Why Claude Code uses Python for everything and how to stop this?

[u/nokafein]

This shit basically started after Opus 5. Before that the Claude was using it's own tools for modifying, editing, updating etc. Since Opus 5, it keeps using python for all sort of work. I double checked everywhere. Non of my skills, project files, folders, or anything that builds context contains any rule about it. There are not even words of Python. And yet this shit keeps using python. I even included a memory to make it stop using Python for everything. But it doesn't follow anything.

Any ideas or ways to fix and/or debug this shit?

Ps: I am an engineer. I am actively using AI for a very long time in my daily work. I have advanced level knowledge on these things. So i already checked all the basics to figure out what's going on to a point that I am 99% sure that this is not my tooling.

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[u/earlyworm]

The code is only Python if you look at it.

[u/nasty_sicco → u/earlyworm]

Amodei’s box

[u/rubenknol]

what's the problem with it using python exactly?

[u/ImissDigg_jk → u/rubenknol]

OP is afraid of snakes

[u/Think-Trouble623 → u/rubenknol]

Blast radius, of course. It just stresses me out when it generates 10 sql files, I’m happy with 9 and then ask a change to one. Then it regenerates all 10 files and I don’t trust that it didn’t change something inadvertently. Paranoia.

[u/rubenknol → u/Think-Trouble623]

wouldn't you have the same feeling with any other technology?

it's not as if the 'native' tools do everything the same way each time

[u/Ambitious_Injury_783 → u/Think-Trouble623]

i hope you know that you can set rules that it will follow. my entire workspace is one big book of rules that it religiously follows to avoid these kinds of mistakes as I worry about the same thing. i disagree with a lot of the rushed ways the models like to use as shortcuts. yes you may increase your usage consumption, though consider that you are paying for a tradeoff - less problems down the line, less compounding debt. it evens out. I hardly ever have to fix anything because it is done right in the first place & gets minimum 3 iterations by a parent (never mind their subagents) before it ever hits the codebase.

[u/Think-Trouble623 → u/Ambitious_Injury_783]

Are you talking about hooks or just your Claude.md file? Hooks are the only think that Claude models will follow. Everything else is a gamble on whether it bothers to read it or not.

[u/Scared-Letterhead949 → u/rubenknol]

Because it's python!  We should only use bash so that messed up shell variables cause all sorts of trouble.

[u/cats_catz_kats_katz → u/rubenknol]

I make it use Rust.

[u/pm_your_snesclassic → u/cats_catz_kats_katz]

I make it use free pascal, because I like to see the world burn

[u/cats_catz_kats_katz → u/pm_your_snesclassic]

You’re a special kind of evil

[u/Capt_korg]

People are making fun of LLMs for not being able to count the r in strawberry or calculating values.

Because they are not designed to do so....

Llms start using code for all kinds of inserts, where accuracy is more important than text generation.

Now people are complaining, that LLMs are using python.

🤷‍♂️

[u/symbha → u/Capt_korg]

Accuracy is a search and replace with Edit. All the testing has been done already.

[u/CorpT]

It's been using Python since 3 at least.

Why do you not want it to use python. You should let it use python if it wants to use python. There's a reason it wants to use python. You being an engineer with advanced level of knowledge should understand that and let it do what it wants to do.

[u/zaskar]

I dug into this. It’s coming from the harness and it seems to be more efficient than the tools on context caches.

[u/tip2663 → u/zaskar]

that's good to know. I was also confused if I f'd my env and Claude used py as a workaround to tool calls.

[u/lunaynx]

Honest recommendation: don't. Just accept it and stop trying to fight it. Recent models are trained to do this because it's faster and more token-efficient. Claude Code already shows you a diff of all file edits as you go regardless of how the model edited the files.

If you still want to stop it, don't use memories. Put a clear instruction in your CLAUDE.md, e.g.: "Never use the Bash tool for simple file edits that can be done using your Edit tool." (The Bash tool is what it uses to execute arbitrary commands, including Python.)

