# Pre-Generative Loop Gate > Before each model call fires, detect known divergence signatures (narration loops, repetitive retries, frustration spirals) and inject a steering hint into the prompt — rather than vetoing the call. - **Category**: Agentic AI - **Subcategory**: Cognition & Introspection - **Canonical URL**: https://designpattern.fyi/patterns/pre_generative_loop_gate/ --- ## Description **Intent**: Certain agent failure modes are visible in telemetry before tokens are produced. Catching them post-generation wastes budget. Catching them pre-generation steers without removing the model's authority. **Context**: Specific failure modes recur often enough to be recognizable from signals already available before the call: narrating about acting instead of invoking the tool, retrying the same broken path repeatedly, sinking into rumination on a high-intensity preoccupation. These signatures live in recent thoughts, recent tool calls, the affect snapshot, and the preoccupation list — all available before the next model call fires. **Solution**: A pre-tick function takes recent thoughts, recent tool calls, the affect snapshot, and the preoccupation list, and returns either None or a short steering string: [steering] divergence pattern detected; consider . The hint is appended to the prompt as a system line and the call proceeds. The decision (hint or no hint, which pattern) is logged for post-hoc correlation with subsequent behavior. Vetoing remains the job of explicit safety patterns — this only steers. ## Use Cases - Specific divergence signatures are detectable from telemetry before the model call fires. - Post-hoc detectors catch the failure too late to avoid the token cost. - The model is responsive to short steering hints in the system context. ## Trade-offs ### Advantages - Divergence is named before tokens are produced — intervening cheap rather than post-hoc - Steering as a hint lets the model retain authority; false positives are recoverable - Hint-presence in logs creates an evaluation substrate for calibrating the detector itself ### Considerations & Drawbacks - Pattern signatures are heuristic and will misfire — per-deployment calibration required - Steering hints add tokens to every flagged tick - Silent injection complicates debugging when the model adapts its behavior to it --- **Reference**: [Original Source](https://www.agentpatternscatalog.org/patterns/pre-generative-loop-gate/)