AI Systems Atlas

H-23Interleaved Thinking

/harnesses/interleaved-thinking

The model reasons between tool calls, reading each result before choosing the next call, instead of thinking only once up front.

Step-by-step walkthrough7 steps
  1. Same task, two harnesses. Up front: one long think writes the whole plan before any tool runs.
  2. The search result says the file has moved — and there is no thinking step to weigh what that implies.
  3. It reacts on reflex: reads the old path, edits a stale copy, answers confidently.
  4. Interleaved: think, then call.
  5. The same result comes back — and the model reasons about it before choosing the next call.
  6. The plan changes mid-flight: edit v2/ instead.
  7. Think once more on what came back, then answer. Reasoning goes where the evidence is.
Key insight

Thinking only before the first call reasons with the least evidence; thinking after each result spends reasoning where new evidence just arrived, which matters most in long tool chains where one result can invalidate the plan.

Failure mode

Thinking between every trivial call. When calls are independent or the results are predictable, the extra reasoning adds latency and tokens without changing a single decision.

Further reading
RelatedReAct loopThinking budgetsReplanner

Elsewhere in the atlas

Security →Evals →Context →Coding Agents →Tools →Ops →