diff --git a/.github/workflows/action-integration-test.yml b/.github/workflows/action-integration-test.yml
new file mode 100644
index 0000000..6ffaafb
--- /dev/null
+++ b/.github/workflows/action-integration-test.yml
@@ -0,0 +1,62 @@
+name: Action Integration Test
+
+on:
+  pull_request:
+  workflow_dispatch:
+    inputs:
+      ref:
+        description: 'Optional branch, tag, or SHA to checkout for testing'
+        required: false
+        default: 'main'
+  push:
+    branches:
+      - 'main'
+
+jobs:
+  test-action:
+    name: Test composite action behavior
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        case:
+          - name: clean notebook should pass
+            path: tests/e2e_notebooks/test_nochange.ipynb
+            expect_failure: false
+          - name: clean notebook with parentheses in filename should pass
+            path: tests/e2e_notebooks/test (nochange).ipynb
+            expect_failure: false
+          - name: dirty notebook with space in filename should fail
+            path: tests/e2e_notebooks/test metadata.ipynb
+            expect_failure: true
+          - name: dirty notebook should fail
+            path: tests/e2e_notebooks/test_metadata.ipynb
+            expect_failure: true
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v6
+        with:
+          ref: ${{ inputs.ref }}
+
+      - name: Run action for ${{ matrix.case.name }}
+        id: run_case
+        continue-on-error: true
+        uses: ./
+        with:
+          paths: |
+            ${{ matrix.case.path }}
+
+      - name: Assert expected outcome
+        if: always()
+        shell: bash
+        run: |
+          expected_outcome="${{ matrix.case.expect_failure && 'failure' || 'success' }}"
+          actual_outcome="${{ steps.run_case.outcome }}"
+
+          if [ "$actual_outcome" != "$expected_outcome" ]; then
+            echo "Case: ${{ matrix.case.name }}"
+            echo "Path: ${{ matrix.case.path }}"
+            echo "Expected outcome: $expected_outcome"
+            echo "Actual outcome: $actual_outcome"
+            exit 1
+          fi
diff --git a/README.md b/README.md
index cac2b0f..fdd737f 100644
--- a/README.md
+++ b/README.md
@@ -591,7 +591,7 @@ All inputs are optional and have sensible defaults:
 | Input | Description | Default |
 | ----- | ----------- | ------- |
 | `python-version` | Python version to use (supports versions, ranges, or "3.x") | `'3.x'` |
-| `paths` | Space-separated list of paths to check (supports wildcards) | `'**/*.ipynb'` |
+| `paths` | Newline-separated list of paths to check (supports wildcards) | `'**/*.ipynb'` |
 | `extra-keys` | Extra metadata keys to strip (space-separated) | `''` |
 | `keep-output` | Keep output in notebooks | `'false'` |
 | `keep-count` | Keep execution counts | `'false'` |
@@ -605,7 +605,9 @@ All inputs are optional and have sensible defaults:
 - name: Check notebooks are stripped
   uses: kynan/nbstripout@main
   with:
-    paths: 'notebooks/*.ipynb examples/*.ipynb'
+    paths: |
+      notebooks/*.ipynb
+      examples/*.ipynb
 ```
 
 #### Strip extra metadata keys
@@ -641,7 +643,8 @@ All inputs are optional and have sensible defaults:
 - name: Check notebooks are stripped
   uses: kynan/nbstripout@main
   with:
-    paths: 'notebooks/**/*.ipynb'
+    paths: |
+      notebooks/**/*.ipynb
     keep-count: 'true'
     extra-keys: 'metadata.widgets cell.metadata.tags'
 ```
diff --git a/action.yml b/action.yml
index ef7a7c7..35e78b4 100644
--- a/action.yml
+++ b/action.yml
@@ -6,7 +6,7 @@ inputs:
     required: false
     default: '3.x'
   paths:
