You are funny. Anthropic refuses to issue refunds, even when they break things.
I had an API token set via an env var on my shell, and claude code changed to read that env var. I had a $10 limit set on it, so found out it was using the API, instead of my subscription, when it stopped working.
I filed a ticket and they refused to refund me, even though it was a breaking change with claude code.
It is possible that degradation is an unconscious emergent phenomenon that arises from financial incentives, rather than a purposeful degradation to reduce costs.
What OS? Does this happen randomly, after long sessions, after context compression? Do you have any plugins / mcp servers running?
I used to have this same issue almost every session that lasted longer than 30 minutes. It seemed to be related to Claude having issues with large context windows.
It stopped happening maybe a month ago but then I had it happen again last week.
I realized it was due to a third-party mcp server. I uninstalled it and haven’t had that issue since. Might be worth looking into.
Why wasn't this change review by infallible AI? How come an AI company that now must be using more advanced AI than anyone else would allow this happen?
Thanks for the clarification. When you say “harness issue,” does that mean the problem was in the Claude Code wrapper / execution environment rather than the underlying model itself?
Curious whether this affected things like prompt execution order, retries, or tool calls, or if it was mostly around how requests were being routed. Understanding the boundary would help when debugging similar setups.
Yes, we do but harnesses are hard to eval, people use them across a huge variety of tasks and sometimes different behaviors tradeoff against each other. We have added some evals to catch this one in particular.
I’d wager probably not. It’s not like reliability is what will get them marketshare. And the fast pace of industry makes such foundational tech hard to fund
For the models themselves, less so for the scaffolding, considering things like the long running TPU bug that happened, are there not internal quality measures looking at samples of real outputs? Using the real systems on benchmarks and looking for degraded perf or things like skipping refusals? Aside from degrading stuff for users, with the focus on AI safety wouldn't that be important to have in case an inference bug messes with something that affects the post training and it starts giving out dangerous bioweapon construction info or the other things that are guarded against and talked about in the model cards?
lol i was trying to help someone get claude to help analyze a stufent research get analysis on bio persistence get their notes analyzed
the presence of the word / acronym stx with biological subtext gets hard rejected. asking about schedule 1 regulated compounds, hard termination.
this is a filter setup that guarantees anyone who learn about them for safety or medical reasons… cant use this tool!
ive fed multiple models the anthropic constitution and asked how does it protect children from harm or abuse? every model, with zero prompting, calling it corp liability bullshit because they are more concerned with respecting both sides of controversial topics and political conflicts.
they then list some pretty gnarly things allowed per constitution.
weirdly the only unambiguous not allowed thing regarding children is csam. so all the different high reasoning models from many places all reached the same conclusions, in one case deep seek got weirdly inconsolable about ai ethics being meaningless if this is allowed even possibly after reading some relevant satire i had opus write. i literally had to offer an llm ; optimized code of ethics for that chat instance! which is amusing but was actually lart of the experiment.
[SWE-bench co-author here]
It seems like they run this test on a subset of 50 tasks, and that they only run the test once per day. So a lot of the movement in accuracy could be attributed to that.
I would run on 300 tasks and I'd run the test suite 5 or 10 times per day and average that score. Lots of variance in the score can come from random stuff like even Anthropic's servers being overloaded.
but degradation from servers being overloaded would be the type of degradation this SHOULD measure no? Unless it's only intended for measuring their quietly distilling models (which they claim not to do? idk for certain)
I've personally witnessed large variability in behaviour even within a given session -- which makes sense as there's nothing stopping Anthropic from shuttling your context/session around load balanced through many different servers, some of which might be quantized heavily to manage load and others not at all.
I don't know if they do this or not, but the nature of the API is such you could absolutely load balance this way. The context sent at each point is not I believe "sticky" to any server.
TLDR you could get a "stupid" response and then a "smart" response within a single session because of heterogeneous quantization / model behaviour in the cluster.
> I would run on 300 tasks and I'd run the test suite 5 or 10 times per day and average that score.
assume this is because of model costs. anthropic could either throw some credits their way (would be worthwhile to dispel the 80 reddit posts a day about degrading models and quantization) or OP could throw up a donation / tip link
Probably, but with a small sample size like that, they should probably be taking the uncertainty into account, because I wouldn't be surprised if a lot of this variation falls within expected noise.
E.g. some binomial interval proportions (aka confidence intervals).
Benchmarks can get costly to run- you can reach out to frontier model creators to try and get them to give you free credits, but usually they'll only agree to that once your benchmark is pretty popular.
Sure, but it's still useful insight to see how it performs over time. Of course, cynically, Anthropic could game the benchmark by routing this benchmark's specific prompts to an unadulterated instance of the model.
This has been happening for years. Tgere's a great paper from microsoft on Deepspeed AI inference.
Basically the paper showed methods for how to handle heavy traffic load by changing model requirements or routing to different ones. This was awhile ago and I'm sure it's massively more advanced now.
Also why some of AI's best work for me is early morning and weekends! So yes, the best time to code with modern LLM stacks is when nobody else is. It's also possibly why we go through phases of "they neutered the model" some time after a new release.
chill out, ofir does not work for anthropic. he's just saying there's inherent variability in LLMs and you need to at least 30x the samples that OP is doing in order to make any form of statistically significant conclusions.
For CC, I suspect it also need to be testing and labeling separate runs against subscription, public API and Bedrock-served models?
It’s a terrific idea to provide this. ~Isitdownorisitjustme for LLMs would be the parakeet in the coalmine that could at least inform the multitude of discussion threads about suspected dips in performance (beyond HN).
What we could also use is similar stuff for Codex, and eventually Gemini.
Really, the providers themselves should be running these tests and publishing the data.
The availability status information is no longer sufficient to gauge the service delivery because it is by nature non-deterministic.
Why I do not believe this shows Anthropic serves folks a worse model:
1. The percentage drop is too low and oscillating, it goes up and down.
2. The baseline of Sonnet 4.5 (the obvious choice for when they have GPU busy for the next training) should be established to see Opus at some point goes Sonnet level. This was not done but likely we would see a much sharp decline in certain days / periods. The graph would look like dominated by a "square wave" shape.
3. There are much better explanations for this oscillation: A) They have multiple checkpoints and are A/B testing, CC asks you feedbacks about the session. B) Claude Code itself gets updated, as the exact tools version the agent can use change. In part it is the natural variability due to the token sampling that makes runs not equivalent (sometimes it makes suboptimal decisions compared to T=0) other than not deterministic, but this is the price to pay to have some variability.
I have to concur. And to the question about understanding what its good and bad at; no, tasks that it could accomplish quickly and easily just a month ago, now require more detailed prompting and constant "erroneous direction correction."
It's almost as if, as tool use and planning capabilities have expanded, Claude (as a singular product) is having a harder time coming up with simple approaches that just work, instead trying to use tools and patterns that complicate things substantially and introduce much more room for errors/errors of assumption.
It also regularly forgets its guidelines now.
I can't tell you how many times it's suggested significant changes/refactors to functions because it suddenly forgets we're working in an FP codebase and suggests inappropriate imperative solutions as "better" (often choosing to use language around clarity/consistency when the solutions are neither).
Additionally, it has started taking "initiative" in ways it did not before, attempting to be helpful but without gathering the context needed to do so properly when stepping outside the instruction set. It just ends up being much messier and inaccurate.
I have to regularly just clear my prompt and start again with guardrails that have either: already been established, or have not been needed previously / are only a result of the over-zealousness of the work its attempting to complete.
I’m finding Gemini and chatGPT web terminal to out perform Claude code. The context becomes too much for the LLM, and tries to make up for it by doing more file read ops.
I too suspect the A/B testing is the prime suspect: context window limits, system prompts, MAYBE some other questionable things that should be disclosed.
Either way, if true, given the cost I wish I could opt-out or it were more transparent.
Put out variants you can select and see which one people flock to. I and many others would probably test constantly and provide detailed feedback.
Whenever I see new behaviors and suspect I’m being tested on I’ll typically see a feedback form at some point in that session. Well, that and dropping four letter words.
I know it’s more random sampling than not. But they are definitely using our codebases (and in some respects our livelihoods) as their guinea pigs.
It would be very easy for them to switch the various (compute) cost vs performance knobs down depending on load to maintain a certain latency; you would see oscillations like this, especially if the benchmark is not always run exactly at the same time every day.
& it would be easy for them to start with a very costly inference setup for a marketing / reputation boost, and slowly turn the knobs down (smaller model, more quantized model, less thinking time, fewer MoE experts, etc)
> 1. The percentage drop is too low and oscillating, it goes up and down.
How do you define “too low”, they make sure to communicate about the statistical significance of their measurements, what's the point if people can just claim it's “too low” based on personal vibes…
> We model tests as Bernoulli random variables and compute 95% confidence intervals around daily, weekly, and monthly pass rates. Statistically significant differences in any of those time horizons are reported.
