diff --git a/package.json b/package.json
index 2313ac1d20..1649b6c00f 100644
--- a/package.json
+++ b/package.json
@@ -76,6 +76,7 @@
     "bridge/agentenv/solve_cleanup.py",
     "scripts/rea.mjs",
     "scripts/lib/cli-process-environment.mjs",
+    "scripts/lib/runtime-admission.mjs",
     "scripts/rea-android-workspace-guardian.mjs",
     "scripts/electron-active-hook.cjs",
     "scripts/electron-active-hook-boundaries.cjs",
diff --git a/scripts/ci/scopes.mjs b/scripts/ci/scopes.mjs
index 7d35e994d2..1f04ef012c 100644
--- a/scripts/ci/scopes.mjs
+++ b/scripts/ci/scopes.mjs
@@ -247,6 +247,8 @@ const PATH_SCOPES = {
     "tests/boundary/filesystem/releaseProposal.test.ts",
     "scripts/rea.mjs",
     "scripts/lib/cli-process-environment.mjs",
+    "scripts/lib/runtime-admission.mjs",
+    "scripts/lib/runtime-admission.d.mts",
     "install.sh",
     "src/config/**",
     "src/application/Setup*.ts",
@@ -493,6 +495,8 @@ const PATH_SCOPES = {
     "src/contracts/toolEffects.ts",
     "scripts/rea.mjs",
     "scripts/lib/cli-process-environment.mjs",
+    "scripts/lib/runtime-admission.mjs",
+    "scripts/lib/runtime-admission.d.mts",
     "src/process/**",
     "src/artifacts/SafeOutputTree.ts",
     "scripts/verify/javascript/recovery.mjs",
diff --git a/scripts/lib/runtime-admission.d.mts b/scripts/lib/runtime-admission.d.mts
new file mode 100644
index 0000000000..76d8727d01
--- /dev/null
+++ b/scripts/lib/runtime-admission.d.mts
@@ -0,0 +1,11 @@
+/** True when `version` is a release admitted by an `engines.node` range. */
+export function satisfiesNodeRange(range: string, version: string): boolean;
+
+/** Refusal text for a release outside `range`, or undefined when it is admitted. */
+export function unsupportedRuntimeMessage(
+  range: string,
+  version: string,
+): string | undefined;
+
+/** Human-readable release families for an `engines.node` range. */
+export function supportedReleaseProse(range: string): string;
diff --git a/scripts/lib/runtime-admission.mjs b/scripts/lib/runtime-admission.mjs
new file mode 100644
index 0000000000..5ba168383f
--- /dev/null
+++ b/scripts/lib/runtime-admission.mjs
@@ -0,0 +1,54 @@
+/**
+ * Reject a Node.js release the compiled runtime cannot link against.
+ *
+ * The dispatcher imports compiled modules before it can report anything, and
+ * those modules import Node APIs that some releases do not export. Checking the
+ * published range here keeps that failure a readable refusal instead of a
+ * module-linking stack trace.
+ *
+ * `range` is the package's own `engines.node`, so the dispatcher and the
+ * installer cannot drift apart. This module deliberately has no imports: the
+ * dispatcher must admit the runtime before any dependency, including `semver`,
+ * can be resolved.
+ */
+export const unsupportedRuntimeMessage = (range, version) => {
+  if (typeof range !== "string" || range.length === 0) return undefined;
+  if (satisfiesNodeRange(range, version)) return undefined;
+  return (
+    `REA requires ${supportedReleaseProse(range)}; this process runs Node.js ${version}. ` +
+    "Install a supported release, then retry."
+  );
+};
+
+/** Human-readable release families for an `engines.node` range. */
+export const supportedReleaseProse = (range) =>
+  `Node.js ${range
+    .split("||")
+    .map((clause) => {
+      const floor = /^(\^|>=)\s*(\d+\.\d+\.\d+)$/.exec(clause.trim());
+      if (floor === null) return clause.trim();
+      return floor[1] === ">="
+        ? `${floor[2]}+`
+        : `${floor[2].split(".")[0]}.x (>=${floor[2]})`;
+    })
+    .join(", ")}`;
+
+const VERSION = /^(\d+)\.(\d+)\.(\d+)$/;
+const FLOOR = /^(>=|\^)\s*(\d+)\.(\d+)\.(\d+)$/;
+
+/** Every clause of the published range is `^major.minor.patch` or `>=`. */
+export const satisfiesNodeRange = (range, version) => {
+  const found = VERSION.exec(version);
+  // A prerelease or a non-release spelling is never an admitted release.
