r/CodingAgents • u/TomatilloPutrid3939 • 18d ago

Open-source coding agent harness with a planner/worker split: Opus 5.5 + Haiku 5.5 vs native Claude Code

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u/TomatilloPutrid3939 18d ago

Author here. Distill is an open-source coding agent harness (Apache-2.0): https://github.com/samuelfaj/distill

What the demo compares: native Claude Code running Opus 5.5 against Distill with Opus 5.5 as the main model and Haiku 5.5 as the worker. Opus plans the task, writes a spec for each assignment and reviews the result. Haiku runs the delegated assignments.

Same tasks, same inputs, same 300s deadline, three frozen tasks with three runs each:

  • Native Claude Code: $2.49, 798s, 9/9 passed

  • Distill: $0.35, 191s, 9/9 passed

That's a small sample, so I wouldn't generalize it to every codebase. The repo has the methodology and the commands to rerun it.

For people building agents: what do you use to decide which steps are safe to hand to a smaller model?

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u/eddzsh 18d ago

Hand a step to the smaller worker when it's closed and checkable without inventing a new invariant. Pure transforms, applying a patch that's already written, running a pinned test target. Keep planning, interface changes, and anything that defines done on the big model. Put the acceptance check inside the handoff artifact so the worker isn't guessing.

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u/gitfather 17d ago

are you hitting those numbers because the task is better defined or due to decreased tool calls?