From d9c759f93f9f220d8e2d8576ff0f465328eec0ed Mon Sep 17 00:00:00 2001
From: James <james@eli.cx>
Date: Mon, 19 Oct 2026 13:41:04 +0100
Subject: [PATCH 1/6] fix(optimize-imports): only stop at use client modules in
 RSC

#4099 made every directive module the import source for the names it
exports, in both server environments. Record the boundary per environment
instead: RSC stops at any directive, while SSR only stops at use server and
use cache modules, which plugin-rsc and vinext replace with references there.
SSR again rewrites imports past use client barrels such as antd's entry.

Also skip the rewrite for any package whose entry defines every imported
name, not just react-aria-components subpaths, so imports from a use client
entry keep their bare specifier in RSC.
---
 .../vinext/src/plugins/optimize-imports.ts    | 49 ++++++++----
 tests/optimize-imports.test.ts                | 77 +++++++++++++++----
 2 files changed, 98 insertions(+), 28 deletions(-)

diff --git a/packages/vinext/src/plugins/optimize-imports.ts b/packages/vinext/src/plugins/optimize-imports.ts
index 4c7b1757f2..bbfb1768ad 100644
--- a/packages/vinext/src/plugins/optimize-imports.ts
+++ b/packages/vinext/src/plugins/optimize-imports.ts
@@ -49,6 +49,17 @@ type BarrelExportEntry = {
   source: string;
   isNamespace: boolean;
   originalName?: string;
+  /**
+   * The outermost module on the way to `source` that RSC replaces with
+   * references or wrappers because of its directive. RSC must import the name
+   * from it instead.
+   */
+  rscBoundary?: string;
+  /**
+   * The same for SSR, where only "use server" and "use cache" modules are
+   * replaced with references.
+   */
+  ssrBoundary?: string;
 };
 
 type BarrelExportMap = Map<string, BarrelExportEntry>;
@@ -398,7 +409,7 @@ async function buildExportMapFromFile(
   }
 
   const exportMap: BarrelExportMap = new Map();
-  const isBoundary = findBoundaryDirective(ast) !== null;
+  const boundaryDirective = findBoundaryDirective(ast);
 
   // Track import bindings: local name → { source, isNamespace, originalName }
   const importBindings = new Map<
@@ -614,11 +625,17 @@ async function buildExportMapFromFile(
     }
   }
 
-  if (isBoundary) {
-    // Every name a boundary module exports must be imported from the module
-    // itself, including names reached through `export *` into or out of it.
-    for (const name of exportMap.keys()) {
-      exportMap.set(name, { source: filePath, isNamespace: false, originalName: name });
+  if (boundaryDirective) {
+    // Record this module as the boundary for every name it exports, including
+    // names reached through `export *` into or out of it. Outer modules
+    // override inner ones, since an importer reaches them first.
+    const isSsrBoundary = boundaryDirective !== "use client";
+    for (const [name, entry] of exportMap) {
+      exportMap.set(name, {
+        ...entry,
+        rscBoundary: filePath,
+        ssrBoundary: isSsrBoundary ? filePath : entry.ssrBoundary,
+      });
     }
   }
 
@@ -852,6 +869,13 @@ export function createOptimizeImportsPlugin(
             barrelCaches.exportMapCache,
           );
           if (!exportMap || !barrelEntry) continue;
+          // The module to import a name from in this environment, stopping at
+          // the module that this environment replaces with references.
+          const getEntry = (name: string): BarrelExportEntry | undefined => {
+            const entry = exportMap.get(name);
+            const boundary = preferReactServer ? entry?.rscBoundary : entry?.ssrBoundary;
+            return boundary ? { source: boundary, isNamespace: false, originalName: name } : entry;
+          };
 
           // Register sub-package sources so resolveId can find them from
           // the barrel's context (needed for pnpm strict hoisting).
@@ -948,12 +972,9 @@ export function createOptimizeImportsPlugin(
             continue;
           }
 
-          // A subpath entry that defines (or is the boundary for) every imported
-          // name gains nothing from a rewrite.
-          if (
-            isSubpath &&
-            specifiers.every(({ imported }) => exportMap.get(imported)?.source === barrelEntry)
-          ) {
+          // An entry that defines (or is the boundary for) every imported name
+          // gains nothing from a rewrite.
+          if (specifiers.every(({ imported }) => getEntry(imported)?.source === barrelEntry)) {
             continue;
           }
 
