Build once. Ship to every chat.
One open-source TypeScript framework to bring your product to Claude, ChatGPT, the terminal, WhatsApp, iMessage, Telegram and your own app. Write your tools and skills once; use them as an MCP server, a plugin, a CLI and a messaging agent.
We're building Flow for a chat-first world: people should be able to use a product by asking for what they need, where they already chat. Moving a booking or placing an order should happen in the conversation—not end with a link to a form. Whether someone texts your business or asks their own assistant, the same product capabilities should be available to them.
Documentation · Quickstart · For coding agents · Website
| Build | Reach |
|---|---|
| MCP server | Claude, ChatGPT and other MCP clients |
| Plugin | Hosts that load native skills and an MCP connection |
| CLI | People, scripts, Claude Code, Codex and other coding agents |
| Messaging agent | WhatsApp, iMessage, Telegram, SMS and your own web or app chat |
Tools are typed TypeScript functions that call your APIs. Skills teach the workflows around them. Flow exposes the same capabilities through each interface, with authentication hooks for your users and room to customize the generated tools, commands and handlers.
In Claude and ChatGPT, the host's model uses your MCP tools. In messaging, Flow runs the conversation with your model, handling double texts, acknowledgements, background tools, channel rules, reminders, persistent history and the agent's own records. Start with whichever interface you need.
Node 22.18 or later. Create a project from the café example:
npx @flow-engineer/flow new my-agent --display-name "My agent"
cd my-agent
npm install
The starter includes the same tools in an MCP server, a CLI and a messaging agent.
Start the server:
npm run mcp
It prints the MCP URL and a command to connect Claude Code. In another terminal, try the CLI:
npm run cli -- --help
npm run cli -- menu --json
To test any MCP server from the current chat, use npx @flow-engineer/flow inspect <url> tools
with the URL the server prints. call, auth, resources and prompts exercise its tools,
sign-in and other capabilities as a host does, without requiring a CLI configuration.
These tool calls need no model key. To reach Claude or ChatGPT remotely, host the MCP server over HTTPS and connect it in the host. MCP and sign-in · Plugin packages
npx @flow-engineer/flow link --channel telegram
npm start
link signs in, sets up the trial keys and prints a phone link. Use --channel whatsapp or
--channel imessage for those platforms when available. Open the playground URL from npm start
to try the agent locally, then text it from your phone while it runs. You can also use your own
model key and messaging provider. Full setup and trial details
flow new includes coding-agent skills and an AGENTS.md pointing to them. Give Claude Code,
Codex or another coding agent your product's codebase and tell it which interfaces to build.
Replace the café tools with calls to your APIs and teach your workflows through skills.
Read the coding-agent guide, or explore the café example.
Check tools, skills and CLI configuration with npx @flow-engineer/flow check. Test the messaging
agent with simulated conversations, inspect traces, and deploy on your own infrastructure or
Flow Cloud. The playground simulators follow each app’s behavior, including channel-specific
controls, media and voice notes; Debug mode shows the underlying platform payloads. Flow Messaging
provides channels through one API; you can also bring your own providers.
Deployment · Self-hosting · Testing · Traces
The documentation site covers the Framework and the
Unified Messaging API. Its source lives in the
private flow-engineer/docs repository. Public behavior changes update the relevant guide there
for people and coding agents; see AGENTS.md.
Tools · Skills · Models and options
In this repository: channel options · patterns that worked (enforce what matters in beforeSend, keep prompts for judgement, render in code, refuse with a reason the model can act on, test a long chat).
A channel's sendMessage resolves when your platform accepted the message and rejects when it
refused it: the agent's next message waits for it, and a rejection reaches the agent as Not
delivered. What is ordered, what is sent once and what send() resolving means:
docs/guarantees.md.
Ready-made beforeSend checks compose with guards(...), the first refusal winning:
oncePerChat(line) (a disclaimer at most once per conversation), noRepeats(),
linkAllowlist(hosts) and noWriteButtons(actions); they read what was sent from the stored
history (context.sent), so they hold after a restart. agent.resetHistory({ to, note }) starts
the history the model is sent again from now (nothing is deleted). Each model call carries at most
24,000 tokens of history, or 60% of the model's contextTokens when that is less
(createAgent({ history: { maxTokens } }) to change it).
What the agent must remember across days and people (a buyer's question waiting for the
seller's answer) it keeps as records: small JSON documents in collections declared on
createAgent({ records }), read by id or matched on a few declared fields, in the same store as its
conversations, so they survive restarts and deploys and work the same in the playground,
self-hosted and on Flow's hosting. Forgetting a person deletes the records that name them, and
flow records export prints them all. The rule: if anything other than the agent reads it, it
belongs in your own database. docs/agents.md
Flow Framework is 0.x: until 1.0 its API (exports, options, file formats, the CLI's commands,
--json fields and exit codes) may change between releases. Every release's notes call out each
breaking change with a migration note saying what to change. The API freezes at 1.0. Pin the exact
version in package.json for production, and read the notes before you move it. What freezes at
1.0: docs/stability.md.