diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 0384b10..7316fa1 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -9,6 +9,7 @@ repos:
       - id: polymath-general
       - id: polymath-python
       - id: polymath-cpp
+      - id: polymath-ros
       - id: polymath-shell
       - id: polymath-cmake
       - id: polymath-docker
diff --git a/.pre-commit-hooks.yaml b/.pre-commit-hooks.yaml
index 0bbd62b..28e7fc5 100644
--- a/.pre-commit-hooks.yaml
+++ b/.pre-commit-hooks.yaml
@@ -28,6 +28,13 @@
   entry: polymath_code_standard cpp
   types_or: [c, c++]
 
+- <<: *python-hook
+  id: polymath-ros
+  name: Polymath Code Standard [ros]
+  description: Opinionated ROS linting and sanity checks
+  entry: polymath_code_standard ros
+  types_or: [c, c++]
+
 - <<: *python-hook
   id: polymath-shell
   name: Polymath Code Standard [shell]
diff --git a/README.md b/README.md
index 01b73d3..28ae9d9 100644
--- a/README.md
+++ b/README.md
@@ -37,7 +37,7 @@ Feel free to use only the ones that apply to your usage.
 ---
 repos:
   - repo: https://github.com/polymathrobotics/polymath_code_standard
-    rev: v2.1.2
+    rev: v2.2.2
     hooks:
       # Basic checks and fixes that apply to any text file and the git repository itself
       - id: polymath-general
@@ -47,6 +47,7 @@ repos:
       # Specific languages
       - id: polymath-python
       - id: polymath-cpp
+      - id: polymath-ros
       - id: polymath-shell
       - id: polymath-cmake
       - id: polymath-docker
diff --git a/polymath_code_standard/checkers/ros.py b/polymath_code_standard/checkers/ros.py
new file mode 100644
index 0000000..b24eba7
--- /dev/null
+++ b/polymath_code_standard/checkers/ros.py
@@ -0,0 +1,14 @@
+# SPDX-FileCopyrightText: 2026 Polymath Robotics, Inc.
+# SPDX-License-Identifier: Apache-2.0
+import argparse
+
+from polymath_code_standard.checker import CheckerGroup, Result, check_group
+from polymath_code_standard.executor_lint import check_executor_threads
+
+
+@check_group
+class RosGroup(CheckerGroup):
+    name = 'ros'
+
+    def run(self, args: argparse.Namespace) -> list[Result]:
+        return [check_executor_threads(args.files)]
diff --git a/polymath_code_standard/executor_lint.py b/polymath_code_standard/executor_lint.py
new file mode 100644
index 0000000..4f872cb
--- /dev/null
+++ b/polymath_code_standard/executor_lint.py
@@ -0,0 +1,193 @@
+# SPDX-FileCopyrightText: 2026 Polymath Robotics, Inc.
+# SPDX-License-Identifier: Apache-2.0
+"""Require an explicit thread count for multi-threaded rclcpp executors.
+
+A default-constructed MultiThreadedExecutor / EventsCBGExecutor spawns
+``hardware_concurrency()`` threads (one per core).
+Their constructors take ``number_of_threads`` as the 2nd
+positional arg, so a bounded count needs ``Type(rclcpp::ExecutorOptions(), N)``;
+This linter forces ROS users to deliberately choose a thread count.
+This includes passing '0' as an option (which defaults to std::hardware_concurrency)
+so that the max threads are created deliberately
+and not from default construction.
+
+Detection is based on regex + balanced-paren parsing.
+To suppress, use a trailing ``// NOLINT``.
+"""
+
+import re
+from pathlib import Path
+
+from polymath_code_standard.checker import Result
+
+# Executors whose 2nd positional ctor arg is number_of_threads.
+THREADED_EXECUTORS = ('MultiThreadedExecutor', 'EventsCBGExecutor')
+
+_TYPE_RE = re.compile(r'(?:[A-Za-z_]\w*::)*(' + '|'.join(THREADED_EXECUTORS) + r')\b')
+
+
+def _blank(span: str) -> str:
+    """Spaces of equal length to ``span``, with newlines left in place."""
+    return ''.join('\n' if c == '\n' else ' ' for c in span)
+
+
+def _string_end(text: str, start: int) -> int:
+    """Index just past the string/char literal whose opening quote is at ``start``."""
+    quote = text[start]
+    i = start + 1
+    while i < len(text):
+        if text[i] == '\\':  # escape consumes the next char, including a quote
+            i += 2
+        elif text[i] == quote:
+            return i + 1
+        else:
+            i += 1
+    return len(text)
+
+
+def _blank_comments_and_strings(text: str) -> str:
+    """Blank comments and string/char literals to spaces. The result keeps the
+    same length and newline positions as ``text``, so offsets and line numbers
+    computed on it map straight back to the original."""
