GitHub should resume REST API versioning to prevent breaking changes for integrators

[joshpollara]

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A recent incident in the GitHub Actions API exposed a systemic problem with REST API contract stability:

https://github.com/orgs/community/discussions/9752

In that case, production behavior for an existing endpoint changed in a way that diverged from the published OpenAPI schema and documented HTTP semantics, resulting in breakage across downstream tooling. The issue was not discoverable via version negotiation, preview headers, or opt-in mechanisms, because no new API version was introduced.

GitHub's REST API is versioned specifically to prevent this class of failure. In practice, however, contract-affecting behavior has been introduced on existing API versions, relying on rollout timing or changelogs rather than explicit versioning. That approach does not work for integrators who depend on machine-verifiable contracts.

Many tools rely on the OpenAPI schema and HTTP status codes as the source of truth. When those drift from production behavior, SDKs, generated clients, CI systems, and automation tooling fail in ways that are difficult to diagnose and recover from.

This incident demonstrates why REST API versioning needs to be actively used again for contract-affecting changes:

• HTTP status codes and response semantics are part of the API contract
• OpenAPI schema accuracy is critical for SDKs and generated clients
• Incremental or dark rollouts amplify confusion when behavior is not versioned
• CI, automation, and orchestration tooling depends on predictable, machine-verifiable contracts

Rolling back the change addressed the immediate breakage. The longer-term fix is to reestablish API versioning as the primary mechanism for introducing breaking or contract-affecting behavior, even if version bumps are infrequent.

Clear guidance on when versioning is required, and ensuring schemas and documentation are updated in lockstep with production behavior, would materially reduce integration risk for the ecosystem.

[github-actions[bot]]

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