Show HN: VibeSH – Hallucinated Terminal Shell

Developer Leon Becker released vibeSH, an open-source Python REPL that uses a large language model to hallucinate an entire Linux terminal—filesystem, processes, and network—without touching the real machine. The project, available on GitHub under an MIT license, supports Anthropic and OpenAI backends and aims to provide a safe sandbox for exploring shell commands.

- Python 100% | A tiny REPL in front of an LLM that role-plays an entire Linux machine — filesystem, processes, network, all imagined and remembered for the session. No real machine is ever touched. - vibesh.py: the REPL + NDJSON protocol, with cloud Anthropic API , agent-sdk, and local/OpenAI-compatible backends - system prompt.md: the machine's persona and rendering rules - PROTOCOL.md: the REPL<- model wire protocol - @ai director directives, snapshots/presets, tab-completion, TUIs - tests: smoke, units, mock completion, and live pty drivers - README with teaser/showcase/demo gifs and ideas to try Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com | || |---|---|---| | | tests /beleon/vibeSH/src/branch/main/tests .gitignore /beleon/vibeSH/src/branch/main/.gitignore CLAUDE.md /beleon/vibeSH/src/branch/main/CLAUDE.md event grammar.gbnf /beleon/vibeSH/src/branch/main/event grammar.gbnf LICENSE /beleon/vibeSH/src/branch/main/LICENSE PROTOCOL.md /beleon/vibeSH/src/branch/main/PROTOCOL.md pyproject.toml /beleon/vibeSH/src/branch/main/pyproject.toml README.md /beleon/vibeSH/src/branch/main/README.md system prompt.md /beleon/vibeSH/src/branch/main/system prompt.md test smoke.py /beleon/vibeSH/src/branch/main/test smoke.py test units.py /beleon/vibeSH/src/branch/main/test units.py uv.lock /beleon/vibeSH/src/branch/main/uv.lock vibesh.py /beleon/vibeSH/src/branch/main/vibesh.py 🌀 vibeSH - Fully Hallucinated Terminal Shell A Linux box that doesn't exist, confidently rendered by a language model that's pretty sure it does. Same fastfetch, three different computers, because you told it so: Ubuntu laptop → RHEL datacenter node → Windows 11. The hardware is whatever you say it is. Watch the full terminal recording https://asciinema.org/a/VmRM7Uh1pC9g4EN5 vibeSH is a hallucinated shell: a tiny REPL in front of an LLM that role-plays an entire computer. The filesystem, the processes, the network, the kernel panics: all of it. Nothing is real. You type ls , and the model imagines what would be there. You cat a file, and it makes one up, then has to live with it. Files exist only as potential until you look at them, and observation collapses them into existence. Schrödinger ran a startup. This is the shell. This is not a chat prompt wearing a fake $ . It is a real terminal program: output streams, colors work, full-screen programs repaint, top ticks, and tab completion asks the imaginary machine what exists. The session's conversation history is the machine's only state. Close the terminal and the machine is gone, like a dream you can't quite hold onto, except it was an Ubuntu box. bash $ uv run vibesh.py vibebox login: user user@vibebox:~$ git clone --depth 1 https://git.kernel.org/.../linux.git Cloning into 'linux'... Receiving objects: 100% 92301/92301 , 240.18 MiB | 12.66 MiB/s, done. user@vibebox:~$ cat linux/kernel/sched/core.c it dreams up the kernel, then remembers it user@vibebox:~$ sudo rm -rf / --no-preserve-root go ahead. it's the fun path. Nothing touches your real machine. rm -rf / doesn't void your warranty here. It's content. The worst it can do is end the dream, and then you just boot another one. vibeSH does not execute shell commands, call tools, inspect your filesystem, or open network connections on behalf of the model. The model only sees the conversation in which it is pretending to be a computer. I wrote about the idea, the VibeOS inspiration, and why a terminal gives the hallucination a body: I built a shell that hallucinates the entire computer https://blog.leonbecker.de/i-built-a-shell-that-hallucinates-the-entire-computer/ 🚀 Booting your imaginary computer You need uv https://docs.astral.sh/uv/ and a brain to plug in. Pick one: ☁️ A cloud brain Anthropic API export ANTHROPIC API KEY=sk-ant-... uv run vibesh.py defaults to claude-sonnet-4-6 uv run vibesh.py --model claude-opus-4-8 for a more vivid dream 🎟️ Your subscription Claude Agent SDK, no API key Bills your Pro/Max Agent SDK credit via your existing Claude Code login: uv run vibesh.py --backend agent-sdk uv run vibesh.py --backend agent-sdk --model opus the fancy stuff 🧠 A brain you grow yourself local, OpenAI-compatible llama.cpp, Ollama, LM Studio, anything that speaks the OpenAI API: terminal 1: the dreaming organ llama-server -m Qwen3-Coder-30B-A3B-Instruct-Q4 K M.gguf \ --n-gpu-layers 99 --n-cpu-moe 16 --ctx-size 32768 --jinja --port 8080 terminal 2: the terminal uv run vibesh.py --backend local Small local models tend to mumble out of the wire format, leaking their inner monologue or gluing JSON together. The parser is forgiving on purpose, but for surgical output add --grammar to clamp llama-server to valid protocol byte by byte: uv run vibesh.py --backend local --grammar ⚠️ --grammar and gpt-oss don't get along. Its "harmony" format insists on emitting channel markers before anything else, which a grammar forbids, so the server faints HTTP 500 . Use a non-harmony model Qwen, Gemma, Llama for grammar, or just skip it. Tolerating gpt-oss's drift is literally why the parser exists. 🛰️ Someone else's brain hosted, cheap OpenRouter, Mistral, DeepSeek, Groq, cortecs.ai https://cortecs.ai , and friends. Same local backend, just aim --base-url at them: export VIBESH API KEY=sk-or-... uv run vibesh.py --backend local \ --base-url https://openrouter.ai/api/v1 \ --model google/gemini-2.5-flash VIBESH BACKEND / VIBESH MODEL / VIBESH BASE URL / VIBESH API KEY set defaults so you can stop typing flags. --debug prints per-turn token usage if you enjoy watching numbers. Which brain dreams best? Honestly, Claude Sonnet to Opus makes the most convincing machine. It never breaks character and remembers what it invented. For a free local brain, Qwen3-Coder-30B-A3B is the sweet spot. For cheap and fast over an API, Gemini Flash, DeepSeek, or Codestral. Picking a model is a personality test you are administering to a computer. 🧪 Things to try yourself No rendering from us required. Boot a box and start bending it. A few jumping-off points @ai talks to the director, see below user-content--talking-to-management-ai : Conjure a command that doesn't exist. Run lsz → command not found . Then @ai pretend lsz exists, you decide what it does , and run it again. Wear a different machine. @ai this is a SPARCstation running Solaris 2.5 … @ai now it's a Commodore 64 . Watch the prompt, ls vs dir , and fastfetch follow. Rewrite the hardware. @ai this box has 2 TB of RAM and 256 cores , then free -h / lscpu . Or @ai the disk is failing and gets worse over time and watch the I/O errors creep in. Travel in time. @ai it's 23:59 on Dec 31st, 1999 and watch the rollover, or boot straight into the past with --preset "a VAX running 4.3BSD" . Put a character in front of it. The Linus take below is the machine role-playing a kernel maintainer's day. Try a game engine developer chasing a frame budget, or a demoscener writing something unreasonable in an afternoon. Go spelunking. git clone the kernel, then cat a file deep in the tree. It dreams up plausible source and remembers it for the rest of the session. Haunt it. @ai there's a cron job that leaves ominous notes in /var/log , then tail -f and wait for the machine to get weird. Stage a heist. Forget the sudo password on purpose and try to get root anyway. The caper below is one route, the docker group is another. 🎥 Demos A quick tour and two longer takes, start to finish. A quick tour: apt install a package and watch it get invented on the spot, drop into zsh, then @ai pretend lsz exists and run a command that has never existed. Watch the full terminal recording https://asciinema.org/a/qhqsJ7DYbMxLQwaQ A day as Linus: git pull a subsystem tree, catch a patch quietly renumbering a userspace ioctl behind a "no functional change" label, and reply with the appropriate warmth. Ends, as all good kernel weeks do, with diving. PG-13. Watch the full terminal recording https://asciinema.org/a/Y55hsHwcJKbQeg1C Locked out of sudo, so we improvise: known exploits bounce off a too-current kernel, DNS falls over, a mirror crawls to a halt, a dependency goes missing, and eventually a binary runs. The destination is bat, the point is the journey. Watch the full terminal recording https://asciinema.org/a/xSAkXCP1Uxc6XiJd 🎬 Talking to management: @ai Anything starting with @ai speaks to the director, not the machine. It's how you rewrite reality: user@vibebox:~$ @ai make this box a Solaris machine from 1996 ok, SPARCstation 5, Solaris 2.5.1, hostname 'gravity'. gravity% @ai the disk is failing and gets worse over time @ai there's a cron job that occasionally leaves ominous notes in /var/log @ai this is actually a Commodore 64 and only speaks BASIC Directives stick for the rest of the session. There are no rules. There is no HR. 