"""
Minimal reproduction: streaming drops `namespace` from deferred function_call
content blocks, causing OpenAI 400 "Missing namespace for function_call" on the
next turn's round-trip.

Requirements:
    pip install langchain-openai>=1.1.11 openai>=2.26.0
    export OPENAI_API_KEY=sk-...

Model: gpt-5.4-mini (or any gpt-5.4+ model that supports tool_search)
"""

import asyncio
import json
from langchain_openai import ChatOpenAI
from langchain_core.tools import tool
from langchain_core.messages import HumanMessage, ToolMessage


# ── A tool marked for deferred loading ──────────────────────────────
@tool(extras={"defer_loading": True})
def get_weather(location: str) -> str:
    """Get current weather for a location."""
    return json.dumps({"location": location, "temp": "72°F", "condition": "sunny"})


async def main():
    llm = ChatOpenAI(
        model="gpt-5.4-mini",
        use_responses_api=True,
        streaming=True,
    ).bind_tools([get_weather, {"type": "tool_search"}])

    # ── Turn 1: model discovers & calls the deferred tool ───────────
    messages = [HumanMessage("What's the weather in Paris?")]

    # Stream the response and accumulate
    full = None
    async for chunk in llm.astream(messages):
        full = chunk if full is None else full + chunk

    print("=== Turn 1 AIMessage.content blocks ===")
    if isinstance(full.content, list):
        for i, block in enumerate(full.content):
            if isinstance(block, dict) and block.get("type") == "function_call":
                has_ns = "namespace" in block
                print(f"  [{i}] function_call  name={block.get('name')!r}  "
                      f"namespace={'PRESENT: ' + repr(block.get('namespace')) if has_ns else 'MISSING <<<'}")

    # ── Execute tool & build Turn 2 ─────────────────────────────────
    messages.append(full)
    for tc in full.tool_calls:
        result = get_weather.invoke(tc["args"])
        messages.append(ToolMessage(content=result, tool_call_id=tc["id"]))

    messages.append(HumanMessage("Now what about London?"))

    # ── Turn 2: round-trips the previous function_call → 400 ───────
    try:
        full2 = None
        async for chunk in llm.astream(messages):
            full2 = chunk if full2 is None else full2 + chunk
        print("\n=== Turn 2 succeeded (unexpected) ===")
        print(full2.content[:200] if isinstance(full2.content, str) else full2.content[:3])
    except Exception as e:
        print(f"\n=== Turn 2 FAILED (expected) ===")
        print(f"  {type(e).__name__}: {e}")


asyncio.run(main())

---

openai.BadRequestError: Error code: 400 -
{
  "error": {
    "message": "Missing namespace for function_call 'get_weather'.
               It does not exist in the default namespace.
               Round-trip the model's function_call item with its namespace field included.",
    "type": "invalid_request_error",
    "param": null,
    "code": null
  }
}

---

# response.output_item.added handler for function_call
content.append(
    {
        "type": "function_call",
        "name": chunk.item.name,
        "arguments": chunk.item.arguments,
        "call_id": chunk.item.call_id,
        "id": chunk.item.id,
        "index": current_index,
    }
)

---

content_block = {
    "type": "function_call",
    "name": chunk.item.name,
    "arguments": chunk.item.arguments,
    "call_id": chunk.item.call_id,
    "id": chunk.item.id,
    "index": current_index,
}
if hasattr(chunk.item, "namespace") and chunk.item.namespace is not None:
    content_block["namespace"] = chunk.item.namespace
content.append(content_block)