Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/cmdr-chara/codex-toolkit/expo-react-native-buildernpx skills add cmdr-chara/codex-toolkit --skill expo-react-native-buildergit clone --depth 1 https://github.com/cmdr-chara/codex-toolkitWhat 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 | $0.00092 | $0.02644 |
| Opus 5 | $0.00046 | $0.01322 |
| Sonnet 5 | $0.00018 | $0.00529 |
| Haiku 4.5 | $0.00009 | $0.00264 |
Grade A, and why
expo-react-native-builder 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 2d ago.
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.
How it starts
The opening of the file, as written. The whole thing — 211 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Expo React Native Builder
Build against the selected Expo SDK and React Native architecture, real devices, native constraints, and store/update policy. Prefer Expo/RN capabilities and existing repository choices before dependencies.
Trigger boundary
Use this skill for:
- implementing an Expo/React Native app or feature;
- auditing routing, native modules, data/offline, performance, accessibility, EAS, and release readiness;
- choosing state/data/storage/animation/test packages conditionally within an established Expo/RN app;
- upgrading implementation patterns within the current supported SDK without changing the platform decision.
Do not trigger for:
- deciding Expo/RN versus Flutter/native—use
mobile-architecture-director; - a web-only React task;
- a bare React Native migration or SDK upgrade whose central problem is version compatibility—use
codebase-evolution-controllerwith this skill as implementation guidance; - treating Expo Go as the production development/runtime environment.
Required inputs
Capture:
- repository state, Expo SDK/RN/React/Node/package-manager versions and monorepo shape;
- app config, routes, development build, native directories/prebuild policy, EAS build/update/submit profiles;
- product/design flows, platform conventions, accessibility/localization requirements;
- backend/auth/data/offline/sync and sensitive-data contracts;
- native modules/device APIs, permissions, extensions/widgets/background needs;
- supported OS/devices, performance/resource targets, and real-device matrix;
- testing, CI, observability, signing/store, update runtime, rollout, and rollback policy.
Inventory first:
python skills/expo-react-native-builder/scripts/expo_project_inventory.py . --format markdown
Safety baseline
- Inspect and preserve uncommitted work.
- Read
package.json, lockfile, app config,eas.json, native projects, config plugins, and existing architecture before edits. - Use
npx expo installor repository tooling for SDK-compatible Expo package resolution when authorized; do not force arbitrary versions. - Do not run prebuild, install pods, regenerate native projects, or upgrade SDK/RN without reviewing expected native diffs and rollback.
- Never ship secrets in
EXPO_PUBLIC_*, app config, JS bundle, AsyncStorage, logs, updates, or source maps. - Test native modules, storage, biometrics, notifications, background, links, memory, and performance in development/release builds on real devices.
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.
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.
- 2d ago First seen · 211 lines · 92 tokens per session scan A cbaa46d31f99
expo-react-native-builder is a skill published in the GitHub repository cmdr-chara/codex-toolkit (2 stars, last pushed 5d ago), licensed MIT. It adds 92 tokens to every session and 2,644 once invoked, about $0.0005 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 2026-08-31.
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