lltx/network-doctor

Network Doctor

Use this skill to diagnose and improve local network performance without guessing or making unsafe system changes.

Scope

Handle:

• Slow internet speed, unstable latency, packet loss, DNS delay, MTU symptoms
• Wi-Fi signal/interference problems
• VPN, proxy, split tunnel, firewall, or filtering conflicts
• Background processes consuming bandwidth
• Stale network locations/profiles and mDNS oddities
• Windows TCP auto-tuning only when the user explicitly says Windows

Do not handle:

• General Mac slowness, browser slowness, local LLM speed, disk cleanup, app crashes
• Router admin changes unless the user explicitly asks and provides access
• Production network, office network, cloud infrastructure, or shared enterprise devices without explicit authorization

Required Workflow

1. Read references/safety.md.
2. Classify the symptom before running commands:
   • Bandwidth: low Mbps or unstable throughput
   • Latency: high ping, jitter, video call lag, game lag
   • DNS: websites pause before loading, IP ping is fine
   • Wi-Fi/LAN: bad signal, far from router, roaming, interference
   • VPN/proxy: only some sites slow, domestic/overseas split is wrong
   • MTU/TCP: stalls, large downloads hang, VPN-specific breakage
   • Background traffic: uploads/sync/downloads consume bandwidth
3. Read references/diagnostic-playbook.md.
4. If the machine is macOS, read references/commands-macos.md.
5. Establish a before baseline before proposing changes.
6. Make findings evidence-led. Use [VERIFIABLE] for measured facts and [JUDGMENT 高/中/低] for interpretation.
7. Separate actions into:
   • Safe read-only checks already run
   • Low-risk reversible actions
   • Risky actions requiring explicit confirmation
   • Actions to reject
8. Change only one variable per pass.
9. Run the same verification after each change.
10. Use references/report-template.md for the final response.

Command Policy

Allowed by default:

• Read-only diagnostics such as networkQuality, ping, scutil --dns, ifconfig, route, netstat, ps
• Speed or latency tests that do not modify system state

Require explicit user confirmation:

• Killing or throttling processes
• Flushing DNS cache
• Restarting mDNSResponder
• Changing DNS, MTU, proxy, VPN, firewall, TCP parameters, network service order, or network location
• Deleting stale profiles or locations
• Router or modem changes
• Any command requiring sudo

Reject unless the user gives a narrow, reversible reason:

• Bulk deletion of network settings
• Disabling security tools blindly
• Random "optimization" commands from the internet
• Multiple simultaneous changes that make before/after verification meaningless

Output Standard

Always give the user:

• What was tested
• What changed, if anything
• What the evidence says
• What remains unknown
• The exact before/after metrics
• Rollback steps for every modification

When the user wants a prompt to reuse, provide a compact /goal style prompt that includes constraints: read-only first, no unsafe changes, one change per pass, rollback, before/after test.