Svelte 5: SVG elements within <slot> fallback not displayed

[techniq]

Describe the bug

If an SVG element (ex. <circle>) is placed within a <slot> as the fallback, the element is not visible, even though the markup is correct.

<slot>
  <circle cx={10} cy={10} r={5} />
  <circle cx={20} cy={20} r={5} />
  <circle cx={30} cy={30} r={5} />
  <circle cx={40} cy={40} r={5} />
  <circle cx={50} cy={50} r={5} />
</slot>

Removing the <slot> wrapper or adding <svelte:options namespace="svg" /> at the top of the component works around the issue.

This is likely due to the element being created with document.createElement("circle") instead of
document.createElementNS("http://www.w3.org/2000/svg", "circle");.

Related issue: #11219

Reproduction

• Svelte 5 REPL
• Svelte 4 REPL

Logs

No response

System Info

Svelte 5 REPL

Severity

blocking an upgrade