-    description: 'Space-separated list of paths to check (supports wildcards)'
+    description: 'Newline-separated list of paths to check (supports wildcards)'
     required: false
     default: '**/*.ipynb'
   extra-keys:
@@ -33,63 +33,69 @@ runs:
       with:
         python-version: ${{ inputs.python-version }}
         pip-install: 'nbstripout'
-    
-    - name: Find notebook files
-      id: find-notebooks
-      shell: bash
-      run: |
-        # Find all notebooks matching the patterns
-        notebooks=""
-        for pattern in ${{ inputs.paths }}; do
-          found=$(find . -path "./$pattern" -type f 2>/dev/null || true)
-          if [ -n "$found" ]; then
-            notebooks="$notebooks $found"
-          fi
-        done
-        
-        if [ -z "$notebooks" ]; then
-          echo "No notebook files found"
-        else
-          echo "Found notebooks: $notebooks"
-          echo "notebooks=$notebooks" >> $GITHUB_OUTPUT
-        fi
-    
+
     - name: Check notebooks are stripped
-      if: steps.find-notebooks.outputs.notebooks != ''
       shell: bash
+      env:
+        INPUT_PATHS: ${{ inputs.paths }}
+        INPUT_EXTRA_KEYS: ${{ inputs.extra-keys }}
+        INPUT_KEEP_OUTPUT: ${{ inputs.keep-output }}
+        INPUT_KEEP_COUNT: ${{ inputs.keep-count }}
+        INPUT_STRIP_INIT_CELLS: ${{ inputs.strip-init-cells }}
       run: |
-        # Build nbstripout command with options
-        cmd="nbstripout --verify"
-        
-        if [ "${{ inputs.keep-output }}" = "true" ]; then
-          cmd="$cmd --keep-output"
+        # Build nbstripout args as an array (bash 3.1+)
+        args=(--verify)
+
+        if [ "$INPUT_KEEP_OUTPUT" = "true" ]; then
+          args+=(--keep-output)
+        fi
+
+        if [ "$INPUT_KEEP_COUNT" = "true" ]; then
+          args+=(--keep-count)
         fi
-        
-        if [ "${{ inputs.keep-count }}" = "true" ]; then
-          cmd="$cmd --keep-count"
+
+        if [ "$INPUT_STRIP_INIT_CELLS" = "true" ]; then
+          args+=(--strip-init-cells)
         fi
-        
-        if [ "${{ inputs.strip-init-cells }}" = "true" ]; then
-          cmd="$cmd --strip-init-cells"
+
+        if [ -n "$INPUT_EXTRA_KEYS" ]; then
+          args+=(--extra-keys "$INPUT_EXTRA_KEYS")
         fi
-        
-        if [ -n "${{ inputs.extra-keys }}" ]; then
-          cmd="$cmd --extra-keys '${{ inputs.extra-keys }}'"
+
+        # Use Python for file discovery: correct ** glob handling on all platforms
+        # Outputs null-delimited paths and deduplicates overlapping patterns.
+        # INPUT_PATHS is quoted to prevent bash from expanding globs before Python sees them.
+        notebook_list="${RUNNER_TEMP:-/tmp}/nbstripout_filelist.txt"
+
+        python3 - "$INPUT_PATHS" << 'PYTHON' > "$notebook_list"
+        import sys
+        from pathlib import Path
+
+        raw_input = sys.argv[1]
+        patterns = [stripped for line in raw_input.splitlines() if (stripped := line.strip())]
+        seen = set()
+        for pat in patterns:
+            for p in sorted(Path(".").glob(pat)):
+                rp = str(p)
+                if p.is_file() and rp not in seen:
+                    seen.add(rp)
+                    sys.stdout.write(rp + "\0")
+        PYTHON
+
+        if [ ! -s "$notebook_list" ]; then
+          echo "No notebook files found matching: $INPUT_PATHS"
+          exit 0
         fi
-        
-        # Check each notebook
-        failed=0
-        for notebook in ${{ steps.find-notebooks.outputs.notebooks }}; do
-          echo "Checking $notebook..."