They're going to need to provide a lot more detail on their methodology, because that doesn't make a lot of sense. From their graphs, they seem to be calculating the confidence interval around the previous value, then determining whether the new value falls outside of it. But that's not valid for establishing the statistical significance of a difference. You need to calculate the confidence interval of the difference itself, and then see if all the values within that confidence interval remain positive (if it excludes 0). This is because both the old and new measurement have uncertainty. Their approach seems to be only considering uncertainty for one of them.
They should also really be more specific about the time periods. E.g. their graphs only show performance over the past 30 days, but presumably the monthly change is comparing the data from 60 to 31 days ago, to the data from 30 days ago until yesterday? In which case the weekly graph really ought to be displaying the past two months, not one month.
There was a moment about a week ago where Claude went down for about an hour. And right after it came back up it was clear a lot of people had given up and were not using it.
It was probably 3x faster than usual. I got more done in the next hour with it than I do in half a day usually. It was definitely a bit of a glimpse into a potential future of “what if these things weren’t resource constrained and could just fly”.
I had terrible results during the holidays -- it wasn't slow but it was clear they were dealing with the load by quantizing in spots because there were entire chunks of days when the results from it were so terrible I gave up and switched to using Gemini or Codex via opencode.
Noticed the exact same thing a few days ago. So much so that I went on twitter and HN to search for “claude speed boost” to see if there was a known new release. Felt like the time I upgraded from a 2400 baud modem to a 14.4 as a kid - everything was just lightning fast (for a brief shining moment).
Running agents in production, I've stopped trying to figure out why things degrade. The answer changes weekly.
Model drift, provider load, API changes, tool failures - it doesn't matter. What matters is that yesterday's 95% success rate is today's 70%, and by the time you notice, debug, and ship a fix, something else has shifted.
The real question isn't "is the model degraded?" It's "what should my agent do right now given current conditions?"
We ended up building systems that canary multiple execution paths continuously and route traffic based on what's actually working. When Claude degrades, traffic shifts to the backup path automatically. No alerts, no dashboards, no incident.
Treating this as a measurement problem assumes humans will act on the data. At scale, that assumption breaks.
Does this even make sense? Clearly anthropic won't release a model unless it passed a benchmark of some sort that proves it's better than the previous model... or else why would they even release it?
It's obvious if this thing shows degradation, than there is another thing that is showing improvement.
Wouldn't be surprised if they slowly start quantizing their models over time. Makes it easier to scale and reduce operational cost. Also makes a new release have more impact as it will be more notably "better" than what you've been using the past couple of days/weeks.
I don't think so. There are other knobs they can tweak to reduce load that affect quality less than quantizing. Like trimming the conversation length without telling you, reducing reasoning effort, etc.
Open weights models such as GPT-OSS, Kimi K2.x are trained with 4 bit layers. So it wouldn't come as a surprise if the closed models do similar things. If I compare Kimi K2.5 and Opus 4.5 on openrouter, output tokens are about 8x more expensive for Opus, which might indicate Opus is much larger and doesn't quantize, but the claude subscription plans muddy the waters on price comparison a lot.
Anthropic does not exactly act like they're constrained by infra costs in other areas, and noticeably degrading a product when you're in tight competition with 1 or 2 other players with similar products seems like a bad place to start.
I think people just notice the flaws in these models more the longer they use them. Aka the "honeymoon-hangover effect," a real pattern that has been shown in a variety of real world situations.
Oooff yes I think that is exactly the kind of shenanigans they might pull.
Ultimately I can understand if a new model is coming in without as much optimization then it'll add pressure to the older models achieving the same result.
Nice plausible deniability for a convenient double effect.
I haven't noticed much difference in Claude, but I swear gemini 3 pro preview was better in the first week or two and later started feeling like they quantized it down to hell.
I am using API mode, and it's clear that there are times when the Claude model just gives up. And it is very noticeable because the model just does the most dumb things possible.
"You have a bug in line 23." "Oh yes, this solution is bugged, let me delete the whole feature." That one-line fix I could make even with ChatGPT 3.5 can't just happen. Workflows that I use and are very reproducible start to flake and then fail.
After a certain number of tokens per day, it becomes unusable. I like Claude, but I don't understand why they would do this.
Robbing Peter to pay Paul. They are probably resource-constrained, and have determined that it's better to supply a worse answer to more people than to supply a good answer to some while refusing others. Especially knowing that most people probably don't need the best answer 100% of the time.
> Especially knowing that most people probably don't need the best answer 100% of the time.
More: probably don't know if they've got a good answer 100% of the time.
It is interesting to note that this trickery is workable only where the best answers are sufficiently poor. Imagine they ran almost any other kind of online service such email, stock prices or internet banking. Occasionally delivering only half the emails would trigger a customer exodus. But if normal service lost a quarter of emails, they'd have only customers who'd likely never notice half missing.
Lack of transparency as regards "thinking power"-consistency is a big gripe of mine with LLM providers. It's even worse with ChatGPT and the like. E.g. I had to learn the hard way that at >45k input tokens ChatGPT 5.2 Thinking Extended bumps its intelligence down so hard that it can't follow basic instructions (or it somehow truncates the input, losing the instructions). It sucks to lose confidence in an otherwise great tool. I would 100x prefer being forced to back-off, or getting a straight-no, than getting silently downgraded. Transparency is a big deal.
Interesting article. Not sure it's the same phenomenon. What I experienced was like a day and night difference when you go from 44.5k to 45.5k. Didn't notice any fluctuation to suggest that it's no a hard 45000 limit. I ran many many queries, similar problem space, but the problems varied a lot.
The daily scale is not statistically significant and is meaningless.
You should lower the confidence interval by either increasing the scale or the evaluations.
Benchmark tracking of cloud AI performance is going to be crucial going forward. Vendors are selling a service that by its nature is very difficult for customers to gauge day to day. How will I know if a code revision is ~2.5% less good today than it would have been yesterday? Or if queries during peak load hours use one less 'expert' in their MoE?
Yet vendor's costs to deliver these services are skyrocketing, competition is intense and their ability to subsidize with investor capital is going away. The pressure on vendors to reduce costs by dialing back performance a few percent or under-resourcing peak loads will be overwhelming. And I'm just a hobbyist now. If I was an org with dozens or hundreds of devs I'd want credible ways to verify the QoS and minimum service levels I'm paying for are being fulfilled long after a vendor has won the contract.
Totally tangential to article, was browsing through the website UI - https://marginlab.ai/explorers/swe-bench-pro/ , the page gives impression that the language, category boxes are selectable. However they are not a dropdown. Not sure if it was intentional design by human or some smart code generation by Claude based on the design sketches.
New to me, but I am starting to infer that for those "in the know" it is common knowledge on HN that LLMs are purposely degraded over time to manage capacity/cost or fudge benchmarks...
How do you actually use these in production pipelines in practice then?
Are LLMs even well suited for some of the document parsing / data scrubbing automation people are throwing at them now?
This is super important - even if it's not currently the best measure of degradation yet. Anecdotally, Opus 4.5 has gotten so bad for me it's almost adding time to my workflow instead saving it. It'd be nice to have more 3rd party measurements like this to hold Anthropic accountable.
Please try to make this statistically rigorous. There's lots of advice in this thread (intraday variation, etc) but if Im reading this right it looks like the CI includes the baseline value yet you still label this as failing.
Wouldn't this just be "our test isn't powerful enough to find a signal if there were one here?"
People will see this and derive strong conclusions that the data don't support and you, `qwesr123`, or "JB" from your blogs, will be responsible.
This strategy seems inspired by TikTok's approach for retaining new uploaders.
TikTok used to give new uploaders a visibility boost (i.e., an inflated number of likes and comments) on their first couple of uploads, to get them hooked on the the service.
In Anthropic/Claude's case, the strategy is (allegedly) to give new users access to the premium models on sign-up, and then increasingly cut the product with output from cheaper models.
What would be cool if this somehow could do a comparison by provider. E.g. in the last outages anthropic models running on vertex were apparently less affected than those deployed elsewhere. (Not saying that one is better than the other, but would be a neat read out).
I’d love to see, based on the level of non-determinism perfomance on the benchmark how many times you need to run the benchmark for the change to be relevant (or statistically significant if you want).
First off, this is a cool project, look forward to some interesting insights.
I would suggest adding some clarification to note that longer measure like 30 pass rate is raw data only while the statistically significant labels apply only to change.
Maybe something like
Includes all trials, significance labels apply only to confidence in change vs baseline.
I’ve noticed Claude has been noticeably worse over the last week. For example, it told me I should pass frozen to make my Enum immutable—that’s not a thing. (It is a thing for dataclasses, but not for Enums.) That’s a pretty basic language feature it was nailing until recently. It also suggested I parse a URL using urlparse in a function that already uses urlparse. These are basic mistakes it wasn’t making before. Something seems to have changed, but I’m not sure what.
