Models

Browse models available through the NT inference API — base models and their fine-tunes.

Draft — pending review.

This page hasn't been reviewed yet. Content may change before it's considered ready.

The NT inference API serves the MolmoAct-2 family. The base entry defines the wire contract for a robot class. Fine-tunes specialize behavior for a specific task; each inherits or declares its own contract.

Pick a model

Browse base models and their fine-tunes. Start with the family that matches your hardware.

Read a contract

Understand the state shape, cameras, and action shape the API enforces for each model.

Quickstart

Connect to the API and run inference in under 20 lines.

Contract quick reference

Every model exposes a contract — the wire shapes the API enforces on observation and action frames. The server validates your first obs frame against the contract and closes with 4422 on mismatch.

Field	What it means
`state_shape`	Dimensions of the joint-state vector your `read_state()` callback must return
`state_dtype`	Expected dtype — `float32` for all current models
`cameras`	Nested object — `required` camera keys must be present in your `images` dict (missing one closes `4422`); `expected` camera keys zero-fill if missing
`image_shape`	Expected shape of each camera array, channels-first (`[C, H, W]`)
`action_shape`	Shape of the action chunk the server returns — `[horizon, action_dim]`
`tags`	Docker-style identifiers for the model — the string you pass to `Robot(model=...)`

The full contract for any model is available from the always-on registry — no GPU warmup needed:

curl -H "Authorization: Bearer $NT_API_KEY" \
  https://nt-registry-production.up.railway.app/v1/models/ft_6341c5_d13da9

Fine-tune entries return the resolved contract inherited from their base. See Reference → Models for per-model contract documentation.

Model families

Family	Base UID	Description	Fine-tunes
MolmoAct-2	`ft_base_molmoact2`	Bimanual, not directly deployable — pick a fine-tune	SO-101