fix(webapp): prevent OTLP nanosecond timestamp overflow (#3292)

Move BigInt() before multiplication to avoid IEEE 754 precision loss
when converting epoch milliseconds to nanoseconds.

Fixes 4 overflow sites:
- getNowInNanoseconds(): BigInt(Date.now()) * 1_000_000n
- calculateDurationFromStart(): BigInt(getTime()) * 1_000_000n
- recordEvent() startTime: BigInt(getTime()) * 1_000_000n
- runEngineHandlers OOM retry: BigInt(getTime()) * 1_000_000n

Also adds epochMsToNanoseconds() helper to durations.ts for safe
epoch-level conversions, and fixes seed script consistency.

Author: marceli1404

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

@@ -25,7 +25,7 @@ export function extractContextFromCarrier(carrier: Record<string, unknown>) {
 }
 
 export function getNowInNanoseconds(): bigint {
-  return BigInt(new Date().getTime() * 1_000_000);
+  return BigInt(Date.now()) * 1_000_000n;
 }
 
 export function getDateFromNanoseconds(nanoseconds: bigint): Date {
@@ -39,7 +39,7 @@ 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()) * 1_000_000n - startTime);
 
   if (minimumDuration && duration < minimumDuration) {
     return minimumDuration;

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

@@ -240,7 +240,7 @@ async function recordRunEvent(
         runId: foundRun.friendlyId,
         ...attributes,
       },
-      startTime: BigInt((startTime?.getTime() ?? Date.now()) * 1_000_000),
+      startTime: BigInt(startTime?.getTime() ?? Date.now()) * 1_000_000n,
       ...optionsRest,
     });
 

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

@@ -555,7 +555,7 @@ export function registerRunEngineEventBusHandlers() {
         );
 
         await eventRepository.recordEvent(retryMessage, {
-          startTime: BigInt(time.getTime() * 1000000),
+          startTime: BigInt(time.getTime()) * 1_000_000n,
           taskSlug: run.taskIdentifier,
           environment,
           attributes: {

apps/webapp/seed-ai-spans.mts

@@ -474,7 +474,7 @@ function buildAiSpanTree(params: SpanTreeParams): CreateEventInput[] {
     attemptNumber?: number;
   }): CreateEventInput {
     const startNs = BigInt(opts.startMs) * BigInt(1_000_000);
-    const durationNs = opts.durationMs * 1_000_000;
+    const durationNs = BigInt(opts.durationMs) * BigInt(1_000_000);
     return {
       traceId,
       spanId: opts.spanId,

packages/core/src/v3/utils/durations.ts

@@ -32,6 +32,11 @@ export function millisecondsToNanoseconds(milliseconds: number): number {
   return milliseconds * 1_000_000;
 }
 
+/** Convert epoch milliseconds to nanoseconds using BigInt to avoid overflow. */
+export function epochMsToNanoseconds(ms: number): bigint {
+  return BigInt(ms) * 1_000_000n;
+}
+
 export function formatDurationNanoseconds(nanoseconds: number, options?: DurationOptions): string {
   return formatDurationMilliseconds(nanosecondsToMilliseconds(nanoseconds), options);
 }