Networking

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

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.

Quick Reference

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 completeness gaps — transition handling, TLS coverage, connection cleanup, framework selection)

Anti-Rationalization

Example Invocations

User: "My API request is failing with a timeout" → Read: skills/networking-diag.md

User: "How do I use URLSession with async/await?" → Read: skills/networking-discipline.md

User: "I need to implement a TCP connection" → Read: skills/network-framework-ref.md

User: "Should I use NWConnection or NetworkConnection?" → Read: skills/network-framework-ref.md

User: "My app was rejected for using HTTP connections" → Read: skills/networking-diag.md (ATS compliance)

User: "App Store says I'm using UIWebView" → Invoke: networking-auditor agent (deprecated API scan)

User: "Check my networking code for deprecated APIs" → Invoke: networking-auditor agent