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GLM-5.3-Flash

Z.ai GLM-5.3-Flash for multimodal understanding, agentic coding, and efficient inference.

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Overview

  • As of October 24, 2026, GLM-5.3-Flash is Z.ai’s newer public GLM-5 release, announced on August 26. It is the first natively multimodal model in the GLM-5 family. GLM-5.3 is the earlier flagship; Flash focuses on inference efficiency.
  • Z.ai reports 320B total parameters, 18B active parameters, and up to 1M context. Release benchmarks and cost comparisons are vendor-reported, not a third-party controlled comparison or a guarantee for GPT88 routes.
  • Official API and weight availability do not establish GPT88 availability. Check the GPT88 console and GET /v1/models for the current API key.

Best Use Cases

  • Process images or screenshots together with text instructions
  • Generate code or run multi-step coding agents with tools
  • Evaluate the tradeoff between throughput, long context, and capability
  • Compare GLM routes on verifiable coding, visual, or office workflows

Integration Notes

  • The commonly documented model ID is glm-5.3-flash; confirm whether GPT88 uses this exact ID with GET /v1/models and the console.
  • Start with a minimal text request via the GPT88 Base URL, then validate image input, reasoning parameters, tools, and streaming separately.
  • Use fixed samples, permissions, and acceptance criteria to compare success, latency, usage, and rework against glm-5.3 or the current production model.

Usage Notes

  • Newer release does not mean it replaces GLM-5.3 as the strongest flagship; Flash is an efficiency-focused variant.
  • Z.ai Code Bench, Artificial Analysis Index, and cost claims use their respective test conditions and are reported by the source.
  • A 1M context limit does not mean every GPT88 route enables 1M context or has the same cost, speed, and cache policy.
  • GPT88 routes, price, limits, model IDs, image input, and tool support depend on the current console and API key.

Capabilities

Native multimodalLong contextCoding and agentsInference efficiency

Recommended Scenarios

  • Screenshot and image understanding
  • Coding agents
  • Long-running tool workflows
  • Frequent complex tasks

Endpoint Path

POSThttps://api.gpt88.cc/v1/chat/completions

The endpoint path is determined by the model category. Chat, image, video, and audio models use different endpoints.

Send requests with Authorization: Bearer <API_KEY>. See Chat Completions API for the full parameter reference.

API Docs

Endpoint
POST /v1/chat/completions
Model ID
glm-5.3-flash
Content-Type
application/json
Protocol
OpenAI-compatible chat completions endpoint with streaming and non-streaming output.
Base URL
Use https://api.gpt88.cc for OpenAI-compatible and Claude-style tools.

Headers / Auth

  • AuthorizationstringRequired
    Send Bearer <GPT88_API_KEY>. Create the API key in the gpt88.cc console.
  • Content-TypestringRequired
    Request body format. Audio transcription uploads use multipart/form-data.
    Default:application/json
  • Acceptstring
    Non-streaming requests return JSON; streaming chat requests return SSE chunks.
    Default:application/json or text/event-stream

Chat Protocol Differences

For chat models, the protocol used by the client matters as much as the model name. Claude Code / Anthropic SDK and OpenAI SDK build different request paths.

OpenAI CompatibleRecommended
Base URL
https://api.gpt88.cc
Endpoint
POST /v1/chat/completions
Body
{ "model": "glm-5.3-flash", "messages": [...] }
Anthropic / Claude
Base URL
https://api.gpt88.cc
Endpoint
POST /v1/messages
Body
{ "model": "glm-5.3-flash", "messages": [...] }

This model is usually best accessed through the OpenAI-compatible protocol. Only use the Anthropic-style path when the target tool explicitly requires it.

Request Parameters

The fields below are generated by model category. Pricing, context limits, rate limits, and available routes should be confirmed in the gpt88.cc console.

  • modelstringRequired
    Current model ID: glm-5.3-flash. Preserve the exact casing when copying.
  • messagesarray<Message>Required
    Conversation history. Each message includes role and content.
  • streamboolean
    Enable SSE streaming. Useful for chat interfaces and long responses.
    Default:false
  • temperaturenumber
    Sampling temperature. Higher values produce more variation; production workloads usually start with a fixed value.
    Default:1
  • max_tokensinteger
    Maximum output tokens for this request. Real context limits should be confirmed in the console.
  • response_formatobject
    Structured output config, for example { "type": "json_object" }.
  • toolsarray<Tool>
    Function-calling tool definitions. Availability depends on the model and account configuration.

Response Fields

Response bodies generally follow OpenAI-compatible shapes. Media models may return async task IDs or resource URLs.

  • idstringRequired
    Unique completion ID for tracing and debugging.
  • objectstringRequired
    Usually chat.completion or a streaming chunk type.
  • modelstringRequired
    Actual model ID that handled inference.
  • choicesarray<Choice>Required
    Generated choices including message, delta, and finish_reason.
  • usageobject
    Token usage statistics. Streaming calls may return this only at the end or in non-streaming mode.

Status Codes

  • 200OKRequired
    Request succeeded. See the response field table above for the response body shape.
  • 400Bad Request
    Invalid request fields, such as missing required fields, unsupported image size format, or unsupported file type.
  • 401Unauthorized
    API key is missing, invalid, or malformed.
  • 404Not Found
    Endpoint or model not found. Confirm the path is /v1/chat/completions and the model ID is glm-5.3-flash.
  • 429Rate Limited
    Rate limit, concurrency cap, or insufficient balance. Check the console for the current allowance.
  • 5xxUpstream Error
    Upstream or request failure. Retry with the same Base URL and keep the request ID for debugging.

Errors and Troubleshooting

  • 401: verify Authorization is Bearer <API_KEY> and the key is still valid.
  • 404: confirm the endpoint is /v1/chat/completions and the model ID glm-5.3-flash is available in the console.
  • 429: reduce concurrency, shorten requests, or check balance and quota in the console.
  • 5xx: retry with the same Base URL and keep the request ID for debugging.

Request Examples

curl https://api.gpt88.cc/v1/chat/completions \
  -H "Authorization: Bearer $GPT88_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "glm-5.3-flash",
    "messages": [
      {"role": "user", "content": "Introduce gpt88.cc in one sentence."}
    ]
  }'

Expected response (trimmed example):

200 OKjson
{
  "id": "chatcmpl-glm-5-3-",
  "object": "chat.completion",
  "created": 1730000000,
  "model": "glm-5.3-flash",
  "choices": [
    {
      "index": 0,
      "finish_reason": "stop",
      "message": { "role": "assistant", "content": "..." }
    }
  ],
  "usage": { "prompt_tokens": 24, "completion_tokens": 64, "total_tokens": 88 }
}