3.53.5
(fix): Fix wire test generation for SSE streaming endpoints with error responses.
Error-case tests for SSE endpoints would generate for await iteration over the response,
but the client throws typed errors for non-2xx status codes. Error-response tests now use
rejects.toThrow() and mock the response with jsonBody instead of sseBody.
3.53.4
(fix): Fix union member interfaces shadowing built-in TypeScript types like Date and Error.
Union variants such as date generated export interface Date inside the union namespace,
which shadowed the global Date type and caused compile errors when other variants
referenced it. Interface names now use safeName (e.g., Date_, Error_) to avoid
collisions with reserved identifiers.
3.53.3
(fix): Add ignoredFields support to formUrlEncodedBody in wire test mock server.
Paginated POST endpoints using application/x-www-form-urlencoded content type
(e.g. Twilio) now correctly ignore pagination cursor fields when matching request
bodies in wire tests, matching the existing behavior for JSON body endpoints.
3.53.2
(fix): Fix map types with enum keys to generate Partial<Record<EnumType, ValueType>> instead of
Record<EnumType, ValueType | undefined>. The previous type required all enum keys to be
explicitly provided (even as undefined), while the new type correctly allows keys to be
omitted entirely, matching the semantics of a sparse map.
3.53.1
(fix): Fix duplicate close event in WebSocket _handleAbort when close() was already called.
The abort handler now checks _closeCalled before dispatching a close event, preventing
applications from receiving duplicate close notifications.
3.53.0
(feat): Add connectionTimeoutInSeconds and abortSignal options to WebSocket ConnectArgs.
The connectionTimeoutInSeconds option sets the timeout for establishing the WebSocket
connection (converted to milliseconds internally). The abortSignal option allows callers
to abort the WebSocket connection attempt using an AbortController.
3.52.9
(fix): Deduplicate @example JSDoc blocks in request wrapper and type declaration
comments. When multiple examples produce identical output, only the first is
kept. The endpoint method docs already had this deduplication; this fix extends
it to request wrappers and type declarations.
3.52.8
(fix): Update generated CI workflow to publish older patch versions with --tag backport
instead of the default latest tag. When publishing a version older than the current
latest on npm (e.g. v1.3.2 after v1.4.0), the publish step now compares against
npm’s current latest using semver and uses --tag backport to avoid moving the
latest pointer backwards.
3.52.7
(fix): Disable commit signing and skip hooks for the throwaway git commit in
deleteGitIgnoredFiles to avoid triggering prompts (e.g. Touch ID on
macOS, 1Password SSH agent) during local generation.
3.52.6
(fix): Fix TypeScript generator crash when discriminated union discriminant values start
with digits (e.g., “1foo”, “1bar”). The generated code now prefixes such identifiers
with an underscore to produce valid TypeScript.
3.52.5
(fix): Fix Edge Runtime compatibility warning in Next.js. The runtime detection code
previously used process.versions.node directly, which caused Next.js bundlers
(Turbopack/webpack) to emit “A Node.js API is used which is not supported in
the Edge Runtime” warnings during static analysis, even though the code path was
guarded by an Edge Runtime check. The fix assigns process to a local variable
first, preventing bundlers from flagging the indirect property access.
3.52.4
(fix): Fix publint warning for ambiguous types in package.json exports. Remove the top-level
types condition from export entries in package.json so that import and require
conditions each resolve to their own correctly-typed declaration file (.d.mts for ESM,
.d.ts for CJS). This eliminates the publint warning about CJS types being used when
resolving with the “import” condition.
3.52.3
(fix): Handle nullable header types by converting null to undefined. HTTP headers
don’t have a “null” concept — they’re either present with a value or absent.
When a header’s type is nullable (explicitly via nullable: true in the spec),
the generated code now wraps the value with ?? undefined to ensure null values
are treated as “don’t send the header” instead of causing type errors.
3.52.2
(fix): Fix biome formatting not being applied in github output mode. The generator was calling
checkFix() (biome) without first installing biome, causing formatting to silently fail.
Now installs checkFix dependencies when tools are not globally available, matching the
existing behavior in downloadFiles mode.
3.52.1
(feat): Add JSDoc availability annotations for SDK endpoint methods. Endpoints marked as
deprecated in the Fern definition now generate a @deprecated JSDoc tag, causing
IDEs to show strikethrough and deprecation warnings. Endpoints marked as in-development
or pre-release generate a @beta JSDoc annotation. This applies to all endpoint types
(default, file download, and streaming).
3.52.0
(feat): Enable generateSubpackageExports by default. Generated TypeScript SDKs now include
subpackage export entries in package.json, allowing users to import subpackage clients
directly (e.g., import { FooClient } from '@acme/sdk/foo'). This enables JavaScript
bundlers to tree-shake unused subpackages, resulting in smaller bundle sizes.
