diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4ac1399..69814d2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - **ci**: `.nvmrc` now pins Node 24, matching the CI matrix. It still read `20`, so `nvm use` handed local developers a runtime that cannot load `node:sqlite` and does not satisfy `commander`'s `engines.node >=22.12.0`.
+- **build**: `npm run build` now runs a `clean` step first, removing `dist/` and `tsconfig.tsbuildinfo` before compiling. Without it, `tsc` leaves output for sources that no longer exist, so a file rename could ship stale artifacts — verified reproducible: planting `dist/sync/strings-client.js` and rebuilding left both files in `npm pack` output. Removing the build-info file is required too; deleting only `dist/` makes the incremental compiler report the output as up to date and emit nothing.
 - **deps**: `commander` 14.0.3 → 15.0.0. commander 15 is ESM-only (`"type": "module"`) and requires Node >=22.12.0, so it was unmergeable until the Node 24 baseline landed. Jest's `transformIgnorePatterns` allowlist gains `commander` so ts-jest transforms it under CommonJS test execution; without that, 28 suites fail to load with `SyntaxError: Cannot use import statement outside a module`.
 - **ci**: Test matrix, release workflow, and security workflow now target Node 24 (previously Node 20 and 22). Node 20 reached end-of-life in April 2026, and Node 24 is the current LTS. This aligns CI with the runtime the project is moving to; the `engines.node` range is unchanged in this entry and is bumped separately.
 
diff --git a/package.json b/package.json
index b05af8d..3ebf534 100644
--- a/package.json
+++ b/package.json
@@ -24,7 +24,8 @@
   },
   "scripts": {
     "dev": "ts-node src/cli/index.ts",
-    "build": "tsc && chmod +x dist/cli/index.js",
+    "clean": "rm -rf dist tsconfig.tsbuildinfo",
+    "build": "npm run clean && tsc && chmod +x dist/cli/index.js",
     "test": "jest",
     "test:watch": "jest --watch",
     "test:coverage": "jest --coverage",
diff --git a/tests/unit/package-manifest.test.ts b/tests/unit/package-manifest.test.ts
new file mode 100644
index 0000000..32a9ed4
--- /dev/null
+++ b/tests/unit/package-manifest.test.ts
@@ -0,0 +1,71 @@
+/**
+ * Tests for package.json publish-surface invariants
+ *
+ * These guard properties that are easy to lose in a merge and expensive to
+ * lose silently: the `clean` script was previously added, lost, and only
+ * rediscovered when a stale `dist/` was found reaching `npm pack`.
+ */
+
+import * as fs from 'fs';
+import * as path from 'path';
+
+interface PackageManifest {
+  scripts: {
+    clean?: string;
+    build: string;
+    prepublishOnly: string;
+  };
+  files: string[];
+  bin: Record<string, string>;
+}
+
+describe('package.json manifest', () => {
+  let pkg: PackageManifest;
+
+  beforeAll(() => {
+    const manifestPath = path.join(__dirname, '..', '..', 'package.json');
+    pkg = JSON.parse(fs.readFileSync(manifestPath, 'utf-8')) as PackageManifest;
+  });
+
+  describe('clean script', () => {
+    it('should define a clean script', () => {
+      expect(pkg.scripts.clean).toBeDefined();
+    });
+
+    it('should remove dist so renames cannot leak stale output to npm publish', () => {
+      expect(pkg.scripts.clean).toContain('dist');
+    });
+
+    it('should remove the TypeScript build info file', () => {
+      // Without this, tsc's incremental cache reports the deleted output as
+      // up-to-date and emits nothing, leaving dist empty after a clean.
+      expect(pkg.scripts.clean).toContain('tsbuildinfo');
+    });
+  });
+
+  describe('build script', () => {
+    it('should run clean before compiling', () => {
+      expect(pkg.scripts.build).toMatch(/^npm run clean &&/);
+    });
+
+    it('should make the CLI entrypoint executable', () => {
+      expect(pkg.scripts.build).toContain('chmod +x');
+    });
+  });
+
+  describe('publish surface', () => {
+    it('should rebuild from scratch before publishing', () => {
+      expect(pkg.scripts.prepublishOnly).toContain('build');
+    });
+
+    it('should exclude source maps and build info from the tarball', () => {
+      const excluded = pkg.files.filter((entry) => entry.startsWith('!'));
+      expect(excluded).toContain('!dist/**/*.tsbuildinfo');
+      expect(excluded).toContain('!dist/**/*.js.map');
+    });
+
+    it('should point bin at a path inside dist', () => {
+      expect(Object.values(pkg.bin).every((target) => target.startsWith('dist/'))).toBe(true);
+    });
+  });
+});