diff --git a/index.cjs b/index.cjs
index 3b0a6193c..48e528641 100644
--- a/index.cjs
+++ b/index.cjs
@@ -3,7 +3,7 @@
 const fs = require('fs');
 const path = require('path');
 
-const { calculatePrRework, calculateReworkSummary } = require('./lib/rework');
+const { calculatePrRework, calculateReworkSummary } = require('./lib/rework.cjs');
 
 const GREEN = '\x1b[32m';
 const RED = '\x1b[31m';
diff --git a/lib/rework.js b/lib/rework.cjs
similarity index 100%
rename from lib/rework.js
rename to lib/rework.cjs
diff --git a/test/rework-rate.test.cjs b/test/rework-rate.test.cjs
index 4f1dad837..711745dd9 100644
--- a/test/rework-rate.test.cjs
+++ b/test/rework-rate.test.cjs
@@ -6,7 +6,7 @@ const { execFileSync } = require('child_process');
 const CLI = path.join(__dirname, '..', 'index.cjs');
 
 // Import rework calculation functions from the pure module (no CLI side effects)
-const { calculatePrRework, calculateReworkSummary } = require(path.join(__dirname, '..', 'lib', 'rework.js'));
+const { calculatePrRework, calculateReworkSummary } = require(path.join(__dirname, '..', 'lib', 'rework.cjs'));
 
 describe('calculatePrRework', () => {
   it('should return zero rework for PR with no reviews', () => {