Hydration Strategies - 🌲 Sonamu

Learn hydration strategies for making server-rendered HTML interactive on the client in Sonamu.

Hydration Overview

TanStack Query

dehydrate/hydrate Automatic state restoration

Full Document Hydration

Document level Complete SSR

Date Serialization

dateReviver Automatic conversion

Selective Disable

disableHydrate CSR transition

Sonamu Hydration Process

1. Server: Dehydration

Serialize Query state on the server.

// entry-server.generated.tsx
import { dehydrate } from "@tanstack/react-query";

export async function render(url: string, preloadedData: PreloadedData[] = []) {
  const queryClient = new QueryClient();

  // Inject data
  for (const { queryKey, data } of preloadedData) {
    queryClient.setQueryData(queryKey, data);
  }

  // Dehydrate: Serialize QueryClient state to JSON
  const dehydratedState = dehydrate(queryClient);

  const appHtml = renderToString(<RouterProvider router={router} />);

  return {
    html: appHtml,
    dehydratedState,  // Serialized state
  };
}

2. Data Injection into HTML

// sonamu/src/ssr/renderer.ts
const ssrDataScript = dehydratedState
  ? `<script>window.__SONAMU_SSR__ = ${JSON.stringify(dehydratedState).replace(/</g, "\\u003c")};</script>`
  : "";

// Inject before </body>
const finalHtml = fullDocHtml.replace("</body>", `${ssrDataScript}\n${viteScripts}\n</body>`);

Generated HTML:

<!DOCTYPE html>
<html>
  <head>
    ...
  </head>
  <body>
    <div id="root">
      <!-- Server rendered HTML -->
      <div>Welcome, John</div>
    </div>

    <!-- SSR data -->
    <script>
      window.__SONAMU_SSR__ = {
        queries: [
          {
            queryKey: ["User", "getUser", "C", 123],
            queryHash: '["User","getUser","C",123]',
            state: {
              data: {
                user: {
                  id: 123,
                  username: "John",
                  createdAt: "2024-01-01T00:00:00.000Z",
                },
              },
              dataUpdateCount: 1,
              dataUpdatedAt: 1704067200000,
              status: "success",
            },
          },
        ],
      };
    </script>

    <!-- Vite scripts -->
    <script type="module" src="/src/entry-client.tsx"></script>
  </body>
</html>

3. Client: Hydration

Restore state and activate React on client.

// entry-client.tsx
import { hydrate } from "@tanstack/react-query";
import { dateReviver } from "./services/sonamu.shared";

// 1. Get data from window.__SONAMU_SSR__
const dehydratedState = window.__SONAMU_SSR__
  ? JSON.parse(JSON.stringify(window.__SONAMU_SSR__), dateReviver)
  : undefined;

// 2. Hydrate into QueryClient
if (dehydratedState) {
  hydrate(queryClient, dehydratedState);
}

// 3. React Hydration
if (document.documentElement.innerHTML && dehydratedState) {
  // SSR page - Hydration
  ReactDOM.hydrateRoot(document, <RouterProvider router={router} />);
} else {
  // Pure CSR page - Render new
  ReactDOM.createRoot(document).render(<RouterProvider router={router} />);
}

Date Serialization Handling

Problem: Date objects become strings with JSON.stringify

const user = {
  id: 123,
  username: "John",
  createdAt: new Date("2024-01-01"), // Date object
};

// Serialized on server
JSON.stringify(user);
// '{"id":123,"username":"John","createdAt":"2024-01-01T00:00:00.000Z"}'
//                                          ↑ String!

// Deserialized on client
JSON.parse(json);
// { id: 123, username: "John", createdAt: "2024-01-01T00:00:00.000Z" }
//                                          ↑ Still string!

Solution: dateReviver

Sonamu automatically converts ISO date strings to Date objects.

