diff --git a/.changeset/runtime-doctor-diagnostics.md b/.changeset/runtime-doctor-diagnostics.md
new file mode 100644
index 0000000..4f57062
--- /dev/null
+++ b/.changeset/runtime-doctor-diagnostics.md
@@ -0,0 +1,5 @@
+---
+"@stellarforge/cli": minor
+---
+
+Add Node.js and npm environment checks to `stellarforge doctor` with supported-version validation and actionable remediation guidance.
diff --git a/src/commands/doctor.ts b/src/commands/doctor.ts
index d95ab97..f9c14e6 100644
--- a/src/commands/doctor.ts
+++ b/src/commands/doctor.ts
@@ -1,6 +1,7 @@
 import { Command } from 'commander';
 import { EXIT_CODES } from '../errors/errors.js';
 import { runDiagnostics } from '../diagnostics/run.js';
+import { createRuntimeDiagnostics } from '../diagnostics/runtime.js';
 import type {
   DiagnosticCheck,
   DiagnosticReport,
@@ -42,7 +43,7 @@ export function renderDiagnosticReport(
 export function createDoctorCommand(
   options: DoctorCommandOptions = {},
 ): Command {
-  const checks = options.checks ?? [];
+  const checks = options.checks ?? createRuntimeDiagnostics();
   const output = options.output ?? new TerminalOutput();
   const setExitCode =
     options.setExitCode ?? ((code) => (process.exitCode = code));
diff --git a/src/diagnostics/process.ts b/src/diagnostics/process.ts
new file mode 100644
index 0000000..93a5431
--- /dev/null
+++ b/src/diagnostics/process.ts
@@ -0,0 +1,27 @@
+import { spawnSync } from 'node:child_process';
+
+export interface CommandResult {
+  readonly status: number | null;
+  readonly stdout: string;
+  readonly stderr: string;
+  readonly error?: Error;
+}
+
+export type RunCommand = (
+  executable: string,
+  args: readonly string[],
+) => CommandResult;
+
+export const runCommand: RunCommand = (executable, args) => {
+  const result = spawnSync(executable, [...args], {
+    encoding: 'utf8',
+    shell: false,
+  });
+
+  return {
+    status: result.status,
+    stdout: result.stdout ?? '',
+    stderr: result.stderr ?? '',
+    ...(result.error === undefined ? {} : { error: result.error }),
+  };
+};
diff --git a/src/diagnostics/runtime.ts b/src/diagnostics/runtime.ts
new file mode 100644
index 0000000..8df6d7a
--- /dev/null
+++ b/src/diagnostics/runtime.ts
@@ -0,0 +1,114 @@
+import type { DiagnosticCheck, DiagnosticResult } from './types.js';
+import { runCommand, type RunCommand } from './process.js';
+import {
+  compareVersions,
+  isAtLeast,
+  parseNumericVersion,
+  type NumericVersion,
+} from './version.js';
+
+const MINIMUM_NODE: NumericVersion = { major: 22, minor: 13, patch: 0 };
+const MAXIMUM_NODE_MAJOR = 25;
+const MINIMUM_NPM: NumericVersion = { major: 10, minor: 9, patch: 0 };
+
+function failure(
+  id: string,
+  label: string,
+  message: string,
+  remediation: string,
+): DiagnosticResult {
+  return { id, label, status: 'fail', message, remediation };
+}
+
+export function createNodeDiagnostic(
+  nodeVersion = process.versions.node,
+): DiagnosticCheck {
+  return {
+    id: 'node',
+    label: 'Node.js',
+    run(): DiagnosticResult {
+      const parsed = parseNumericVersion(nodeVersion);
+
+      if (!parsed) {
+        return failure(
+          'node',
+          'Node.js',
+          'Could not determine a valid Node.js version.',
+          'Install a supported Node.js release (>=22.13.0 and <25).',
+        );
+      }
+
+      if (
+        !isAtLeast(parsed, MINIMUM_NODE) ||
+        parsed.major >= MAXIMUM_NODE_MAJOR
+      ) {
+        return failure(
+          'node',
+          'Node.js',
+          `Unsupported Node.js version ${nodeVersion}.`,
+          'Use Node.js >=22.13.0 and <25.',
+        );
+      }
+
+      return {
+        id: 'node',
+        label: 'Node.js',
+        status: 'pass',
+        message: `Supported version ${nodeVersion} detected.`,
+      };
