chore: import upstream snapshot with attribution

tests/unit/chatcore-compression-cache-stats.test.ts

@@ -0,0 +1,90 @@
+// Characterization of recordCompressionCacheStats — the compression cache-stats hook extracted
+// from handleChatCore's request-setup compression path (chatCore god-file decomposition, #3501).
+// Fire-and-forget; uses a real temp DB and polls compression_cache_stats. Locks: a compressed
+// prompt records a cache-stats row with the resolved provider/mode/tokens-saved, and the helper
+// returns synchronously without throwing (fail-open).
+import { test, before, after } from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+const testDataDir = fs.mkdtempSync(path.join(os.tmpdir(), "omni-comp-cache-test-"));
+process.env.DATA_DIR = testDataDir;
+
+const coreDb = await import("../../src/lib/db/core.ts");
+const { recordCompressionCacheStats } = await import(
+  "../../open-sse/handlers/chatCore/compressionCacheStats.ts"
+);
+
+function rowsFor(provider: string): Array<Record<string, unknown>> {
+  return coreDb
+    .getDbInstance()
+    .prepare(
+      "SELECT provider, compression_mode AS mode, tokens_saved_compression AS saved FROM compression_cache_stats WHERE provider = ?"
+    )
+    .all(provider) as Array<Record<string, unknown>>;
+}
+
+async function waitForRows(provider: string, min: number, timeoutMs = 3000) {
+  const deadline = Date.now() + timeoutMs;
+  while (Date.now() < deadline) {
+    if (rowsFor(provider).length >= min) break;
+    await new Promise((r) => setTimeout(r, 25));
+  }
+  return rowsFor(provider);
+}
+
+before(async () => {
+  await coreDb.ensureDbInitialized();
+});
+
+after(() => {
+  coreDb.resetDbInstance();
+  try {
+    fs.rmSync(testDataDir, { recursive: true, force: true });
+  } catch {
+    // best-effort cleanup
+  }
+});
+
+test("returns synchronously without throwing (fire-and-forget)", () => {
+  assert.doesNotThrow(() =>
+    recordCompressionCacheStats({
+      compressionInputBody: { messages: [{ role: "user", content: "hi" }] },
+      provider: "openai",
+      targetFormat: "openai",
+      effectiveModel: "gpt-x",
+      mode: "balanced",
+      stats: { originalTokens: 100, compressedTokens: 60 },
+    })
+  );
+});
+
+test("records a cache-stats row with the resolved provider/mode/tokens-saved", async () => {
+  recordCompressionCacheStats({
+    compressionInputBody: { messages: [{ role: "user", content: "hello world" }] },
+    provider: "ccs-prov",
+    targetFormat: "openai",
+    effectiveModel: "gpt-ccs",
+    mode: "aggressive",
+    stats: { originalTokens: 200, compressedTokens: 75 },
+  });
+  const rows = await waitForRows("ccs-prov", 1);
+  assert.equal(rows.length, 1);
+  assert.equal(rows[0].mode, "aggressive");
+  assert.equal(rows[0].saved, 125);
+});
+
+test("clamps negative tokens-saved to 0", async () => {
+  recordCompressionCacheStats({
+    compressionInputBody: { messages: [] },
+    provider: "ccs-neg",
+    targetFormat: "openai",
+    effectiveModel: "gpt-x",
+    mode: "balanced",
+    stats: { originalTokens: 50, compressedTokens: 80 },
+  });
+  const rows = await waitForRows("ccs-neg", 1);
+  assert.equal(rows[0].saved, 0);
+});