Pass Claude Thinking Blocks Back in Tool Loops

Across newer Claude models like Claude Fable 5.1, passing thinking blocks back unchanged across multi-step tool turns is supported to preserve reasoning continuity.

API Workflow Rule: In multi-turn tool-use trajectories on Claude Fable 5.1, pass the assistant's prior thinking blocks back unchanged in the message array when returning tool results, and never manually edit the output text following a thinking block.