presets(vercel): support node.js 26

src/presets/vercel/types.ts

@@ -107,7 +107,13 @@ export interface VercelServerlessFunctionConfig {
   /**
    * The runtime to use. Defaults to the auto-detected Node.js version.
    */
-  runtime?: "nodejs20.x" | "nodejs22.x" | "bun1.x" | (string & {});
+  runtime?:
+    | "nodejs20.x"
+    | "nodejs22.x"
+    | "nodejs24.x"
+    | "nodejs26.x"
+    | "bun1.x"
+    | (string & {});
 
   [key: string]: unknown;
 }

src/presets/vercel/utils.ts

@@ -17,7 +17,8 @@ import { ISR_URL_PARAM } from "./runtime/consts";
 // https://vercel.com/docs/build-output-api/configuration
 
 // https://vercel.com/docs/functions/runtimes/node-js/node-js-versions
-const SUPPORTED_NODE_VERSIONS = [18, 20, 22, 24];
+// https://github.com/vercel/vercel/blob/main/packages/build-utils/src/fs/node-version.ts
+const SUPPORTED_NODE_VERSIONS = [22, 24, 26];
 
 const FALLBACK_ROUTE = "/__fallback";
 
@@ -39,6 +40,15 @@ function getSystemNodeVersion() {
   return Number.isNaN(systemNodeVersion) ? 22 : systemNodeVersion;
 }
 
+export function resolveNodeRuntime(
+  systemNodeVersion = getSystemNodeVersion()
+): `nodejs${number}.x` {
+  const usedNodeVersion =
+    SUPPORTED_NODE_VERSIONS.find((version) => version >= systemNodeVersion) ??
+    SUPPORTED_NODE_VERSIONS.at(-1)!;
+  return `nodejs${usedNodeVersion}.x`;
+}
+
 export async function generateFunctionFiles(nitro: Nitro) {
   const o11Routes = getObservabilityRoutes(nitro);
 
@@ -58,12 +68,7 @@ export async function generateFunctionFiles(nitro: Nitro) {
       runtime = `bun${vercelConfig.bunVersion || "1.x"}`;
     } else {
       // 3. Auto-detect runtime based on system Node.js version
-      const systemNodeVersion = getSystemNodeVersion();
-      const usedNodeVersion =
-        SUPPORTED_NODE_VERSIONS.find(
-          (version) => version >= systemNodeVersion
-        ) ?? SUPPORTED_NODE_VERSIONS.at(-1);
-      runtime = `nodejs${usedNodeVersion}.x`;
+      runtime = resolveNodeRuntime();
     }
   }
 

test/presets/vercel.test.ts

@@ -741,6 +741,30 @@ describe("nitro:preset:vercel:bun", async () => {
   });
 });
 
+describe("nitro:preset:vercel:node-runtime", async () => {
+  const ctx = await setupTest("vercel", {
+    config: {
+      preset: "vercel",
+      vercel: {
+        functions: {
+          runtime: "nodejs26.x",
+        },
+      },
+    },
+  });
+  // Read now: the other vercel groups build into the same output dir
+  const config = await fsp
+    .readFile(
+      resolve(ctx.outDir, "functions/__fallback.func/.vc-config.json"),
+      "utf8"
+    )
+    .then((r) => JSON.parse(r));
+
+  it("should keep an explicit nodejs26.x runtime", () => {
+    expect(config.runtime).toBe("nodejs26.x");
+  });
+});
+
 describe("nitro:preset:vercel:skew-protection", async () => {
   const prevDeploymentId = process.env.VERCEL_DEPLOYMENT_ID;
   process.env.VERCEL_DEPLOYMENT_ID = "dpl_test";

test/unit/vercel-runtime.test.ts

@@ -0,0 +1,49 @@
+import { describe, expect, it } from "vitest";
+import { resolveNodeRuntime } from "../../src/presets/vercel/utils";
+
+describe("vercel: resolveNodeRuntime", () => {
+  it.each([
+    [22, "nodejs22.x"],
+    [24, "nodejs24.x"],
+    [26, "nodejs26.x"],
+  ])(
+    "uses the runtime of a supported Node.js major (%s)",
+    (major, expected) => {
+      expect(resolveNodeRuntime(major)).toBe(expected);
+    }
+  );
+
+  it.each([
+    [21, "nodejs22.x"],
+    [23, "nodejs24.x"],
+    [25, "nodejs26.x"],
+  ])("uses the next supported major for Node.js %s", (major, expected) => {
+    expect(resolveNodeRuntime(major)).toBe(expected);
+  });
+
+  it.each([16, 18, 20])("uses the oldest runtime for Node.js %s", (major) => {
+    expect(resolveNodeRuntime(major)).toBe("nodejs22.x");
+  });
+
+  it.each([27, 28, 30])("uses the newest runtime for Node.js %s", (major) => {
+    expect(resolveNodeRuntime(major)).toBe("nodejs26.x");
+  });
+
+  it("detects the Node.js major of the running process", () => {
+    const node = Object.getOwnPropertyDescriptor(process.versions, "node")!;
+    try {
+      Object.defineProperty(process.versions, "node", {
+        value: "26.1.0",
+        configurable: true,
+      });
+      expect(resolveNodeRuntime()).toBe("nodejs26.x");
+      Object.defineProperty(process.versions, "node", {
+        value: "24.0.0",
+        configurable: true,
+      });
+      expect(resolveNodeRuntime()).toBe("nodejs24.x");
+    } finally {
+      Object.defineProperty(process.versions, "node", node);
+    }
+  });
+});