Drew Breunig's QCon Talk Breaks Down Prompt Debt and Four Context Failures With Concrete Fixes
dbreunig · x · 2026-11-06
At QCon San Francisco, Drew Breunig (CEO of CMPND, editor of O'Reilly's Context Management Handbook) presents "Avoiding Prompt Debt & Other Context Failures".
Key points:
- Prompts accrete "prompt debt": edge cases get patched with one-line hotfixes and stacked instructions, producing a brittle artifact overfit to an aging model.
- It worsens when agents manage their own contexts — tool calls and user input pile up history, and million-token windows aren't a panacea since quality degrades long before the window fills.
Using a deliberately simple repo-bug-fixing agent, he demonstrates four predictable failures — context distraction, confusion, clash, and poisoning — each paired with a concrete fix: compacting history, selecting only needed tools, and offloading context to a code environment the agent can explore on demand, with analysis of costs and trade-offs.
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