I Wrote a Playwright Script to Test LLM Long-Term Memory — and Found 3 Critical Bugs

Short summary

A developer shares how they built automated Playwright tests in Python to validate LLM long-term memory in a LangChain-powered customer support assistant, uncovering three framework-level bugs including cross-session memory leakage. The post explains why browser-based end-to-end testing is essential for verifying memory flows that unit tests cannot capture, and provides concrete pytest fixtures and test code for simulating multi-session memory persistence.

• •Browser-based E2E testing with Playwright is necessary to validate full LLM memory chains including frontend session management
• •Three critical bugs were found: memory leakage across sessions, unreliable summarization, and concurrent session state corruption
• •Includes working pytest + Playwright Python code for testing cross-session memory persistence in LangChain-based assistants

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