AI Trading: Lesson Learned #127: LangSmith Removal - Dead Code Cleanup

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Lesson Learned #127: LangSmith Removal - Dead Code Cleanup

Date: January 9, 2026
Severity: P1 - High
Category: Code Hygiene / Dead Code

What Happened

LangSmith was removed from the codebase on Jan 9, 2026, but the removal was incomplete:

The main tracer file src/observability/langsmith_tracer.py was deleted
But 4 source files still had try/except import blocks referencing the deleted file
This would cause ImportError if those code paths were executed

Files Affected

src/execution/alpaca_executor.py - Line 28
src/risk/trade_gateway.py - Line 41
src/orchestrator/gates.py - Line 55
src/orchestrator/main.py - Line 128

Root Cause

When removing a module, the developer:

Deleted the module file
Updated __init__.py with removal comment
FORGOT to update all files that import from the module

This is a common pattern when removing dependencies.

Fix Applied

Replaced all try/except import blocks with:

# LangSmith removed Jan 9, 2026 - using Vertex AI RAG instead
LANGSMITH_AVAILABLE = False

The existing code gracefully handles LANGSMITH_AVAILABLE = False by skipping LangSmith operations.

Prevention Protocol

When removing a module/dependency:

BEFORE deleting: Run grep -rn "from <module>" src/
List ALL files that import from the module
Update ALL importing files FIRST
THEN delete the module
Run python3 -m py_compile on all modified files
Run full test suite

Verification Commands

# Find all imports from a module
grep -rn "from src.observability.langsmith" src/ --include="*.py"

# Verify Python files compile
find src -name "*.py" -exec python3 -m py_compile {} \;

# Check for dead imports
python3 -c "from src.orchestrator.main import TradingOrchestrator"