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Troubleshooting prebuilds

You can use prebuilds to speed up the creation of codespaces. This article provides troubleshooting steps for common issues with prebuilds.

Codespaces is available for organizations using GitHub Team or GitHub Enterprise Cloud. For more information, see "GitHub's products."

For more information about Codespaces prebuilds, see "Prebuilding your codespaces."

Checking whether a codespace was created from a prebuild?

When you create a codespace, you can choose the type of the virtual machine you want to use. If a prebuild is available for the type of virtual machine, " Prebuild ready" is shown next to it.

A list of available machine types

If you have your Codespaces editor preference set to "Visual Studio Code for Web" then the "Setting up your codespace" page will show the message "Prebuilt codespace found" if a prebuild is being used.

The 'prebuilt codespace found' message

Similarly, if your editor preference is "VS Code" then the integrated terminal will contain the message "You are on a prebuilt codespace defined by the prebuild configuration for your repository" when you create a new codespace. For more information, see "Setting your default editor for Codespaces."

After you have created a codespace you can check whether it was created from a prebuild by running the following GitHub CLI command in the terminal:

Shell
gh api /user/codespaces/$CODESPACE_NAME --jq .prebuild

This returns true if the codespace was created using a prebuild.

Alternatively, if GitHub CLI (gh) is not installed, you can use the following command, which returns createFromPrebuild if the codespace was created from a prebuild:

Shell
cat /workspaces/.codespaces/shared/environment-variables.json | jq '.ACTION_NAME'

The "Prebuild Ready" label is sometimes missing

You may notice that sometimes, when you create a new codespace from a prebuild-enabled branch, the " Prebuild Ready" label is not displayed in the dialog box for choosing a machine type. This means that prebuilds are not currently available.

By default, each time you push to a prebuild-enabled branch, the prebuild template is updated. If the push involves a change to the dev container configuration then, while the update is in progress, the " Prebuild Ready" label is removed from the list of machine types. During this time you can still create codespaces without a prebuild template. If required, you can reduce the occasions on which prebuilds are unavailable for a repository by setting the prebuild template to be updated only when you make a change to your dev container configuration files, or only on a custom schedule. For more information, see "Configuring prebuilds."

If your branch is not specifically enabled for prebuilds it may still benefit from prebuilds if it was branched from a prebuild-enabled branch. However, if the dev container configuration is changed on your branch, so that it's not the same as the configuration on the base branch, prebuilds will no longer be available on your branch.

Here are things to check if the " Prebuild Ready" label is not displayed for a particular branch:

  • Confirm that a prebuild configuration exists for this branch. If you’re not a repository administrator, you'll need to reach out to one to confirm this.
  • Confirm that the prebuild configuration includes your region.
  • Check whether a change to the dev container configuration was pushed to the prebuild-enabled branch recently. If so, you will typically have to wait until the prebuild workflow run for this push completes before prebuilds are available again.
  • If no configuration changes were recently made, go to the Actions tab of your repository, click Codespaces Prebuilds in the workflows list, and check that prebuild workflow runs for the branch are succeeding. If latest runs of a workflow failed, and one or more of these failed runs contained changes to the dev container configuration, then there will be no available prebuilds for the associated branch.

Troubleshooting failed workflow runs for prebuilds

If the workflow runs for a prebuild configuration are failing, you can temporarily disable the prebuild configuration while you investigate. For more information, see "Managing prebuilds."

Further reading