+    },
+  };
+}
+
+export function createNpmDiagnostic(
+  execute: RunCommand = runCommand,
+): DiagnosticCheck {
+  return {
+    id: 'npm',
+    label: 'npm',
+    run(): DiagnosticResult {
+      const result = execute('npm', ['--version']);
+
+      if (result.error || result.status !== 0) {
+        return failure(
+          'npm',
+          'npm',
+          'npm is unavailable or could not be executed.',
+          'Install npm >=10.9.0 and ensure it is available on PATH.',
+        );
+      }
+
+      const version = result.stdout.trim();
+      const parsed = parseNumericVersion(version);
+
+      if (!parsed) {
+        return failure(
+          'npm',
+          'npm',
+          'npm returned an unrecognized version.',
+          'Install npm >=10.9.0 and verify `npm --version` returns a numeric version.',
+        );
+      }
+
+      if (compareVersions(parsed, MINIMUM_NPM) < 0) {
+        return failure(
+          'npm',
+          'npm',
+          `Unsupported npm version ${version}.`,
+          'Upgrade to npm >=10.9.0.',
+        );
+      }
+
+      return {
+        id: 'npm',
+        label: 'npm',
+        status: 'pass',
+        message: `Supported version ${version} detected.`,
+      };
+    },
+  };
+}
+
+export function createRuntimeDiagnostics(): readonly DiagnosticCheck[] {
+  return [createNodeDiagnostic(), createNpmDiagnostic()];
+}
diff --git a/src/diagnostics/version.ts b/src/diagnostics/version.ts
new file mode 100644
index 0000000..9185b34
--- /dev/null
+++ b/src/diagnostics/version.ts
@@ -0,0 +1,35 @@
+export interface NumericVersion {
+  readonly major: number;
+  readonly minor: number;
+  readonly patch: number;
+}
+
+export function parseNumericVersion(value: string): NumericVersion | null {
+  const match = /^(\d+)\.(\d+)\.(\d+)(?:[-+].*)?$/.exec(value.trim());
+
+  if (!match) return null;
+
+  const major = Number(match[1]);
+  const minor = Number(match[2]);
+  const patch = Number(match[3]);
+
+  if (![major, minor, patch].every(Number.isSafeInteger)) return null;
+
+  return { major, minor, patch };
+}
+
+export function compareVersions(
+  left: NumericVersion,
+  right: NumericVersion,
+): number {
+  if (left.major !== right.major) return left.major - right.major;
+  if (left.minor !== right.minor) return left.minor - right.minor;
+  return left.patch - right.patch;
+}
+
+export function isAtLeast(
+  actual: NumericVersion,
+  minimum: NumericVersion,
+): boolean {
+  return compareVersions(actual, minimum) >= 0;
+}
diff --git a/tests/doctor.test.ts b/tests/doctor.test.ts
index 4f44656..2ac938e 100644
--- a/tests/doctor.test.ts
+++ b/tests/doctor.test.ts
@@ -25,10 +25,11 @@ function check(
 }
 
 describe('doctor command', () => {
-  it('renders an empty scaffold without failing', () => {
+  it('renders an empty scaffold without failing when checks are explicitly empty', () => {
     const captured = createCapturedTerminalOutput();
     let exitCode = -1;
     const command = createDoctorCommand({
+      checks: [],
       output: captured.output,
       setExitCode: (code) => {
         exitCode = code;
diff --git a/tests/executable.test.ts b/tests/executable.test.ts
index 01e6c3c..81c5a10 100644
--- a/tests/executable.test.ts
+++ b/tests/executable.test.ts
@@ -42,11 +42,22 @@ describe('StellarForge CLI executable', () => {
 
     expect(result.status).toBe(0);
     expect(result.stderr).toBe('');
-    expect(result.stdout).toContain('Usage: stellarforge [options]');
+    expect(result.stdout).toContain('Usage: stellarforge [options] [command]');
+    expect(result.stdout).toContain('doctor');
     expect(result.stdout).toContain('-h, --help');
     expect(result.stdout).toContain('-V, --version');
   });
 
+  it('runs the default runtime doctor checks successfully in the supported toolchain', () => {