@@ -962,7 +983,7 @@ export function createOptimizeImportsPlugin(
           const resolvedPackageSources = new Map<string, string>();
           if (isSubpath) {
             for (const { imported } of specifiers) {
-              const source = exportMap.get(imported)?.source;
+              const source = getEntry(imported)?.source;
               if (!source || path.isAbsolute(source) || resolvedPackageSources.has(source))
                 continue;
               const resolvedId = await resolveFileId(this, source, barrelEntry);
@@ -985,7 +1006,7 @@ export function createOptimizeImportsPlugin(
             }
           >();
           for (const { local, imported } of specifiers) {
-            const entry = exportMap.get(imported);
+            const entry = getEntry(imported);
             if (!entry) continue;
             // Sources in the export map are already absolute paths (for file references)
             // or bare package specifiers — no further resolution needed.
diff --git a/tests/optimize-imports.test.ts b/tests/optimize-imports.test.ts
index 5ac33b04ba..47a86ffefe 100644
--- a/tests/optimize-imports.test.ts
+++ b/tests/optimize-imports.test.ts
@@ -391,28 +391,47 @@ export { Mo as Listbox };`;
     expect(map!.get("parse")).toBeDefined();
   });
 
-  it("does not follow re-exports through a directive boundary", async () => {
+  it("records the directive boundaries that re-exports pass through", async () => {
     const entryPath = "/fake/wildcard-boundary/index.js";
     const files: Record<string, string> = {
-      [entryPath]: `export * from "./client.js";\nexport { Button } from "./button.js";`,
-      "/fake/wildcard-boundary/client.js": `"use client";\nexport { Dialog } from "./dialog.js";\nexport * as Icons from "./icons.js";`,
+      [entryPath]: `export * from "./client.js";\nexport * from "./actions.js";\nexport { Button } from "./button.js";`,
+      "/fake/wildcard-boundary/client.js": `"use client";\nexport { Dialog } from "./dialog.js";\nexport * as Icons from "./icons.js";\nexport * from "./client-actions.js";`,
+      "/fake/wildcard-boundary/client-actions.js": `"use server";\nexport { save } from "./save.js";`,
+      "/fake/wildcard-boundary/actions.js": `"use server";\nexport { submit } from "./submit.js";`,
     };
 
     const map = await buildBarrelExportMap(entryPath, (fp) => Promise.resolve(files[fp] ?? null));
 
-    // Names exported by the "use client" module are imported from it, so the
-    // client reference boundary is kept.
+    // RSC stops at any directive; SSR only at "use server" and "use cache".
     expect(map!.get("Dialog")).toEqual({
-      source: "/fake/wildcard-boundary/client.js",
+      source: "/fake/wildcard-boundary/dialog.js",
       isNamespace: false,
       originalName: "Dialog",
+      rscBoundary: "/fake/wildcard-boundary/client.js",
+      ssrBoundary: undefined,
     });
     expect(map!.get("Icons")).toEqual({
-      source: "/fake/wildcard-boundary/client.js",
+      source: "/fake/wildcard-boundary/icons.js",
+      isNamespace: true,
+      rscBoundary: "/fake/wildcard-boundary/client.js",
+      ssrBoundary: undefined,
+    });
+    // The outermost boundary wins for each environment.
+    expect(map!.get("save")).toMatchObject({
+      source: "/fake/wildcard-boundary/save.js",
+      rscBoundary: "/fake/wildcard-boundary/client.js",
+      ssrBoundary: "/fake/wildcard-boundary/client-actions.js",
+    });
+    expect(map!.get("submit")).toMatchObject({
+      source: "/fake/wildcard-boundary/submit.js",
+      rscBoundary: "/fake/wildcard-boundary/actions.js",
+      ssrBoundary: "/fake/wildcard-boundary/actions.js",
+    });
+    expect(map!.get("Button")).toEqual({
+      source: "/fake/wildcard-boundary/button.js",
       isNamespace: false,
-      originalName: "Icons",
+      originalName: "Button",
     });
-    expect(map!.get("Button")!.source).toBe("/fake/wildcard-boundary/button.js");
   });
 
