github-codespaces-efficiency

A guide to making GitHub Codespaces, cloud-based development environments for repositories, start faster and use less money.

In plain words
What is it for?
Use it to review a repository's devcontainer, tune startup and prebuild settings, choose machine sizes, and set better idle-time practices.
Why use it?
It helps identify oversized development containers, unsuitable machines, overly broad prebuilds, and excessive idle time.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/drvoss/everything-copilot-cli/github-codespaces-efficiency
Any agent
npx skills add drvoss/everything-copilot-cli --skill github-codespaces-efficiency
Clone the repo
git clone --depth 1 https://github.com/drvoss/everything-copilot-cli

Made for: Claude Code, Codex.

Per session 37 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,119 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00037 $0.01119
Opus 5 $0.00018 $0.00560
Sonnet 5 $0.00007 $0.00224
Haiku 4.5 $0.00004 $0.00112

Measured 2d ago against content hash 4ad674f85de5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

github-codespaces-efficiency 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 2d 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.

skills/copilot-exclusive/github-codespaces-efficiency/SKILL.md · 122 lines

How it starts

The opening of the file, as written. The whole thing — 122 lines — stays where its author put it; the contents beside it link to each section on GitHub.

GitHub Codespaces Efficiency

Audit GitHub Codespaces efficiency with a GitHub-native lens. Focus on devcontainer size, startup time, machine sizing, prebuild scope, and idle-time discipline without stripping away tools the team relies on every day.

Why This is Copilot-Exclusive

GitHub Codespaces is a GitHub-native development environment. This skill is most useful when you can inspect repository configuration, correlate it with gh-based Codespaces metadata, and turn the result into Copilot-driven GitHub workflow guidance.

When to Use

  • Codespaces start too slowly or cost more than the team expects
  • .devcontainer/ exists and needs trimming, right-sizing, or prebuild tuning
  • A team wants guidance on machine sizing, idle timeout, or prebuild scope
  • The repository is onboarding Codespaces for the first time and needs a minimal baseline

When NOT to Use

Instead of github-codespaces-efficiency Use
Debugging a failing GitHub Actions run actions-debugging
Reviewing PR lifecycle and checks github-pr-workflow
General local development environment setup without Codespaces ordinary repo setup guidance

Prerequisites

  • Access to .devcontainer/ when it exists
  • gh CLI access if you want live Codespaces or machine data
  • Understanding of the team's baseline tooling requirements

Load Only What You Need

If no .devcontainer/ exists yet, start with codespaces.md and define a minimal baseline before optimizing.

Core Workflow

1. Measure first

Get-ChildItem .devcontainer -Recurse -File | Select-Object -ExpandProperty FullName
gh codespace list
$repo = gh repo view --json nameWithOwner --jq ".nameWithOwner"
gh api "/repos/$repo/codespaces/machines"

Read the full file on GitHub · 122 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.

  1. 2d ago First seen · 122 lines · 37 tokens per session scan A 4ad674f85de5

Subscribe to this mod's changes

github-codespaces-efficiency is a skill published in the GitHub repository drvoss/everything-copilot-cli (45 stars, last pushed 5d ago), licensed MIT. It adds 37 tokens to every session and 1,119 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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