mcp-hmr v0.0.3

What's Changes

• Support for multiple transport protocols: --transport / -t flag allows choosing between stdio, http, sse, streamable-http
• New CLI options for Streamable HTTP transport configuration: --host, --port, --path
• Programmatic API: mcp_server(target) context manager enables using mcp-hmr without CLI, allowing custom middleware and server extensions

Features ✨

CLI Enhancements

The CLI now supports all transport protocols available in fastmcp run, making it a true drop-in replacement:

# Use streamable-http transport
mcp-hmr main:app -t streamable-http --port 8000

# Custom host and port
mcp-hmr main:app -t http --host 0.0.0.0 --port 3000

Programmatic API

You can now integrate mcp-hmr directly in your code to add custom functionality:

from mcp_hmr import mcp_server

async with mcp_server("main.py:mcp") as mcp:
    # Add middleware, configure settings, etc.
    # mcp.add_middleware(...)
    await mcp.run_async()  # runs with hot-reloading enabled ✨

This is useful when you want to extend your server with additional features like CORS middleware while maintaining HMR capabilities.

Important

For the programmatic API to work correctly with HMR, ensure that the target module has not been imported yet when calling mcp_server(target). Otherwise, hot-reloading won't take effect.

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Tip

As a reminder, mcp-hmr provides Hot Module Reloading for MCP/FastMCP servers.

It acts as a drop-in replacement for mcp run or fastmcp run. Both FastMCP v2 and the official python SDK are supported.

Under the hood, we use FastMCP.mount to hot swap the underlying fastmcp.FastMCP / mcp.server.FastMCP instances, providing fine-grained on-demand hot-reloading DX for your local MCP Server development.

Full Changelog: mcp-hmr/v0.0.2...mcp-hmr/v0.0.3

mcp-hmr v0.0.2

API Changes

• 0438f6c now both mcp-hmr path/to/file.py:app (new) and mcp-hmr module:app target is supported
• fad2b48 now support --log-level

Internal Changes

• 38f4318 safer task management via TaskGroup

Full Changelog: mcp-hmr/v0.0.1...mcp-hmr/v0.0.2

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Tip

As a reminder, mcp-hmr provides Hot Module Reloading for MCP/FastMCP servers.

It acts as a drop-in replacement for mcp run or fastmcp run. Both FastMCP v2 and the official python SDK are supported.

Under the hood, we uses FastMCP.mount to hot swap the underlying fastmcp.FastMCP / mcp.server.FastMCP instances, providing fine-grained on-demand hot-reloading DX for your local MCP Server development.

Demo

mcp-inspector-demo.mov

Hot Reload your MCP Server ✨

mcp-hmr

Provides Hot Module Reloading for MCP/FastMCP servers.

It acts as a drop-in replacement for mcp run or fastmcp run. Both FastMCP v2 and the official python SDK are supported.

Usage

If your server instance is named app in path/to/main.py, you can run:

mcp-hmr path.to.main:app

Which will be equivalent to the following code but with HMR enabled:

from path.to.main import app

app.run("stdio")

Now, whenever you save changes to your source code, the server will automatically reload without dropping the connection to the client.

Details

This integration uses FastMCP.mount to hot swap the underlying fastmcp.FastMCP / mcp.server.fastmcp.FastMCP instances, providing fine-grained on-demand hot-reloading DX for your local MCP Server development.

Currently only stdio transport is supported. But since the uvicorn-hmr integration already exists for a while, that won't be hard.

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Full Changelog: see PR #39