LangChain Local Dev Loop (Python)

Overview

An engineer writes the most natural assertion possible:

def test_summarize():
    out = chain.invoke({"text": "..."})
    assert out.content == "expected summary"

It passes locally against Claude at temperature=0. It fails in CI on the third run with a one-token delta in the output. That is P05: Anthropic's temperature=0 is not greedy — it still samples. Tests against live Claude are not deterministic, period.