Is Your AI System Ready for the Next Model Deprecation?

The Deprecation Problem Nobody Plans For Model upgrades are inevitable in production AI systems — whether forced by provider deprecation cycles or driven by the promise of a better, cheaper model. When Anthropic announced the deprecation of Claude Sonnet 4 earlier this year, the team at Thomson Reuters Labs faced a challenge familiar to anyone running LLM-powered agents in production: how do you migrate a complex, carefully tuned prompt to a new model without breaking the behaviour you spent months perfecting? The naive answer is manual re-prompting: try out the new model, tweak the prompt, ru