fix(web): create the QueryClient per-request on the server (#1575)

* fix(web): create the QueryClient per-request on the server

The QueryClient was created at module scope, so on the server one instance —
rooted for the process lifetime — was shared by every SSR render. Each render
deposits query state into its cache under request-derived keys (repos, file
paths, searches), and queries never become inactive server-side because
unmount/unsubscribe never run during SSR, so gcTime eviction never fires. The
cache anchored entire server render graphs (react-query observers, hook
state, CodeMirror editor state) at ~400 MiB/h of genuine retention, measured
in production by forcing a full GC via the inspector: 2073 -> 1826 MiB freed
only 247 MiB at a 2 GiB heap.

Follow TanStack Query's advanced SSR guidance: a fresh client per server
render (it dies with the request, releasing everything anchored to it) and a
module-scope singleton in the browser, deliberately not stored in React state
so it survives React suspending during the initial render.

This also removes a correctness defect the docs call out for module-scope
clients: one request's cached query data could previously be rendered into
another request's SSR HTML.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* docs: add changelog entry for query client leak fix

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: brendan-kellam

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed the web process being capped at a ~4GiB heap regardless of how much memory the container has, which caused multi-second garbage collection pauses on larger deployments. [#1569](https://github.com/sourcebot-dev/sourcebot/pull/1569)
 - Upgraded `@sentry/*` to `^10.70.0`, fixing memory leaks where spans retained request data indefinitely. [#1572](https://github.com/sourcebot-dev/sourcebot/pull/1572)
 - Fixed code search result links occasionally getting stuck during navigation and restored Cmd/Ctrl-click to open matches in preview. [#1574](https://github.com/sourcebot-dev/sourcebot/pull/1574)
+- Fixed a server-side memory leak where a single shared react-query cache retained state from every server render; the cache is now created per-request. [#1575](https://github.com/sourcebot-dev/sourcebot/pull/1575)
 
 ## [5.1.6] - 2026-08-10
 

packages/web/src/app/queryClientProvider.tsx

@@ -1,14 +1,47 @@
 'use client';
 
 import * as React from "react"
-import { QueryClient, QueryClientProvider as QueryClientProviderBase, QueryClientProviderProps } from "@tanstack/react-query"
+import { isServer, QueryClient, QueryClientProvider as QueryClientProviderBase, QueryClientProviderProps } from "@tanstack/react-query"
+
+const makeQueryClient = () => {
+    return new QueryClient();
+}
+
+let browserQueryClient: QueryClient | undefined = undefined;
+
+/**
+ * On the server, always create a fresh QueryClient so it lives and dies with
+ * the request. A module-scoped client is rooted for the process lifetime and
+ * every SSR render deposits query state into it — with request-derived query
+ * keys (repos, file paths, searches) that cache only ever grows, and queries
+ * never become inactive server-side (unmount/unsubscribe don't run during
+ * SSR), so nothing is ever evicted. In production this retained whole render
+ * graphs at ~400 MiB/h until the container was OOM-adjacent and liveness
+ * probes killed it.
+ *
+ * In the browser a singleton is correct (one user, unmounts run, gcTime
+ * evicts) and deliberately NOT stored in React state, so the client survives
+ * React suspending during the initial render.
+ *
+ * @see https://tanstack.com/query/latest/docs/framework/react/guides/advanced-ssr
+ */
+const getQueryClient = () => {
+    if (isServer) {
+        return makeQueryClient();
+    }
+
+    if (!browserQueryClient) {
+        browserQueryClient = makeQueryClient();
+    }
+    return browserQueryClient;
+}
 
-const queryClient = new QueryClient();
- 
 export const QueryClientProvider = ({ children, ...props }: Omit<QueryClientProviderProps, 'client'>) => {
-  return (
-    <QueryClientProviderBase client={queryClient} {...props}>
-        {children}
-    </QueryClientProviderBase>
-  )
-}
+    const queryClient = getQueryClient();
+
+    return (
+        <QueryClientProviderBase client={queryClient} {...props}>
+            {children}
+        </QueryClientProviderBase>
+    )
+}