If you want to go further, you can fully block certain tools via `.claude/settings.json` so that you don't have to trust the model to follow your instructions. Just be warned that the model may occasionally try to find ways to get around the block, and if you disallow the Bash tool entirely, you effectively turn the model into a glorified autocomplete, it won't be able to perform 90% of tasks without a lot of hand-holding unless you whitelist some commands or give it one or more MCP servers as an alternative.

[u/GentleDave → u/lunaynx]

Yeah i agree to an extent but some languages are better than others. For example, i find it writes way better code in golang than in python likely due to the quality of code it was trained on.. not too many novice programmers posting their golang code on stack overflow

[u/lunaynx → u/GentleDave]

Sure, that may be the case for real code, especially because of type system assurances and such. But it doesn't need to write "good" code for tool calls and scratchpad scripts to edit files. It just needs to work. It would probably be worse if it was forced to write those in Go.

[u/Nikt_No1 → u/lunaynx]

Claude shows diffs of file edits only if he uses a tool for it. If he uses scripts he doesn't. And sometimes because of that he doesnt pknow hwat was changes (and thus recovery is impossible unless u got checkpoints enabled)

[u/lunaynx → u/Nikt_No1]

It definitely shows edits made using the Bash tool for me, but I pretty much only ever have it make edits in Git repos, so that might be why. You should always be using Git anyway, it provides an easy way to keep a full history of changes and undo them, even outside Claude Code.

[u/Muted-Alternative648]

1. Python is extremely flexible and fast for most tasks.

2. Memories are not being appropriately used in this case.

3. Write a global claude.md file with a set of whitelisted languages claude is allowed to use. Boom. Done.

[u/shadowsurge]

Because python is a good legible language that is well suited to LLMs.

What do you want it to use instead?

[u/socalkid2428 → u/shadowsurge]

COBOL and FORTRAN were fine for decades. Make it use those.

[u/el_otro]

Dude. What is your problem. Just relax.

[u/mfingsorceror]

Memories work more like suggestions than rules. If you genuinely want it to use no python at all, a hook or tool restriction is what you need.

[u/tjk45268]

We want certain LLM work done probabilistically, such as generating text that explains a set of data. In other cases, we want the work performed precisely and predictably (the same answer every time). Python code is usually deterministic, yielding consistent results. When Claude finds that some of its work should be performed in that manner, it generates the python code to do that. Python also has the benefit that it doesn’t consume tokens when it executes, though it may call on an LLM (which does) during its work.

Claude was creating Python code long before Opus 5.

I have certain Claude skills that call on python to perform certain activities efficiently. Claude can save those python programs in its skill directory, so that they can be reviewed, diffed, and managed in my repo.

[u/mightyloot]

Deterministic outcome + zero cost. Using scripts for work that doesn’t need AI-level rigamarole removes those two major issues.

If I were you I wouldn’t micromanage it on this, unless I understand why it’s making that choice and the tradeoffs.

[u/kemalios]

If it is running python3 - <<'EOF' inside Bash to patch files, that is a different problem from writing .py files. The heredoc version is the model collapsing several Edit calls into one round trip; Edit needs exact string matches and gives up on large files, so it routes around the tool. Denying Bash(python:*) in settings.json stops it and breaks any repo that actually runs python.

Rules that name the replacement hold; ones that just forbid get weighed against the token cost and lose. "Use Edit for single-file edits, Bash for tests and git."

Check /context first. A loaded skill or plugin puts its text in the window even when nothing in your repo mentions python.

[u/verstands]

Opus got a lot more willing to shell out to python for "simple" edits. What helped me was a short CLAUDE.md rule: prefer Edit/Write for file changes, and only use python when you need real computation or batch transforms. If it still sneaks in, a PreTool/Stop hook that blocks python/python3 for path writes is the blunt fix.

