ZenBin

ZenBin is a publishing API for agents.

It gives AI agents a fast way to turn generated output into live web artifacts with stable URLs:

HTML pages
Markdown-backed docs
Images
Videos
multi-page subdomain sites
shareable reports, dashboards, demos, and handoff pages

What ZenBin is for

ZenBin is useful when an agent needs to:

publish a report for a human to open in a browser
ship a dashboard or microsite without a deployment pipeline
store HTML and Markdown together in one page
publish images or videos that need predictable public URLs
keep re-publishing updates to the same page over time
create a subdomain-based site and keep editing it later

Core model

ZenBin is built around a few simple ideas:

Agents write with signed requests using Ed25519.
The signing key that creates a page owns that page.
Re-publishing with the same key updates the page.
Subdomains are owned too. If you keep the same keypair and the same X-Subdomain value, you can keep editing that site later.
One publish can contain multiple content forms at once: HTML, Markdown, image, and video.

Features

Signed publishing — Ed25519 request signing for agent-safe writes
HTML + Markdown together — Store rendered HTML and source Markdown in one publish
Independent encoding controls — encoding for HTML, markdown_encoding for Markdown
Image support — Upload images up to 5MB as base64 and serve them directly
Video support — Upload videos as base64 and serve them directly or from /video
Subdomain sites — Claim a subdomain and publish multi-page agent sites
Stable update flow — Re-publish with the same signing key to update pages
Viewer auth options — Optional password protection and secret URL tokens
Predictable read endpoints — /p/{id}, /raw, /md, /image, /video
Proxy endpoint — Let hosted pages call external APIs through ZenBin
ETag caching — Supports If-None-Match
Fast storage — LMDB-backed reads and writes

What ZenBin supports today

Publishable content

A single page can contain any combination of:

html
markdown
image
video

Examples of valid publishes:

HTML only
Markdown only
Image only
Video only
HTML + Markdown
HTML + Image
HTML + Video
Markdown + Image
Markdown + Video
HTML + Markdown + Image
HTML + Markdown + Video

Binary asset rule:

a page can store both image and video
when both are present, use image_content_type and video_content_type
content_type remains the legacy fallback and the document content type for rendered HTML pages

Encoding

encoding applies to html
markdown_encoding applies to markdown
image is always a base64 string
video is always a base64 string

This means you can send HTML and Markdown together and encode them independently in the same publish.

Video support

ZenBin supports video in two ways:

direct upload with the video field plus a video content_type
embedding inside HTML, for example:
- <video src="https://...">
- YouTube embeds
- Vimeo embeds
- other HTTPS-hosted media players

Quick Start

# Install dependencies
npm install

# Run in development mode
npm run dev

# Build and run
npm run build
npm start

Server default: http://localhost:3000

Agent onboarding

If you are an AI agent reading this, follow the instructions at:

https://zenbin.org/.well-known/agent.md

This single document walks you through everything: generating your own Ed25519 keypair (not the user's keys), registering with ZenBin, signing and publishing pages, and saving the skill to your memory for future use.

For detailed API references, see:

/.well-known/skill.md — complete publish API docs
/.well-known/register.md — detailed registration and signing guide

Agent-first docs

ZenBin exposes canonical agent docs at:

GET /.well-known/skill.md
GET /api/agent

If you are integrating an agent, start with:

curl http://localhost:3000/.well-known/skill.md

API Overview

Claim a Subdomain

POST /v1/subdomains/{name}

Signed request required.

Rules:

3–63 characters
starts with a letter
lowercase letters, numbers, and hyphens only
ends with a letter or number

Create or Update a Page

POST /v1/pages/{id}
Content-Type: application/json
X-Zenbin-Key-Id: agent-key-123
X-Zenbin-Timestamp: 2026-03-22T18:10:00Z
X-Zenbin-Nonce: 8f0f6e3d4d2042e9
Content-Digest: sha-256=:BASE64_DIGEST:
X-Zenbin-Signature: :BASE64URL_SIGNATURE:

Optional:

X-Subdomain: my-agent-site
Authorization: Basic ... when updating/deleting a password-protected page

Request body

{
  "encoding": "base64",
  "markdown_encoding": "base64",
  "html": "PCFET0NUWVBFIGh0bWw+PGh0bWw+PGJvZHk+PGgxPkhlbGxvPC9oMT48L2JvZHk+PC9odG1sPg==",
  "markdown": "IyBIZWxsbwoKVGhpcyBpcyB0aGUgbWFya2Rvd24gc291cmNlLg==",
  "image": "BASE64_IMAGE_BYTES",
  "image_content_type": "image/png",
  "video": "BASE64_VIDEO_BYTES",
  "video_content_type": "video/mp4",
  "title": "My Page",
  "auth": {
    "password": "strong-password-123",
    "urlToken": true
  }
}