-          if ! eval "$cmd $notebook"; then
-            echo "❌ $notebook has output that should be stripped"
-            failed=1
-          else
-            echo "✅ $notebook is properly stripped"
-          fi
-        done
-        
-        if [ $failed -eq 1 ]; then
+
+        # Count null-delimited entries (POSIX-compatible, works on macOS and Linux)
+        notebook_count=$(tr -cd '\0' < "$notebook_list" | wc -c | tr -d ' ')
+        echo "Found $notebook_count notebook(s) to check."
+
+        # xargs -0 reads null-delimited paths (handles any filename characters)
+        # and batches automatically for ARG_MAX safety on large repos
+        if xargs -0 nbstripout "${args[@]}" < "$notebook_list"; then
+          echo "All notebooks are properly stripped! ✅"
+        else
           echo ""
           echo "================================================"
           echo "Some notebooks have output that should be stripped."
@@ -98,5 +104,3 @@ runs:
           echo "================================================"
           exit 1
         fi
-        
-        echo "All notebooks are properly stripped! ✅"
diff --git a/tests/e2e_notebooks/test (nochange).ipynb b/tests/e2e_notebooks/test (nochange).ipynb
new file mode 100644
index 0000000..605c0c7
--- /dev/null
+++ b/tests/e2e_notebooks/test (nochange).ipynb	
@@ -0,0 +1,61 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "This notebook should not be changed by nbstripout."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "1+1 # This cell has `\"init_cell:\" true`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "metadata": {
+    "keep_output": true
+   },
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "4"
+      ]
+     },
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "2+2 # This cell has `\"keep_output:\" true`"
+   ]
+  }
+ ],
+ "metadata": {
+  "celltoolbar": "Edit Metadata",
+  "kernelspec": {
+   "display_name": "Python 2",
+   "language": "python",
+   "name": "python2"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 2
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython2",
+   "version": "2.7.11"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}
diff --git a/tests/e2e_notebooks/test metadata.ipynb b/tests/e2e_notebooks/test metadata.ipynb
new file mode 100644
index 0000000..613ab73
--- /dev/null
+++ b/tests/e2e_notebooks/test metadata.ipynb	
@@ -0,0 +1,101 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "This notebook tests that cells with either `\"keep_output\": true` or `\"init_cell\": true` are not stripped."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {
+    "collapsed": false,
+    "init_cell": true
+   },
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "2"
+      ]
+     },
+     "execution_count": 1,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "1+1 # This cell has `\"init_cell:\" true`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {
+    "collapsed": false,
+    "keep_output": true
+   },
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "4"
+      ]
+     },
+     "execution_count": 2,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "2+2 # This cell has `\"keep_output:\" true`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "6"
+      ]
+     },
+     "execution_count": 3,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "3+3"
+   ]
+  }
+ ],
+ "metadata": {
+  "celltoolbar": "Edit Metadata",
+  "kernelspec": {
+   "display_name": "Python 2",
+   "language": "python",
+   "name": "python2"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 2
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython2",
+   "version": "2.7.11"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}
diff --git a/tests/test_end_to_end.py b/tests/test_end_to_end.py
index 321e64c..2e494c0 100644
--- a/tests/test_end_to_end.py
+++ b/tests/test_end_to_end.py
@@ -21,6 +21,7 @@
     ('test_max_size.ipynb', 'test_max_size.ipynb.expected_sequential_id', ['--max-size', '50']),
     ('test_empty_metadata.ipynb', 'test_empty_metadata.ipynb.expected', []),
     ('test_metadata.ipynb', 'test_metadata.ipynb.expected', []),
+    ('test metadata.ipynb', 'test_metadata.ipynb.expected', []),
     (
         'test_metadata.ipynb',
         'test_metadata_extra_keys.ipynb.expected',
@@ -57,6 +58,7 @@
     ('test_metadata.ipynb', [], True),
     ('test_zeppelin.zpln', ['--mode', 'zeppelin'], True),
     ('test_nochange.ipynb', [], False),
+    ('test (nochange).ipynb', [], False),
 ]
 
 ERR_OUTPUT_CASES = [