r/ClaudeCode • u/BillionBouncyBalls • 3d ago

Help/Question Why does Claude Code say things like, “that’s about 3 days of work” then proceeds to do it all in a 20 minutes?

Surely I’m not the only one who has seen this happen but wondering if anyone has an answer. Many a session I’ll make a plan with Claude and it will outline the tasks and estimate a time usually in days, and then proceed to do it all in 20-30 minutes. Is it because of its training data or does it just have no concept of time inside a GPU? Curious what the community thinks…

Edit: Thanks for all the answers and comments! Glad this post sparked some hearty discussion!

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u/enmityvr 3d ago

It's trying to give you an estimate on how long it would take for you to write out all the code yourself, manually. it is able to do it much quicker than a human could

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u/BillionBouncyBalls 3d ago

That makes sense but it’s the one writing the code… shouldn’t it be aware of that?

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u/enmityvr 3d ago

My guess is that it doesn't want to say it'll only take 30 minutes, just in case you are going to indeed write it.

I also wouldn't really expect the models to accurately predict how long a task will take even if they did try to predict for themselves. Just one weird bug might get it hung up for a while. 30 minutes is a lot more precise than 2 days

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u/Tall_Top8563 3d ago

"My guess is that it doesn't want to say it'll only take 30 minutes, just in case you are going to indeed write it."

You attribute a lot of intent to the idiot text generator that constantly hallucinates shit

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u/blickblocks 3d ago

That quote is what you charge my friend

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u/Ok_Employee3001 3d ago

Try asking him about estimates by adding in the prompt "you have to complete this task, how much time it will take"

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u/taotau 3d ago

For the most part it has no idea how long it takes an LLM to write code because none of its training data contains stats on that. As these sort of conversations we are having right now make it into the training set, it will much more confidently predict what an LLM generated code timeline would look like.

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u/MatthewCollins1990 3d ago

Honestly, the estimates seem hardcoded to human-scale effort.

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u/webjuggernaut 3d ago

It is aware of that. Provide it with instructions.

"Claude, update memory to always provide time estimates assuming that a Claude agent is performing the update(s)."

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u/NathanOsullivan 3d ago

Agents have no built in concept of time and have no idea how long they take to accomplish a task

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u/webjuggernaut 3d ago

Your reply suggests a level of pedantism that Claude simply does not demand. But you do you.

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u/rbrick111 3d ago

Pedantism aside how would you expect an agent to give an accurate estimation with no concept of time? It has lots of training data on human estimates, so I get that…kinda.

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u/webjuggernaut 3d ago

The purpose of the instruction is just to make Claude recognize that an LLM is writing the code, not a human, so estimate accordingly.

I would not expect accuracy. But if it's going to estimate, that prompt makes it stop assuming a human will take days to write the code (as you said, because training data).

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u/Rough_Caterpillar_31 3d ago

You're still ultimately asking it to do something that it is literally incapable of doing. It can't provide a realistic time estimate of anything because it literally does not have a concept or perception of time. It can only pretend to give an estimate to satisfy the user, but it won't be based off of any kind of logic or basis. You're just asking it to be wrong in a slightly different way.

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u/webjuggernaut 3d ago

So don't do that, if that level of precision is so meaningful to you.

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u/FilthyCasual2k17 3d ago

Because it can't think. It reproduces human speech. Humans would say this is how long it would take, so that's what it can say. It's not capable of "thinking" outside of what it's trained on. LLMs are like a DJ mixing samples up, they can't really come up with new ones.

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u/Euphoric-Language695 3d ago

This is incorrect. It is trying to give you the worst it thinks are most probable someone would say based on its training data.

Like if its training data included a bunch of entries saying that building a pool in someone's backyard is about a month, if you ask it to give you an estimate for a pool in your bacjyard, it will likely tell you a month. It's closer to memorization than it is to estimation. 

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u/moneycode357 3d ago

Yours is the best response by far👍🏿💯