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Deep Dive: RL for Coding Agents1 / 2

1 min lesson

Long-horizon RL on real coding problems

Name the parts in "Long-horizon RL on real coding problems" and give the practical job of each one.

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Long-horizon RL on real coding problems

The unit of training is a real coding problem set inside a copy of its repo. For each problem the trainer runs many rollouts in parallel, each a full agent episode against its own simulated copy of the codebase. The successful rollouts get reinforced; the policy is updated away from the ones that failed.

What one rollout actually costs
Scale per rollout
A single rollout can reach 200K tokens and hundreds of tool calls before it terminates.
Many per problem
Each real problem is run many times so the group has both successes and failures to learn from.
Isolated copies
Every rollout works against its own simulated copy of the repo, so edits and test runs don't collide.
Terminal signal
Reward arrives at the end from the environment's tests - the sparse, verifiable signal from section three.

Hundreds of tool calls and 200K tokens per rollout is why environment throughput and self-summarization both matter.