--- title: "GitHub Reveals Causes of Eight-Hour Outage: Istio Autoscaling Bug and Tenfold Traffic from VS Code" description: "GitHub published a report on the August 17–18 eight-hour outage: the causes were an Istio autoscaling bug and a tenfold traffic increase due to VS Code retry requests." date: 2026-08-19T23:42:33.000Z lang: en url: https://xab.info/en/posts/github-eight-hour-outage-istio-autoscaling-bug-vs-code-traffic tags: [github, vs-code, istio, load-balancer, copilot, outage] publisher: "XAB.info" --- # GitHub Reveals Causes of Eight-Hour Outage: Istio Autoscaling Bug and Tenfold Traffic from VS Code ![GitHub logo amid the eight-hour outage caused by an Istio autoscaling error and a tenfold traffic spike from VS Code](https://xab.info/media/2026/08/20/github-sboy-istio-vs-code/github-sboy-istio-vs-code-1.webp) ## 🎯 Key Points - The GitHub outage on August 17–18, 2026, lasted 7 hours 47 minutes (from 16:28 MSK to 00:15 MSK). - The root cause was the Istio sidecar autoscaling failing to trigger on the load balancers. - A long-standing VS Code bug caused a tenfold increase in traffic to the Copilot Token Service due to retry requests. - GitHub promised an Istio audit, a review of retry limits, and a fix to the autoscaling policy. GitHub's administration published a detailed incident report on the outage that paralyzed the developer platform for nearly eight hours. Service access issues began on August 17, 2026, at 16:28 MSK, and were fully resolved only at 00:15 MSK on August 18. Thus, the total outage duration was 7 hours 47 minutes, during which users reported a rise in errors across various platform services — from the API to CI/CD pipelines and Copilot. ### Root cause: Istio autoscaling failure According to the report, the root cause was network overload on the load balancers at the company's central office in the US. The trigger was reaching the parallel execution limit of the Istio sidecar — a service mesh proxy component. Under normal operation, the system was supposed to automatically increase throughput as these limits were exhausted, but this did not happen due to a misconfigured autoscaling policy: only the host service's state was monitored, not that of the load balancer itself. As a result, throughput was not scaled up, and requests began to accumulate. ### Tenfold traffic due to a VS Code bug The situation was sharply worsened by client behavior: as the service degraded, clients began sending massive numbers of retry requests, which ultimately took the load balancer down. According to engineers, the incident helped uncover a long-standing bug in the Visual Studio Code editor — programs began generating retry requests, causing traffic to the Copilot Token Service to grow tenfold. This led to a significant delay in restoring this particular component. ### How engineers stopped the avalanche To stabilize the system, specialists temporarily reduced the number of gateway retry attempts by changing the code and configured the load balancers to reject incoming requests to the Copilot Token Service with a 403 error code. The phased recovery looked like this: the GitHub Actions service was up by 18:03 MSK on August 17, most other services by 19:36 MSK the same day, and the Copilot Token Service was fully restored only at 0:02 MSK on August 18, after which the incident was officially closed at 00:15 MSK. ### Contradictory data There are inconsistencies in the wording around the incident that are worth noting. In headlines and brief summaries, the outage duration is often rounded to 'eight hours,' whereas the report itself cites the exact figure of 7 hours 47 minutes. In addition, open sources for 2026 mention other GitHub outages (specifically, incidents in June 2026, as well as reports of access issues in certain regions), which are not part of the August 17–18 event under consideration. When reading the news, it is important not to conflate these separate episodes into a single continuous outage. ### What was promised to be fixed The company announced a series of corrective measures: fix the errors in the autoscaling policy, review the limits on the number of retry attempts, audit the Istio parallel access settings, and resolve the VS Code behavior issues that caused traffic to the Copilot Token Service to multiply. These steps are aimed at preventing a repeat of the cascading outage when service mesh limits are reached. ## 🔍 Fact-Check Verification - [GitHub explained the massive outage as a scaling error and a flood of retry requests from VS Code window-new](https://3dnews.ru/1147111/github-obyasnil-masshtabniy-sboy-oshibkoy-masshtabirovaniya-i-shkvalom-povtornih-zaprosov-ot-vs-code) - Первичный источник с полным отчётом GitHub: даты, длительность 7ч47м, причина Istio, ошибка VS Code, этапы восстановления. - [Actions not starting, API down: a new outage paralyzed developers on GitHub](https://www.securitylab.ru/news/575788.php) - Сопутствующее освещение симптомов сбоя (Actions, API), не противоречит отчёту. - [GitHub outage on June 8, 2026: what is known](https://hi-tech.mail.ru/news/149127-sboi-v-rabote-github-8-iyunya-2026-chto-izvestno/) - Описывает иной инцидент (июнь 2026), не является частью рассматриваемого сбоя 17–18 августа; учтено в блоке противоречий. - [A massive outage of Google, Apple, and GitHub occurred in Russia: CPD reported possible new ...](https://zn.ua/TECHNOLOGIES/v-rossii-proizoshel-masshtabnyj-sboj-v-rabote-google-apple-i-github-tspd-soobshchil-o-vozmozhnykh-novykh-blokirovkakh.html) - Связан с региональными блокировками, а не с техническим сбоем платформы; не по теме, не использован как подтверждение. ## ❓ FAQ ### Q: How long did the GitHub outage in August 2026 last? **A:** From 16:28 MSK on August 17 to 00:15 MSK on August 18, i.e., 7 hours 47 minutes (summaries often round it to eight hours). ### Q: What was the main cause of the outage? **A:** Load balancer overload due to the Istio sidecar autoscaling failing to trigger: the policy monitored only the host service, not the state of the load balancer. ### Q: What role did Visual Studio Code play? **A:** A long-standing VS Code bug caused programs to send retry requests, which increased traffic to the Copilot Token Service tenfold and slowed recovery. ### Q: When were the main services restored? **A:** GitHub Actions by 18:03 MSK on August 17, most services by 19:36 MSK, and the Copilot Token Service by 0:02 MSK on August 18. ### Q: What did the company promise as fixes? **A:** Fix the autoscaling policy, review retry limits, audit the Istio settings, and resolve the VS Code behavior issue.