diff --git a/packages/vinext/src/index.ts b/packages/vinext/src/index.ts
index aeb86803a..35ab0367e 100644
--- a/packages/vinext/src/index.ts
+++ b/packages/vinext/src/index.ts
@@ -1704,12 +1704,38 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
           ].flatMap((entry) => (entry ? [toRelativeFileEntry(root, entry)] : []));
           const optimizeEntries = [...new Set([...appEntries, ...explicitInstrumentationEntries])];
 
+          // Resolve conditions per environment so package `exports` maps pick
+          // the correct file for each runtime context. Matches Next.js webpack
+          // behavior (see Next.js `build/webpack-config.ts` reactServerConditionNames)
+          // and Next.js' `test/e2e/import-conditions/`. See #1356.
+          //
+          //   RSC env  : `react-server` + server defaults (+ edge conditions on workerd)
+          //   SSR env  : server defaults (`module`, `node`, …) (+ edge conditions on workerd)
+          //   Client   : client defaults (`module`, `browser`, …)
+          //
+          // When running on Cloudflare Workers / Nitro, the runtime is workerd,
+          // so we add `edge-light`, `workerd`, and `worker` to the server-side
+          // environments. `@cloudflare/vite-plugin` already sets these for its
+          // own worker environment; we set them here for vinext's rsc/ssr envs
+          // because Cloudflare's plugin doesn't reach inside them. Without this,
+          // packages that gate exports on `edge-light` (e.g. Next.js'
+          // `library-with-exports` test fixture) resolve to their `node` export
+          // when running on workerd.
+          const SERVER_DEFAULT_CONDITIONS = ["module", "node", "development|production"];
+          const CLIENT_DEFAULT_CONDITIONS = ["module", "browser", "development|production"];
+          const EDGE_CONDITIONS =
+            hasCloudflarePlugin || hasNitroPlugin ? ["edge-light", "workerd", "worker"] : [];
+          const rscConditions = ["react-server", ...EDGE_CONDITIONS, ...SERVER_DEFAULT_CONDITIONS];
+          const ssrConditions = [...EDGE_CONDITIONS, ...SERVER_DEFAULT_CONDITIONS];
+          const clientConditions = [...CLIENT_DEFAULT_CONDITIONS];
+
           viteConfig.environments = {
             rsc: {
-              ...(hasCloudflarePlugin || hasNitroPlugin
-                ? {}
-                : {
-                    resolve: {
+              resolve: {
+                conditions: rscConditions,
+                ...(hasCloudflarePlugin || hasNitroPlugin
+                  ? {}
+                  : {
                       // Externalize native/heavy packages so the RSC environment
                       // loads them natively via Node rather than through Vite's
                       // ESM module evaluator (which can't handle native addons).
@@ -1727,8 +1753,8 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
                       // When user sets `ssr.external: true`, skip noExternal since
                       // everything is already externalized.
                       ...(userSsrExternal === true ? {} : { noExternal: true as const }),
-                    },
-                  }),
+                    }),
+              },
               optimizeDeps: {
                 exclude: mergeOptimizeDepsExclude(incomingExclude, VINEXT_OPTIMIZE_DEPS_EXCLUDE),
                 entries: optimizeEntries,
@@ -1741,10 +1767,11 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
               },
             },
             ssr: {
-              ...(hasCloudflarePlugin || hasNitroPlugin
-                ? {}
-                : {
-                    resolve: {
+              resolve: {
+                conditions: ssrConditions,
+                ...(hasCloudflarePlugin || hasNitroPlugin
+                  ? {}
+                  : {
                       external: userSsrExternal === true ? true : [...userSsrExternal, "ipaddr.js"],
                       // Force all node_modules through Vite's transform pipeline
                       // so non-JS imports (CSS, images) don't hit Node's native
@@ -1752,8 +1779,8 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
                       // When user sets `ssr.external: true`, skip noExternal since
                       // everything is already externalized.
