We unveil that internal representations in large language models (LLMs) serve as reliable proxies of learned knowledge, and propose **RECALL**, a novel representation-aware model merging framework for continual learning without access to historical data. RECALL computes inter-model similarity from layer-wise hidden representations over clustered typical samples, and performs adaptive, hierarchical parameter fusion to align knowledge across models. This design enables the preservation of domain-general features in shallow layers while allowing task-specific adaptation in deeper layers. Unlike prior methods that require task labels or incur performance trade-offs, RECALL achieves seamless multi-domain integration and strong resistance to catastrophic forgetting. Extensive experiments across five NLP tasks and multiple continual learning scenarios show that RECALL outperforms baselines in both knowledge retention and generalization, providing a scalable and data-free solution for evolving LLMs.

The ClimateCheck shared task addresses the critical challenge of grounding social media claims about climate change in scientific literature. This paper details our winning approach. For abstract retrieval, we propose a multi-stage pipeline: (1) initial candidate generation from a corpus of ~400,000 abstracts using BM25; (2) fine-grained reranking of these candidates using an ensemble of BGE-Reranker cross-encoder models, fine-tuned with a specialized training set incorporating both random and hard negative samples; and (3) final list selection based on an RRF-ensembled score. For the verification aspect, we leverage Gemini 2.5 Pro to classify the relationship (Supports, Refutes, Not Enough Information) between claims and the retrieved abstracts, guided by carefully engineered prompts. Our system achieved first place in both subtasks, demonstrating the efficacy of combining robust sparse retrieval, powerful neural rerankers, strategic negative sampling, and LLM-based semantic analysis for connecting social media discourse to scientific evidence. Part of the example code: https://anonymous.4open.science/r/climatecheck_solution-1120