Retrace – reverse debugging for production CPython applications

In plain words

Retrace is a reverse debugger for CPython applications that records production failures by capturing interactions with external systems like databases, networks, and filesystems, then replays them locally in VS Code. Developers can step through the replay forwards and backwards to diagnose issues without running the full application in production. It records boundary crossings rather than every line of code, minimizing overhead. Currently supports Python 3.11 and 3.12 on macOS and Linux with Flask, Django, requests, psycopg2, and threading.

written from the facts on this page · September 2026

From the sources

Turn failed Python tests and CI runs into replayable debug sessions. - retracesoftware/retracesoftware

In the maker’s words, at launch

Nathan here, one of the people who built Retrace. Happy to answer technical questions. Retrace records a CPython application's interactions with the nondeterministic outside world i.e. network, DB, filesystem, time, randomness, subprocesses, and lets you replay that execution locally and deterministically. The goal…

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