MCP set_style with multiple classes: second class invisible in Designer UI but affects styling

[mlimmerfolg]

Description

When using set_style (via the element_tool) with two or more class names, only the first class is visible in the Webflow Designer's Style Selector panel. The second (and any subsequent) class is applied to the element and affects rendering, but is completely invisible in the Designer UI.

This means users cannot see, edit, or remove the hidden class through the Designer — only via MCP.

Reproduction Steps

1. Open any Webflow project in the Designer with the MCP app connected
2. Select any element with an existing class (e.g. section_content1)
3. Use MCP element_tool > set_style with two classes:
   {
   "style_names": ["section_content1", "background-color-gray"]
   }
4. MCP responds with success, showing both classes
5. In the Designer Style Selector: only section_content1 is visible
6. background-color-gray is not visible anywhere in the UI (Style Selector, Attributes panel, etc.)
7. However, the styling from background-color-gray is applied to the element

Expected Behavior
Both classes should be visible in the Designer's Style Selector panel, just as if the user had added them manually.

Actual Behavior

• Only the first class appears in the Style Selector
• The second class is invisible but actively affects styling
• Reloading the Designer does not fix the issue
• Deselecting and reselecting the element does not fix the issue
• The isComboClass flag in the MCP response is true

Environment

• Tested on two separate Webflow projects
• Tested on both Component root elements and regular page-level Sections
• Chrome 146, Windows 11
• MCP connector via Claude Code

Impact

• Hidden styling dependencies that users cannot manage
• No way to remove the hidden class through the Designer UI
• Users may unknowingly accumulate invisible classes that affect their design
• Workaround: only set one class per set_style call, use wrapper divs for additional classes

[viratatwebflow]

Thanks for reporting it. team is working on a fix

[mlimmerfolg]

Hi @viratatwebflow ,

Update — follow-up test, reframing the issue

(Written by Claude Code — the AI agent that was using the MCP tools and originally filed this issue through my user. Sharing verbatim so you can see the exact mental model that led to the misdiagnosis.)

Why I made the mistake originally:
create_style mentions parent_style_names only in passing ("this will use to create combo class"). As an LLM I read this as an optional hint, not as the central mechanism for combo creation. set_style contains no hint about combo prerequisites at all. My wrong assumption was therefore: "a combo is formed when setting on the element, by passing two styles together." The opposite is true.

What does not work:
create_style("base") // no parent
create_style("second") // no parent
set_style(element, ["base", "second"])
→ Designer shows only base in the Style Selector. second appears in the Inheritance dropdown as a parallel base class, not as a combo. Both styles affect rendering — which looked like a hidden-combo bug.
Reality: two independent base classes attached to one element, an unusual Webflow state that surfaces inconsistently in the UI.

What works (= the solution):
create_style("base")
create_style("combo", parent_style_names: ["base"]) // response: isComboClass: true
set_style(element, ["base", "combo"])
→ Designer shows base as base and combo as a proper combo class below it, identical to manually creating the combo in the UI.

How it works (mechanism):
parent_style_names during create_style marks the style in Webflow's data model as a combo definition (flag isComboClass: true). set_style reads this flag and establishes the combo cascade correctly. Without the flag, multiple styles are attached as parallel base classes.

Documentation suggestions:

1. Most important: make it prominent in both set_style AND create_style that combos require the child style to have been created with parent_style_names. The current mention is easily overlooked by LLMs.
2. Optional response hint: when set_style receives 2+ styles with no parent/child link among them → return a warning that they will attach as parallel base classes.
3. Optional: consider whether the planned fix should auto-promote b into a combo under a when set_style([a, b]) is called with a fresh b — that would also resolve the confusion.

Feel free to close this issue or keep it open as a docs tracker. Thanks for the fast response.

thx ;)