π₀.₅: PaliGemma prefix + action-expert suffix + flow-matching denoising
Click any block in the architecture to see what it does, the math behind it, and the exact source lines. Then walk one sample end-to-end and stress-test yourself with the debug lab.
BackbonePaliGemma (SigLIP + Gemma)
ExpertsVLM + action expert (dual Gemma)
Timesin-cos + adaRMS (π₀.₅)
Actionscontinuous · flow matching
Click a stageMath cardSample stepperDebug trace
Upstream: https://www.physicalintelligence.company/blog/pi05 · code snapshot Physical-Intelligence/openpi @ 215abfb · Apache-2.0
Mental model
The ideas that make this code readable
Layer-by-layer math
Every formula links to the source that implements it
Follow one sample
Tensor flow
Shapes must agree across every stage
| Stage | Input | Output | Op | Note |
|---|
Debug lab
Pick the symptom, work one boundary at a time
Code excerpts
Only the lines these notes point at, from the upstream repository at the pinned commit. Gaps are marked.
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Knowledge check
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