chore: import upstream snapshot with attribution

tests/unit/tool-latency-tracker.test.ts

@@ -0,0 +1,61 @@
+/**
+ * #3173 — cross-request tool latency metrics.
+ *
+ * toolLatencyTracker aggregates per-provider TTFT/gap after tool calls;
+ * sessionManager persists a one-shot tool-finish timestamp so the follow-up
+ * request (Request 2) can measure cross-request TTFT.
+ */
+import test from "node:test";
+import assert from "node:assert/strict";
+
+const {
+  recordToolLatency,
+  getToolLatencyByProvider,
+  recordToolTtft,
+  resetToolLatency,
+} = await import("../../open-sse/services/toolLatencyTracker.ts");
+const { markToolFinish, consumeToolFinishTime } = await import(
+  "../../open-sse/services/sessionManager.ts"
+);
+
+test("recordToolLatency averages TTFT/gap per provider and counts requests", () => {
+  resetToolLatency();
+  recordToolLatency("openai", 100, 40);
+  recordToolLatency("openai", 300, 60);
+  recordToolLatency("anthropic", 200, null);
+
+  const m = getToolLatencyByProvider();
+  assert.equal(m.openai.avgTtftAfterToolMs, 200); // (100+300)/2
+  assert.equal(m.openai.avgGapAfterToolMs, 50); // (40+60)/2
+  assert.equal(m.openai.measurementCount, 2);
+  assert.equal(m.anthropic.avgTtftAfterToolMs, 200);
+  assert.equal(m.anthropic.avgGapAfterToolMs, 0); // no gap samples
+  assert.equal(m.anthropic.measurementCount, 1);
+});
+
+test("recordToolLatency ignores null/negative samples but still counts the request", () => {
+  resetToolLatency();
+  recordToolLatency("glm", null, null);
+  recordToolLatency("glm", -5, -5);
+  const m = getToolLatencyByProvider();
+  assert.equal(m.glm.measurementCount, 2);
+  assert.equal(m.glm.avgTtftAfterToolMs, 0);
+  assert.equal(m.glm.avgGapAfterToolMs, 0);
+});
+
+test("recordToolTtft accumulates and resetToolLatency clears", () => {
+  resetToolLatency();
+  recordToolTtft("codex", 120);
+  recordToolTtft("codex", 80);
+  assert.equal(getToolLatencyByProvider().codex.avgTtftAfterToolMs, 100);
+  resetToolLatency();
+  assert.deepEqual(getToolLatencyByProvider(), {});
+});
+
+test("markToolFinish/consumeToolFinishTime is a one-shot per session", () => {
+  // null session is a no-op / null
+  markToolFinish(null);
+  assert.equal(consumeToolFinishTime(null), null);
+  // unknown session (never touched) → null
+  assert.equal(consumeToolFinishTime("sess-never-seen-xyz"), null);
+});