fix: use BigInt arithmetic for nanosecond timestamp conversion

Multiplying Date.getTime() by 1_000_000 as a float before converting
to BigInt causes IEEE 754 precision loss once the product exceeds
Number.MAX_SAFE_INTEGER (~9007T, which ms * 1e6 hits around 2255 AD).

The correct pattern already exists in convertDateToNanoseconds():
  BigInt(date.getTime()) * BigInt(1_000_000)

Apply it consistently to the three call sites that still use the
float-multiply pattern (getNowInNanoseconds, calculateDurationFromStart,
and the runEngineHandlers retry-event recordEvent call).

Author: okxint

.server-changes/fix-otlp-nanosecond-bigint-precision.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: fix
+---
+
+Fix OTLP trace timestamps losing precision for runs after approximately 2255 AD. Timestamps are now computed with full 64-bit integer arithmetic.

apps/webapp/app/v3/eventRepository/common.server.ts

@@ -26,7 +26,7 @@ export function extractContextFromCarrier(carrier: Record<string, unknown>) {
 }
 
 export function getNowInNanoseconds(): bigint {
-  return BigInt(new Date().getTime() * 1_000_000);
+  return BigInt(new Date().getTime()) * BigInt(1_000_000);
 }
 
 export function getDateFromNanoseconds(nanoseconds: bigint): Date {
@@ -40,7 +40,7 @@ export function calculateDurationFromStart(
 ) {
   const $endtime = typeof endTime === "string" ? new Date(endTime) : endTime;
 
-  const duration = Number(BigInt($endtime.getTime() * 1_000_000) - startTime);
+  const duration = Number(BigInt($endtime.getTime()) * BigInt(1_000_000) - startTime);
 
   if (minimumDuration && duration < minimumDuration) {
     return minimumDuration;

apps/webapp/app/v3/eventRepository/index.server.ts

@@ -208,7 +208,7 @@ async function recordRunEvent(
         runId: foundRun.friendlyId,
         ...attributes,
       },
-      startTime: BigInt((startTime?.getTime() ?? Date.now()) * 1_000_000),
+      startTime: BigInt(startTime?.getTime() ?? Date.now()) * BigInt(1_000_000),
       ...optionsRest,
     });
 

apps/webapp/app/v3/runEngineHandlers.server.ts

@@ -557,7 +557,7 @@ export function registerRunEngineEventBusHandlers() {
         );
 
         await eventRepository.recordEvent(retryMessage, {
-          startTime: BigInt(time.getTime() * 1000000),
+          startTime: BigInt(time.getTime()) * BigInt(1_000_000),
           taskSlug: run.taskIdentifier,
           environment,
           attributes: {