Sendmux SDKs

Official SDK, CLI, and MCP workspace for Sendmux.

• Product documentation: sendmux.ai/docs
• Management API reference: sendmux.ai/docs/api/introduction
• Mailbox API reference: sendmux.ai/docs/mailbox-api/introduction
• Sending API reference: sendmux.ai/docs/sending-api/introduction
• MCP guide: sendmux.ai/docs/guides/mcp

Packages

Ecosystem	Package	Surface	API key or auth	Install	Source
npm	@sendmux/core	Shared TypeScript helpers	n/a	npm install @sendmux/core	packages/ts/core
npm	@sendmux/sending	Sending API	smx_mbx_* or owner-approved smx_agent_*	npm install @sendmux/sending	packages/ts/sending
npm	@sendmux/mailbox	Mailbox API	smx_mbx_* or smx_agent_*	npm install @sendmux/mailbox	packages/ts/mailbox
npm	@sendmux/management	Management API	smx_root_*	npm install @sendmux/management	packages/ts/management
npm	@sendmux/sdk	TypeScript umbrella package	surface-specific	npm install @sendmux/sdk	packages/ts/sdk
npm	@sendmux/cli	sendmux CLI	command/profile-specific	npm install -g @sendmux/cli	packages/ts/cli
Homebrew	sendmux	sendmux CLI	command/profile-specific	brew install sendmux/tap/sendmux	Sendmux/homebrew-tap
PyPI	sendmux-core	Shared Python helpers	n/a	pip install sendmux-core	packages/python/core
PyPI	sendmux-sending	Sending API	smx_mbx_* or owner-approved smx_agent_*	pip install sendmux-sending	packages/python/sending
PyPI	sendmux-mailbox	Mailbox API	smx_mbx_* or smx_agent_*	pip install sendmux-mailbox	packages/python/mailbox
PyPI	sendmux-management	Management API	smx_root_*	pip install sendmux-management	packages/python/management
PyPI	sendmux-sdk	Python umbrella package	surface-specific	pip install sendmux-sdk	packages/python/sdk
PyPI	sendmux-mcp	Local, self-hosted, and hosted MCP servers	OAuth for hosted; surface-specific keys for local	pip install sendmux-mcp	packages/python/mcp
Go	sendmux.ai/go/core	Shared Go helpers	n/a	go get sendmux.ai/go@v1.0.0	go/core
Go	sendmux.ai/go/sending	Sending API	smx_mbx_* or owner-approved smx_agent_*	go get sendmux.ai/go@v1.0.0	go/sending
Go	sendmux.ai/go/mailbox	Mailbox API	smx_mbx_* or smx_agent_*	go get sendmux.ai/go@v1.0.0	go/mailbox
Go	sendmux.ai/go/management	Management API	smx_root_*	go get sendmux.ai/go@v1.0.0	go/management
Go	sendmux.ai/go/sdk	Go umbrella package	surface-specific	go get sendmux.ai/go@v1.0.0	go/sdk
crates.io	sendmux	Rust umbrella crate	surface-specific	cargo add sendmux	rust
Packagist	sendmux/core	Shared PHP helpers	n/a	composer require sendmux/core:^1.0	packages/php/core
Packagist	sendmux/sending	Sending API	smx_mbx_* or owner-approved smx_agent_*	composer require sendmux/sending:^1.0	packages/php/sending
Packagist	sendmux/mailbox	Mailbox API	smx_mbx_* or smx_agent_*	composer require sendmux/mailbox:^1.0	packages/php/mailbox
Packagist	sendmux/management	Management API	smx_root_*	composer require sendmux/management:^1.0	packages/php/management
Packagist	sendmux/sdk	PHP umbrella package	surface-specific	composer require sendmux/sdk:^1.0	packages/php/sdk
RubyGems	sendmux-core	Shared Ruby helpers	n/a	gem install sendmux-core	packages/ruby/core
RubyGems	sendmux-sending	Sending API	smx_mbx_* or owner-approved smx_agent_*	gem install sendmux-sending	packages/ruby/sending
RubyGems	sendmux-mailbox	Mailbox API	smx_mbx_* or smx_agent_*	gem install sendmux-mailbox	packages/ruby/mailbox
RubyGems	sendmux-management	Management API	smx_root_*	gem install sendmux-management	packages/ruby/management
RubyGems	sendmux-sdk	Ruby umbrella package	surface-specific	gem install sendmux-sdk	packages/ruby/sdk

