ANTHROPIC_API_KEY=sk-ant-...
LANGCHAIN_HARNESS_MODEL=claude-opus-4-7
LANGCHAIN_HARNESS_THINKING_BUDGET=8000
LANGCHAIN_HARNESS_WORKSPACE=_workspace

# Optional: LangSmith tracing
# LANGSMITH_API_KEY=
# LANGSMITH_TRACING=true
# LANGSMITH_PROJECT=langchain-harness