github codespaces efficiency

Author's original introduction

Audit and improve GitHub Codespaces efficiency. Use this skill when a user wants faster Codespaces startup, lower Codespaces spend, slim devcontainers, right-size machines, tune idle timeout, or scope prebuilds to branches with sustained usage.

SkillPi interpretation

Tasks

github codespaces efficiency

Audience

Use the scenarios stated in the author's introduction.

Inputs and outputs

See the complete author document; outputs have not been runtime verified by SkillPi.

Software, accounts and paid services

Check required software, accounts, costs and permissions in the full document; confirm and authorize actual file access and external services in your host. Domains referenced in the documents (not a runtime allowlist): No HTTP(S) domain stated.

Limits and differences

Functionality, version status and outcome statements in the introduction are author claims. Only pinned source and static attachment evidence were checked; runtime behavior, external services and compatibility are not guaranteed.

Testing

Not tested

Security rating and access scope

caution · Static evidence review; not a runtime safety guarantee.

Check required software, accounts, costs and permissions in the full document; confirm and authorize actual file access and external services in your host. Domains referenced in the documents (not a runtime allowlist): No HTTP(S) domain stated.

Before use, confirm and authorize actual file access, external services and network destinations in your host. This review grants no runtime permissions.

Original SKILL.md

---
name: github-codespaces-efficiency
description: 'Audit and improve GitHub Codespaces efficiency. Use this skill when a user wants faster Codespaces startup, lower Codespaces spend, slim devcontainers, right-size machines, tune idle timeout, or scope prebuilds to branches with sustained usage.'
---

# GitHub Codespaces Efficiency

Use this skill as a lean entrypoint for GitHub Codespaces efficiency work. Inspect the repo, identify waste, and load only needed references.

If no `.devcontainer/` exists yet, load [`references/codespaces.md`](./references/codespaces.md) and define a baseline before proceeding with the steps below.

## Use This Skill When

- The user wants faster Codespaces startup or lower Codespaces spend.
- The repo has a `.devcontainer/` or explicit Codespaces configuration questions.
- The user asks for devcontainer optimization, machine sizing, prebuild strategy, or idle-timeout guidance.
- The user is setting up Codespaces for the first time or needs help creating a new `.devcontainer/` from scratch.

## Load Only What You Need

- [`references/codespaces.md`](./references/codespaces.md) — devcontainer, machine-sizing, prebuild, idle-timeout guidance, and reporting.
- [`references/review-rubric.md`](./references/review-rubric.md) — load only for review passes.

## Core Workflow

### 1. Measure first

```bash
find .devcontainer -maxdepth 2 -type f
gh codespace list
repo=$(gh repo view --json nameWithOwner --jq .nameWithOwner)
gh api "/repos/$repo/codespaces/machines"
```

If `gh` auth fails or the user lacks repo admin scope, proceed with static analysis of `.devcontainer/` files; mark machine-type and prebuild recommendations as unverified.

Look for: devcontainer image >2 GB or more than 10 features, machine type larger than usage data supports, missing `devcontainer-lock.json` (recommend adding — many repos predate lock-file support), prebuilds scoped too broadly, and idle timeout mismatched to usage patterns.

### 2. Apply guardrails

Check each proposed fix against these rules before recommending it:

1. Does not remove tools the team uses every day — drop any fix that strips required development tools or extensions.
2. Does not assume smaller is always better — balance machine cost against developer experience and throughput.
3. Does not turn the devcontainer into a production image — drop any fix that adds production-only dependencies unless the team explicitly requires it.
4. Incremental changes preferred — a greenfield baseline is appropriate only when no `.devcontainer/` exists; flag (do not drop) changes that restructure an existing config.
5. Repo changes stay separate from org settings — split any fix that mixes repo-editable files with org-level or user-level Codespaces settings into two distinct recommendations.

### 3. Select the top 3 fixes

From the six candidates below, keep only those supported by audit evidence from step 1 *and* passing all guardrails from step 2. Rank survivors by estimated monthly cost savings (USD). Select all candidates that meet both criteria, up to a maximum of 3.

1. Trim devcontainer — remove features, packages, or extensions not needed for everyday development work; target image <2 GB and fewer than 10 features
2. Right-size machine type — match to observed usage patterns; if data is unavailable, state assumptions explicitly
3. Scope prebuilds — enable for the default branch, `release/*` branches active in the last 14 days, and branches with more than 5 Codespaces per week; disable for all others
4. Tune idle timeout — 30 min default; 15 min if most sessions end before 30 min; 60 min if most sessions run longer
5. Remove unused extensions or port-forwarding rules
6. Reduce devcontainer image size and improve layer caching

### 4. Verify

- Start a test Codespace to confirm devcontainer changes build and start as expected.
- Validate machine sizing against observed usage when telemetry is available; otherwise mark as unverified.
- Treat unexpected build or startup failures as real bugs even when the configuration looks correct.

## Required Output

**Waste sources:** [top cost or startup-time drivers]

**Proposed fixes:** [top 3 changes supported by audit evidence and passing guardrails]

**Validation:** [proven live / static-only / remaining risk]

**Impact:**
- Startup time: [expected] / [measured if available]
- Monthly spend: [expected] / [measured if available]
- Resource utilization: [expected] / [measured if available]

## References

- [`references/codespaces.md`](./references/codespaces.md)
- [`references/review-rubric.md`](./references/review-rubric.md) — load when reviewing completed efficiency work

Copyright and license notice

MIT License

Copyright GitHub, Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.