Nu
The interaction primitive.
Build apps in one primitive that spans your whole stack (databases, UIs, AI agents, and services). No glue. 50x less code.
Every app is a set of interactions between systems: a database, a UI, AI agents, and services. Nu makes interaction the primitive:
- Ref names what you touch. A KV slot, a UI widget, an LLM endpoint, a memory slot, a remote object.
- Interaction describes what to do with it. Read, write, branch, iterate, compose.
- Fabric binds Refs to a real backend. Swap the Fabric, keep the tree.
Persistence, reactivity, atomicity, observability, and scalability are inherent, not bolted on.
The interaction model
Nu, the one core atom, splits into two:
- Ref: address to any resource.
- Interaction: the work over Refs.
Interaction has five kinds:
- Query: pure evaluation, yields values.
- Command: mutation, yields nothing.
- Action: mutation, yields values.
- Span: scope wrapping a body.
- Flow: orchestration of mutations.
Compose them into a tree. That is a Nu program.
Example
A dashboard on a live counter that persists across restarts. One Nu tree, two Fabrics.
import nu
class Counter(nu.Shape):
value: nu.v.IntRef
class Dashboard(nu.ui.Page):
count: nu.ui.TextRef
class App(nu.ui.Index):
pages = nu.ui.Pages({"/": Dashboard})
app = nu.With(
nu.v.presets.rocksdb_navigator(".dbtest"),
nu.ui.presets.server(
nu.v.auto_flow_atomic(
nu.ReactForever(
Counter.value.on_change(),
Dashboard.count.set(Counter.value),
),
),
),
body=(
nu.IfDo(Counter.value.missing(), Counter.value.set(0))
>> nu.ForeverDo(
Counter.value.inc() >> nu.Delay(1.0),
)
),
)
if __name__ == "__main__":
import asyncio
asyncio.run(nu.arun(nu.v.auto_flow_atomic(app)))
Run it, open the browser tab. The counter ticks once a second, the dashboard mirrors it live. Kill it, run again, it picks up where it left off.
More examples in examples/. Full walkthrough at nustack.dev/docs.
Fabrics
A Fabric implements Refs against one backend. Nu ships five in-tree.
| Fabric | What |
|---|---|
nu.m |
In-process substrate. Zero-config default for tests, notebooks, cache. |
nu.v |
Persistent substrate backed by virtuals. Virtual Python collections over RocksDB, LMDB, more. |
nu.ui |
Refs on screen. Binds Nu Refs to a live browser tab. |
nu.invisibles |
Location-independent Nus. Transparent RPC across processes and machines. |
nu.ray |
Compute across the cluster. Scale Nu on Ray without leaving the model. |
Swap the Fabric, keep the tree. Same program runs against different substrates.
Install
From source. Python 3.12+. See nustack.dev/docs/how-to/install for the full guide (Python side, UI bundle, verify).
Apps built on Nu
- nulog. Structured logging as a Nu app. Handles billions of entries, UI dashboard out of the box.
Status
v0.1.0. APIs will break, no backwards compatibility guarantees.
License
Apache-2.0
1 maintainer
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