chore: import upstream snapshot with attribution

tests/unit/compression/previewRouteToon.test.ts

@@ -0,0 +1,54 @@
+// tests/unit/compression/previewRouteToon.test.ts
+import test from "node:test";
+import assert from "node:assert/strict";
+import { join } from "node:path";
+import { mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+const TEST_DATA_DIR = mkdtempSync(join(tmpdir(), "preview-toon-"));
+process.env.DATA_DIR = TEST_DATA_DIR;
+process.env.API_KEY_SECRET = process.env.API_KEY_SECRET ?? "test-secret-32-chars-min-aaaaaaaa";
+delete process.env.INITIAL_PASSWORD;
+const core = await import("../../../src/lib/db/core.ts");
+const route = await import("../../../src/app/api/compression/preview/route.ts");
+function makeReq(body: unknown) {
+  return new Request("http://localhost/api/compression/preview", {
+    method: "POST",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+test.beforeEach(() => core.resetDbInstance());
+test.after(() => {
+  core.resetDbInstance();
+  rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+});
+
+test("headroom engine carries encoderComparison with one array and a valid winner", async () => {
+  const big = JSON.stringify(Array.from({ length: 20 }, (_, i) => ({ id: i, ok: true })));
+  const res = await route.POST(
+    makeReq({ messages: [{ role: "user", content: big }], engineId: "headroom" })
+  );
+  assert.equal(res.status, 200);
+  const body = await res.json();
+  assert.ok(body.encoderComparison);
+  assert.equal(body.encoderComparison.arraysCompared, 1);
+  assert.ok(["gcf", "toon", "json"].includes(body.encoderComparison.winner));
+});
+
+test("non-headroom engine (lite) does not carry encoderComparison", async () => {
+  const big = JSON.stringify(Array.from({ length: 20 }, (_, i) => ({ id: i, ok: true })));
+  const res = await route.POST(
+    makeReq({ messages: [{ role: "user", content: big }], engineId: "lite" })
+  );
+  assert.equal(res.status, 200);
+  const body = await res.json();
+  assert.equal(body.encoderComparison ?? null, null);
+});
+
+test("error responses do not leak stack traces", async () => {
+  const res = await route.POST(makeReq({ messages: [] }));
+  assert.equal(res.status, 400);
+  const body = await res.json();
+  const details = JSON.stringify(body);
+  assert.ok(!String(details).includes("at /"));
+});