5.50.3
(fix): Fixes translated locales in ledger publishing mode (currently opt-in).
(fix): Fixes translated locales in ledger publishing mode (currently opt-in).
(fix): Fixed the local C# dynamic-snippet test runner so it strips the docs-only
exported-client-class-name override before generating snippet tests. The compiled snippets now
reference the generated client class instead of the customer-provided wrapper, which is not part
of generator output.
(fix): Add retry with exponential backoff to registerApiDefinition during docs
publish. Large docs sites (e.g. 30+ API versions) could hit transient
connection aborts from FDR; the CLI now retries up to 3 times with
1 s / 2 s / 4 s delays before failing.
(chore): Bump js-yaml to 4.2.0 across all transitive dependencies to fix
CVE-2026-53550 (quadratic-complexity DoS in merge key handling).
(feat): Add docs deployment ledger. Set FERN_DOCS_DEPLOY_MODE=ledger to
publish via the new ledger backend; legacy (default) uses the
existing register flow. The ledger path uses content-addressed
storage for incremental deploys and supports multi-locale
translations (including localized API reference content with
per-locale apiManifest blobs and sidebar titles), custom JS
components, favicon resolution, git provenance metadata,
multi-domain forwarding, stable file-path references in page
markdown, MIME-type inference for uploads, and a dedicated preview
endpoint.
(fix): When a generator breaks an import cycle by relocating types into a shared
package, the local generation runner now applies those relocations to the IR
that powers host-side dynamic snippet test generation. This keeps the
generated dynamic snippets referencing each relocated type from the same
package the generator declares it in, fixing undefined-symbol compile errors
in the Go SDK’s dynamic snippet tests.
(fix): infer-discriminated-union-base-properties now lifts properties that every variant inherits via a shared allOf $ref parent. Previously these were dropped to protect TypeScript’s _Base from colliding with the real parent interface, which left Go and C# unions missing common fields like id, name, and display_name.
(fix): Library docs generator now writes module overview pages as index.mdx inside their
directory (e.g. adapters/index.mdx) instead of as sibling files (adapters.mdx),
eliminating duplicate entries in the sidebar for library autodocs output.
(feat): Add support for x-fern-subtitle OpenAPI extension on endpoints. When set,
the subtitle is rendered below the endpoint title in the docs UI.
(feat): Add a --local flag to fern docs md generate that runs the library
documentation parsers locally in Docker instead of using Fern’s servers.
Local generation requires no authentication and operates on path inputs
(local source); git inputs continue to be generated remotely.
(fix): Fix frontmatter values with leading zeros being corrupted during docs publish.
grayMatter.stringify() in parseImagePaths would strip quotes from values
like '001999' (non-octal digits), causing downstream YAML 1.2 parsers to
interpret them as integers and lose leading zeros.
(fix): Fix v3 OpenAPI importer dropping types that are only referenced through a
list/map of a $ref when audience filtering is enabled. Array and map
aliases now record the referenced named type in referencedTypes (matching
how object properties already do), so audience reachability no longer prunes
the referenced type and leaves a dangling reference. This restores the
“Show N variants” UI in docs for discriminated unions referenced via a list
(e.g. Cohere’s v2 chat messages field under an audience filter).
(fix): Group GraphQL queries by parent field in the sidebar; mutations and subscriptions remain flat. Field path is now included on all GraphQL operations for correct snippet nesting.
(fix): Include field-level arguments when converting GraphQL object types and interfaces
to FDR format. Previously, arguments were only captured for top-level query/mutation
fields but not for nested object type fields (e.g., Image.url(width, height, lossy)).
Namespace grouping types (object types whose fields are all promoted to top-level
operations) are no longer double-registered as plain type definitions.
(fix): Use string literal for this.name in error classes instead of
this.constructor.name, which gets mangled by minifiers.
(fix): Fix text/* content types (e.g. text/csv, text/xml) being silently converted
to text/plain during OpenAPI export. The original media type is now preserved
through the IR via a new optional contentType field on TextResponse.
(fix): Stop dropping custom scalars in the GraphQL converter. Custom scalars (e.g. DateTime,
URL, EmailAddress) are now emitted as named alias types in the types map with a stable
id, and references to them point to that id so the type can be linked to in documentation.
(fix): Fix v3 OpenAPI importer producing empty discriminated unions when
discriminator.propertyName is present but discriminator.mapping is absent.
The importer now infers the mapping from oneOf/anyOf $ref schemas,
using const/single-element enum values on the discriminant property
(falling back to the schema name from the $ref path). This restores the
“Show N variants” UI in docs for specs like Cohere’s chat messages field.
(feat): Add page-actions.options.skills to docs.yml to enable and configure the “Install skills”
page action on docs sites. Presence of the key enables the action (an empty object enables it
with all defaults); title, description, learn-more-url, repository, and
install-command (string or list, rendered one command per line) customize the modal, and
skills lists the available skills. If the site also serves a /.well-known skills manifest,
the served manifest replaces the hand-listed skills.
(feat): Upload Agent Skills bundles placed under .well-known/skills/ or .well-known/agent-skills/
in the docs folder when publishing docs, so Fern-hosted docs sites serve them and
npx skills add https://<docs-domain> installs them. fern check now validates skill
bundles: the index.json discovery manifest must exist and parse, and each skill’s
SKILL.md frontmatter needs a kebab-case name (max 64 characters) matching its parent
directory and a non-empty description (max 1024 characters).
(fix): Bump bundled @fern-api/replay (via generator-cli 0.9.38) to 0.18.0: replay
detection filters .fernignore-protected files before materializing patches,
handles trailing-slash patterns like docs/, and no longer crashes with an
unhandled write EPIPE during patch application.
(feat): Add OIDC support for PyPI publishing in local generation. When
token: OIDC is configured for a PyPI output, the CLI now detects
the OIDC credential and propagates it through both the GitHub publish
info and the publish config so the Python generator can activate its
OIDC trusted-publisher workflow.
(feat): Track which validation rules fired during fern check as part of the PostHog CLI telemetry event.
The event now includes validationRules (array of rule names that produced violations),
numErrors, numWarnings, and passed properties.
(fix): Bump @fern-api/generator-cli to 0.9.36: AutoVersionStep now calls the hosted FAI
service with fernToken when no BAML ai config is supplied, restoring real
version bumps and changelog entries for replay-enabled remote generations.