diff --git a/lib/codecept.js b/lib/codecept.js
index 05203d241..5f6a48b08 100644
--- a/lib/codecept.js
+++ b/lib/codecept.js
@@ -284,6 +284,9 @@ class Codecept {
       // Ignore if gherkin module not available
     }
 
+    // Sort test files alphabetically for consistent execution order
+    this.testFiles.sort()
+
     return new Promise((resolve, reject) => {
       const mocha = container.mocha()
       mocha.files = this.testFiles
diff --git a/test/unit/alphabetical_order_test.js b/test/unit/alphabetical_order_test.js
new file mode 100644
index 000000000..0f1f55680
--- /dev/null
+++ b/test/unit/alphabetical_order_test.js
@@ -0,0 +1,95 @@
+import { expect } from 'chai'
+import Codecept from '../../lib/codecept.js'
+import Container from '../../lib/container.js'
+import path from 'path'
+import fs from 'fs'
+import { fileURLToPath } from 'url'
+import { dirname } from 'path'
+
+const __filename = fileURLToPath(import.meta.url)
+const __dirname = dirname(__filename)
+
+describe('Test Files Alphabetical Order', () => {
+  let codecept
+  const tempDir = path.join(__dirname, '../data/sandbox/configs/alphabetical_order')
+  const config = {
+    tests: `${tempDir}/*_test.js`,
+    gherkin: { features: null },
+    output: './output',
+    hooks: [],
+  }
+
+  before(() => {
+    if (!fs.existsSync(tempDir)) {
+      fs.mkdirSync(tempDir, { recursive: true })
+    }
+
+    fs.writeFileSync(
+      path.join(tempDir, 'zzz_test.js'),
+      `
+        Feature('Test');
+        Scenario('zzz test', () => {});
+      `,
+    )
+    fs.writeFileSync(
+      path.join(tempDir, 'aaa_test.js'),
+      `
+        Feature('Test');
+        Scenario('aaa test', () => {});
+      `,
+    )
+    fs.writeFileSync(
+      path.join(tempDir, 'mmm_test.js'),
+      `
+        Feature('Test');
+        Scenario('mmm test', () => {});
+      `,
+    )
+  })
+
+  after(() => {
+    const files = ['zzz_test.js', 'aaa_test.js', 'mmm_test.js']
+    files.forEach(file => {
+      const filePath = path.join(tempDir, file)
+      if (fs.existsSync(filePath)) {
+        fs.unlinkSync(filePath)
+      }
+    })
+  })
+
+  beforeEach(async () => {
+    codecept = new Codecept(config, {})
+    await codecept.init(path.join(__dirname, '../data/sandbox'))
+  })
+
+  afterEach(() => {
+    Container.clear()
+  })
+
+  it('should not sort test files in loadTests (sorting happens in run)', () => {
+    codecept.loadTests()
+
+    if (codecept.testFiles.length === 0) {
+      console.log('No test files found, skipping test')
+      return
+    }
+
+    // After loadTests(), files should be in glob order (NOT sorted).
+    // Sorting should only happen later in run().
+    const filenames = codecept.testFiles.map(filePath => path.basename(filePath))
+
+    // Verify all 3 test files were loaded
+    expect(filenames).to.include('aaa_test.js')
+    expect(filenames).to.include('mmm_test.js')
+    expect(filenames).to.include('zzz_test.js')
+    expect(filenames.length).to.equal(3)
+
+    // Verify that sorting the files produces alphabetical order
+    const sortedFiles = [...codecept.testFiles].sort()
+    const sortedFilenames = sortedFiles.map(filePath => path.basename(filePath))
+
+    expect(sortedFilenames[0]).to.include('aaa_test.js')
+    expect(sortedFilenames[1]).to.include('mmm_test.js')
+    expect(sortedFilenames[2]).to.include('zzz_test.js')
+  })
+})
diff --git a/test/unit/worker_test.js b/test/unit/worker_test.js
index 635f00b72..6c0a51978 100644
--- a/test/unit/worker_test.js
+++ b/test/unit/worker_test.js
@@ -382,4 +382,35 @@ describe('Workers', function () {
 
     workers.run()
   })
+
+  it('should preserve original file order in loadTests for worker distribution (issue #5412)', async () => {
+    // This test verifies the fix for issue #5412:
+    // Test files should NOT be sorted in loadTests() because that affects worker distribution.
+    // Sorting should only happen in run() for execution order.
+    //
+    // The bug was: sorting in loadTests() changed the order of suites during distribution,
+    // causing all workers to receive the same tests instead of different suites.
+
+    const workerConfig = {
+      by: 'suite',
+      testConfig: './test/data/sandbox/codecept.customworker.js',
+    }
+
+    const workers = new Workers(3, workerConfig)
+    await workers._ensureInitialized()
+
+    // Verify that test files were loaded
+    const testFiles = workers.codecept.testFiles
+    expect(testFiles.length).to.be.greaterThan(1, 'Multiple test files should be loaded')
+
+    // loadTests() must preserve the original glob order (not sort files).
+    // Verify by comparing with a fresh glob call — the order should match.
+    const { globSync } = await import('glob')
+    const expectedFiles = globSync('./custom-worker/*.js', { cwd: path.join(__dirname, '/../data/sandbox') })
+      .filter(f => !f.includes('node_modules'))
+      .map(f => path.resolve(path.join(__dirname, '/../data/sandbox'), f))
+
+    const actualFiles = testFiles.map(f => path.resolve(f))
+    expect(actualFiles).to.deep.equal(expectedFiles, 'loadTests() should preserve original glob order without sorting')
+  })
 })