wip: existing create_react_agent with only v1 support

[sydney-runkle]

Using langchain-openai==0.4.0.dev0 langchain-core==0.4.0.dev0

from libs.langchain_v1.langchain.agents.base_v1 import create_react_agent
from langchain_openai.v1 import ChatOpenAI

def get_weather(city: str) -> str:
    """Get weather for a given city."""
    return f"It's always sunny in {city}!"

agent = create_react_agent(
    model=ChatOpenAI(model="gpt-4o-mini"),
    tools=[get_weather],
    prompt="You are a helpful assistant",
)

# Run the agent
result = agent.invoke(
    {"messages": [{'role': 'user', 'content': 'what is the weather in sf?'}]}
)
print(result)

Noticeable change:

• v1 doesn't have support for RemoveMessage so I've removed that logic from the reducer. We should figure out the right pattern here.

This is working ok in studio.

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1 Skipped Deployment

Name	Status	Preview	Comments	Updated (UTC)
langchain	⬜️ Ignored (Inspect)			Aug 8, 2025 1:07pm

[codspeed-hq]

CodSpeed WallTime Performance Report

Merging #32464 will not alter performance

_{Comparing sr/v1-mvp (b98158f) with master (0200121)}

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

Summary

✅ 13 untouched benchmarks

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #32464 will not alter performance

_{Comparing sr/v1-mvp (b98158f) with master (0200121)}

Summary

✅ 14 untouched benchmarks

[sydney-runkle]

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