Challenge: Recent work shows that decoder-only LLMs can serve as strong embedding backbones when fine-tuned with contrastive objectives.
Approach: They propose a framework that activates the latent representation power of frozen LLMs by rerouting the final token's KV states as a prepended prefix.
Outcome: The proposed framework outperforms existing training-free baselines by 10% on MTEB and maintains robust performance on sequences up to 4,096 tokens.

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A Systematic Study of Cross-Layer KV Sharing for Efficient LLM Inference (2025.naacl-short)

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Challenge: Recent studies have shown that sharing key-value (KV) cache across layers is effective in efficient inference of large language models.
Approach: They propose a unified framework that covers several recent methods and their novel variants to investigate cross-layer KV sharing.
Outcome: The proposed framework achieves higher throughput and better performance when reducing the size of the key-value cache by 2 while maintaining competitive performance.
Causal2Vec: Improving Decoder-only LLMs as Embedding Models through a Contextual Token (2026.acl-long)

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Challenge: Existing methods modify attention mechanism to be bidirectional, undermining LLMs’ ability to extract semantic information acquired during pre-training.
Approach: They propose a general-purpose embedding model that pre-encodes input text into a single Contextual token and then prepends it to the LLM's input sequence.
Outcome: The proposed model improves performance of decoder-only large language models without altering their architectures or introducing significant computational overhead.
GenEOL: Harnessing the Generative Power of LLMs for Training-Free Sentence Embeddings (2025.findings-naacl)

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Challenge: Training-free embedding methods focus on optimizing embeddable prompts . previous methods have overlooked the benefits of utilizing generative abilities of LLMs - GenEOL .
Approach: They propose a method that leverages pretrained large language models to embed text . they propose generating diverse transformations of a sentence that preserve its meaning .
Outcome: The proposed method outperforms existing training-free embedding methods by 2.85 points on the sentence semantic text similarity (STS) benchmark.
KV-Latent: Dimensional-level KV Cache Reduction with Frequency-aware Rotary Positional Embedding (2025.acl-long)

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Challenge: Large language models (LLMs) based on Transformer Decoders have become the preferred choice for conversational generative AI.
Approach: They propose a paradigm called KV-Latent to reduce the KV cache footprint and improve inference speed by down-sampling the Key-Value vector dimensions into a latent space.
Outcome: The proposed paradigm reduces the KV Cache footprint and improves inference speed with a small amount of extra training, less than 1% of pre-training takes.
Exploring the Hidden Capacity of LLMs for One-Step Text Generation (2025.emnlp-main)

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Challenge: Large language models (LLMs) can reconstruct surprisingly long texts via autoregressive generation from just one trained input embedding.
Approach: They show that large language models can reconstruct surprisingly long texts via autoregressive generation from just one trained input embedding.
Outcome: The proposed model can generate hundreds of accurate tokens in one token-parallel forward pass, when provided with only two learned embeddings.
Token Prepending: A Training-Free Approach for Eliciting Better Sentence Embeddings from LLMs (2025.acl-long)

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Challenge: Recent studies have focused on prompt engineering to extract sentence embeddings from large language models (LLMs) but these models are mostly decoder-only and the earlier tokens in the sentence cannot attend to the latter, resulting in biased encoding of sentence information and cascading effects on the final decoded token.
Approach: They propose a plug-and-play and training-free technique that prepends each layer’s decoded sentence embedding to the beginning of the sentence in the next layer’ s input.
Outcome: The proposed technique can significantly improve the performance of existing prompt-based sentence embedding methods across different LLMs while incurring negligible additional inference cost.
Improving Text Embeddings with Large Language Models (2024.acl-long)

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Challenge: Existing methods for obtaining text embeddings require complex training pipelines . authors leverage proprietary LLMs to generate diverse synthetic data for text embeds based on 93 languages .
Approach: They propose a method for obtaining high-quality text embeddings using only synthetic data and less than 1k training steps.
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LLM-QAT: Data-Free Quantization Aware Training for Large Language Models (2024.findings-acl)

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Challenge: Several post-training quantization methods have been shown to perform well down to 8-bits.
Approach: They propose a data-free distillation method that leverages generations produced by the pre-trained model to quantize any generative model independent of its training data.
Outcome: The proposed method outperforms SoTA PTQ and LLaMA models at low bit precision.
T-FREE: Subword Tokenizer-Free Generative LLMs via Sparse Representations for Memory-Efficient Embeddings (2024.emnlp-main)

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Challenge: Tokenizers are crucial for encoding information in Large Language Models, but their development has stagnated.
Approach: They propose a tokenizer that embeds words through sparse activation patterns over character triplets . they show competitive downstream performance with a parameter reduction of more than 85% .
Outcome: The proposed approach achieves competitive downstream performance with a parameter reduction of more than 85% on embedding layers.
Tokenizer-Aware Cross-Lingual Adaptation of Decoder-Only LLMs through Embedding Relearning and Swapping (2026.eacl-long)

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Challenge: Large Language Models (LLMs) have been primarily focused on English, leaving the multilingual ability unexplored.
Approach: They propose a technique that creates new tokenizers and tunes embeddings on fixed model weights for target language adaptation.
Outcome: The proposed method is light-weight and performant but has limitations for older models and high resource languages.

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