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Claude Fable 5.1
Send a message to test this OpenAI-compatible chat completions model.
探索不同用例和参数配置
claude-fable-5-1 使用完整指南
Unlock OpenAI's flagship model for complex, long-horizon agentic tasks with seamless integration and affordable pricing.
Claude Fable 5.1 is OpenAI’s most capable flagship model to date, engineered specifically to handle long-horizon agentic tasks where the AI must plan, manage multi-step processes, use tools, and make autonomous decisions over extended periods. While traditional models excel at completing single prompts, Claude Fable 5.1 is built to orchestrate actions and recover from errors mid-task without requiring constant human hand-holding. Through ApiPass, developers can access this premium model using a standard, OpenAI-compatible API endpoint, making it easy to integrate the world's most advanced reasoning engine into your applications reliably and affordably.
Every request should include a messages array in standard chat format. The adapter forwards this field directly to the upstream provider.
You can provide temperature to control sampling behavior. If omitted, the adapter leaves it out of the upstream request.
You can send max_tokens to limit completion length. If omitted, the upstream provider decides the response length.
Claude Fable 5.1 drastically reduces the occurrence of "stuck" agents. If a tool call fails or a task goes off track, the model is highly capable of detecting its own mistakes mid-task, backtracking, and trying a new approach rather than failing or looping indefinitely.
Tool calling is more efficient and precise than ever before. Claude Fable 5.1 makes fewer redundant tool calls and introduces native support for parallel tool invocations—allowing it to call multiple tools simultaneously to reduce latency and save on token costs.
While many models lose track of early instructions during lengthy sessions, Claude Fable 5.1 maintains strict coherence deep into long conversations and task threads. This makes it ideal for analyzing massive documents, entire codebases, or maintaining full context across multi-step workflows.
Non-streaming responses are normalized into content plus prompt_tokens, completion_tokens, total_tokens, and cost fields for downstream consumers.
Beyond standard text generation, Claude Fable 5.1 seamlessly handles mixed-media inputs including images and documents. It is exceptionally strong at high-level scientific, legal, and mathematical reasoning, as well as complex code generation and debugging.
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Create an account on apipass.dev and generate your secure API key for authentication.
Point your API client or HTTP request to the ApiPass chat completions endpoint: `https://api.apipass.dev/v1/chat/completions`.
Include your API key in the request headers. Format it as: `Authorization: Bearer YOUR_API_KEY`.
Build your JSON request body using standard OpenAI message formatting. Crucially, set the model parameter to `claude-fable-5-1`.
Send your request. You will receive a standard Chat Completion response object. You can also test your prompts and model behavior visually using the ApiPass Playground before pushing to production.
In multi-agent architectures, deploy Claude Fable 5.1 as the primary decision-maker and orchestrator, while delegating repetitive sub-tasks (like basic formatting or retrieval) to smaller, faster sub-agents.
Because Claude Fable 5.1 is a premium tier model with a higher token cost, use it for complex, long-running workflows where the cost of failure is high. For shorter, high-volume, or simple tasks, route requests to cheaper models like GPT-5.4.
Claude Fable 5.1 performs exceptionally well when given outcomes rather than rigid step-by-step instructions. Tell the model what the final goal is and let its agentic reasoning plan the steps.
Agentic applications often require passing the same large system prompts or contexts repeatedly. Take advantage of cached input discounts by reusing contexts to lower your overall API spend.
Use Claude Fable 5.1 to power coding agents that can plan full application architectures, write code, debug errors, and manage multiple files simultaneously without getting stuck.
Build tools that read, summarize, and extract nuanced data from hundreds of pages of legal, medical, or academic documents without losing context.
Deploy agents that operate for minutes or hours, executing complex loops like taking a product requirement, calling database tools, writing specifications, and deploying code.
Feed the model raw, anonymized datasets (CSV, XLS) and have it autonomously analyze the data, generate hypotheses, and draft highly technical reports or academic literature.
所有 API 都需要通过 Bearer Token 进行身份验证。
Authorization: Bearer
Generate text with claude-fable-5-1 through the ApiPass OpenAI-compatible chat completions endpoint.
Send an OpenAI-compatible JSON request body. ApiPass routes claude-fable-5-1 to the APIPASS adapter, which forwards the chat payload to APIPASS's LLM endpoint.
1{
2 "model": "claude-fable-5-1",
3 "messages": [
4 {
5 "role": "user",
6 "content": "Hello!"
7 }
8 ],
9 "stream": false,
10 "temperature": 0.7,
11 "max_tokens": 512,
12 "channel": "auto"
13}model必填stringThe public ApiPass model name. The APIPASS adapter also accepts the gpt-5.5 alias and maps it upstream to claude-fable-5-1.
