ResponsesRequest fails to marshal when ServiceTier is omitted

[ell-hol]

Summary

components.ResponsesRequest fails to marshal when ServiceTier is omitted.

This happens before any HTTP request is sent, during local JSON serialization.

I opened a PR with a minimal reproduction and proposed a fix #300

I saw the contributing guide says this repository contains generated code and does not accept direct code changes, so I am opening this issue as the official report and linking the PR for context.

Reproduction

This code fails when ServiceTier is not explicitly set:

package main

import (
	"context"
	"fmt"
	"log"
	"os"

	openrouter "github.com/OpenRouterTeam/go-sdk"
	"github.com/OpenRouterTeam/go-sdk/models/components"
)

func main() {
	ctx := context.Background()

	s := openrouter.New(
		openrouter.WithSecurity(os.Getenv("OPENROUTER_API_KEY")),
	)

	res, err := s.Beta.Responses.Send(ctx, components.ResponsesRequest{
		Input: openrouter.Pointer(
			components.CreateInputsUnionStr("Hey there"),
		),
		Model:  openrouter.Pointer("openai/gpt-4o-mini"),
		Stream: openrouter.Bool(true),
	}, nil)

	if err != nil {
		log.Printf("error type: %T", err)
		log.Printf("error value: %+v", err)
		log.Fatal(err)
	}

	if res != nil {
		defer res.EventStream.Close()

		for res.EventStream.Next() {
			event := res.EventStream.Value()
			delta := event.Data.TextDeltaEvent.GetDelta()
			fmt.Print(delta)
		}
	}
}

Actual behavior

The request fails before reaching the API:

error serializing request body: json: error calling MarshalJSON for type components.ResponsesRequest:
json: error calling MarshalJSON for type json.RawMessage:
invalid character 'a' looking for beginning of value

The same issue also happens with Stream: openrouter.Bool(false), so the problem is not streaming-specific.

A minimal local reproduction is:

req := components.ResponsesRequest{
	Input: openrouter.Pointer(
		components.CreateInputsUnionStr("Hey there"),
	),
	Model:  openrouter.Pointer("openai/gpt-4o-mini"),
	Stream: openrouter.Bool(false),
}

_, err := json.Marshal(req)

This fails with the same serialization error.

Expected behavior

ResponsesRequest should marshal successfully when ServiceTier is omitted.

Since ResponsesRequest.ServiceTier has:

ServiceTier optionalnullable.OptionalNullable[ResponsesRequestServiceTier] `default:"auto" json:"service_tier"`

the generated JSON should either omit service_tier or serialize the default as a valid JSON string:

"service_tier": "auto"

Root cause

The default value auto appears to be emitted as raw JSON:

auto

That is invalid JSON. It should be emitted as:

"auto"

This explains why explicitly setting ServiceTier works:

serviceTier := components.ResponsesRequestServiceTierAuto

ServiceTier: optionalnullable.From(&serviceTier)

In that case, the enum value goes through the normal marshaling path and is serialized correctly.

Notes

The linked PR adds a regression test showing the failure and a small patch that prevents non-JSON default tag values from being emitted as raw JSON.

Full test suite passed locally with:

go test ./...

Environment:

github.com/OpenRouterTeam/go-sdk v0.5.0
Go: go1.26.3
OS: macOS amd64