Webhooks never fire for the personal Inbox board (board.type="inbox")

A webhook registered on the personal Trello Inbox board is created successfully (active=true) but never receives any action events when cards are added to the Inbox. consecutiveFailures stays 0 (Trello never even attempts delivery). An identical callback on a normal board delivers fine.

Repro:

  1. GET /1/members/me?fields=inbox → note inbox.idBoard
    (board’s type is “inbox”).
  2. POST /1/webhooks with idModel=,
    callbackURL= → returns active:true.
  3. Add a card to the Inbox (UI, or POST /1/cards into
    inbox.idList).
  4. Observed: no POST to the callback; webhook
    consecutiveFailures stays 0.
  5. Control: same callback on a regular board receives
    createCard normally.

Expected: either Inbox board actions fire webhooks, or the API documents/rejects webhooks on type=“inbox” boards so integrators don’t get a silently-dead webhook.

Env: REST API; standard API key; token has full access to the Inbox board (can read it + its cards).