"claude-fable-5-1"
messages必填array<object>OpenAI-style chat messages array. The adapter requires a non-empty list, and each message object must include role and content.
[{"role":"user","content":"Write a short product announcement for APIPASS Claude Fable 5.1 support in ApiPass."}]stream可选booleanSet to true to receive Server-Sent Events. When false or omitted, ApiPass returns a single OpenAI-compatible chat.completion response.
false
temperature可选numberOptional sampling temperature from 0 to 2. If omitted, the adapter does not include temperature in the upstream request.
Allowed range: 0 to 2
0.7
max_tokens可选integerOptional maximum number of completion tokens. If omitted, the upstream provider decides the response length.
Must be greater than 0 when provided
512
top_p可选numberOptional nucleus sampling value accepted by the ApiPass chat endpoint and forwarded to APIPASS when supplied.
Allowed range: 0 to 1
0.9
frequency_penalty可选numberOptional OpenAI-compatible frequency penalty accepted by ApiPass and forwarded when supplied.
Allowed range: -2 to 2
0
presence_penalty可选numberOptional OpenAI-compatible presence penalty accepted by ApiPass and forwarded when supplied.
Allowed range: -2 to 2
0
response_format可选objectOptional response format object accepted by the ApiPass chat endpoint and forwarded to the provider if present.
{"type":"json_object"}tools可选array<object>Optional OpenAI-compatible tools array. ApiPass accepts tool definitions and forwards them to APIPASS when supplied; support depends on the upstream model.
[{"type":"function","function":{"name":"lookup_order","description":"Look up an order by ID","parameters":{"type":"object","properties":{"order_id":{"type":"string"}},"required":["order_id"]}}}]include_thoughts可选booleanOptional provider-specific flag accepted by ApiPass and forwarded when true.
false
reasoning_effort可选stringOptional reasoning effort value accepted by the ApiPass chat endpoint and forwarded to the provider when supplied.
可用选项：
"low"
_provider_config_id可选stringOptional ApiPass routing override. Supply a provider_model_configs.id to force this request to a specific configured APIPASS provider.
"provider-config-id"
channel可选stringYou may specify the corresponding provider within APIPASS via the channel parameter; these providers handle the actual image and video generation tasks. APIPASS currently offers three provider options:
The default value for the channel parameter is auto. When enabled, APIPASS automatically allocates tasks across available providers based on real-time pricing and stability metrics to balance minimal cost and reliable performance. Retain the default auto value unless you have custom routing requirements.
可用选项：
auto
Each item in the messages array follows the OpenAI chat message shape validated by ApiPass before the APIPASS adapter is called.
messages[].role必填stringMessage role. ApiPass accepts developer, system, user, and assistant roles in the chat request model.
可用选项：
"user"
messages[].content必填stringMessage content. For Claude Fable 5.1 text generation, use plain text content for the most predictable provider behavior.
"Summarize the following text in three concise bullets."
1curl -X POST "https://api.apipass.dev/v1/chat/completions" \
2 -H "Content-Type: application/json" \
3 -H "Authorization: Bearer YOUR_API_KEY" \
4 -d '{
5 "model": "claude-fable-5-1",
6 "messages": [
7 {
8 "role": "system",
9 "content": "You are a precise and concise assistant."
10 },
11 {
12 "role": "user",
13 "content": "Write a short product announcement for APIPASS Claude Fable 5.1 support in ApiPass."
14 }
15 ],
16 "temperature": 0.7,
17 "max_tokens": 512,
18 "stream": false
19 }'1{
2 "id": "chatcmpl_gpt_5_5_demo",
3 "object": "chat.completion",
4 "created": 1765968190,
5 "model": "claude-fable-5-1",
6 "choices": [
7 {
8 "index": 0,
9 "message": {
10 "role": "assistant",
11 "content": "ApiPass now supports APIPASS Claude Fable 5.1 through the standard OpenAI-compatible chat completions endpoint."
12 },
13 "finish_reason": "stop"
14 }
15 ],
16 "usage": {
17 "prompt_tokens": 35,
18 "completion_tokens": 19,
19 "total_tokens": 54
20 }
21}idApiPass chat completion response ID.
objectResponse object type. Non-streaming calls return chat.completion.
modelThe public model name used for the request.
choices[0].message.contentAssistant reply text extracted from the APIPASS OpenAI-compatible response.
choices[0].finish_reasonCompletion finish reason. ApiPass returns stop for successful non-streaming Claude Fable 5.1 completions.
usage.prompt_tokensPrompt token count reported by the upstream provider.
usage.completion_tokensCompletion token count reported by the upstream provider.
usage.total_tokensTotal token count used for ApiPass usage accounting.
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