---

name: ros2-engineering-skills description: > TRIGGER when the user: writes or reviews ROS 2 nodes (rclcpp/rclpy), creates packages (colcon/ament), edits launch files (.launch.py), configures QoS or DDS, writes URDF/xacro, implements ros2_control hardware interfaces or controllers, sets up Nav2/MoveIt 2 pipelines, processes sensor data (camera/LiDAR/PCL), works with Gazebo/Isaac Sim, configures SROS2 security, develops micro-ROS firmware, manages multi-robot fleets (Open-RMF), debugs with ros2 doctor/rosbag2, deploys via Docker/cross-compilation, or migrates from ROS 1. DO NOT TRIGGER for general C++/Python questions unrelated to ROS 2, non-robotics middleware, or web/mobile development tasks. context: fork classification: capability category: api-reference version: 1.2.0 deprecation-risk: medium

The hooks block below is Claude Code-specific: the hook schema, the

${CLAUDE_PLUGIN_ROOT} path variable, and the tool-name matcher are not

part of the Agent Skills standard. Other platforms (Codex, Cursor,

Gemini CLI) ignore this block — see "Platform support" in the body for

the manual fallback.

hooks: PreToolUse: # Matcher = Claude Code's file-mutation and shell tools. - matcher: "Edit|Write|MultiEdit|Bash" hooks: - type: command # timeout is in SECONDS (not milliseconds). The command-hook # default is 600 s; these validators are local file scans that # finish in well under a second. command: "python3 ${CLAUDE_PLUGIN_ROOT}/scripts/skill_validate_hook.py" timeout: 10 Stop: - hooks: - type: command command: "python3 ${CLAUDE_PLUGIN_ROOT}/scripts/skill_stop_hook.py" timeout: 15

Eval definitions live in evals/eval.yaml (single source of truth).

---

ROS 2 Engineering Skills

Single responsibility: This skill is an API reference & code template guide for ROS 2 development. It tells you how to use ROS 2 APIs correctly and what mistakes to avoid. It does NOT do CI/CD orchestration, incident response, data analysis, or deployment automation — those are separate skill categories.

A progressive-disclosure skill for ROS 2 development — from first workspace to production fleet deployment. Detailed patterns and code templates live in references/; read the relevant file before writing code.

How to use this skill

This always-loaded file carries routing, core principles, pitfalls, and anti-patterns — enough for quick questions and architectural decisions. For implementation work, use the Decision Router below to load the reference file(s) matching the task; the AI pitfalls table lists mistakes worth re-checking before generating code. scripts/ are tools to run (scaffolding, QoS checking, launch validation), not reading material. When domains intersect (e.g. Nav2 + ros2_control) and recommendations conflict, favor safety > determinism > simplicity.

Execution log (opt-in): When the Stop hook runs (Claude Code only) and the SKILL_RUNS_LOG environment variable is set, a session summary is appended to .skill-runs.log. If that file exists in the workspace, read the last few lines to avoid repeating past mistakes. Without the opt-in — and on platforms without hooks — the file is never created, so a read-only session leaves the working tree untouched.

Platform support: SKILL.md and references/ are platform-neutral knowledge documents. scripts/ can be run manually on any platform whose environment has Python and the repository dependencies. The hook wiring (automatic execution) and .skill-runs.log are Claude Code-specific; on other platforms run the validators manually from the skill root: SKILL_WORKSPACE=<dir> python3 scripts/skill_stop_hook.py and python3 scripts/skill_validate_hook.py --file <src> / --command '<cmd>' (the command string is inspected only, never executed; without those flags the validate hook expects a Claude Code PreToolUse payload and checks nothing on its own).

Decision router

User is doing...	Read
Creating a workspace, package, or build config	references/workspace-build.md
Writing nodes, executors, callback groups	references/nodes-executors.md
Topics, services, actions, custom interfaces, QoS	references/communication.md
Lifecycle nodes, component loading, composition	references/lifecycle-components.md
Launch files, conditional logic, event handlers	references/launch-system.md
tf2, URDF, xacro, robot_state_publisher	references/tf2-urdf.md
ros2_control, hardware interfaces, controllers	references/hardware-interface.md
Real-time constraints, PREEMPT_RT, memory, jitter	references/realtime.md
Nav2, SLAM, costmaps, behavior trees	references/navigation.md
MoveIt 2, planning scene, grasp pipelines	references/manipulation.md
Camera, LiDAR, PCL, cv_bridge, depth processing	references/perception.md
Sensor drivers, clock sync, LiDAR-camera extrinsics	references/sensor-integration.md
Unit tests, integration tests, launch_testing, CI	references/testing.md
ros2 doctor, tracing, profiling, rosbag2, CLI cheat sheet	references/debugging.md
Docker, cross-compile, fleet deployment, OTA	references/deployment.md
System bringup, udev rules, boot sequence, watchdogs	references/system-bringup.md
Gazebo, Isaac Sim, sim-to-real, use_sim_time	references/simulation.md
SROS2, DDS security, certificates, supply chain	references/security.md
E-stop, safety chains, command arbitration	references/safety-estop.md
micro-ROS, MCU/RTOS, XRCE-DDS, rclc	references/micro-ros.md
Multi-robot fleet, Open-RMF, DDS discovery scale	references/multi-robot.md
Message types, units, covariance, frame conventions	references/message-types.md
ROS 1 migration, ros1_bridge, hybrid operation	references/migration-ros1.md

