Changelog

Jul 9, 2026

3.79.2

(fix): Pin the npm toolchain used by the generated publish workflow. The .github/workflows/ci.yml publish job now runs on a pinned Node LTS (node-version: "lts/Krypton") and calls npm publish directly instead of npx -y npm@latest publish. Relying on npm@latest pulled whatever npm release was newest at publish time, so a broken npm release could break publishing. The pinned Node LTS bundles an npm that supports OIDC trusted publishing. The npx semver invocation used for backport detection is also pinned to semver@7.8.1.

Jul 8, 2026

3.79.1

(fix): Generated snippets now use baseUrl instead of environment when no environments are defined in the API spec, matching the actual constructor parameter users should provide.

Jul 7, 2026

3.79.0

(feat): Add a defaultTimeout custom config option, expressed in milliseconds, which is idiomatic for JavaScript/TypeScript (setTimeout, AbortSignal.timeout(ms)). Use "infinity" to disable the timeout. The seconds-based defaultTimeoutInSeconds and timeoutInSeconds keys are now deprecated but continue to work: their values are converted to milliseconds (× 1000). Precedence is defaultTimeout > defaultTimeoutInSeconds > timeoutInSeconds. Generated SDK output is unchanged for existing configs.

3.78.2

(fix): Fix a regression where | undefined was dropped from the value type of generated Record types backed by optional map values (e.g. optional additionalProperties). Optional map values now correctly generate Record<string, T | undefined> with serialization record(string(), T.optional()), while unknown/any map values keep the redundant | undefined stripped (Record<string, unknown>).

3.78.1

(fix): Fix TypeError: Cannot use 'in' operator to search for 'path' in undefined crash when null or undefined is passed to a file upload parameter at runtime. The error is now a clear TypeError describing the expected types instead of a cryptic in operator failure.

3.78.0

(feat): Add an additionalBodyParameters request option that spreads additional parameters into an endpoint’s JSON request body. Caller-supplied properties override matching keys in the endpoint body, matching the behavior of the Python, Swift, and Ruby SDKs. Omitting the option leaves the request body unchanged and never fabricates a body for bodyless requests.

3.77.3

(fix): Revert the automatic renaming of inlined path parameters that collide with request body properties (introduced in 3.77.1). These collisions are now rejected at the CLI level: fern check errors and asks the user to deconflict the names (e.g. via x-fern-parameter-name).

Jul 6, 2026

3.77.2

(fix): Fix ESM spec violations for extensionless imports in generated SDKs. The rename-to-esm-files.js script now resolves bare directory imports (e.g. from "./oauth" → from "./oauth/index.mjs") and extensionless file imports (e.g. from "./client" → from "./client.mjs"), which previously broke Node’s ESM loader and Turbopack (Next 16). Also sets moduleResolution: "bundler" in tsconfig.esm.json for correct ESM semantics.

3.77.1

(fix): When an inlined path parameter (inlinePathParameters: true) shares its property name with an inlined request-body property (e.g. a {idType} path parameter and an idType body field), the request wrapper now keeps both fields by renaming the path parameter with a PathParam suffix (e.g. idTypePathParam). Previously the two values were collapsed into a single shared field, which made it impossible to send different values for the URL path and the request body.

Jul 4, 2026

3.77.0

(feat): Implement SSE stream auto-reconnection for resumable endpoints. When an SSE stream drops mid-connection and the endpoint is marked resumable: true, the SDK now automatically reconnects using the Last-Event-ID header, honoring server-sent retry directives clamped to 30 seconds. Reconnection respects reconnectionEnabled and maxReconnectionAttempts options.

Jul 3, 2026

3.76.0

(feat): Add React Query hooks generation support via the generateReactQueryHooks config flag. When enabled, generates a react-query/ directory with a tRPC-style namespace object that mirrors the SDK client hierarchy (e.g. seedApi.user.list.useQuery()). Each query endpoint exposes useQuery, useSuspenseQuery, getQueryKey, getQueryOptions (for SSR/RSC), and invalidate. Mutation endpoints expose useMutation. Hierarchical cache invalidation at endpoint, service, and SDK levels. Per-service file splits with wildcard subexports for tree-shaking. All exports available via a ./react-query package.json subexport with optional peer dependencies on react and @tanstack/react-query.

Jul 2, 2026

3.75.3

(fix): Emit object keys without quotes in generated dynamic snippets when the key is a valid JavaScript identifier. Previously, keys of maps and free-form objects (e.g. map<string, unknown> values) were always quoted, producing inconsistent output where metadata: { "releaseDate": ... } sat next to unquoted typed properties. Keys that are not valid identifiers remain quoted.

Jul 1, 2026

3.75.2

(fix): Fix formatter regression caused by pnpm 11 Docker upgrade. The Dockerfile’s rm -rf /.pnpm/store cleanup step was breaking all globally installed tools (biome, oxfmt, prettier) because pnpm 11 stores global packages as symlinks into $PNPM_HOME/store. Also clean up a redundant code template wrapper in constructor generation that produced malformed indentation before formatting.

3.75.1

(fix): Fix asymmetric webhook signature verification to support payload-format configuration. When payload-format.components includes timestamp, the timestamp header value is now included in the data verified by the asymmetric signature, closing a replay-protection gap where the timestamp was unauthenticated.

(fix): Use IterableIterator<T> instead of HeadersIterator<T> in the generated Headers.ts shim. HeadersIterator was added in TypeScript 5.6; the previous annotations broke compilation on TS < 5.6.

Jun 30, 2026

3.75.0

(feat): TimeoutError now extends the base API error class instead of Error directly, so instanceof ApiError catches timeout errors. Added a requestId getter to the base API error class that extracts x-request-id from the raw response headers.

Jun 29, 2026

3.74.2

(chore): Remove the tsgolint rebuild-from-source Docker stage. The published oxlint-tsgolint 0.23.0 binaries are now used directly, eliminating the golang image pull, typescript-go submodule clone, and Go compilation that made Dockerfile builds slow. The two Go stdlib CVEs previously addressed by the rebuild (CVE-2026-42507 net/textproto, CVE-2026-27145 crypto/x509) are not exercisable by a linting binary; they will clear automatically when tsgolint ships a release built with go1.26.4+.

3.74.1

(fix): Fix TS5076 compilation error in generated pagination code when both hasNextPage and step are configured on offset pagination. The ?? and && operators were mixed without parentheses.

(fix): Fix TS1484 compilation error in generated webhook code by using import type for SignatureEncoding to satisfy verbatimModuleSyntax.

Jun 26, 2026

3.74.0

(feat): Support resumable flag in SSE streaming endpoints. When an endpoint has x-fern-streaming.resumable: true, the generated SDK now includes resumable: true in the stream event shape, plumbing the flag through to the runtime for use by reconnection logic. Adds stream: { reconnectionEnabled, maxReconnectionAttempts } request options for runtime control of reconnection behavior.

3.73.4

(fix): Treat null values identically to undefined when serializing query string parameters. Previously, null values in objects and arrays were serialized as empty strings (e.g. key=); they are now omitted from the query string, matching the existing behavior for undefined values and the QueryStringBuilder API.

3.73.3

(fix): Fix SSE event parsing to buffer data and yield on blank lines per the SSE spec. Previously, the parser yielded events immediately on data: lines, causing id: and retry: fields that follow the data: line to be missed or associated with the wrong event.