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vendor/ruvector/docs/adr/coherence-engine/ADR-CE-020-confidence-from-energy.md

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+# ADR-CE-020: Confidence from Energy
+
+**Status**: Accepted
+**Date**: 2026-01-22
+**Parent**: ADR-014 Coherence Engine Architecture
+
+## Context
+
+RuvLLM's `ConfidenceChecker` produces confidence scores, but:
+- Scores are heuristic-based
+- "Confidence" is often miscalibrated
+- No mathematical grounding
+
+Coherence energy provides a principled alternative.
+
+## Decision
+
+**Confidence scores derived from coherence energy with sigmoid mapping.**
+
+Mapping:
+```rust
+fn confidence_from_energy(energy: f32, scale: f32, threshold: f32) -> f32 {
+    // Low energy → high confidence
+    // High energy → low confidence
+    let scaled = scale * (energy - threshold);
+    1.0 / (1.0 + scaled.exp())
+}
+```
+
+Properties:
+- Energy = 0 → Confidence ≈ 1.0 (perfectly coherent)
+- Energy = threshold → Confidence = 0.5 (uncertain)
+- Energy >> threshold → Confidence → 0 (incoherent)
+
+## Consequences
+
+### Benefits
+- Confidence has mathematical grounding
+- "I don't know" is provable (high energy)
+- Calibration through energy scale tuning
+
+### Risks
+- Sigmoid parameters need tuning
+- Different domains may need different mappings
+
+## References
+
+- ADR-014: Coherence Engine Architecture, "RuvLLM Integration"
+- ADR-CE-013: Not Prediction