Cross-cutting concerns: Security, error handling, and QoS are not isolated to single reference files — use your judgment and apply them whenever the data path crosses a trust boundary, a node owns hardware, or communication reliability matters.

Core engineering principles

These apply to every ROS 2 artifact you produce, regardless of domain.

1. Distro awareness

Staleness warning: The table below was last verified on 2026-07-15. If the current date is more than 6 months past that, re-verify EOL dates and feature support against https://docs.ros.org/en/rolling/Releases.html before relying on this table. When you update it, change both LAST_UPDATED and NEXT_REVIEW comments above.

Identify which ROS 2 distribution the user targets — from the workspace (Dockerfile, CI config, /opt/ros/<distro>) when possible, or by asking when it is not inferable. Key differences:

Feature	Humble (LTS)	Jazzy (LTS)	Kilted (non-LTS)	Lyrical (LTS)	Rolling
EOL	May 2027	May 2029	Dec 2026	May 2031	Rolling
Ubuntu	22.04	24.04	24.04	26.04	Latest
Default DDS	Fast DDS	Fast DDS	Fast DDS	Fast DDS	Fast DDS
Zenoh support	—	—	Tier 1	Tier 1	Tier 1
Type description support	No	Yes	Yes	Yes	Yes
Service introspection	No	Yes	Yes	Yes	Yes
EventsExecutor	No	Experimental	Experimental (+ rclpy port)	EventsCBGExecutor (non-experimental, rclcpp)	Verify installed rclcpp
Default bag format	sqlite3	MCAP	MCAP	MCAP	MCAP
ros2_control interface	2.x	4.x	5.x	6.x (verify installed)	Latest
CMake recommendation	ament_target_deps	either	target_link_libs	target_link_libs	target_link_libs

Foxy (EOL June 2023, Ubuntu 20.04, ros2_control not bundled) is a migration reference only — see the migration notes below. The pre-Lyrical EventsExecutor lives in the rclcpp::experimental namespace on every release that ships it; Lyrical adds the separate, non-experimental rclcpp::executors::EventsCBGExecutor.

When the user does not specify, default to the latest LTS — Lyrical Luth (Ubuntu 26.04); use Jazzy when the target platform is Ubuntu 24.04. Pin the exact distro in Dockerfile, CI, and documentation so builds are reproducible.

2. C++ vs Python decision

Choose the language based on the node's role, not personal preference. rclcpp (C++): control loops ≥100 Hz, deterministic memory allocation (real-time path), hardware drivers and controller plugins, intra-process zero-copy. rclpy (Python): orchestration, monitoring, parameter management, rapid prototyping, Python-native ML frameworks — anything off the latency-critical path.

Mixed stacks are normal. A typical robot has C++ drivers/controllers and Python orchestration/monitoring. Note: component_container (composition) only loads C++ components via pluginlib. Python nodes run as separate processes and communicate over intra-host DDS — not zero-overhead by default: the standard inter-process transport pays serialization, copies, and transport bandwidth, and splitting work into another process does not by itself remove encoding costs. Copy avoidance has three distinct mechanisms with different preconditions: (1) the rclcpp intra-process path (use_intra_process_comms(true), same process) avoids copies only depending on publish ownership (unique_ptr), callback type, subscriber count, and QoS; (2) loaned messages / vendor shared memory (SHM/PSMX) are RMW- and vendor-dependent and can avoid some or all copies when their preconditions hold; (3) separate processes on the standard DDS transport get no copy avoidance — crossing processes without copies requires the vendor mechanisms in (2). Details: references/nodes-executors.md.

3. Package structure conventions

Follow the standard layout — package.xml (format 3, explicit <depend> tags), config/params.yaml, launch/*.launch.py, src/ + include/<pkg>/ for C++ or <pkg>/ for Python, and test/. Keep custom msg/srv/action definitions in a dedicated *_interfaces package so downstream packages can depend on interfaces without the implementation. Full annotated layout: references/workspace-build.md.

