react-query generator uses { data } for SSE endpoints (ServerSentEventsResult) causing TS2339; should use stream

[hqw567]

Description

Bug report

When using text/event-stream (SSE) responses, openapi-ts generates a TanStack React Query mutation that destructures { data } from the client call, but the generated client returns ServerSentEventsResult<...> (no data field). This causes TypeScript errors like TS2339: Property 'data' does not exist on type 'ServerSentEventsResult<...>'.

OpenAPI snippet (minimal)

/api/v1/documents/{domain_id}/ingest_permanent_document_batch:
  post:
    summary: Ingest permanent documents and link them to assistants.
    description: Uses Server-Sent Events (SSE) to stream progress updates.
    parameters:
      - name: domain_id
        in: path
        required: true
        schema:
          type: string
          format: uuid
    requestBody:
      required: true
      content:
        multipart/form-data:
          schema:
            $ref: "#/components/schemas/Body_ingestPermanentDocumentBatch"
    responses:
      "200":
        description: SSE stream with progress updates
        content:
          text/event-stream:
            schema:
              oneOf:
                - $ref: "#/components/schemas/BatchIngestionSSEUpdate"
                - $ref: "#/components/schemas/BatchIngestionSSEResult"
                - $ref: "#/components/schemas/BatchIngestionSSEError"

Generated code (problem)

File: src/services/_openapi/.../@tanstack/react-query.gen.ts

mutationFn: async (fnOptions) => {
  const { data } = await PostSse({
    ...options,
    ...fnOptions,
    throwOnError: true,
  })
  return data
}

TypeScript error

error TS2339: Property 'data' does not exist on type
'ServerSentEventsResult<PostSseResponses, PostSseErrors>'.

const { data } = await PostSse(...)
        ^^^^ no data on SSE result

Expected behavior

For SSE endpoints, the generated mutation should NOT assume a JSON response with data.
Instead it should return the SSE stream result, e.g.:

mutationFn: async (fnOptions) => {
  const { stream } = await PostSse({
    ...options,
    ...fnOptions,
    throwOnError: true,
  })
  return stream
}

(or return the entire ServerSentEventsResult object, depending on the intended API.)

Actual behavior

Generator always emits { data } = await <operation>() and return data, even for SSE endpoints.

Environment

• openapi-ts: 0.90.3
• generator: @tanstack/react-query
• TypeScript: 5.9
• runtime: axios

Reproducible example or configuration

No response

OpenAPI specification (optional)

No response

System information (optional)

No response

[mrlubos]

@hqw567 I'm aware of this issue but my impression was TanStack Query doesn't play nice with SSE. Is that not true?

[hqw567]

@hqw567 I'm aware of this issue but my impression was TanStack Query doesn't play nice with SSE. Is that not true?

I agree TanStack Query shouldn’t manage SSE automatically, but this is a codegen bug: the operation returns ServerSentEventsResult, yet the react-query generator still emits { data }. For SSE endpoints it should return the stream directly.

[hqw567]

Per the docs, POST/PUT/PATCH/DELETE are classified as mutation operations by default.
The mutation defaults should be updated to exclude text/event-stream responses
Ref: https://heyapi.dev/openapi-ts/configuration/parser#hooks-query-operations

[mrlubos]

@hqw567 so the request in this issue is to avoid generating TanStack Query options for SSE endpoints? Or are you trying to use TanStack Query with SSE?

[hqw567]

To clarify: I’m not trying to use TanStack Query to manage SSE logic.
I’m only pointing out that SSE endpoints can still be used with useMutation, so the generator shouldn’t break or assume { data }.

const m = useMutation({
 ...
  onSuccess: async (stream) => {
    for await (const evt of stream) {
      // update local state/store with progress events
    }
  },
})