The Function That Lied: How a Duplicate def Silently Broke GIF Trimming in My 16,000-Line Flask App.

This is a submission for DEV's Summer Bug Smash: Clear the Lineup powered by Sentry.

Project Overview

snipforge.video is an AI video editing SaaS I run solo. Users upload a video and run tools on it in the browser: trimming, compression, GIF creation, AI dubbing with speaker diarization, auto captions, background removal, and about twenty other operations. Under the hood it is a single-file Flask app of roughly 16,000 lines, deployed on Railway, with FFmpeg doing the heavy lifting and Cloudflare R2 storing the media.

Being a solo founder means I am also the QA team, which is fitting because my day job is Lead QE. This bug still got past me for a while, and the reason it did is the interesting part.

Bug Fix or Performance Improvement