grpc-ecosystem/grpc-gateway · error

invalid header parameter type: %+v

Error message

invalid header parameter type: %+v

What it means

Schema-mapping error in genopenapi renderServices: an openapi_options HeaderParameter has a type enum value outside the known STRING/NUMBER/INTEGER/BOOLEAN set, so the generator cannot map it to an OpenAPI parameter type. The failing input is the header parameter option with the unsupported type value.

Solutions

1. Set the header parameter's type to one of STRING, NUMBER, INTEGER, or BOOLEAN in the openapiv2 options.
2. Regenerate if a newer plugin supports additional header types.

When it happens

Trigger: Thrown at protoc-gen-openapiv2/internal/genopenapi/template.go:2190 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grpc-ecosystem/grpc-gateway@a58a4436a3 (2026-09-02). Data as JSON: /api/errors/851fe7b93f694d11. Report an issue: GitHub.

Appendix: source

Thrown at protoc-gen-openapiv2/internal/genopenapi/template.go:2190

							param := openapiParameterObject{
								In:          "header",
								Name:        header.Name,
								Description: header.Description,
								Required:    header.Required,
								Format:      header.Format,
							}

							switch header.Type {
							case openapi_options.HeaderParameter_STRING:
								param.Type = "string"
							case openapi_options.HeaderParameter_NUMBER:
								param.Type = "number"
							case openapi_options.HeaderParameter_INTEGER:
								param.Type = "integer"
							case openapi_options.HeaderParameter_BOOLEAN:
								param.Type = "boolean"
							default:
								return fmt.Errorf("invalid header parameter type: %+v", header.Type)
							}

							operationObject.Parameters = append(operationObject.Parameters, param)
						}
					}

					// TODO(ivucica): add remaining fields of operation object
				}

				switch b.HTTPMethod {
				case "DELETE":
					pathItemObject.Delete = operationObject
				case "GET":
					pathItemObject.Get = operationObject
				case "POST":
					pathItemObject.Post = operationObject
				case "PUT":
					pathItemObject.Put = operationObject

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