The backend and the page.
One file.

guestbook.pyxl · 33 lines · Python 3.10+ · React 18/19

Working copyv0.9.4 · PyPI · MITruns as printed

1· loader runs on the server

2· its return value is the page’s props

3· HTML arrives finished, then hydrates

4· the button calls Python in the same file

pages/guestbook.pyxl33 lines

1from pydantic import BaseModel2import db34class Entry(BaseModel):5    name: str6    note: str78@server9async def load(request):10    return {"entries": await db.recent(10)}1112@action13async def sign(request, body: Entry):14    await db.add(body.name, body.note)15    return {"entries": await db.recent(10)}16# ← the API layer (one blank line)17export default function Guestbook({ data }) {export default function Guestbook(  { data }) {18  const [entries, setEntries] = useState(data.entries)  const [entries, setEntries] =    useState(data.entries)19  const sign = useAction('sign')20  const submit = async (e) => {21    e.preventDefault()22    const form = Object.fromEntries(new FormData(e.target))    const form = Object.fromEntries(      new FormData(e.target))23    const r = await sign(form)24    if (r.ok) setEntries(r.entries)25  }26  return <form onSubmit={submit}>27    <ul>{entries.map(e =>28      <li key={e.id}><b>{e.name}</b> {e.note}</li>)}</ul>      <li key={e.id}>        <b>{e.name}</b> {e.note}</li>)}</ul>29    <input name="name" placeholder="name" />30    <input name="note" placeholder="note" />31    <button>Sign</button>32  </form>33}

1· loader runs on the server — line 9
2· its return value is the page’s props — line 10
3· HTML arrives finished, then hydrates — line 17
4· the button calls Python in the same file — line 19

localhost:8000dev

Guestbook

mira says hi from a FastAPI shop
deno_fan fine, this is neat
sam shipped before my coffee cooled

sign it — watch the file run

seed entries are authored · yours are real — stored by this server, shown only to your browser

request log

GET/200—← HTML, finished

LOADload_home()200<0.1 ms← {"entries": […]}

Open the playground →

runs .pyxl files in your browser · CPython via Pyodide · ~12 MB once

02 · Request

One request, start to finish.

what the server does, in order — no magic left in the margin

FIG 01

pyxle

GET /load(request)propsserver sidebrowser sideHTMLhydrate()

conventional

routeserializefetchparserender

the same request, with and without an API layer.

03 · Framework

A whole framework, not a trick.

six of 64 documented pages — every cell links to its docs

Routing

pages/
├── index.pyxl          → /
├── layout.pyxl         → wraps children
└── posts/
   └── [slug].pyxl      → /posts/:slug

Files are routes. Brackets are params.

docs →/docs/core-concepts/routing

Streaming SSR

<h1>{data.title}</h1>  {/* shell */}

<Suspense fallback={<p>Loading…</p>}>
  <ActivityFeed />  {/* streams in */}
</Suspense>

HTML streams while Python awaits.

docs →/docs/guides/streaming

Validated actions

@action
async def sign(request, body: Entry): …

// bad input — 422, action never ran
{"ok": false,
 "error": "Validation failed",
 "fields": {"note": ["Field required"]}}

The hero’s Entry model, failing honestly: per-field errors, typed.

docs →/docs/core-concepts/server-actions

Realtime

async with channel(
        ws, f"room:{room}") as live:
    async for text in ws.iter_text():
        await live.publish(text)

const { send } = useWebSocket(
  '/chat/' + room, { onMessage })

The page serves its own WebSocket. Abridged from examples/chat.

docs →/docs/guides/websockets

Auth pluginpyxle-auth 0.4

const { user, isAuthenticated,
        logout } = useAuth()

if (!isAuthenticated)
  return <a href="/login">Sign in</a>

Sliding sessions in HttpOnly cookies; request.user on every loader.

docs →/docs/plugins/pyxle-auth

Studio & debugger

Pyxle Studio at /__pyxle/studio — route table of a scaffolded app

Routes, requests, metrics — and breakpoints in .pyxl files.

docs →/docs/guides/studio

04 · Numbers

Numbers we can defend.

every figure carries its own test conditions

~2.2×

median per-core SSR throughput vs Next.js

measured July 2026 on Pyxle 0.7.1 · normalized, Next.js = 1.0 · full harness → /benchmarks

FastAPI
parity

raw JSON endpoints

same harness, July 2026 · Pyxle is Starlette underneath

documentation pages, in the repo

counted from the docs manifest at load · /docs

apps we run in production

all three below ↓ · click them

05 · Production

Demos, running in production.

click them — they are not screenshots of screenshots

pyxle.dev — this site's homepage, served by Pyxle

This site livepyxle.devThe page you are reading. Every route here is a .pyxl file — the hero’s guestbook is a live @action, and the footer links each page’s source.

source →

Today livetoday.pyxle.appSessions via pyxle-auth.

visit → source →

Pulse livepulse.pyxle.appDB-backed pages, prerendered.

visit → source →

Open source. MIT. Self-hosted. No cloud tax.

There is no logo wall here — Pyxle is weeks past 0.9. What exists is running software: these apps, a playground, 64 pages of docs, and the framework’s source. Kick the tires.

github.com/pyxle-dev/pyxle · ★ 10 · MIT

06 · Start

Three commands to a running app.

the terminal on the right replays a real captured session

Docs Playground GitHub

terminal

$ pip install pyxle-framework
Successfully installed pyxle-framework-0.9.3
  pyxle-langkit-0.3.5 starlette-1.3.1 uvicorn-0.51.0 …
$ pyxle init app
▶️  Creating project — app
✅ Project scaffolded at app
$ cd app && pyxle dev
ℹ️  node_modules/ not found — running 'npm install'
✅ npm install completed
✅ Pyxle dev server ready in 1559 ms
ℹ️    Local:   http://127.0.0.1:8000
ℹ️    Studio:  http://127.0.0.1:8000/__pyxle/studio

output abridged · pyxle 0.9.3 · captured 2026-09-03

The backend and the page.One file.