+  if (found === null) return false;
+  const [, major, minor, patch] = found;
+  return range.split("||").some((clause) => {
+    const floor = FLOOR.exec(clause.trim());
+    if (floor === null) return false;
+    const [, operator, floorMajor, floorMinor, floorPatch] = floor;
+    if (Number(major) !== Number(floorMajor))
+      return operator === ">=" && Number(major) > Number(floorMajor);
+    if (minor !== floorMinor) return Number(minor) > Number(floorMinor);
+    return Number(patch) >= Number(floorPatch);
+  });
+};
diff --git a/scripts/prepack.mjs b/scripts/prepack.mjs
index f3c8061927..eca4b6268f 100644
--- a/scripts/prepack.mjs
+++ b/scripts/prepack.mjs
@@ -46,6 +46,7 @@ if (await pathExists(join(root, "src"))) {
 } else {
   for (const path of [
     "scripts/lib/cli-process-environment.mjs",
+    "scripts/lib/runtime-admission.mjs",
     "dist/main.js",
     "dist/mcp/main.js",
     "dist/cli-runtime/cli.js",
diff --git a/scripts/rea.mjs b/scripts/rea.mjs
index 2c0ff9af02..3c57696a85 100755
--- a/scripts/rea.mjs
+++ b/scripts/rea.mjs
@@ -5,6 +5,7 @@ import { dirname, resolve } from "node:path";
 import { fileURLToPath } from "node:url";
 
 import { prepareCliProcessEnvironment } from "./lib/cli-process-environment.mjs";
+import { unsupportedRuntimeMessage } from "./lib/runtime-admission.mjs";
 
 // Route production MCP before importing Incur. Incur owns registration helpers
 // such as `mcp add`, while the MCP runtime serves the tool catalog over stdio
@@ -13,6 +14,19 @@ const args = process.argv.slice(2);
 const { default: packageJson } = await import("../package.json", {
   with: { type: "json" },
 });
+// Admit the runtime before the first compiled import. Compiled modules import
+// Node APIs that absent releases only reject while linking, so an unsupported
+// release previously surfaced as a module error from every command, including
+// `--version` and `doctor`. `process.exit` is required here: setting exitCode
+// would still reach the imports below.
+const unsupportedRuntime = unsupportedRuntimeMessage(
+  packageJson.engines?.node,
+  process.versions.node,
+);
+if (unsupportedRuntime !== undefined) {
+  process.stderr.write(`${unsupportedRuntime}\n`);
+  process.exit(1);
+}
 prepareCliProcessEnvironment(
   process.env,
   process.platform,
diff --git a/scripts/verify-package-pack.mjs b/scripts/verify-package-pack.mjs
index 7009b1a81c..22f889874b 100644
--- a/scripts/verify-package-pack.mjs
+++ b/scripts/verify-package-pack.mjs
@@ -191,6 +191,8 @@ export async function verifyPackagePack({ root, workspace, commands }) {
     throw new Error("package did not expose both rea command entry points");
   if (!packedFiles.includes("package/scripts/lib/cli-process-environment.mjs"))
     throw new Error("package omitted the CLI process environment owner");
+  if (!packedFiles.includes("package/scripts/lib/runtime-admission.mjs"))
+    throw new Error("package omitted the CLI runtime admission owner");
   if (packedFiles.some((path) => path.startsWith("package/.agents/")))
     throw new Error(
       "package included authored skill sources instead of only the generated bundle",
diff --git a/tests/boundary/cli/dispatcher.test.ts b/tests/boundary/cli/dispatcher.test.ts
index 3c9a0ff22a..af8ac83d82 100644
--- a/tests/boundary/cli/dispatcher.test.ts
+++ b/tests/boundary/cli/dispatcher.test.ts
@@ -1,9 +1,10 @@
-import { copyFile, cp } from "node:fs/promises";
+import { access, copyFile, cp } from "node:fs/promises";
 import { join, resolve } from "node:path";
 import { pathToFileURL } from "node:url";
 
 import { describe, expect } from "vitest";
 
+import { unsupportedRuntimeMessage } from "../../../scripts/lib/runtime-admission.mjs";
