diff --git a/CHANGELOG.md b/CHANGELOG.md
index a7ba50dcd..cb433421f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -30,6 +30,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Export missing `PluginWithConfig` type from `tailwindcss/plugin` to fix errors when inferring plugin config types ([#19707](https://github.com/tailwindlabs/tailwindcss/pull/19707))
 - Ensure `start` and `end` legacy utilities without values do not generate CSS ([#20003](https://github.com/tailwindlabs/tailwindcss/pull/20003))
 - Ensure `--value(…)` is required in functional `@utility` definitions ([#20005](https://github.com/tailwindlabs/tailwindcss/pull/20005))
+- Canonicalization: preserve required whitespace around operators in negated arbitrary values (e.g. `-left-[(var(--a)+var(--b))]`) ([#20011](https://github.com/tailwindlabs/tailwindcss/pull/20011))
 
 ## [4.2.4] - 2026-04-21
 
diff --git a/packages/tailwindcss/src/utilities.test.ts b/packages/tailwindcss/src/utilities.test.ts
index 219302ae3..6b018f672 100644
--- a/packages/tailwindcss/src/utilities.test.ts
+++ b/packages/tailwindcss/src/utilities.test.ts
@@ -1109,6 +1109,9 @@ test('left', async () => {
         'left-4',
         '-left-4',
         'left-[4px]',
+
+        // https://github.com/tailwindlabs/tailwindcss/issues/20010
+        '-left-[(var(--my-var1)+var(--my-var2))]',
       ],
     ),
   ).toMatchInlineSnapshot(`
@@ -1121,6 +1124,10 @@ test('left', async () => {
       left: calc(var(--spacing-4) * -1);
     }
 
+    .-left-\\[\\(var\\(--my-var1\\)\\+var\\(--my-var2\\)\\)\\] {
+      left: calc((var(--my-var1) + var(--my-var2)) * -1);
+    }
+
     .-left-full {
       left: -100%;
     }
diff --git a/packages/tailwindcss/src/utilities.ts b/packages/tailwindcss/src/utilities.ts
index 565b64523..c40f3be93 100644
--- a/packages/tailwindcss/src/utilities.ts
+++ b/packages/tailwindcss/src/utilities.ts
@@ -24,6 +24,7 @@ import {
   isValidOpacityValue,
   isValidSpacingMultiplier,
 } from './utils/infer-data-type'
+import { addWhitespaceAroundMathOperators } from './utils/math-operators'
 import { replaceShadowColors } from './utils/replace-shadow-colors'
 import { segment } from './utils/segment'
 import * as ValueParser from './value-parser'
@@ -450,7 +451,10 @@ export function createUtilities(theme: Theme) {
         if (value === null) return
 
         // Negate the value if the candidate has a negative prefix.
-        return desc.handle(negative ? `calc(${value} * -1)` : value, dataType)
+        return desc.handle(
+          negative ? addWhitespaceAroundMathOperators(`calc(${value} * -1)`) : value,
+          dataType,
+        )
       }
     }