Harvest API v3

In Greenhouse, open API Credentials, click Create new API credentials, select Harvest V3 (OAuth), save, and configure the scopes your integration needs, as described in Harvest authentication. Greenhouse then gives you a Client ID and Client Secret. Use them to get a bearer token from https://auth.greenhouse.io/token with the OAuth client-credentials flow.

This is for signed Greenhouse partners. Start with the integration request form, then work with Greenhouse Partner Support as described in the Harvest partner OAuth guide. Provide your integration name, environment, required scopes, redirect URI(s), and logo; Greenhouse issues a Client ID and Client Secret for the authorization-code flow against https://auth.greenhouse.io/authorize and https://auth.greenhouse.io/token.

Create a Harvest API credential in Greenhouse from API Credentials / API Credential Management. The Harvest docs note existing Harvest API credentials can still be used during the v1/v2→v3 transition and for Audit Log token generation; see Harvest authentication and Audit Log authentication. Use the API key as the HTTP Basic username with an empty password (api_key:).