diff --git a/.github/workflows/validation.yaml b/.github/workflows/validation.yaml
index 7bb00098e..10528a62c 100644
--- a/.github/workflows/validation.yaml
+++ b/.github/workflows/validation.yaml
@@ -40,6 +40,18 @@ jobs:
       - name: Run tests and check code coverage
         run: npm run test:coverage
 
+      - name: Check that tests left the working tree clean
+        # Tests must clean up after themselves; a leaked artifact once got
+        # committed from a local run (google/adk-js#276).
+        shell: bash
+        run: |
+          changes="$(git status --porcelain)"
+          if [ -n "$changes" ]; then
+            echo "::error::The test run left the working tree dirty. Tests must delete the files they create, or write them under a temp directory (fs.mkdtemp)."
+            echo "$changes"
+            exit 1
+          fi
+
       - name: Run lint check
         run: npm run lint
 
diff --git a/core/src/code_executors/unsafe_local_code_executor.ts b/core/src/code_executors/unsafe_local_code_executor.ts
index 97061719a..b54641817 100644
--- a/core/src/code_executors/unsafe_local_code_executor.ts
+++ b/core/src/code_executors/unsafe_local_code_executor.ts
@@ -178,9 +178,17 @@ export class UnsafeLocalCodeExecutor extends BaseCodeExecutor {
       const filePath = res.filePath;
       tempDir = res.tempDir;
 
-      if (params.codeExecutionInput.inputFiles) {
-        await materializeFiles(params.codeExecutionInput.inputFiles, tempDir);
-      }
+      // Recorded as resolved paths rather than names: `fs.readdir` reports
+      // platform separators (`subdir\file` on Windows) while `File.name` is
+      // always `/`-separated, so comparing the two as raw strings misses
+      // nested inputs and re-reports them as script output.
+      const inputFiles = await materializeFiles(
+        params.codeExecutionInput.inputFiles,
+        tempDir,
+      );
+      const inputFilePaths = new Set(
+        inputFiles.map((f) => path.join(res.tempDir, f.name)),
+      );
 
       let command = this.nodeCommandPath;
       let args = [filePath];
@@ -271,10 +279,7 @@ export class UnsafeLocalCodeExecutor extends BaseCodeExecutor {
           }
 
           // Skip input files
-          const isInputFile = params.codeExecutionInput.inputFiles?.some(
-            (f) => f.name === relativeFilePath,
-          );
-          if (isInputFile) {
+          if (inputFilePaths.has(fullPath)) {
             continue;
           }
 
diff --git a/core/test/code_executors/unsafe_local_code_executor_test.ts b/core/test/code_executors/unsafe_local_code_executor_test.ts
index 82a0d2d01..e568274e6 100644
--- a/core/test/code_executors/unsafe_local_code_executor_test.ts
+++ b/core/test/code_executors/unsafe_local_code_executor_test.ts
@@ -7,6 +7,7 @@
 import {
   CodeExecutionLanguage,
   ExecuteCodeParams,
+  FileContentEncoding,
   InvocationContext,
   LlmAgent,
   PluginManager,
@@ -321,6 +322,39 @@ describe('UnsafeLocalCodeExecutor', () => {
     expect(result.outputFiles![0].mimeType).toBe('text/plain');
   });
 
+  it('should exclude nested input files from the returned output files', async () => {
+    const params: ExecuteCodeParams = {
+      invocationContext,
+      codeExecutionInput: {
+        code: 'const fs = require("fs"); fs.writeFileSync("new_output.txt", "hello from script");',
+        language: CodeExecutionLanguage.JAVASCRIPT,
+        // A nested input file is read back from disk as `scripts/hello.js` on
+        // POSIX and `scripts\hello.js` on Windows, and `./assets/logo.txt` is
+        // a third spelling of the same path. All of them denote an input and
+        // must not be reported as script output.
+        inputFiles: [
+          {
+            name: 'scripts/hello.js',
+            content: 'console.log("hello");',
+            contentEncoding: FileContentEncoding.UTF8,
+            mimeType: 'text/javascript',
+          },
+          {
+            name: './assets/logo.txt',
+            content: 'logo',
+            contentEncoding: FileContentEncoding.UTF8,
+            mimeType: 'text/plain',
+          },
+        ],
+      },
+    };
+
+    const result = await executor.executeCode(params);
+
+    expect(result.stderr).toBe('');
+    expect(result.outputFiles!.map((f) => f.name)).toEqual(['new_output.txt']);
+  });
+
   it('should infer correct mimeType for generated JSON files', async () => {
     const params: ExecuteCodeParams = {
       invocationContext,