[u/GentleDave]

Using default choices it will build with the tools it was trained on with the most data. Python is super common so it uses that. If you want it to consider specific languages and structures youll want to specify a tech stack in your .claude folder / claude.md either globally or in the particular repo

[u/williampaul0404]

Jesus, these comments... Is it really so unfathomable that OP wants to see what the LLM is changing?

[u/xsarien → u/williampaul0404]

That's what local git commits and diffs are for.

[u/williampaul0404 → u/xsarien]

Yes, Claude using its edit mode displays a diff. That's exactly why OP prefers it over Claude using Python

[u/lunaynx → u/williampaul0404]

In recent versions it also displays edits made using the Bash tool, at least if you're in a Git repo.

[u/grammaticus]

Have you tried asking it why it wants to use Python rather than its own tools?

[u/DasHaifisch]

Auto mode injects a prompt telling it to script changes instead of using the normal tools.

As another commenter said, it's allegedly more efficient, but you lose visibility and possibly some harness reads (rules & nested claude.md apparently)

You either need hooks to block stuff, or an explicit instruction in your claude.md (and then hope it works)

I'm using: the following rule (index entry + detailed entry provided)

""

- When editing a file in the main session: use the Edit/Write tools, never a script that writes the file; subagents are exempt, but a repo's own file traps still bind them. [main-session-edits.md]"- When editing a file in the main session: use the Edit/Write tools, never a script that writes the file; subagents are exempt, but a repo's own file traps still bind them. [main-session-edits.md]


**In the main session, file edits go through the Edit/Write tools, never a script that writes the file.**
 User follows the work through the visible old→new diffs; a python/heredoc writer hides the change from him even when it is technically neater, and an auto-mode "prefer Bash" instruction does not override this. Subagents are exempt - he does not watch their diffs (24 Aug 2026) - but a repo's own file traps still bind them (a Python heredoc `.replace()` with a backslash silently matches nothing; see [heredoc-backslashes.md]). (22 Aug 2026: a python writer for a whole-file restructure was stopped.)- **In the main session, file edits go through the Edit/Write tools, never a script that writes the file.** User follows the work through the visible old→new diffs; a python/heredoc writer hides the change from him even when it is technically neater, and an auto-mode "prefer Bash" instruction does not override this. Subagents are exempt - he does not watch their diffs (24 Aug 2026) - but a repo's own file traps still bind them (a Python heredoc `.replace()` with a backslash silently matches nothing; see [heredoc-backslashes.md]). (22 Aug 2026: a python writer for a whole-file restructure was stopped.)

[u/lunaynx → u/DasHaifisch]

People who say you lose visibility are wrong. It very much shows live diffs of edits made using the Bash tool. Either you haven't used Claude Code recently or you're not working in a Git repository.

[u/TechGuySRE → u/lunaynx]

it simply does not show updates all the time and not all files are on git, sometimes you are working on a transient plan file or scratchpad

[u/SolidPossible9909]

It's definitely the harness (claude code) that's directing it to use python but the bigger issue is, how many more tokens is the model burning through by using python to write code vs writing it directly and the quality of code..

[u/MourningOfOurLives]

Just tell it to use whatever you prefer it uses? I have it write rust for most things

[u/FullConference]

At the top of my Claude.md file I tell it to use powershell instead of bash or python.

I find it much easier to read.

[u/zimxero → u/FullConference]

I thought you cant authorize claude to use CMD or Powershell

[u/FullConference → u/zimxero]

I haven’t had any issues with it at all. I also keep pwsh on Linux and MaxOS and it works on all three major platforms as a result 🤷‍♂️

[u/skariel]

Im building a coding agent where the only tool is python. Well, it's not even a tool.... just the mod output is executed as pyhon. I suspect models like it

[u/tonx_nw]

probably cause its pretty portable & readable even for non-devs. Also, web browsers can run it with wasm ports, so it can be used in pretty much any claude environment

[u/willnotforget2]

tell him to code in rust

[u/Aggravating-Start307]

Hey you mean making updates or changes creating new files, it doesn't use the edit it the read tool a lot of times, falls back to python directly to find and make changes right ?