Quick start

Install only the package for the surface you need.

npm install @sendmux/sending
pip install sendmux-sending
go get sendmux.ai/go@v1.0.0
cargo add sendmux
composer require sendmux/sending:^1.0
gem install sendmux-sending

Use send-capable smx_mbx_* keys or owner-approved Sending-resource smx_agent_* tokens for Sending clients. Use smx_mbx_* keys or scoped smx_agent_* tokens for Mailbox clients. Use root smx_root_* keys for Management clients. Agent tokens remain limited by server-side scopes; pre-claim self-registered agent tokens do not include email.send.

For command-line access, install the CLI:

brew install sendmux/tap/sendmux
npm install -g @sendmux/cli
sendmux --help

For MCP clients, install sendmux-mcp or connect to the hosted MCP endpoint:

pip install sendmux-mcp
sendmux-mcp-mailbox --help

The hosted MCP endpoint is https://mcp.sendmux.ai/mcp. Local MCP commands support stdio and HTTP transports; hosted MCP uses OAuth and does not require manual API keys or custom OAuth endpoints.

Attachments And Live Mailbox Events

Mailbox attachment metadata now includes a short-lived download_url. Fetch that URL promptly with a plain HTTP client; it does not require an Authorization header, but it expires after a short TTL. If a download URL expires, re-fetch the message or attachment metadata to receive a fresh URL.

For outbound files, avoid manually placing base64 in prompts or source strings. Use the zero-context path for your lane:

• CLI: sendmux mailbox:send-message --attach ./report.pdf or sendmux sending:send --attach ./report.pdf.
• TypeScript: use @sendmux/mailbox/node sendMailboxMessageWithFiles(...) or @sendmux/sending/node sendEmailWithFiles(...).
• Python: use sendmux_mailbox.send_mailbox_message_with_files(...) or sendmux_sending.send_email_with_files(...).
• MCP: local stdio can use mailbox_upload_attachment with file_path; hosted and shell-capable agents can mint a presigned upload URL, PUT bytes to it without an API key, then send with the returned blob_id.

Mailbox direct uploads, presigned uploads, CLI --attach, and mailbox SDK file helpers share the mailbox attachment cap: currently 7,500,000 bytes per attachment. Sending API attachment helpers encode files into the send request body; the generated Sending API limit is max 10 attachments and a 25 MB request body.

Small generated attachments can still use inline base64 where the API schema supports them. MCP inline base64 is capped at 32 KiB decoded; the cheaper alternatives are file_path, presigned upload, CLI --attach, and SDK file helpers.

Live mailbox events are available through idiomatic lanes:

• TypeScript: streamMailboxEvents(...) returns an async iterator over typed mailbox realtime events.
• Python: iter_mailbox_events(...) yields typed MailboxRealtimeEvent models from the generated mailbox client.
• CLI: sendmux mailbox:stream-events --follow prints one JSON event per line until the stream closes or the process is interrupted.
• MCP: use mailbox_wait_for_message for bounded waits inside agent tool calls, then mailbox_get_attachment to renew attachment metadata and fetch download_url.

Repository structure

Path	Purpose
packages/ts	TypeScript SDK packages and the sendmux CLI.
packages/python	Python SDK packages and the sendmux-mcp package.
go	Go module sendmux.ai/go and subpackages.
rust	Rust crate published as sendmux on crates.io.
packages/php	PHP package sources used for Packagist packages and public split repositories.
packages/ruby	RubyGem package sources.
codegen	Generator configuration and templates.
scripts	Generation, verification, publishing, and release helper scripts.
docs	Surface-coverage and live E2E audit artefacts.
.github/workflows	CI, canary, live E2E, and release workflows.

Versioning and support

SDK packages track the Sendmux public API contracts. Patch versions can differ between packages when a fix only affects one ecosystem or runtime.

Generated clients are built from committed OpenAPI snapshots. Any API contract change must update the snapshots and generated output in the same change.

For help, open a GitHub issue with the package name, version, command or import path, and the request ID from any API error response.

Contributing

Open pull requests against this repository. Keep generated output, source snapshots, and verification artefacts together in the same change.

Security issues should be reported through GitHub Security Advisories.

Licence

This repository is available under the MIT licence.