Guidance for running Zephyr RTOS applications on a regular computer through its native_sim board. It lets Linux, macOS, or Windows act as a test machine instead of requiring embedded hardware.

Use it to build and run host simulations, debug them with GDB or Valgrind, and run automated native_sim tests in CI/CD, the systems that check code automatically.

It helps test application logic and investigate failures earlier, while avoiding the need to connect physical hardware for every build or test.

native-sim — Skill for Claude Code and Codex by beriberikix

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo

git clone --depth 1 https://github.com/beriberikix/zephyr-agent-skills

agentmods

npx agentmods add skills/beriberikix/zephyr-agent-skills/native-sim

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/beriberikix/zephyr-agent-skills/native-sim/github.svg)](https://agentmods.dev/skills/beriberikix/zephyr-agent-skills/native-sim)

Your own site

<a href="https://agentmods.dev/skills/beriberikix/zephyr-agent-skills/native-sim"><img src="https://agentmods.dev/badge/skills/beriberikix/zephyr-agent-skills/native-sim/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/beriberikix/zephyr-agent-skills/native-sim"><img src="https://agentmods.dev/badge/skills/beriberikix/zephyr-agent-skills/native-sim.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 57 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 550 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00057	$0.00550
Opus 5	$0.00028	$0.00275
Sonnet 5	$0.00011	$0.00110
Haiku 4.5	$0.00006	$0.00055

Measured 9d ago against content hash c599843e5a35, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

native-sim scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/native_log_scan.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/native-sim/SKILL.md · 60 lines

What it actually says

Zephyr Native Simulation

Develop, test, and debug Zephyr applications with the speed and convenience of your host machine.

Core Workflows

1. Simulation Basics

Understand when to use native_sim vs. QEMU and how to map host resources.

Reference: simulation_basics.md
Key Tools: west build -b native_sim.

2. Host-Side Debugging

Use professional host tools to find the most elusive bugs.

Reference: debugging.md
Key Tools: gdb, valgrind, gprof, pcap.

3. Automated Testing (CI/CD)

The foundation of modern firmware development.

Reference: See the testing-debugging skill (Phase 3) for comprehensive testing workflows.
Key Tools: twister -p native_sim.

Quick Start

# Build for host
west build -b native_sim samples/hello_world

# Run the app
./build/zephyr/zephyr.exe

# Debug with GDB
west debug

Automation Tools

native_log_scan.py: Scan native simulation logs for common crash/failure signatures.

Examples & Templates

native_sim_ci_checklist.md: Starter checklist for CI simulation coverage.

Validation Checklist

west build -b native_sim succeeds for at least one sample and one app target.
Built binary runs on host and emits expected startup logs.
Host debugger (GDB/Valgrind) can attach and surface expected symbols.
Simulation test path is integrated into CI (for example Twister native_sim run).

Resources

References:
- simulation_basics.md: Architectural overview and usage patterns.
- debugging.md: GDB, Valgrind, and profiling guide.
Scripts:
- native_log_scan.py: Failure signature scanner for native_sim logs.
Assets:
- native_sim_ci_checklist.md: CI simulation review checklist.

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

9d ago First seen · 60 lines · 57 tokens per session scan A c599843e5a35

Subscribe to this mod's changes

native-sim is a skill published in the GitHub repository beriberikix/zephyr-agent-skills (63 stars, last pushed 3mo ago), licensed Apache-2.0. It adds 57 tokens to every session and 550 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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