fix: replace deprecated create_react_agent with langchain create_agent

[devin-ai-integration]

Summary

Both LangGraph examples still build their agents with langgraph.prebuilt.create_react_agent, which emits LangGraphDeprecatedSinceV10: create_react_agent has been moved to langchain.agents ... Deprecated in LangGraph V1.0 to be removed in V2.0 on every run. Both examples already depend on langchain = "^1.0.0", so the replacement is available today.

-from langgraph.prebuilt import create_react_agent
+from langchain.agents import create_agent
-agent = create_react_agent(model=llm, tools=[get_weather], prompt=agent_config.instructions)
+agent = create_agent(llm, tools=[get_weather], system_prompt=agent_config.instructions)

• Removes the deprecation warning users see the first time they run poetry run agent / poetry run agent-graph.
• prompt= becomes system_prompt= — the only renamed argument; the returned object is still a compiled graph with the same invoke({"messages": [...]}) / response["messages"] shape, so metric tracking is unchanged.
• No dependency changes: every manifest uses floor/caret constraints and poetry.lock is gitignored, so poetry install already resolves to the latest within-major releases of the AI SDK, the LangChain/LangGraph packages, and the observability SDK.

No screenshots: these examples are console applications with no UI. No staging preview applies — reviewers can run them locally per the steps below.

Implementation details

How to test

With a LaunchDarkly SDK key and an agent-mode AI Config (plus the provider key for the model the config selects):

cd getting_started/langgraph/react_agent && poetry install && poetry run agent
cd getting_started/langgraph/state_graph && poetry install && poetry run agent-graph

Both were run end-to-end against real agent-mode AI Configs before and after the change:

• react_agent: answered the sample weather question using the get_weather tool, metrics tracked with Success: True. The LangGraphDeprecatedSinceV10 warning is gone after the change.
• state_graph: the full two-agent code-review workflow ran, both nodes evaluated their configs, and the final report was produced — output equivalent to main (verified by running the pre-change file against the same configs).

Also ran poetry install in all example directories (the repo's only CI check) and imported every example module with DeprecationWarnings enabled.

Not changed

• getting_started/gemini/generate_content keeps google-genai = "^1.30.0"; latest is 2.x, which is a major jump.
• The launchdarkly-server-sdk-ai = ">=0.20.0" floors are left alone: the constraint already installs the latest 1.x, and the declared minimum still exposes every API these examples use.
• langgraph stays a direct dependency of both examples (state_graph still uses StateGraph/Command; create_agent returns a compiled LangGraph graph).

Known limitations / follow-ups

• launchdarkly-observability's generated GraphQL client imports the deprecated websockets.client / websockets.legacy APIs, so a DeprecationWarning prints on import of every example. That needs an upstream fix in the observability SDK.
• In state_graph, the documentation node's report section renders as [] when the config points at an Anthropic model (the last message's content is an empty block list). This reproduces identically on main, so it is pre-existing and provider-specific — the documented OpenAI/Gemini/Bedrock providers could not be exercised here (no provider credentials available).
• Neither LangGraph example declares langchain-anthropic, so Anthropic-backed configs fail with an install hint; that matches their .env.example/README, which advertise only OpenAI, Google, and AWS. Anthropic support for the plain LangChain example is handled by chore: add ANTHROPIC_API_KEY to langchain example .env.example #40.

Link to Devin session: https://app.devin.ai/sessions/e48229e292c14f86af398aa1b7e9fe66
Open in Devin Desktop: https://app.devin.ai/desktop/session/e48229e292c14f86af398aa1b7e9fe66?variant=devin

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[devin-ai-integration]

@cursor review