docs: add v6.0.0 changelog entry

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: gavinsharp

changelog.md

@@ -1,3 +1,31 @@
+## 6.0.0 - 2026-02-09
+* feat: SDK generator upgrade with auth providers, logging, and restructured upload API
+* Major SDK regeneration with upgraded Fern TypeScript SDK generator (v3.46.3). Introduces pluggable auth,
+* structured logging with sensitive data redaction, and centralizes error handling across all clients.
+* Breaking changes:
+* PhenoMLClient (WrapperClient) no longer exported from main entry point; use phenomlClient directly
+* All resource client classes renamed with Client suffix (e.g. Agent -> AgentClient, Construe -> ConstrueClient)
+* UploadRequest restructured from discriminated union (UploadRequest.Csv/Json) to flat interface with Format enum
+* Remove UploadRequestCsv and UploadRequestJson types
+* Remove user_id field from ChatMessageTemplate, ChatSessionTemplate, FhirProviderTemplate, SummaryTemplate, McpServerResponse, McpServerToolResponse, WorkflowDefinition, WorkflowResponse
+* Construe getASpecificCode parameter renamed from codeId to codeID
+* Auth client options simplified to use standard BaseClientOptions
+* New features:
+* Configurable logging system (LogConfig, Logger, ConsoleLogger) with sensitive data redaction for headers, URLs, and query params
+* Custom fetch implementation support via BaseClientOptions.fetch
+* AuthProvider pattern for pluggable authentication (BearerAuthProvider, NoOpAuthProvider)
+* BodyIsNullError type for null response bodies on streaming/SSE endpoints
+* Form-encoded request body support (requestType: "form")
+* New exports: BaseClientOptions, BaseRequestOptions types
+* Infrastructure improvements:
+* Centralized error handling via handleNonStatusCodeError() replacing duplicated switch blocks
+* Improved error class prototype chains (proper instanceof and stack traces via new.target.prototype)
+* Case-insensitive header merging
+* React Native runtime detection now prioritized over Node.js
+* Cross-platform timer types (ReturnType<typeof setTimeout> instead of NodeJS.Timeout)
+* Automatic Accept header based on response type
+* Removed X-Fern-SDK-Name, X-Fern-SDK-Version, User-Agent from default headers
+
 ## 5.3.0 - 2026-02-09
 * feat: add custom code system export endpoint
 * Add new exportCustomCodeSystem method to the construe client that allows exporting custom (non-builtin) code systems as JSON files. This feature enables users to backup and transfer code systems between instances.