/axiom-networking

name: axiom-networking
description: Use when implementing or debugging ANY network connection, API call, or socket in an Apple app. Covers URLSession, Network.framework, NetworkConnection, connection diagnostics.
license: MIT

Networking

**You MUST use this skill for ANY networking work including HTTP requests, WebSockets, TCP connections, or network debugging.**

<!-- AXIOM_AUDITOR_INLINE_BEGIN — rewritten for Codex by scripts/build-codex.ts; do not hand-edit --> > **Auditors are skills here.** Where this router says "Launch `some-auditor` agent", invoke the > matching Codex skill instead — same procedure, no Claude Code agent required. > > Available: `axiom-audit-networking`. > > The ones that shell out — builds, tests, simulators, crash symbolication — need shell access to run. <!-- AXIOM_AUDITOR_INLINE_END -->

Quick Reference

| Symptom / Task | Reference | |----------------|-----------| | URLSession with structured concurrency | See `skills/networking-discipline.md` | | Network.framework anti-patterns | See `skills/networking-discipline.md` | | Deprecated API migration | See `skills/networking-discipline.md` | | gRPC Swift — typed RPC, streaming, `.proto` codegen (WWDC 2026) | See `skills/networking-discipline.md` | | Pressure scenarios (reachability, sockets) | See `skills/networking-discipline.md` | | NetworkConnection (iOS 26+) API reference | See `skills/network-framework-ref.md` | | NWConnection (iOS 12-18) API reference | See `skills/network-framework-ref.md` | | TLV framing, Coder protocol | See `skills/network-framework-ref.md` | | NetworkListener, NetworkBrowser, Wi-Fi Aware | See `skills/network-framework-ref.md` | | Connection timeouts, TLS failures | See `skills/networking-diag.md` | | Data not arriving, connection drops | See `skills/networking-diag.md` | | ATS / HTTP / App Store rejection | See `skills/networking-diag.md` | | Production crisis diagnosis | See `skills/networking-diag.md` | | NWConnection patterns (iOS 12-18) | See `skills/networking-legacy.md` | | UDP batch, NWListener, NWBrowser | See `skills/networking-legacy.md` | | BSD sockets → NWConnection migration | See `skills/networking-migration.md` | | Push/calls on networks without internet (Local Push Connectivity, NEAppPushProvider) | **Use axiom-integration (skills/local-push-connectivity.md)** | | NWConnection → NetworkConnection migration | See `skills/networking-migration.md` | | URLSession StreamTask → NetworkConnection | See `skills/networking-migration.md` |

Decision Tree

digraph networking {
    start [label="Networking task" shape=ellipse];
    what [label="What do you need?" shape=diamond];

    start -> what;
    what -> "skills/networking-discipline.md" [label="implement patterns,\nanti-patterns,\npressure scenarios"];
    what -> "skills/network-framework-ref.md" [label="API reference\n(iOS 26+ or 12-18)"];
    what -> "skills/networking-diag.md" [label="debug connection\nfailures"];
    what -> "skills/networking-legacy.md" [label="iOS 12-18\nNWConnection patterns"];
    what -> "skills/networking-migration.md" [label="migrate from\nsockets/URLSession"];
}

1. URLSession with structured concurrency? → `skills/networking-discipline.md` 2. Network.framework / NetworkConnection (iOS 26+)? → `skills/network-framework-ref.md` 3. NWConnection (iOS 12-18)? → `skills/networking-legacy.md` 4. Migrating from sockets/URLSession? → `skills/networking-migration.md` 5. Connection issues / debugging? → `skills/networking-diag.md` 6. Typed RPC / streaming against a service you control? → gRPC Swift (`skills/networking-discipline.md`) 7. ATS / HTTP / App Store rejection for networking? → `skills/networking-diag.md` + networking-auditor 8. Certificate pinning, signing API requests, encrypting payloads? → `/skill axiom-security` 9. UIWebView or deprecated API rejection? → networking-auditor (Agent) 10. Want deprecated API / anti-pattern scan? → networking-auditor (Agent)

Platform-specific networking

• watchOS low-level-networking limits (TN3135) → See axiom-watchos (skills/background-and-networking.md)

Pressure Resistance

**When user has invested significant time in custom implementation:**

Do NOT capitulate to sunk cost pressure. The correct approach is:

1. **Diagnose first** — Understand what's actually failing before recommending changes 2. **Recommend correctly** — If standard APIs (URLSession, Network.framework) would solve the problem, say so professionally 3. **Respect but don't enable** — Acknowledge their work while providing honest technical guidance

Critical Patterns

**Networking** (`skills/networking-discipline.md`):

• URLSession with structured concurrency
• 8 red-flag anti-patterns (SCNetworkReachability, blocking sockets, hardcoded IPs)
• Decision tree for choosing TCP/UDP/TLS patterns
• NetworkConnection patterns (iOS 26+): TLS, UDP, TLV framing, Coder protocol
• 3 pressure scenarios with professional push-back templates
• Pre-shipping checklist

**Network Framework Reference** (`skills/network-framework-ref.md`):

• NetworkConnection (iOS 26+): all 12 WWDC 2025 examples
• NWConnection (iOS 12-18): complete API with examples
• TLV framing, Coder protocol, NetworkListener, NetworkBrowser
• Mobility: viability, better path, Multipath TCP, NWPathMonitor
• Security: TLS, certificate pinning, cipher suites
• Performance: user-space networking, ECN, service class, TCP Fast Open

**Diagnostics** (`skills/networking-diag.md`):

• Systematic decision tree for all connection failure types
• DNS failures, TLS certificate validation, message framing
• TCP congestion, IPv6-only cellular, VPN interference, ATS
• Production crisis scenario with professional communication templates

**Legacy** (`skills/networking-legacy.md`):

• NWConnection with TLS (completion handlers)
• UDP batch (30% CPU reduction)
• NWListener, NWBrowser (Bonjour discovery)

Automated Scanning

**Networking audit** → `axiom-audit-networking` (deprecated APIs, anti-patterns, and completenes