{
  "id": "format.parse_mode_unsupported",
  "category": "formatting",
  "summary": "The requested parse_mode is unsupported.",
  "match_any": [
    {
      "error_code": 400,
      "description_exact": "Bad Request: unsupported parse_mode"
    }
  ],
  "scope": {
    "method_examples": [
      "sendMessage",
      "editMessageText",
      "sendPhoto"
    ],
    "exhaustive": false
  },
  "possible_causes": [
    "Nonempty text was supplied with a parse_mode that the server does not recognize."
  ],
  "diagnostic_limits": "The server lowercases parse_mode before checking it. This response does not identify a malformed entity inside a supported mode.",
  "evidence": [
    {
      "source": "live-2026-09-16",
      "note": "sendMessage with an unsupported parse_mode returned this description."
    },
    {
      "source": "server-10.3",
      "path": "telegram-bot-api/Client.cpp",
      "lines": [
        11961,
        11977
      ],
      "note": "Nonempty text accepts markdown, markdownv2, html, or the no-parsing path; other modes fail."
    },
    {
      "source": "server-10.3",
      "path": "telegram-bot-api/Client.cpp",
      "lines": [
        13800,
        13803
      ],
      "note": "Method validation errors are passed to the response normalizer."
    },
    {
      "source": "server-10.3",
      "path": "telegram-bot-api/Client.cpp",
      "lines": [
        165,
        205
      ],
      "note": "Adds the code-specific prefix and lowercases only the initial character of ordinary messages."
    }
  ],
  "example": {
    "method": "sendMessage",
    "response": {
      "ok": false,
      "error_code": 400,
      "description": "Bad Request: unsupported parse_mode"
    }
  },
  "evidence_level": "observed",
  "guidance": {
    "action": "correct_parse_mode",
    "repeat_request": "after_relevant_change",
    "preconditions": [
      "Choose a supported parse_mode, or omit it and use plain text or explicit entities."
    ]
  }
}