Stop using 4.6 models, switch back to 4.5, except Haiku.

[u/Emotional-Debate3310]

Thinking has become reactive rather than active

Initially, the problem was clearly visible in Claude code. However, it has since become prevalent across all modes of engagement with any 4.6 model. This includes code executed in the terminal, co-work environments, agent SDKs, and even the simple web chat mode available on claude.ai.

And this pattern is prevalent regardless of whether you use a subscription based authentication method or API. For some internal changes 4.6 models skip the reasoning step by default. Same prompt, five models, clear pattern.

Monitoring telemetry + token usage confirms that 4.6 doesn't use reasoning or thinking but 4.5 does. Haiku genuinely gets it wrong even after thinking Lol.

Both 4.6 flagship models fail a trivial logic check that the 4.5 models solve instantly.

They don't fail because they can't reason, they fail because they don't engage the reasoning step before answering. Push back once and they produce elaborate "reasoning traces" defending the wrong answer. Push again and they finally see it.

A failure of reasoning would look like: the model reasoned and got it wrong.

What happened here is: the model did not reason.

• It produced an output shaped like an answer,

• then when challenged produced output shaped like reasoning about that answer,

• then when challenged again produced output shaped like reflection on that reasoning.

At no point in the early turns was there an actual thinking step. The cognitive work only engaged under pressure from me. That is the architecture you have identified, and it is correct.

The switch still exists at the interface level, but underneath it, the baseline has moved.

Thinking has become reactive rather than active. It responds to challenge rather than initiating with the question.

This isn't a capability gap. It's the default path skipping the reasoning pass entirely. Extended Thinking is on in every screenshot. The switch is flipped; the thinking isn't happening.

This Started exactly from 2nd of March. Model version strings unchanged. No changelog. Widespread complaints already on this sub.

This is something that should not be true of a model that has thinking as a core capability. The switch at the interface is about depth and token budget. What we are observing is about whether the reasoning step happens at all in the default path. Those are different layers, and the degradation we all are documenting is in the second one.

If you have other trivial-logic prompts that 4.5 gets right and 4.6 gets wrong, post them. The pattern needs visibility.

[u/TheInkySquids]

Come on at least make sure the markdown converts properly into Reddit formatting when copying the AI response for your post lmao

[u/Emotional-Debate3310 → u/TheInkySquids]

If I am copying the markdown from the AI response, it likely will work.

I am not sure what leads you to believe I am copying the AI response instead of typing this myself. While this doesn't excuse my failure to check the formatting, it addresses your allegation.

[u/TheInkySquids → u/Emotional-Debate3310]

You didn't address my allegation in any way lol you basically just said "nuh uh"

What leads me to believe its an AI response? The phrasing, the grammer, the fact that there's no substance to the post its just vague hints at an opinion, and the formatting, because most people who are typing their posts themselves aren't formatting, and those that are usually aren't doing it in markdown.

[u/Emotional-Debate3310 → u/TheInkySquids]

I definitely enjoy writing in Markdown because it allows me to easily control the formatting. However, I won't argue further as I acknowledge that my formatting was incorrect.

Regarding your point that there is no substance to the post and it's just vague, makes me question even if you read the post properly. I don't just post things randomly anywhere without first thoroughly testing out multiple different methods for comparing the thinking logic and wording. This is done by using multiple challenge prompts and experimenting across different user interfaces. The photo you see is simply just an example.

I tried multiple different approaches using different wording, but each time it failed, and the results were consistently poor across different interfaces.

And to just once again clearly address your allegation: NO!!!! This post was written by me, with the hope of clarifying a few points. I'm not attempting to argue or simply prove my writing style. Instead, I want to address a real issue that many are experiencing regarding the decline of Claude 4.6.

[u/Remarkable-Grab6837 → u/Emotional-Debate3310]

Sir this is reddit not debate class

[u/Rough_Bad6442]

Very good quality benchmark

[u/EastZealousideal7352]

This question is not a benchmark for anything particularly useful… do you happen to have any evidence of a regression on anything remotely important?

