chore: import upstream snapshot with attribution

tests/unit/compression-unknown-engine-validation-6485.test.ts

@@ -0,0 +1,45 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import { applyStackedCompression } from "@omniroute/open-sse/services/compression/strategySelector";
+
+// #6485 — a stacked pipeline step naming an engine which is not registered used to
+// silently `continue`, so the caller had no signal that a configured step was a no-op.
+// The fix records a `validationErrors` entry for each unknown engine while still
+// fail-open (the request is not aborted). These tests pin that contract.
+//
+// Note: the unknown-engine path is only reachable via OBJECT steps ({ engine: "…" }).
+// Bare-string steps are coerced to the "caveman" fallback by normalizePipelineStep,
+// so they can never name an unknown engine.
+
+const body = {
+  messages: [
+    { role: "user", content: "hello ".repeat(200) },
+    { role: "assistant", content: "world ".repeat(200) },
+  ],
+};
+
+test("unknown compression engine surfaces a validationErrors entry (sync)", () => {
+  const result = applyStackedCompression(body, [{ engine: "definitely-not-a-real-engine" }]);
+  const errors = result.stats?.validationErrors ?? [];
+  assert.ok(
+    errors.some((e) => e.includes("definitely-not-a-real-engine")),
+    `expected a validationErrors entry naming the unknown engine, got: ${JSON.stringify(errors)}`
+  );
+});
+
+test("known + unknown mixed pipeline reports only the unknown engine (sync)", () => {
+  const result = applyStackedCompression(body, [
+    { engine: "session-dedup" },
+    { engine: "ghost-engine" },
+  ]);
+  const errors = result.stats?.validationErrors ?? [];
+  assert.ok(
+    errors.some((e) => e.includes("ghost-engine")),
+    `expected the unknown engine to be reported, got: ${JSON.stringify(errors)}`
+  );
+  assert.ok(
+    !errors.some((e) => e.includes("session-dedup")),
+    "a real engine must not be reported as unknown"
+  );
+});