gut

Judgment calls as one line of Python, on models small enough to put inside an if.

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: small models. A 70M-parameter NLI model answers "is this spam?" in about a tenth of a second on a laptop CPU; a 0.6B language model, in under a second on a laptop GPU. Hosted models built for exactly this, like Jev, need no hardware at all. They are good enough for these questions — but each speaks its own API, and none of them hands you a decision.

gut is the primitive that does:

import gut

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

No prompt, no parsing, no threshold — and no model named in your code.

Three questions

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:

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.

Any model

The model is configuration, not code. Change it and nothing else changes:

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
gut.configure(backend=gut.JevBackend())                            # TypeSafe AI's Jev

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

gut.configure(backend=gut.Cascade(
    gut.ZeroShotBackend(),                        # free and local: settles the obvious
    gut.OpenAICompatibleBackend("gpt-4.1-nano"),  # sees only what the first could not
))

Answers are read from each model's own probabilities, never parsed from text, and decision.model names the model that gave one. Your own model can be a backend too: here is how.

Several questions, one pass

@gut.semantic
def handle(ticket):
    if gut.likely(ticket, "is a bug report"):
        ...
    elif gut.likely(ticket, "asks for a refund"):   # already answered
        ...

Every judgment about ticket goes to the model together: one request to a hosted model, one pass over the ticket for a local one.

Install

pip install gutfeel                  # any OpenAI-compatible server; FakeBackend for tests
pip install "gutfeel[local]"         # + ZeroShotBackend and TransformersBackend (PyTorch)
pip install "gutfeel[jev]"           # + JevBackend

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.

Docs

examples/ runs the same code on every backend. Coding agents: read SKILL.md.

Status and license

Pre-1.0, Apache-2.0. Every code block in these docs runs in the test suite, and every decision is in DECISIONS.md · contributing