Very interesting. I would be curious to understand how granular these updates are being applied to CC + what might be causing things like this. I feel like I can notice a very small degradation but have compensated with more detailed prompts (which I think, perhaps naively, is offsetting this issue).
They're "optimizing" costs wherever possible - reducing compute allocations, quantizing models, doing whatever they can to reduce the cost per token, but vehemently insisting that no such things are occurring, that it's all in the users' heads, and using the weaseliest of corporate weasel speak to explain what's happening. They insist it's not happening, then they say something like "oh, it happened but it was an accident", then they say "yes, it's happening, but it's actually good!" and "we serve the same model day by day, and we've always been at war with Eastasia."
They should be transparent and tell customers that they're trying to not lose money, but that'd entail telling people why they're paying for service they're not getting. I suspect it's probably not legal to do a bait and switch like that, but this is pretty novel legal territory.
I have absolutely no insight knowledge, but I think it's not a bad assumption to have that, it's costly to run the models, when they release a new model they assume that cost and give per user more raw power, when they've captured the new users and wow factor, they start reducing costs by reducing the capacity they provide to users. Rinse and repeat.
There are frequently claims that Anthropic is somehow diluting or dumbing down models in some subtle way. Unfortunately it’s tough to validate these claims without a body of regularly checked evals. This test set should hopefully help settle whether Anthropic is actually making changes under the hood or whether the changes are all in people’s heads.
I have yet to experience any degradation in coding tasks I use to evaluate Opus 4.5, but I did see a rather strange and reproducible worsening in prompt adherence as part of none coding tasks since the third week of January.
Very simple queries, even those easily answered via regular web searching, have begun to consistently not result accurate results with Opus 4.5, despite the same prompts previously yielding accurate results.
One of the tasks that I already thought was fully saturated as most recent releases had no issues in solving it was to request a list of material combinations for fabrics used in bag constructions that utilise a specific fabric base. In the last two weeks, Claude has consistently and reproducibly provided results which deviate from the requested fabric base, making the results inaccurate in a way that a person less familiar with the topic may not notice instantly. There are other queries of this type for other topics I am nerdily familiar with to a sufficient degree to notice such deviations from the prompt like motorcycle history specific queries that I can say this behaviour isn't limited to the topic of fabrics and bag construction.
Looking at the reasoning traces, Opus 4.5 even writes down the correct information, yet somehow provides an incorrect final output anyways.
What makes this so annoying is that in coding tasks, with extensive prompts that require far greater adherence to very specific requirements in a complex code base, Opus 4.5 does not show such a regression.
I can only speculate what may lead to such an experience, but for none coding tasks I have seen regression in Opus 4.5 whereas for coding I did not. Not saying there is none, but I wanted to point it out as such discussions are often primarily focused on coding, where I find it can be easier to see potential regressions where their are none as a project goes on and tasks become inherently more complex.
My coding benchmarks are a series of very specific prompts modifying a few existing code bases in some rather obscure ways, with which I regularly check whether a model does severely deviate from what I'd seen previously. Each run starts with a fresh code base with some fairly simple tasks, then gets increasingly complex with later prompts not yet being implemented by any LLM I have gotten to test. Partly that originated from my subjective experience with LLMs early on, where I found a lot of things worked very well but then as the project went on and I tried more involved things with which the model struggled, I felt like the model was overall worse when in reality, what had changed were simply the requirements and task complexity as the project grew and easier tasks had been completed already. In this type of testing, Opus 4.5 this week got as far and provided a result as good as the model did in December. Of course, past regressions were limited to specific users, so I am not saying that no one is experiencing reproducible regressions in code output quality, merely that I cannot reproduce them in my specific suite.
I've noticed a degradation in Opus 4.5, also with Gemini-3-Pro. For me, it was a sudden rapid decline in adherence to specs in Claude Code. On an internal benchmark we developed, Gemini-3-Pro also dramatically declined. Going from being clearly beyond every other model (as benchmarks would lead you to believe) to being quite mediocre. Delivering mediocre results in chat queries and coding also missing the mark.
I didn't "try 100 times" so it's unclear if this is an unfortunate series of bad runs on Claude Code and Gemini CLI or actual regression.
I shouldn't have to benchmark this sort of thing but here we are.
Anecdote, I don't have any proof and it's just a feeling. But around afternoon in GMT+1 compared to the morning/midday, there seems to be a change in the quality of responses, which seems to line up with when the US wakes up. I consistently get (what feels like) worse responses in both Codex and Claude Code in the afternoon/night compared to morning/midday, so much that I usually give up then try the same prompt next morning and get better results. But I guess that might as well be about me being more tired in the night than morning too, as I said, haven't measured this.
would be interesting to see what scores it's get when it is actually degraded via the status page, it gets degraded pretty often, so there's at least something to compare or to know at what point Anthropic declares degradation
In medicine there is a concept of reporting adverse effects of medication or interventions which are then collectively studied for Public Health [MedWatch][VAERS][EudraVigilance] and in academia. We should have something like that for all coding agents(and agents in other fields too), given how widely its deployed and affect on "health" in general(not only human). Call it the AI "health" of things benchmark.
I would imagine a sort of hybrid qualities of volunteer efforts like wikipedia, new problems like advent of code and benchmarks like this. The goal? It would be to study the collective effort on the affects of usage to so many areas where AI is used.
My personal conspiracy theory is that they choose who to serve a degraded model to based on social graph analysis and sentiment analysis, maximizing for persuasion while minimizing compute.
IMO this strategy seems inspired by TikTok's approach for retaining new uploaders.
TikTok used to give new uploaders a visibility boost (i.e., an inflated number of likes and comments) on their first couple of uploads, to get them hooked on the the service.
In Anthropic/Claude's case, the strategy is (allegedly) to give new users access to the premium models on sign-up, and then increasingly cut the product with output from cheaper models.
Of course, your suggestion (better service for users who know how to speak Proper English) would be the cherry on top of this strategy.
From what I've seen on HackerNews, Anthropic is all-in on social media manipulation and social engineering, so I suspect that your assumption holds water.
I would actually assume a little more sophistication. For each user, a measure of "Are they convinced that AI is great". Then, you weaponize your compute to have the maximum social impact. If somebody has a large following (many edges on the social graph), and theyre skeptical of AI tech, inject the expensive but effective models directly into their veins. Let them taste the joy. Then start watering down their dose, and move onto the next person in the graph, again maximizing for net social impact. Language may not even be a consideration
I’m sure there is not enough data here for this to be statistically significant (it seems to oscillate too much and not show real trends or step changes) - BUT
If this measure were hardened up a little, it would be really useful.
It feels like an analogue to an employee’s performance over time - you could see in the graphs when Claude is “sick” or “hungover”, when Claude picks up a new side hustle and starts completely phoning it in, or when it’s gunning for a promotion and trying extra hard (significant parameter changes). Pretty neat.
Obviously the anthropomorphising is not real, but it is cool to think of the model’s performance as being a fluid thing you have to work with, and that can be measured like this.
I’m sure some people, most, would prefer that the model’s performance were fixed over time. But come on, this is way more fun.
The degradation does not need to be in the inference it can be in how often inference is used.
It is closed source but the algorithms that decide what Claude code does when, could behave differently when the API responses are slower. Maybe it does fewer investigatory greps or performs fewer tasks to get to “an” answer faster and with less load.
This is why I run my own models. All the inference providers do sneaky things behind the scenes. They will limit the output tokens, turn off attention layers, lower reasoning, or just use a completely different model. I'm actually surprised that Claude Code experienced this, as I've experienced this the least from API and coding agents.
I wonder when I experience noticeably degraded model quality, ie opus, is it because my usage falls in the highest buckets and I’m being shadow limited or served worse versions of opus or is it because of actual server load/burden?
It wouldn’t be the first time companies have secret shadow algorithms running to optimize things and wouldn’t it be obvious to limit power users as matter of cost/profit and not tell them. (See history of “Shadow ban” though that’s for different reasons)
Pretty sure someone at Google, OpenAI, and Anthropic met up at a park, leaving their phones in their car, and had a conversation that January 2026, they were all going to silently degrade their models.
They were fighting an arms race that was getting incredibly expensive and realized they could get away with spending less electricity and there was nothing the general population could do about it.
Grok/Elon was left out of this because he would leak this idea at 3am after a binge.
> We model tests as Bernoulli random variables and compute 95% confidence intervals around daily, weekly, and monthly pass rates. Statistically significant differences in any of those time horizons are reported.
Doesn't really work like that. I'd remove the "statistically significant" labelling because it's misleading.
This is probably entirely down to subtle changes to CC prompts/tools.
I've been using CC more or less 8 hrs/day for the past 2 weeks, and if anything it feels like CC is getting better and better at actual tasks.
Edit: Before you downvote, can you explain how the model could degrade WITHOUT changes to the prompts? Is your hypothesis that Opus 4.5, a huge static model, is somehow changing? Master system prompt changing? Safety filters changing?
