diff --git a/src/commands/doctor.ts b/src/commands/doctor.ts
index 6f74efe..505e362 100644
--- a/src/commands/doctor.ts
+++ b/src/commands/doctor.ts
@@ -43,7 +43,11 @@ function formatOverallHealth(summary: DiagnosticSummary): string {
   return 'Overall health: ready.';
 }
 
-function createDefaultDiagnostics(): readonly DiagnosticCheck[] {
+/**
+ * Default doctor checks in their canonical, platform-independent display
+ * order: runtime, source control, Rust toolchain, Stellar CLI, then Docker.
+ */
+export function createDefaultDiagnostics(): readonly DiagnosticCheck[] {
   return [
     ...createRuntimeDiagnostics(),
     createGitDiagnostic(),
diff --git a/src/diagnostics/run.ts b/src/diagnostics/run.ts
index 1297268..e8ccef1 100644
--- a/src/diagnostics/run.ts
+++ b/src/diagnostics/run.ts
@@ -35,16 +35,27 @@ function summarize(results: readonly DiagnosticResult[]): DiagnosticSummary {
   };
 }
 
+/**
+ * Runs diagnostic checks sequentially and returns results in registration
+ * order. Ordering is part of the doctor output contract: results are never
+ * sorted by status, label, or completion time, and a check that throws keeps
+ * its original position as a failed result.
+ */
 export function runDiagnostics(
   checks: readonly DiagnosticCheck[],
 ): DiagnosticReport {
-  const results = checks.map((check) => {
+  // Snapshot the registration order so a caller mutating its own array while
+  // checks run cannot reorder, skip, or duplicate results.
+  const registered = [...checks];
+  const results: DiagnosticResult[] = [];
+
+  for (const check of registered) {
     try {
-      return check.run();
+      results.push(check.run());
     } catch {
-      return failedCheckResult(check);
+      results.push(failedCheckResult(check));
     }
-  });
+  }
 
