feat: Expose Ollama reasoning (thinking) as <think> tags in OpenAI-compat SSE for generic clients

[pvyswiss]

Feature Request

Ollama reasoning models (DeepSeek R1, Gemma 4) send reasoning in message.thinking. Open WebUI converts this to delta.reasoning_content -- a non-standard field that only DeepSeek-specific SDKs understand.

Generic OpenAI-compatible SDKs (@ai-sdk/openai-compatible, etc.) don't recognize reasoning_content and silently drop reasoning tokens.

Related to: #23917 (Bug 4)

Suggested Enhancement

Convert Ollama's thinking field into <think> tags inside the standard content field:

if reasoning_content:
    if not in_reasoning:
        in_reasoning = True
        message_content = "<think>\n" + reasoning_content
    else:
        message_content = reasoning_content
    reasoning_content = None
elif in_reasoning and message_content:
    in_reasoning = False
    message_content = "\n</think>\n\n" + message_content

Open WebUI's browser middleware already detects <think> tags and renders them as collapsible blocks -- fully backward-compatible.

Impact

• Web UI: <think> tags rendered as collapsible reasoning (same as before)
• API clients: Reasoning visible as standard content text

File

backend/open_webui/utils/response.py

[tjbck]

Open to discussion.