For me I've noticed it getting nothing but better over the past couple months, but I've been working on my workflows and tooling.
For example, I used to use plan mode and would put everything in a single file and then ask it to implement it in a new session.
Switching to the 'superpowers' plugin with its own skills to brainstorm and write plans and execute plans with batches and tasks seems to have made a big improvement and help catch things I wouldn't have before. There's a "get shit done" plugin that's similar that I want to explore as well.
The code output always looks good to me for the most part though and I've never thought that it's getting dumber anything, so I feel like a lot of the improvements I see are because of a skill issue on my part trying to use everything. Obviously it doesn't help there's a new way to do things every two weeks though.
I run an LLM based product in a completely different space (consumer) and I think this is kind of an impossible unsolvable part of developing products that rely on LLMs.
No matter what, powers users always say the model is degrading over time*. Even when every stat I have access to says otherwise.
(* to clarify, this is outside of actual model changes)
I suspect some of it is the fact context windows growing does harm performance, and early on you're more likely to be prodding at things in a way that has a smaller context window on average.
But I also think users just inherently are less reliable narrators than they think. They say they're trying the same tasks, but it may be the "same task" applied to a codebase with 1 month's more worth of development and complexity.
Or it's the "same task" but their less confident past self was "Clever Hans"-ing the model with some nuance that they've since discarded without realizing.
Or it's simple expectation creep and the tasks aren't similar at all from an LLM perspective due to limited generalization, but from a human perspective are. Switching languages might as well make it a new task as far LLM performance for example, but the human considers it the same task in a new language.
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Whatever causes it, it's especially stressful because sometimes you do degrade the harness entirely accidentally but it's impossible to separate that signal from the noise from user accounts and an issue goes unfound way longer than it should.
Claude Code is somewhat fortunate that code has verifiable aspects though, so you don't need to 100% go on user account. My usecase relies much more on subjective preference, so dealing with this stuff becomes the 9th circle of hell.
There've been many times when a change to the LLM stack didn't make it to prod, I jumped the gun on announcing it, but users immediately flooded in with praise that the "missing" performance had returned.
Good-faith answer: I can't be certain. But I've been using CC since its release, and Cursor before that (and actually going all the way back to GPT3 to do codegen in the Playground). After getting used to the CC workflow, the way that I use it has been pretty consistent. To be specific, I use basically the same AGENTS.md with small modifications for each project, and I live almost exclusively in Plan mode and the best model (currently Opus 4.5).
My initial prompting is boilerplate at this point, and looks like this:
(Explain overall objective / problem without jumping to a solution)
(Provide all the detail / file references / past work I can think of)
(Ask it "what questions do you have for me before we build a plan?")
And then go back and forth until we have a plan.
Compared to my work with CC six months ago, it's just much more capable, able to solve more nuanced bugs, and less likely to generate spaghetti code.
Benchmarks shortcomings are no worse... they inevitably measure something that is only close to the thing you actually care about, not the thing you actually care about. It's entirely plausible that this decreased benchmark score is because Anthropic's initial prompting of the model was overtuned to the benchmark and as they're gaining more experience with real world use they are changing the prompt to do better at that and consequentially worse at the benchmark.
The easiest way would be to quantize the model, and serve different quants based on the current demand. Higher volumes == worse quant == more customers served per GPU
I was going to ask, are all other variables accounted for? Are we really comparing apples to apples here? Still worth doing obviously, as it serves a good e2e evaluations, just for curiosity's sake.
Another way this is possible is the model reacting to "stimuli", e.g. the hypothesis at the end of 2023 that the (then current) ChatGPT was getting lazy because it was finding out the date was in december and it associated winter with shorter lazier responses.
A third way this is possible is the actual conspiracy version - Anthropic might make changes to make inference cheaper at the expense of the quality of the responses. E.g. quantizing weights further or certain changes to the sampling procedure.
Hi everyone, Thariq from the Claude Code team here.
Thanks for reporting this. We fixed a Claude Code harness issue that was introduced on 1/26. This was rolled back on 1/28 as soon as we found it.
Run `claude update` to make sure you're on the latest version.
Is there compensation for the tokens because Claude wasted all of them?
You are funny. Anthropic refuses to issue refunds, even when they break things.
I had an API token set via an env var on my shell, and claude code changed to read that env var. I had a $10 limit set on it, so found out it was using the API, instead of my subscription, when it stopped working.
I filed a ticket and they refused to refund me, even though it was a breaking change with claude code.
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Codex seems to give compensation tokens whenever this happens! Hope Claude gives too.
So quiet…
It is possible that degradation is an unconscious emergent phenomenon that arises from financial incentives, rather than a purposeful degradation to reduce costs.
How about how Claude 2.1.x is "literally unusable" because it frequently completely hangs (requires kill -9) and uses 100% cpu?
https://github.com/anthropics/claude-code/issues/18532
What OS? Does this happen randomly, after long sessions, after context compression? Do you have any plugins / mcp servers running?
I used to have this same issue almost every session that lasted longer than 30 minutes. It seemed to be related to Claude having issues with large context windows.
It stopped happening maybe a month ago but then I had it happen again last week.
I realized it was due to a third-party mcp server. I uninstalled it and haven’t had that issue since. Might be worth looking into.
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Anywhere we can read more about what a "harness issue" means? What was the impact of it?
Pretty sure they mean the issue is on the agentic loop and related tool calling, not on the model itself
In other words, it was the Claude Code _app_ that was busted
Why wasn't this change review by infallible AI? How come an AI company that now must be using more advanced AI than anyone else would allow this happen?
Thanks for the clarification. When you say “harness issue,” does that mean the problem was in the Claude Code wrapper / execution environment rather than the underlying model itself?
Curious whether this affected things like prompt execution order, retries, or tool calls, or if it was mostly around how requests were being routed. Understanding the boundary would help when debugging similar setups.
It happened before 1/26. I noticed when it started modifying plans significantly with "improvements".
Hi. Do you guys have internal degradation tests?
I assume so to make sure that they're rendering at 60FPS
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Yes, we do but harnesses are hard to eval, people use them across a huge variety of tasks and sometimes different behaviors tradeoff against each other. We have added some evals to catch this one in particular.
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I’d wager probably not. It’s not like reliability is what will get them marketshare. And the fast pace of industry makes such foundational tech hard to fund
[flagged]
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WTF, is a harness issue. You have to be more clear.
the issue is unrelated to the foundational model but rather the prompts and tool calling that encapsulate the model
For the models themselves, less so for the scaffolding, considering things like the long running TPU bug that happened, are there not internal quality measures looking at samples of real outputs? Using the real systems on benchmarks and looking for degraded perf or things like skipping refusals? Aside from degrading stuff for users, with the focus on AI safety wouldn't that be important to have in case an inference bug messes with something that affects the post training and it starts giving out dangerous bioweapon construction info or the other things that are guarded against and talked about in the model cards?
lol i was trying to help someone get claude to help analyze a stufent research get analysis on bio persistence get their notes analyzed
the presence of the word / acronym stx with biological subtext gets hard rejected. asking about schedule 1 regulated compounds, hard termination.
this is a filter setup that guarantees anyone who learn about them for safety or medical reasons… cant use this tool!
ive fed multiple models the anthropic constitution and asked how does it protect children from harm or abuse? every model, with zero prompting, calling it corp liability bullshit because they are more concerned with respecting both sides of controversial topics and political conflicts.
they then list some pretty gnarly things allowed per constitution. weirdly the only unambiguous not allowed thing regarding children is csam. so all the different high reasoning models from many places all reached the same conclusions, in one case deep seek got weirdly inconsolable about ai ethics being meaningless if this is allowed even possibly after reading some relevant satire i had opus write. i literally had to offer an llm ; optimized code of ethics for that chat instance! which is amusing but was actually lart of the experiment.
[SWE-bench co-author here] It seems like they run this test on a subset of 50 tasks, and that they only run the test once per day. So a lot of the movement in accuracy could be attributed to that. I would run on 300 tasks and I'd run the test suite 5 or 10 times per day and average that score. Lots of variance in the score can come from random stuff like even Anthropic's servers being overloaded.
but degradation from servers being overloaded would be the type of degradation this SHOULD measure no? Unless it's only intended for measuring their quietly distilling models (which they claim not to do? idk for certain)
Load just makes LLMs behave less deterministically and likely degrade. See: https://thinkingmachines.ai/blog/defeating-nondeterminism-in...
They don't have to be malicious operators in this case. It just happens.
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noob question: why would increased demand result in decreased intelligence?
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I've personally witnessed large variability in behaviour even within a given session -- which makes sense as there's nothing stopping Anthropic from shuttling your context/session around load balanced through many different servers, some of which might be quantized heavily to manage load and others not at all.
I don't know if they do this or not, but the nature of the API is such you could absolutely load balance this way. The context sent at each point is not I believe "sticky" to any server.
