Evaluation

cosmos_framework.scripts.eval scores a checkpoint against ground truth. It has two paths, and --dataset.model-mode picks one:

--dataset.model-mode	What runs	Per-sample metrics
joint (default), forward_dynamics, inverse_dynamics, wam	Loads samples from a training dataset config, generates each one with the model, then scores it against the sample's ground truth	forward_dynamics: PSNR. inverse_dynamics: action MSE. wam: both
vision	Scores videos you have already generated against a directory of ground-truth videos. It loads no model and needs no GPU.	PSNR

joint runs all three action modes, one after the other.

Action evaluation

The dataset comes from the config.yaml that training saved in the run directory. Evaluate a checkpoint that has been exported to Hugging Face safetensors (see Training → Export checkpoint):

torchrun --nproc-per-node=8 -m cosmos_framework.scripts.eval \
  -o outputs/eval \
  --checkpoint-path $RUN_DIR/model \
  --dataset.config-file $RUN_DIR/config.yaml \
  --dataset.model-mode forward_dynamics \
  --dataset.num-samples 16

Common dataset arguments:

• --dataset.model-mode: the mode to evaluate (see the table above).
• --dataset.num-samples N: evaluate at most N samples per mode. By default the N samples are a deterministic pseudo-random subset of the candidates (stable for the same dataset label and seed), not the first N.
• --dataset.sample-selection-strategy {deterministic_random,first}: how --dataset.num-samples picks its subset. Use first for the leading samples.
• --dataset.sample-selection-seed S: seed for deterministic_random (default 42).
• --dataset.dataset NAME: choose one dataloader or dataset by name when the config defines several. If you leave it out, the first one is used.
• --dataset.dataset-split {val,train,full}: the split to load. The default is val. With val or full, training-only caption dropout is turned off.
• --dataset.sample-stride K: evaluate every K-th sample.
• --dataset.dataset-kwargs / --dataset.transform-kwargs: override fields of the inner dataset config or the outer dataset config (for example its transform) before instantiation. Nested dictionaries are merged, and resolution is only written when the dataset config declares it.
• --no-compute-metrics: generate the samples and skip scoring.

The usual setup arguments, such as --checkpoint-path, parallelism and sampling overrides, work the same way as in Inference.

For video metrics, the ground-truth clip is taken from the batch before generation starts. Its reflection padding is removed and it is cropped to the tokenizer's spatial alignment, so it has the same height and width as the generated vision.mp4. For action metrics, the generated action is compared with the raw ground-truth action (action_raw). If the batch has a channel mask (action_valid_mask), only the valid channels count.

Outputs, under -o:

• <dataset>/<mode>/<index>/: the generated outputs and that sample's metrics.json.
• metrics_aggregate.json: {mode: {metric: {mean, count}}}, collected from every metrics.json under the output directory.
• benchmark.json: timings, written only with --benchmark.

Scoring pre-generated videos

To score videos produced by cosmos_framework.scripts.inference, point the script at the predictions and at a directory of ground-truth videos:

python -m cosmos_framework.scripts.eval \
  -o outputs/eval_vision \
  --checkpoint-path "" \
  --dataset.model-mode vision \
  --predictions-dir outputs/inference \
  --gt-dir /path/to/gt_videos

No model is loaded in this mode. The CLI still requires --checkpoint-path, so pass an empty string.

• --predictions-glob (default **/vision.mp4) selects the prediction files under --predictions-dir.
• Each prediction is paired with <gt-dir>/<key><gt-extension>. The default --gt-extension is .mp4. For the inference output layout <group>/<key>/<output_index>/vision.*, the key is the sample directory name. For any other file name, the key is the file stem. Predictions with no matching ground truth are logged and skipped.
• If the frame counts differ, both clips are trimmed to the shorter one. Generation produces 4k+1 frames, while the ground truth keeps its original length. A difference in height or width skips that clip.
• Metrics are grouped by the path between --predictions-dir and the sample directory. Predictions at the top level are grouped under default. Each metrics.json is written to the same relative location under -o, and metrics_aggregate.json lists one entry per group.