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name: environments-and-vectorization description: "Create and validate Gymnasium custom environments for Stable-Baselines3, then wrap them safely with Monitor, DummyVecEnv/SubprocVecEnv, VecNormalize, VecCheckNan, and frame/dict/image vector wrappers." disable-model-invocation: true metadata: disco-role: operating license: MIT

Environments And Vectorization

Use this sub-skill when the task is about Stable-Baselines3 environment compatibility rather than algorithm selection: custom Gymnasium env APIs, check_env, vectorized env construction, VecEnv API semantics, Monitor logging, normalization, NaN checks, frame stacking, dict/image observations, and multiprocessing caveats.

Route By Task

• Custom env contract or check_env failure: use references/custom-envs.md for the required reset()/step() API, spaces, image/dict observations, unsupported spaces, and the validation checklist.
• Vectorization, wrappers, or VecEnv behavior: use references/vectorized-envs.md for make_vec_env, DummyVecEnv, SubprocVecEnv, automatic resets, terminal_observation, seeding/options, VecNormalize, VecCheckNan, VecFrameStack, and dict/image wrappers.
• Exact signatures and wrapper matrix: use references/api-reference.md for SB3 environment helper signatures and return-value expectations.
• Errors, warnings, and edge cases: use references/troubleshooting.md for reset/step shape mismatches, Gymnasium vs VecEnv API confusion, unsupported spaces, image warnings, non-zero-start spaces, NaNs/Infs, and subprocess start-method failures.
• Quick local validation: run python sub-skills/environments-and-vectorization/scripts/check_custom_env.py --mode valid or --mode invalid from a copied skill tree that has Stable-Baselines3 installed.

Boundaries

• This sub-skill covers env creation, validation, wrapping, vectorization, and observation/action-space compatibility.
• For choosing PPO/SAC/DQN/A2C/TD3/DDPG/HerReplayBuffer or setting training hyperparameters, route to training-and-algorithms.
• For evaluation callbacks, model save/load, VecNormalize persistence during evaluation, or rollout metrics, route to evaluation-and-persistence.
• For custom policy classes, feature extractors, MultiInputPolicy internals, or normalize_images=False policy details, route to policies-and-customization after confirming the env observation routing here.