One task, three workers, three worktrees.
Opus 5 split it into packets, OpenCode 2 workers on DeepSeek 4.1 Flash built the pages in parallel, and I reviewed every diff before merging what passed. All of it on the record. Open source,
How Claude Opus 5 Deals with assumptions.
Made in Three.js
Two Anthropic engineers spent $200 and 6 hours on one prompt, and the result is the clearest argument yet that the harness still matters
The prompt was five words: build a retro game maker they ran it twice. same model, same prompt. the only difference was the scaffolding
Deepseek-v4.1 local beats Opus-5
Best 2 out of 3 matches Game 3 was intense. Opus was up 5 points of material at move 18, Stockfish had DeepSeek at -8.3 Then: Queen for a rook and it never gave the lead back No chess engine, no help. Opus needed 57 requests to make 31 moves.
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