GLM-5.3-Flash

Model IDs

Model ID
`zai-org/GLM-5.3-Flash`
`zai-org/GLM-5.3-Flash-ultra`

Both IDs serve the same model and accept the same parameters. Each ID has its own rates and rate limits, listed on the Models and Limits pages.

Limits

Limit	Tokens
Context length	1,048,576
Max output	131,072

The context length covers the input and max_tokens together. A request whose input plus max_tokens exceeds it returns 400. A max_tokens above 131,072 is accepted, but output stops at 131,072 tokens.

Thinking

GLM-5.3-Flash always thinks, and thinking cannot be turned off. "reasoning_effort": "none" and "thinking": {"type": "disabled"} are not supported for this model, so don’t send them. reasoning_effort accepts minimal, low, medium, high, xhigh and max. Any other value returns 400. The reasoning arrives in message.reasoning_content, or in delta.reasoning_content when streaming, separate from content. usage.completion_tokens_details.reasoning_tokens counts it. Reasoning tokens are part of completion_tokens and are billed as output. max_tokens covers the reasoning and the answer together. If the reasoning uses the whole budget, the response ends with finish_reason: "length" and an empty content. Stop sequences are matched in the reasoning too, so a match there ends the response before the answer starts.

Parameters

Parameter	Notes
`max_tokens`, `max_completion_tokens`	Cover reasoning and answer together.
`temperature`	0 to 2.
`top_p`	Greater than 0, up to 1.
`top_k`, `presence_penalty`, `frequency_penalty`	Accepted.
`stop`	Also matched in the reasoning.
`seed`	Accepted, but does not make output reproducible.
`stream`, `stream_options`	Every stream ends with a usage chunk, with or without `include_usage`.
`tools`, `tool_choice`	`auto`, `required`, `none` or a named function.
`response_format`	`text`, `json_object` and `json_schema`.
`reasoning_effort`	See Thinking.
`user`	Accepted.

These return 400:

Parameter	`error.code`	`error.message`
`n` other than `1`	`unsupported_n`	`n must be 1`
`logprobs`, even `false`	`unsupported_parameter`	the parameter `logprobs` is not supported
`top_logprobs`	`unsupported_parameter`	the parameter `top_logprobs` is not supported
`logit_bias`	`unsupported_parameter`	the parameter `logit_bias` is not supported
Fields the API does not define, such as `chat_template_kwargs`	`unknown_parameter`	`unrecognized request argument supplied: chat_template_kwargs`

{
  "error": {
    "message": "the parameter `logprobs` is not supported",
    "type": "invalid_request_error",
    "param": null,
    "code": "unsupported_parameter"
  }
}

Out-of-range values, such as temperature: 3 or top_p: 0, also return 400.

Getting Started

Models

Inference APIs

Account

Model IDs

Limits

Thinking

Parameters

​Model IDs

​Limits

​Thinking

​Parameters

Model IDs

Limits

Thinking

Parameters