when-model-merging-rivals-joint-multi-task-reinforcement-learning-a-task-vector-geometry-analysis-fee72dc0·1 events·first seen Aliases: When Model Merging Rivals Joint Multi-Task Reinforcement Learning: A Task-Vector Geometry Analysis
A new arXiv paper provides the first direct comparison of model merging versus joint multi-task reinforcement learning training, using Qwen3-8B specialists trained on the AppWorld agent benchmark with the LOOP algorithm. Merging methods (TIES, RAM+) statistically match jointly trained models on task-goal completion. The authors explain this via task vector geometry: specialist task vectors are near-orthogonal (cosine similarity 0.06–0.10) despite ~65% parameter support overlap, causing sign- and support-based merging methods to collapse to near-uniform averaging.