 import { workspaceCliTest } from "../../support/cli/workspaceCliFixture.js";
 import type { TestWorkspace } from "../../support/workspace/workspaceFixture.js";
 
@@ -27,6 +28,10 @@ const installCliRuntime = async (
       "scripts/lib/cli-process-environment.mjs",
       workspace.path("scripts/lib/cli-process-environment.mjs"),
     ),
+    copyFile(
+      "scripts/lib/runtime-admission.mjs",
+      workspace.path("scripts/lib/runtime-admission.mjs"),
+    ),
     workspace.write(
       "package.json",
       JSON.stringify({ type: "module", version: "1.0.0" }),
@@ -188,6 +193,67 @@ describe("doctor configuration dispatch", () => {
   );
 });
 
+describe("runtime admission dispatch", () => {
+  workspaceCliTest(
+    "refuses an unsupported runtime before loading the compiled runtime",
+    async ({ processes, workspace }) => {
+      const marker = workspace.path("compiled-runtime-loaded");
+      const loaded = `import { writeFileSync } from "node:fs";\nwriteFileSync(${JSON.stringify(marker)}, "loaded");\n`;
+      const range = ">=999.0.0";
+      await installCliRuntime(workspace, loaded, loaded);
+      await workspace.write(
+        "package.json",
+        JSON.stringify({
+          type: "module",
+          version: "1.0.0",
+          engines: { node: range },
+        }),
+      );
+      const result = await processes.run(
+        process.execPath,
+        [workspace.path("scripts/rea.mjs"), "--version"],
+        { cwd: workspace.root },
+      );
+      expect(result.exitCode).toBe(1);
+      expect(result.stdout).toBe("");
+      expect(result.stderr).toBe(
+        `${unsupportedRuntimeMessage(range, process.versions.node)}\n`,
+      );
+      await expect(access(marker)).rejects.toMatchObject({ code: "ENOENT" });
+    },
+  );
+
+  workspaceCliTest(
+    "admits a runtime the package engines field allows",
+    async ({ processes, workspace }) => {
+      await installCliRuntime(
+        workspace,
+        "export const closeCliResources = () => {}; export const createCli = () => ({ serve: () => {} });\n",
+      );
+      const previousMajor = Number(process.versions.node.split(".")[0]) - 1;
+      for (const range of [
+        `^${process.versions.node}`,
+        `>=${previousMajor}.0.0`,
+      ]) {
+        await workspace.write(
+          "package.json",
+          JSON.stringify({
+            type: "module",
+            version: "1.0.0",
+            engines: { node: range },
+          }),
+        );
+        const result = await processes.run(
+          process.execPath,
+          [workspace.path("scripts/rea.mjs"), "fixture"],
+          { cwd: workspace.root },
+        );
+        expect(result.stderr).toBe("");
+      }
+    },
+  );
+});
+
 describe("executable dispatcher", () => {
   workspaceCliTest(
     "does not append recovery output after delegated stdout has begun",
@@ -300,6 +366,10 @@ describe("executable dispatcher", () => {
           "scripts/lib/cli-process-environment.mjs",
           workspace.path("scripts/lib/cli-process-environment.mjs"),
         ),
+        copyFile(
+          "scripts/lib/runtime-admission.mjs",
+          workspace.path("scripts/lib/runtime-admission.mjs"),
+        ),
         workspace.write(
           "package.json",
           JSON.stringify({ type: "module", version: "1.0.0" }),
diff --git a/tests/boundary/cli/runtimeAdmission.test.ts b/tests/boundary/cli/runtimeAdmission.test.ts
new file mode 100644
index 0000000000..cf96efc3f7
--- /dev/null
+++ b/tests/boundary/cli/runtimeAdmission.test.ts
@@ -0,0 +1,37 @@
+import { describe, expect, it } from "vitest";
+
+import { satisfiesNodeRange } from "../../../scripts/lib/runtime-admission.mjs";
+
+describe("satisfiesNodeRange", () => {
