diff --git a/package.json b/package.json
index 18e4d0f0d..5ab3242fb 100644
--- a/package.json
+++ b/package.json
@@ -33,6 +33,7 @@
 		"audit:complexity": "node scripts/audit-complexity.mjs",
 		"audit:map": "node scripts/build-complexity-map.mjs",
 		"audit:i18n-coverage": "node scripts/audit-i18n-coverage.mjs",
+		"audit:port-drift": "node scripts/audit-port-drift.mjs",
 		"generate:dockerfiles": "node scripts/generate-dockerfiles.mjs",
 		"setup:env": "node scripts/generate-env.mjs",
 		"setup:secrets": "node scripts/setup-secrets.mjs",
diff --git a/scripts/audit-port-drift.mjs b/scripts/audit-port-drift.mjs
new file mode 100644
index 000000000..562cb7eb1
--- /dev/null
+++ b/scripts/audit-port-drift.mjs
@@ -0,0 +1,155 @@
+#!/usr/bin/env node
+/**
+ * Audit port declarations: each services/*\/CLAUDE.md declares `## Port:
+ * NNNN`. Verify that the same port appears as a literal in the service's
+ * source code, and that no two services claim the same port.
+ *
+ * docs/PORT_SCHEMA.md is explicitly "partially aspirational" as of
+ * 2026-04-08, so the authoritative source is each service's own
+ * CLAUDE.md. This audit catches drift where a service moves its port in
+ * code but forgets to update its CLAUDE.md, or where two services
+ * accidentally claim the same number.
+ *
+ * Checks:
+ *   1. Parse `## Port: NNNN` from every `services/*\/CLAUDE.md`.
+ *   2. Grep the service directory (ignoring node_modules / dist / build /
+ *      .turbo / __pycache__) for the literal port number.
+ *      - Pass  : declared port found in code.
+ *      - Flag  : not found — either a doc typo or outdated doc.
+ *   3. Cross-check: build a port → service map and flag collisions.
+ *
+ * Usage:
+ *   node scripts/audit-port-drift.mjs
+ */
+
+import { readdirSync, readFileSync, existsSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { dirname, join } from 'node:path';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const REPO_ROOT = join(__dirname, '..');
+const SERVICES_DIR = join(REPO_ROOT, 'services');
+
+const SKIP_DIRS = new Set([
+	'node_modules',
+	'dist',
+	'build',
+	'.turbo',
+	'.svelte-kit',
+	'__pycache__',
+	'.venv',
+	'venv',
+	'.next',
+	'target', // rust
+]);
+
+function parseCLAUDEPort(mdPath) {
+	const src = readFileSync(mdPath, 'utf8');
+	const m = src.match(/^##\s+Port:\s+(\d{4,5})\s*$/m);
+	return m ? Number(m[1]) : null;
+}
+
+/** True if any tracked source file under `dir` contains `port` as a
+ *  digit-boundary match (avoids matching 3050 inside 30500, etc.). */
+function portAppearsIn(dir, port) {
+	const portStr = String(port);
+	const re = new RegExp(`\\b${portStr}\\b`);
+	function walk(d) {
+		for (const ent of readdirSync(d, { withFileTypes: true })) {
+			if (ent.name.startsWith('.') && ent.name !== '.env.example') continue;
+			if (SKIP_DIRS.has(ent.name)) continue;
+			const p = join(d, ent.name);
+			if (ent.isDirectory()) {
+				if (walk(p)) return true;
+			} else if (ent.isFile()) {
+				// Only scan source-ish files; skip binaries + lockfiles.
+				if (/\.(ts|tsx|js|mjs|cjs|go|py|env|env\.example|yaml|yml|toml|json|md)$/.test(ent.name)) {
+					try {
+						const src = readFileSync(p, 'utf8');
+						if (re.test(src)) return true;
+					} catch {
+						// Unreadable file — skip.
+					}
+				}
+			}
+		}
+		return false;
+	}
+	return walk(dir);
+}
+
+function audit() {
+	const entries = readdirSync(SERVICES_DIR, { withFileTypes: true }).filter((e) => e.isDirectory());
+
+	const declared = []; // { service, port, mdPath }
+	const missingCLAUDE = []; // service names
+
+	for (const ent of entries) {
+		const mdPath = join(SERVICES_DIR, ent.name, 'CLAUDE.md');
+		if (!existsSync(mdPath)) {
+			missingCLAUDE.push(ent.name);
+			continue;
+		}
+		const port = parseCLAUDEPort(mdPath);
+		if (port === null) continue; // service without a single-port concept (e.g. library service)
+		declared.push({ service: ent.name, port, mdPath });
+	}
+
+	const drifts = [];
+	for (const d of declared) {
+		const serviceDir = join(SERVICES_DIR, d.service);
+		const found = portAppearsIn(serviceDir, d.port);
+		if (!found) drifts.push(d);
+	}
+
+	const byPort = new Map();
+	for (const d of declared) {
+		if (!byPort.has(d.port)) byPort.set(d.port, []);
+		byPort.get(d.port).push(d.service);
+	}
+	const collisions = [...byPort.entries()].filter(([, list]) => list.length > 1);
+
+	console.log(`\n── Port drift audit ───────────────────────────────────\n`);
+	console.log(`Services with CLAUDE.md Port declaration: ${declared.length}`);
+	console.log(`Services without CLAUDE.md: ${missingCLAUDE.length}`);
+	console.log('');
+
+	if (drifts.length === 0 && collisions.length === 0) {
+		console.log(`✓ No drift: every declared port appears in its own service's source.`);
+		console.log(`✓ No collisions: all ${declared.length} port assignments unique.`);
+	}
+
+	if (drifts.length > 0) {
+		console.log(`✗ Drift: declared port not found in service source (${drifts.length}):\n`);
+		for (const d of drifts) {
+			console.log(
+				`  ${d.service}  declared :${d.port}  — not found in ${d.mdPath.slice(REPO_ROOT.length + 1)}`
+			);
+		}
+		console.log('');
+	}
+
+	if (collisions.length > 0) {
+		console.log(`✗ Collisions: multiple services claim the same port (${collisions.length}):\n`);
+		for (const [port, list] of collisions) {
+			console.log(`  :${port}  ${list.join(', ')}`);
+		}
+		console.log('');
+	}
+
+	console.log(`Port map:\n`);
+	for (const d of declared.slice().sort((a, b) => a.port - b.port)) {
+		console.log(`  :${d.port}  ${d.service}`);
+	}
+	console.log('');
+
+	if (missingCLAUDE.length > 0) {
+		console.log(`Services without CLAUDE.md (no port declared):`);
+		for (const name of missingCLAUDE) console.log(`  ${name}`);
+		console.log('');
+	}
+
+	// Report-only: never exit non-zero. This is diagnostic, not a gate.
+}
+
+audit();