From 9822ab3a3064e98d0e5d52fcaa50ab7300a8aa68 Mon Sep 17 00:00:00 2001
From: okxint <cashmein.eth@gmail.com>
Date: Tue, 21 Jul 2026 12:31:23 +0530
Subject: [PATCH] fix(events): prevent float precision loss in nanosecond
 timestamp conversion

Multiplying milliseconds by 1_000_000 before BigInt conversion loses precision
because the result (~1.7e18) exceeds Number.MAX_SAFE_INTEGER. Switch all three
call sites to use convertDateToNanoseconds(), which does BigInt(ms) * BigInt(1_000_000)
and keeps the arithmetic in BigInt-land throughout.
---
 .server-changes/fix-bigint-nanosecond-precision.md  | 6 ++++++
 apps/webapp/app/v3/eventRepository/common.server.ts | 4 ++--
 apps/webapp/app/v3/eventRepository/index.server.ts  | 3 ++-
 3 files changed, 10 insertions(+), 3 deletions(-)
 create mode 100644 .server-changes/fix-bigint-nanosecond-precision.md

diff --git a/.server-changes/fix-bigint-nanosecond-precision.md b/.server-changes/fix-bigint-nanosecond-precision.md
new file mode 100644
index 00000000000..2a9f6b9b05a
--- /dev/null
+++ b/.server-changes/fix-bigint-nanosecond-precision.md
@@ -0,0 +1,6 @@
+---
+area: webapp
+type: fix
+---
+
+Timestamp precision is no longer lost when recording nanosecond-resolution span times. Previously, multiplying milliseconds by 1,000,000 in float-land before converting to BigInt produced slightly wrong timestamps for spans and run events.
diff --git a/apps/webapp/app/v3/eventRepository/common.server.ts b/apps/webapp/app/v3/eventRepository/common.server.ts
index eb8bf7f23ec..137a440c3fd 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 convertDateToNanoseconds(new Date());
 }
 
 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($endtime.getTime() * 1_000_000) - startTime);
+  const duration = Number(convertDateToNanoseconds($endtime) - startTime);
 
   if (minimumDuration && duration < minimumDuration) {
     return minimumDuration;
diff --git a/apps/webapp/app/v3/eventRepository/index.server.ts b/apps/webapp/app/v3/eventRepository/index.server.ts
index f0687d2a7ce..29b8d948e24 100644
--- a/apps/webapp/app/v3/eventRepository/index.server.ts
+++ b/apps/webapp/app/v3/eventRepository/index.server.ts
@@ -1,6 +1,7 @@
 import { env } from "~/env.server";
 import { eventRepository } from "./eventRepository.server";
 import { type IEventRepository, type TraceEventOptions } from "./eventRepository.types";
+import { convertDateToNanoseconds } from "./common.server";
 import { prisma } from "~/db.server";
 import { runStore } from "../runStore.server";
 import { controlPlaneResolver } from "~/v3/runOpsMigration/controlPlaneResolver.server";
@@ -240,7 +241,7 @@ async function recordRunEvent(
         runId: foundRun.friendlyId,
         ...attributes,
       },
-      startTime: BigInt((startTime?.getTime() ?? Date.now()) * 1_000_000),
+      startTime: convertDateToNanoseconds(startTime ?? new Date()),
       ...optionsRest,
     });