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Thinking-capable models emit a thinking field that separates their reasoning trace from the final answer. Use this capability to audit model steps, animate the model thinking in a UI, or hide the trace entirely when you only need the final response.

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Supported models

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Enable thinking in API calls

Set the think field on chat or generate requests. Most models accept booleans (true/false). GPT-OSS instead expects one of low, medium, or high to tune the trace length. The message.thinking (chat endpoint) or thinking (generate endpoint) field contains the reasoning trace while message.content / response holds the final answer.
  • cURL
  • Python
  • JavaScript
curl http://localhost:11434/api/chat -d '{
  "model": "qwen3",
  "messages": [{
    "role": "user",
    "content": "How many letter r are in strawberry?"
  }],
  "think": true,
  "stream": false
}'
GPT-OSS requires think to be set to "low", "medium", or "high". Passing true/false is ignored for that model.

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Stream the reasoning trace

Thinking streams interleave reasoning tokens before answer tokens. Detect the first thinking chunk to render a “thinking” section, then switch to the final reply once message.content arrives.
  • Python
  • JavaScript
from ollama import chat

stream = chat(
  model='qwen3',
  messages=[{'role': 'user', 'content': 'What is 17 × 23?'}],
  think=True,
  stream=True,
)

in_thinking = False

for chunk in stream:
  if chunk.message.thinking and not in_thinking:
    in_thinking = True
    print('Thinking:\n', end='')

  if chunk.message.thinking:
    print(chunk.message.thinking, end='')
  elif chunk.message.content:
    if in_thinking:
      print('\n\nAnswer:\n', end='')
      in_thinking = False
    print(chunk.message.content, end='')

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CLI quick reference

  • Enable thinking for a single run: ollama run deepseek-r1 --think "Where should I visit in Lisbon?"
  • Disable thinking: ollama run deepseek-r1 --think=false "Summarize this article"
  • Hide the trace while still using a thinking model: ollama run deepseek-r1 --hidethinking "Is 9.9 bigger or 9.11?"
  • Inside interactive sessions, toggle with /set think or /set nothink.
  • GPT-OSS only accepts levels: ollama run gpt-oss --think=low "Draft a headline" (replace low with medium or high as needed).
Thinking is enabled by default in the CLI and API for supported models.
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