a layout whose placeholder is not named `Main` passes check AND exec, then fails CE0848 — and there is no `DROP LAYOUT`

[marclehane-creator]

Re-confirmed unchanged on 0.21.0 (2026-09-07).

• Repro.

  CREATE OR REPLACE LAYOUT ProbeSecond.App_Other (layouttype: 'Responsive', class: 'layout-atlas') {
    scrollcontainer layoutContainer { region center (Class: 'region-content') { placeholder Content } }
  }

• Measured. mxcli check -p --references → Check passed!; exec → Created layout;
  mx check → CE0848 "No placeholder with the name 'Main' found. There should be exactly one."
  at Layout 'ProbeSecond.App_Other'.
• This contradicts the release notes' own rationale. 0.20.0 argues that which placeholder is
  "main" is a naming convention (22 of 22 Atlas layouts name one Main, and a page binds by
  qualified name anyway), and on that basis declines to expose MainPlaceholderName as a header
  property. mxbuild enforces it as a rule. Since mxcli now writes layouts, it should enforce
  the same rule the builder does — a one-line check at the point the layout is built.
• ⛔ Compounding: there is no DROP LAYOUT verb. DROP LAYOUT Mod.Name is a parse error
  (no viable alternative at input 'DROPLAYOUT'), and no drop form appears anywhere under
  mxcli syntax layout / layout.alter / layout.show. A layout is creatable and alterable but
  not removable — unique among the doctypes mxcli writes (pages, microflows, entities, queues,
  rules and folders all have one). So a layout authored with the wrong placeholder name cannot be
  deleted headlessly; it must be repaired with CREATE OR REPLACE LAYOUT.
• ⚠ Related, same area: placeholder Name { } — the page spelling, with braces — passes
  mxcli check inside a layout and is then refused by exec with
  "layout X declares no placeholder: a page's content has nowhere to go. Add placeholder Main…".
  In a layout the placeholder is bare. The exec message is excellent; the check that preceded
  it validated the wrong grammar.

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mxcli 0.21.0 (mxcli-windows-amd64.exe, 2026-09-06 build), Mendix 11.11.0 / 11.12.x, Windows 11. Each item was re-measured on a fresh app with a control of the same construct type, and every mx check verdict is the literal The app contains: N errors. line. We keep the full register with repros in our repo; happy to share more detail.