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Build apps in one primitive that spans your whole stack — databases, UIs, AI agents, and services. No glue. 50x less code.
The primitive Nu is built on, in three words.
A tiny script keeps its values in memory and calls functions on them. Real apps don't stay there. Values live in a database, arrive from a browser form, render into a dashboard, get recomputed by a background job. Almost none of the code is about the values anymore — it's all interaction between systems.
Nu makes interaction the primitive.
- Ref — a name for a value, wherever it lives: a KV slot, a UI text block, an LLM endpoint, a remote object.
- Interaction — what you do with a Ref: read, write, branch, iterate, compose.
- Fabric — binds Refs to a real system. Compose as many as you need; they all speak the same primitive.
Same primitive, different system. One Ref for any resource, one Interaction for any op. Setting a browser text block is the same interaction as setting a KV slot.
Nu is the reference implementation of the interaction model in Python.
A few of Nu's fabrics — state, UIs, cluster, models. Same Python, same code shape.
Persistent state. Stores any Python type.
Reach any value by name; it survives restarts. Same code local or sharded across a cluster.
- Serverless, scales to terabytes
- Store any Python type
...
class DB(nu.Shape):
hits = nustd.kv.IntRef.slot()
# +1 to a persistent counter
op = DB.hits.set(DB.hits + 1)
app = nu.With(
nustd.kv.rocksdb_navigator(".db"),
body=nustd.kv.auto_flow_atomic(op),
)
...Powered by virtuals · rdbpy · RocksDB · LMDB.
Reactive UIs from Python. No JS, no build step, no websocket you had to write.
A text block, a chart, a form — set them like variables, they render. Update the value, the browser updates itself.
- 50+ components out of the box
- Live updates for free
...
class Dashboard(nustd.ui.Page):
hello = nustd.ui.TextRef.slot()
# renders live in the browser
op = Dashboard.hello.set("Hello, browser.")
app = nustd.ui.serve(Dashboard, op)
...Same code runs local or across the cluster. No worker pool to run.
Teleport any Nu tree to any worker; it runs there and returns the result. Where it runs is a binding, not a rewrite.
- Same code, local or remote
- Distribute with a single line
...
class DB(nu.Shape):
hits = nustd.kv.IntRef.slot()
# any Nu op
op = DB.hits.set(DB.hits + 1)
# same op — teleport it to a worker
remote = nustd.cluster.Teleport(op, target="gpu-0")
app = nu.With(
nustd.cluster.RayCluster(),
body=remote,
)
...Powered by Ray.
One wire, N providers. Ollama, OpenAI, OpenRouter, Groq, xAI — same call.
LLM chat as a Ref. Swap the model string, keep the code. Local models and hosted APIs meet at the same interface.
- Add intelligence to any Nu app
- 7 providers out of the box
...
class Bot(nu.Service):
chat = nustd.llm.ChatRef.method(temperature=0.7)
# ask the model
op = Bot.chat(prompt="one-line haiku about rust")
app = nu.With(
nustd.llm.ollama(Bot, host="localhost", model="qwen2.5:7b"),
body=op,
)
...Nu is batteries-included and covers the common cases. In-memory state, proxy, HTTP, Python objects, Claude Code, local parallelism — same model, same shape, same primitive as the four above.
Install, run a demo, start hacking.
Python 3.10+ · everything ships in the wheel.
pip install nucore "nustd[all]" nucliEach one boots a live browser dashboard and picks up where it left off on restart. nu demo lists them all.
| counter | sampled |
|---|---|
 A live counter, persistent across restarts. nu demo counter |
 An infinite series, live-sampled into a line-chart. nu demo sampled |
| movies | |
 A movie tracker: form, filterable table, detail pages. nu demo movies |
- Read the docs — tutorials, how-tos, and the fabric reference.
- Browse examples — full source for every demo, plus more programs to steal from.
Batteries included. 26 modules ship on top of the kernel.
Twelve are fabrics. Bind one and every Ref inside the bracket reaches a real system.
The rest re-surface Python's standard library. Call them anywhere, no binding. Same names, same call shape as the stdlib, except a call hands back a tree, not a value. So it composes into the rest of the program.
pip install nucore "nustd[all]" # every backend
pip install nucore "nustd[kv,ui]" # or one extra per fabric| Module | What | Looks like |
|---|---|---|
| nustd.kv | Persistent state. | State.movies.append(m) |
| nustd.ui | Reactive web UI. | Dashboard.count.set_value(n) |
| nustd.cluster | Cluster compute. | Teleport(op, target="gpu") |
| nustd.llm | OpenAI-compatible chat. | Bot.chat(prompt="…") |
| nustd.mem | In-memory state. | users.age.set(12) |
| nustd.proxy | Fabrics over the network. | InvisiblesProxy(Nav, address=...) |
| nustd.http | Nu meets the web. | Solana.get_slot() |
| nustd.service | Python objects as Refs. | Calc.add(a=2, b=3) |
| nustd.cc | Claude Code as a Ref. | Agent.ask(prompt="…") |
| nustd.mp | Local parallel execution. | Teleport(op, target=0) |
| nustd.mp_pool | A pool of workers, as a fabric. | Teleport(body, worker=w) |
| nustd.ws_server | Serve websocket clients. | SessionFor(body=arm) |
| nustd.math | Math functions and constants. | math.sqrt(2) |
| nustd.cmath | complex and its companions. |
cmath.polar(z) |
| nustd.random | The global RNG. | random.randint(1, 6) |
| nustd.time | The process clock. | time.monotonic() |
| nustd.datetime | Dates, times, deltas, timezones. | datetime.date.today() |
| nustd.itertools | Iterator building blocks. | itertools.product(a, b) |
| nustd.functools | A fold over a stream. | functools.reduce(Add, xs) |
| nustd.asyncio | The non-blocking sleep. | asyncio.sleep(1) |
| nustd.logging | Loggers and level shortcuts. | logging.getLogger(__name__) |
| nustd.pathlib | Lexical path operations. | pathlib.Path.of("a", "b") |
| nustd.uuid | UUIDs, all four versions. | uuid.uuid4() |
| nustd.decimal | Exact decimal arithmetic. | Decimal.of("0.1") |
| nustd.fractions | Exact rational arithmetic. | Fraction.of(1, 3) |
| nustd.fin | Nu's own financial types. | Percentage.of(75.5) |
End-user tools written as Nu programs.
| Repo | What |
|---|---|
| nustackdev/nulog | Pure-Python, serverless logger and metrics store. Log and observe metrics from any Python code; entries persist to an embedded KV store and scale to billions, in-process. One line boots a live viewer. |
| nustackdev/nuagent | An AI agent that speaks Nu. The model answers with a program, not a tool call, so one turn reads, branches, loops and writes across real state. |
| nustackdev/nuspace | Nu runtime built on Nu, self-hosted. |
Nu is a reference implementation of the interaction model — a language-agnostic specification of what an interaction is, how Refs name locations, and how Interactions compose into programs.
Add a Nu badge to your README if you're building on Nu:
[](https://github.com/nustackdev/nu)
Considering contributing to Nu? Start by opening an issue or a PR — the codebase is small and readable, and the model is stable enough to build on.
Apache-2.0