[jeffdupont]

Fixes AIC-3590. Spec change: launchdarkly/ai-sdks-monorepo#64 (merge that first).

Problem

The handler builds its agent with langgraph.prebuilt.create_react_agent. LangGraph 1.0 deprecated it and 2.0 removes it, so every agent run emits a LangGraphDeprecatedSinceV10 warning, and the handler breaks on LangGraph 2.0.

Change

• Both the blocking and the streaming path call create_agent from langchain.agents. The system prompt is now passed as system_prompt= instead of prompt=. This matches the TypeScript handler, which uses createAgent.
• langchain>=1.0 is now a declared dependency. The lockfile adds only langchain 1.3.14; I pinned that version on purpose so no other locked version moves. The newest langchain (1.4.6) would also have bumped langchain-core, langgraph and langsmith (0.9 → 0.14).
• Tests: the §2.x.0 test now covers both paths. It asserts create_agent is called with system_prompt= and that create_react_agent is never called. The test mocks now use the new import path. test_output_format_appends_schema_instruction used to assert nothing when no call was captured; it now requires a captured call.
• agents.md and the docstrings are updated.

Testing

• Full suite: 2437 passed, 1 skipped (on main: 2436 passed, 1 skipped; the extra one is the new streaming case of §2.x.0). ruff check, ruff format --check and mypy are clean. The deprecation warning no longer appears.
• Side-by-side run: I ran the real main handler and this branch's handler against the same fake tool-calling model, using the real agent graph and real LangChain callbacks, on 7 scenarios: tool loop, streaming tool loop, tool error, streaming tool error, no tools, history, messages-only config. Every compared field was identical: messages the model received, output, usage, stream events, span tree, and tool-error propagation (§1.4). The only difference is that the warning is gone.

The graph nodes are now named model/tools instead of agent/tools. The streaming loop reads the values of each graph step, not the node names, so this doesn't change anything here.

🤖 Generated with Claude Code

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Note

Overview
Replaces LangGraph's deprecated create_react_agent with langchain.agents.create_agent on both blocking and streaming invoke paths, passing instructions via system_prompt= instead of prompt= (aligned with the TypeScript handler).

Adds langchain>=1.0 as a direct dependency and caps langgraph at <2 so the package stays compatible before LangGraph 2.0 removes the old API. Docs, docstrings, and tests are updated—including a parametrized test that create_react_agent is never called and system_prompt is wired correctly on stream and non-stream paths.

^{Reviewed by Cursor Bugbot for commit 92ef5f7. Bugbot is set up for automated code reviews on this repo. Configure here.}

[jeffdupont]

Pushed two commits:

• c6461ca merges origin/main (fix!: pass AI Config model parameters through to every provider handler #107 changed this handler).
• 1afec86 raises the langchain-core and langgraph floors to >=1.0 and re-locks.

Local: lint and typecheck pass; the langchain-agents tests pass. Needs a human reviewer.

🤖 Generated with Claude Code

[XieX]

Approving. One non-blocking note and two nits.

Non-blocking: the new minimum versions don't install together cleanly. In a fresh venv at the floor (langchain==1.0.0), pip picked langchain-core 1.0.7, langgraph 1.0.10 and langgraph-checkpoint 4.3.1. With those, from langchain.agents import create_agent fails:

TypeError: Reviver.__init__() got an unexpected keyword argument 'allowed_objects'

The cause is upstream: langgraph-checkpoint 4.3.1 declares langchain-core>=0.2.38 but uses a newer Reviver API. Fresh installs get the latest versions and work, so only users who hold langchain-core back would hit this. Raising the floors closer to what's tested would avoid it. For example, langchain 1.3.14 itself requires langchain-core>=1.4.9.

Nits:

• _patch_lc in tests/test_handler.py still returns a MagicMock for "langchain" under the comment "Stub out packages that aren't installed in the test environment". langchain is a hard dependency now, so that branch and its comment are stale.
• The §2.x.0 test checks system_prompt= but not the model and tools arguments, which the general §2.x.0 bullet asks for ("assert it was called with the expected arguments (model, tools, system prompt)"). The old test didn't check them either.