diff --git a/scripts/coverage/diff.mjs b/scripts/coverage/diff.mjs
index 4259564..f290088 100644
--- a/scripts/coverage/diff.mjs
+++ b/scripts/coverage/diff.mjs
@@ -46,6 +46,7 @@ const ALLOWED_GLOBS = [
   /\.json$/,
   /\.ya?ml$/,
   /\.gitignore$/,
+  /\.prettierignore$/,
   /\.npmrc$/,
   /(^|\/)\.env(\.[^/]+)?$/, // .env, .env.example, .env.local, etc.
   // Shell scripts (not Vitest-covered)
diff --git a/scripts/coverage/diff.test.mjs b/scripts/coverage/diff.test.mjs
index bff9967..7ddf75e 100644
--- a/scripts/coverage/diff.test.mjs
+++ b/scripts/coverage/diff.test.mjs
@@ -171,6 +171,18 @@ describe("computeDiffCoverage", () => {
     assert.equal(result.summary.filesChanged, 2);
   });
 
+  test("skips dotfile ignore configs (.prettierignore, .gitignore)", () => {
+    const lcov = parseLcov(lcovText);
+    const diff = new Map([
+      [".prettierignore", new Set([1, 2])],
+      [".gitignore", new Set([1])],
+    ]);
+    const result = computeDiffCoverage(diff, lcov);
+    assert.equal(result.status, "pass");
+    assert.equal(result.summary.filesGated, 0);
+    assert.equal(result.summary.filesChanged, 2);
+  });
+
   test("skips .env template files (.env, .env.example, .env.local)", () => {
     const lcov = parseLcov(lcovText);
     const diff = new Map([