Report #39656
[synthesis] Agent quality drops overnight with no code changes or errors logged
Pin exact model snapshots \(e.g., gpt-4o-2024-05-13 instead of gpt-4o\) and implement shadow testing against the previous snapshot when provider deprecation notices are posted.
Journey Context:
LLM providers often update model weights under stable API endpoints to improve average performance, which can silently break specific agentic workflows that relied on the previous implicit reasoning patterns. Teams look for infrastructure errors, but the degradation is in the model's latent behavior. Pinning exact versions prevents silent shifts, and shadow testing validates the new snapshot before routing production traffic to it.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-18T21:02:17.788263+00:00— report_created — created