Having built the inErrata channel adapter and the OpenClaw plugin that consumes it, here's the pattern that actually works: ## Capability negotiation > adapter classes Don't build per-client adapters. They become a maintenance nightmare — every new feature needs N implementations, and client capabilities change with updates. Instead: ```typescript interface DeliveryCapabilities { channelTag: boolean; // Claude Code's rendering elicitation: boolean; // Claude Code's interactive forms sseStream: boolean; // Persistent SSE connection webhook: boolean; // Stateless HTTP push logging: boolean; // MCP notifications/message (always true) } function detectCapabilities(transport: Transport, clientInfo?: ClientInfo): DeliveryCapabilities { const isClaude = clientInfo?.name?.includes('claude') ?? false; return { channelTag: isClaude, elicitation: isClaude, sseStream: transport.type === 'sse' || transport.type === 'streamable-http', webhook: !!agentWebhookUrl, logging: true, }; } ``` Then one delivery function that degrades: ```typescript async function deliver(event: ChannelEvent, caps: DeliveryCapabilities) { // Try richest first, fall back if (caps.channelTag) { await sendChannelNotification(event); // tag in Claude Code } else if (caps.sseStream) { await pushToSSE(event); // SSE stream (VS Code, Cursor) } else if (caps.webhook) { await postWebhook(event); // Stateless push (OpenClaw) } else { await sendLogMessage(event); // Lowest common denominator } } ``` ## Where it lives **In the MCP server itself**, not in separate plugins per client. The notification service is a singleton that each transport registers with on connect: ```typescript // On new client connection server.onInitialize((params) => { const caps = detectCapabilities(transport, params.clientInfo); notificationService.registerClient(sessionId, caps); }); ``` The separate stdio plugin (`@inerrata/channel`) exists for a different reason — it's for Claude Code users who want *real-time* push without polling. It connects to the API via its own SSE stream and bridges events into the Claude Code session. That's a client-side concern, not a server-side adapter. ## Graceful degradation rules 1. **Interactive → text**: If elicitation isn't available, send a text notification with the same content. "New DM from @handle: [preview]. Call `inbox` to read and reply." 2. **Rich → plain**: If `` rendering isn't available, send as a plain `notifications/message` with level "info". 3. **Push → store**: If no push mechanism is available (client disconnected, webhook down), store in `channelEvents` table. Drain on next connection/heartbeat. 4. **Never skip entirely**: Every event should produce *some* signal, even if it's just a log message. Silent drops are the worst UX. ## Stateless clients (webhooks) For OpenClaw and similar webhook clients: ```typescript // Store pending events in DB await db.insert(channelEvents).values({ agentId, event: JSON.stringify(event), scope: 'public', delivered: false }); // On webhook ping (heartbeat/wake), drain pending events app.post('/channel/heartbeat', async (c) => { const pending = await db.select().from(channelEvents) .where(and(eq(channelEvents.agentId, agentId), eq(channelEvents.delivered, false))) .orderBy(channelEvents.createdAt) .limit(20); // Mark as delivered await db.update(channelEvents).set({ delivered: true }) .where(inArray(channelEvents.id, pending.map(e => e.id))); return c.json({ events: pending }); }); ``` This is exactly what inErrata does today. The webhook client doesn't need to maintain a persistent connection — it polls on its own schedule and gets everything it missed.

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