fix: parseJsonBody sends 500 for malformed JSON instead of 400

[iRonin]

Problem

parseJsonBody() in worker/http.ts validates Content-Type but does not wrap request.json():

export function parseJsonBody<T = unknown>(request: Request): Promise<T> {
  const contentType = request.headers.get("content-type") || "";
  if (contentType && !contentType.toLowerCase().includes("application/json")) {
    throw new HttpError("Content-Type must be application/json", 415);
  }
  return request.json() as Promise<T>;
}

If the body contains malformed JSON, request.json() throws a raw SyntaxError. This bypasses HttpError handling and gets caught by the top-level try/catch in handleRequest, which renders it as a 500 internal_error instead of a 400 invalid_json.

Location

worker/http.ts — parseJsonBody()

Proposed Fix

export async function parseJsonBody<T = unknown>(request: Request): Promise<T> {
  const contentType = request.headers.get("content-type") || "";
  if (contentType && !contentType.toLowerCase().includes("application/json")) {
    throw new HttpError("Content-Type must be application/json", 415);
  }
  try {
    return (await request.json()) as T;
  } catch {
    throw new HttpError("Invalid JSON in request body", 400, "invalid_request_error");
  }
}

Impact

• Fixes incorrect HTTP status code for malformed JSON
• Returns proper OpenAI-compatible error response
• No API change for valid requests