Research map / Reinforcement learning / Policy gradient and actor-critic
Latent Safety-Constrained Policy Approach for Safe Offline Reinforcement Learning
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Proposes LSPC, which models safe behavior with a CVAE in latent space and trains a reward-AWR latent encoder to maximize reward under inferred safety constraints for safe offline RL.
Problem
Safe offline RL requires maximizing reward while strictly satisfying cost constraints using only a static dataset, where overly restrictive constraints hurt reward and overly loose ones allow unsafe out-of-distribution actions.
Approach
Learn a CVAE over state-action pairs weighted by cost advantage to form a conservatively safe latent policy, then train a state-conditioned latent encoder with reward-advantage weighted regression whose outputs are squashed by tanh into a restricted high-probability latent region, yielding LSPC-O.
Key results
- LSPC-O reaches average normalized reward 0.72 with cost 0.29 on MetaDrive, versus FISOR 0.36/0.08 and CDT 0.42/0.80.
- LSPC-O averages reward 0.40 with cost 0.27 on Safety Gym and reward 0.54 with cost 0.20 on Bullet Safety Gym, the best safe reward among methods on Bullet Safety Gym.
- Theoretical bounds on performance gap and constraint violation scale with (1/(1-gamma)^2)(sqrt(eps1'/2)+sqrt(eps2'/2)); sample complexity analysis gives decay rate O(1/N^(0.25+v)).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use reward-optimized latent embeddings (LSPC-O) instead of LSPC-S | LSPC · Metadrive average | normalized reward: 0.67 -> 0.72 | Helped |
| Use reward-optimized latent embeddings (LSPC-O) instead of LSPC-S | LSPC · Metadrive average | normalized cost: 0.17 -> 0.29 | Hurt |
| Use reward-optimized latent embeddings (LSPC-O) instead of LSPC-S | LSPC · Safety Gym average | normalized reward: 0.32 -> 0.40 | Helped |
| Use reward-optimized latent embeddings (LSPC-O) instead of LSPC-S | LSPC · Safety Gym average | normalized cost: 0.32 -> 0.27 | Helped |
| Use reward-optimized latent embeddings (LSPC-O) instead of LSPC-S | LSPC · Bullet Safety Gym average | normalized reward: 0.32 -> 0.54 | Helped |
| Use reward-optimized latent embeddings (LSPC-O) instead of LSPC-S | LSPC · Bullet Safety Gym average | normalized cost: 0.04 -> 0.20 | Hurt |
| Increase the latent safety restriction parameter (ablation) | LSPC-O · restriction-parameter evaluation | reward return | Helped |
| Increase the latent safety restriction parameter (ablation) | LSPC-O · restriction-parameter evaluation | cost return | Hurt |
Surprising findings
- Reported that BC-Safe, which uses only safe data subsets, often outperforms FISOR and CDT in reward despite lacking reward-label use.
Limitations
- Choosing the latent restriction epsilon (degree of restriction) is not theoretically linked to cost value and must be tuned.
- Sample complexity analysis is worst-case and relies on Donsker-type assumptions on the policy class.
- Some Bullet Safety Gym tasks use a different restriction value (0.6) than others, indicating per-domain tuning.
Experimental setup
Datasets: DSRL benchmark (MetaDrive, Safety Gymnasium, Bullet Safety Gym offline datasets)
Benchmarks: DSRL MetaDrive DSRL Safety Gymnasium DSRL Bullet Safety Gym
Metrics: normalized reward return normalized cost return
Baselines: BC-Safe CDT CPQ FISOR
Builds on: Implicit Q-learning advantage-weighted regression CPQ FISOR DSRL
Closest papers by meaning
- Online Optimization for Offline Safe Reinforcement Learning (NeurIPS 2025 · similarity 0.91)
- Safe Offline Reinforcement Learning with Feasibility-Guided Diffusion Model (ICLR 2024 · similarity 0.90)
- Don’t Trade Off Safety: Diffusion Regularization for Constrained Offline RL (NeurIPS 2025 · similarity 0.90)
- Offline Safe Reinforcement Learning Using Trajectory Classification (AAAI 2025 · similarity 0.90)
- Constraint-Adaptive Policy Switching for Offline Safe Reinforcement Learning (AAAI 2025 · similarity 0.90)
- Safety Representations for Safer Policy Learning (ICLR 2025 · similarity 0.90)
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