   it("does not overwrite existing exports when wildcard sub-module has same name", async () => {
@@ -632,7 +651,9 @@ describe("vinext:optimize-imports transform", () => {
   async function setupTransform(
     packageName: string,
     barrelContents: string,
-  ): Promise<(code: string, id: string) => Promise<ReturnType<(...args: any[]) => any>>> {
+  ): Promise<
+    (code: string, id: string, envName?: string) => Promise<ReturnType<(...args: any[]) => any>>
+  > {
     // Create tmp project with a fake package in node_modules.
     // The package name must be in DEFAULT_OPTIMIZE_PACKAGES (or configured via
     // next.config.js) for the plugin's buildStart to include it.
@@ -662,9 +683,9 @@ describe("vinext:optimize-imports transform", () => {
     if (buildStartHook) await buildStartHook.call(plugin);
 
     const transform = unwrapHook(plugin.transform)!;
-    // Return a caller that fakes the environment context as RSC (server)
-    return async (code: string, id: string) =>
-      await (transform as any).call({ ...plugin, environment: { name: "rsc" } }, code, id);
+    // Return a caller that fakes the environment context, RSC by default
+    return async (code: string, id: string, envName = "rsc") =>
+      await (transform as any).call({ ...plugin, environment: { name: envName } }, code, id);
   }
 
   afterEach(() => {
@@ -806,6 +827,33 @@ describe("vinext:optimize-imports transform", () => {
     expect(importLines[0]).toContain(expected);
   });
 
+  it('leaves imports from a "use client" entry alone in RSC but rewrites them in SSR', async () => {
+    // antd is in DEFAULT_OPTIMIZE_PACKAGES, and its entry starts with "use client".
+    const call = await setupTransform("antd", `"use client";\nexport { Button } from "./button";`);
+    const code = `import { Button } from "antd";`;
+    expect(await call(code, "/app/page.tsx", "rsc")).toBeNull();
+
+    const result = await call(code, "/app/page.tsx", "ssr");
+    const button = path.posix.join(tmpDir, "node_modules", "antd", "button");
+    expect(result!.code).toContain(`import { Button } from ${JSON.stringify(button)}`);
+  });
+
+  it('stops at "use server" modules in SSR', async () => {
+    const call = await setupTransform("antd", `export * from "./actions.js";`);
+    const pkgDir = path.posix.join(tmpDir, "node_modules", "antd");
+    fs.writeFileSync(
+      path.join(pkgDir, "actions.js"),
+      `"use server";\nexport { submit } from "./submit.js";`,
+    );
+    const code = `import { submit } from "antd";`;
+    for (const envName of ["rsc", "ssr"]) {
+      const result = await call(code, "/app/page.tsx", envName);
+      expect(result!.code).toContain(
+        `import { submit } from ${JSON.stringify(path.posix.join(pkgDir, "actions.js"))}`,
+      );
+    }
+  });
+
   it("produces separate statements for namespace and named imports from the same source", async () => {
     // lodash-es is in DEFAULT_OPTIMIZE_PACKAGES.
     // The barrel exports both a namespace re-export and a named re-export pointing at
@@ -1158,7 +1206,8 @@ describe("vinext:optimize-imports subpath imports", () => {
     return { call, racDir, nestedStately, resolveCalls };
   }
 
-  const heroToastQueue = `${"/app"}/node_modules/@heroui/react/dist/components/toast/toast-queue.js?v=abc`;
+  const heroToastQueue =
+    "/app/node_modules/@heroui/react/dist/components/toast/toast-queue.js?v=abc";
 
   it("optimizes react-aria-components subpaths by default", () => {
     expect(SUBPATH_OPTIMIZE_PACKAGES).toContain("react-aria-components");

From 95ddd43f2c874a6acc68ff62b3cc3925cf81d177 Mon Sep 17 00:00:00 2001
From: James <james@eli.cx>
Date: Mon, 19 Oct 2026 13:50:37 +0100
Subject: [PATCH 2/6] test(optimize-imports): e2e for SSR rewrites past a use
 client barrel

