> Canonical page: https://posttrainllm.com/sae-timeline

# SAE timeline

Drop a .jsonl produced by posttrainllm sae --checkpoint-dir … --timeline-out … . The page plots reconstruction MSE and L0 feature activity across training checkpoints, with group-SAE rows filterable by layer group.

Drop an SAE timeline .jsonl here or click to choose

Expected row keys: step, layer/layers, d_model, d_features, mse, l0_per_sample, l0_frac, sae_path, ckpt_path.

no file loaded

 Clear

 Layer group

## Reconstruction MSE

## L0 feature activity

## Latest checkpoint summary

## Timeline rows

no SAE timeline loaded yet

Drop JSONL rows with step, mse, l0_per_sample, l0_frac, sae_path, ckpt_path.

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