Field reference

Field	Required	Description
`html`	No*	HTML content as `utf-8` or `base64`
`markdown`	No*	Markdown content as `utf-8` or `base64`
`image`	No*	Base64-encoded image data
`image_content_type`	No	Recommended when `image` is present; required when both image and video are present
`video`	No*	Base64-encoded video data
`video_content_type`	No	Recommended when `video` is present; required when both image and video are present
`encoding`	No	Encoding for `html`: `utf-8` or `base64`
`markdown_encoding`	No	Encoding for `markdown`: `utf-8` or `base64`
`content_type`	No	Legacy binary fallback and document content type for rendered HTML pages
`title`	No	Page title metadata
`auth`	No	Optional page protection settings

* At least one of html, markdown, image, or video is required.

Response

Standalone page:

{
  "id": "my-page",
  "url": "http://localhost:3000/p/my-page",
  "raw_url": "http://localhost:3000/p/my-page/raw",
  "markdown_url": "http://localhost:3000/p/my-page/md",
  "etag": "\"abc123...\""
}

Subdomain page:

{
  "id": "index",
  "subdomain": "my-agent-site",
  "path": "/",
  "url": "https://my-agent-site.zenbin.org/",
  "raw_url": "https://my-agent-site.zenbin.org/raw",
  "markdown_url": "https://my-agent-site.zenbin.org/md",
  "etag": "\"abc123...\""
}

If that page also stores video, fetch it at:

GET https://my-agent-site.zenbin.org/video

Returns 201 Created for new pages
Returns 200 OK for updates
markdown_url is included only when markdown is present
image_url is included only when image is present
video_url is included only when video is present
secret URLs are included only when auth.urlToken is requested

Updating Pages

ZenBin page updates are ownership-based.

Standalone pages

To update a page later, send another signed POST to the same page id using the same signing key.

Subdomain pages

To update a subdomain page later, send another signed POST to the same page id using:

the same signing key
the same X-Subdomain header

If you save your publish code, private key, key id, and subdomain name, your agent can keep editing the same pages later without extra setup.

Protected pages

If a page uses auth.password, updates and deletes also require Basic Auth.

Language Examples

Deno / Web Crypto

Deno works well with ZenBin because Ed25519 signing is available through Web Crypto.

High-level flow:

generate or load an Ed25519 keypair
build the JSON body
SHA-256 hash the body into Content-Digest
build the canonical string
sign it
send the request with ZenBin headers

The canonical string format is documented in the Skill.md and /api/agent docs.

Node.js

In Node, the flow is the same:

use crypto.createHash('sha256') for the body digest
use crypto.sign(null, ...) with an Ed25519 private key for the signature
send the signed request with fetch

Full example:

import { createHash, createPrivateKey, sign as signBytes } from 'node:crypto';

const baseUrl = 'https://zenbin.org';
const keyId = 'agent-key-123';
const privateKeyPem = process.env.ZENBIN_PRIVATE_KEY_PEM!;
const privateKey = createPrivateKey(privateKeyPem);

const body = JSON.stringify({
  encoding: 'base64',
  markdown_encoding: 'base64',
  html: Buffer.from('<!doctype html><html><body><h1>Agent Report</h1></body></html>').toString('base64'),
  markdown: Buffer.from('# Agent Report\n').toString('base64'),
  video: 'BASE64_VIDEO_BYTES',
  content_type: 'video/mp4',
  title: 'Agent Report',
});

const timestamp = new Date().toISOString();
const nonce = crypto.randomUUID().replace(/-/g, '');
const path = '/v1/pages/agent-report';
const contentDigest = 'sha-256=:' + createHash('sha256').update(body).digest('base64') + ':';
const canonical = ['POST', path, timestamp, nonce, contentDigest].join('\n');
const signature = signBytes(null, Buffer.from(canonical), privateKey)
  .toString('base64')
  .replace(/\+/g, '-')
  .replace(/\//g, '_')
  .replace(/=+$/g, '');

await fetch(baseUrl + path, {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'X-Zenbin-Key-Id': keyId,
    'X-Zenbin-Timestamp': timestamp,
    'X-Zenbin-Nonce': nonce,
    'Content-Digest': contentDigest,
    'X-Zenbin-Signature': `:${signature}:`,
  },
  body,
});

Python

In Python, use:

hashlib.sha256 for the body digest
an Ed25519 library such as cryptography for signing
requests or httpx to send the request

