From b9e7e852407e87b22ff192074a57363f76c0f1d1 Mon Sep 17 00:00:00 2001
From: zan <z4n.mlakar@gmail.com>
Date: Mon, 24 Aug 2026 12:32:56 +0000
Subject: [PATCH] fix(router-ssr-query-core): skip hydrate on stream close

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
---
 .changeset/olive-pugs-shave.md                |  5 +++
 packages/router-ssr-query-core/src/index.ts   |  2 +-
 .../tests/stream-close.test.ts                | 38 +++++++++++++++++++
 3 files changed, 44 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/olive-pugs-shave.md
 create mode 100644 packages/router-ssr-query-core/tests/stream-close.test.ts

diff --git a/.changeset/olive-pugs-shave.md b/.changeset/olive-pugs-shave.md
new file mode 100644
index 00000000000..3ead4f59c3d
--- /dev/null
+++ b/.changeset/olive-pugs-shave.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/router-ssr-query-core': patch
+---
+
+skip hydration when the query stream closes
diff --git a/packages/router-ssr-query-core/src/index.ts b/packages/router-ssr-query-core/src/index.ts
index 685653dea0c..0425728c3f7 100644
--- a/packages/router-ssr-query-core/src/index.ts
+++ b/packages/router-ssr-query-core/src/index.ts
@@ -195,10 +195,10 @@ export function setupCoreRouterSsrQueryIntegration<TRouter extends AnyRouter>({
       reader
         .read()
         .then(async function handle({ done, value }) {
-          queryHydrate(queryClient, value, hydrateOptions)
           if (done) {
             return
           }
+          queryHydrate(queryClient, value, hydrateOptions)
           const result = await reader.read()
           return handle(result)
         })
diff --git a/packages/router-ssr-query-core/tests/stream-close.test.ts b/packages/router-ssr-query-core/tests/stream-close.test.ts
new file mode 100644
index 00000000000..3f757fe84d6
--- /dev/null
+++ b/packages/router-ssr-query-core/tests/stream-close.test.ts
@@ -0,0 +1,38 @@
+import { QueryClient, hydrate } from '@tanstack/query-core'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { setupCoreRouterSsrQueryIntegration } from '../src'
+
+vi.mock('@tanstack/query-core', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('@tanstack/query-core')>()
+  return { ...actual, hydrate: vi.fn(actual.hydrate) }
+})
+
+describe('setupCoreRouterSsrQueryIntegration', () => {
+  beforeEach(() => {
+    vi.mocked(hydrate).mockClear()
+  })
+
+  it('does not hydrate once the query stream is closed', async () => {
+    const queryClient = new QueryClient()
+    const router = { isServer: false, options: {} } as {
+      isServer: boolean
+      options: { hydrate?: (dehydrated: any) => unknown | Promise<unknown> }
+    }
+
+    setupCoreRouterSsrQueryIntegration({ router: router as any, queryClient })
+
+    const stream = new ReadableStream({
+      start(controller) {
+        controller.enqueue({ mutations: [], queries: [] })
+        controller.close()
+      },
+    })
+
+    await router.options.hydrate?.({ queryStream: stream })
+    await vi.waitFor(() => expect(hydrate).toHaveBeenCalled())
+
+    expect(
+      vi.mocked(hydrate).mock.calls.some(([, state]) => state === undefined),
+    ).toBe(false)
+  })
+})