---
 pnpm-lock.yaml                                |  8 +++++++
 .../optimize-imports-client-barrel.spec.ts    | 24 +++++++++++++++++++
 .../fake-client-barrel/counter.js             | 16 +++++++++++++
 .../fake-client-barrel/index.js               |  5 ++++
 .../fake-client-barrel/package.json           | 11 +++++++++
 .../fake-client-barrel/unused.js              |  5 ++++
 .../optimize-imports-client-barrel/page.tsx   |  7 ++++++
 tests/fixtures/app-basic/next.config.ts       |  3 +++
 tests/fixtures/app-basic/package.json         |  1 +
 9 files changed, 80 insertions(+)
 create mode 100644 tests/e2e/app-router/optimize-imports-client-barrel.spec.ts
 create mode 100644 tests/fixtures/app-basic/__test_packages__/fake-client-barrel/counter.js
 create mode 100644 tests/fixtures/app-basic/__test_packages__/fake-client-barrel/index.js
 create mode 100644 tests/fixtures/app-basic/__test_packages__/fake-client-barrel/package.json
 create mode 100644 tests/fixtures/app-basic/__test_packages__/fake-client-barrel/unused.js
 create mode 100644 tests/fixtures/app-basic/app/optimize-imports-client-barrel/page.tsx

diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 08a2d8d51b..fb10597796 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -1451,6 +1451,9 @@ importers:
       '@vitejs/plugin-rsc':
         specifier: 'catalog:'
         version: 0.5.38(@voidzero-dev/vite-plus-core@1.1.0(@types/node@25.9.2)(esbuild@0.28.1)(jiti@2.7.0)(sass@1.100.0)(tsx@4.21.1)(typescript@7.0.2)(yaml@2.9.0))(react-dom@19.3.1(react@19.3.1))(react-server-dom-webpack@19.3.1(react-dom@19.3.1(react@19.3.1))(react@19.3.1))(react@19.3.1)
+      fake-client-barrel:
+        specifier: file:./__test_packages__/fake-client-barrel
+        version: file:tests/fixtures/app-basic/__test_packages__/fake-client-barrel
       fake-context-lib:
         specifier: file:./__test_packages__/fake-context-lib
         version: file:tests/fixtures/app-basic/__test_packages__/fake-context-lib
@@ -8458,6 +8461,9 @@ packages:
   extendable-error@0.1.7:
     resolution: {integrity: sha512-UOiS2in6/Q0FK0R0q6UY9vYpQ21mr/Qn1KOnte7vsACuNJf514WvCCUHSRCPcgjPT2bAhNIJdlE6bVap1GKmeg==}
 
+  fake-client-barrel@file:tests/fixtures/app-basic/__test_packages__/fake-client-barrel:
+    resolution: {directory: tests/fixtures/app-basic/__test_packages__/fake-client-barrel, type: directory}
+
   fake-context-lib@file:tests/fixtures/app-basic/__test_packages__/fake-context-lib:
     resolution: {directory: tests/fixtures/app-basic/__test_packages__/fake-context-lib, type: directory}
 
@@ -16933,6 +16939,8 @@ snapshots:
 
   extendable-error@0.1.7: {}
 
+  fake-client-barrel@file:tests/fixtures/app-basic/__test_packages__/fake-client-barrel: {}
+
   fake-context-lib@file:tests/fixtures/app-basic/__test_packages__/fake-context-lib: {}
 
