Apollo GraphQL

Apollo Client 4.3 alpha and Router 2.16 shipped alongside GraphOS Studio improvements to Schema Proposals and Connect graduating from preview.

Custom scalars got first-class cache support. Apollo Client 4.3 alpha introduced a Scalar API for InMemoryCache: declare types via declaration merging, configure parse/serialize per field, and let the cache automatically serialize custom scalar variables before they reach the network. A companion Codegen plugin generates the inputObjects and scalarTypePolicies configuration without manual boilerplate.

Schema Proposals gained a rebuilt authoring experience. GraphOS Studio shipped a diff navigator for long proposals, inline conflict resolution with one-click accept actions, and a conflicts drawer for bulk navigation. Webhook payloads now carry richer context — proposal title, actor, Studio URL, affected subgraphs — plus two new event types: REVIEW_SUBMITTED and COMMENT_MENTION. Proposals can now also notify Slack channels alongside webhooks.

Sensitive headers masked across telemetry by default. The router now redacts authorization, cookie, and x-api-key by default in logs, OTel spans, and coprocessor communications. Two new telemetry selectors — response_errors_count and response_errors_field — expose GraphQL error counts and structured error detail as OTel attributes. Per-exporter trace sampling lets each backend receive an independent fraction of traces.

Connect graduated out of preview. The preview_connect_v0_4 config key is now a deprecated no-op; linking connect/v0.4 in a subgraph is the sufficient opt-in. A connect-migrate CLI assists migration from earlier spec versions.

Cache performance tightened in recent patches. Cache writes skip the full AST traversal when detecting @stream, limiting the check to fields that actually carry stream info. KeyArgsFunction and RelayFieldPolicy types were added to public entrypoints.