   return {
     results,
diff --git a/tests/doctor-ordering.test.ts b/tests/doctor-ordering.test.ts
new file mode 100644
index 0000000..9888d60
--- /dev/null
+++ b/tests/doctor-ordering.test.ts
@@ -0,0 +1,202 @@
+import { describe, expect, it } from 'vitest';
+import {
+  createDefaultDiagnostics,
+  createDoctorCommand,
+} from '../src/commands/doctor.js';
+import { runDiagnostics } from '../src/diagnostics/run.js';
+import type {
+  DiagnosticCheck,
+  DiagnosticStatus,
+} from '../src/diagnostics/types.js';
+import { createCapturedTerminalOutput } from './helpers/index.js';
+
+function mockCheck(
+  id: string,
+  status: DiagnosticStatus,
+  remediation?: string,
+): DiagnosticCheck {
+  return {
+    id,
+    label: `Check ${id}`,
+    run: () => ({
+      id,
+      label: `Check ${id}`,
+      status,
+      message: `${id} ${status}`,
+      ...(remediation === undefined ? {} : { remediation }),
+    }),
+  };
+}
+
+function throwingCheck(id: string): DiagnosticCheck {
+  return {
+    id,
+    label: `Check ${id}`,
+    run() {
+      throw new Error('unexpected');
+    },
+  };
+}
+
+function renderDoctor(checks: readonly DiagnosticCheck[]): string[] {
+  const captured = createCapturedTerminalOutput();
+  createDoctorCommand({
+    checks,
+    output: captured.output,
+    setExitCode: () => undefined,
+  }).parse(['node', 'doctor']);
+
+  return captured
+    .stdoutText()
+    .split('\n')
+    .filter((line) => line.length > 0);
+}
+
+describe('doctor result ordering', () => {
+  it('keeps registration order instead of sorting by status or id', () => {
+    const report = runDiagnostics([
+      mockCheck('zeta', 'fail'),
+      mockCheck('alpha', 'pass'),
+      mockCheck('mid', 'warn'),
+      mockCheck('beta', 'pass'),
+    ]);
+
+    expect(report.results.map((result) => result.id)).toEqual([
+      'zeta',
+      'alpha',
+      'mid',
+      'beta',
+    ]);
+  });
+
+  it('keeps a throwing check in its original position', () => {
+    const report = runDiagnostics([
+      mockCheck('first', 'pass'),
+      throwingCheck('broken'),
+      mockCheck('last', 'warn'),
+    ]);
+
+    expect(report.results.map((result) => [result.id, result.status])).toEqual([
+      ['first', 'pass'],
+      ['broken', 'fail'],
+      ['last', 'warn'],
+    ]);
+  });
+
+  it('runs checks sequentially in registration order', () => {
+    const calls: string[] = [];
+    const tracked = (id: string): DiagnosticCheck => ({
+      id,
+      label: id,
+      run() {
+        calls.push(id);
+        return { id, label: id, status: 'pass', message: 'ok' };
+      },
+    });
+
+    runDiagnostics([tracked('c'), tracked('a'), tracked('b')]);
+
+    expect(calls).toEqual(['c', 'a', 'b']);
+  });
+
+  it('is not affected by the caller mutating the check list mid-run', () => {
+    const checks: DiagnosticCheck[] = [];
+    checks.push(
+      {
+        id: 'mutator',
+        label: 'Mutator',
+        run() {
+          checks.reverse();
+          checks.push(mockCheck('late', 'fail'));
+          return {
+            id: 'mutator',
+            label: 'Mutator',
+            status: 'pass',
+            message: 'ok',
+          };
+        },
+      },
+      mockCheck('second', 'warn'),
+      mockCheck('third', 'pass'),
+    );
+
+    const report = runDiagnostics(checks);
+
+    expect(report.results.map((result) => result.id)).toEqual([
+      'mutator',
+      'second',
+      'third',
+    ]);
+  });
+
+  it('produces identical rendered output across repeated runs', () => {
+    const checks = [
+      mockCheck('node', 'pass'),
+      mockCheck('docker', 'warn', 'Start Docker when needed.'),
+      throwingCheck('stellar'),
+      mockCheck('git', 'fail', 'Install Git.'),
+    ];
+
+    const first = renderDoctor(checks);
+
+    for (let run = 0; run < 5; run += 1) {
+      expect(renderDoctor(checks)).toEqual(first);
+    }
+  });
+
+  it('renders each remediation directly under its own result', () => {
+    const lines = renderDoctor([
+      mockCheck('a', 'warn', 'Fix a.'),
+      mockCheck('b', 'pass'),
+      mockCheck('c', 'fail', 'Fix c.'),
+    ]);
+
+    expect(lines).toEqual([
+      '[WARN] Check a: a warn',
+      '  Remediation: Fix a.',
+      '[PASS] Check b: b pass',
+      '[FAIL] Check c: c fail',
+      '  Remediation: Fix c.',
+      'Summary: 1 passed, 1 warnings, 1 failed.',
+      'Overall health: action required.',
+    ]);
+  });
+
+  it('keeps aggregation semantics unchanged when order changes', () => {
+    const checks = [
+      mockCheck('a', 'pass'),
+      mockCheck('b', 'warn'),
+      throwingCheck('c'),
+      mockCheck('d', 'pass'),
+    ];
+
+    const forward = runDiagnostics(checks);
+    const reversed = runDiagnostics([...checks].reverse());
+
+    expect(forward.summary).toEqual({ pass: 2, warn: 1, fail: 1, total: 4 });
+    expect(reversed.summary).toEqual(forward.summary);
+    expect(reversed.results.map((result) => result.id)).toEqual([
+      'd',
+      'c',
+      'b',
+      'a',
+    ]);
+  });
+
+  it('registers default diagnostics in a fixed canonical order', () => {
+    // Only ids are read; no check is run, so no real tool is invoked.
+    const ids = createDefaultDiagnostics().map((check) => check.id);
+
+    expect(ids).toEqual([
+      'node',
+      'npm',
+      'git',
+      'rust',
+      'cargo',
+      'stellar',
+      'docker',
+    ]);
+    expect(new Set(ids).size).toBe(ids.length);
+    expect(createDefaultDiagnostics().map((check) => check.id)).toEqual(ids);
+  });
+});