   fake-css-lib@file:tests/fixtures/app-basic/__test_packages__/fake-css-lib: {}
diff --git a/tests/e2e/app-router/optimize-imports-client-barrel.spec.ts b/tests/e2e/app-router/optimize-imports-client-barrel.spec.ts
new file mode 100644
index 0000000000..119501c47e
--- /dev/null
+++ b/tests/e2e/app-router/optimize-imports-client-barrel.spec.ts
@@ -0,0 +1,24 @@
+import { test, expect } from "@playwright/test";
+import { waitForAppRouterHydration } from "../helpers";
+
+const BASE = "http://localhost:4174";
+
+// fake-client-barrel is in the fixture's optimizePackageImports. Its entry is a
+// "use client" barrel, and its unused leaf sets a global when it is evaluated.
+test.describe('optimizePackageImports with a "use client" barrel', () => {
+  test("SSR only evaluates the modules that define the imported names", async ({ request }) => {
+    const res = await request.get(`${BASE}/optimize-imports-client-barrel`);
+    expect(res.status()).toBe(200);
+    const html = await res.text();
+    expect(html).toContain('data-testid="client-barrel-counter"');
+    expect(html).toContain('data-unused-loaded="false"');
+  });
+
+  test("the component hydrates", async ({ page }) => {
+    await page.goto(`${BASE}/optimize-imports-client-barrel`);
+    await waitForAppRouterHydration(page);
+    const counter = page.getByTestId("client-barrel-counter");
+    await counter.click();
+    await expect(counter).toHaveText("Count: 1");
+  });
+});
diff --git a/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/counter.js b/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/counter.js
new file mode 100644
index 0000000000..7529e54d0d
--- /dev/null
+++ b/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/counter.js
@@ -0,0 +1,16 @@
+import { createElement, useState } from "react";
+
+export function Counter() {
+  const [count, setCount] = useState(0);
+  return createElement(
+    "button",
+    {
+      "data-testid": "client-barrel-counter",
+      // Hydration can't match: the client loads the whole barrel.
+      "data-unused-loaded": String(globalThis.__fakeClientBarrelUnusedLoaded === true),
+      suppressHydrationWarning: true,
+      onClick: () => setCount((value) => value + 1),
+    },
+    `Count: ${count}`,
+  );
+}
diff --git a/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/index.js b/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/index.js
new file mode 100644
index 0000000000..a94604604d
--- /dev/null
+++ b/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/index.js
@@ -0,0 +1,5 @@
+"use client";
+
+// A "use client" barrel, like antd's entry.
+export { Counter } from "./counter.js";
+export { Unused } from "./unused.js";
diff --git a/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/package.json b/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/package.json
new file mode 100644
index 0000000000..b407257ec5
--- /dev/null
+++ b/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/package.json
@@ -0,0 +1,11 @@
+{
+  "name": "fake-client-barrel",
+  "version": "1.0.0",
+  "private": true,
+  "type": "module",
+  "main": "index.js",
+  "exports": {
+    ".": "./index.js"
+  },
+  "sideEffects": false
+}
diff --git a/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/unused.js b/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/unused.js
new file mode 100644
index 0000000000..003fe1da5b
--- /dev/null
+++ b/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/unused.js
@@ -0,0 +1,5 @@
+globalThis.__fakeClientBarrelUnusedLoaded = true;
+
+export function Unused() {
+  return null;
+}
diff --git a/tests/fixtures/app-basic/app/optimize-imports-client-barrel/page.tsx b/tests/fixtures/app-basic/app/optimize-imports-client-barrel/page.tsx
new file mode 100644
index 0000000000..74037ed77d
--- /dev/null
+++ b/tests/fixtures/app-basic/app/optimize-imports-client-barrel/page.tsx
@@ -0,0 +1,7 @@
+"use client";
+
+import { Counter } from "fake-client-barrel";
+
+export default function OptimizeImportsClientBarrelPage() {
+  return <Counter />;
+}
diff --git a/tests/fixtures/app-basic/next.config.ts b/tests/fixtures/app-basic/next.config.ts
index b534d8177f..ea25e3300e 100644
--- a/tests/fixtures/app-basic/next.config.ts
+++ b/tests/fixtures/app-basic/next.config.ts
@@ -32,6 +32,9 @@ const nextConfig: NextConfig = {
   // don't assert the method's absence against this fixture.
   experimental: {
     gestureTransition: true,
+    // Used by E2E: optimize-imports-client-barrel.spec.ts — a "use client"
+    // barrel whose imports SSR rewrites to the modules that define them.
+    optimizePackageImports: ["fake-client-barrel"],
   },
 
   // Used by Vitest: app-router-production-server.test.ts — a next/dynamic()
diff --git a/tests/fixtures/app-basic/package.json b/tests/fixtures/app-basic/package.json
index 7de39b89ca..6ceaef0650 100644
--- a/tests/fixtures/app-basic/package.json
+++ b/tests/fixtures/app-basic/package.json
@@ -4,6 +4,7 @@
   "type": "module",
   "dependencies": {
     "@vitejs/plugin-rsc": "catalog:",
+    "fake-client-barrel": "file:./__test_packages__/fake-client-barrel",
     "fake-context-lib": "file:./__test_packages__/fake-context-lib",
     "fake-css-lib": "file:./__test_packages__/fake-css-lib",
     "fake-css-module-lib": "file:./__test_packages__/fake-css-module-lib",

