Large Message workflow sub-action: Message/body content not rendered in modal

Problem Statement

A workflow action's Large Message sub-action renders its Title correctly but never displays the configured Message/body content in the modal, making the sub-action unusable for its primary purpose on affected versions. Confirmed via network inspection that the correct message content is delivered to the client but not applied to the modal.

The modal displays only the Title. The Message/body area is empty, regardless of whether the message content is plain text or HTML.

Steps to Reproduce

1. On an existing workflow scheme (reproduced on the Blog and default System workflows on demo.dotcms.com; also reproduced on a custom workflow scheme in a customer environment), add a Large Message sub-action to any workflow action.
2. Configure the sub-action with: User IDs = Current User, Message = TEST (also tested

   TEST

   as HTML — same result), Title = Test Preview, Width = 50%, Height = 90%, Language = java, Code = empty.
3. Save the action.
4. From the content edit screen, fire the workflow action.
5. Observe the resulting modal.

• Reviewed LargeMessageActionlet/processMessageValue source (dotCMS/core, master branch): confirmed message is always processed and set independently of code/lang — those two only add an additional code block when both are set, and don't suppress or interact with message. Ruled out as the cause.
• Exported the workflow scheme JSON and confirmed the message parameter is saved correctly server-side.
• Cleared cache — no change.
• Inspected the DOM at modal-open time: the message content is genuinely absent from the rendered DOM, not present-but-hidden via CSS.
• Delivery happens via a persistent connection (shows as a single long-lived "events" entry in the browser Network panel rather than a discrete per-fire request). Inspecting that connection's individual pushed frames confirmed a body: "TEST" frame is delivered to the client with the correct content — so the data reaches the browser but isn't applied to the modal.
• That connection showed unusually long Stalled (~1.1 min) and Content Download (~1.9 min) phases for what should be a near-instant push.
• Title reliably updates correctly on every fire, isolating the defect specifically to the Message/body not being applied, rather than a broader modal-rendering failure.
• Reproduces identically in both Chrome and Firefox — not browser-specific.

Acceptance Criteria

The modal displays both the configured Title ("Test Preview") and the Message/body content ("TEST").

dotCMS Version

• dotCMS versions: v26.08.19-04 and v26.09.09-01 appear to be broken
• local environment running v25.07.02-1 is working as expected

Severity

Medium - Some functionality impacted

Links

NA

Start by reading LargeMessageActionlet/processMessageValue and reproduce the workflow action with the supplied TEST message. Trace the client-side handling of the delivered body frame and modal rendering, then verify that the modal shows both the configured title and message content in the affected versions.