                       ...(userSsrExternal === true ? {} : { noExternal: true as const }),
-                    },
-                  }),
+                    }),
+              },
               optimizeDeps: {
                 // When userSsrExternal === true, exclude React from the SSR
                 // optimizer so plugin-rsc's crawlFrameworkPkgs doesn't pre-bundle
@@ -1794,6 +1821,9 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
               // service for the client environment, causing virtual module
               // imports to leak to Node's native ESM loader (ERR_UNSUPPORTED_ESM_URL_SCHEME).
               consumer: "client",
+              resolve: {
+                conditions: clientConditions,
+              },
               optimizeDeps: {
                 // Exclude server-external packages from the client dep optimizer.
                 // These packages are server-only by design (listed in next.config's
@@ -1850,6 +1880,12 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
           viteConfig.environments = {
             client: {
               consumer: "client",
+              resolve: {
+                // See #1356: package `exports` must resolve to the browser entry
+                // in the client environment so e.g. isomorphic libs pick their
+                // browser file.
+                conditions: ["module", "browser", "development|production"],
+              },
               optimizeDeps:
                 pagesOptimizeEntries.length > 0 ? { entries: pagesOptimizeEntries } : undefined,
               build: {
@@ -1875,6 +1911,12 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
           viteConfig.environments = {
             client: {
               consumer: "client",
+              resolve: {
+                // See #1356: package `exports` must resolve to the browser entry
+                // in the client environment so e.g. isomorphic libs pick their
+                // browser file.
+                conditions: ["module", "browser", "development|production"],
+              },
               optimizeDeps:
                 pagesOptimizeEntries.length > 0 ? { entries: pagesOptimizeEntries } : undefined,
               build: {
@@ -1890,6 +1932,10 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
             },
             ssr: {
               resolve: {
+                // See #1356: package `exports` must resolve to the node entry in
+                // the Pages Router SSR environment so server-only libs (e.g.
+                // ones that gate on `node`) pick their server file.
+                conditions: ["module", "node", "development|production"],
                 external: ["react", "react-dom", "react-dom/server", "ipaddr.js"],
                 noExternal: true as const,
               },
diff --git a/tests/import-conditions.test.ts b/tests/import-conditions.test.ts
new file mode 100644
index 000000000..97eb3bc73
--- /dev/null
+++ b/tests/import-conditions.test.ts
@@ -0,0 +1,219 @@
+/**
+ * Import conditions tests — verifies that `resolve.conditions` is configured
+ * correctly per Vite environment so package `exports` resolve to the right
+ * file in each runtime context.
+ *
+ * Mirrors Next.js' behavior from `test/e2e/import-conditions/`:
+ *   - RSC environment must include `react-server`
+ *   - Edge / Cloudflare Workers environment must include `edge-light` (and `worker`)
+ *   - Client environment must include `browser`
+ *   - SSR/Node environment must include `node`
+ *
+ * Regression for: https://github.com/cloudflare/vinext/issues/1356
+ * Ported behavior from: https://github.com/vercel/next.js/blob/canary/test/e2e/import-conditions/import-conditions.test.ts
+ */
+import fsp from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import { describe, it, expect, beforeEach, afterEach } from "vite-plus/test";
+
+// The vinext config hook mutates process.env.NODE_ENV as a side effect.
