Skim is a speculative execution framework for web agents that exploits the predictable structure of purpose-built websites. Today's web-agent expense is not intrinsic to the tasks but a property of how agents are composed: frontier-model inference, browser rendering, and ReAct-style planning are applied to every step of every task regardless of complexity. Skim's key observation is that websites enforce stable URL patterns, answer formats, and task-to-trajectory mappings across queries of the same type, so most queries can bypass these heavyweight components entirely. An offline profiler captures these patterns once per site. At runtime, Skim matches each query to a template, synthesizes the destination URL, and extracts the answer with a small model. A lightweight verifier gates each fast-path output against the query and schema; rare misspeculations cascade to the full agent, warm-started by the fast path's final URL to preserve upstream trajectory progress. Across standard web-agent benchmarks paired with three backboneagents (WebVoyager, AgentOccam, BrowserUse), Skim reduces median per-task cost by 1.9x and latency by 33.4% with no accuracy loss.

翻译：Skim是一种面向网络代理的推测执行框架，利用特定任务网站可预测的结构化特征。当前网络代理的开销并非任务本身的固有属性，而是代理构建方式的产物：前沿模型推理、浏览器渲染及ReAct式规划等步骤，在每项任务的每个环节中均被不加区分地应用，无论其复杂程度如何。Skim的关键发现是，同一类型的查询中，网站会强制采用稳定的URL模式、答案格式及任务到轨迹的映射关系，因此多数查询可完全绕过这些重量级组件。离线分析器每站点仅需一次模式捕捉。运行时，Skim将查询匹配至对应模板，合成目标URL，并通过轻量模型抽取答案。小型验证器对每个快速路径的输出与查询及模式进行检验；罕见的推测错误将级联至完整代理，此时快速路径的最终URL将用于热启动，从而保留上游轨迹进展。在与三种骨架代理（WebVoyager、AgentOccam、BrowserUse）配对的标准网络代理基准测试中，Skim在无精度损失的前提下，将每项任务的中位成本降低1.9倍，延迟降低33.4%。