From Tasks to Turns: Measuring Human Labor Contributions in Human-Agent Joint Production
In agent workflows, a brief human instruction can alter subsequent search, reasoning, and tool execution, yet final task outcomes rarely reveal the contribution of an individual instruction to human-agent joint production. We propose a Human Turn-level framework for measuring human contributions, using task quality and token usage to characterize the collaborative production outcomes associated with each human instruction. We compare continuations from adjacent checkpoints under matched models, budgets, and termination conditions, and assess stability through repeated measurements. Across four archived and simulated interaction settings, we conduct 29,124 comparisons between predicted and observed directions of quality and computational change at both Human Turn and session levels. On HumanBench, we obtain 506 valid comparisons across 85 real-user scenarios. Results show that quality and computational changes associated with human guidance depend on task conditions. Expert-style and ordinary-style guidance differ in information provision, correction, and repetition. Even when task quality after continuation is identical, remaining computational demands can differ substantially across checkpoints. Our framework advances the measurement of human labor contributions from tasks and sessions to individual turns, providing a repeatable, fine-grained foundation for studying human contributions and their allocation in human-agent joint production.