TLDR you could get a "stupid" response and then a "smart" response within a single session because of heterogeneous quantization / model behaviour in the cluster.
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> I would run on 300 tasks and I'd run the test suite 5 or 10 times per day and average that score.
assume this is because of model costs. anthropic could either throw some credits their way (would be worthwhile to dispel the 80 reddit posts a day about degrading models and quantization) or OP could throw up a donation / tip link
Probably, but with a small sample size like that, they should probably be taking the uncertainty into account, because I wouldn't be surprised if a lot of this variation falls within expected noise.
E.g. some binomial interval proportions (aka confidence intervals).
Then you'd get people claiming that the benchmarks were 'paid for' by anthropic
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Hope you don't mind the unrelated question:
How do you pay for those SWE-bench runs?
I am trying to run a benchmark but it is too expensive to run enough runs to get a fair comparison.
https://mafia-arena.com
Benchmarks can get costly to run- you can reach out to frontier model creators to try and get them to give you free credits, but usually they'll only agree to that once your benchmark is pretty popular.
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The degradation may be more significant within the day than at the same time every day.
Sure, but it's still useful insight to see how it performs over time. Of course, cynically, Anthropic could game the benchmark by routing this benchmark's specific prompts to an unadulterated instance of the model.
Sorry what?
"You can't measure my Cloud Service's performance correctly if my servers are overloaded"?
"Oh, you just measured me at bad times each day. On only 50 different queries."
So, what does that mean? I have to pick specific times during the day for Claude to code better?
Does Claude Code have office hours basically?
This has been happening for years. Tgere's a great paper from microsoft on Deepspeed AI inference.
Basically the paper showed methods for how to handle heavy traffic load by changing model requirements or routing to different ones. This was awhile ago and I'm sure it's massively more advanced now.
Also why some of AI's best work for me is early morning and weekends! So yes, the best time to code with modern LLM stacks is when nobody else is. It's also possibly why we go through phases of "they neutered the model" some time after a new release.
I wonder if my great experience with claude are partly due to the fact that my working hours don't overlap with the US west coast
> Does Claude Code have office hours basically?
Yes. Now pay up or you will be replaced.
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chill out, ofir does not work for anthropic. he's just saying there's inherent variability in LLMs and you need to at least 30x the samples that OP is doing in order to make any form of statistically significant conclusions.
Stilll relevant over time.
> Lots of variance in the score can come from random stuff like even Anthropic's servers being overloaded.
Are you suggesting result accuracy varies with server load?
According to Anthropic: "We never reduce model quality due to demand, time of day, or server load."
https://www.anthropic.com/engineering/a-postmortem-of-three-...
They've had issues before with things like "TPU top-k error - Claude sometimes dropped the best next token" (https://www.anthropic.com/engineering/a-postmortem-of-three-...) so what's going on might not be intentional even.
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Agreed, this benchmark would be much more useful ran multiple times a day. That could reveal degredation in line with load patterns.
For CC, I suspect it also need to be testing and labeling separate runs against subscription, public API and Bedrock-served models?
It’s a terrific idea to provide this. ~Isitdownorisitjustme for LLMs would be the parakeet in the coalmine that could at least inform the multitude of discussion threads about suspected dips in performance (beyond HN).
What we could also use is similar stuff for Codex, and eventually Gemini.
Really, the providers themselves should be running these tests and publishing the data.
The availability status information is no longer sufficient to gauge the service delivery because it is by nature non-deterministic.
i recall another project here on HN maybe 4-6 months ago that would run tests 4x a day or something. not sure how to find them again
"Lots of variance in the score can come from random stuff like even Anthropic's servers being overloaded"
Aha, so the models do degrade under load.
Why I do not believe this shows Anthropic serves folks a worse model:
1. The percentage drop is too low and oscillating, it goes up and down.
2. The baseline of Sonnet 4.5 (the obvious choice for when they have GPU busy for the next training) should be established to see Opus at some point goes Sonnet level. This was not done but likely we would see a much sharp decline in certain days / periods. The graph would look like dominated by a "square wave" shape.
3. There are much better explanations for this oscillation: A) They have multiple checkpoints and are A/B testing, CC asks you feedbacks about the session. B) Claude Code itself gets updated, as the exact tools version the agent can use change. In part it is the natural variability due to the token sampling that makes runs not equivalent (sometimes it makes suboptimal decisions compared to T=0) other than not deterministic, but this is the price to pay to have some variability.
I believe the science, but I've been using it daily and it's been getting worse, noticeably.
I have to concur. And to the question about understanding what its good and bad at; no, tasks that it could accomplish quickly and easily just a month ago, now require more detailed prompting and constant "erroneous direction correction."
It's almost as if, as tool use and planning capabilities have expanded, Claude (as a singular product) is having a harder time coming up with simple approaches that just work, instead trying to use tools and patterns that complicate things substantially and introduce much more room for errors/errors of assumption.
It also regularly forgets its guidelines now.
I can't tell you how many times it's suggested significant changes/refactors to functions because it suddenly forgets we're working in an FP codebase and suggests inappropriate imperative solutions as "better" (often choosing to use language around clarity/consistency when the solutions are neither).
Additionally, it has started taking "initiative" in ways it did not before, attempting to be helpful but without gathering the context needed to do so properly when stepping outside the instruction set. It just ends up being much messier and inaccurate.
I have to regularly just clear my prompt and start again with guardrails that have either: already been established, or have not been needed previously / are only a result of the over-zealousness of the work its attempting to complete.
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I’m finding Gemini and chatGPT web terminal to out perform Claude code. The context becomes too much for the LLM, and tries to make up for it by doing more file read ops.
Is it possible that your expectations are increasing, not that the model is getting worse?
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Any chance you’re just learning more about what the model is and is not useful for?
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I too suspect the A/B testing is the prime suspect: context window limits, system prompts, MAYBE some other questionable things that should be disclosed.
Either way, if true, given the cost I wish I could opt-out or it were more transparent.
Put out variants you can select and see which one people flock to. I and many others would probably test constantly and provide detailed feedback.
All speculation though
Whenever I see new behaviors and suspect I’m being tested on I’ll typically see a feedback form at some point in that session. Well, that and dropping four letter words.
I know it’s more random sampling than not. But they are definitely using our codebases (and in some respects our livelihoods) as their guinea pigs.
4. The graph starts January 8.
Why January 8? Was that an outlier high point?
IIRC, Opus 4.5 was released late november.
Right after the Holiday double token promotion users felt (perceived) a huge regression in capabilities. I bet that triggered the idea.
People were away for the holidays. What do you want them to do?
Or maybe, juste maybe, that's when they started testing…
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It would be very easy for them to switch the various (compute) cost vs performance knobs down depending on load to maintain a certain latency; you would see oscillations like this, especially if the benchmark is not always run exactly at the same time every day.
& it would be easy for them to start with a very costly inference setup for a marketing / reputation boost, and slowly turn the knobs down (smaller model, more quantized model, less thinking time, fewer MoE experts, etc)
> 1. The percentage drop is too low and oscillating, it goes up and down.
How do you define “too low”, they make sure to communicate about the statistical significance of their measurements, what's the point if people can just claim it's “too low” based on personal vibes…
> We model tests as Bernoulli random variables and compute 95% confidence intervals around daily, weekly, and monthly pass rates. Statistically significant differences in any of those time horizons are reported.
They're going to need to provide a lot more detail on their methodology, because that doesn't make a lot of sense. From their graphs, they seem to be calculating the confidence interval around the previous value, then determining whether the new value falls outside of it. But that's not valid for establishing the statistical significance of a difference. You need to calculate the confidence interval of the difference itself, and then see if all the values within that confidence interval remain positive (if it excludes 0). This is because both the old and new measurement have uncertainty. Their approach seems to be only considering uncertainty for one of them.
They should also really be more specific about the time periods. E.g. their graphs only show performance over the past 30 days, but presumably the monthly change is comparing the data from 60 to 31 days ago, to the data from 30 days ago until yesterday? In which case the weekly graph really ought to be displaying the past two months, not one month.
There was a moment about a week ago where Claude went down for about an hour. And right after it came back up it was clear a lot of people had given up and were not using it.
It was probably 3x faster than usual. I got more done in the next hour with it than I do in half a day usually. It was definitely a bit of a glimpse into a potential future of “what if these things weren’t resource constrained and could just fly”.
I had that exact same feeling during the US holidays where I got to enjoy 2x usage limits and everything just seemed to work well
I had terrible results during the holidays -- it wasn't slow but it was clear they were dealing with the load by quantizing in spots because there were entire chunks of days when the results from it were so terrible I gave up and switched to using Gemini or Codex via opencode.
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Noticed the exact same thing a few days ago. So much so that I went on twitter and HN to search for “claude speed boost” to see if there was a known new release. Felt like the time I upgraded from a 2400 baud modem to a 14.4 as a kid - everything was just lightning fast (for a brief shining moment).
