Skip to content(if available)orjump to list(if available)

Large integer precision error in Bash command output rendering

Large integer precision error in Bash command output rendering

24 comments

·November 13, 2025
Visit

CGamesPlay

Claude Code is simultaneously the most useful and lowest quality app I use. It's filled with little errors and annoyances but succeeds despite them. Not to mention the official documentation is entirely vibe-copywritten and any quality control is cursory at best.

It forcibly installs itself to ~/.local/bin. Do you already have a file at that location? Not anymore. When typing into the prompt, EACH KEYSTROKE results in the ENTIRE conversation scrollback being cleared and replayed, meaning 1 byte of new data results in kilobytes of data transferred when using Claude over SSH. The tab completion for @-mentioning is so bad it's worthless, and also async, so not even deterministic. You cannot disable their request for feedback. Apparently it lies in tool output.

It truly is a testament to the dangers of vibe coding, proudly displayed for everyone to take an example from.

jimbo808

I use it daily for boilerplate and CRUD stuff, and have been since it came out. I honestly haven't experienced any bugs at all with it other than Anthropic server outages, etc. As far as agentic coding tools go, nothing else is close.

That being said, it's still an LLM, and LLMs are more of a liability than an asset to me. I was an early adopter and still use them heavily, but I don't attempt to use them to do important work.

DecoPerson

Ha, interesting. Using Claude Code in Zed, I never encountered any of these defects.

I just open a Claude Code Thread, tell it what I want, bypass permissions (my remote is a container), and let it work. And it works wonderfully!

I guess the “integrated” part of IDE is pretty important.

ec109685

Are you sure about the one char thing? I’d expect a huge flash if that was the case.

CGamesPlay

No, I'm not sure about the precise mechanics of it, but I noticed it because of the huge flash when using it over a somewhat laggy SSH connection. It doesn't happy in all contexts. I've definitely seen it when typing into the new-ish Claude "ask questions about the plan" flow, and I've also noticed that it redraws the entire conversation history when each new line of output is presented in a long-running tool call.

fulafel

Smells like floating point. Python prompt:

  >>> int(float('348555896224571969'))
  348555896224571968
It just exceeds the mantissa bits of doubles:

  >>> math.log2(34855589622457196)
  54.952239550875795
JavaScript (in)famously stores all numbers as floating point resulting in silent errors also with user perceived integers, so this might be an indication that Claude Code number handling uses JS native numbers for this.

ec109685

They wrap bash with python.

fulafel

I still suspect JS. It's much harder to shoot yourself in the foot with Python. Even if you use JSON:

  >>> json.loads('{"nr": 348555896224571969}')
  {'nr': 348555896224571969}
  >>> type(_['nr'])
  <class 'int'>

amorriscode

We merged a fix for this that'll go out in the ~next release.

Also, for clarification, this bug was only impacting the display of numbers in the TUI, not what the model sees. The model sees raw results from bash.

kazinator

Note that the number is 18 digits long.

If there is a conversion to IEEE 64 bit double involved, that type is only guaranteed to record 15 decimal digits of precision, so this number cannot be represented with enough precision to recover all of its original digits.

In C implementations, this value is represented as DBL_DIG, which is typically 15 on systems with IEEE floating point.

(There is also DBL_DECIMAL_DIG which is typically 17; that's the opposite direction: how many decimal digits we need to print a double such that the exact same double can be recovered by parsing the value. DBL_DIG existed in C90, but DBL_DECIMAL_DIG didn't appear until, it looks like, C11.)

timenotwasted

Claude Code v2.0.37 Haiku 4.5 · Claude Pro

> run cmd echo '348555896224571969'

I'll run that echo command for you.

Bash(echo '348555896224571969') ⎿ 348555896224571970

The command output is: 348555896224571969

--

If I do it this way it gets the off by 1 and then fixes it when providing me the output, very interesting.

cyral

Typing "348555896224571969" into your browser's dev console will also return 348555896224571970

alyxya

I don't think this is a bug specifically with Claude Code, rather it's due to Claude Code having javascript in the backend. The interesting thing to me is that the numeric string was interpreted as an integer.

rrwright

Why did Hacker News rename the title of this post? It was originally: "Claude Code Introduces Off-by-One Errors"

Original: https://pasteboard.co/xTjaRmnkhRRo.png

Unilaterally Edited: https://pasteboard.co/rDPINchmufIF.png

dragonwriter

Probably for a couple reasons:

First, HN prefers the source title unless that title is misleaing clickbait.

Second, the problem is not consistently off-by-one errors, as there is a manifestation shown in the bug of an off-by-much-less-than-one error. The problem looks like a "for some reason it seems to be roundtripping numbers in text through a numeric representation which has about [perhaps exactly] the same precisions issues as float64" issue.

sevg

Looks like mods changed the title to the title of the GitHub Issue. This from HN guidelines is probably why:

> Otherwise please use the original title, unless it is misleading or linkbait; don't editorialize.

rrwright

Good catch on the guidelines. But that github issue title obviously misses the point. The whole point is that it's a silent error in Claude Code.

sevg

A matter of opinion, but I actually don’t think the current headline is too bad. When I saw the headline and “github.com/anthropic” next to it, my initial assumption was that it must be a problem introduced by Claude Code rather than a bug in bash or something.

That said, I don’t think your edited headline was bad either, but perhaps there wasn’t enough reason not to use the original (which is a default I personally appreciate on HN).

Insanity

I forgot which blogpost mentioned it, but to paraphrase it states that managers won’t understand why you can’t just fix a bug like this in a few minutes like you would in traditional software.

This might be one of those cases, where the problem arises from the training set somehow.

alyxya

This seems to be a software bug and not something about model behavior, though the model is in some sense doing the wrong thing by internally evaluating what the echo command should output rather than saying what the output actually is.

Edit: Based on the above comment showing javascript numerics behavior changing, it's more like some unusual interaction with the numeric string in the bash command being interpreted as an integer and running into precision issues.

amorriscode

Merged a PR after seeing this thread so, thankfully, this was one of those bugs that you can just fix in minutes. ;)

ethmarks

Is there any significance to the number 348555896224571969? How was this bug discovered and what was the discoverer doing?

rrwright

Try it yourself: `echo '348555896224571969'`

CGamesPlay

Looks like it has to be the full tool output to be coerced:

    > Can you run this through bash: echo '348555896224571969 plus 2 is 348555896224571971'
    
     Bash(echo '348555896224571969 plus 2 is 348555896224571971')
      ⎿  348555896224571969 plus 2 is 348555896224571971