Azure SDK October 2026: Azure Core, managed identity and Cosmos DB for Rust 1.0.0
The October 2026 Azure SDK release highlights Azure Core 1.63.0 for .NET, Identity updates for Python and Java, and the first stable Cosmos DB for Rust 1.0.0. The authentication changes affect how DefaultAzureCredential behaves in production. Teams on the Cosmos DB Rust preview also get concrete upgrade steps.
Key points
- Azure Core 1.63.0 for .NET adds mTLS proof-of-possession for client certificate authentication and the managed identity federated identity flow.
- DefaultAzureCredential no longer stalls when IMDS is unavailable, and unavailable managed identity sources no longer abort the credential chain.
- If you use the experimental managed identity proof-of-possession option, change DisableMtlsProofOfPossession = true to EnableMtlsProofOfPossession = false to keep forcing bearer authentication.
- Cosmos DB for Rust 1.0.0 is stable; rename the preview_dtx, preview_patch and preview_opentelemetry flags to their unstable_ equivalents.
- Replace CosmosCredential::MasterKey with CosmosCredential::AccountKey; the User-Agent format has also changed.
- Identity 1.26.0 for Python adds user-assigned managed identity on Azure Arc servers and fixes a shared token cache issue.
Microsoft's October Azure SDK release brings updates across .NET, Python, Java and Rust, and the most consequential changes sit in authentication. Azure Core 1.63.0 for .NET adds mTLS proof-of-possession for client certificate authentication and for the managed identity federated identity flow. It also removes a delay in DefaultAzureCredential when the Instance Metadata Service is unreachable, and unavailable managed identity sources no longer end the credential chain early.
The Cosmos DB library for Rust reaches version 1.0.0, shipped together with the Client Driver and SDK Macros crates. Developers upgrading from the preview must rename the preview_dtx, preview_patch and preview_opentelemetry feature flags to their unstable_ counterparts and replace CosmosCredential::MasterKey with CosmosCredential::AccountKey. The post also covers Identity updates for Python and Java and a long list of new management and client packages.
Real-world use
- An ASP.NET Core API on Azure that uses managed identity and suffers startup delays when IMDS is unreachable.
- A .NET or Java service on Azure Arc servers that needs a user-assigned managed identity to reach Key Vault.
- A Rust service that talks to Cosmos DB and is moving from the preview crates to the stable 1.0.0 release.
Why it matters
Applications that rely on DefaultAzureCredential see different startup and credential chain behavior after this release. If you use Cosmos DB for Rust, feature flag and credential type names must be updated during the upgrade.
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