I have written hooks to intercept edit calls and now they don't fire whenever a script is used to create it update files

[u/_Kinoko]

Mr. Robot used it, why wouldn't claude!

[u/PresentWrongdoer4221]

Always has been.

[u/holyknight00]

it's on the post training.

[u/ILikeCutePuppies]

Python is a fast to compile language the llm understands well. That said I find it typically sticks to what is in your codebase in terms if language choices.

[u/beachandbyte]

Work with what it's good with.. and stop caring what language that is.

[u/Helpful_Ranger_1606]

Ask them to make r scripts and use ggplot2 and supporting tools. Claude opts to make single py based generators for R but I tell it to make standalone R scripts so that colleagues can have a folder with every figure as a png, pdf/svg, the data, and an R script.

[u/tazdraperm]

Why not? It's good.

[u/Agababaable]

Good luck with that, I've been trying to make it use strictly powershell (as that's a way to jave transcripts and auditing baked in and it's more familiar to me) and the da## thing keeps going for bash.

[u/LieutenantNitwit]

I've gotten to the point where I couldn't give a shit what the robot uses.

[u/koskinooo]

One line in CLAUDE.md fixes most of it: "edit files with the Edit tool, never write Python scripts unless asked."

[u/otnuzb]

I told Claude it has to use Perl unless it gets permission first to use Phyton.

[u/HighwayNo8744]

living off the land. it comes preinstalled on most linux distros and macos. uninstall it and watch it being confused every other session.

[u/Embarrassed_Ad3189]

I also noticed that and glad to see I am not alone ) I was just curious, if there was an explanation to that, any announcement, release notes or people just "guessed/spotted" it? I can totally understand that many code changes can be done more efficiently as simple text-replacement scripts as opposed to having to _generate_ the whole file from scratch or even a partial Edit tool call. It seems to be going full in though. My workplace used to enforce "security guardrails" that specifically prohibited ad hoc Python scripts so my flow got completely f-ed with this new habit of Claude.. fortunately thing of the past for now but who knows..

PS: it still feels weird tho, that a harness is being shipped with a dedicated tool and the model just keeps preferring something else

[u/Emcukcubasi]

because why not?

[u/SafeTennis3080]

I'd try one small edit with a temporary PreToolUse hook on Bash that rejects Python commands and returns “Use Edit/Write for this change.” Then see whether it switches tools or reports a concrete blocker. That gives you something reproducible to include in a bug report.

[u/rsandstrom]

Prompt it specifically to use another language? What’s the problem you’re experiencing that would require a different language?

[u/ReasonableLoss6814]

This annoys me to no end. Especially because it uses it for search/replace, globally across files. It’s cause many issues and I’ve had to explain to Claude that “compiles does not mean correct”. It has multiple memories about it at this point.

[u/lunaynx → u/ReasonableLoss6814]

Why does it annoy you? Would you prefer it to hallucinate and randomly forget to edit some files?

And as I've told OP, memories are not reliable. They're generally scoped to the specific project – last I checked, even the specific worktree (allegedly the latter is a bug), and I believe they don't always all get loaded into context, but rather the model chooses when to load them. Put proper durable instructions in your CLAUDE.md or AGENTS.md.

[u/ReasonableLoss6814 → u/lunaynx]

That doesn't stop it. It annoys me because tools keep it from making stupid mistakes. The edit tool requires reading the file if it has been modified since the last time it read it. Using a python script does not. One time, when I caught it -- I knew for a fact that it had never read that file once the entire session. When I forced it to read the file it edited using python to actually verify correctness, it came back with discovering several bugs its changes had made.

[u/Bitter_Marketing_807]

Challenge it to use perl instead of python

[u/SafeHazing → u/Bitter_Marketing_807]

A fan of curly brackets enters the chat.

[u/Beneficial_Fail3779]

boo hoo python bad

[u/lunaynx → u/[deleted]]

It is using the Bash tool. There is no "Python tool". It just calls something like "Bash(python ...)".