4. Parameter discipline

• Declare every parameter with a type, description, range, and default in the node constructor — never use undeclared parameters.
• Use ParameterDescriptor with FloatingPointRange or IntegerRange for numeric bounds. The parameter server rejects out-of-range values at set time.
• Group related parameters under a namespace prefix: controller.kp, controller.ki, controller.kd.
• Load defaults from a config/params.yaml; allow launch-time overrides.
• For dynamic reconfiguration, register a set_parameters_callback and validate new values atomically before accepting.

5. Error handling philosophy

• Nodes must not silently swallow errors. Log at the appropriate severity, then take a safe action (stop motion, request help, transition to error state).
• Prefer lifecycle node error transitions over ad-hoc boolean flags.
• When calling a service, always handle the "service not available" and "future timed out" cases explicitly.
• For hardware drivers, distinguish transient errors (retry with backoff) from fatal errors (transition to FINALIZED and alert the operator).

6. Quality of Service defaults

Start from these profiles and adjust per use case:

Use case	Reliability	Durability	History	Depth	Deadline	Lifespan
Sensor stream	BEST_EFFORT	VOLATILE	KEEP_LAST	5	—	—
Command velocity	RELIABLE	VOLATILE	KEEP_LAST	1	100 ms	200 ms
Map (latched)	RELIABLE	TRANSIENT_LOCAL	KEEP_LAST	1	—	—
Diagnostics	RELIABLE	VOLATILE	KEEP_LAST	10	—	—
Parameter events	RELIABLE	VOLATILE	KEEP_LAST	1000	—	—
Action feedback	RELIABLE	VOLATILE	KEEP_LAST	1	—	—
Safety heartbeat	RELIABLE	VOLATILE	KEEP_LAST	1	500 ms	1 s

QoS mismatches are the #1 cause of "I published but nobody receives." Always check compatibility with ros2 topic info -v when debugging.

DEADLINE and LIFESPAN are critical for safety-critical systems. DEADLINE fires an event when no message arrives within the specified period (detect stale data). LIFESPAN discards messages older than the specified duration before delivery (prevent acting on stale data). See references/communication.md section 9 for full API and examples.

7. Naming conventions

Entity	Convention	Example
Package	snake_case	arm_controller
Node	snake_case	joint_state_broadcaster
Topic	/snake_case with ns	/arm/joint_states
Service	/snake_case	/arm/set_mode
Action	/snake_case	/arm/follow_joint_trajectory
Parameter	snake_case with dot ns	controller.publish_rate
Frame	snake_case	base_link, camera_optical
Interface	PascalCase.msg/srv/action	JointState.msg

8. Thread safety and callbacks

• A MutuallyExclusiveCallbackGroup serializes its callbacks — safe for shared state without locks, but limits throughput.
• A ReentrantCallbackGroup allows parallel execution — you must protect shared state with std::mutex (C++) or threading.Lock (Python).
• Calling a service from a callback: If the callback registers the request asynchronously — rclcpp: async_send_request(request, response_callback); rclpy: future = client.call_async(request) then future.add_done_callback(...) — and returns without waiting for the result, the same MutuallyExclusiveCallbackGroup does not deadlock. Deadlock comes from waiting synchronously inside the callback — rclcpp: calling get()/wait()/wait_for() on a not-yet-complete future from the initiating callback, or spin_until_future_complete (inside the response callback the future is already complete, so get() there is safe — the examples use exactly that); rclpy: synchronous Client.call(), spin_until_future_complete, or a loop that blocks until future.done(). (rclpy's future.result() by itself does not block — it immediately returns whatever result is currently stored, which may be unset.) A synchronous wait needs the client in a different callback group or a ReentrantCallbackGroup, plus a matching executor configuration (e.g. MultiThreadedExecutor). Do not assume plain-executor async def callback patterns are safe until tested with your executor; Lyrical's rclpy.experimental.AsyncNode is a separate execution model that officially supports await client.call(...) inside callbacks.
• Never do blocking work (file I/O, long computation, sleep) inside a timer or subscription callback on the default executor. Offload to a dedicated thread or use a MultiThreadedExecutor with a reentrant group.
• In rclcpp, prefer std::shared_ptr<const MessageT> in subscription callbacks to avoid unnecessary copies; whether intra-process delivery is actually copy-free additionally depends on publish ownership, subscriber count, and QoS (Principle 2).