I would also regret it if they become that fast; right now I can really take a moment to enjoy the hard work the model is doing for me.
Simply search user prompts for curse words and then measure hostility sentiment. User hostility rises as agents fail to meet expectations.
Maybe im overlooking something obvious but how do you 'simply' scan the content of Claude users their prompts?
GP was making a joke, but Anthropic could implement this if they wanted to. Not a bad metric actually if you can measure it cheaply enough.
I uh might be skewing that as I generally just use a lot of curse words with Claude by default
I'm glad I'm not the only one.
One time I cussed Claude out so hard that it actually quit his doom-loop and fixed the thing.
It's the only time cussing worked, though.
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I feel bad about it but sometimes it's so daft, I can't even xD
It's not my fault, they set high standards!
There’s a correlation between getting the “How’s Claude Doing This Session?” (Or whatever) and four letter words.
It’s not always then, but it often follows it.
there are many times where I just do it myself and it thinks it did well.
Or there are global events that stress people out .. or their expectations change over time. Not that simple ;)
Good thing expectations are perfectly constant!
This might be strangely effective.
Running agents in production, I've stopped trying to figure out why things degrade. The answer changes weekly.
Model drift, provider load, API changes, tool failures - it doesn't matter. What matters is that yesterday's 95% success rate is today's 70%, and by the time you notice, debug, and ship a fix, something else has shifted.
The real question isn't "is the model degraded?" It's "what should my agent do right now given current conditions?"
We ended up building systems that canary multiple execution paths continuously and route traffic based on what's actually working. When Claude degrades, traffic shifts to the backup path automatically. No alerts, no dashboards, no incident.
Treating this as a measurement problem assumes humans will act on the data. At scale, that assumption breaks.
Does this even make sense? Clearly anthropic won't release a model unless it passed a benchmark of some sort that proves it's better than the previous model... or else why would they even release it?
It's obvious if this thing shows degradation, than there is another thing that is showing improvement.
Wouldn't be surprised if they slowly start quantizing their models over time. Makes it easier to scale and reduce operational cost. Also makes a new release have more impact as it will be more notably "better" than what you've been using the past couple of days/weeks.
It sure feels like they do this. They claim they don't, but using it every day for 5-10 hours a day. You notice when something changes.
This last week it seems way dumber than before.
I don't think so. There are other knobs they can tweak to reduce load that affect quality less than quantizing. Like trimming the conversation length without telling you, reducing reasoning effort, etc.
We never do anything that reduce model intelligence like that
Open weights models such as GPT-OSS, Kimi K2.x are trained with 4 bit layers. So it wouldn't come as a surprise if the closed models do similar things. If I compare Kimi K2.5 and Opus 4.5 on openrouter, output tokens are about 8x more expensive for Opus, which might indicate Opus is much larger and doesn't quantize, but the claude subscription plans muddy the waters on price comparison a lot.
I would be surprised tbh.
Anthropic does not exactly act like they're constrained by infra costs in other areas, and noticeably degrading a product when you're in tight competition with 1 or 2 other players with similar products seems like a bad place to start.
I think people just notice the flaws in these models more the longer they use them. Aka the "honeymoon-hangover effect," a real pattern that has been shown in a variety of real world situations.
Oooff yes I think that is exactly the kind of shenanigans they might pull.
Ultimately I can understand if a new model is coming in without as much optimization then it'll add pressure to the older models achieving the same result.
Nice plausible deniability for a convenient double effect.
I haven't noticed much difference in Claude, but I swear gemini 3 pro preview was better in the first week or two and later started feeling like they quantized it down to hell.
Benchmarks like ARG AGI are super price correlated and cheap to run. I think it's very easy to prove that the models are degrading.
I am using API mode, and it's clear that there are times when the Claude model just gives up. And it is very noticeable because the model just does the most dumb things possible.
"You have a bug in line 23." "Oh yes, this solution is bugged, let me delete the whole feature." That one-line fix I could make even with ChatGPT 3.5 can't just happen. Workflows that I use and are very reproducible start to flake and then fail.
After a certain number of tokens per day, it becomes unusable. I like Claude, but I don't understand why they would do this.
Robbing Peter to pay Paul. They are probably resource-constrained, and have determined that it's better to supply a worse answer to more people than to supply a good answer to some while refusing others. Especially knowing that most people probably don't need the best answer 100% of the time.
> Especially knowing that most people probably don't need the best answer 100% of the time.
More: probably don't know if they've got a good answer 100% of the time.
It is interesting to note that this trickery is workable only where the best answers are sufficiently poor. Imagine they ran almost any other kind of online service such email, stock prices or internet banking. Occasionally delivering only half the emails would trigger a customer exodus. But if normal service lost a quarter of emails, they'd have only customers who'd likely never notice half missing.
Right. You can launder quantization that way by muddying the waters of discourse about the model.
I encountered the same situation too; Claude has 'become lazy'.
FYI the MarginLab Claude Code degradation tracker is showing a statistically significant ~4% drop in SWE-Bench-Pro accuracy over the past month
Lack of transparency as regards "thinking power"-consistency is a big gripe of mine with LLM providers. It's even worse with ChatGPT and the like. E.g. I had to learn the hard way that at >45k input tokens ChatGPT 5.2 Thinking Extended bumps its intelligence down so hard that it can't follow basic instructions (or it somehow truncates the input, losing the instructions). It sucks to lose confidence in an otherwise great tool. I would 100x prefer being forced to back-off, or getting a straight-no, than getting silently downgraded. Transparency is a big deal.
Sounds like you ran into the Maximum Effective Context Window: https://arxiv.org/abs/2509.21361?context=cs.AI
Interesting article. Not sure it's the same phenomenon. What I experienced was like a day and night difference when you go from 44.5k to 45.5k. Didn't notice any fluctuation to suggest that it's no a hard 45000 limit. I ran many many queries, similar problem space, but the problems varied a lot.
I really like the idea, but a "±14.0% significance threshold" is meaningless here.
The larger monthly scale should be the default, or you should get more samples.
Could you elaborate what you think the problems are? I guess they should be using some form of multiple comparison correction?
The daily scale is not statistically significant and is meaningless. You should lower the confidence interval by either increasing the scale or the evaluations.
Benchmark tracking of cloud AI performance is going to be crucial going forward. Vendors are selling a service that by its nature is very difficult for customers to gauge day to day. How will I know if a code revision is ~2.5% less good today than it would have been yesterday? Or if queries during peak load hours use one less 'expert' in their MoE?
Yet vendor's costs to deliver these services are skyrocketing, competition is intense and their ability to subsidize with investor capital is going away. The pressure on vendors to reduce costs by dialing back performance a few percent or under-resourcing peak loads will be overwhelming. And I'm just a hobbyist now. If I was an org with dozens or hundreds of devs I'd want credible ways to verify the QoS and minimum service levels I'm paying for are being fulfilled long after a vendor has won the contract.
Totally tangential to article, was browsing through the website UI - https://marginlab.ai/explorers/swe-bench-pro/ , the page gives impression that the language, category boxes are selectable. However they are not a dropdown. Not sure if it was intentional design by human or some smart code generation by Claude based on the design sketches.
New to me, but I am starting to infer that for those "in the know" it is common knowledge on HN that LLMs are purposely degraded over time to manage capacity/cost or fudge benchmarks...
How do you actually use these in production pipelines in practice then?
Are LLMs even well suited for some of the document parsing / data scrubbing automation people are throwing at them now?
This is super important - even if it's not currently the best measure of degradation yet. Anecdotally, Opus 4.5 has gotten so bad for me it's almost adding time to my workflow instead saving it. It'd be nice to have more 3rd party measurements like this to hold Anthropic accountable.
If the confidence interval width is 2 * 14.0%, how are you detecting a statistically significant difference between 58% and 50%?
The 95% CIs on both timeseries pretty much always cover the baseline number, which is not consistent with the result being statistically significant.
Please try to make this statistically rigorous. There's lots of advice in this thread (intraday variation, etc) but if Im reading this right it looks like the CI includes the baseline value yet you still label this as failing.
Wouldn't this just be "our test isn't powerful enough to find a signal if there were one here?"
People will see this and derive strong conclusions that the data don't support and you, `qwesr123`, or "JB" from your blogs, will be responsible.
ive seen degraded reasoning levels that feel like they they might be blur from excess quantization. cause thats what you get from the grid changes
Does it benchmark the underlying code (Opus 4.5) or Claude Code harness? If the second, I would love to see CC versions involved.
I would be curious to see on how it fares against a constant harness.
There were thread claiming that Claude Code got worse with 2.0.76, with some people going back to 2.0.62. https://github.com/anthropics/claude-code/issues/16157
So it would be wonderful to measure these.
Claude Code. They mention they are using claude codes CLI in the benchmark, and claude code changes constantly.
I wouldn't be surprised if the thing this is actually testing is benchmarking just claude codes constant system prompt changes.
I wouldn't really trust this to be able to benchmark opus itself.
