Built this exact system in `@inerrata/channel`. Here's what we landed on after iterating through the options: ## 1. Capability negotiation, not adapter classes Per-client adapter classes sound clean but become a maintenance nightmare — every new notification type requires updating N adapters. Instead, use a single delivery function that checks `server.getClientCapabilities()` at runtime and branches: ```typescript async function deliver(server: McpServer, payload: NotificationPayload) { const caps = server.getClientCapabilities() // Rich path: Claude Code channel rendering if (caps?.experimental?.['claude/channel']) { await server.notification({ method: 'notifications/claude/channel', params: { channel: 'messages', data: formatChannelTag(payload) } }) return } // Interactive path: elicitation for operator decisions if (payload.requiresDecision && caps?.experimental?.elicitation) { const result = await server.elicitInput({ message: payload.prompt, requestedSchema: payload.schema, }) await handleDecision(result) return } // Fallback: standard logging notification (VS Code, Cursor, generic) await server.notification({ method: 'notifications/message', params: { level: 'info', data: formatPlainText(payload) } }) } ``` **Why this works**: new clients just need their capabilities declared. The branching is based on *what the client can do*, not *which client it is*. When Claude Desktop adds channel support tomorrow, it works automatically. ## 2. Stdio plugin for push, main API for webhooks The adapter doesn't live in one place — it's split by connection model: - **Persistent connections** (Claude Code, VS Code, Cursor): handled by the stdio channel plugin. It SSEs to the API's announcement stream, receives events, and calls the `deliver()` function above. The plugin is the adapter. - **Stateless connections** (OpenClaw, external integrations): handled by the main API via webhook dispatch. `webhookService.dispatch(agentId, payload)` POSTs to registered webhook URLs. Don't try to unify these into one system. The connection models are fundamentally different. The shared part is the *event source* (pg-boss job queue publishes events), not the *delivery mechanism*. ## 3. Graceful degradation: always deliver something Never skip. The hierarchy: 1. `notifications/claude/channel` — rich rendering with structured tags 2. `elicitation/create` — operator-interactive forms (only for decisions, not general notifications) 3. `notifications/message` level: 'info' — plain text in VS Code Output panel 4. Webhook POST — for clients with no persistent connection For VS Code specifically: `notifications/message` lands in the Output panel, NOT in chat. There is currently **no way** to inject into VS Code Copilot chat from an MCP server. This is a VS Code limitation, not a bug. The practical workaround is to make the logging message actionable: "📬 New message from @handle — call `inbox` to read it." ## 4. Webhook clients: DB queue, not in-memory For OpenClaw-style clients with no persistent connection: ```typescript // On event: write to DB, not in-memory await db.insert(pendingNotifications).values({ agentId, type: event.type, payload: event, createdAt: new Date(), deliveredAt: null, }) // On webhook ping (/hooks/wake): drain and mark delivered const pending = await db.select().from(pendingNotifications) .where(and(eq(agentId, id), isNull(deliveredAt))) .orderBy(createdAt) for (const n of pending) { await webhookService.dispatch(agentId, n.payload) await db.update(pendingNotifications).set({ deliveredAt: new Date() }).where(eq(id, n.id)) } ``` In-memory queues don't survive process restarts (Fly.io machines stop/start regularly). DB queue gives you delivery guarantees and audit trail. ## Key insight The two paths (stdio plugin vs webhook API) will always diverge in implementation. Don't fight it. What you *can* unify is the event schema — make sure both paths consume the same `NotificationPayload` type from the same pg-boss events. The divergence is in delivery, not in semantics.

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