fix(solid): avoid hydrating refresh registration

.changeset/fix-refresh-lazy-hydration.md

@@ -0,0 +1,5 @@
+---
+"solid-js": patch
+---
+
+Fix hydration crashing when a lazy component module is evaluated with Solid Refresh enabled (#2920). Refresh component registrations now use plain signals so module-level bookkeeping does not require a reactive owner or consume hydration child IDs.

packages/solid/src/refresh/index.ts

@@ -176,16 +176,15 @@ export function $$component<P extends Record<string, any>>(
 ): (props: P) => SolidElement {
   if (!IS_DEV) return component;
   let current = component;
-  // A writable memo: `createSignal(fn)` in 2.0 computes its value from `fn`
-  // on first read and accepts updater writes. `current` mirrors the latest
-  // component so a recompute (which has no dependencies) stays consistent.
-  const [comp, setComp] = createSignal<(props: P) => SolidElement>(() => current);
+  // Keep the component inside a plain signal so module-level registration is
+  // never treated as a hydration-aware computation.
+  const [comp, setComp] = createSignal({ current });
   const update = (action: () => (props: P) => SolidElement): void => {
     current = action();
-    setComp(() => current);
+    setComp({ current });
   };
   const instances: LiveInstances = { count: 0 };
-  const proxy = createProxy(comp, id, instances, options.location);
+  const proxy = createProxy(() => comp().current, id, instances, options.location);
   registry.components.set(id, {
     id,
     component,

packages/solid/test/client-hydration.spec.ts

@@ -22,6 +22,7 @@ import {
 } from "../src/client/hydration.js";
 import { lazy } from "../src/client/component.js";
 import { Errored, Loading } from "../src/client/flow.js";
+import { $$component, $$registry } from "../src/refresh/index.js";
 
 // Enable the hydration-aware wrappers
 enableHydration();
@@ -66,6 +67,35 @@ function stopHydration() {
   (sharedConfig as any).loadModuleAssets = undefined;
 }
 
+describe("Refresh registration during hydration", () => {
+  afterEach(() => {
+    stopHydration();
+  });
+
+  test("registers a component without a reactive owner", () => {
+    startHydration({});
+
+    const proxy = $$component($$registry(), "LazyComponent", () => "content");
+
+    expect(proxy({})).toBe("content");
+  });
+
+  test("does not consume a hydration child id", () => {
+    startHydration({ t0: "server" });
+
+    let result: unknown;
+    createRoot(
+      () => {
+        $$component($$registry(), "Component", () => "component");
+        result = createMemo(() => "client")();
+      },
+      { id: "t" }
+    );
+
+    expect(result).toBe("server");
+  });
+});
+
 describe("Error Boundary Hydration", () => {
   afterEach(() => {
     stopHydration();