9. Lifecycle-first design

Default to lifecycle (managed) nodes for anything that owns resources: hardware drivers, sensor pipelines, planners, controllers. The managed state machine (unconfigured → inactive → active, with cleanup, shutdown, and error transitions) gives the system manager explicit control over when resources are allocated, when processing starts, and how shutdown proceeds — and makes error recovery predictable. Configure-only transitions also enable hardware-safe config validation (references/testing.md section 4). Full state diagram and callbacks: references/lifecycle-components.md.

10. Build and CI hygiene

• Use colcon build --cmake-args -DCMAKE_BUILD_TYPE=RelWithDebInfo for development; Release for deployment.
• Enable -Wall -Wextra -Wpedantic and treat warnings as errors in CI.
• Run colcon test with --event-handlers console_cohesion+ so test output groups by package.
• Pin rosdep keys in rosdep.yaml for reproducible dependency resolution.
• Cache /opt/ros/, .ccache/, and build//install/ in CI to cut build times by 60–80%.

11. Source-first behavior verification

Distro labels are not enough when exact behavior matters — patch releases change parameter names, plugin behavior, and defaults. Before asserting how an installed stack behaves, identify the installed version (ros2 pkg xml, dpkg-query -W) and read what ships with it: reference configs, headers, and the source tag matching that version. Worked Nav2 procedure: references/navigation.md section 6.

12. Motion-safety defaults

Never generate configs that can move an unvalidated robot. Motion recoveries (Spin/BackUp) stay opt-in until robot geometry, locomotion response, and clearance are validated — actuation-free recovery comes first. Velocity limits come from the safe operational ceiling, never the SDK/API maximum. For hardware checks, prefer configure-only lifecycle validation with hardware isolation (references/testing.md section 4). Details: references/navigation.md sections 7 and 10.

Common anti-patterns

Anti-pattern	Why it hurts	Fix
Global variables for node state	Breaks composition, untestable	Store state as class members
spin() in main() for multi-node processes	Starves other nodes	Use MultiThreadedExecutor or component composition
Hardcoded topic names	Breaks reuse across robots	Use relative names + namespace remapping
KEEP_ALL history with no bound	Memory grows unbounded on slow subscribers	Use KEEP_LAST with explicit depth
Using time.sleep() / std::this_thread::sleep_for	Blocks the executor thread	Use create_wall_timer or a dedicated thread
Monolithic launch file for everything	Unmanageable past 10 nodes	Compose launch files with IncludeLaunchDescription
Skipping package.xml dependencies	Builds locally, breaks CI and Docker	Declare every dependency explicitly
Publishing in constructor	Subscribers may not be ready, messages lost	Publish in on_activate or after a short timer
Ignoring QoS compatibility	Silent communication failure	Match publisher/subscriber QoS or check with ros2 topic info -v
Creating timers/subs in callbacks	Resource leak, unpredictable behavior	Create all entities in constructor or on_configure
Synchronous service call in callback	Deadlocks the executor thread	Use async_send_request with a callback or dedicated thread
Waiting on a service future inside a callback	Synchronous waiting deadlocks a MutuallyExclusiveCallbackGroup; registering a response callback and returning is safe even in the same group	Return without waiting; if a synchronous wait is unavoidable, put the client in a different group (or reentrant) with a MultiThreadedExecutor
No safe command on shutdown	Motors hold last velocity after node exits	Send zero-velocity in on_deactivate and the destructor as best-effort hygiene; crash safety needs a downstream command timeout/watchdog (references/safety-estop.md)
Dynamic subscriptions with StaticSingleThreadedExecutor	New subs are never picked up after spin()	Use SingleThreadedExecutor or MultiThreadedExecutor for dynamic entities
CPU frequency governor left on powersave/ondemand	10-100 ms latency spikes in RT path	Set performance governor, disable turbo boost (see references/realtime.md)

AI pitfalls — traps this skill has learned from

These are mistakes AI agents repeatedly make when generating ROS 2 code. Add a new line here every time a failure is discovered in practice.

