> ## Documentation Index
> Fetch the complete documentation index at: https://doc.gapstack.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Deploy a Lambda

> Upload an artifact to S3 before you create a Lambda. You cannot add a Lambda without an available artifact.

A common mistake is creating a **Lambda** before an artifact exists. Gapstack needs a zip already in the environment artifacts bucket. You cannot create a Lambda resource without that artifact.

<Warning>
  Configure the GitHub repository and upload the artifact first. Then select that artifact on the Lambda form and click **Create**.
</Warning>

<Steps>
  <Step title="Upload an artifact">
    Connect the GitHub repository and follow [Deploy an artifact to S3](/guides/deploy-artifacts). Use the environment OIDC role and artifacts bucket. Wait until the workflow finishes and the zip is in S3.
  </Step>

  <Step title="Create the Lambda">
    Open the environment, click **Add resources**, and choose **Lambda**. Select the artifact that was just uploaded, complete the form, then click **Create**.
  </Step>
</Steps>

<Note>
  If the Lambda form has no artifact to select, the upload has not completed. Fix the GitHub Actions workflow, deploy the artifact again, then return to the Lambda form.
</Note>