# Multi-Channel Delivery (Slack, Teams, Email, Webhooks)

## Module
Notifier

## Status
IMPLEMENTED

## Description
Multi-channel notification delivery with Slack, Webhook connectors (and PagerDuty in Notifier), with snapshot testing and error handling.

## Implementation Details
- **IChannelAdapter interface**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Channels/IChannelAdapter.cs` -- `DispatchAsync` (sends notification via channel), `CheckHealthAsync` (verifies channel connectivity), typed by `NotifyChannelType`
- **ChannelAdapterFactory**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Channels/ChannelAdapterFactory.cs` -- resolves channel adapters by type, `GetAdapter`/`GetAllAdapters` for DI-based adapter registry
- **SlackChannelAdapter**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Channels/SlackChannelAdapter.cs` -- Slack delivery adapter
- **WebhookChannelAdapter**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Channels/WebhookChannelAdapter.cs` -- generic webhook delivery adapter
- **ChatWebhookChannelAdapter**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Channels/ChatWebhookChannelAdapter.cs` -- chat-specific webhook adapter (Teams, Discord, etc.)
- **PagerDutyChannelAdapter**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Channels/PagerDutyChannelAdapter.cs` -- PagerDuty incident creation adapter
- **OpsGenieChannelAdapter**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Channels/OpsGenieChannelAdapter.cs` -- OpsGenie alert adapter
- **EmailChannelAdapter**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Channels/EmailChannelAdapter.cs` -- email delivery adapter
- **InAppChannelAdapter**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Channels/InAppChannelAdapter.cs` -- in-app notification adapter
- **WebhookChannelDispatcher**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Dispatch/WebhookChannelDispatcher.cs` -- dispatches to webhook-based channels
- **IWebhookSecurityService**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Security/IWebhookSecurityService.cs` -- webhook signature verification
- **IFallbackHandler**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Fallback/IFallbackHandler.cs` -- fallback when primary channel fails
- **HttpEgressSloSink**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Worker/Processing/HttpEgressSloSink.cs` -- SLO tracking for HTTP egress
- **Templates**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.WebService/offline/notifier/templates/` -- Slack and webhook templates for risk, attestation, deprecation events
- **Tests**: `src/Notifier/StellaOps.Notifier/StellaOps.Notifier.Tests/Channels/WebhookChannelAdapterTests.cs`, `Dispatch/WebhookChannelDispatcherTests.cs`, `Dispatch/SimpleTemplateRendererTests.cs`, `Security/WebhookSecurityServiceTests.cs`, `Fallback/FallbackHandlerTests.cs`, `HttpEgressSloSinkTests.cs`
- **Source**: Feature matrix scan

## E2E Test Plan
- [ ] Verify Slack channel adapter delivers notifications with Block Kit formatting
- [ ] Test webhook channel adapter posts to configured URLs with HMAC signature
- [ ] Verify PagerDuty adapter creates incidents with correct severity mapping
- [ ] Test OpsGenie adapter creates alerts with priority
- [ ] Verify email adapter sends with subject and rendered body
- [ ] Test in-app notification adapter records notifications for UI retrieval
- [ ] Verify channel health checks detect unreachable endpoints
- [ ] Test fallback handler routes to secondary channel on primary failure
- [ ] Verify egress SLO tracking records delivery latency