plugin: normalize unicode whitespace in filter strings

docs/docs/changelog.md

@@ -16,6 +16,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - You can now sort tasks by their deadlines by name using `deadline` or `deadlineDescending` in the sorting field.
 
+### 🐛 Bug Fixes
+
+- Filter strings now have Unicode whitespace characters (e.g., non-breaking spaces from copy-paste) normalized to regular spaces, preventing API errors.
+
 ## v2.6.0 (2026-02-01)
 
 ### ✨ Features

plugin/src/query/replacements.test.ts

@@ -61,4 +61,41 @@ describe("applyReplacements", () => {
       });
     }
   });
+
+  describe("unicode whitespace normalization", () => {
+    const testcases: TestCase[] = [
+      {
+        description: "should replace non-breaking spaces with regular spaces",
+        filter: "#Project\u00A0&\u00A0/section",
+        expectedFilter: "#Project & /section",
+      },
+      {
+        description: "should replace em spaces with regular spaces",
+        filter: "#Project\u2003&\u2003/section",
+        expectedFilter: "#Project & /section",
+      },
+      {
+        description: "should trim leading and trailing whitespace",
+        filter: "  #Project & /section  ",
+        expectedFilter: "#Project & /section",
+      },
+      {
+        description: "should not modify filters with only regular spaces",
+        filter: "#Project & /section",
+        expectedFilter: "#Project & /section",
+      },
+    ];
+
+    for (const tc of testcases) {
+      it(tc.description, () => {
+        const query: TaskQuery = {
+          filter: tc.filter,
+        };
+
+        applyReplacements(query, new FakeContext(tc.filePath ?? ""));
+
+        expect(query.filter).toBe(tc.expectedFilter);
+      });
+    }
+  });
 });

plugin/src/query/replacements.ts

@@ -6,4 +6,8 @@ export function applyReplacements(query: TaskQuery, ctx: MarkdownPostProcessorCo
   // Replace {filename} with the base file name of file where the query originated.
   const baseFileName = ctx.sourcePath.replace(/.*\//, "").replace(/\.md$/i, "");
   query.filter = query.filter.replace(/{{filename}}/g, baseFileName);
+
+  // Normalize Unicode whitespace characters (e.g., non-breaking spaces, em spaces)
+  // to regular ASCII spaces to prevent API errors.
+  query.filter = query.filter.replace(/[\p{Zs}]/gu, " ").trim();
 }