+let originalNodeEnv: string | undefined;
+
+beforeEach(() => {
+  originalNodeEnv = process.env.NODE_ENV;
+});
+
+afterEach(() => {
+  if (originalNodeEnv === undefined) {
+    Reflect.deleteProperty(process.env, "NODE_ENV");
+  } else {
+    Reflect.set(process.env, "NODE_ENV", originalNodeEnv);
+  }
+});
+
+async function makeAppDirFixture(prefix: string) {
+  const tmpDir = await fsp.mkdtemp(path.join(os.tmpdir(), `vinext-import-conditions-${prefix}-`));
+  const rootNodeModules = path.resolve(import.meta.dirname, "../node_modules");
+  await fsp.symlink(rootNodeModules, path.join(tmpDir, "node_modules"), "junction");
+
+  await fsp.mkdir(path.join(tmpDir, "app"), { recursive: true });
+  await fsp.writeFile(
+    path.join(tmpDir, "app", "layout.tsx"),
+    `export default function RootLayout({ children }: { children: React.ReactNode }) { return <html><body>{children}</body></html>; }`,
+  );
+  await fsp.writeFile(
+    path.join(tmpDir, "app", "page.tsx"),
+    `export default function Home() { return <h1>Home</h1>; }`,
+  );
+  await fsp.writeFile(path.join(tmpDir, "next.config.mjs"), `export default {};`);
+
+  return tmpDir;
+}
+
+async function runConfigHook(mockConfig: unknown) {
+  const vinext = (await import("../packages/vinext/src/index.js")).default;
+  const plugins = vinext();
+  const mainPlugin = plugins.find(
+    (p: unknown) =>
+      !!p &&
+      typeof p === "object" &&
+      (p as { name?: string }).name === "vinext:config" &&
+      typeof (p as { config?: unknown }).config === "function",
+  );
+  if (!mainPlugin) throw new Error("vinext:config plugin not found");
+  return await (mainPlugin as { config: (c: unknown, env: unknown) => Promise<any> }).config(
+    mockConfig,
+    { command: "build" },
+  );
+}
+
+describe("resolve.conditions per environment (App Router)", () => {
+  it("sets `react-server` condition on the RSC environment", async () => {
+    const tmpDir = await makeAppDirFixture("rsc");
+    try {
+      const result = await runConfigHook({ root: tmpDir, build: {}, plugins: [] });
+      const rscConditions = result.environments?.rsc?.resolve?.conditions ?? [];
+      expect(
+        rscConditions,
+        `rsc env should include "react-server"; got: ${JSON.stringify(rscConditions)}`,
+      ).toContain("react-server");
+    } finally {
+      await fsp.rm(tmpDir, { recursive: true, force: true }).catch(() => {});
+    }
+  }, 15000);
+
+  it("sets `node` condition on the SSR environment", async () => {
+    const tmpDir = await makeAppDirFixture("ssr");
+    try {
+      const result = await runConfigHook({ root: tmpDir, build: {}, plugins: [] });
+      const ssrConditions = result.environments?.ssr?.resolve?.conditions ?? [];
+      expect(
+        ssrConditions,
+        `ssr env should include "node"; got: ${JSON.stringify(ssrConditions)}`,
+      ).toContain("node");
+      expect(
+        ssrConditions,
+        `ssr env should NOT include "react-server"; got: ${JSON.stringify(ssrConditions)}`,
+      ).not.toContain("react-server");
+    } finally {
+      await fsp.rm(tmpDir, { recursive: true, force: true }).catch(() => {});
+    }
+  }, 15000);
+
+  it("sets `browser` condition on the client environment", async () => {
+    const tmpDir = await makeAppDirFixture("client");
+    try {
+      const result = await runConfigHook({ root: tmpDir, build: {}, plugins: [] });
+      const clientConditions = result.environments?.client?.resolve?.conditions ?? [];
+      expect(
+        clientConditions,
+        `client env should include "browser"; got: ${JSON.stringify(clientConditions)}`,
+      ).toContain("browser");
+      expect(
+        clientConditions,
+        `client env should NOT include "react-server"; got: ${JSON.stringify(clientConditions)}`,
+      ).not.toContain("react-server");
+    } finally {
+      await fsp.rm(tmpDir, { recursive: true, force: true }).catch(() => {});
+    }
+  }, 15000);
+
+  it("adds `edge-light` and `worker` conditions to RSC environment when Cloudflare plugin is present", async () => {
+    const tmpDir = await makeAppDirFixture("rsc-cf");
+    try {
+      // The vinext config hook detects the Cloudflare plugin by name.
+      const fakeCloudflarePlugin = { name: "vite-plugin-cloudflare" };
+      const result = await runConfigHook({
+        root: tmpDir,
+        build: {},
+        plugins: [fakeCloudflarePlugin],
+      });
+      const rscConditions = result.environments?.rsc?.resolve?.conditions ?? [];
+      // RSC on workerd: must keep `react-server` and add edge runtime conditions
+      // so packages like `library-with-exports` resolve their edge-light exports.
