From 7ff413bad4e8de388f61453f57440e342d5e520a Mon Sep 17 00:00:00 2001
From: Robin Malfait <malfait.robin@gmail.com>
Date: Thu, 25 Jun 2026 13:21:12 +0200
Subject: [PATCH] Ignore unknown at-rule warnings for `@position-try` (#20277)
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This PR ignores Lightning CSS warnings for the unknow at-rule
`@position-try`.

This is a temporary fix/workaround until support for `@position-try`
lands in Lightning CSS:
https://github.com/parcel-bundler/lightningcss/pull/1238

Fixes: #20275

## Test plan

Ran a test based on the issue:

Before:
```shellsession
❯ tw -i x.css -o out.css --optimize
≈ tailwindcss v4.3.1

Found 1 warning while optimizing generated CSS:

│   position-try-fallbacks: --flip-above;
│ }
│ @position-try --flip-above {
┆              ^-- Unknown at rule: @position-try
┆
│   top: auto;
│   bottom: 0;

Done in 29ms
```

After:
```shellsession
❯ tw -i x.css -o out.css --optimize
≈ tailwindcss v4.3.1

Done in 14ms
```
---
 packages/@tailwindcss-node/src/optimize.ts | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/packages/@tailwindcss-node/src/optimize.ts b/packages/@tailwindcss-node/src/optimize.ts
index 6e60f8b87..5e0234432 100644
--- a/packages/@tailwindcss-node/src/optimize.ts
+++ b/packages/@tailwindcss-node/src/optimize.ts
@@ -68,6 +68,13 @@ export function optimize(
       return false
     }
 
+    // Ignore warnings about unknown at-rules.
+    //
+    // TODO: drop `@position-try` once https://github.com/parcel-bundler/lightningcss/pull/1238 lands
+    if (/Unknown at rule: @position-try/.test(warning.message)) {
+      return false
+    }
+
     return true
   })