRef.current?.();
+    });
     ret.controller = nm['controller'];
     ret.cleanup = cleanup;
     ret.allSettled = allSettled;

From 734291ddd2d5488949c3099d5138a1f62e723e5f Mon Sep 17 00:00:00 2001
From: Cursor Agent <cursoragent@cursor.com>
Date: Thu, 24 Sep 2026 16:52:35 +0000
Subject: [PATCH 2/2] refactor(test): Store Kick's setState directly in
 renderDataHook

Co-authored-by: Nathaniel Tucker <me@ntucker.me>
---
 packages/test/src/makeRenderDataClient/index.tsx | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/packages/test/src/makeRenderDataClient/index.tsx b/packages/test/src/makeRenderDataClient/index.tsx
index 662817876328..ef572efaf238 100644
--- a/packages/test/src/makeRenderDataClient/index.tsx
+++ b/packages/test/src/makeRenderDataClient/index.tsx
@@ -23,13 +23,13 @@ import { MockProps } from '../mockTypes.js';
 
 const activeCleanups = new Set<() => void>();
 
+type KickRef = { current?: React.Dispatch<React.SetStateAction<number>> };
+
 /** Sibling that commits even when the hook suspends, so we can schedule a real update. */
-function Kick({ kickRef }: { kickRef: { current: (() => void) | null } }) {
+function Kick({ kickRef }: { kickRef: KickRef }) {
   const [, setKick] = useState(0);
   useLayoutEffect(() => {
-    kickRef.current = () => {
-      setKick(count => count + 1);
-    };
+    kickRef.current = setKick;
   }, [kickRef]);
   return null;
 }
@@ -149,8 +149,7 @@ export default function makeRenderDataHook(
         }
       : ProviderWithResolver;
 
-    // Captured in Kick's layout effect, which still runs inside the sync mount act.
-    const kickRef: { current: (() => void) | null } = { current: null };
+    const kickRef: KickRef = {};
     const wrapper: React.ComponentType<any> = ({
       children,
       ...props
@@ -168,7 +167,7 @@ export default function makeRenderDataHook(
     // A suspending first render inside sync act() drops the passive-effect task.
     // A real setState gives React a task that flushes those effects. An empty act() does not.
     act(() => {
-      kickRef.current?.();
+      kickRef.current?.(count => count + 1);
     });
     ret.controller = nm['controller'];
     ret.cleanup = cleanup;