When an agent has one configured destination (e.g. Discord) but receives a message from a different channel (e.g. Slack), the single-destination shortcut was routing replies to the destination instead of the originating channel. Now uses the inbound message's routing context (channel_type, platform_id) when available, falling back to the destination table only when routing context is absent. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>