System One decisions API

Send a state and a set of typed questions to POST /inference/v1/systemone and get a calibrated probability distribution for every question in one pass.

The System One decisions API takes a state (any text or JSON describing the current situation) and a set of typed questions, and returns a calibrated probability distribution for every question. The model reads the state once and answers every question from that single pass, so adding questions to a request is much cheaper than making separate calls.

The same API is also available in an OpenAI-compatible shape at POST /inference/v1/decisions.

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Endpoint

POST https://api.fireworks.ai/inference/v1/systemone

Authenticate with your normal Fireworks API key. Set model to the System One model path. The public Serverless model is accounts/fireworks/models/rune, which serves this API and the Decisions API only; chat completions and completions against it return a 400. Other models that don’t support this API also return a 400.

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Quickstart

cURL

curl https://api.fireworks.ai/inference/v1/systemone \
  -H "Authorization: Bearer $FIREWORKS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "accounts/<your-account>/models/<your-model>",
  "state": {
    "user_request": "Add retry with exponential backoff to the payments webhook handler, and don'\''t retry on 4xx.",
    "last_command": "npm test -- webhooks",
    "test_output": "PASS handler.test.ts (4 tests)\nFAIL retry.test.ts\n  x does not retry on 4xx responses\n    Expected forwardEvent to be called 1 time, received 5"
  },
  "questions": {
    "task_complete": {
      "type": "noul",
      "instructions": "Is the user'\''s request fully done?"
    },
    "next_action": {
      "type": "choice",
      "instructions": "What should the agent do next?",
      "criteria": {
        "edit_code": "Change the code to fix the failing behavior",
        "rerun_tests": "Run the tests again without changing anything",
        "ask_user": "Stop and ask the user a clarifying question",
        "finish": "Report the task as done"
      }
    },
    "risk": {
      "type": "score",
      "instructions": "How risky would it be to ship the current change as is?",
      "criteria": ["safe", "minor risk", "moderate risk", "high risk", "would cause an incident"]
    }
  }
}'

​

Request

Field	Type	Description
model	string	Required. The System One model path, for example accounts/<your-account>/models/<your-model>.
state	string or object	Required. The situation to decide about. Strings are used as-is; objects are serialized as JSON.
questions	object	Required. Map of your question ID to a question. Up to 256 questions per request.

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Question types

type	criteria	Answer
noul	Optional object {"true": "...", "false": "..."} describing each side. Defaults to yes/no.	Probability that the statement is true.
choice	Required. Object mapping each option key to a description. Up to 208 options.	The most likely option, a probability per option, and a confidence.
score	Required. Ordered array of 2 to 10 level descriptions, lowest first.	The expected score (0 = first level), a probability per level, and a confidence.

Every question takes an instructions string: the question itself, in plain language.

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Response

{
  "model": "accounts/<your-account>/models/<your-model>",
  "answers": {
    "refund": { "type": "noul", "noul": 0.98 },
    "tone": {
      "type": "choice",
      "choice": "angry",
      "probabilities": { "angry": 0.91, "neutral": 0.08, "positive": 0.01 },
      "confidence": 0.87
    },
    "urgency": {
      "type": "score",
      "score": 1.7,
      "legend": { "0": "not urgent", "1": "somewhat urgent", "2": "urgent", "3": "critical" },
      "probabilities": { "0": 0.05, "1": 0.3, "2": 0.55, "3": 0.1 },
      "confidence": 0.4
    }
  },
  "usage": { "input_tokens": 212, "cached_input_tokens": 0, "output_tokens": 0 }
}

Values above are illustrative.

Field	Description
noul	Probability, from 0 to 1, that the statement is true.
choice	The key of the most likely option.
score	Expected level, from 0 to the number of levels minus 1, weighted by probability.
probabilities	Probability of each option key (choice) or level index (score). Sums to 1.
confidence	How concentrated the distribution is: 0 when every option is equally likely, 1 when one option has all the probability.
legend	For score, maps each level index back to its description.
usage	Token usage for the request. cached_input_tokens counts state tokens served from the prompt cache.

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Pricing and capacity

Billing, capacity, and rate limits depend on how the model is deployed.

• Serverless. Rune is billed per input token on Serverless pricing. Output tokens are always zero. Capacity and rate limits work the same as for other Serverless models; see Serverless rate limits.
• Dedicated deployment. Usage is billed at the deployment’s standard on-demand GPU rate, and capacity scales with the deployment’s size and autoscaling settings.

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Latency and caching

• Batch your questions. All questions in a request share one read of the state, so asking ten questions in one request is much faster and cheaper than ten requests.
• Reuse the state. The state is cached across requests and the questions are not. Calls that send the same large state (for example a long transcript) with different questions benefit most from caching.
• Measure server time. The fireworks-server-processing-time response header reports time spent on Fireworks servers. Anything above that is network.

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Limits

Limit	Value
Questions per request	256
Options per choice question	208
Levels per score question	2 to 10
Context window	256K tokens
Question text	16K tokens
State size	4 MiB
Request body	8 MiB
Request duration	5 minutes

Current support:

• Text only. Requests with images return a 400.
• No reasoning. reasoning_effort other than "none" returns a 400.
• Decisions only. The model serves /inference/v1/systemone and /inference/v1/decisions only. Chat completions and completions against it return a 400.

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Errors

Errors use the standard Fireworks error body.

Status	Meaning
400	Over a limit, an unsupported field, or a model that doesn’t support this API.
413	Request body over 8 MiB.
422	Malformed JSON, a missing required field, or an invalid question (unknown type or malformed criteria).
429	Rate limited. Retry after the Retry-After header.
503	Temporarily at capacity. Retry after the Retry-After header.
504	The request took longer than 5 minutes.
502	Upstream failure. Safe to retry.