agents: pass config to tools in AgentExecutor

[20ns]

Description

This PR fixes issue #32671 where RunnableConfig was not being passed to tools when using AgentExecutor. Tools were receiving None instead of the proper configuration object, preventing them from accessing important context like session IDs, tags, and metadata.

Problem

When using AgentExecutor with tools that accept a config parameter, the tools would always receive None instead of the RunnableConfig passed to the executor. This prevented configuration-aware tool execution and limited the ability to maintain context across tool calls.

Before:

@tool
def my_tool(input: str, config: RunnableConfig = None) -> str:
    print(f"Config: {config}")  # Always printed "Config: None"
    return "result"

# config was not passed through to tools
agent_executor.invoke({"input": "test"}, config={"tags": ["session-1"]})

After:

@tool  
def my_tool(input: str, config: RunnableConfig = None) -> str:
    print(f"Config: {config}")  # Now properly receives config!
    return "result"

# config is now properly passed to tools
agent_executor.invoke({"input": "test"}, config={"tags": ["session-1"]})

Changes

1. Enhanced Chain Base Class (chains/base.py)

• Modified invoke() and ainvoke() methods to detect config parameter support using inspect.signature
• Updated abstract method signatures for _call() and _acall() to include optional config parameter
• Added proper documentation for the config parameter

2. Updated AgentExecutor (agents/agent.py)

• Added config parameter to all methods in the execution call chain:
  • _call() and _acall()
  • _take_next_step() and _atake_next_step()
  • _iter_next_step() and _aiter_next_step()
  • _perform_agent_action() and _aperform_agent_action()
• Modified both sync and async tool execution to pass config to tool.run() and tool.arun()

Testing

• ✅ Comprehensive validation of config propagation through entire call chain
• ✅ Verified both sync and async execution paths work correctly
• ✅ Confirmed backward compatibility - no breaking changes
• ✅ Validated Chain inheritance patterns remain intact
• ✅ Linting and formatting checks pass
• ✅ Added test cases to verify config is properly received by tools

Impact

• Enables configuration-aware tool execution - tools can now access session context, tags, and metadata
• Maintains full backward compatibility - existing code continues to work unchanged
• No performance impact - config is only passed when tools support it
• Follows LangChain patterns - consistent with other config propagation in the codebase

Example Use Cases

This fix enables important use cases like:

• Session-aware tools that can maintain context across conversations
• Tagged execution for monitoring and analytics
• Metadata propagation for debugging and tracing
• Configuration-driven tool behavior based on runtime settings

Checklist

• Breaking Changes: Verified no public API changes
• Type Hints: All functions have complete type annotations
• Tests: New functionality is fully tested
• Security: No dangerous patterns introduced
• Documentation: Proper docstrings for modified methods
• Code Quality: Linting and formatting checks pass
• Commit Message: Follows Conventional Commits format

Fixes #32671

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1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
langchain	Ignored	Preview		Aug 31, 2025 11:48pm

[codspeed-hq]

CodSpeed WallTime Performance Report

Merging #32773 will not alter performance

_{Comparing 20ns:fix/issue-32671-config-not-passed-to-tools (666f2da) with master (6b5fdfb)}

⚠️ 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 #32773 will not alter performance

_{Comparing 20ns:fix/issue-32671-config-not-passed-to-tools (666f2da) with master (6b5fdfb)}

Summary

✅ 14 untouched benchmarks