MCP Notifications Feature Support

[david-martin]

Summary

This is a Feature tracking MCP notification-related capabilities in the gateway.

Design Document

See docs/design/notifications.md for the architecture and design decisions.

Already Implemented

• State change event notifications (broadcast)
  • notifications/tools/list_changed
  • notifications/resources/list_changed
  • notifications/prompts/list_changed
  • notifications/roots/list_changed
• Progress updates for long-running tool calls
• Persistent broker connections to backend MCP servers

Dependency Graph

#598 (Design doc update)
    │
    ▼
#599 (Per-client notifications infrastructure)
    │
    ├──▶ #407 (MCP Logging)
    │
    └──▶ #597 (Resource subscriptions)

#349 (Elicitations) - independent, in progress

#422 (Cancellations) - needs design review

Related Testing

• Test for multiple long-running tools at the same time (e.g. server1 slow) to make sure notifications arrive at the client without being buffered #371 - Test for multiple long-running tools notifications (sub-issue of Improve test coverage #326)

References

• MCP Architecture - Notifications
• MCP Logging Specification
• MCP Elicitation Specification
• MCP Cancellation Specification