March 25, 2026

fets@0.8.6

Patch Changes

• #3650
  db80dbc
  Thanks @copilot-swe-agent! - Allow optional request
  bodies in OpenAPI spec by respecting TypeBox Type.Optional modifier

  Previously, the OpenAPI plugin hardcoded requestBody.required = true for all JSON and formData
  request bodies, making it impossible to declare optional bodies using Type.Optional<...> or
  similar patterns from TypeBox.

  The plugin now checks for the TypeBox OptionalKind symbol on the schema and sets
  requestBody.required accordingly. Non-TypeBox schemas and non-optional schemas continue to
  produce required: true (preserving backward compatibility), while schemas wrapped with
  Type.Optional(...) correctly produce required: false.

  router.route({
    path: '/example',
    method: 'POST',
    schemas: {
      request: {
        json: Type.Optional(Type.Object({ name: Type.String() }))
      }
    },
    handler: () => Response.json({ ok: true })
  })
  // → requestBody.required === false in the generated OpenAPI spec

• #3662
  8c5d3e0
  Thanks @copilot-swe-agent! - Fix "Type of property
  circularly references itself" error with arrays of recursive objects

  Schemas where a recursive type is referenced through an array property (e.g.
  children: { type: 'array', items: { $ref: '#/components/schemas/Node' } }) previously triggered
  TypeScript error TS2615 when used with createClient or the OASModel / OASOutput /
  OASJSONResponseSchema helpers.

  The root cause was in the Circular<T> type helper, which only detected self-references via
  direct property values (child: Node) but not through array items (children: Node[]). After
  NormalizeOAS resolves $refs it injects a $id field onto resolved schemas, making array items
  a subtype of the parent rather than the identical type. The existing equality-based check
  therefore returned false for the array case, allowing json-schema-to-ts to try to expand the
  circular type and hit TS2615.

  A new ArrayItemValue<T> helper extracts the items schema from an array-typed JSON schema. The
  Circular<T> check now additionally tests whether any array-property's items extend the parent
  schema, correctly identifying circular array references and disabling the problematic deserializer
  expansion.

  Before (broken):

  // Node.children is an array of Node — triggered TS2615
  const client = createClient<NormalizeOAS<typeof oas>>({})
  await client['/tree'].get() // Error: Type of property 'children' circularly references itself

  After (fixed):

  const client = createClient<NormalizeOAS<typeof oas>>({})
  const res = await client['/tree'].get()
  if (res.ok) {
    const body = await res.json()
    body.children?.[0]?.children?.[0]?.number // correctly typed as number | undefined
  }

• #3665
  5fd3022
  Thanks @copilot-swe-agent! - Fix "Type of property
  circularly references itself" error for mutually-recursive schemas (e.g. Argo Workflows OpenAPI
  spec)

  Large OpenAPI specs such as Argo Workflows contain mutually-recursive schema references (e.g.
  Template → DAGTemplate → DAGTask → Template). These schemas caused TypeScript error TS2615 when
  used with OASModel, OASOutput, OASJSONResponseSchema, or createClient.

  The root cause was in the Circular<T> type helper, which detected only:

  1. Direct self-references (child: Node where Node.child resolves back to the same Node type)
  2. Array self-references added in a previous fix (children: Node[])

  It did not detect indirect mutual recursion (Schema A → Schema B → Schema A), because the
  recursive type check Circular<PropertyValue<A>> eventually calls Circular<A> again, causing
  TypeScript to hit its recursion limit and silently fail, leaving the deserializer enabled and
  triggering TS2615 inside json-schema-to-ts.

  The fix extends Circular<T> to also return true when any property of the schema is a
  resolved $ref — identified by the presence of a $id field that NormalizeOAS injects.
  Such schemas were resolved from $ref entries in the original OpenAPI document and may
  participate in complex circular reference chains. Disabling the deserializer expansion for these
  schemas avoids the TS2615 error.

  Before (broken):

  // Template → DAGTemplate → DAGTask → Template caused TS2615
  type NormalizedArgo = NormalizeOAS<typeof argoWorkflowsOAS>
  type TemplateType = OASModel<NormalizedArgo, 'Template'> // Error: TS2615
  const client = createClient<NormalizedArgo>({})
  await client['/workflow'].get() // Error: TS2615

  After (fixed):

  type NormalizedArgo = NormalizeOAS<typeof argoWorkflowsOAS>
  type TemplateType = OASModel<NormalizedArgo, 'Template'> // Works!
  const client = createClient<NormalizedArgo>({})
  const res = await client['/workflow'].get() // Works!
  if (res.ok) {
    const body = await res.json()
    body.dag?.tasks?.[0]?.name // correctly typed as string | undefined
  }

• #3652
  4c0976b
  Thanks @copilot-swe-agent! - Fix object types with
  array type (e.g. ["object", "null"]) being inferred as undefined

  OpenAPI 3.1 schemas that declare a nullable object using an array type such as
  "type": ["object", "null"] were incorrectly inferred as undefined in the feTS client instead
  of resolving to the correct union type (e.g.
  { url: string; name: string; size: number } | null).