From ac91aff1a6ad24ae067ea23513846ac3a8b959b5 Mon Sep 17 00:00:00 2001
From: James <james@eli.cx>
Date: Mon, 19 Oct 2026 13:53:45 +0100
Subject: [PATCH 3/6] style: sort fixture package.json keys

---
 .../__test_packages__/fake-client-barrel/package.json         | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/package.json b/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/package.json
index b407257ec5..8cc882913e 100644
--- a/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/package.json
+++ b/tests/fixtures/app-basic/__test_packages__/fake-client-barrel/package.json
@@ -3,9 +3,9 @@
   "version": "1.0.0",
   "private": true,
   "type": "module",
+  "sideEffects": false,
   "main": "index.js",
   "exports": {
     ".": "./index.js"
-  },
-  "sideEffects": false
+  }
 }

From e2df5ea896a5d781c557510780cb63996de5f63a Mon Sep 17 00:00:00 2001
From: James <james@eli.cx>
Date: Mon, 19 Oct 2026 14:00:47 +0100
Subject: [PATCH 4/6] test: keep the client barrel route out of the Workers
 runtime fixture

---
 tests/after-response-close-worker.test.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tests/after-response-close-worker.test.ts b/tests/after-response-close-worker.test.ts
index aea6b9bee9..9ac73f94ca 100644
--- a/tests/after-response-close-worker.test.ts
+++ b/tests/after-response-close-worker.test.ts
@@ -57,10 +57,11 @@ describe("closeAfterResponseWithBody on the Cloudflare Workers runtime", () => {
       // createIsolatedFixture swaps in a plain workspace node_modules symlink
       // (here, cf-app-basic's, for @cloudflare/vite-plugin + wrangler), which
       // drops app-basic's own `file:./__test_packages__/*` local packages.
-      // Exclude the four routes that depend on those — unrelated to this
+      // Exclude the routes that depend on those — unrelated to this
       // regression — so the rest of the fixture still builds.
       (src) =>
         !src.includes(`${path.sep}app${path.sep}context-dedup-test`) &&
+        !src.includes(`${path.sep}app${path.sep}optimize-imports-client-barrel`) &&
         !src.includes(`${path.sep}app${path.sep}nextjs-compat${path.sep}node-modules-css`) &&
         !src.includes(
           `${path.sep}app${path.sep}nextjs-compat${path.sep}dynamic${path.sep}out-of-root-package`,

From f5acbef7640bcc662065037ceadac258d693e1d4 Mon Sep 17 00:00:00 2001
From: James <james@eli.cx>
Date: Mon, 19 Oct 2026 14:09:32 +0100
Subject: [PATCH 5/6] fix(optimize-imports): register and rewrite by the
 environment's sources

---
 .../vinext/src/plugins/optimize-imports.ts    | 22 ++++----
 tests/optimize-imports.test.ts                | 50 +++++++++++++++++--
 2 files changed, 57 insertions(+), 15 deletions(-)

diff --git a/packages/vinext/src/plugins/optimize-imports.ts b/packages/vinext/src/plugins/optimize-imports.ts
index bbfb1768ad..d25763345c 100644
--- a/packages/vinext/src/plugins/optimize-imports.ts
+++ b/packages/vinext/src/plugins/optimize-imports.ts
@@ -900,16 +900,15 @@ export function createOptimizeImportsPlugin(
               envOriginMap = new Map<string, string>();
               barrelCaches.subpkgOrigin.set(envKey, envOriginMap);
             }
-            for (const entry of exportMap.values()) {
-              if (
-                !entry.source.startsWith("/") &&
-                !entry.source.startsWith(".") &&
-                !envOriginMap.has(entry.source)
-              ) {
+            for (const name of exportMap.keys()) {
+              // Only the sources this environment can emit, so a package behind
+              // a boundary isn't registered.
+              const source = getEntry(name)!.source;
+              if (!source.startsWith("/") && !source.startsWith(".") && !envOriginMap.has(source)) {
                 // First barrel to register this specifier (within this environment) wins.
                 // Sub-package specifiers are keyed per environment so that RSC and SSR
                 // barrel entries don't cross-contaminate each other's resolution context.
-                envOriginMap.set(entry.source, barrelEntry);
+                envOriginMap.set(source, barrelEntry);
               }
             }
           }
@@ -972,9 +971,12 @@ export function createOptimizeImportsPlugin(
             continue;
           }
 