+      expect(
+        rscConditions,
+        `rsc env on cloudflare should include "react-server"; got: ${JSON.stringify(rscConditions)}`,
+      ).toContain("react-server");
+      expect(
+        rscConditions,
+        `rsc env on cloudflare should include "edge-light"; got: ${JSON.stringify(rscConditions)}`,
+      ).toContain("edge-light");
+      expect(
+        rscConditions,
+        `rsc env on cloudflare should include "worker"; got: ${JSON.stringify(rscConditions)}`,
+      ).toContain("worker");
+    } finally {
+      await fsp.rm(tmpDir, { recursive: true, force: true }).catch(() => {});
+    }
+  }, 15000);
+
+  it("adds `edge-light` and `worker` conditions to SSR environment when Cloudflare plugin is present", async () => {
+    const tmpDir = await makeAppDirFixture("ssr-cf");
+    try {
+      const fakeCloudflarePlugin = { name: "vite-plugin-cloudflare" };
+      const result = await runConfigHook({
+        root: tmpDir,
+        build: {},
+        plugins: [fakeCloudflarePlugin],
+      });
+      const ssrConditions = result.environments?.ssr?.resolve?.conditions ?? [];
+      expect(
+        ssrConditions,
+        `ssr env on cloudflare should include "edge-light"; got: ${JSON.stringify(ssrConditions)}`,
+      ).toContain("edge-light");
+      expect(
+        ssrConditions,
+        `ssr env on cloudflare should include "worker"; got: ${JSON.stringify(ssrConditions)}`,
+      ).toContain("worker");
+    } finally {
+      await fsp.rm(tmpDir, { recursive: true, force: true }).catch(() => {});
+    }
+  }, 15000);
+});
+
+describe("resolve.conditions per environment (Pages Router on Node)", () => {
+  async function makePagesDirFixture(prefix: string) {
+    const tmpDir = await fsp.mkdtemp(path.join(os.tmpdir(), `vinext-import-conditions-${prefix}-`));
+    const rootNodeModules = path.resolve(import.meta.dirname, "../node_modules");
+    await fsp.symlink(rootNodeModules, path.join(tmpDir, "node_modules"), "junction");
+
+    await fsp.mkdir(path.join(tmpDir, "pages"), { recursive: true });
+    await fsp.writeFile(
+      path.join(tmpDir, "pages", "index.tsx"),
+      `export default function Home() { return <h1>Home</h1>; }`,
+    );
+    await fsp.writeFile(path.join(tmpDir, "next.config.mjs"), `export default {};`);
+
+    return tmpDir;
+  }
+
+  it("sets `node` condition on the SSR environment", async () => {
+    const tmpDir = await makePagesDirFixture("pages-ssr");
+    try {
+      const result = await runConfigHook({ root: tmpDir, build: {}, plugins: [] });
+      const ssrConditions = result.environments?.ssr?.resolve?.conditions ?? [];
+      expect(
+        ssrConditions,
+        `pages ssr env should include "node"; got: ${JSON.stringify(ssrConditions)}`,
+      ).toContain("node");
+    } finally {
+      await fsp.rm(tmpDir, { recursive: true, force: true }).catch(() => {});
+    }
+  }, 15000);
+
+  it("sets `browser` condition on the client environment", async () => {
+    const tmpDir = await makePagesDirFixture("pages-client");
+    try {
+      const result = await runConfigHook({ root: tmpDir, build: {}, plugins: [] });
+      const clientConditions = result.environments?.client?.resolve?.conditions ?? [];
+      expect(
+        clientConditions,
+        `pages client env should include "browser"; got: ${JSON.stringify(clientConditions)}`,
+      ).toContain("browser");
+    } finally {
+      await fsp.rm(tmpDir, { recursive: true, force: true }).catch(() => {});
+    }
+  }, 15000);
+});