Google Cloud announced streaming support for API Gateway in public preview on October 22. The update lets developers route incremental model responses and persistent connections through the managed gateway instead of sending that traffic around it.

Supported transports include Server-Sent Events, chunked HTTP responses, WebSockets and bidirectional gRPC streaming. Google says existing API-key enforcement, JWT validation, backend service-account authentication, logging and monitoring continue to work with streaming traffic.

A new gateway, not an in-place switch

Developers can enable the feature when creating a gateway with the --enable-streaming flag. The streaming mode is immutable: an existing non-streaming gateway cannot simply be upgraded in place. New streaming gateways also use a predictable hostname derived from the gateway ID, project number and region.

Although the announcement emphasizes keeping the same API contract, the documentation makes clear that backend protocol and timeout settings still matter. WebSockets require HTTP/1.1, while gRPC requires HTTP/2.

SSE and chunked responses retain a default 15-second deadline unless developers change it. The maximum is 3,600 seconds; WebSocket connections also end after one hour. Clients therefore need appropriate timeout configuration and reconnection handling, rather than assuming streams remain open indefinitely.

Preview limits matter for deployment

Terraform enablement and custom domains through Serverless NEGs and an external Application Load Balancer are not supported during the preview. The documentation also says enabling gateway streaming does not make its MCP endpoints stream: those responses remain a single JSON body.

For AI application teams, the practical benefit is centralized authentication and visibility for token-by-token output. The immediate work is provisioning a new gateway, validating backend settings and checking whether preview restrictions fit the deployment.