LangChain Common Errors (Python) Overview The same twelve-plus LangChain 1.0 / LangGraph 1.0 tracebacks show up every week in production: , , , , deep in LCEL internals. Stack traces are ambiguous, docs sprawl across 0.2 / 0.3 / 1.0 eras, and engineers lose 30–90 minutes per incident re-deriving the fix. This skill is a paste-match catalog of 14 entries (E01–E14) grouped into 3 reference files by category, plus a triage decision tree. Every entry opens with the exact exception class and message string you see in your terminal, names the cause in one sentence with a pain-catalog code, and give…