-          // An entry that defines (or is the boundary for) every imported name
-          // gains nothing from a rewrite.
-          if (specifiers.every(({ imported }) => getEntry(imported)?.source === barrelEntry)) {
+          // A subpath entry that defines (or is the boundary for) every imported
+          // name gains nothing from a rewrite.
+          if (
+            isSubpath &&
+            specifiers.every(({ imported }) => getEntry(imported)?.source === barrelEntry)
+          ) {
             continue;
           }
 
diff --git a/tests/optimize-imports.test.ts b/tests/optimize-imports.test.ts
index 47a86ffefe..8d5fec7341 100644
--- a/tests/optimize-imports.test.ts
+++ b/tests/optimize-imports.test.ts
@@ -827,15 +827,55 @@ describe("vinext:optimize-imports transform", () => {
     expect(importLines[0]).toContain(expected);
   });
 
-  it('leaves imports from a "use client" entry alone in RSC but rewrites them in SSR', async () => {
+  it('stops at a "use client" entry in RSC but not in SSR', async () => {
     // antd is in DEFAULT_OPTIMIZE_PACKAGES, and its entry starts with "use client".
     const call = await setupTransform("antd", `"use client";\nexport { Button } from "./button";`);
+    const pkgDir = path.posix.join(tmpDir, "node_modules", "antd");
     const code = `import { Button } from "antd";`;
-    expect(await call(code, "/app/page.tsx", "rsc")).toBeNull();
+    const rscResult = await call(code, "/app/page.tsx", "rsc");
+    expect(rscResult!.code).toContain(
+      `import { Button } from ${JSON.stringify(path.posix.join(pkgDir, "index.js"))}`,
+    );
+
+    const ssrResult = await call(code, "/app/page.tsx", "ssr");
+    expect(ssrResult!.code).toContain(
+      `import { Button } from ${JSON.stringify(path.posix.join(pkgDir, "button"))}`,
+    );
+  });
+
+  it("only registers the packages this environment imports for resolveId", async () => {
+    tmpDir = toSlash(
+      fs.realpathSync(fs.mkdtempSync(path.join(os.tmpdir(), "vinext-optimize-test-"))),
+    );
+    fs.writeFileSync(
+      path.join(tmpDir, "package.json"),
+      JSON.stringify({ name: "test-app", type: "module" }),
+    );
+    const pkgDir = path.join(tmpDir, "node_modules", "antd");
+    fs.mkdirSync(pkgDir, { recursive: true });
+    fs.writeFileSync(
+      path.join(pkgDir, "package.json"),
+      JSON.stringify({ name: "antd", type: "module", main: "./index.js" }),
+    );
+    fs.writeFileSync(
+      path.join(pkgDir, "index.js"),
+      `"use client";\nexport { Slot } from "@radix-ui/react-slot";`,
+    );
+
+    const plugin = createOptimizeImportsPlugin(
+      () => undefined,
+      () => tmpDir,
+    ) as Plugin;
+    const buildStartHook = unwrapHook((plugin as any).buildStart);
+    if (buildStartHook) await buildStartHook.call(plugin);
+    const transform = unwrapHook(plugin.transform)!;
+    const resolveId = unwrapHook(plugin.resolveId)!;
+    const context = { ...plugin, environment: { name: "rsc" }, resolve: vi.fn() };
 