+  it("admits a caret floor and later patches or minors in that major", () => {
+    expect(satisfiesNodeRange("^22.23.4", "22.23.4")).toBe(true);
+    expect(satisfiesNodeRange("^22.23.4", "22.23.5")).toBe(true);
+    expect(satisfiesNodeRange("^22.23.4", "22.24.0")).toBe(true);
+    expect(satisfiesNodeRange("^22.23.4", "22.23.3")).toBe(false);
+    expect(satisfiesNodeRange("^22.23.4", "22.22.9")).toBe(false);
+  });
+
+  it("rejects a higher major under a caret and admits it under a minimum", () => {
+    expect(satisfiesNodeRange("^22.23.4", "23.0.0")).toBe(false);
+    expect(satisfiesNodeRange(">=22.23.4", "23.0.0")).toBe(true);
+    expect(satisfiesNodeRange(">=22.23.4", "22.23.4")).toBe(true);
+    expect(satisfiesNodeRange(">=22.23.4", "22.23.3")).toBe(false);
+    expect(satisfiesNodeRange(">=22.23.4", "22.22.0")).toBe(false);
+  });
+
+  it("admits either clause of a union", () => {
+    const range = "^22.23.4 || >=26.12.1";
+    expect(satisfiesNodeRange(range, "22.23.4")).toBe(true);
+    expect(satisfiesNodeRange(range, "26.12.1")).toBe(true);
+    expect(satisfiesNodeRange(range, "27.0.0")).toBe(true);
+    expect(satisfiesNodeRange(range, "24.0.0")).toBe(false);
+    expect(satisfiesNodeRange(range, "26.12.0")).toBe(false);
+  });
+
+  it("rejects prerelease and non-release spellings", () => {
+    expect(satisfiesNodeRange("^22.23.4", "22.23.4-rc.1")).toBe(false);
+    expect(satisfiesNodeRange(">=22.23.4", "22.23.4-rc.1")).toBe(false);
+    expect(satisfiesNodeRange("^22.23.4", "not-a-version")).toBe(false);
+    expect(satisfiesNodeRange("^22.23.4", "22.23")).toBe(false);
+  });
+});
diff --git a/tests/boundary/filesystem/ciChangeScope.test.ts b/tests/boundary/filesystem/ciChangeScope.test.ts
index 7ff6281d9b..c3b560ec47 100644
--- a/tests/boundary/filesystem/ciChangeScope.test.ts
+++ b/tests/boundary/filesystem/ciChangeScope.test.ts
@@ -1492,6 +1492,26 @@ it.each([
       readiness: false,
     },
   ],
+  [
+    "scripts/lib/runtime-admission.mjs",
+    {
+      code: true,
+      package: true,
+      runtime: true,
+      javascript_recovery: true,
+      readiness: false,
+    },
+  ],
+  [
+    "scripts/lib/runtime-admission.d.mts",
+    {
+      code: true,
+      package: true,
+      runtime: true,
+      javascript_recovery: true,
+      readiness: false,
+    },
+  ],
   [
     "tests/conformance/readiness/report/reconstructionReadiness.ts",
     {
diff --git a/tests/boundary/mcp/deferredRuntime.test.ts b/tests/boundary/mcp/deferredRuntime.test.ts
index 6d7ac54232..693c87fe94 100644
--- a/tests/boundary/mcp/deferredRuntime.test.ts
+++ b/tests/boundary/mcp/deferredRuntime.test.ts
@@ -780,11 +780,15 @@ const copyCompiledPackage = async (prefix: string): Promise<string> => {
   await cp(resolve("dist"), join(directory, "dist"), { recursive: true });
   await mkdir(join(directory, "scripts/lib"), { recursive: true });
   await cp(resolve("scripts/rea.mjs"), join(directory, "scripts/rea.mjs"));
-  // The launcher imports its process-environment owner, as the package ships it.
-  await cp(
-    resolve("scripts/lib/cli-process-environment.mjs"),
-    join(directory, "scripts/lib/cli-process-environment.mjs"),
-  );
+  // Copy the helpers selected by the package, so this fixture exercises the
+  // same launcher files that an installation receives.
+  const manifest = JSON.parse(await readFile("package.json", "utf8")) as {
+    files: string[];
+  };
+  for (const path of manifest.files.filter((file) =>
+    file.startsWith("scripts/lib/"),
+  ))
+    await cp(resolve(path), join(directory, path));
   await cp(resolve("package.json"), join(directory, "package.json"));
   await symlink(
     resolve("node_modules"),