Ask HN: Claude Opus performance affected by time of day?

#1

Post by scaredreally » Fri, Jan 16, 2026, 5:15 PM UTC

I am a big fan of Claude Opus as it has been very good at understanding feature requests and generally staying consistent with my codebase (completely written from scratch using Opus).

I've noticed recently that when I am using Opus at night (Eastern US), I am seeing it go down extreme rabbit holes on the same types of requests I am putting through on a regular basis. It is more likely to undertake refactors that break the code and then iterates on those errors in a sort of spiral. A request that would normally take 3-4 minutes will turn into a 10 minute adventure before I revert the changes, call out the mistake, and try again. It will happily admit the mistake, but the pattern seems to be consistent.

I haven't performed a like for like test and that would be interesting, but has anyone else noticed the same?

Re: Ask HN: Claude Opus performance affected by time of day?

#2

Post by bayarearefugee » Fri, Jan 16, 2026, 9:21 PM UTC

I mostly use Gemini, so I can't speak for Claude, but Gemini definitely has variable quality at different times, though I've never bothered to try to find a specific time-of-day pattern to it.

The most reliable time to see it fall apart is when Google makes a public announcement that is likely to cause a sudden influx of people using it.

And there are multiple levels of failure, first you start seeing iffy responses of obvious lesser quality than usual and then if things get really bad you start seeing just random errors where Gemini will suddenly lose all of its context (even on a new chat) or just start failing at the UI level by not bothering to finish answers, etc.

The sort of obvious likely reason for this is when the models are under high load they probably engage in a type of dynamic load balancing where they fall back to lighter models or limit the amount of time/resources allowed for any particular prompt.

Re: Ask HN: Claude Opus performance affected by time of day?

#3

Post by janalsncm » Fri, Jan 16, 2026, 9:25 PM UTC

It’s possible that they could be using fallback models during peak load times (west coast mid day). I assume your traffic would be routed to an east coast data center though. But secretly routing traffic to a worse model is a bit shady so I’d want some concrete numbers to quantify worse performance.

Re: Ask HN: Claude Opus performance affected by time of day?

#4

Post by causal » Fri, Jan 16, 2026, 9:25 PM UTC

I've had the same suspicion for various providers - if I had time and motivation I would put together a private benchmark that runs hourly and chart performance over time. If anyone wants to do that I'll upvote your Show HN :)

Re: Ask HN: Claude Opus performance affected by time of day?

#5

Post by kevinsync » Fri, Jan 16, 2026, 9:27 PM UTC

bayarearefugee wrote: post #2

I mostly use Gemini, so I can't speak for Claude, but Gemini definitely has variable quality at different times, though I've never bothered to try to find a specific time-of-day pattern to it. The most reliable time to see it fall apart is when Google makes a public announcement that is likely to cause a sudden influx of people using it. And there are multiple levels of failure, first you start seeing iffy responses…

I suspect they might transparently fall back too; Opus 4.5 has been really reasonable lately, except right after it launched, and also surrounding any service interruptions / problems reported on status.claude.ai -- once those issues resolve, for a few hours the results feel very "Sonnet", and it starts making a lot more mistakes. When that happens, I'll usually just pause Claude and prompt Codex and Gemini with the same issue to see what comes out of the black hole.. then a bit later, Claude mysteriously regains its wits.

I just assume it went to the bar, got wasted, and needed time to sober up!

Re: Ask HN: Claude Opus performance affected by time of day?

#6

Post by oncallthrow » Fri, Jan 16, 2026, 9:28 PM UTC

For what it’s worth, Anthropic very strongly claim that they don’t degrade model performance by time of day [1]. I have no reason to doubt that, imo Anthropic are about as ethical as LLM companies get.

[1] https://www.anthropic.com/engineering/a-postmortem-of-three-...

Re: Ask HN: Claude Opus performance affected by time of day?

#7

Post by hagbard_c » Fri, Jan 16, 2026, 9:36 PM UTC

Simple, the model is tired after a long day of working so it starts making mistakes. Give it some rest and it is ready to serve again.

Re: Ask HN: Claude Opus performance affected by time of day?

#8

Post by anonzzzies » Fri, Jan 16, 2026, 9:39 PM UTC

Many people 'notice' it (on reddit); I notice it too, but it is hard to prove. I tried the same prompt on the same code every 4 hours for 48 hours, the behaviour was slightly different but not worse or much different in time. But then I just work on my normal code, think wtf is it doing now??? look at the time and see it is US day time and stop.

People put forward many theories for this (weaker model routing; be it a different model, Sonnet or Haiku or lower quantized Opus seem the most popular), Anthropic says it is all not happening.

Re: Ask HN: Claude Opus performance affected by time of day?

#9

Post by scaredreally » Fri, Jan 16, 2026, 9:42 PM UTC

kevinsync wrote: post #5

bayarearefugee wrote: post #2

I mostly use Gemini, so I can't speak for Claude, but Gemini definitely has variable quality at different times, though I've never bothered to try to find a specific time-of-day pattern to it. The most reliable time to see it fall apart is when Google makes a public announcement that is likely to cause a sudden influx of people using it. And there are multiple levels of failure, first you start seeing iffy responses…

I suspect they might transparently fall back too; Opus 4.5 has been really reasonable lately, except right after it launched, and also surrounding any service interruptions / problems reported on status.claude.ai -- once those issues resolve, for a few hours the results feel very "Sonnet", and it starts making a lot more mistakes. When that happens, I'll usually just pause Claude and prompt Codex and Gemini with the…

Precisely. Once I point out the fact that it is doing this, it seems to produce better results for a bit before going back to the same.

I jokingly (and not so) thought that it was trained on data that made it think it should be tired at the end of the day.

But it is happening daily and at night.

Re: Ask HN: Claude Opus performance affected by time of day?

#10

Post by RickS » Fri, Jan 16, 2026, 9:43 PM UTC

I've certainly noticed some variance from opus. there are times it gets stuck and loops on dumb stuff that would have been frustrating from sonnet 3.5, let alone something as good as opus 4.5 when it's locked in. But it's not obviously correlated with time, I've hit those snags at odd hours, and gotten great perf during peak times. It might just be somewhat variable, or a shitty context.

Now GPT4.1 was another story last year, I remember cooking at 4am pacific and feeling the whole thing slam to a halt as the US east coast came online.