Why it matters

Replay shapes regression detection. Understanding shapes practice.

Advertisement

The architecture

Record: prompts + LLM responses + tool results.

Replay: mock LLM + tools with recorded.

Compare new to recorded.

Agent replay flowRecordprompts + responsesMock LLM + toolsreturn recordedCompareold vs new agentLangSmith + Langfuse support replay + eval; VCR-style HTTP recording
Agent replay.
Advertisement

How it works end to end

Cassette-based recording (VCR).

Deterministic replay for tests.

Diff outputs.

Version comparison.