Documented steps

Create .devcontainer/devcontainer.json at the repo root, e.g. {"name": "My project", "image": "mcr.microsoft.com/devcontainers/javascript-node:20"} (a root .devcontainer.json also works)
With NO dev container config, Codespaces uses the default universal Linux image, which bundles common runtimes (Python, Node.js, Java, Go, C++, Ruby, .NET, PHP...)
For per-team/per-stack setups, add alternative configs exactly one level below .devcontainer: .devcontainer/frontend/devcontainer.json, .devcontainer/backend/devcontainer.json
Commit and push; when creating a codespace from the web UI ('...' > 'New with options') users pick a configuration from the dropdown; from the CLI use gh codespace create --devcontainer-path .devcontainer/frontend/devcontainer.json
Test the config by creating a codespace (or locally with the devcontainer CLI) and checking the creation log for lifecycle-command failures
Docs: https://docs.github.com/en/codespaces/setting-up-your-project-for-codespaces/adding-a-dev-container-configuration/introduction-to-dev-containers

Known gotchas

Alternative configs must sit exactly one directory level below .devcontainer — deeper nesting (.devcontainer/a/b/devcontainer.json) is not picked up
If both .devcontainer/devcontainer.json and a root .devcontainer.json exist, the one inside .devcontainer/ takes precedence
Configurations don't inherit from each other — each codespace uses exactly one devcontainer.json; shared setup must be duplicated or pulled in via a shared image/Features
The default image is large and generic; teams with specific dependencies should define a config rather than rely on it

docs.github.com · 5 steps · unrated

Understand and configure GitHub merge queue for CI gating

docs.github.com · 5 steps · unrated

Attest and verify a container image with GitHub Artifact Attestations

docs.github.com · 6 steps · unrated

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Configure a repository for GitHub Codespaces: devcontainer.json locations, the default image, and multiple configurations

Documented steps

Known gotchas

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