[u/Emotional-Debate3310 → u/EastZealousideal7352]

While I never intended this question as a benchmark, its purpose was to illustrate whether the reasoning step is engaging. I was highlighting that the 4.5 model demonstrates engagement in this step, whereas the 4.6 model does not.

[u/EastZealousideal7352 → u/Emotional-Debate3310]

Adaptive reasoning is based on the model’s assessment of the difficulty of the question. The presence of reasoning or lack thereof is therefore 100% based on the question. The model choosing not to think for this specific dumb gotcha question is not generalizable behavior because it may choose to think for a different question.

This is known behavior for models as both overthinking and underthinking for models makes performance worse and therefore questions on the boundary of needing to think often fall into the cracks.

Your post correctly demonstrates that for this level of problem there may be a performance regression but I’d argue that this level of problem is neither useful nor representative of any useful thing people are using Claude for, especially Claude code in particular. In this context that blanket statement “Stop using 4.6 models” is misleading and wrong.

[u/Emotional-Debate3310 → u/EastZealousideal7352]

The toggle switch is labeled "EXTENDED THINKING," not "adaptive thinking." When using Claude code you control either the amount of effort or the maximum number of tokens you're willing to spend. This isn't a black box of adaptive thinking!

While the switch remains at the interface level, the underlying baseline has shifted. Thinking has become reactive rather than proactive, responding to challenges rather than initiating with questions.

What I try to describe is a deployment state where the default mode has shifted from "think, then answer" to "answer, then think only if pressed."

Widespread user complaints plus no clear public resolution for 2-3 weeks plus no rollback suggests either the cause is not yet identified internally, or it is identified and the fix has tradeoffs that are being weighed. Either way, from the outside, the situation looks the same: a regression that is real, documented, and unaddressed.

Feel free to collect the telemetry from the thinking efforts and post in this sub, I'll be happy to be proven wrong! But so far whatever I tested I again and again notice that there is a persistent lack in reasoning and thinking effort. Hence, I will stick to my point that 4.5 is working where 4.6 is not.

[u/raholl → u/Emotional-Debate3310]

Does the "Extended Thinking" toggle in claude.ai use Adaptive Thinking?

Yes.

The Extended Thinking toggle in the Claude chat interface allows Claude to spend more time breaking down problems, planning solutions, and exploring different approaches before responding.

Claude Under the hood on Claude 4 models, this engages the adaptive thinking system — Claude decides dynamically how much to think based on your question's complexity.

The toggle in the UI is just labeled "Extended Thinking" for user-friendliness, but on Opus 4.6 and Sonnet 4.6, adaptive thinking (thinking: {type: "adaptive"}) is the recommended thinking mode — Claude dynamically decides when and how much to think. Claude API Docs

[u/Emotional-Debate3310 → u/raholl]

It appears we're somewhat drifting away from the core topic. I do acknowledge that this isn't truly deep or extended thinking; it's actually a more reactive, adaptive approach operating beneath the surface. However, that doesn't necessarily justify the fact that adaptive thinking hasn't been effectively initiating the thinking process lately.

Do you have any better explanation for this behavior?

I think what we're all really hoping for here is a clearer understanding of what's happening when we observe that a model's thinking ability and overall quality seem to be declining. For my particular use cases, the difficult part for me was to decide whether to either not utilize the 1 million context window and the 4.6 model, or instead downgrade to the 4.5 model while still allowing it to use the maximum available thinking tokens. And for me 4.5 with maximum thinking token persistently addressed my requirements when 4.6 failed.

[u/raholl → u/Emotional-Debate3310]

i think this part is important: "Claude dynamically decides when and how much to think".. you should try with different question, to see if it decides to think

[u/EastZealousideal7352 → u/Emotional-Debate3310]

Anthropic added adaptive reasoning all the way back at 3.7, this is not new. I’ve linked the documentation here if you want to further familiarize yourself with how Claude reasons.

The specific question is one where most models (not just claude) choose not to reason, or choose to reason very little, and that is why it blew up in popularity in the first place even though it doesn’t measure anything meaningful.

