chore: import upstream snapshot with attribution

contributing/samples/models/interactions_api/README.md

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+# Interactions API Sample Agent
+
+This sample agent demonstrates the Interactions API integration in ADK. The
+Interactions API provides stateful conversation capabilities, allowing chained
+interactions using `previous_interaction_id` instead of sending full
+conversation history.
+
+## Features Tested
+
+1. **Basic Text Generation** - Simple conversation without tools
+1. **Google Search Tool** - Web search using `GoogleSearchTool` with
+   `bypass_multi_tools_limit=True`
+1. **Multi-Turn Conversations** - Stateful interactions with context retention
+   via `previous_interaction_id`
+1. **Custom Function Tool** - Weather lookup using `get_current_weather`
+
+## Important: Tool Compatibility
+
+The Interactions API does **NOT** support mixing custom function calling tools
+with built-in tools (like `google_search`) in the same agent. To work around
+this limitation:
+
+```python
+# Use bypass_multi_tools_limit=True to convert google_search to a function tool
+GoogleSearchTool(bypass_multi_tools_limit=True)
+```
+
+This converts the built-in `google_search` to a function calling tool (via
+`GoogleSearchAgentTool`), which allows it to work alongside custom function
+tools.
+
+## How to Run
+
+### Prerequisites
+
+```bash
+# From the adk-python root directory
+uv sync --all-extras
+source .venv/bin/activate
+
+# Set up authentication (choose one):
+# Option 1: Using Google Cloud credentials
+export GOOGLE_CLOUD_PROJECT=your-project-id
+
+# Option 2: Using API Key
+export GOOGLE_API_KEY=your-api-key
+```
+
+### Running Tests
+
+```bash
+cd contributing/samples
+
+# Run automated tests with Interactions API
+python -m interactions_api.main
+```
+
+## Key Differences: Interactions API vs Standard API
+
+### Interactions API (`use_interactions_api=True`)
+
+- Uses stateful interactions via `previous_interaction_id`
+- Only sends current turn contents when chaining interactions
+- Returns `interaction_id` in responses for chaining
+- Ideal for long conversations with many turns
+- Context caching is not used (state maintained via interaction chaining)
+
+### Standard API (`use_interactions_api=False`)
+
+- Uses stateless `generate_content` calls
+- Sends full conversation history with each request
+- No interaction IDs in responses
+- Context caching can be used
+
+## Code Structure
+
+```
+interactions_api/
+├── __init__.py                    # Package initialization
+├── agent.py                       # Agent definition with Interactions API
+├── main.py                        # Test runner
+├── test_interactions_curl.sh      # cURL-based API tests
+├── test_interactions_direct.py    # Direct API tests
+└── README.md                      # This file
+```
+
+## Agent Configuration
+
+```python
+from google.adk.agents.llm_agent import Agent
+from google.adk.models.google_llm import Gemini
+from google.adk.tools.google_search_tool import GoogleSearchTool
+
+root_agent = Agent(
+    model=Gemini(
+        model="gemini-2.5-flash",
+        use_interactions_api=True,  # Enable Interactions API
+    ),
+    name="interactions_test_agent",
+    tools=[
+        GoogleSearchTool(bypass_multi_tools_limit=True),  # Converted to function tool
+        get_current_weather,  # Custom function tool
+    ],
+)
+```
+
+## Example Output
+
+```
+============================================================
+TEST 1: Basic Text Generation
+============================================================
+
+>> User: Hello! What can you help me with?
+<< Agent: Hello! I can help you with: 1) Search the web...
+   [Interaction ID: v1_abc123...]
+PASSED: Basic text generation works
+
+============================================================
+TEST 2: Function Calling (Google Search Tool)
+============================================================
+
+>> User: Search for the capital of France.
+   [Tool Call] google_search_agent({'request': 'capital of France'})
+   [Tool Result] google_search_agent: {'result': 'The capital of France is Paris...'}
+<< Agent: The capital of France is Paris.
+   [Interaction ID: v1_def456...]
+PASSED: Google search tool works
+
+============================================================
+TEST 3: Multi-Turn Conversation (Stateful)
+============================================================
+
+>> User: Remember the number 42.
+<< Agent: I'll remember that number - 42.
+   [Interaction ID: v1_ghi789...]
+
+>> User: What number did I ask you to remember?
+<< Agent: You asked me to remember the number 42.
+   [Interaction ID: v1_jkl012...]
+PASSED: Multi-turn conversation works with context retention
+
+============================================================
+TEST 5: Custom Function Tool (get_current_weather)
+============================================================
+
+>> User: What's the weather like in Tokyo?
+   [Tool Call] get_current_weather({'city': 'Tokyo'})
+   [Tool Result] get_current_weather: {'city': 'Tokyo', 'temperature_f': 68, ...}
+<< Agent: The weather in Tokyo is 68F and Partly Cloudy.
+   [Interaction ID: v1_mno345...]
+PASSED: Custom function tool works with bypass_multi_tools_limit
+
+ALL TESTS PASSED (Interactions API)
+```