GitHub Expands Developer Platform with Actions Artifacts v5 and Copilot Extensions GA

GitHub has shipped a batch of platform updates in March that span the build, security, and AI layers of the developer experience. Actions Artifacts v5 introduces immutable storage with cryptographic attestation for build outputs, Copilot Extensions reaches general availability for third-party integrations, and GitHub Models expands with seven new provider partnerships.

Actions Artifacts v5

The fifth generation of GitHub Actions artifact storage brings immutable storage for build outputs — once an artifact is uploaded, it cannot be modified or replaced, only deleted. Combined with the new artifact attestation feature, which generates a signed provenance record for each artifact, teams can establish a tamper-proof chain of evidence from source code to build output.

Artifact attestation uses Sigstore-compatible signatures, meaning the provenance records can be verified using standard supply chain security tools. For organizations subject to compliance requirements — SOC 2, FedRAMP, or supply chain security mandates — this provides a built-in mechanism for demonstrating build integrity without third-party notarization services.

Copilot Extensions GA

Copilot Extensions, which allow third-party tools to integrate directly into the Copilot chat experience, has reached general availability. Extensions can respond to @-mentions in Copilot chat, providing domain-specific knowledge and actions that go beyond what Copilot's base model can offer. Launch partners include Datadog (monitoring queries), Sentry (error analysis), LaunchDarkly (feature flag management), and Hashicorp (Terraform assistance).

The extension API provides a standardized interface for receiving chat messages, accessing repository context, and returning formatted responses. Extensions run on the developer's own infrastructure, meaning sensitive data stays within the organization's security perimeter rather than being processed by GitHub.

GitHub Models Expansion

GitHub Models — the playground for experimenting with AI models directly in GitHub — has added providers including Cohere, Mistral, AI21 Labs, and DeepSeek, bringing the total number of available models to over 50. The expansion positions GitHub as a neutral platform for model evaluation, allowing developers to compare responses from different providers without creating separate API accounts.

All three features are available to GitHub Teams and Enterprise plans, with Copilot Extensions and GitHub Models also available on individual Copilot subscriptions.