Agent uses Computer Use to reverse-engineer CapCut, batch-downloads 2,291 subtitle templates
dotey · x · 2026-10-12
A hands-on agentic reverse-engineering case: the author wanted to learn CapCut's dynamic subtitle format but didn't know where or how it was stored, so they let an agent (REA + Codex) drive Computer Use itself — clicking to download templates inside CapCut while monitoring network requests and disk paths.
After a few dozen manual GUI downloads, the agent realized clicking was too slow and switched to constructing URLs directly, eventually pulling down 2,291 templates (1.3 GB). It also reverse-engineered the template package structure (config., content., extra.) and the Lua-based subtitle rendering logic, plus a manifest of 995 dependencies and failed resources.
The post extends the previously shared 'screen-record the flow, have the model replicate it' technique: beyond passive recording, letting the agent actively explore a GUI and sniff the underlying protocol is a viable way to reverse closed-source formats.
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