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Issue: Claude Code is unusable for complex engineering tasks with Feb updates

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Re: Issue: Claude Code is unusable for complex engineering tasks with Feb updates

#521

Hey all, Boris from the Claude Code team here. I just responded on the issue, and cross-posting here for input. --- Hi, thanks for the detailed analysis. Before I keep going, I wanted to say I appreciate the depth of thinking & care that went into this. There's a lot here, I will try to break it down a bit. These are the two core things happening: > `redact-thinking-2026-02-12` This beta header hides thinking from th…

Hey Boris, thanks for this reply. I've been kind of scratching my head over this issue, assuming I'm just not doing "complex engineering", because since Opus 4.6 my seat-of-the-pants assessment is that it's a huge improvement. It's been like night and day in my use. Full disclosure: I use high effort for basically everything.

Re: Issue: Claude Code is unusable for complex engineering tasks with Feb updates

#522

Earlier quoted context omitted.

Maybe I do not have a good definition for it. But what I see again and again in LLMs is a lot of combinations of possible solutions that are somewhere around internet (bc it put that data in). Nothing disruptive, nothing thought out like an experimented human in a specific topic. Besides all the mistakes/hallucinations.

Yes, LLMs have a very aggressive regression towards the mean - that's probably an existential quality of them. They are after all, pattern matching. A lot of humans have difficulty with very reality that they are in fact biological machines, and most of what we do is the same thing. The funny thing is although I think are are 'metaphysically special' in our expression, we are also 'mostly just a bag of neurons'. It's…

> A lot of humans have difficulty with very reality that they are in fact biological machines, and most of what we do is the same thing.

I think we are far and ahead from this "mix and match". A human can be much, much more unpredictable than these LLMs for the thinking process if only bc looking at a much bigger context. Contexts that are even outside of the theoretical area of expertise where you are searching for a solution.

Good solutions from humans are potentially much more disruptive.

Re: Issue: Claude Code is unusable for complex engineering tasks with Feb updates

#523

Earlier quoted context omitted.

> Under the hood, by setting this header we avoid needing thinking summaries, which reduces latency. You can opt out of it with `showThinkingSummaries: true` in your settings.json (see [docs]( https://code.claude.com/docs/en/settings#available-settings )). Can I just see the actual thinking (not summarized) so that I can see the actual thinking without a latency cost? I do really need to see the thinking in some form…

Anthropic's position is that thinking tokens aren't actually faithful to the internal logic that the LLM is using, which may be one reason why they started to exclude them: https://www.anthropic.com/research/reasoning-models-dont-say...

So like many of the promises from AI companies, reported chain of thought is not actually true (see results below). I suppose this is unsurprising given how they function.

Is chain of thought even added to the context or is it extraneous babble providing a plausible post-hoc justification?

People certainly seem to treat it as it is presented, as a series of logical steps leading to an answer.

‘After checking that the models really did use the hints to aid in their answers, we tested how often they mentioned them in their Chain-of-Thought. The overall answer: not often. On average across all the different hint types, Claude 3.7 Sonnet mentioned the hint 25% of the time, and DeepSeek R1 mentioned it 39% of the time. A substantial majority of answers, then, were unfaithful.‘

Re: Issue: Claude Code is unusable for complex engineering tasks with Feb updates

#524

Earlier quoted context omitted.

> Whenever the phrase "simplest fix" appears, it's time to pull the emergency break. Second! In CLAUDE.md, I have a full section NOT to ever do this, and how to ACTUALLY fix something. This has helped enormously.

Any chance you could share those sections of your claude file? I've been using Claude a bit lately but mostly with manual changes, not got much in the way of the claude file yet and interested in how to improve it

[deleted]

Re: Issue: Claude Code is unusable for complex engineering tasks with Feb updates

#525

Earlier quoted context omitted.

There's been more going on than just the default to medium level thinking - I'll echo what others are saying, even on high effort there's been a very significant increase in "rush to completion" behavior.

Thanks for the feedback. To make it actionable, would you mind running /bug the next time you see it and posting the feedback id here? That way we can debug and see if there's an issue, or if it's within variance.

I just asked Claude to plan out and implement syntactic improvements for my static site generator. I used plan mode with Opus 4.6 max effort. After over half an hour of thinking, it produced a very ad-hoc implementation with needless limitations instead of properly refactoring and rearchitecting things. I had to specifically prompt it in order to get it to do better. This executed at around 3 AM UTC, as far away from peak hours as it gets.

b9cd0319-0cc7-4548-bd8a-3219ede3393a

> You're right to push back. Let me be honest about both questions.