// services/sonamu.shared.ts
export function dateReviver(_key: string, value: unknown): unknown {
  if (typeof value === "string") {
    // ISO 8601 date string pattern
    const isoDatePattern = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d{3})?Z$/;
    if (isoDatePattern.test(value)) {
      return new Date(value); // Convert to Date object
    }
  }
  return value;
}

// entry-client.tsx
const dehydratedState = window.__SONAMU_SSR__
  ? JSON.parse(JSON.stringify(window.__SONAMU_SSR__), dateReviver)
  : undefined;

// ✅ createdAt is restored as Date object!

Preventing Hydration Mismatch

Problem: Error when server and client HTML differ

// ❌ Hydration Mismatch occurs
function Clock() {
  const [time, setTime] = useState(new Date());
  // Server and client times differ!

  return <div>{time.toLocaleTimeString()}</div>;
}

Error message:

Warning: Text content did not match. Server: "10:30:45" Client: "10:30:47"

Solution 1: Use useEffect

// ✅ Execute only on client
function Clock() {
  const [time, setTime] = useState<Date | null>(null);

  useEffect(() => {
    setTime(new Date());
    const interval = setInterval(() => {
      setTime(new Date());
    }, 1000);
    return () => clearInterval(interval);
  }, []);

  if (!time) return <div>--:--:--</div>;  // Server render
  return <div>{time.toLocaleTimeString()}</div>;  // Client only
}

Solution 2: suppressHydrationWarning

Use when server/client intentionally differ.

function RandomQuote() {
  const [quote] = useState(() => getRandomQuote());

  return (
    <div suppressHydrationWarning>
      {quote}  {/* Server and client may differ */}
    </div>
  );
}

disableHydrate Option

Disable Hydration and Switch to CSR

// api/src/application/sonamu.ts
registerSSR({
  path: "/admin/realtime-dashboard",
  preload: (params) => [
    /* ... */
  ],
  disableHydrate: true, // Disable Hydration
});

How it works:

// entry-client.tsx
const ssrConfig = window.__SONAMU_SSR_CONFIG__;

if (ssrConfig?.disableHydrate) {
  // Render new instead of Hydration
  console.log("[Sonamu] Hydration disabled, rendering as CSR");
  ReactDOM.createRoot(document).render(<RouterProvider router={router} />);
} else {
  // Normal Hydration
  ReactDOM.hydrateRoot(document, <RouterProvider router={router} />);
}

Use cases:

When real-time data is important (dashboards, chat, etc.)
When server/client rendering results intentionally differ
When Hydration mismatch is hard to resolve

Full Document Hydration

Sonamu hydrates the entire document (not just div#root).

// ❌ Typical React app (div#root only)
ReactDOM.hydrateRoot(
  document.getElementById("root"),
  <App />
);

// ✅ Sonamu (entire document)
ReactDOM.hydrateRoot(
  document,
  <RouterProvider router={router} />
);

Reason:

TanStack Router manages up to <html>, <head> tags
<HeadContent />, <Scripts /> components modify head/body
Can dynamically change SEO meta tags

// web/src/routes/__root.tsx
export const Route = createRootRouteWithContext<RouterContext>()({
  head: () => ({
    meta: [
      { charSet: "utf-8" },
      { title: "My App" },
    ],
  }),
  component: RootComponent,
});

function RootComponent() {
  return (
    <html lang="en">
      <head>
        <HeadContent />  {/* Dynamic head tag generation */}
      </head>
      <body>
        <div id="root">
          <Outlet />
        </div>
        <Scripts />  {/* Dynamic script tag generation */}
      </body>
    </html>
  );
}

Suspense and Hydration

You can render Suspense fallback on server and load actual content on client.

