chore: import upstream snapshot with attribution

tests/unit/compression/compression-preview-api.test.ts

@@ -0,0 +1,65 @@
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+
+import {
+  PreviewCompressionConfigSchema,
+  PreviewRequestSchema,
+} from "../../../src/app/api/compression/preview/route.ts";
+
+describe("compression preview API contract", () => {
+  it("accepts RTK and stacked preview payloads", () => {
+    assert.equal(
+      PreviewRequestSchema.safeParse({
+        messages: [{ role: "tool", content: "same\nsame\nsame" }],
+        mode: "rtk",
+        config: {
+          rtkConfig: {
+            intensity: "standard",
+            applyToToolResults: true,
+            customFiltersEnabled: true,
+            rawOutputRetention: "never",
+          },
+        },
+      }).success,
+      true
+    );
+
+    assert.equal(
+      PreviewRequestSchema.safeParse({
+        messages: [{ role: "tool", content: "same\nsame\nsame" }],
+        mode: "stacked",
+        config: {
+          stackedPipeline: [
+            { engine: "rtk", intensity: "standard" },
+            { engine: "caveman", intensity: "full" },
+          ],
+        },
+      }).success,
+      true
+    );
+  });
+
+  it("rejects invalid preview config instead of accepting arbitrary records", () => {
+    assert.equal(PreviewCompressionConfigSchema.safeParse({ unknown: true }).success, false);
+    assert.equal(
+      PreviewRequestSchema.safeParse({
+        messages: [{ role: "tool", content: "x" }],
+        mode: "rtk",
+        config: { rtkConfig: { intensity: "extreme" } },
+      }).success,
+      false
+    );
+    assert.equal(
+      PreviewCompressionConfigSchema.safeParse({
+        stackedPipeline: [{ engine: "rtk", intensity: "bogus" }],
+      }).success,
+      false
+    );
+    assert.equal(
+      PreviewCompressionConfigSchema.safeParse({
+        stackedPipeline: [{ engine: "rtk", config: { maxLinesPerResult: -1 } }],
+      }).success,
+      false
+    );
+  });
+});