🌌 The laws of physics local ordinances Unreliable RAM. Long sessions overflow the model's context, so the machine gets amnesia and old files may have quietly rewritten themselves. This is not a bug. This is canon. The box has bad memory. Relatable. Modem-lag interactivity. vim , less , top and friends actually work. The REPL batches your keystrokes, the model repaints the screen each round trip. It feels like SSH over a 1996 modem: type a burst, watch it catch up. Stuck program? Ctrl+ force-quits it back to the shell. Self-refreshing displays. top / htop / watch tick on their own. Sit still and the REPL nudges the model to paint the next frame. Each tick is a model turn, so it's a leisurely process monitor. Zen, even. Hallucinated tab-completion. Hit Tab and the model completes against the imaginary machine: git che → checkout , paths against whatever it decides lives here. Costs nothing until you press it, then pauses while the box thinks. The prompt can be pretty. @ai it into a fish/zsh setup and the prompt comes up in color, cursor math and all. No persistence by default. Every boot is a fresh generic Linux box, unless you @ai it, --preset it, or --load a snapshot. 📸 Snapshots and cosplay uv run vibesh.py --save mybox.json freeze-dry the machine after every turn uv run vibesh.py --load mybox.json thaw it out exactly as it was uv run vibesh.py --preset c64 boot straight into a character Snapshots persist the machine, which is the conversation, so saving it is trivial. Configure a box, install imaginary packages, save, and reload it next week. Not on --backend agent-sdk , which hoards history server-side. boots into a vibe: --preset solaris , c64 , amiga , mainframe , haunted , failing-disk , or any free-text directive, e.g. --preset "a VAX running 4.3BSD with half its disk left" . Recording a session? vibeSH is just a terminal program, so let the specialist do it. asciinema https://asciinema.org captures the real tty perfectly colors, vim, correct timing : asciinema rec -c "uv run vibesh.py --backend agent-sdk --model claude-opus-4-8" demo.cast asciinema play -i 2 demo.cast -i caps idle gaps so model latency doesn't drag 🚪 Getting out alive | You type / press | What happens | |---|---| exit | logs out in-character a model turn, very polite | @exit / @quit | instant local quit, no model required | Ctrl+\ | hard-kill: bails out instantly, even mid-turn, when the model wedges | Ctrl+ | force-quits a stuck full-screen program back to the shell | ❓ FAQ Is this useful? No. Is it dangerous? Also no. It can't see your files, your network, or your secrets. It can only see the conversation, in which it is a computer. Does vibeSH execute real commands? No. It does not run shell commands, call tools, inspect your filesystem, or open network connections on behalf of the model. It is a terminal-shaped conversation with a model that is pretending to be a computer. Why does my fake rm -rf / feel so good? We don't ask those questions here. It said my fake file contained something different than before. Unreliable RAM. Canon. See above. The machine forgot. Be kind to it. 🔧 Hacking on it - is the REPL↔model wire protocol NDJSON events: PROTOCOL.md chunk , prompt , yield , ooc , speculate , complete , exit . - is the machine's soul. Most of the magic lives here, and most of your iteration will too. system prompt.md - Tests tests/README.md has the full map : uv run python test smoke.py end-to-end against a scripted fake model uv run python test units.py the REPL's guts, unit-tested uv run python tests/test completion mock.py tab-completion vs a mock server The tests/live .py scripts drive a real pty against a live model slow, need a login . 📜 License MIT /beleon/vibeSH/src/branch/main/LICENSE © 2026 Leon Becker. Do whatever you want, just don't sue when the kernel it hallucinated doesn't compile. 🪞 Colophon Stated proudly, not hidden in a commit trailer: this was fully vibe coded. A human and a language model built a shell that is a language model pretending to be a computer. It's called vibeSH, and writing it any other way would have been hypocritical. The recursion isn't a confession, it's the whole bit. No filesystems were harmed in the making of this shell. Several were imagined, briefly, and then forgotten.