  The root cause was in the FixJSONSchema type pipeline:

  • FixMissingTypeObject unconditionally added & { type: 'object' } to any schema with
    properties, even when type was already set. For type: ["object", "null"] this produced
    { type: ["object", "null"] } & { type: 'object' } → { type: never }, causing
    json-schema-to-ts to yield undefined.
  • FixMissingAdditionalProperties only matched type: 'object' (string literal), so schemas with
    array types never received the required additionalProperties: false injection.

  Both helpers have been updated to correctly handle array-style type declarations.

• #3649
  bce414f
  Thanks @copilot-swe-agent! - Fix client sending HTTP
  methods in lowercase (e.g. patch instead of PATCH). The client now normalizes all HTTP methods
  to uppercase before sending the request.

• #3653
  742c313
  Thanks @copilot-swe-agent! - Fix required query
  parameters becoming optional when mixed with header parameters in the client type generation.
  Previously, when an endpoint had both query and header parameters, required query parameters were
  incorrectly typed as optional. The fix correctly checks whether any parameter of the specific type
  (query or header) is marked as required: true instead of using a tuple check across all
  parameter types.

• #3651
  3d17b72
  Thanks @copilot-swe-agent! - fix: apply
  encodeURIComponent to URL path parameters in createClient

  Previously, path parameters were substituted into the URL as-is, which could result in malformed
  URLs when the parameter values contained characters such as spaces, slashes, question marks, or
  non-ASCII characters.

  For example, passing { id: 'hello world' } to /todo/{id} would produce /todo/hello world
  instead of /todo/hello%20world.

  With this fix, all path parameter values are now passed through encodeURIComponent before being
  substituted into the URL, ensuring that the generated request URL is always valid and correctly
  encoded.

• #3654
  a313e10
  Thanks @copilot-swe-agent! - Add use() method for
  router composition and merging

  Routers can now be composed together using the .use() method, allowing you to split routes
  across multiple files and merge them into a parent router.

  // users-router.ts
  const usersRouter = createRouter().route({
    path: '/users',
    method: 'GET',
    handler: () => Response.json({ users: [] })
  })
  
  // app.ts
  const app = createRouter()
    .use(usersRouter) // merge at existing paths
    .use('/api', anotherRouter) // merge under a prefix

  The .use() method supports:

  • Merging a sub-router at its existing paths
  • Merging with a path pref...

March 05, 2025

fets@0.8.5

Patch Changes

• #2475
  dc7abfe
  Thanks @renovate! - dependencies updates:
  • Updated dependency
    @whatwg-node/server@^0.10.0 ↗︎
    (from ^0.9.55, in dependencies)

November 15, 2024

fets@0.8.4

Patch Changes

• #2081
  6eeda76
  Thanks @renovate! - dependencies updates:
  • Updated dependency
    @sinclair/typebox@^0.34.0 ↗︎
    (from ^0.33.0, in dependencies)

August 16, 2024

fets@0.8.3

Patch Changes

• #1824
  047ecec
  Thanks @ardatan! - Fix nested circular references

August 07, 2024

fets@0.8.2

Patch Changes

• #1791
  0f49090
  Thanks @renovate! - dependencies updates:
  • Updated dependency
    @sinclair/typebox@^0.33.0 ↗︎
    (from ^0.32.0, in dependencies)

June 11, 2024

fets@0.8.1

Patch Changes

• #696
  61889ce
  Thanks @ardatan! - More strict on request parameters typing

• #1609
  b33d572
  Thanks @ardatan! - Support exclusiveMinimum or exclusiveMaximum
  as booleans instead of numbers only

March 25, 2024

fets@0.8.0

Minor Changes

• #1313 4f9c219 Thanks @colonel-sanders! - Support for multipart fields other than string or file

March 14, 2024

fets@0.7.2

Patch Changes

• #1238 f780f5e Thanks @renovate! - Support the latest TS version

January 02, 2024

fets@0.7.1

Patch Changes

• fc3654e Thanks @ardatan! - Use the same EMPTY_OBJECT for proxies

December 22, 2023

fets@0.7.0

Minor Changes

• #977 5c993ef Thanks @renovate! - Update typebox

Patch Changes

• #915 3be42d8 Thanks @renovate! - dependencies updates:

  • Updated dependency @sinclair/typebox@^0.32.0 ↗︎ (from ^0.31.23, in dependencies)

• #967 98d2323 Thanks @renovate! - dependencies updates:

  • Updated dependency json-schema-to-ts@^3.0.0 ↗︎ (from ^2.9.1, in dependencies)

• #977 5c993ef Thanks @renovate! - dependencies updates:

  • Updated dependency @sinclair/typebox@^0.32.0 ↗︎ (from ^0.31.23, in dependencies)