fix(workbench): keep turn last event timing latest (#2019)

internal/cloud/server-workbench-http.test.ts

@@ -58,6 +58,36 @@ test("workbench projection diagnostics keeps projecting health distinct from cau
   assert.equal(diagnostics.projectionHealth, "projecting");
 });
 
+test("workbench turn projection keeps lastEventAt on the latest event instead of stale admission timing (#1889)", () => {
+  const traceId = "trc_turn_timing_latest_event";
+  const result = {
+    traceId,
+    status: "running",
+    startedAt: "2026-06-23T21:43:48.740Z",
+    lastEventAt: "2026-06-23T21:43:48.740Z",
+    timing: {
+      startedAt: "2026-06-23T21:43:48.740Z",
+      lastEventAt: "2026-06-23T21:43:48.740Z",
+      durationMs: null
+    }
+  };
+  const trace = {
+    traceId,
+    status: "running",
+    updatedAt: "2026-06-23T21:44:33.486Z",
+    lastEventAt: "2026-06-23T21:44:31.000Z",
+    events: [
+      { seq: 1, type: "admitted", createdAt: "2026-06-23T21:43:48.740Z" },
+      { seq: 2, type: "commandExecution", status: "completed", updatedAt: "2026-06-23T21:44:31.000Z" }
+    ],
+    eventCount: 2
+  };
+  const projection = createWorkbenchTurnProjection({ traceId, result, trace });
+  assert.equal(projection.startedAt, "2026-06-23T21:43:48.740Z");
+  assert.equal(projection.lastEventAt, "2026-06-23T21:44:33.486Z");
+  assert.equal(projection.timing.lastEventAt, "2026-06-23T21:44:33.486Z");
+});
+
 test("workbench turn projection treats retryable provider stream disconnect as active", () => {
   const traceId = "trc_retryable_provider_stream_disconnect";
   const result = {

internal/cloud/workbench-turn-projection.ts

@@ -67,7 +67,7 @@ export function createWorkbenchTurnTimingProjection({ result = null, session = n
     firstEvent?.createdAt,
     firstEvent?.occurredAt
   );
-  const lastEventAt = firstTimestamp(
+  const lastEventAt = latestTimestamp(
     result?.lastEventAt,
     directTiming?.lastEventAt,
     trace?.lastEventAt,
@@ -382,6 +382,16 @@ function firstTimestamp(...values) {
   return null;
 }
 
+function latestTimestamp(...values) {
+  let latest = null;
+  for (const value of values) {
+    const ms = Date.parse(String(value ?? ""));
+    if (!Number.isFinite(ms)) continue;
+    latest = latest === null ? ms : Math.max(latest, ms);
+  }
+  return latest === null ? null : new Date(latest).toISOString();
+}
+
 function durationValue(...values) {
   let max = null;
   for (const value of values) {