PiSSA-style SVD init for LoRA adapters also improves downstream RL training, Trajectory Labs reports

simonguozirui · x · 2026-09-17

The Trajectory Labs team shared a hands-on study: initializing LoRA adapters with the top-k SVD components of pretrained weights (PiSSA, 2024), already known to help SFT, also improves downstream RL training — an idea first suggested in John Schulman's "LoRA Without Regret" blog. They published a blog with clear visuals on why initialization matters and merged the code into SkyRL for others to reproduce. Future directions include LoRA-GA and, for alignment, selecting training directions orthogonal to alignment-critical ones.

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