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 rules/alphabitcore/nexus-gateway/ne-fail-opengit clone --depth 1 https://github.com/AlphaBitCore/nexus-gatewayWrote 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.
[](https://agentmods.dev/rules/alphabitcore/nexus-gateway/ne-fail-open)<a href="https://agentmods.dev/rules/alphabitcore/nexus-gateway/ne-fail-open"><img src="https://agentmods.dev/badge/rules/alphabitcore/nexus-gateway/ne-fail-open.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00000 | $0.00564 |
| Opus 5 | $0.00000 | $0.00282 |
| Sonnet 5 | $0.00000 | $0.00113 |
| Haiku 4.5 | $0.00000 | $0.00056 |
Grade A, and why
ne-fail-open 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 4d 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 — 36 lines — stays where its author put it; the contents beside it link to each section on GitHub.
macOS NE proxy must fail-open (binding, safety-critical)
You are editing NETransparentProxyProvider territory. This code is in the host's outbound packet path. Any hang / panic / silently-claimed-but-not-relayed flow takes down the entire Mac's network — DNS, DHCP, mDNS, NTP, Apple Push, VPNs. Recovery requires launchctl unload + plist delete.
Read docs/developers/architecture/services/agent/agent-ne-fail-open-architecture.md BEFORE editing.
The 5 binding fail-open rules
handleNewFlowdecides synchronously. Onlyreturn truefor flows we can fully relay. UDP without a relay implementation =return falsefor unknown bundles. Apply protocol / bundle-ID checks BEFORE claiming.- Every async callback into the daemon has a fail-open timeout.
requestDecision→ passthrough after 2s.peekSNIThenRelay→ plain relay after 500ms. Never let a flow hang on an absent daemon. - No hardcoded enforcement lists in NE Swift code. Bundle-ID allowlists etc. live in the Hub-pushed
agent_settingsshadow → daemon writes to/var/run/nexus-agent/quic-bundles.json→ NE reads file-only with empty-as-fail-safe. isLikelyXyz = truepatterns are banned. Either write the real condition orreturn false. Don't flip a TODO and ship.- System DNS / DHCP / Push services MUST NEVER have UDP closed.
mdnsresponder,configd,dhcpcd,apsd,nsurlsessiond,kdc,ntpd— validate every kill-list addition.
Test invariants before merging
- Boot on a fresh macOS; verify Wi-Fi browsing works (DNS / DHCP / HTTPS).
- Disable the Hub; verify network still works.
- Send malformed flows (random UDP, unknown TCP); verify nothing hangs.
- Watch QUIC handshake handling; never both pass-through and capture.
- Run 24h on a dev machine; no "did I lose internet?" question.
Build & sign
Use .claude/skills/build-agent (binding). Never run wails build / codesign / xcrun notarytool manually.
Skipping this rule requires explicit user approval in chat.
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.
- 4d ago First seen · 36 lines · 0 tokens per session scan A 2f0f58f3bd80
ne-fail-open is a cursor rule published in the GitHub repository AlphaBitCore/nexus-gateway (23 stars, last pushed 2d ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 564 tokens. 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.
Other cursor rules, from other repositories
10-deterministic-audit
Enforce deterministic audit behavior — no invented controls, cite authoritative sources, emit traceable artifacts.
flagship_author
How to author a flagship in ks-cookbook.
recipe_author
How to author a recipe in ks-cookbook.
30-framework-routing
Route tasks to HIPAA, HITECH, PCI-DSS, SOC 2, ISO 27001, NIST CSF, NIST AI RMF, FERPA, COPPA, CCPA, US state privacy, GDPR, FedRAMP, SOX, CMMC, and GLBA skills based on user intent and presets.
00-compliance-agent-core
Core compliance agent mission, PHI redaction gate, and audit lifecycle for HIPAA, PCI-DSS, and SOC 2.
20-phi-redaction-first
PHI redaction first — Presidio gate, token handling, and minimum necessary LLM access for HIPAA workflows.