-    const result = await call(code, "/app/page.tsx", "ssr");
-    const button = path.posix.join(tmpDir, "node_modules", "antd", "button");
-    expect(result!.code).toContain(`import { Button } from ${JSON.stringify(button)}`);
+    // RSC imports Slot from the "use client" entry, never from @radix-ui/react-slot.
+    await (transform as any).call(context, `import { Slot } from "antd";`, "/app/page.tsx");
+    await (resolveId as any).call(context, "@radix-ui/react-slot", "/app/other.tsx");
+    expect(context.resolve).not.toHaveBeenCalled();
   });
 
   it('stops at "use server" modules in SSR', async () => {

From f7be78637937465fb520be892a31dd11ca9d51a1 Mon Sep 17 00:00:00 2001
From: James <james@eli.cx>
Date: Mon, 19 Oct 2026 14:22:24 +0100
Subject: [PATCH 6/6] fix(optimize-imports): resolve sub-packages from the
 environment's own registrations

---
 packages/vinext/src/plugins/optimize-imports.ts | 14 ++++++--------
 tests/optimize-imports.test.ts                  | 17 +++++++++++------
 2 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/packages/vinext/src/plugins/optimize-imports.ts b/packages/vinext/src/plugins/optimize-imports.ts
index d25763345c..aaef84d029 100644
--- a/packages/vinext/src/plugins/optimize-imports.ts
+++ b/packages/vinext/src/plugins/optimize-imports.ts
@@ -776,14 +776,12 @@ export function createOptimizeImportsPlugin(
       // In pnpm strict mode, sub-packages like @radix-ui/react-slot are only
       // resolvable from the barrel package's location, not from user code.
       // Use Vite's own resolver (not createRequire) so it picks the ESM entry.
-      // subpkgOrigin is keyed by environment; prefer the current env's map but
-      // fall back to the other env's map for the case where only one environment
-      // has transformed files that import from a given barrel (e.g. a barrel
-      // only reachable from the RSC graph may still need resolving from SSR).
-      const envName = (this as PluginCtx).environment?.name ?? "ssr";
-      const barrelEntry =
-        barrelCaches.subpkgOrigin.get(envName)?.get(source) ??
-        barrelCaches.subpkgOrigin.get(envName === "rsc" ? "ssr" : "rsc")?.get(source);
+      // subpkgOrigin is keyed like the transform below, which registers every
+      // specifier it emits in its own environment's map. The other environment's
+      // map may hold specifiers this one never emits, such as packages behind a
+      // "use client" boundary in RSC.
+      const envKey = (this as PluginCtx).environment?.name === "rsc" ? "rsc" : "ssr";
+      const barrelEntry = barrelCaches.subpkgOrigin.get(envKey)?.get(source);
       if (!barrelEntry) return;
       const resolved = await this.resolve(source, barrelEntry, { skipSelf: true });
       return resolved ?? undefined;
diff --git a/tests/optimize-imports.test.ts b/tests/optimize-imports.test.ts
index 8d5fec7341..4d4e49a053 100644
--- a/tests/optimize-imports.test.ts
+++ b/tests/optimize-imports.test.ts
@@ -870,12 +870,17 @@ describe("vinext:optimize-imports transform", () => {
     if (buildStartHook) await buildStartHook.call(plugin);
     const transform = unwrapHook(plugin.transform)!;
     const resolveId = unwrapHook(plugin.resolveId)!;
-    const context = { ...plugin, environment: { name: "rsc" }, resolve: vi.fn() };
-
-    // RSC imports Slot from the "use client" entry, never from @radix-ui/react-slot.
-    await (transform as any).call(context, `import { Slot } from "antd";`, "/app/page.tsx");
-    await (resolveId as any).call(context, "@radix-ui/react-slot", "/app/other.tsx");
-    expect(context.resolve).not.toHaveBeenCalled();
+    const rsc = { ...plugin, environment: { name: "rsc" }, resolve: vi.fn() };
+    const ssr = { ...plugin, environment: { name: "ssr" }, resolve: vi.fn() };
+
+    // SSR imports Slot from @radix-ui/react-slot, but RSC imports it from the
+    // "use client" entry, whichever environment transforms first.
+    for (const context of [ssr, rsc]) {
+      await (transform as any).call(context, `import { Slot } from "antd";`, "/app/page.tsx");
+      await (resolveId as any).call(context, "@radix-ui/react-slot", "/app/other.tsx");
+    }
+    expect(ssr.resolve).toHaveBeenCalledOnce();
+    expect(rsc.resolve).not.toHaveBeenCalled();
   });
 
   it('stops at "use server" modules in SSR', async () => {