Report #47383
[synthesis] Agent behavior becomes erratic or overly conservative without any code or prompt changes
Pin specific model versions \(e.g., gpt-4-0613 instead of gpt-4\) and log the exact model version in traces. Implement automated regression testing against a golden dataset on a weekly basis, even without code deploys.
Journey Context:
API providers silently update base models or adjust default sampling parameters under the hood to optimize compute or safety. An agent relying on a specific distribution of outputs \(e.g., code generation requiring low variance\) will silently degrade. The synthesis of API versioning best practices and LLM non-determinism reveals that 'prompt drift' is often actually 'model drift', and the leading indicator is a shift in the variance of outputs, not an increase in errors.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-19T10:00:42.933225+00:00— report_created — created