+    out = []
+    i, n = 0, len(text)
+    while i < n:
+        pair = text[i : i + 2]
+        if pair == '//':
+            end = text.find('\n', i)
+            end = n if end == -1 else end
+        elif pair == '/*':
+            end = text.find('*/', i + 2)
+            end = n if end == -1 else end + 2
+        elif text[i] in '"\'':
+            end = _string_end(text, i)
+        else:
+            out.append(text[i])
+            i += 1
+            continue
+        out.append(_blank(text[i:end]))
+        i = end
+    return ''.join(out)
+
+
+def _skip_ws(text: str, i: int) -> int:
+    while i < len(text) and text[i].isspace():
+        i += 1
+    return i
+
+
+def _parse_arg_list(text: str, open_idx: int) -> list[str] | None:
+    """Top-level comma-split of the bracketed list starting at ``open_idx``.
+
+    Depth is tracked uniformly across (), [] and {} so nested calls like
+    ``ExecutorOptions()`` count as part of one argument. Returns None if the
+    list is unbalanced (parse gave up — caller should not flag)."""
+    depth = 0
+    args: list[str] = []
+    buf: list[str] = []
+    for c in text[open_idx:]:
+        if c in '([{':
+            depth += 1
+            if depth == 1:
+                continue
+            buf.append(c)
+        elif c in ')]}':
+            depth -= 1
+            if depth == 0:
+                tail = ''.join(buf).strip()
+                if args or tail:
+                    args.append(tail)
+                return args
+            buf.append(c)
+        elif c == ',' and depth == 1:
+            args.append(''.join(buf).strip())
+            buf = []
+        else:
+            buf.append(c)
+    return None
+
+
+def find_violations(text: str) -> list[tuple[int, str]]:
+    """Return (1-based line, type name) for each unbounded executor construction."""
+    code = _blank_comments_and_strings(text)
+    violations = []
+    for m in _TYPE_RE.finditer(code):
+        type_name = m.group(1)
+
+        # Skip type aliases — ``typedef X Y;`` / ``using Y = X;`` are not ctors.
+        stmt_start = (
+            max(
+                code.rfind(';', 0, m.start()),
+                code.rfind('{', 0, m.start()),
+                code.rfind('}', 0, m.start()),
+            )
+            + 1
+        )
+        if re.search(r'\b(?:typedef|using)\b', code[stmt_start : m.start()]):
+            continue
+
+        j = _skip_ws(code, m.end())
+        if j >= len(code):
+            continue
+        ch = code[j]
+        args: list[str] | None = None
+        default_ctor = False
+
+        if ch in '({':  # Type(...) / Type{...} temporary or direct init
+            args = _parse_arg_list(code, j)
+        elif ch == '_' or ch.isalpha():  # Type varname ...
+            k = j
+            while k < len(code) and (code[k].isalnum() or code[k] == '_'):
+                k += 1
+            k = _skip_ws(code, k)
+            if k < len(code) and code[k] in '({':
+                args = _parse_arg_list(code, k)
+            elif k < len(code) and code[k] in ';,)=':
+                default_ctor = True  # Type var;  (no initializer)
+            else:
+                continue
+        elif ch == '>':  # make_shared<...Type>( ... )
+            k = _skip_ws(code, j + 1)
+            if k < len(code) and code[k] == '(':
+                args = _parse_arg_list(code, k)
+            else:
+                continue
+        else:
+            continue  # reference / pointer / unrelated token
+
+        if default_ctor:
+            bounded = False
+        elif args is None:
+            continue  # unbalanced — don't risk a false positive
+        else:
+            bounded = len(args) >= 2 and args[1] != ''
+        if not default_ctor and bounded:
+            continue
+
+        line = code.count('\n', 0, m.start()) + 1
+        violations.append((line, type_name))
+    return violations
+
+
+def check_executor_threads(cpp_files: list[str]) -> Result:
+    name = 'executor-threads'
+    if not cpp_files:
+        return Result(name=name, passed=True, skipped=True)
+    findings = []
+    for path in cpp_files:
+        try:
+            text = Path(path).read_text(encoding='utf-8', errors='replace')
+        except OSError:
+            continue
+        src_lines = text.splitlines()
+        for lineno, type_name in find_violations(text):
+            if 0 <= lineno - 1 < len(src_lines) and 'NOLINT' in src_lines[lineno - 1]:
+                continue
+            findings.append(
+                f'{path}:{lineno}: {type_name} constructed without an explicit thread count; '
+                f'pass number_of_threads, e.g. {type_name}(rclcpp::ExecutorOptions(), N) '
+                f'(use // NOLINT to suppress) [executor-threads]'
+            )
+    if findings:
+        return Result(name=name, passed=False, output='\n'.join(findings))
+    return Result(name=name, passed=True)
diff --git a/pyproject.toml b/pyproject.toml
index 7570434..682d3dc 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "polymath-code-standard"
-version = "2.1.2"
+version = "2.2.2"
 description = "Polymath Code Standard pre-commit hooks"
 requires-python = ">=3.10"
 dependencies = [
diff --git a/tests/test_executor_lint.py b/tests/test_executor_lint.py
new file mode 100644
index 0000000..5334ee4
--- /dev/null
+++ b/tests/test_executor_lint.py
@@ -0,0 +1,69 @@
+# SPDX-FileCopyrightText: 2026 Polymath Robotics, Inc.