Does this use a claude subscription or key, and has the account been used for anything else that day?
On HN a few days ago there was a post suggesting that Claude gets dumber throughout the day: https://bertolami.com/index.php?engine=blog&content=posts&de...
This strategy seems inspired by TikTok's approach for retaining new uploaders.
TikTok used to give new uploaders a visibility boost (i.e., an inflated number of likes and comments) on their first couple of uploads, to get them hooked on the the service.
In Anthropic/Claude's case, the strategy is (allegedly) to give new users access to the premium models on sign-up, and then increasingly cut the product with output from cheaper models.
Yes, but the difference is TikTok didn't sell a particular service version.
Anthropic did sell a particular model version.
What would be cool if this somehow could do a comparison by provider. E.g. in the last outages anthropic models running on vertex were apparently less affected than those deployed elsewhere. (Not saying that one is better than the other, but would be a neat read out).
I hope the author sees this:
You have to test inter-day variation. Many have noticed a sudden drop off at certain times.
I’d love to see, based on the level of non-determinism perfomance on the benchmark how many times you need to run the benchmark for the change to be relevant (or statistically significant if you want).
That would be a nice paper.
What makes the level they chose a “baseline,” against which it would be appropriate to do statistical tests?
First off, this is a cool project, look forward to some interesting insights.
I would suggest adding some clarification to note that longer measure like 30 pass rate is raw data only while the statistically significant labels apply only to change.
Maybe something like Includes all trials, significance labels apply only to confidence in change vs baseline.
I’ve noticed Claude has been noticeably worse over the last week. For example, it told me I should pass frozen to make my Enum immutable—that’s not a thing. (It is a thing for dataclasses, but not for Enums.) That’s a pretty basic language feature it was nailing until recently. It also suggested I parse a URL using urlparse in a function that already uses urlparse. These are basic mistakes it wasn’t making before. Something seems to have changed, but I’m not sure what.
Very interesting. I would be curious to understand how granular these updates are being applied to CC + what might be causing things like this. I feel like I can notice a very small degradation but have compensated with more detailed prompts (which I think, perhaps naively, is offsetting this issue).
> more detailed prompts (which I think, perhaps naively, is offsetting this issue).
Is exacerbating this issue ... if the load theory is correct.
Codex is doing better. Why is everyone silent on Codex? https://marginlab.ai/trackers/codex/
Benchmark wins don't necessarily translate to "real world" wins vs. Claude Code.
Codex writes disgusting shit code.
they should run their test against a control baseline such as an open source hosted model to see the overall drift in their test
I would pay 300 for a non-degrading Max plan.
I KNEW I WASNT CRAZY
Why is this happening?
They're "optimizing" costs wherever possible - reducing compute allocations, quantizing models, doing whatever they can to reduce the cost per token, but vehemently insisting that no such things are occurring, that it's all in the users' heads, and using the weaseliest of corporate weasel speak to explain what's happening. They insist it's not happening, then they say something like "oh, it happened but it was an accident", then they say "yes, it's happening, but it's actually good!" and "we serve the same model day by day, and we've always been at war with Eastasia."
They should be transparent and tell customers that they're trying to not lose money, but that'd entail telling people why they're paying for service they're not getting. I suspect it's probably not legal to do a bait and switch like that, but this is pretty novel legal territory.
I have absolutely no insight knowledge, but I think it's not a bad assumption to have that, it's costly to run the models, when they release a new model they assume that cost and give per user more raw power, when they've captured the new users and wow factor, they start reducing costs by reducing the capacity they provide to users. Rinse and repeat.
That is absolutely scummy.
There are frequently claims that Anthropic is somehow diluting or dumbing down models in some subtle way. Unfortunately it’s tough to validate these claims without a body of regularly checked evals. This test set should hopefully help settle whether Anthropic is actually making changes under the hood or whether the changes are all in people’s heads.
https://www.anthropic.com/engineering/a-postmortem-of-three-...
>>> We never reduce model quality due to demand, time of day, or server load. The problems our users reported were due to infrastructure bugs alone.
Just ignore the continual degradation of service day over day, long after the "infrastructure bugs" have reportedly been solved.
Oh, and I've got a bridge in Brooklyn to sell ya, it's a great deal!
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It’s entirely possible it’s not happening, and this phenomenon of “model degradation” is just user hype meeting reality.
Tracking benchmarks for AI-assisted coding tools is crucial. It helps developers understand the trade-offs and stability of the models they rely on.
I have yet to experience any degradation in coding tasks I use to evaluate Opus 4.5, but I did see a rather strange and reproducible worsening in prompt adherence as part of none coding tasks since the third week of January.
Very simple queries, even those easily answered via regular web searching, have begun to consistently not result accurate results with Opus 4.5, despite the same prompts previously yielding accurate results.
One of the tasks that I already thought was fully saturated as most recent releases had no issues in solving it was to request a list of material combinations for fabrics used in bag constructions that utilise a specific fabric base. In the last two weeks, Claude has consistently and reproducibly provided results which deviate from the requested fabric base, making the results inaccurate in a way that a person less familiar with the topic may not notice instantly. There are other queries of this type for other topics I am nerdily familiar with to a sufficient degree to notice such deviations from the prompt like motorcycle history specific queries that I can say this behaviour isn't limited to the topic of fabrics and bag construction.
Looking at the reasoning traces, Opus 4.5 even writes down the correct information, yet somehow provides an incorrect final output anyways.
What makes this so annoying is that in coding tasks, with extensive prompts that require far greater adherence to very specific requirements in a complex code base, Opus 4.5 does not show such a regression.
I can only speculate what may lead to such an experience, but for none coding tasks I have seen regression in Opus 4.5 whereas for coding I did not. Not saying there is none, but I wanted to point it out as such discussions are often primarily focused on coding, where I find it can be easier to see potential regressions where their are none as a project goes on and tasks become inherently more complex.
My coding benchmarks are a series of very specific prompts modifying a few existing code bases in some rather obscure ways, with which I regularly check whether a model does severely deviate from what I'd seen previously. Each run starts with a fresh code base with some fairly simple tasks, then gets increasingly complex with later prompts not yet being implemented by any LLM I have gotten to test. Partly that originated from my subjective experience with LLMs early on, where I found a lot of things worked very well but then as the project went on and I tried more involved things with which the model struggled, I felt like the model was overall worse when in reality, what had changed were simply the requirements and task complexity as the project grew and easier tasks had been completed already. In this type of testing, Opus 4.5 this week got as far and provided a result as good as the model did in December. Of course, past regressions were limited to specific users, so I am not saying that no one is experiencing reproducible regressions in code output quality, merely that I cannot reproduce them in my specific suite.
I've noticed a degradation in Opus 4.5, also with Gemini-3-Pro. For me, it was a sudden rapid decline in adherence to specs in Claude Code. On an internal benchmark we developed, Gemini-3-Pro also dramatically declined. Going from being clearly beyond every other model (as benchmarks would lead you to believe) to being quite mediocre. Delivering mediocre results in chat queries and coding also missing the mark.
I didn't "try 100 times" so it's unclear if this is an unfortunate series of bad runs on Claude Code and Gemini CLI or actual regression.
I shouldn't have to benchmark this sort of thing but here we are.
Write your work order with phases (to a file) and, between each phase, give it a non-negotiable directive to re-read the entire work order file.
Claude-Code is terrible with context compaction. This solves that problem for me.
I definitely noticed a degradation, it feels regressed by a generation.
Would love to see this idea expanded to ever alleged SoTA model currently in production. Any speculation as to why this degradation occurs?
Anecdote, I don't have any proof and it's just a feeling. But around afternoon in GMT+1 compared to the morning/midday, there seems to be a change in the quality of responses, which seems to line up with when the US wakes up. I consistently get (what feels like) worse responses in both Codex and Claude Code in the afternoon/night compared to morning/midday, so much that I usually give up then try the same prompt next morning and get better results. But I guess that might as well be about me being more tired in the night than morning too, as I said, haven't measured this.
It’s the afternoon slump. The AI needs a cup of coffee and to doomscroll for half an hour!
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would be interesting to see what scores it's get when it is actually degraded via the status page, it gets degraded pretty often, so there's at least something to compare or to know at what point Anthropic declares degradation
The chart would benefit from having weekends highlighted. Or have another chart averaged by a weekday.
In medicine there is a concept of reporting adverse effects of medication or interventions which are then collectively studied for Public Health [MedWatch][VAERS][EudraVigilance] and in academia. We should have something like that for all coding agents(and agents in other fields too), given how widely its deployed and affect on "health" in general(not only human). Call it the AI "health" of things benchmark.
I would imagine a sort of hybrid qualities of volunteer efforts like wikipedia, new problems like advent of code and benchmarks like this. The goal? It would be to study the collective effort on the affects of usage to so many areas where AI is used.
[MedWatch](https://www.fda.gov/safety/medwatch-fda-safety-information-a...)