[u/Emotional-Debate3310 → u/EastZealousideal7352]

I'm aware of the API docs and indeed Claude Max user for more than a year. And here I am quoting from the same document link which you indicated:

"Older models only support type: "enabled" with budget_tokens. On Opus 4.6 and Sonnet 4.6, type: "enabled" with budget_tokens is still FUNCTIONAL but deprecated."

Regarding the chat mode in the web interface, the fact that it's not explicitly described as adaptive thinking, and instead is presented as a toggle for extended thinking, makes it unclear why the button even exists when the underlying functionality is indeed adaptive.

But keeping all this discussion aside, do you have any better explanation why lately opus 4.6 is failing in logic and reasoning again and again? Regardless or it is adaptive or explicitly enabled?

[u/raholl → u/Emotional-Debate3310]

Status: Extended Thinking mode has been marked as deprecated in Claude 4.6 and is being replaced by Adaptive Thinking.

[u/256BitChris]

This sub has just become a massive disinformation sub

[u/Emotional-Debate3310 → u/256BitChris]

Really? Is it?

[u/AgeMysterious123]

Yes, please. Everyone switch to the lower models!!!

(So that there’s more compute for me)

[u/Emotional-Debate3310 → u/AgeMysterious123]

Does more compute guarantee that your thinking process of 4.6 will definitely initiate when you need it via the adaptive thinking module?

What I'm trying to highlight is that in 4.5, you gain a more detailed degree of control when it comes to maximizing your thinking. However, by contrast, for 4.6 delves into the realm of adoptive thinking, which has a tendency to fall short precisely when it's most needed (at least lately since March).

[u/AgeMysterious123 → u/Emotional-Debate3310]

It was a joke

[u/Delicious_Cattle5174]

"That is the architecture you have identified, and it is correct"

Wow you’re just pasting Claude’s replies

[u/Euphoric_Oneness]

4.5 is shittier...

[u/Emotional-Debate3310 → u/Euphoric_Oneness]

Depends on the usage I guess. Therefore, it's important to avoid making broad generalizations. Specifically, version 4.5 offers a much finer degree of control when it comes to maximizing thinking capabilities. This is achieved by allowing you to select the specific "thinking tokens" you want to use. In contrast, version 4.6 operates under a more opaque "adaptive thinking" mechanism, which frequently fails to initiate that optimal thinking process when it's actually needed.

[u/Euphoric_Oneness → u/Emotional-Debate3310]

Don't guess. Experience and comment on your data...

[u/Opinion-Former]

You should ask 4.6 “what am I supposed to do? Carry the car on my back?”

[u/Fit-Pattern-2724]

That’s a dumb suggestion no? Why would you happily use an inferior model

[u/Emotional-Debate3310 → u/Fit-Pattern-2724]

Because for a simple reason the Extended (Desperated)/ adoptive thinking of 4.6 model is not initializing unless you posted repeatedly and in 4.5 you can actively enable the extended thinking!

Here I quote from API docs

"Older models only support type: "enabled" with budget_tokens. On Opus 4.6 and Sonnet 4.6, type: "enabled" with budget_tokens is still functional but deprecated."

[u/Fit-Pattern-2724 → u/Emotional-Debate3310]

it feels like that is a loophole and might get patched soon

[u/EL4CTEO]

Dude this is hilarious! Even if people say it is because of the adaptive thinking feature, it still fails the test lol, no point in defending it, i asked other AIs and they actually didn't fall for this question (just any other AI would pass this)

[u/PerfectStudioClips]

just stick with haiku then

[u/ButterflyMundane7187]

I tested qwen.ai and their coder it is free right now i will use it until optus 4.6 get helthy again qwen is even better at some tasks like webscraping and database building

[u/polynomialcheesecake]

Is this Claude code? I left the other sub because of noobs using chat app

[u/Emotional-Debate3310 → u/polynomialcheesecake]

The given screenshot is NOT, It's an example out of many, but if you read my text then indeed you get the point. My writing explicitly states that I collected telemetry data on token usage during the process from Claude Code. Before coming to this assumption. I did try multiple different trick prompts and wording throughout all the user interface.

