Real-time ActivityPub debug dashboard

[dahlia]

A debug dashboard that shows all ActivityPub activities being sent and received in real-time would greatly improve the developer experience when building federated applications with Fedify.

Proposed features

• Real-time monitoring of inbound/outbound activities
• Filtering by activity type, sender, receiver
• Detailed inspection of JSON-LD content and HTTP headers
• Signature verification details (HTTP Signatures, LD Signatures, Object Integrity Proofs)
• Retry queue management for failed deliveries

Implementation options

1. Embedded web dashboard (accessible at a debug endpoint)
2. Browser extension/developer tools integration
3. Enhanced logging visualization

Questions

• Should this be development-only or configurable for production use?
• How should we handle potentially sensitive information?
• Are there specific debugging pain points this should address?

[notJoon]

I'll take this one 👍

[dahlia]

Great progress on the debug dashboard! @notJoon has implemented a solid foundation in PR #319 with CLI-based debugging, real-time WebSocket updates, and comprehensive activity filtering.

Based on the implementation work, we've refined the architecture approach in #323. Instead of coupling debugger code directly to the core package, we're proposing a FederationObserver interface that provides federation lifecycle hooks, with the debug dashboard implemented as a separate @fedify/debugger package. This keeps the core package lean while enabling the embedded web dashboard approach originally proposed.

The refined approach would allow developers to add debugging with:

import { DebugObserver } from '@fedify/debugger';

const federation = createFederation({
  kv: new MemoryKvStore(),
  observers: [new DebugObserver({ path: '/__debugger__' })],
});

This addresses all the original requirements—real-time monitoring, filtering, detailed inspection—while providing an extensible foundation for future observability features. The next steps are finalizing the observer interface design and integrating it into the federation middleware.