handshake-prompt (Python Server SDK)

Core network component for the Handshake Prompt Protocol (HPP) — session pairing, token auth, HTTP + WebSocket transport.

Architecture

┌─────────────────────────────────────────┐
│  Application (your service)           │
│  form-fill UI, device pairing, etc.     │
└──────────────────┬──────────────────────┘
                   │ hooks + mode handlers
┌──────────────────▼──────────────────────┐
│  handshake_prompt (this package)        │
│  ProtocolEngine · Session · SessionStore│
│  auth · Flask adapter (HandshakeManager)│
└──────────────────┬──────────────────────┘
                   │
         HTTP / WebSocket + X-Handshake-Token

Core transport (always included):

• Session creation with 128-bit sid + 192-bit token
• Token auth on all Agent endpoints
• Rate limiting, TTL, dynamic extension
• WebSocket real-time push

Application plugins (optional, in handshake_prompt.modes):

• form-fill — schema validation, field ownership, missing-field detection
• default — opaque key/value context for generic Agent interactions

Prompt text generation is not part of the core transport — use handshake_prompt.prompt.build_prompt() if you want a default template.

Install

pip install handshake-prompt

Quick start (Flask)

from flask import Flask
from flask_sock import Sock
from handshake_prompt import HandshakeManager

app  = Flask(__name__)
sock = Sock(app)
hm   = HandshakeManager(app, sock)   # HPP endpoints mounted

if __name__ == '__main__':
    app.run(port=5000)

Endpoints (default prefix /handshake):

Using without Flask

from handshake_prompt import ProtocolEngine, SessionStore

store = SessionStore()
engine = ProtocolEngine(store=store, prefix='/api/pair')

payload, code = engine.create_session({'mode': 'device-pair', 'data': {}})
# Wire payload/code into your own framework adapter

Form-fill mode (optional plugin)

{
  "mode": "form-fill",
  "schema": [
    {"key": "name", "label": "Name", "type": "string", "required": true}
  ],
  "context": {}
}

Custom mode handler

from handshake_prompt.modes import DEFAULT_HANDLERS

class MyHandler:
    def setup_session(self, sess, body): ...
    def context_response(self, sess): ...
    def process_actions(self, sess, actions, stream, interval, cbs, broadcast): ...
    def process_notify(self, sess, key, value): ...
    def process_ws_message(self, sess, msg): ...

hm = HandshakeManager(app, sock, mode_handlers={
    **DEFAULT_HANDLERS,
    'my-mode': MyHandler(),
})

Hooks

@hm.on_create_session
def bind_owner(sess, request):
    sess.owner = flask_session.get('user_id')

@hm.on_action
def audit(sess, action, request):
    return True  # return False to veto

@hm.on_extend
def cap_extension(sess, extra_seconds, request):
    return min(extra_seconds, 1800)

Security defaults

• Token: 192-bit entropy, timing-safe comparison
• Session ID: 128-bit entropy
• TTL: 30 min default, dynamically extendable
• Rate limit: 60 req/min/session
• WebSocket: token verified at connect time

See SPEC.md for full protocol details.

License

MIT