LLMs are transforming customer service, yet evaluating service agents across diverse business scenarios remains costly and fragmented, as each new domain requires building a dedicated benchmark from scratch. Existing benchmarks rely on static, scenario-specific scripts with two fundamental limitations: ***Scenario Silos***, where each domain demands costly independent annotation with no shared evaluation structure, and ***Dialogue Dynamics Gap***, where fixed scripts fail to capture the full range of real user behaviors. We propose **SAGE** (**S**ervice **A**gent **G**raph-guided **E**valuation), to our knowledge the first scenario-extensible benchmark to jointly assess logical SOP compliance and conversational quality, abstracting any SOP as a directed graph and bridging Scenario Silos through a lightweight two-step extension mechanism. SAGE further enables dynamic multi-turn simulation via adversarial user agents to overcome the Dynamics Gap. Across six industrial scenarios representative of real-world customer service deployment, we evaluate 27 mainstream LLMs spanning both closed-source systems and open-source families, offering a fine-grained capability map to guide real-world model selection. Our experiments further reveal two systematic failure patterns shared across all tested models: while models generally succeed at recognizing user intent, they frequently struggle to follow complex business logic and execute the correct subsequent action; and they sustain a warm and empathetic conversational tone even when their underlying procedural reasoning has already failed. **Code and resources are available at: https://github.com/lingshi6565/SAGE-Bench.**

Dense large language models (LLMs) face critical efficiency bottlenecks, as they rigidly activate all parameters regardless of input complexity. While existing sparsity methods (static pruning or dynamic activation) partially address this issue, they either lack adaptivity to contextual or model structural demands or incur prohibitive computational overhead. Inspired by the human brain’s dual-process mechanisms — predictive coding (N400) for backbone sparsity and structural reanalysis (P600) for complex contexts — we propose CLADA, a Cognitive-Load-Aware Dynamic Activation framework that synergizes statistical sparsity with semantic adaptability.Our key insight is that LLM activations exhibit two complementary patterns: 1. Global Statistical Sparsity driven by sequence-level prefix information, and 2. Local Semantic Adaptability modulated by cognitive load metrics (e.g., surprisal and entropy). CLADA employs a hierarchical thresholding strategy: a baseline derived from offline error-controlled optimization ensures over 40% sparsity, which is then dynamically adjusted using real-time cognitive signals. Evaluations across six mainstream LLMs and nine benchmarks demonstrate that CLADA achieves 20% average speedup with less than 2% accuracy degradation, outperforming Griffin (over 5% degradation) and TT (negligible speedup).Crucially, we establish the first formal connection between neurolinguistic event-related potential (ERP) components and LLM efficiency mechanisms through multi-level regression analysis (R² = 0.17), revealing a sparsity–adaptation synergy. Requiring no retraining or architectural changes, CLADA provides a deployable solution for resource-aware LLM inference while advancing biologically inspired AI design.