diff --git a/.changeset/ssr-inline-seroval.md b/.changeset/ssr-inline-seroval.md
new file mode 100644
index 0000000..da43e2e
--- /dev/null
+++ b/.changeset/ssr-inline-seroval.md
@@ -0,0 +1,5 @@
+---
+'@solidjs/vite-plugin': patch
+---
+
+Under `vite dev` the SSR environment now inlines `seroval` and `seroval-plugins` next to `solid-js` and `@solidjs/web`. Both ship a `dist/dev` build behind the `development` condition, and `@solidjs/web` imports both. Left external, `seroval-plugins` loaded through Node and its own `import "seroval"` resolved to the prod copy, while the inlined `@solidjs/web` got the runner's dev copy. Seroval detects streams with `instanceof Stream`, so the `Stream` that `ReadableStreamPlugin` builds from one copy was rejected by the other copy's serializer. This broke server components (`serverFunctions: { components: true }`) in dev when a component resolved after the shell flush (for example after an `await` in the server function): its `sc:live` ReadableStream failed with "Seroval caught an error during the parsing process … cannot be parsed/serialized", the `<Loading>` boundary contained the error, and the component only rendered on the client. Builds were unaffected because they bundle a single copy. A host that sets `noExternal: true` and Vitest projects are left alone, as before.
diff --git a/examples/start-ssr/package.json b/examples/start-ssr/package.json
index 866607b..fb275b1 100644
--- a/examples/start-ssr/package.json
+++ b/examples/start-ssr/package.json
@@ -6,7 +6,7 @@
     "dev": "vite",
     "build": "vite build",
     "serve": "NODE_ENV=production node server.js",
-    "test": "node test/run.mjs && node test/http-bridge.mjs && node test/components-warning.mjs && node test/webworker-warning.mjs && node test/dedupe.mjs"
+    "test": "node test/run.mjs && node test/http-bridge.mjs && node test/components-warning.mjs && node test/webworker-warning.mjs && node test/dedupe.mjs && node test/ssr-inline.mjs"
   },
   "devDependencies": {
     "jsdom": "^26.1.0",
diff --git a/examples/start-ssr/test/ssr-inline.mjs b/examples/start-ssr/test/ssr-inline.mjs
new file mode 100644
index 0000000..e3d0489
--- /dev/null
+++ b/examples/start-ssr/test/ssr-inline.mjs
@@ -0,0 +1,89 @@
+// Config-level test for the dev SSR inline list (`environments.ssr.resolve.noExternal`):
+//   - under `serve`, `solid-js`, `@solidjs/web`, `seroval` and
+//     `seroval-plugins` are inlined. Each ships a `dist/dev` build behind
+//     the `development` condition; left external, Node resolves their own
+//     imports without it and a second (prod) copy loads beside the runner's
+//     dev copy. For seroval that breaks `instanceof Stream`, so a server
+//     component's `sc:live` ReadableStream fails to serialize
+//     ("cannot be parsed/serialized") when it lands after the shell flush,
+//   - host entries are kept alongside,
+//   - a host that set `noExternal: true` is left alone,
+//   - under `build` none of them are added (dev-only fix; the build bundles
+//     one copy of everything).
+//
+// Pure resolveConfig — no dev server, no browser. Requires the plugin built
+// (pnpm build at the repo root). Usage: node test/ssr-inline.mjs
+
+import { fileURLToPath } from 'node:url';
+import path from 'node:path';
+import { resolveConfig } from 'vite';
+import solidPlugin from '@solidjs/vite-plugin';
+
+const exampleDir = path.dirname(path.dirname(fileURLToPath(import.meta.url)));
+const INLINED = ['solid-js', '@solidjs/web', 'seroval', 'seroval-plugins'];
+
+const results = [];
+function record(name, ok, detail = '') {
+  results.push({ name, ok, detail });
+  console.log(`  ${ok ? 'PASS' : 'FAIL'} ${name}${detail && !ok ? ` — ${detail}` : ''}`);
+}
+
+async function ssrNoExternal(command, ssrResolve) {
+  const config = await resolveConfig(
+    {
+      root: exampleDir,
+      configFile: false,
+      logLevel: 'error',
+      ...(ssrResolve ? { environments: { ssr: { resolve: ssrResolve } } } : {}),
+      plugins: [solidPlugin({ ssr: true })],
+    },
+    command,
+  );
+  // A bare `build` resolve may carry no ssr environment at all.
+  return config.environments.ssr?.resolve.noExternal;
+}
+
+const show = (v) => (Array.isArray(v) ? v.map(String).join(', ') : String(v));
+
+{
+  const noExternal = await ssrNoExternal('serve');
+  record(
+    'serve: solid-js, @solidjs/web, seroval and seroval-plugins inlined in ssr',
+    Array.isArray(noExternal) && INLINED.every((pkg) => noExternal.includes(pkg)),
+    show(noExternal),
+  );
+}
+
+{
+  const noExternal = await ssrNoExternal('serve', { noExternal: ['host-pkg'] });
+  record(
+    'serve: host noExternal entries kept alongside',
+    Array.isArray(noExternal) &&
+      noExternal.includes('host-pkg') &&
+      INLINED.every((pkg) => noExternal.includes(pkg)),
+    show(noExternal),
+  );
+}
+
+{
+  const noExternal = await ssrNoExternal('serve', { noExternal: true });
+  record('serve: host noExternal: true left alone', noExternal === true, show(noExternal));
+}
+
+{
+  const noExternal = await ssrNoExternal('build');
+  record(
+    'build: seroval and seroval-plugins not added (dev-only fix)',
+    !Array.isArray(noExternal) ||
+      (!noExternal.includes('seroval') && !noExternal.includes('seroval-plugins')),
+    show(noExternal),
+  );
+}
+
+const failed = results.filter((r) => !r.ok);
+console.log(`\n${results.length - failed.length}/${results.length} assertions passed`);
+if (failed.length) {
+  console.log('\nFailures:');
+  for (const f of failed) console.log(`  ${f.name} — ${f.detail}`);
+  process.exit(1);
+}
diff --git a/src/index.ts b/src/index.ts
index b752f40..d3c5eb8 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1592,12 +1592,25 @@ export default function solidPlugin(options: Partial<Options> = {}): Plugin[] {
         // reach the same copy. Vitest projects manage their own inlining
         // (`test.server.deps` above) and are left alone, as is a host that
         // set `noExternal: true` (everything is inlined already).
+        //
+        // `seroval` and `seroval-plugins` split the same way: both ship a
+        // `dist/dev` build behind `development`, and `@solidjs/web` imports
+        // both. Left external, `seroval-plugins` loads through Node and its
+        // own `import "seroval"` lands on the prod copy, while the inlined
+        // `@solidjs/web` gets the runner's dev copy. Seroval tells a stream
+        // apart with `instanceof Stream`, so the `Stream` that
+        // `ReadableStreamPlugin` builds from one copy is rejected by the
+        // other's serializer ("cannot be parsed/serialized"). A server
+        // component that lands after the shell flushes hits this: its
+        // `sc:live` channel is a ReadableStream serialized into the document.
         if (!isTestMode && config.resolve.noExternal !== true) {
           const noExternal = config.resolve.noExternal;
           config.resolve.noExternal = [
             ...(Array.isArray(noExternal) ? noExternal : noExternal ? [noExternal] : []),
             'solid-js',
             '@solidjs/web',
+            'seroval',
+            'seroval-plugins',
           ];
         }
       }