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Reasoning Models

This page only documents reasoning behavior that was revalidated against Crazyrouter production on 2026-03-22. For OpenAI-compatible integrations, the current guidance is:
  • If you only want stronger reasoning and only need the final answer, use Chat Completions with reasoning_effort
  • If you need a stable, inspectable reasoning output, prefer the Responses API and see GPT-5 Thinking Mode

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Verified combinations

RouteModelRequest parameterCurrent production behavior
Chat Completionsgpt-5.4reasoning_effortRequest succeeds and returns a final answer
Responsesgpt-5.4reasoning.effort / reasoning.summaryoutput includes reasoning and message items

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Chat Completions: reasoning_effort

The following request shape currently works in production:
cURL
curl https://crazyrouter.com/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "gpt-5.4",
    "messages": [
      {
        "role": "user",
        "content": "Which is larger, 9.11 or 9.9? Explain briefly."
      }
    ],
    "reasoning_effort": "high",
    "max_tokens": 120
  }'
Available reasoning_effort values:
ValueMeaning
lowFaster response for simpler tasks
mediumBalanced default-style setting
highMore reasoning for harder tasks

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Current response behavior

In the 2026-03-22 production recheck:
  • the request succeeded
  • the final answer was returned in message.content
  • message.reasoning_content did not reliably contain usable content
So if you only want stronger reasoning, Chat Completions with reasoning_effort is still usable. If you need a visible reasoning summary field, do not treat Chat Completions as the primary path.

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When you need inspectable reasoning output

The more reliable production path is the Responses API:
cURL
curl https://crazyrouter.com/v1/responses \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "gpt-5.4",
    "input": "Which is larger, 9.11 or 9.9? Explain briefly.",
    "reasoning": {
      "effort": "high",
      "summary": "detailed"
    }
  }'
Verified output.type values: 
["reasoning", "message"]
For concrete response shapes, summary fields, and streaming event names, see:

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Current recommendation

  • For new builds that need to log or display reasoning summaries, start with the Responses API
  • For existing Chat Completions integrations that only care about the final answer, reasoning_effort is still a valid path
  • Do not assume all OpenAI-compatible reasoning models will reliably expose reasoning_content
Reasoning requests usually increase both latency and token usage. Higher reasoning_effort generally costs more.