To mitigate high inference costs for in-context learning, prior works have proposed activation-space task vectors that encapsulate demonstration contexts into static representations. However, performance occasionally degrades across tasks, leaving it unclear whether this stems from sub-optimal extraction heuristics or fundamental limitations. We resolve this by decomposing Transformer self-attention to establish a theoretical best-case approximation: the Minimal-Gap Approximation. By isolating structural constraints from heuristic flaws, the Minimal-Gap Approximation reveals that task vectors are fundamentally bottlenecked by attention and length gaps. Specifically, because task vectors lock contextual information to fixed attention maps and positional alignments, they structurally fail under dynamic routing, length mismatches, and multi-token generation. We further show that these findings consistently hold across training-free extract-and-inject task vector methods, model architectures, and model scales.

Large language models (LLMs) have evolved from pure text generators into interactive agents capable of invoking external tools. However, LLM agents still struggle with goal-oriented queries, which require decomposing high-level objectives into sequences of interdependent API calls with accurate planning and execution. Current approaches rely on zero-shot evaluation due to the absence of training data; while proprietary models such as GPT-4 exhibit strong reasoning capabilities, smaller open-source models remain ineffective at complex tool use. To address this limitation, we propose a novel training framework GOAT, that enables fine-tuning LLM agents without human annotation. GOAT automatically synthesizes goal-oriented API execution data from API documents using a novel call-first generation paradigm, that constructs training data based on executed API call sequences. Through extensive experiments, we show that GOAT-trained agents achieve state-of-the-art performance across multiple existing goal-oriented benchmarks. In addition, we introduce GOATBench, a new goal-oriented API execution benchmark, and demonstrate that agents trained with GOAT also excel in this setting. These results highlight GOAT as a practical path toward building robust open-source LLM agents capable of complex reasoning and tool use.

For embodied agents capable of physical interaction, the capability to create and understand dialog is crucial to ensure both safety and effectiveness. While DialNav provides a framework for holistic evaluation of the dialog–execution loop in photorealistic indoor navigation, its performance remains limited by a critical scarcity of training data (2K episodes) To address this, we propose an automatic generation pipeline and generate the RAINbow dataset, a large-scale training dataset with 238K episodes for DialNav. Then, we introduce two additional complementary advances to unlock the data’s full potential: (1) a navigation training scheme to align the navigation training with the dynamic dialog-navigation loop, and (2) a localization model that leverages VLN knowledge. By combining these complementary solutions, our model substantially outperforms the success rate of the baseline on both Val Seen (58.24, +89%) and Val Unseen (29.05, +100%) splits, establishing a new state of the art. We will publicly release our dataset, code, and models.