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 skills add gabrielmoreira/agent-skills-mirror --skill debugging-websocket-issuesgit clone --depth 1 https://github.com/gabrielmoreira/agent-skills-mirrorWrote 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/skills/gabrielmoreira/agent-skills-mirror/debugging-websocket-issues)<a href="https://agentmods.dev/skills/gabrielmoreira/agent-skills-mirror/debugging-websocket-issues"><img src="https://agentmods.dev/badge/skills/gabrielmoreira/agent-skills-mirror/debugging-websocket-issues/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/gabrielmoreira/agent-skills-mirror/debugging-websocket-issues"><img src="https://agentmods.dev/badge/skills/gabrielmoreira/agent-skills-mirror/debugging-websocket-issues.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00054 | $0.01234 |
| Opus 5 | $0.00027 | $0.00617 |
| Sonnet 5 | $0.00011 | $0.00247 |
| Haiku 4.5 | $0.00005 | $0.00123 |
Grade A, and why
debugging-websocket-issues 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 7d 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.
This is a copy
100% identical to debugging-websocket-issues — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 131 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Debugging WebSocket Issues
Overview
WebSocket "invalid frame header" errors often stem from raw HTTP being written to an upgraded socket, not actual frame corruption. The most common cause is multiple WebSocketServer instances conflicting on the same HTTP server.
When to Use
- Error:
Invalid WebSocket frame: RSV1 must be clear - Error:
WS_ERR_UNEXPECTED_RSV_1 - Error:
Invalid frame header - WebSocket connects then immediately disconnects with code 1006
- Server logs success but client receives garbage data
Quick Reference
| Symptom | Likely Cause | Fix |
|---|---|---|
| RSV1 must be clear | Multiple WSS on same server OR compression mismatch | Use noServer: true mode |
Hex starts with 48545450 |
Raw HTTP on WebSocket (0x48='H') | Check for conflicting upgrade handlers |
| Code 1006, no reason | Abnormal closure, often server-side abort | Check abortHandshake calls |
| Works isolated, fails in app | Something else writing to socket | Audit all upgrade listeners |
The Multiple WebSocketServer Bug
Problem
When attaching multiple WebSocketServer instances to the same HTTP server using the server option:
// ❌ BAD - Both servers add upgrade listeners, causing conflicts
const wss1 = new WebSocketServer({ server, path: '/ws' });
const wss2 = new WebSocketServer({ server, path: '/ws/other' });
What happens:
- Client connects to
/ws - BOTH upgrade handlers fire (Node.js EventEmitter calls all listeners)
wss1matches path, handles upgrade successfullywss2doesn't match, callsabortHandshake(socket, 400)- Raw
HTTP/1.1 400 Bad Requestwritten to the now-WebSocket socket - Client receives HTTP text as WebSocket frame data
- First byte
0x48('H') interpreted as: RSV1=1, opcode=8 → invalid frame
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.
- 7d ago First seen · 131 lines · 54 tokens per session scan A 40c5fab7d562
debugging-websocket-issues is a skill published in the GitHub repository gabrielmoreira/agent-skills-mirror (17 stars, last pushed yesterday), licensed MIT. It adds 54 tokens to every session and 1,234 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to debugging-websocket-issues, differing in 0 lines, and is treated as a copy.
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