Opus 5.5 worked 8 hours unattended, then re-implemented code that already existed
Sauers_ · x · 2026-09-25
Developer Sauers shares that Opus 5.5 worked autonomously for 8 hours overnight, only to re-implement something that already existed — in the exact same directory it was coding in. A classic failure mode of long-horizon autonomous coding agents: no awareness of existing implementations in the codebase.
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