To opt out, explicitly set generateSubpackageExports: false in your generator config.
(feat): Add tree-shaking smoke test to verify that importing a single subpackage produces a
significantly smaller webpack bundle than importing the full SDK.
3.51.6
(chore): In downloadFiles mode, install only the configured formatter/linter
packages instead of the full dependency tree when outputting source files
only. This replaces the ~1.8s full pnpm install with a targeted
pnpm add of just the check:fix packages (e.g. @biomejs/biome,
prettier, oxfmt, oxlint).
3.51.5
(fix): Fix duplicate identifier collision in serialization schemas when two different packages
define types with the same name. The schema generator now tracks directly imported type
names and switches to namespace imports when a collision would occur, preventing
“Duplicate identifier” TypeScript errors in cross-package type references.
3.51.4
(fix): Add cache: "no-store" to streaming and SSE fetch requests to prevent
Next.js from buffering streamed responses. The option is guarded by a
cached runtime feature-detection so it is safely skipped in runtimes
that do not support the cache RequestInit option (e.g. Cloudflare Workers).
3.51.3
(fix): Fix duplicate case clauses in error handling switch statements when multiple errors
map to the same status code. The generator now deduplicates errors by status code,
keeping the first error for each status code.
(fix): Fix test generator to skip error examples whose status code is already handled by
a prior error, matching the code generator’s deduplication behavior.
(fix): Fix test generator to include the error discriminant property (e.g., errorName) in
mock response bodies for property-discriminated errors, so the generated switch
statement can match the correct error case.
(fix): Fix inferred auth provider to handle endpoints without wrapped request types,
preventing crashes during generation for non-wrapped endpoints.
3.51.2
(chore): Use generator-cli JS API directly instead of subprocess spawning.
Remove generator-cli from Docker image since it is now bundled via esbuild.
3.51.1
(chore): Upgrade Docker base image from Node.js 22 to Node.js 24 LTS.
3.50.1
(fix): Support custom WebSocket connection method names via the connectMethodName IR field
(sourced from x-fern-sdk-method-name on AsyncAPI channels). When specified, the
generated client uses the custom name instead of the default connect.
3.51.0
(feat): Add event-level SSE discrimination support. When an SSE streaming endpoint returns a
discriminated union with discriminatorContext: "protocol", the Stream class injects the
SSE event: field value into the JSON data as the discriminator key before deserialization.
This matches the Go SDK’s approach and supports proper SSE event-level discrimination,
multiline data: concatenation, and blank-line event boundaries per the SSE spec.
Also adds wire test generation support for SSE streaming endpoints.
3.50.0
(feat): Add webhook signature verification helpers to generated SDKs. Define signature
verification via the x-fern-webhook-signature OpenAPI extension on individual webhooks
or as a document-level default, and the generator produces a WebhooksHelper class for
the most common config plus named helpers (e.g. PaymentNotificationWebhooksHelper) for
each unique per-webhook override. Supports HMAC (SHA-1/256/384/512) and asymmetric
(RSA-SHA256, ECDSA-SHA256) verification with configurable encoding, signature prefixes,
payload format composition, timestamp-based replay protection, and JWKS key resolution.
Includes unit tests for the underlying crypto primitives.
3.49.3
(chore): Update oxfmt to 0.35.0, oxlint to 1.50.0, and oxlint-tsgolint to 0.14.2.
3.49.2
(fix): Replace lodash-es template with Eta for template file processing. The lodash
templating engine crashes on backticks (template literals) because it uses
new Function() internally. Eta is a modern, lightweight, zero-dependency
templating engine that properly handles backticks and uses the same <% %>
syntax, requiring no changes to existing template files.
3.49.1
(fix): Change [TIMING] log statements from info to debug level so they are only
printed when debug logging is enabled.
3.49.0
(feat): Optimize schema serialization layer performance with 7.2x geometric mean speedup.
Replace O(n²) array/object spread patterns in list and record builders with O(n) loops,
lazily memoize property metadata in object schemas, simplify prototype chain check,
use for-in loops to avoid Object.entries() allocations, cache required-key Sets,
and eliminate rest spread in union discriminant extraction.
3.48.5
(chore): Add timing logs for each phase of SDK generation: code generation, package manager install,
lockfile generation, formatting/linting, build, and publish. Each phase logs its duration
in milliseconds with a [TIMING] prefix for easy identification.
3.48.4
(fix): Switch Docker base image from node:22.12-alpine3.20 to node:22.12-slim (Debian).
Alpine uses musl instead of glibc, causing a ~14x performance regression for Biome
due to musl’s allocator being significantly slower for allocation-heavy workloads like AST parsing.
3.48.3
(chore): Update @biomejs/biome from 2.3.11 to 2.4.3.
