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fix: respect user Vite CORS config - #16924
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elliott-with-the-longest-name-on-github merged 5 commits intoAug 25, 2026
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elliott-with-the-longest-name-on-github merged 5 commits into
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…ndlers during `vite build`, even though `server.cors`/`preview.cors` are irrelevant to building.
This commit fixes the issue reported at packages/kit/src/exports/vite/index.js:51
## Bug
In `packages/kit/src/exports/vite/index.js`, the plugin's `config` hook always builds and returns `new_config` regardless of `config_env.command`. It sets `is_build = config_env.command === 'build'` (line 335) but never uses it to gate CORS resolution:
```js
server: {
cors: resolve_cors(config.server?.cors, 'server.cors'),
...
},
preview: {
cors: resolve_cors(config.preview?.cors, 'preview.cors')
},
```
`resolve_cors` emits a `console.warn` whenever preflight is disabled:
```js
if (preflight_disabled) {
console.warn(styleText(['yellow', 'bold'],
`OPTIONS request handlers will not work unless ...`));
return undefined;
}
```
### Trigger
A user who sets `server.cors: false` (or `true`, or an object with `preflightContinue: false`) in `vite.config.js` and runs **`vite build`** sees this yellow warning. During `build`, neither `server.cors` (dev) nor `preview.cors` (preview) has any effect, so the warning is pure noise unrelated to building.
## Fix
Added a `warn` parameter to `resolve_cors` and gated the `console.warn` on it. The two call sites pass `!is_build`, so the warning only fires for `serve`/`preview` commands where the CORS setting is actually used. The returned config value is unchanged, so build behavior is unaffected.
*(Rebased against the formatting-only commit `d2bde94`; `resolve_cors` is now defined at line 51 and the `preflight_disabled` check was collapsed onto a single line, but the warning remains ungated.)*
Co-authored-by: Vercel <vercel[bot]@users.noreply.github.com>
Co-authored-by: teemingc <chewteeming01@gmail.com>
Co-authored-by: Nic Polumeyv <nicolas.polum@outlook.com>
elliott-with-the-longest-name-on-github
merged commit Aug 25, 2026
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August 25, 2026 21:14
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closes #12574
SvelteKit currently silently overrides user-provided
server.corsandpreview.corsvalues to ensure OPTIONS handlers work during development and preview. This change preserves explicit user configuration instead, while continuing to addpreflightContinue: truewhen it has not been configured. A warning explains that OPTIONS handlers requirepreflightContinue: truewhen the user's CORS setting disables it.Please don't delete this checklist! Before submitting the PR, please make sure you do the following:
Tests
pnpm testand lint the project withpnpm lintandpnpm checkTargeted verification:
pnpm -F @sveltejs/kit test:unit(748 passed, 110 skipped).Changesets
pnpm changesetand following the prompts. Changesets that add features should beminorand those that fix bugs should bepatch. Please prefix changeset messages withfeat:,fix:, orchore:.Edits