From a87496b381ed096dc06d8cd5e65cddf8ac554a39 Mon Sep 17 00:00:00 2001
From: ANSHSINGH050404 <114014895+ANSHSINGH050404@users.noreply.github.com>
Date: Mon, 20 Jul 2026 12:23:24 +0530
Subject: [PATCH] fix(webapp): convert epoch-ms to BigInt before nanosecond
 multiply

Avoids IEEE 754 precision loss when ms * 1e6 exceeds Number.MAX_SAFE_INTEGER.

Closes #3292
---
 .server-changes/fix-otlp-nanosecond-overflow.md     | 6 ++++++
 apps/webapp/app/v3/eventRepository/common.server.ts | 4 ++--
 apps/webapp/app/v3/runEngineHandlers.server.ts      | 2 +-
 3 files changed, 9 insertions(+), 3 deletions(-)
 create mode 100644 .server-changes/fix-otlp-nanosecond-overflow.md

diff --git a/.server-changes/fix-otlp-nanosecond-overflow.md b/.server-changes/fix-otlp-nanosecond-overflow.md
new file mode 100644
index 00000000000..b895deffc11
--- /dev/null
+++ b/.server-changes/fix-otlp-nanosecond-overflow.md
@@ -0,0 +1,6 @@
+---
+area: webapp
+type: fix
+---
+
+Improve accuracy of run timeline timestamps by converting times to nanoseconds without floating-point rounding errors.
diff --git a/apps/webapp/app/v3/eventRepository/common.server.ts b/apps/webapp/app/v3/eventRepository/common.server.ts
index eb8bf7f23ec..b16518beae5 100644
--- a/apps/webapp/app/v3/eventRepository/common.server.ts
+++ b/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(new Date().getTime()) * BigInt(1_000_000);
 }
 
 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()) * BigInt(1_000_000) - startTime);
 
   if (minimumDuration && duration < minimumDuration) {
     return minimumDuration;
diff --git a/apps/webapp/app/v3/runEngineHandlers.server.ts b/apps/webapp/app/v3/runEngineHandlers.server.ts
index c44bcc54cec..0d83aad8e2a 100644
--- a/apps/webapp/app/v3/runEngineHandlers.server.ts
+++ b/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()) * BigInt(1_000_000),
           taskSlug: run.taskIdentifier,
           environment,
           attributes: {