diff --git a/docs/ts-migration-baseline.md b/docs/ts-migration-baseline.md
new file mode 100644
index 00000000..214c4472
--- /dev/null
+++ b/docs/ts-migration-baseline.md
@@ -0,0 +1,50 @@
+<!--
+SPDX-FileCopyrightText: 2026 Stan Grams <sjg@haxx.space>
+
+SPDX-License-Identifier: GPL-2.0-or-later
+-->
+
+# TypeScript migration baseline
+
+This baseline records the browser architecture at the start of the migration.
+It is intentionally historical; generated output sizes are tracked separately
+by the deterministic frontend build.
+
+## Startup order
+
+The initial document loads these scripts in order:
+
+1. `/vendor/opus-decoder-0.7.11.min.js`
+2. `/vendor/leaflet.js`
+3. `/leaflet-ais-tracksymbol.js`
+4. `/webgl-renderer.js`
+5. `/ui-core.js`
+6. `/app.js`
+
+Decoder and feature scripts are then loaded lazily by the inline loader in
+`index.html`. The frontend smoke test locks the core ordering and rejects
+remote script or stylesheet URLs.
+
+## Source measurements
+
+At baseline, first-party JavaScript comprised 23 files and approximately
+776 KiB. The largest sources were:
+
+| Source | Bytes |
+|---|---:|
+| `app.js` | 337,111 |
+| `map-core.js` | 131,899 |
+| `plugins/scheduler.js` | 60,883 |
+| `plugins/bookmarks.js` | 30,543 |
+| `plugins/sat.js` | 22,541 |
+| `plugins/vchan.js` | 20,195 |
+| `webgl-renderer.js` | 18,993 |
+
+The migrated source snapshot contained 123 distinct direct `window.*`
+assignments. These are compatibility callbacks, shared state, and plugin entry
+points. New TypeScript code must not add to that set; the typed plugin registry
+and explicit services replace it over the course of the migration.
+
+All production scripts, stylesheets, fonts, icons, and map assets were already
+served from local embedded routes. The automated startup test ensures no
+remote runtime script or stylesheet dependency is introduced.
diff --git a/src/trx-client/trx-frontend/trx-frontend-http/frontend/tests/smoke.test.mjs b/src/trx-client/trx-frontend/trx-frontend-http/frontend/tests/smoke.test.mjs
index 517348e1..6fa1f158 100644
--- a/src/trx-client/trx-frontend/trx-frontend-http/frontend/tests/smoke.test.mjs
+++ b/src/trx-client/trx-frontend/trx-frontend-http/frontend/tests/smoke.test.mjs
@@ -6,7 +6,21 @@ import assert from "node:assert/strict";
 import test from "node:test";
 import { readFile } from "node:fs/promises";
 
+const indexPath = new URL("../../assets/web/index.html", import.meta.url);
+
 test("index loads the shared UI before the application", async () => {
-  const html = await readFile(new URL("../../assets/web/index.html", import.meta.url), "utf8");
+  const html = await readFile(indexPath, "utf8");
   assert.ok(html.indexOf("/ui-core.js") < html.indexOf("/app.js"));
 });
+
+test("startup has no remote script or stylesheet dependencies", async () => {
+  const html = await readFile(indexPath, "utf8");
+  const assetReferences = Array.from(
+    html.matchAll(/<(?:script|link)\b[^>]+(?:src|href)="([^"]+)"/g),
+    (match) => match[1],
+  );
+  assert.equal(
+    assetReferences.some((reference) => /^https?:\/\//i.test(reference)),
+    false,
+  );
+});