CoSTAast: Cost-Sensitive Toolpath Agent for Multi-turn Image Editing
Authors: name: Advait Gupta; name: NandaKiran Velaga; name: Dang Nguyen; name: Tianyi Zhou
Published: 2025-03-13 17:55:45

Abstract: Text-to-image models like stable diffusion and DALLE-3 still struggle with
multi-turn image editing. We decompose such a task as an agentic workflow
(path) of tool use that addresses a sequence of subtasks by AI tools of varying
costs. Conventional search algorithms require expensive exploration to find
tool paths. While large language models (LLMs) possess prior knowledge of
subtask planning, they may lack accurate estimations of capabilities and costs
of tools to determine which to apply in each subtask. Can we combine the
strengths of both LLMs and graph search to find cost-efficient tool paths? We
propose a three-stage approach "CoSTA*" that leverages LLMs to create a subtask
tree, which helps prune a graph of AI tools for the given task, and then
conducts A* search on the small subgraph to find a tool path. To better balance
the total cost and quality, CoSTA* combines both metrics of each tool on every
subtask to guide the A* search. Each subtask's output is then evaluated by a
vision-language model (VLM), where a failure will trigger an update of the
tool's cost and quality on the subtask. Hence, the A* search can recover from
failures quickly to explore other paths. Moreover, CoSTA* can automatically
switch between modalities across subtasks for a better cost-quality trade-off.
We build a novel benchmark of challenging multi-turn image editing, on which
CoSTA* outperforms state-of-the-art image-editing models or agents in terms of
both cost and quality, and performs versatile trade-offs upon user preference.