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Slomo is a zero-config flight recorder for Python applications. Drop two lines into your app and Slomo silently captures every function call, unhandled exception, SQL query, HTTP request, and log record to a local append-only log — then gives you a terminal UI to replay and diagnose crashes without touching a server, creating an account, or changing how you work. Think of it as a black box for your Python process: when something goes wrong, you already have everything you need to understand exactly what happened and why.

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Explore the docs

Quickstart

Install Slomo, add two lines to your app, and explore your first crash recording in under five minutes.

Installation

System requirements, pip/uv/pipx install commands, and optional integrations for requests, httpx, and SQLAlchemy.

Core Concepts

Learn how Slomo uses PEP 669 / sys.monitoring to instrument your code with near-zero overhead.

CLI Reference

Full reference for slomo issues, slomo doctor, slomo replay, slomo init, and more.

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How it works

1

Install the package

Add Slomo to your project with a single pip command. No Docker, no external server, no account required.
2

Enable recording in your app

Call slomo.enable() at the top of your entry point. That’s it — Slomo starts recording immediately and creates a .slomo/ directory in your project folder the first time your app runs.
3

Replay and diagnose crashes from your terminal

Use the built-in CLI to browse crashes, get a root-cause summary, or step through a full interactive replay of any session.

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Why Slomo?

Fully local — no account, no telemetry

Every recording lives under .slomo/ in your project directory. Nothing leaves your machine.

Near-zero overhead

enable() completes in under 5 ms. Instrumentation is powered by sys.monitoring (PEP 669), the low-overhead monitoring API introduced in Python 3.12.

Automatic — records everything

Function calls, exceptions with local variables, SQL queries, HTTP requests, log records, and session metadata are all captured without any manual instrumentation.

Crash-safe storage

Recordings are written to an append-only JSONL file, so data is never lost even if your process crashes mid-write.
Slomo requires Python 3.12 or later and is licensed under the MIT License. See the Installation page for full system requirements.