What is connecting-securely?

A set of instructions for connecting securely to the Yale SOM HPC cluster, a shared system for running larger computing jobs. It covers SSH keys, connection reuse, jump hosts, and tunnels for tools such as VS Code or Jupyter.

Use it when logging into hpc.som.yale.edu, connecting to compute nodes, forwarding ports, setting up VS Code or Jupyter tunnels, using GitHub through the cluster, or troubleshooting SSH connections.

It helps you access the cluster without copying private keys onto it and helps keep connections working through network interruptions or multiple login steps.

connecting-securely — Skill for Claude Code by yale-som-hpc

Install

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.

Any agent

npx skills add yale-som-hpc/claude-code-marketplace --skill connecting-securely

Clone the repo

git clone --depth 1 https://github.com/yale-som-hpc/claude-code-marketplace

Made for: Claude Code.

Or install hpc, the plugin that ships this one along with the rest of its 23 skills, 3 commands.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/yale-som-hpc/claude-code-marketplace/connecting-securely/github.svg)](https://agentmods.dev/skills/yale-som-hpc/claude-code-marketplace/connecting-securely)

Your own site

<a href="https://agentmods.dev/skills/yale-som-hpc/claude-code-marketplace/connecting-securely"><img src="https://agentmods.dev/badge/skills/yale-som-hpc/claude-code-marketplace/connecting-securely/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/yale-som-hpc/claude-code-marketplace/connecting-securely"><img src="https://agentmods.dev/badge/skills/yale-som-hpc/claude-code-marketplace/connecting-securely.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 80 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,280 The whole file, excluding the scripts and references it only reads on demand.

Security scan D 2 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

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	$0.00080	$0.01280
Opus 5.5	$0.00032	$0.00512
Sonnet 5.5	$0.00016	$0.00256
Haiku 4.5	$0.00008	$0.00128

Measured 2mo ago against content hash a46766d564b0, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade D, and why

connecting-securely scanned grade D with 2 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 2mo 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.

Asks for rootmediumPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

chmod 700 ~/.ssh

Reaches for credential fileshighPrivilege escalation

SSH keys, cloud credentials, git-credentials, .npmrc, /etc/shadow: reading these is how a config file becomes a credential leak.

scp ~/.ssh/id_ed25519 hpc:~/.ssh/

plugins/hpc/skills/connecting-securely/SKILL.md · 141 lines

How it starts

The opening of the file, as written. The whole thing — 141 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Connecting Securely

Rule: use SSH keys and agent forwarding; never copy private keys onto the cluster.

Do not copy private keys

Bad:

scp ~/.ssh/id_ed25519 hpc:~/.ssh/

Good:

ssh-add -l
ssh hpc

If you need GitHub from the cluster, use gh auth login or carefully scoped SSH agent forwarding. Do not store your laptop private key on GPFS. If gh is not installed, see installing software.

Local SSH config

Example ~/.ssh/config on your laptop:

Host hpc
    HostName hpc.som.yale.edu
    User yournetid
    ServerAliveInterval 60
    ServerAliveCountMax 3
    ControlMaster auto
    ControlPath ~/.ssh/cm-%r@%h:%p
    ControlPersist 10m

Host b??? c???
    User yournetid
    ProxyJump hpc
    HostName %h.cm.cluster

ServerAliveInterval keeps NAT/firewalls from silently dropping an idle session; ControlMaster/ControlPersist reuse one warm connection across repeated logins. To keep long agent work alive across laptop sleep or wifi drops, see staying connected.

Enable ForwardAgent yes only if you need it for Git or another SSH hop. Agent forwarding is convenient, but any process you run on the remote host can ask your agent to sign while the connection is active.

Now login works:

ssh hpc

Only connect to a compute node after Slurm has allocated it to you. Use the hostname printed inside your allocation, then tunnel to that node.

Permissions

chmod 700 ~/.ssh
chmod 600 ~/.ssh/config
chmod 600 ~/.ssh/authorized_keys 2>/dev/null || true
chmod 700 ~

This is a shared system. Keep private files private: do not make your home directory, .ssh, .env, tokens, or project credentials group/world-readable.

SSH agent checks

ssh-add -l
ssh -T [email protected]

Inside tmux or a long-running shell, SSH_AUTH_SOCK can go stale. The value is only a path to the forwarded agent socket created by your current SSH login; it is not the key itself. If GitHub auth worked yesterday and fails today, do not copy keys to the cluster. Start a fresh SSH login, restart the shell, or look into refreshing SSH_AUTH_SOCK so it points at a current working socket owned by you.

Read the full file on GitHub · 141 lines

Changes

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.

2mo ago First seen · 141 lines · 80 tokens per session scan D a46766d564b0

Subscribe to this mod's changes

connecting-securely is a skill published in the GitHub repository yale-som-hpc/claude-code-marketplace (5 stars, last pushed 3mo ago), licensed Unlicense. It adds 80 tokens to every session and 1,280 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it D with 2 findings (asks for root, reaches for credential files). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

DevOps and cloud Security

connecting-securely next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
connecting-securelyyale-som-hpc/claude-code-marketplace	Skill	5	3mo ago	Unlicense	D	80	Claude Code
imagegenopenai/codex	Skill	133k	yesterday	Apache-2.0	A	113	Codex
playwright-climicrosoft/playwright	Skill	99k	yesterday	Apache-2.0	A	19	Claude Code
local-ai-agentsmicrosoft/ai-agents-for-beginners	Skill	79k	4d ago	MIT	A	200	Claude Code, Codex
systematic-debuggingobra/superpowers	Skill	313k	3d ago	MIT	A	21	Claude Code
next-cache-components-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	95	Claude Code
next-partial-prefetching-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	103	Claude Code

connecting-securely