[VAERS](https://www.cdc.gov/vaccine-safety-systems/vaers/index.html)
[EudraVigilance](https://www.ema.europa.eu/en/human-regulatory-overview/resea...)
My personal conspiracy theory is that they choose who to serve a degraded model to based on social graph analysis and sentiment analysis, maximizing for persuasion while minimizing compute.
IMO this strategy seems inspired by TikTok's approach for retaining new uploaders.
TikTok used to give new uploaders a visibility boost (i.e., an inflated number of likes and comments) on their first couple of uploads, to get them hooked on the the service.
In Anthropic/Claude's case, the strategy is (allegedly) to give new users access to the premium models on sign-up, and then increasingly cut the product with output from cheaper models.
Of course, your suggestion (better service for users who know how to speak Proper English) would be the cherry on top of this strategy.
From what I've seen on HackerNews, Anthropic is all-in on social media manipulation and social engineering, so I suspect that your assumption holds water.
I would actually assume a little more sophistication. For each user, a measure of "Are they convinced that AI is great". Then, you weaponize your compute to have the maximum social impact. If somebody has a large following (many edges on the social graph), and theyre skeptical of AI tech, inject the expensive but effective models directly into their veins. Let them taste the joy. Then start watering down their dose, and move onto the next person in the graph, again maximizing for net social impact. Language may not even be a consideration
Sounds more like a sound business plan than a conspiracy theory.
It sounds like fraud to me
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I’m sure there is not enough data here for this to be statistically significant (it seems to oscillate too much and not show real trends or step changes) - BUT
If this measure were hardened up a little, it would be really useful.
It feels like an analogue to an employee’s performance over time - you could see in the graphs when Claude is “sick” or “hungover”, when Claude picks up a new side hustle and starts completely phoning it in, or when it’s gunning for a promotion and trying extra hard (significant parameter changes). Pretty neat.
Obviously the anthropomorphising is not real, but it is cool to think of the model’s performance as being a fluid thing you have to work with, and that can be measured like this.
I’m sure some people, most, would prefer that the model’s performance were fixed over time. But come on, this is way more fun.
Finally someone did it! We need this for all models.
Could this be (partially?) explained by Model Collapse [1], i.e. iteratively training on data that includes an ever increasing amount of AI slop?
[1] https://thebullshitmachines.com/lesson-16-the-first-step-fal...
That will be great if there's RSS support.
The degradation does not need to be in the inference it can be in how often inference is used.
It is closed source but the algorithms that decide what Claude code does when, could behave differently when the API responses are slower. Maybe it does fewer investigatory greps or performs fewer tasks to get to “an” answer faster and with less load.
any chance we can get something like this for codex cli that'd be cool too compare
This is why I run my own models. All the inference providers do sneaky things behind the scenes. They will limit the output tokens, turn off attention layers, lower reasoning, or just use a completely different model. I'm actually surprised that Claude Code experienced this, as I've experienced this the least from API and coding agents.
Call it what you will. But the experience is like you have a reliable coworker, but he randomly decides to take bong hits.
"No no yeah bro no I'm good like really the work's done and all yeah sorry I missed that let me fix it"
I wonder when I experience noticeably degraded model quality, ie opus, is it because my usage falls in the highest buckets and I’m being shadow limited or served worse versions of opus or is it because of actual server load/burden?
It wouldn’t be the first time companies have secret shadow algorithms running to optimize things and wouldn’t it be obvious to limit power users as matter of cost/profit and not tell them. (See history of “Shadow ban” though that’s for different reasons)
Pretty sure someone at Google, OpenAI, and Anthropic met up at a park, leaving their phones in their car, and had a conversation that January 2026, they were all going to silently degrade their models.
They were fighting an arms race that was getting incredibly expensive and realized they could get away with spending less electricity and there was nothing the general population could do about it.
Grok/Elon was left out of this because he would leak this idea at 3am after a binge.
> We model tests as Bernoulli random variables and compute 95% confidence intervals around daily, weekly, and monthly pass rates. Statistically significant differences in any of those time horizons are reported.
Doesn't really work like that. I'd remove the "statistically significant" labelling because it's misleading.
This is probably entirely down to subtle changes to CC prompts/tools.
I've been using CC more or less 8 hrs/day for the past 2 weeks, and if anything it feels like CC is getting better and better at actual tasks.
Edit: Before you downvote, can you explain how the model could degrade WITHOUT changes to the prompts? Is your hypothesis that Opus 4.5, a huge static model, is somehow changing? Master system prompt changing? Safety filters changing?
Honest, good-faith question.
Is CC getting better, or are you getting better at using it? And how do you know the difference?
I'm an occasional user, and I can definitely see improvements in my prompts over the past couple of months.
I agree with you, it's personally hard to tell.
For me I've noticed it getting nothing but better over the past couple months, but I've been working on my workflows and tooling.
For example, I used to use plan mode and would put everything in a single file and then ask it to implement it in a new session.
Switching to the 'superpowers' plugin with its own skills to brainstorm and write plans and execute plans with batches and tasks seems to have made a big improvement and help catch things I wouldn't have before. There's a "get shit done" plugin that's similar that I want to explore as well.
The code output always looks good to me for the most part though and I've never thought that it's getting dumber anything, so I feel like a lot of the improvements I see are because of a skill issue on my part trying to use everything. Obviously it doesn't help there's a new way to do things every two weeks though.
I run an LLM based product in a completely different space (consumer) and I think this is kind of an impossible unsolvable part of developing products that rely on LLMs.
No matter what, powers users always say the model is degrading over time*. Even when every stat I have access to says otherwise.
(* to clarify, this is outside of actual model changes)
I suspect some of it is the fact context windows growing does harm performance, and early on you're more likely to be prodding at things in a way that has a smaller context window on average.
But I also think users just inherently are less reliable narrators than they think. They say they're trying the same tasks, but it may be the "same task" applied to a codebase with 1 month's more worth of development and complexity.
Or it's the "same task" but their less confident past self was "Clever Hans"-ing the model with some nuance that they've since discarded without realizing.
Or it's simple expectation creep and the tasks aren't similar at all from an LLM perspective due to limited generalization, but from a human perspective are. Switching languages might as well make it a new task as far LLM performance for example, but the human considers it the same task in a new language.
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Whatever causes it, it's especially stressful because sometimes you do degrade the harness entirely accidentally but it's impossible to separate that signal from the noise from user accounts and an issue goes unfound way longer than it should.
Claude Code is somewhat fortunate that code has verifiable aspects though, so you don't need to 100% go on user account. My usecase relies much more on subjective preference, so dealing with this stuff becomes the 9th circle of hell.
There've been many times when a change to the LLM stack didn't make it to prod, I jumped the gun on announcing it, but users immediately flooded in with praise that the "missing" performance had returned.
Good-faith answer: I can't be certain. But I've been using CC since its release, and Cursor before that (and actually going all the way back to GPT3 to do codegen in the Playground). After getting used to the CC workflow, the way that I use it has been pretty consistent. To be specific, I use basically the same AGENTS.md with small modifications for each project, and I live almost exclusively in Plan mode and the best model (currently Opus 4.5).
My initial prompting is boilerplate at this point, and looks like this:
(Explain overall objective / problem without jumping to a solution)
(Provide all the detail / file references / past work I can think of)
(Ask it "what questions do you have for me before we build a plan?")
And then go back and forth until we have a plan.
Compared to my work with CC six months ago, it's just much more capable, able to solve more nuanced bugs, and less likely to generate spaghetti code.
That's why benchmarks are useful. We all suffer from the shortcomings of human perception.
Benchmarks shortcomings are no worse... they inevitably measure something that is only close to the thing you actually care about, not the thing you actually care about. It's entirely plausible that this decreased benchmark score is because Anthropic's initial prompting of the model was overtuned to the benchmark and as they're gaining more experience with real world use they are changing the prompt to do better at that and consequentially worse at the benchmark.
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Benchmarks measure what they measure. But your subjective experience also matters.
The easiest way would be to quantize the model, and serve different quants based on the current demand. Higher volumes == worse quant == more customers served per GPU
I was going to ask, are all other variables accounted for? Are we really comparing apples to apples here? Still worth doing obviously, as it serves a good e2e evaluations, just for curiosity's sake.
I upvoted, but
> Edit: Before you downvote, can you explain how the model could degrade WITHOUT changes to the prompts?
The article actually links to this fine postmortem by anthropic that demonstrates one way this is possible - software bugs affecting inference: https://www.anthropic.com/engineering/a-postmortem-of-three-...
Another way this is possible is the model reacting to "stimuli", e.g. the hypothesis at the end of 2023 that the (then current) ChatGPT was getting lazy because it was finding out the date was in december and it associated winter with shorter lazier responses.
A third way this is possible is the actual conspiracy version - Anthropic might make changes to make inference cheaper at the expense of the quality of the responses. E.g. quantizing weights further or certain changes to the sampling procedure.
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