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Can language models discover new expertise through collaborative weight search?

Can model experts be composed through particle swarm optimization in weight space without training? This explores whether collaborative search can discover capabilities that no individual expert possesses.

Synthesis note · 2026-02-23 · sourced from Agents Multi Architecture

Model composition has two dominant approaches: learn-to-fuse (train components to glue experts together — data-heavy, rigid) and model arithmetic (weight operations with strong assumptions like lion_indoors = lion_outdoors + dog_indoors - dog_outdoors — assumption-heavy, manual). MODEL SWARMS proposes a third way: collaborative search in weight space inspired by particle swarm optimization.

Each LLM expert is a particle with a location (model weights) and velocity (direction in weight space). Velocity is iteratively updated by three forces: inertia (tendency to keep moving), personal best (the best location this particle has found), and global best/worst (the best/worst locations found across all particles). Particles then step toward their updated velocity.

Three key properties make this distinctive:

1. Training-free. No loss function, gradient descent, or backpropagation. Composition requires only 200 examples as validation signal — barely 3 batches for training-based approaches.

2. Assumption-free. No manual specification of how experts should compose. The swarm automatically discovers better adapted experts through collaborative search.

3. Any adaptation objective. The utility function can be anything — dataset performance, reward model scores, human interests. This flexibility is structural, not parameter-tuned.

The most interesting finding is correctness emergence: new capabilities appear that no initial expert had. Questions where all experts initially answered incorrectly are answered correctly by post-swarm experts. This is not transfer — it is genuinely new capability discovered through search in weight space.

Practical results: 17.6% improvement in LLM-as-judge scores, 17.0% in factuality, 70.8% human win rate against initial experts (96% on best domains). MODEL SWARMS also drastically reduces sensitivity to minor prompt changes — improving robustness through weight-space optimization rather than prompt engineering.

Token swarms extend the approach to cross-architecture composition by operating on token probability distributions rather than weights.

Inquiring lines that read this note 26

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Can base models hide emergent misalignment through alignment training? Can AI systems discover fundamental improvements to their own architectures? How do neural networks learn compositional structure from training? How does diversity prevent model convergence on superficial patterns? Can artificial systems establish authority in domains requiring expert judgment? Can smaller specialized models match frontier models on key metrics? Does AI-assisted research sacrifice exploration breadth for productivity gains? How do training data quality and composition affect downstream model performance? How does fine-tuning trade off accuracy against reasoning quality? How do curriculum design and feedback approaches affect model learning? How does model capacity affect learning performance on diverse downstream tasks? How do sequence length and task type interact with sparsity tolerance? Does intelligent routing among smaller models outperform training larger models? What explains the gap between benchmark scores and true reasoning capability? Can inference-time computation adaptively substitute for static model capacity? How can evaluations be made robust against model reward hacking?

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Original note title

swarm intelligence in weight space discovers adapted language model experts without training through collaborative search guided by utility functions