ChatGPT, Claude, Grok, and Gemini all had trouble inside the same two hours on September 3

Individually, each of these incidents is a normal bad morning. Together they are the case that most fallback plans quietly assume cannot happen: four separate vendors degrading inside the same two hours, with no shared cloud outage underneath to explain it.

What the status pages actually recorded

Anthropic's incident history shows an entry titled elevated errors for multiple models on September 3, 2026, running from 13:26 to 16:23 UTC, with impact ending at 16:16 UTC. Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 are named. A separate, shorter entry covers elevated errors on Claude Sonnet 5 from 12:37 to 12:56 UTC the same day.

OpenAI's history shows elevated errors across ChatGPT and Codex, marked resolved, with one operational footnote worth reading if you use Codex remotely: some remote-control users may need to pair their mobile device again after the incident. That is the kind of aftershock that outlives the outage itself.

Grok and Gemini are the less certain half

Neither xAI nor Google published an incident that Ars Technica could point to, so this half of the story rests on user reports and third-party monitoring rather than on the vendors. Ars reports that DownDetector submissions for Grok rose from fewer than 10 shortly before 9 am Eastern to 1,365 by 9:45 am, and that Gemini reports went from 23 around 10:30 am to 412 just after 11. It also cites StatusGator recording what that service calls a likely outage of the Gemini API between 10:45 and 11:15 am.

Treat those two differently from the first two. A status page is the operator saying what broke; a spike in user reports is a crowd saying something felt broken. Both are evidence, but only one of them is the vendor's own record.

Why this matters more than any single outage

The usual answer to a model provider going down is a second model provider. September 3 is the morning that answer did not help, because the second and third choices were degrading at the same time. Ars reports the baseline these incidents sit against: Claude at 99.4% uptime over the previous 90 days, ChatGPT at 99.63%, and ChatGPT Codex at 100%.

One possible explanation is contagion rather than coincidence: when one provider slows, traffic moves to the others, and the others meet a spike they did not plan for. Nothing on any status page confirms that, and no shared cause has been published. What is confirmed is the shape of the failure, and the shape is what you design against.

The practical conclusion is unglamorous. A fallback chain that only switches vendors buys less than it appears to. Queue the work, make retries idempotent, degrade the feature instead of the whole page, and tell the person waiting what is happening. That plan costs the same whether one provider is down or four are.