JSON-body endpoints (Content API, Messaging v2) send camelCase request keys verbatim — request types don't match the snake_case wire format

[simllll]

Description

For endpoints whose request bodies are sent as application/json (e.g. Content API content.v1.contents.create(), Messaging v2 messaging.v2.channelsSenders(sid).update()), the generated client sends the params object verbatim (data = params) and never converts the camelCase TypeScript property names to the snake_case keys the REST API expects. Because the generated request types are also camelCase, typed code compiles cleanly but produces an invalid request body on the wire.

Form-encoded endpoints are not affected: their generated code explicitly maps each field, e.g. in trunking/v1/trunk.js:

data["FriendlyName"] = params["friendlyName"];
headers["Content-Type"] = "application/x-www-form-urlencoded";

The JSON endpoints instead do:

data = params;
headers["Content-Type"] = "application/json";

Reproduction (no network needed)

import twilio from "twilio";
const client = twilio("ACxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx", "fake_token");

client.httpClient.axios.interceptors.request.use((c) => {
  console.log(`${c.method.toUpperCase()} ${c.url}`);
  console.log(`Body: ${typeof c.data === "string" ? c.data : JSON.stringify(c.data)}`);
  return Promise.reject(new Error("stop-before-network"));
});

await client.content.v1.contents.create({
  friendlyName: "qr",
  language: "en",
  types: { twilioQuickReply: { body: "Pick", actions: [{ id: "a", title: "Yes" }] } },
}).catch(() => {});

Output (twilio@6.0.2, node 22):

POST https://content.twilio.com/v1/Content
Body: {"friendlyName":"qr","language":"en","types":{"twilioQuickReply":{"body":"Pick","actions":[{"id":"a","title":"Yes"}]}}}

Sending that body to the real API returns Invalid types. At least one content type definition is required, because the Content API expects friendly_name and the content-type key twilio/quick-reply. The same pattern on channelsSenders().update({ webhook: { callbackUrl, callbackMethod } }) returns error 63100 Update request body is empty (it expects callback_url / callback_method).

Expected

Either (a) the serializer converts camelCase request properties to the snake_case wire keys for JSON endpoints — mirroring what's already done for form endpoints — or (b) the generated request types reflect the actual wire keys.

Actual

camelCase types + verbatim passthrough → request body the API rejects. Note the response resource classes already read snake_case (payload["friendly_name"]), so the request and response sides are internally inconsistent.

Workaround

Build the body with snake_case / slash-delimited keys and cast past the camelCase types.

Versions

twilio 5.13.1 and 6.0.2; Node 22. Reproduces on both.

[Maders]

We hit this too, and it's still happening on 6.1.0. Adding what I found while confirming it, in case it helps narrow things down.

it comes out of the generator. twilio-oai-generator:

{{#queryParams}}{{>requestParam}}{{/queryParams}}
{{#formParams}}{{>requestParam}}{{/formParams}}
{{#bodyParam}}data = params{{/bodyParam}}

Query and form params get run through requestParam.mustache, which does the data["{{{baseName}}}"] = params["{{paramName}}"] mapping. Body params skip it. That seems to be where the asymmetry in the description comes from.

On why CI wouldn't have caught it: every requestBody in examples/spec/*.yaml is application/x-www-form-urlencoded. There's no JSON-body operation in the example specs at all, so the affected code path never shows up in the generated output that gets reviewed.