feat(models): add langchain-ollama for native Ollama thinking support (#2062)

Add langchain-ollama as an optional dependency and provide ChatOllama
config examples, enabling proper thinking/reasoning content preservation
for local Ollama models.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/packages/harness/pyproject.toml

@@ -36,6 +36,7 @@ dependencies = [
 ]
 
 [project.optional-dependencies]
+ollama = ["langchain-ollama>=0.3.0"]
 pymupdf = ["pymupdf4llm>=0.0.17"]
 
 [build-system]

config.example.yaml

@@ -79,6 +79,41 @@ models:
   #   output_version: responses/v1
   #   supports_vision: true
 
+  # Example: Ollama (native provider — preserves thinking/reasoning content)
+  #
+  # IMPORTANT: Use langchain_ollama:ChatOllama instead of langchain_openai:ChatOpenAI
+  # for Ollama models. The OpenAI-compatible endpoint (/v1/chat/completions) does NOT
+  # return reasoning_content as a separate field — thinking content is either flattened
+  # into <think> tags or dropped entirely (ollama/ollama#15293). The native Ollama API
+  # (/api/chat) correctly separates thinking from response content.
+  #
+  # Install: cd backend && uv pip install 'deerflow-harness[ollama]'
+  #
+  # - name: qwen3-local
+  #   display_name: Qwen3 32B (Ollama)
+  #   use: langchain_ollama:ChatOllama
+  #   model: qwen3:32b
+  #   base_url: http://localhost:11434   # No /v1 suffix — uses native /api/chat
+  #   num_predict: 8192
+  #   temperature: 0.7
+  #   reasoning: true                    # Passes think:true to Ollama native API
+  #   supports_thinking: true
+  #   supports_vision: false
+  #
+  # - name: gemma4-local
+  #   display_name: Gemma 4 27B (Ollama)
+  #   use: langchain_ollama:ChatOllama
+  #   model: gemma4:27b
+  #   base_url: http://localhost:11434
+  #   num_predict: 8192
+  #   temperature: 0.7
+  #   reasoning: true
+  #   supports_thinking: true
+  #   supports_vision: true
+  #
+  # For Docker deployments, use host.docker.internal instead of localhost:
+  #   base_url: http://host.docker.internal:11434
+
   # Example: Anthropic Claude model
   # - name: claude-3-5-sonnet
   #   display_name: Claude 3.5 Sonnet