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# LEAPP: Lightweight Export Annotations for Policy Pipelines
[Full Isaac LEAPP docs](https://nvidia-isaac.github.io/leapp/)
**Export the policy code you already run: preprocessing, model inference, and action processing together.**
Isaac LEAPP is NVIDIA's library for machine learning pipeline export. It traces supported PyTorch and NumPy computation across existing functions and objects. Export the complete path as **one ONNX, TorchScript, or PT2 model**, or choose separate stages when useful.
Input and output annotations capture computation as your application runs. A single model can capture computation across multiple input call sites, helper functions, and class methods. The annotations work directly in application code without a prescribed RL environment interface. [See annotation patterns](https://nvidia-isaac.github.io/leapp/guides/nodes.html).
- **Keep processing with the policy.** Capture supported NumPy preprocessing, conversions into PyTorch, and action transforms together. [Warp kernel regions](https://nvidia-isaac.github.io/leapp/tensor_libraries/warp.html) can also be captured into ONNX or PT2 with an additional runtime adapter.
- **Adapt unsupported calls with [FunctionPatch](https://nvidia-isaac.github.io/leapp/guides/patching.html).** Register a faithful replacement built from supported operations; existing module-level callers can stay in place.
- **Describe the deployment interface.** Attach tensor roles, joint names, and timing information with [semantic metadata](https://nvidia-isaac.github.io/leapp/semantics/usage.html), so downstream applications can interpret model inputs and outputs.
- **Inspect and validate the export.** Compare exported outputs, including state updates, against cached samples from consecutive Python iterations. Configure sample coverage, inspect the graph, and use [sequential replay](https://nvidia-isaac.github.io/leapp/guides/debugging.html#stateful-transitions-and-sequential-replay) to check accumulated drift and runtime feedback.
## Quick start
```bash
pip install leapp
```
Requires Python 3.10+ and PyTorch 2.7.0+.
This example exports NumPy preprocessing, a small PyTorch policy, and action scaling and clipping together:
```python
import numpy as np
import torch
import leapp
from leapp import annotate
def make_observation(position, velocity):
return np.concatenate([np.clip(position, -1.0, 1.0), velocity * 0.1])
policy = torch.nn.Sequential(
torch.nn.Linear(12, 32), torch.nn.Tanh(), torch.nn.Linear(32, 6),
).eval()
leapp.start(name="robot_policy")
position, velocity = annotate.input_tensors("control", {
"position": np.zeros(6, dtype=np.float32),
"velocity": np.ones(6, dtype=np.float32),
})
with torch.no_grad():
observation = torch.from_numpy(make_observation(position, velocity))
targets = torch.clamp(policy(observation) * 0.25, -1.0, 1.0)
annotate.output_tensors("control", {"targets": targets}, export_with="onnx")
leapp.stop()
leapp.compile_graph(validate=True)
```
Produces **`robot_policy/control.onnx`**, a YAML interface specification, and a graph PNG on Python 3.11+. This stateless model runs directly in ONNX Runtime; [InferenceManager](https://nvidia-isaac.github.io/leapp/leapp_runtime.html) loads the bundle for Python replay. Other applications can consume the exported artifacts through their chosen backend runtime.
## Capture scope
LEAPP captures the executed tensor path. Data-dependent Python branches are not preserved dynamically, and unsupported operations or scalar extraction can freeze values. Check tracing warnings and validate on fresh inputs. See [PyTorch](https://nvidia-isaac.github.io/leapp/tensor_libraries/torch_limitations.html) and [NumPy](https://nvidia-isaac.github.io/leapp/tensor_libraries/limitations.html) limitations.
[Getting started](https://nvidia-isaac.github.io/leapp/getting_started.html) · [Export options](https://nvidia-isaac.github.io/leapp/guides/export.html) · [API reference](https://nvidia-isaac.github.io/leapp/api/index.html)
## License
Copyright (c) 2026, NVIDIA Corporation & affiliates. Licensed under the Apache License, Version 2.0. See [LICENSE](LICENSE) and [thirdparty.txt](thirdparty.txt).