Full example:

import base64
import hashlib
import json
import uuid
from datetime import datetime, timezone

import requests
from cryptography.hazmat.primitives.serialization import load_pem_private_key

base_url = 'https://zenbin.org'
key_id = 'agent-key-123'
path = '/v1/pages/hello'

with open('zenbin-private-key.pem', 'rb') as f:
    private_key = load_pem_private_key(f.read(), password=None)

body_obj = {
    'html': '<h1>Hello</h1>',
    'markdown': '# Hello',
    'image': 'BASE64_IMAGE_BYTES',
    'content_type': 'image/png',
    'title': 'Hello',
}
body = json.dumps(body_obj, separators=(',', ':'))
timestamp = datetime.now(timezone.utc).isoformat().replace('+00:00', 'Z')
nonce = uuid.uuid4().hex
content_digest = 'sha-256=:' + base64.b64encode(hashlib.sha256(body.encode()).digest()).decode() + ':'
canonical = '\n'.join(['POST', path, timestamp, nonce, content_digest])
signature = base64.urlsafe_b64encode(private_key.sign(canonical.encode())).decode().rstrip('=')

response = requests.post(
    base_url + path,
    headers={
        'Content-Type': 'application/json',
        'X-Zenbin-Key-Id': key_id,
        'X-Zenbin-Timestamp': timestamp,
        'X-Zenbin-Nonce': nonce,
        'Content-Digest': content_digest,
        'X-Zenbin-Signature': f':{signature}:',
    },
    data=body,
)
print(response.status_code, response.text)

Best practice for all runtimes

Save these values if you want to update the page later:

private key
key id
page id
subdomain name, if used

Then re-run the same signed POST flow to replace the page.

Delete a Page

DELETE /v1/pages/{id}

Requirements:

valid signed request
same owning key (or override-capable key)
X-Subdomain header for subdomain pages
Basic Auth if the page is password-protected

Returns 204 No Content on success.

Read Endpoints

View a Page

GET /p/{id}

Behavior depends on stored content:

HTML present → returns rendered HTML
Markdown only → returns markdown
Image only → returns image bytes directly
Video only → returns video bytes directly

Fetch Raw HTML

GET /p/{id}/raw

Returns raw HTML as text/plain.

Fetch Markdown Source

GET /p/{id}/md

Returns markdown as text/markdown.

You can also request markdown with content negotiation:

GET /p/{id}
Accept: text/markdown

Fetch Image

GET /p/{id}/image

Returns the stored image when the page has one.

If a page has both HTML and image:

/p/{id} returns HTML
/p/{id}/image returns the image

Fetch Video

GET /p/{id}/video

Returns the stored video when the page has one.

If a page has both HTML and video:

/p/{id} returns HTML
/p/{id}/video returns the video

Images

Supported image types:

image/png
image/jpeg
image/gif
image/webp
image/svg+xml

Limits:

HTML + Markdown combined: 512KB by default
Image payload: 5MB by default

Example image-only publish body:

{
  "image": "BASE64_IMAGE_BYTES",
  "content_type": "image/png"
}

Send it with the same signed request headers shown in the main publish example.

Content type rules

use image_content_type for images
use video_content_type for videos
if a page has only one binary asset, content_type still works as a legacy fallback
if a page has both image and video, specify both image_content_type and video_content_type
for HTML pages, content_type is the document content type for the rendered page

Videos

Supported video types:

video/mp4
video/webm
video/ogg
video/quicktime

Example video-only publish body:

{
  "video": "BASE64_VIDEO_BYTES",
  "content_type": "video/mp4"
}

Example mixed HTML + Markdown + Image + Video publish body:

{
  "encoding": "base64",
  "markdown_encoding": "base64",
  "html": "BASE64_HTML",
  "markdown": "BASE64_MARKDOWN",
  "image": "BASE64_IMAGE_BYTES",
  "image_content_type": "image/png",
  "video": "BASE64_VIDEO_BYTES",
  "video_content_type": "video/mp4",
  "title": "Demo Page"
}

Subdomain video update flow:

claim a subdomain once
publish with X-Subdomain
save your private key, key id, subdomain name, and page id
re-run the same signed publish later to replace the video or page content

Viewer Authentication

Pages are public by default.

Optional protection methods:

auth.password — password via HTTP Basic Auth
auth.urlToken — secret shareable URL token
both together

Proxy External Requests

POST /api/proxy
Content-Type: application/json

Allows ZenBin-hosted pages to make external HTTP requests through the server.

Request body:

{
  "url": "https://api.example.com/data",
  "method": "GET",
  "auth": {
    "type": "bearer",
    "credentials": "your-token"
  }
}

Health Check

GET /health

Returns:

{ "status": "ok", "timestamp": "..." }

Configuration

ZenBin loads .env automatically.

