In plain words: Instead of writing its reasoning word by word, the model feeds its internal hidden state back in as the next input, so it thinks in continuous vectors. This beat word-based step-by-step reasoning on logic puzzles needing heavy search, while balancing accuracy and speed better.
Abstract · Training Large Language Models to Reason in a Continuous Latent Space
Large language models (LLMs) are typically constrained to reason in the language space, where they express the reasoning process through a chain-of-thought (CoT) to solve complex problems. However, the language space may not always be optimal for reasoning. Most word tokens primarily ensure textual coherence and are not essential for reasoning, while some critical tokens require complex planning and pose challenges to LLMs. To explore the potential of reasoning beyond language, we introduce a new paradigm called Coconut (Chain of Continuous Thought). Coconut utilizes the last hidden state of the LLM as a representation of the reasoning state, termed "continuous thought." Instead of decoding this state into words, we feed it back to the model as the next input embedding directly in the continuous space. This latent reasoning paradigm enables an advanced reasoning pattern, where continuous thoughts can encode multiple alternative next steps, allowing the model to perform a breadth-first search (BFS) rather than committing prematurely to a single deterministic path as in CoT. Coconut outperforms CoT on logical reasoning tasks that require substantial search during planning and achieves a better trade-off between accuracy and efficiency.
Shibo Hao, Sainbayar Sukhbaatar, DiJia Su, Xian Li, Zhiting Hu, Jason Weston, Yuandong Tian
arXiv:2412.06769 · cs.CL · submitted Dec 9, 2024 · updated Aug 23, 2026
abstract · pdf · html · Accepted to COLM 2025
I am not surprised at all that Meta was able to generate some positive returns by feeding the last hidden layer back into the model auto-regressively.
The method of training they describe in the paper is really cool. Summarized in Figure 2, they train it with a corpus of step-by-step text instructions and then across multiple stages, they iteratively replace one of the textual steps with a last-hidden-layer embedding and see what the model spits out. The weights are then updated through cross-entropy loss as the additional text tokens are generated once again.
So they're basically rewinding the output, replacing an increasing number of textual steps with hidden state embeddings, and playing it forward as the model gradually learns to do all of its step-by-step thinking using just the hidden state data.
In a way, this might be how humans learn to think through language. Our parents teach us using words and our brain gradually replaces the words with thoughts until we can replicate the action or solve the problem ourselves without anyone guiding us with words.