+    const result = runBuiltCli(['doctor']);
+
+    expect(result.status).toBe(0);
+    expect(result.stderr).toBe('');
+    expect(result.stdout).toContain('[PASS] Node.js:');
+    expect(result.stdout).toContain('[PASS] npm:');
+    expect(result.stdout).toContain('Summary: 2 passed, 0 warnings, 0 failed.');
+  });
+
   it('prints the package version from the built executable', () => {
     const packageJson = JSON.parse(readFileSync(packageJsonPath, 'utf8')) as {
       version: string;
diff --git a/tests/runtime-diagnostics.test.ts b/tests/runtime-diagnostics.test.ts
new file mode 100644
index 0000000..db00c93
--- /dev/null
+++ b/tests/runtime-diagnostics.test.ts
@@ -0,0 +1,100 @@
+import { describe, expect, it } from 'vitest';
+import {
+  createNodeDiagnostic,
+  createNpmDiagnostic,
+} from '../src/diagnostics/runtime.js';
+import type { RunCommand } from '../src/diagnostics/process.js';
+
+function commandResult(
+  status: number | null,
+  stdout = '',
+  stderr = '',
+  error?: Error,
+) {
+  return {
+    status,
+    stdout,
+    stderr,
+    ...(error === undefined ? {} : { error }),
+  };
+}
+
+describe('Node.js diagnostic', () => {
+  it('passes a supported Node.js version', () => {
+    const result = createNodeDiagnostic('22.13.0').run();
+
+    expect(result.status).toBe('pass');
+    expect(result.message).toContain('22.13.0');
+  });
+
+  it('fails versions below the supported minimum', () => {
+    const result = createNodeDiagnostic('22.12.9').run();
+
+    expect(result.status).toBe('fail');
+    expect(result.remediation).toContain('>=22.13.0');
+  });
+
+  it('fails Node.js 25 and newer', () => {
+    const result = createNodeDiagnostic('25.0.0').run();
+
+    expect(result.status).toBe('fail');
+    expect(result.remediation).toContain('<25');
+  });
+
+  it('fails malformed versions without throwing', () => {
+    const result = createNodeDiagnostic('unknown').run();
+
+    expect(result.status).toBe('fail');
+    expect(result.message).toContain('valid Node.js version');
+  });
+});
+
+describe('npm diagnostic', () => {
+  it('executes npm with an argument array and passes a supported version', () => {
+    const calls: Array<{ executable: string; args: readonly string[] }> = [];
+    const execute: RunCommand = (executable, args) => {
+      calls.push({ executable, args });
+      return commandResult(0, '10.9.2\n');
+    };
+
+    const result = createNpmDiagnostic(execute).run();
+
+    expect(calls).toEqual([{ executable: 'npm', args: ['--version'] }]);
+    expect(result.status).toBe('pass');
+    expect(result.message).toContain('10.9.2');
+  });
+
+  it('fails when npm is unavailable without exposing subprocess details', () => {
+    const execute: RunCommand = () =>
+      commandResult(
+        null,
+        '',
+        'SECRET_TOKEN=do-not-render',
+        new Error('spawn npm ENOENT SECRET_TOKEN=do-not-render'),
+      );
+
+    const result = createNpmDiagnostic(execute).run();
+
+    expect(result.status).toBe('fail');
+    expect(result.message).toBe('npm is unavailable or could not be executed.');
+    expect(JSON.stringify(result)).not.toContain('SECRET_TOKEN');
+  });
+
+  it('fails npm versions below the supported minimum', () => {
+    const execute: RunCommand = () => commandResult(0, '10.8.9\n');
+
+    const result = createNpmDiagnostic(execute).run();
+
+    expect(result.status).toBe('fail');
+    expect(result.remediation).toContain('>=10.9.0');
+  });
+
+  it('fails unrecognized npm version output', () => {
+    const execute: RunCommand = () => commandResult(0, 'npm unknown\n');
+
+    const result = createNpmDiagnostic(execute).run();
+
+    expect(result.status).toBe('fail');
+    expect(result.message).toBe('npm returned an unrecognized version.');
+  });
+});