#	Pitfall	What goes wrong	Correct approach
1	Using spin_until_future_complete inside a callback	Deadlocks the executor — the callback blocks waiting for a response that can never be delivered	Register a response callback and return without waiting; a separate callback group (or reentrant + MultiThreadedExecutor) is needed only when a synchronous wait is unavoidable
2	Generating Foxy-era API for Jazzy/Kilted	node_executable is deprecated, export_state_interfaces() signature changed in ros2_control 4.x	Always check the distro feature matrix above before generating code
3	Omitting QoS in publisher/subscriber creation	Defaults silently mismatch — publisher sends but subscriber receives nothing	Always specify QoS explicitly; use the QoS defaults table in Principle 6
4	Creating a msg/ directory inside a non-interfaces package	Builds locally but fails in CI — interface packages need rosidl_generate_interfaces	Put messages in a dedicated *_interfaces package
5	Hardcoding /opt/ros/humble/ paths in launch files	Breaks on any other distro or install prefix	Use FindPackageShare, PathJoinSubstitution, or environment substitutions
6	Forgetting <depend> tags in package.xml	colcon build works in overlay but rosdep install and Docker builds fail	Declare every find_package() / import as <depend> in package.xml
7	Using time.sleep() for rate control in rclpy	Blocks the executor thread; timers and subscriptions stop firing	Use create_timer() or Rate with a MultiThreadedExecutor
8	Treating process-side cleanup as crash safety	Destructors never run on SIGKILL/power loss and are not guaranteed on segfaults — the robot keeps its last command	Zero-command in on_deactivate + destructor is best-effort hygiene only; require a downstream command timeout, heartbeat/watchdog, and hardware e-stop (references/safety-estop.md)
9	Mixing ament_target_dependencies() and target_link_libraries()	Kilted deprecated ament_target_dependencies — mixing causes link errors	Use target_link_libraries() with modern CMake targets for Kilted+; ament_target_dependencies() for Humble/Jazzy
10	Generating rospy / roscpp code instead of rclpy / rclcpp	ROS 1 patterns in a ROS 2 context — nothing compiles	This skill is ROS 2 only — always use rclpy/rclcpp APIs
11	Ignoring use_sim_time parameter in simulation	Real clock diverges from Gazebo clock — tf lookups fail, controllers drift	Set use_sim_time:=true in launch and pass --clock to ros2 bag play
12	Publishing before subscribers connect (no TRANSIENT_LOCAL)	First N messages lost — map, URDF, or initial config never received	Use TRANSIENT_LOCAL durability for latched-style data, or publish in on_activate with a startup delay
13	Writing Nav2 names from memory (recoveries_server/nav2_recoveries/ on Humble, pre-Galactic default_bt_xml_filename)	Parameters silently ignored or plugin loading fails at configure	Humble+ uses behavior_server/nav2_behaviors/ and default_nav_to_pose_bt_xml; verify against the installed version (Principle 11)
14	Enabling Spin/BackUp recoveries by default on an unvalidated robot	Robot suddenly rotates or reverses in the field — the recovery, not path following, is at fault	Motion recoveries are opt-in after validation; actuation-free recovery first (Principle 12)

Maintenance rule: When you encounter a new AI failure pattern while using this skill, append it to this table with the next sequential number. The pitfall list is the single most valuable section for preventing repeated mistakes.

Distro-specific migration notes

When upgrading between distributions, check these breaking changes first:

• Foxy → Humble: complete API overhaul (lifecycle, actions stabilized in Humble); ros2_control was not bundled in Foxy; Nav2 renamed recoveries_server → behavior_server and nav2_recoveries/ → nav2_behaviors/ (Galactic → Humble migration — pre-Humble recovery naming does not exist on Humble). Plan a rework, not a port.
• Humble → Jazzy: ros2_control 2.x → 4.x — interface exports auto-generated, get_value() → get_optional<T>(), spawner uses --param-file, all <ros2_control> joints must exist in the URDF (details: references/hardware-interface.md); default bag format sqlite3 → MCAP (storage_id='mcap'); ROS_AUTOMATIC_DISCOVERY_RANGE replaces ROS_LOCALHOST_ONLY; launch_ros parameter handling changed — retest launch files.
• Jazzy → Kilted (non-LTS): Zenoh Tier 1 (RMW_IMPLEMENTATION=rmw_zenoh_cpp); experimental EventsExecutor gains an rclpy port (still rclcpp::experimental); ament_target_dependencies() deprecated — use target_link_libraries() with modern CMake targets; Gazebo pairing is Ionic (Harmonic was Jazzy); multi-bag replay in ros2 bag play.
• Kilted → Lyrical (LTS): primary platform moves to Ubuntu 26.04; default RMW stays rmw_fastrtps_cpp; new non-experimental rclcpp::executors::EventsCBGExecutor (distinct from the experimental EventsExecutor); ros2_control moves to the 6.x series — verify per-package changes against the installed versions (Principle 11).
• ROS 1 → ROS 2: see references/migration-ros1.md for a step-by-step strategy.

Quick reference — ros2 CLI

See references/debugging.md §10 "Quick CLI reference" for the full command cheat sheet (workspace, introspection, ros2_control, debugging, lifecycle). Kept out of this always-loaded file to preserve context budget.