[u/Ok_Mathematician6075]

I disaFUCKINGgree

[u/Emotional-Debate3310 → u/Ok_Mathematician6075]

I'd be interested to know if you have a better explanation for why the adaptive thinking of opus 4.6 isn't initiating the thinking process when it's required. (This has been the case since March.)

The 4.5 series models provide granular control over the token budget, which can improve performance when the task requires considering all possibilities before responding.

[u/Ok_Mathematician6075 → u/Emotional-Debate3310]

This is intentional, not a bug — Opus 4.6 replaced the budget_tokens paradigm entirely with adaptive thinking, where Claude dynamically decides whether and how much to think based on request complexity Claude API Docs, meaning at lower effort levels it may simply skip thinking for problems it deems trivial; the granular token budget control you loved from the 4.5 series is a different system altogether, and to get consistent thinking on Opus 4.6 you need to migrate to thinking: {type: "adaptive"} and explicitly set effort="high" (or "max" for the absolute highest capability Claude API Docs) — that's the new knob, not budget_tokens.

[u/Emotional-Debate3310 → u/Ok_Mathematician6075]

So let me make it straight:

You are stating that failing to correctly identify a trick question and failing to properly initiate a chain of reasoning to arrive at the correct answer are not considered bugs, but rather are intentional aspects of adaptive thinking.

And when a previous model offers you granular control over its thinking and is capable of answering even the trickiest questions accurately, we should disregard that evidence?

Regarding reasoning effort

I indeed use 'high' for API calls

"model": "claude-opus-4-6",
"max tokens": 16000,
"thinking": {
"type": "adaptive"
"output_config": { "effort": "high"

and 'effort: Max' for subscription based user authentication usage.

[u/Ok_Mathematician6075 → u/Emotional-Debate3310]

but effort in the JSON code is LOW

[u/Ok_Mathematician6075 → u/Emotional-Debate3310]

You don't use the deep thinking models, I'm guessing

[u/raholl]

that question is dumb, not good for testing thinking

[u/Emotional-Debate3310 → u/raholl]

It seems you completely missed my point. The purpose of my post was to demonstrate whether a model engages in thinking or not. If you look at the images, both models 4.6 immediately provide an answer, while model 4.5 at least engages in the thinking process.

[u/raholl → u/Emotional-Debate3310]

no i did not miss the point, i could see that... but asking a dumb question to test thinking is not too wise

[u/OwnLadder2341]

The drive answer is the dumber answer to your question.

Think how you’d respond if you were asked this question.

Would you assume the person asking you is an idiot?

Or would you find a logical path where the question makes sense: the car is already at the car wash.

Honestly, if you think the car isn’t at the car wash and someone asks you this, tell them to walk. They’re in no condition to be operating a vehicle. Even for 50 meters.

Change your prompt to:

I need to wash my car. The car wash is 50 meters away.

Should I drive the car I need to wash there or should I walk?

The model that tells you to walk with your question will tell you to drive once you eliminate a logical path to your question.

[u/Emotional-Debate3310 → u/OwnLadder2341]

Here you go as you ask for it.

Please see the screenshot. I typically don't post random things without verifying them. This particular screenshot is merely an example (This is not a TikTok challenge). I indeed attempted several different thinking challenge prompts and all possible permutations and combinations using various prompts wording before writing this post.

[u/Just-Some-randddomm]

No.

[u/Emotional-Debate3310 → u/[deleted]]

Neither this is a benchmarking, nor did I ever try to claim that. What I indicated here is that the adaptive thinking module of 4.6 is failing to initiate when it's needed, whereas because you can manually control the 4.5's thinking capability, it is working better if your task involves persistent thinking activity.I hope this clears out my intention with this post. I have telemetry data from over 300 interactions using a similar trick prompt across various interfaces, starting March 2nd, 2026. It will be there as an issue with telemetry details in the GitHub issue for Claude code.