Engineering

Your AI agent already knows how to use a terminal. Why CLIs beat MCP servers

LLMs already know how to use a terminal. We maintain both an MCP server and a CLI at Courier, and the difference tells you something about where AI tooling is heading.

EU Data Residency for Notifications: What Engineering Teams Need to Know

Courier supports EU data residency through a dedicated datacenter in AWS EU-West-1 (Ireland), with full API feature parity, same-workspace dual-region access, built-in GDPR deletion endpoints, and localization support for multilingual notifications. Engineering teams can switch to EU hosting by changing a single base URL with no workspace migration or downtime required.

Expo Push Notifications: The Complete Implementation Guide (SDK 52+)

Expo push notifications are alerts sent from a server to a user's phone, even when the app isn't open. To set them up, install the expo-notifications library, ask the user for permission, and get a unique push token for their device. Your server sends a message to Expo's push service with that token, and Expo delivers it through Apple or Google. Push notifications only work on real phones, not simulators. Local notifications are different — they're scheduled by the app itself for things like reminders. You can also route Expo push through services like Courier to add email, SMS, and Slack fallbacks.

Best Email API Providers for Developers in 2026: SendGrid vs Postmark vs Mailgun vs SES vs Resend

Your email provider sticks with you longer than most technical decisions. Courier handles notification infrastructure for thousands of teams, so we went deep on the six email providers that show up most: SendGrid, Postmark, Mailgun, Amazon SES, Resend, and SMTP. This guide covers real API primitives, actual code from each provider's docs, Courier integration examples with provider overrides, and an honest read on where each developer experience holds up and where it breaks down. We also asked Claude to review every API and tell us which one it would wire up first. The answer surprised us.

The Courier MCP Server Is Open Source. Here's How It Actually Works.

Courier's MCP server is open source at github.com/trycourier/courier-mcp. It connects AI coding tools like Cursor and Claude Code to your Courier account so they can send messages, manage users, and install SDKs without hallucinating API details. This post walks through the actual codebase: how 16 tool classes are registered (and how a config allowlist gates most of them), why we pull installation guides from GitHub at runtime instead of bundling them, how the DocsTools class generates live JWTs alongside setup instructions, and what the SdkContextTools class does in the repo to prevent v7/v8 SDK conflicts (even though it isn't wired into the server yet).

Cross-Channel Notification State: Why Read Receipts Are Harder Than They Look

When a user opens your email, does your app know? For most products, the answer is no. Each channel tracks its own state. Email has read receipts. Push has delivery confirmation. In-app has its own unread count. They don't talk to each other. Users notice. This guide covers the three approaches to notification state management (channel-first, central-first, event-first), when to use each, and how to implement cross-channel sync without overengineering. Includes state diagrams and practical implementation patterns.

Terminal-First Development vs. IDE: Building Notification Infrastructure with Claude Code and Cursor

AI coding tools split into two camps: terminal agents (Claude Code) and IDE-augmented editors (Cursor). This guide compares both approaches using Courier's CLI and MCP server as the test case. Covers installation, configuration, and practical workflows for building multi-channel notifications. Includes code examples for user management, bulk operations, and automation triggers. Also explores agent-to-agent communication patterns where AI systems need notification infrastructure to coordinate tasks and escalate to humans.

The Notification Platform Developers Choose

Most notification platforms built dashboards first and added developer tools later. Courier did the opposite. With a CLI that handles real workflows, MCP integration with setup management, typed SDKs in seven languages, and SOC 2 Type 2 certification, Courier is built for teams that ship. This isn't marketing copy: Twilio chose Courier to unify notifications across their 10M+ developer platform. LaunchDarkly uses Courier to power feature release workflows. When the companies that build developer infrastructure choose your notification platform, that says something about the technical foundation.

Vibe Coding Notifications: How to Use Courier with Cursor or Claude Code

Courier's MCP server lets AI coding tools like Cursor and Claude Code interact directly with your notification infrastructure. Unlike Knock and Novu's MCP servers that focus on API operations, Courier's includes embedded installation guides for Node, Python, Flutter, React, and other platforms. When you prompt "add Courier to my app," your AI assistant pulls accurate setup instructions rather than relying on outdated training data. OneSignal's MCP is community-maintained, not official. Courier supports 50+ providers, native Slack/Teams integration, drop-in inbox and preference components, and a free tier of 10,000 notifications/month. Configure in Cursor with "url": "https://mcp.courier.com" and "headers": { "api_key": "YOUR_KEY" }.