GPT-6 Astra

GPT-6 Astra is OpenAI’s GPT-6 flagship model for complex reasoning, coding, research, computer use, and document creation. Use the model ID gpt-6-astra with the OpenAI-compatible Responses API at POST /v1/responses.

gpt-6-astra is available from both POST /v1/responses and POST /v1/chat/completions. Use the Responses API for tools, image and file input, Structured Outputs, and prompt caching.

Model specifications

Property	Value
Model ID	`gpt-6-astra`
Recommended API	Responses API
Input	Text and image
Output	Text
Context window	1,050,000 tokens
Maximum input	922,000 tokens
Maximum output	128,000 tokens
Knowledge cutoff	April 30, 2026
Reasoning effort	`low`, `medium`, `high`, `xhigh`, `max`
Fine-tuning	Not supported

Key capabilities

Long-context reasoning — Analyze large codebases, documents, and multi-step workflows within a 1.05M-token context window.
Software engineering — Plan and execute long-running coding tasks across files, tools, and verification steps.
Vision — Accept image input together with text instructions.
Structured Outputs — Return JSON that follows a supplied schema.
Prompt caching — prompt_cache_key and prompt_cache_options support the 30m cache lifetime and expose cache-write and cache-hit token counts.
Responses API tools — Web search, code interpreter, hosted shell, apply patch, computer use, MCP, function tools, and custom tools are available through AnyFast.
Async tool calling — Function and custom tools accept async: true and return the corresponding tool-call item.

Capability examples

Text and reasoning
Image and file input
Structured output
Tool workflows

Use reasoning.effort to balance latency and reasoning depth. GPT-6 Astra accepts low, medium, high, xhigh, and max.

cURL

curl https://www.anyfast.ai/v1/responses \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-6-astra",
    "input": "Review this retry design, identify race conditions, and propose a safe implementation plan.",
    "reasoning": {
      "effort": "high",
      "summary": "auto"
    },
    "max_output_tokens": 4096
  }'

Add an input_image part for diagrams, screenshots, or charts. Use input_file with inline Base64 data when you need to analyze a document.

cURL

curl https://www.anyfast.ai/v1/responses \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-6-astra",
    "input": [{
      "role": "user",
      "content": [
        { "type": "input_text", "text": "Find the failure point in this architecture diagram." },
        { "type": "input_image", "image_url": "data:image/png;base64,<BASE64_IMAGE_DATA>", "detail": "high" },
        { "type": "input_file", "filename": "deployment-notes.pdf", "file_data": "data:application/pdf;base64,<BASE64_PDF_DATA>" }
      ]
    }],
    "reasoning": { "effort": "high" }
  }'

Set text.format.type to json_schema and provide a strict schema when your application needs machine-readable output.

cURL

curl https://www.anyfast.ai/v1/responses \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-6-astra",
    "input": "Classify the deployment risk as low, medium, or high.",
    "text": {
      "format": {
        "type": "json_schema",
        "name": "deployment_risk",
        "strict": true,
        "schema": {
          "type": "object",
          "properties": {
            "risk": { "type": "string", "enum": ["low", "medium", "high"] },
            "reason": { "type": "string" }
          },
          "required": ["risk", "reason"],
          "additionalProperties": false
        }
      }
    }
  }'

Use the Responses API for function calling. OpenAI’s GPT-6 Astra guidance does not support tool calling through Chat Completions.

cURL

curl https://www.anyfast.ai/v1/responses \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-6-astra",
    "input": "Check the deployment status for service api-gateway.",
    "tools": [{
      "type": "function",
      "name": "get_deployment_status",
      "description": "Return the current deployment status for a service.",
      "parameters": {
        "type": "object",
        "properties": {
          "service": { "type": "string" }
        },
        "required": ["service"],
        "additionalProperties": false
      },
      "strict": true
    }],
    "tool_choice": "auto"
  }'

Reasoning configuration

Effort	Use case
`low`	Lower-latency requests and routine tasks
`medium`	General reasoning and coding
`high`	Complex analysis and multi-step work
`xhigh`	Difficult professional and engineering tasks
`max`	Maximum reasoning depth for the hardest workflows

GPT-6 Astra does not support none or minimal. It also does not support temperature, top_p, or top_logprobs. Do not send logprobs with Chat Completions.

API guidance

Use the Responses API for tool calling.
For explicit prompt caching, use prompt_cache_options.ttl rather than the older prompt_cache_retention field.
Use include: ["reasoning.encrypted_content"] with store: false when you need encrypted reasoning items for stateless workflows.
Use max_tool_calls to cap built-in tool calls and parallel_tool_calls to control parallel function calls.
Public image URLs must permit server-side downloads. Data URLs are supported when the remote host blocks automated access.
Image input is supported; audio and video input are not supported.

AnyFast does not currently expose the Responses retrieval, Conversations, or Vector Stores management endpoints. Do not depend on background, conversation, previous_response_id, stored prompt references, or configuration_update for this model. Cross-request item references can also fail when requests are routed to different upstream resources.

Core parameters

Parameter	Type	Required	Description
`model`	string	Yes	Must be `gpt-6-astra`
`input`	string / array	Yes	Text, image, file, or tool-result input
`instructions`	string	No	System-level instructions for this response
`reasoning.effort`	string	No	`low`, `medium`, `high`, `xhigh`, or `max`
`reasoning.summary`	string	No	`auto`, `concise`, or `detailed`
`reasoning.context`	string	No	`auto`, `current_turn`, or `all_turns`
`reasoning.mode`	string	No	Use `standard`; Pro mode is not exposed on the current AnyFast route
`max_output_tokens`	integer	No	Maximum generated tokens, up to 128,000
`max_tool_calls`	integer	No	Maximum total built-in tool calls processed by the response
`text.format`	object	No	Text or Structured Outputs configuration
`text.verbosity`	string	No	`low`, `medium`, or `high`
`tools`	array	No	Function or Responses API tool definitions
`tool_choice`	string / object	No	Controls whether and which tool is called
`parallel_tool_calls`	boolean	No	Allows multiple tool calls in one model turn
`include`	array	No	Requests supported supplementary response data
`prompt_cache_key`	string	No	Improves cache matching for related requests
`prompt_cache_options`	object	No	Configures implicit or explicit prompt caching; `ttl` currently supports `30m`
`prompt_cache_breakpoint`	object	No	Marks an explicit reusable-prefix boundary inside a content block
`stream`	boolean	No	Stream response events over SSE
`stream_options`	object	No	Controls stream-specific behavior such as event obfuscation
`store`	boolean	No	Controls upstream response storage; AnyFast does not expose response retrieval
`metadata`	object	No	Application-defined string key-value pairs
`truncation`	string	No	Use `disabled` on the current AnyFast route

API Reference

View the GPT-6 Astra Responses API reference.

Getting started

Model Introduction

Resources

Model specifications

Key capabilities

Capability examples

Reasoning configuration

API guidance

Core parameters

API Reference

Official references

​Model specifications

​Key capabilities

​Capability examples

​Reasoning configuration

​API guidance

​Core parameters

API Reference

​Official references

Model specifications

Key capabilities

Capability examples

Reasoning configuration

API guidance

Core parameters

Official references