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claude-fable-5-1

Claude Fable 5.1 is a featured Anthropic route for complex reasoning, long-running agents, software work, and knowledge tasks.

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Overview

  • Claude Fable 5.1 is represented in the current GPT88 featured catalog as an iterative Claude Fable route for sustained, quality-first work.
  • It is intended for workflows that need to preserve context, plan across several steps, use tools, and produce outputs with less rework. Confirm the actual features available to the current account before relying on them.
  • If Claude Fable 5 is already in use, compare the same evaluation set on both versions before changing a production default.

Best Use Cases

  • Run multi-step agent workflows with planning, tools, and failure recovery
  • Analyze large codebases, refactor across files, repair tests, and review changes
  • Process long documents, structured material, and business rules in a single workflow
  • Evaluate a new quality-first candidate within the Claude Fable family

Integration Notes

  • Use the GPT88 Base URL https://api.gpt88.cc and set model to claude-fable-5-1 in OpenAI-compatible requests.
  • Claude- or Anthropic-style clients should use the same GPT88 Base URL and send the exact model ID in their native request format.
  • Call GET /v1/models, then send a minimal POST /v1/chat/completions request before adding tools, streaming, structured output, or long context.
  • Compare it with Claude Fable 5 or Claude Opus on a fixed workload while recording completion rate, rework, latency, and usage.

Usage Notes

  • Availability, pricing, context limits, rate limits, routes, permissions, and feature support are determined by the current GPT88 console configuration.
  • A new model revision may change behavior, latency, or parameter support. Introduce it through a monitored canary instead of replacing all traffic at once.
  • High-risk requests may receive stricter safeguards or refusals; include refusal handling and human escalation in acceptance testing.
  • Keep a validated Claude Fable 5 or Claude Opus fallback until the route is stable on production-like workloads.

Capabilities

Complex reasoningLong-running agentsCode understandingTool use

Recommended Scenarios

  • Complex software tasks
  • Enterprise knowledge bases
  • Long documents
  • Multi-step automation

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/messages or POST /v1/chat/completions
Model ID
claude-fable-5-1
Content-Type
application/json
Protocol
Claude family model. Claude-native tools should prefer the Anthropic Messages protocol; OpenAI-compatible tools can use the compatibility path.
Base URL
Use https://api.gpt88.cc for Claude Code / Anthropic SDK, OpenAI SDK, Cursor, and cURL.

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 Compatible
Base URL
https://api.gpt88.cc
Endpoint
POST /v1/chat/completions
Body
{ "model": "claude-fable-5-1", "messages": [...] }
Anthropic / ClaudeRecommended
Base URL
https://api.gpt88.cc
Endpoint
POST /v1/messages
Body
{ "model": "claude-fable-5-1", "messages": [...] }

This model is in the Claude family. Claude Code, Anthropic SDK, OpenClaw, and similar tools should prefer the Anthropic / Claude path.

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: claude-fable-5-1. 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 claude-fable-5-1.
  • 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 claude-fable-5-1 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": "claude-fable-5-1",
    "messages": [
      {"role": "user", "content": "Introduce gpt88.cc in one sentence."}
    ]
  }'

Expected response (trimmed example):

200 OKjson
{
  "id": "chatcmpl-claude-f",
  "object": "chat.completion",
  "created": 1730000000,
  "model": "claude-fable-5-1",
  "choices": [
    {
      "index": 0,
      "finish_reason": "stop",
      "message": { "role": "assistant", "content": "..." }
    }
  ],
  "usage": { "prompt_tokens": 24, "completion_tokens": 64, "total_tokens": 88 }
}