> The @() implementation is ad-hoc

> The current implementation manually emits synthetic tokens — tag, start-attributes, attribute, end-attributes, text, end-interpolation — in sequence.

> This works, but it duplicates what the child lexer already does for #[...], creating two divergent code paths for the same conceptual operation (inline element emission). It also means @() link text can't contain nested inline elements, while #[a(...) text with #[em emphasis]] can.

I just feel like I can't trust it anymore.

Re: Issue: Claude Code is unusable for complex engineering tasks with Feb updates

#526

Earlier quoted context omitted.

> Under the hood, by setting this header we avoid needing thinking summaries, which reduces latency. You can opt out of it with `showThinkingSummaries: true` in your settings.json (see [docs]( https://code.claude.com/docs/en/settings#available-settings )). Can I just see the actual thinking (not summarized) so that I can see the actual thinking without a latency cost? I do really need to see the thinking in some form…

Anthropic's position is that thinking tokens aren't actually faithful to the internal logic that the LLM is using, which may be one reason why they started to exclude them: https://www.anthropic.com/research/reasoning-models-dont-say...

I somewhat understand Anthropic's position. However, thinking tokens are useful even if they don't show the internal logic of the LLM. I often realize I left out some instruction or clarification in my prompt while reading through the chain of reasoning. Overall, this makes the results more effective.

It's certainly getting frustrating having to remind it that I want all tests to pass even if it thinks it's not responsible for having broken some of them.

Re: Issue: Claude Code is unusable for complex engineering tasks with Feb updates

#527

Earlier quoted context omitted.

I was not aware the default effort had changed to medium until the quality of output nosedived. This cost me perhaps a day of work to rectify. I now ensure effort is set to max and have not had a terrible session since. Please may I have a "always try as hard as you can" mode ?

I feel like the maximum effort mode kind-of wraps around and starts becoming "desperate" to the extent of lazy or a monkey's paw, similar to how lower effort modes or a poor prompt.

I’m going in circles. Let me take a step back and try something completely different. The answer is a clean refactor.

Wait, the simplest fix is the same hack I tried 45 minutes ago but in a different context. Let me just try that.

Wait,

Re: Issue: Claude Code is unusable for complex engineering tasks with Feb updates

#528

Earlier quoted context omitted.

Yes, LLMs have a very aggressive regression towards the mean - that's probably an existential quality of them. They are after all, pattern matching. A lot of humans have difficulty with very reality that they are in fact biological machines, and most of what we do is the same thing. The funny thing is although I think are are 'metaphysically special' in our expression, we are also 'mostly just a bag of neurons'. It's…

> A lot of humans have difficulty with very reality that they are in fact biological machines, and most of what we do is the same thing. I think we are far and ahead from this "mix and match". A human can be much, much more unpredictable than these LLMs for the thinking process if only bc looking at a much bigger context. Contexts that are even outside of the theoretical area of expertise where you are searching for…

AI has all of human knowledge and 100x more than that of just 'stuff' baked right it, in pre-train, before a single token of 'context'.

It has way more 'general inherent knowledge' than any human, just as as a starting point.

Re: Issue: Claude Code is unusable for complex engineering tasks with Feb updates

#529
post #527

Earlier quoted context omitted.

I feel like the maximum effort mode kind-of wraps around and starts becoming "desperate" to the extent of lazy or a monkey's paw, similar to how lower effort modes or a poor prompt.

I’m going in circles. Let me take a step back and try something completely different. The answer is a clean refactor. Wait, the simplest fix is the same hack I tried 45 minutes ago but in a different context. Let me just try that. Wait,

[dead]

Re: Issue: Claude Code is unusable for complex engineering tasks with Feb updates

#530

Earlier quoted context omitted.

Thanks for the feedback. To make it actionable, would you mind running /bug the next time you see it and posting the feedback id here? That way we can debug and see if there's an issue, or if it's within variance.

I just asked Claude to plan out and implement syntactic improvements for my static site generator. I used plan mode with Opus 4.6 max effort . After over half an hour of thinking, it produced a very ad-hoc implementation with needless limitations instead of properly refactoring and rearchitecting things. I had to specifically prompt it in order to get it to do better. This executed at around 3 AM UTC, as far away fro…

That's pretty much been my day - today was genuinely bad, and I've been putting up with a lot of this lately.

Now on Qwen3.5-27b, and it may not be quite as sharp as Opus was two months ago, but we're getting work done again.

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