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debugging-network-issues

Investigates network, streaming and protocol failures with falsification-first layered experiments, the general fallback for unknown root causes. Use for ECONNRESET / RST_STREAM / SSE stalls, CDN/CGNAT timeouts or certificate errors, throughput collapse where everything returns 200 but transfers crawl, or LAN identity/topology mysteries. Not for known Tailscale/TUN/DNS/proxy-path conflicts (use tunnel-doctor).

debugging-network-issues/SKILL.md

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Network or broad shell
Last checked
Nov 4, 2026

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1,522
Repository last updated
Nov 6, 2026
License
MIT

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# Debugging Network Issues

Evidence-driven investigation methodology for incidents where the obvious cause is probably wrong. Built from a real 5-hour production case (see [references/case-sse-rst-130s.md](references/case-sse-rst-130s.md)) where assumption-stacking wasted hours that a 10-minute layered experiment would have resolved.

Apply this skill when the user reports a network/streaming/protocol symptom and the investigator feels tempted to diagnose from one log line or one circumstantial data point. The skill's job is to slow that reflex down.

## Triage first — is this a known domain?

Before applying the general methodology below, check whether the symptom points at a stack that already has a dedicated skill in this repo. Those carry the domain-specific symptom→cause→fix tables this skill deliberately stays general about — start there, and come back here for methodology if the root cause turns out to be elsewhere.

| If the symptom is…                                                                                                                                                                                       | Start with                                   |
| -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------- |
| macOS Tailscale ⨯ proxy/VPN conflict (Shadowrocket / Clash / Surge): `tailscale ping` works but SSH/curl/git fails, `Connection closed by 198.18.x.x`, TUN DNS hijack, ~60s `getaddrinfo` resolver stall | **tunnel-doctor**                            |
| Cloudflare config: `ERR_TOO_MANY_REDIRECTS`, SSL-mode mismatch, DNS / proxy-status issues behind the orange cloud                                                                                        | **cloudflare-troubleshooting**               |