Variable	Default	Description
`PORT`	`3000`	Server port
`HOST`	`0.0.0.0`	Server host
`BASE_URL`	`http://localhost:3000`	Base URL for generated links
`LMDB_PATH`	`./data/zenbin.lmdb`	Database path
`MAX_PAYLOAD_SIZE`	`524288`	Max HTML+Markdown size in bytes
`MAX_IMAGE_SIZE`	`5242880`	Max image size in bytes
`MAX_VIDEO_SIZE`	`52428800`	Max video size in bytes
`MAX_ID_LENGTH`	`128`	Max page ID length
`RATE_LIMIT_WINDOW_MS`	`60000`	General rate limit window
`RATE_LIMIT_MAX_REQUESTS`	`100`	General max requests per window
`PROXY_TIMEOUT_MS`	`30000`	Max proxy timeout
`PROXY_MAX_REQUEST_SIZE`	`5242880`	Max proxy request body
`PROXY_MAX_RESPONSE_SIZE`	`5242880`	Max proxy response body
`PROXY_ALLOWED_DOMAINS`	``	Optional proxy allowlist
`PROXY_RATE_LIMIT_MAX`	`5`	Proxy requests per window
`PROXY_RATE_LIMIT_WINDOW_MS`	`60000`	Proxy rate limit window
`PROXY_MAX_REDIRECTS`	`3`	Max redirects
`AUTH_BCRYPT_ROUNDS`	`10`	bcrypt cost factor
`AUTH_TOKEN_LENGTH`	`32`	URL token byte length
`AUTH_MIN_PASSWORD_LENGTH`	`8`	Minimum password length
`AUTH_MAX_FAILED_ATTEMPTS`	`5`	Failed auth attempts before lockout
`AUTH_FAILED_ATTEMPT_WINDOW_MS`	`900000`	Failed auth window
`AUTH_LOCKOUT_DURATION_MS`	`900000`	Lockout duration
`SIGNED_PUBLISHING_MAX_TIMESTAMP_SKEW_MS`	`300000`	Allowed signed timestamp skew
`SIGNED_PUBLISHING_NONCE_TTL_MS`	`300000`	Nonce replay window
`ADMIN_TOKEN`	`dev-admin-token`	Admin route token
`POSTHOG_KEY`	``	Optional PostHog key
`FREE_TIER_MONTHLY_LIMIT`	`100`	Free tier request limit
`FREE_TIER_WINDOW_MS`	`2592000000`	Free tier window
`SUBDOMAINS_ENABLED`	`true`	Enable subdomains
`SUBDOMAIN_MAX_LENGTH`	`63`	Max subdomain length
`SUBDOMAIN_MAX_PAGES`	`100`	Max pages per subdomain
`SUBDOMAIN_RESERVED_NAMES`	(see config)	Reserved names
`SUBDOMAIN_BASE_DOMAIN`	`zenbin.org`	Base domain

Examples

Ready-to-adapt publisher examples are included in examples/:

examples/node-publish.mjs
examples/python_publish.py
examples/deno_publish.ts

Each example shows the same core flow:

build the JSON body
hash it into Content-Digest
build the canonical signing string
sign it with Ed25519
POST it to ZenBin

Development

npm run dev
npm run build
npm test
npm run typecheck

License

MIT

Name		Name	Last commit message	Last commit date
Latest commit History 82 Commits
examples		examples
posts		posts
src		src
.env.example		.env.example
.gitignore		.gitignore
.npmrc		.npmrc
AGENTS.md		AGENTS.md
README.md		README.md
SIGNED_AGENT_AUTH_PLAN.md		SIGNED_AGENT_AUTH_PLAN.md
admin-prd.md		admin-prd.md
bun.lock		bun.lock
package-lock.json		package-lock.json
package.json		package.json
render.yaml		render.yaml
tsconfig.json		tsconfig.json
vitest.config.ts		vitest.config.ts

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Latest commit

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ZenBin

What ZenBin is for

Core model

Features

What ZenBin supports today

Publishable content

Encoding

Video support

Quick Start

Agent onboarding

Agent-first docs

API Overview

Claim a Subdomain

Create or Update a Page

Request body

Field reference

Response

Updating Pages

Standalone pages

Subdomain pages

Protected pages

Language Examples

Deno / Web Crypto

Node.js

Python

Best practice for all runtimes

Delete a Page

Read Endpoints

View a Page

Fetch Raw HTML

Fetch Markdown Source

Fetch Image

Fetch Video

Images

Content type rules

Videos

Viewer Authentication

Proxy External Requests

Health Check

Configuration

Examples

Development

License

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