gut

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**Judgment calls as one line of Python — built for Jev, and running on any small model.**

[Try it in your browser →](https://gutpy.dev/) The site runs gut's local model in the page: no key, no server.

Your code keeps running into questions that aren't logic: *Is this comment spam? Which team owns
this ticket? How urgent is it? Is the agent's task done?* Until now there were three answers:

- **Regex and keyword rules** — free and instant, and wrong the moment someone phrases it differently.
- **A frontier LLM** — understands anything, at seconds and cents a call, with prose to parse.
- **Train a classifier** — cheap to run, once you have the labelled data, the pipeline and the week.

There is a fourth: **a small model made for exactly these questions.** TypeSafe AI's
[Jev](https://docs.typesafe.ai) answers typed questions directly — a probability for yes, a
distribution over options, a score on a scale — with nothing to generate or parse, billed on input
only. `gut` is built around it, and makes it a line of code:

```python
import gut

gut.configure(backend=gut.JevBackend())   # or just set TYPESAFE_API_KEY

if gut.likely(comment, "is spam"):
    hide(comment)
```

No prompt, no parsing, no threshold — and no model named at the call site.

## Three questions

```python
gut.likely(ticket, "is a bug report")                      # yes / no
gut.classify(ticket, Team)                                 # which one — an Enum
gut.rate(ticket, ["can wait", "this week", "right now"])   # how much
```

## It knows when it doesn't know

A regex never hesitates, and neither does an LLM. `gut` can:

```python
match gut.likely(email, "the customer threatens to cancel", ask_human=True):
    case gut.YES:    escalate(email)
    case gut.NO:     auto_reply(email)
    case gut.UNSURE: send_to_a_person(email)
```

Say how careful to be in words — `lean="yes"`, `stakes="high"` — and `gut` works out the thresholds.

## A thousand subjects, one line

```python
spam = gut.each(comments).likely("is spam")     # one decision per comment, in order
teams = gut.each(tickets).classify(Team)
```

Jev gets concurrent requests, a local model batched passes, and nothing already cached is asked
twice. `@gut.semantic` does the same for several questions about one subject.

## Jev first, any model

Jev is the model `gut` is designed around. It is not the only one: the model is configuration, and
the same line runs unchanged on any of these.

```python
gut.configure(backend=gut.JevBackend())                            # TypeSafe AI's Jev
gut.configure(backend=gut.JevBackend.openrouter())                 # Jev, through OpenRouter
gut.configure(backend=gut.JevBackend.ollaya("winnow:e4b"))         # open decision model, Ollaya
gut.configure(backend=gut.ZeroShotBackend())                       # NLI model, on your CPU
gut.configure(backend=gut.TransformersBackend("Qwen/Qwen3-0.6B"))  # small LLM, on your machine
gut.configure(backend=gut.OpenAICompatibleBackend(                 # Ollama, vLLM, llama.cpp
    "qwen2.5:1.5b", base_url="http://localhost:11434/v1"))
gut.configure(backend=gut.OpenAICompatibleBackend("gpt-4.1-nano")) # OpenAI
```

Or several at once. `Cascade` asks the cheapest model first and passes on only what it is unsure of:

```python
gut.configure(backend=gut.Cascade(
    gut.ZeroShotBackend(),   # free and local: settles the obvious
    gut.JevBackend(),        # sees only what the first could not
))
```

Every answer is a model's own probabilities, never parsed from text, and `decision.model` names the model that gave it. Your own model can be a backend too: [here is how](https://gutpy.dev/docs/backends.html#writing-your-own).

## Install

```bash
pip install "gutfeel[jev]"           # + JevBackend: TypeSafe, OpenRouter or Ollaya
pip install "gutfeel[local]"         # + ZeroShotBackend and TransformersBackend (PyTorch)
pip install gutfeel                  # core: any OpenAI-compatible server; FakeBackend for tests
pip install gutfeel-mcp             # + the MCP server, gutfeel-mcp
```

The package on PyPI is `gutfeel` (`gut` was taken); the import is plain `import gut`. No model at hand? `gut.FakeBackend(answers={"is spam": 0.97})` answers from fixtures, for tests.

## From a shell, and for agents

The big model thinks; the small one decides, fast. An agent with `gut` judges a thousand files,
commits or search results in one command instead of reading each one itself:

```bash
git ls-files | gut filter "retries failed requests" --read-files --max-cost 0.50
claude mcp add gut --env TYPESAFE_API_KEY=your-key -- uvx gutfeel-mcp   # MCP Registry: io.github.Kungie/gut
npx skills add Kungie/gut --skill gut     # teaches a coding agent when to reach for it
```

## Docs

**[The documentation](https://gutpy.dev/docs/)**, one page per idea: [Getting started](https://gutpy.dev/docs/getting-started.html) · [Backends](https://gutpy.dev/docs/backends.html) · [Knowing when it doesn't know](https://gutpy.dev/docs/knowing-when-it-doesnt-know.html) · [Asking everything at once](https://gutpy.dev/docs/batching.html) · [Async](https://gutpy.dev/docs/async.html) · [Exact costs](https://gutpy.dev/docs/exact-costs.html) · [Caching and observability](https://gutpy.dev/docs/caching-and-observability.html) · [Command line](https://gutpy.dev/docs/cli.html) · [MCP server](https://gutpy.dev/docs/mcp.html) · [Honest limitations](https://gutpy.dev/docs/limitations.html). [`examples/`](https://github.com/Kungie/gut/tree/main/examples/) runs the same code on every backend.

## Status and license

Pre-1.0, Apache-2.0. Every code block in these docs runs in the test suite ·
[contributing](https://github.com/Kungie/gut/blob/main/CONTRIBUTING.md)