+# SPDX-License-Identifier: Apache-2.0
+"""Unit tests for the executor thread-count linter."""
+
+import pytest
+
+from polymath_code_standard.executor_lint import check_executor_threads, find_violations
+
+# Constructions that MUST be flagged (no explicit, non-zero thread count).
+FLAGGED = [
+    'rclcpp::executors::MultiThreadedExecutor executor;',
+    'rclcpp::executors::EventsCBGExecutor exec;',
+    'MultiThreadedExecutor executor;',
+    'auto e = rclcpp::executors::MultiThreadedExecutor();',
+    'rclcpp::executors::MultiThreadedExecutor executor(rclcpp::ExecutorOptions());',
+    'auto e = std::make_shared<rclcpp::executors::MultiThreadedExecutor>();',
+    'auto e = new rclcpp::executors::EventsCBGExecutor();',
+    'rclcpp::executors::MultiThreadedExecutor executor{};',
+]
+
+# Constructions and references that MUST NOT be flagged.
+CLEAN = [
+    'rclcpp::executors::MultiThreadedExecutor executor(rclcpp::ExecutorOptions(), 4);',
+    'MultiThreadedExecutor executor(rclcpp::ExecutorOptions(), 0);',
+    'rclcpp::executors::MultiThreadedExecutor executor(rclcpp::ExecutorOptions(), node->getNumThreads());',
+    'auto e = std::make_shared<rclcpp::executors::EventsCBGExecutor>(rclcpp::ExecutorOptions(), 2);',
+    'rclcpp::executors::SingleThreadedExecutor executor;',
+    'void f(rclcpp::executors::MultiThreadedExecutor & exec);',
+    'using Exec = rclcpp::executors::MultiThreadedExecutor;',
+    'typedef rclcpp::executors::MultiThreadedExecutor Exec;',
+    '// rclcpp::executors::MultiThreadedExecutor executor;',
+    'const char * s = "MultiThreadedExecutor executor;";',
+    'rclcpp::executors::MultiThreadedExecutor executor;  // NOLINT(custom)',
+]
+
+
+@pytest.mark.parametrize('src', FLAGGED)
+def test_flagged(src):
+    assert find_violations(src), f'expected a violation for: {src}'
+
+
+@pytest.mark.parametrize('src', CLEAN)
+def test_clean(src):
+    # NOLINT suppression is applied at the file level, so route through check_*.
+    assert not find_violations(src) or 'NOLINT' in src, f'unexpected violation for: {src}'
+
+
+def test_nolint_suppresses(tmp_path):
+    f = tmp_path / 'a.cpp'
+    f.write_text('rclcpp::executors::MultiThreadedExecutor executor;  // NOLINT\n')
+    assert check_executor_threads([str(f)]).passed
+
+
+def test_check_reports_path_and_line(tmp_path):
+    f = tmp_path / 'b.cpp'
+    f.write_text('int main() {\n  rclcpp::executors::MultiThreadedExecutor exec;\n}\n')
+    result = check_executor_threads([str(f)])
+    assert not result.passed
+    assert f'{f}:2:' in result.output
+
+
+def test_multiline_ctor_with_threads_is_clean(tmp_path):
+    f = tmp_path / 'c.cpp'
+    f.write_text('rclcpp::executors::MultiThreadedExecutor exec(\n    rclcpp::ExecutorOptions(),\n    4);\n')
+    assert check_executor_threads([str(f)]).passed
+
+
+def test_empty_file_list_skipped():
+    assert check_executor_threads([]).skipped
diff --git a/tests/test_runner.py b/tests/test_runner.py
index b6e8b8f..524ec34 100644
--- a/tests/test_runner.py
+++ b/tests/test_runner.py
@@ -51,6 +51,7 @@ def test_all_groups_registered():
         'general',
         'python',
         'cpp',
+        'ros',
         'shell',
         'cmake',
         'docker',
@@ -82,6 +83,12 @@ def test_cpp(make_project_file):
     assert runner.main(['cpp', f]) == 0
 
 
+def test_ros(make_file):
+    content = 'rclcpp::executors::MultiThreadedExecutor executor(rclcpp::ExecutorOptions(), 4);\n'
+    f = make_file('example.cpp', content)
+    assert runner.main(['ros', f]) == 0
+
+
 def test_shell(make_file):
     f = make_file('example.sh', '#!/bin/bash\necho "hello"\n')
     assert runner.main(['shell', f]) == 0
diff --git a/uv.lock b/uv.lock
index 6ab5489..afd91e7 100644
--- a/uv.lock
+++ b/uv.lock
@@ -801,7 +801,7 @@ wheels = [
 
 [[package]]
 name = "polymath-code-standard"
-version = "2.1.2"
+version = "2.2.2"
 source = { editable = "." }
 dependencies = [
     { name = "ansible-lint" },