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fix: include slot scripts in server island response #15633

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Merged
matthewp merged 9 commits into from
Feb 24, 2026
Merged

fix: include slot scripts in server island response #15633

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97b47f6
fix: include slot scripts in server island response
jwoyo Feb 24, 2026
8c59537
add changeset
jwoyo Feb 24, 2026
09f43cc
fix: cast SlotString for type safety
jwoyo Feb 24, 2026
8b26f9c
use Array.isArray guard for defensive type safety
jwoyo Feb 24, 2026
45f6c69
test: verify slotted component scripts in server island response
jwoyo Feb 24, 2026
8e846fa
Update .changeset/server-island-slot-scripts.md
jwoyo Feb 24, 2026
9735e88
Merge branch 'main' into fix/server-island-deduplicate-scripts
jwoyo Feb 24, 2026
607c8e3
Merge branch 'main' into fix/server-island-deduplicate-scripts
jwoyo Feb 24, 2026
3a5d9a3
improved type import
jwoyo Feb 24, 2026
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5 changes: 5 additions & 0 deletions .changeset/server-island-slot-scripts.md
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@@ -0,0 +1,5 @@
---
'astro': patch
---

Fixes a case where `<script>` tags from components passed as slots to server islands were not included in the response
17 changes: 15 additions & 2 deletions packages/astro/src/runtime/server/render/server-islands.ts
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Expand Up @@ -5,7 +5,7 @@ import { renderChild } from './any.js';
import { createThinHead, type ThinHead } from './astro/head-and-content.js';
import type { RenderDestination } from './common.js';
import { createRenderInstruction } from './instruction.js';
import { type ComponentSlots, renderSlotToString } from './slot.js';
import { type ComponentSlots, type SlotString, renderSlotToString } from './slot.js';

const internalProps = new Set([
'server:component-path',
Expand Down Expand Up @@ -158,7 +158,20 @@ export class ServerIslandComponent {
for (const name in this.slots) {
if (name !== 'fallback') {
const content = await renderSlotToString(this.result, this.slots[name]);
renderedSlots[name] = content.toString();
let slotHtml = content.toString();
// Append script instructions so that components passed as slots
// to server:defer components retain their scripts in the island response.
// renderSlotToString returns a SlotString (typed as string) that carries
// render instructions stripped from the HTML content.
const slotContent = content as unknown as SlotString;
if (Array.isArray(slotContent.instructions)) {
for (const instruction of slotContent.instructions) {
if (instruction.type === 'script') {
slotHtml += instruction.content;
}
}
}
renderedSlots[name] = slotHtml;
}
}

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17 changes: 17 additions & 0 deletions packages/astro/test/fixtures/server-islands/ssr/src/components/ScriptedCounter.astro
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---
---
<div class="counter">
<span data-count>0</span>
<button data-increment>Increment</button>
</div>

<script>
document.querySelectorAll("[data-increment]").forEach((btn) => {
btn.addEventListener("click", () => {
const countEl = btn.previousElementSibling;
if (countEl) {
countEl.textContent = String(Number(countEl.textContent) + 1);
}
});
});
</script>
5 changes: 5 additions & 0 deletions packages/astro/test/fixtures/server-islands/ssr/src/components/Wrapper.astro
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---
---
<div id="wrapper">
<slot name="content" />
</div>
15 changes: 15 additions & 0 deletions packages/astro/test/fixtures/server-islands/ssr/src/pages/slot-with-script.astro
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---
import Wrapper from '../components/Wrapper.astro';
import ScriptedCounter from '../components/ScriptedCounter.astro';
---
<html>
<head>
<title>Slot with script</title>
</head>
<body>
<Wrapper server:defer>
<ScriptedCounter slot="content" />
<div slot="fallback">Loading...</div>
</Wrapper>
</body>
</html>
14 changes: 14 additions & 0 deletions packages/astro/test/server-islands.test.js
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Expand Up @@ -245,6 +245,20 @@ describe('Server islands', () => {
assert.equal(fetchMatch.length, 2, 'should include props in the query string');
assert.equal(fetchMatch[1], '', 'should not include encrypted empty props');
});

it('includes script from slotted component in island response', async () => {
const res = await fixture.fetch('/slot-with-script');
assert.equal(res.status, 200);
const html = await res.text();
// Extract the island fetch URL from the page
const urlMatch = html.match(/fetch\('(\/_server-islands\/Wrapper\?[^']+)'/);
assert.ok(urlMatch, 'should have a server island fetch URL');
const islandRes = await fixture.fetch(urlMatch[1]);
assert.equal(islandRes.status, 200);
const islandHtml = await islandRes.text();
assert.ok(islandHtml.includes('<script'), 'island response should include the script tag from the slotted component');
assert.ok(islandHtml.includes('data-increment'), 'island response should include the slotted component HTML');
});
});

describe('prod', () => {
Expand Down