fix(langchain): handle ToolNode in create_react_agent tool iteration

[dvirski]

Fixes #3841 — TypeError: ToolNode object is not iterable when using langgraph-supervisor with create_react_agent
Fixes #3921 — same root cause as #3841, duplicate issue

Summary by CodeRabbit

• Bug Fixes

  • Enhanced agent creation wrapper to more reliably handle tools from LangChain, including improved tool extraction and definition generation.

• Tests

  • Added regression test to verify create_react_agent functionality with ToolNode input and tool definition accuracy.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ff3a8d0a-ff4c-4560-8c90-1dbae548c17a

📥 Commits

Reviewing files that changed from the base of the PR and between abbcc11 and 0ef2899.

📒 Files selected for processing (2)

• packages/opentelemetry-instrumentation-langchain/opentelemetry/instrumentation/langchain/patch.py
• packages/opentelemetry-instrumentation-langchain/tests/test_langgraph.py

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📝 Walkthrough

Walkthrough

The pull request enhances the OpenTelemetry LangChain instrumentation to robustly handle tools wrapped in LangChain's ToolNode by introducing a fallback iteration mechanism that checks for tools_by_name.values() before using tools directly. A regression test validates this functionality.

Changes

Agent Tool Wrapper Enhancement

Layer / File(s)	Summary
Core Implementation packages/opentelemetry-instrumentation-langchain/opentelemetry/instrumentation/langchain/patch.py	Agent creation wrapper modified to extract tools via tools_by_name.values() when available, with fallback to original tools iterable, ensuring GEN_AI_TOOL_DEFINITIONS are correctly populated for ToolNode-wrapped tools.
Test Coverage packages/opentelemetry-instrumentation-langchain/tests/test_langgraph.py	New regression test test_create_react_agent_with_toolnode verifies that create_react_agent accepts ToolNode as tools input and correctly emits both tool definitions.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 A ToolNode hops through LangChain's door,
The wrapper now knows what's inside its core—
tools_by_name unlocks the way,
While tests ensure the tools will stay! 🛠️

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 55.56% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main fix: handling ToolNode in the create_react_agent tool iteration, which aligns directly with the core changes in the patch.py file.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix(langchain)-handle-ToolNode-in-create_react_agent-tool-iteration

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