// entry-server.generated.tsx
const appHtml = renderToString(
  <Suspense fallback={null}>  {/* Prevents hydration mismatch */}
    <RouterProvider router={router} />
  </Suspense>,
);

Why use fallback=:

All data is already loaded in SSR
Fallback won’t be visible
Prevents Hydration mismatch

QueryClient Configuration

Server Configuration

// entry-server.generated.tsx
const queryClient = new QueryClient({
  defaultOptions: {
    queries: {
      staleTime: 5000, // 5 seconds
      retry: false, // No retry on server
    },
  },
});

Client Configuration

// entry-client.tsx
const queryClient = new QueryClient({
  defaultOptions: {
    queries: {
      staleTime: 5000, // 5 seconds
      retry: false, // No retry
      refetchOnMount: true, // Revalidate on mount
    },
  },
});

Note: It’s good to set the same staleTime for server and client.

Router Context

Pass QueryClient via Router Context.

// web/src/routes/__root.tsx
export interface RouterContext {
  queryClient: QueryClient;
}

export const Route = createRootRouteWithContext<RouterContext>()({
  component: RootComponent,
});

function RootComponent() {
  const { queryClient } = Route.useRouteContext();

  return (
    <html>
      <body>
        <QueryClientProvider client={queryClient}>
          <Outlet />
        </QueryClientProvider>
      </body>
    </html>
  );
}

// entry-server.generated.tsx & entry-client.tsx
const router = createRouter({
  routeTree,
  context: { queryClient }, // Pass via Context
  defaultPreload: "intent",
});

Debugging

Verify Hydration

// entry-client.tsx
if (document.documentElement.innerHTML && dehydratedState) {
  console.log("[Sonamu] Hydrating with SSR data");
  console.log("Queries:", Object.keys(dehydratedState.queries || {}));
  ReactDOM.hydrateRoot(document, <RouterProvider router={router} />);
} else {
  console.log("[Sonamu] Rendering as CSR (no SSR data)");
  ReactDOM.createRoot(document).render(<RouterProvider router={router} />);
}

Check QueryClient State

// Chrome Extension support
window.__TANSTACK_QUERY_CLIENT__ = queryClient;

// Check in console
window.__TANSTACK_QUERY_CLIENT__.getQueryCache().getAll();

Cautions

Cautions when using Hydration: 1. Server/client HTML must match: Prevent Hydration mismatch 2. Careful with window object: window doesn’t exist on server 3. Date objects: dateReviver handles automatically but verify 4. Same QueryClient settings: Match staleTime between server and client 5. Minimize disableHydrate: Use only in special cases

Next Steps

SSR Setup

SSR basic structure

Data Preloading

How to use registerSSR

Cache Control

TanStack Query caching

TanStack Query Docs

Query detailed guide

​Hydration Overview

TanStack Query

Full Document Hydration

Date Serialization

Selective Disable

​Sonamu Hydration Process

​1. Server: Dehydration

​2. Data Injection into HTML

​3. Client: Hydration

​Date Serialization Handling

​Problem: Date objects become strings with JSON.stringify

​Solution: dateReviver

​Preventing Hydration Mismatch

​Problem: Error when server and client HTML differ

​Solution 1: Use useEffect

​Solution 2: suppressHydrationWarning

​disableHydrate Option

​Disable Hydration and Switch to CSR

​Full Document Hydration

​Suspense and Hydration

​QueryClient Configuration

​Server Configuration

​Client Configuration

​Router Context

​Debugging

​Verify Hydration

​Check QueryClient State

​Cautions

​Next Steps

SSR Setup

Data Preloading

Cache Control

TanStack Query Docs

Hydration Overview

Sonamu Hydration Process

1. Server: Dehydration

2. Data Injection into HTML

3. Client: Hydration

Date Serialization Handling

Problem: Date objects become strings with JSON.stringify

Solution: dateReviver

Preventing Hydration Mismatch

Problem: Error when server and client HTML differ

Solution 1: Use useEffect

Solution 2: suppressHydrationWarning

disableHydrate Option

Disable Hydration and Switch to CSR

Full Document Hydration

Suspense and Hydration

QueryClient Configuration

Server Configuration

Client Configuration

Router Context

Debugging

Verify Hydration

Check QueryClient State

Cautions

Next Steps