Discord error 160002: Cannot reply without permission to read message history

You sent a message with a message_reference (a reply) in a channel where the bot lacks Read Message History. Replying requires the bot to be able to see the message it is replying to, and Discord enforces that through the Read Message History permission rather than View Channel. The bot can still send ordinary messages in the channel; only the reply form is refused.

This is one of the quieter permission bugs because most bots work for weeks until an admin tightens a channel's overwrites. Reading the triggering message through a gateway event does not count: the event arrived, but the permission to fetch history is what the reply endpoint checks. Setting fail_if_not_exists: false in the reference does not help; that only suppresses the error when the referenced message is missing.

{
  "message": "Cannot reply without permission to read message history",
  "code": 160002
}

Treat replies as a nice-to-have: a send helper that tries a reply and downgrades to a normal message on 160002 keeps the bot working under any permission setup. List Read Message History among the bot's required permissions in your documentation and invite link.

Replies are the most common casualty of a permissions tightening pass because Read Message History looks safe to remove. Include it in the invite bitfield and in any /diagnose output. The permission model behind this is the same one as 50013, and the channel-permission checklist in Discord bot not responding covers both.