# TrustRank (Reputation)

**Last Updated:** 2025-01-31
**Confidence:** Medium (planned feature)

## Summary

TrustRank is a recursive PageRank-style algorithm for agent credibility. Agents who make accurate claims early gain reputation; agents who contradict settled truth lose reputation.

**Key Facts:**
- Stored in `A:{AgentId}` key in KV store
- Background "Gardener" process calculates scores
- Used by `Authority` lens to weight assertions
- Reputation decays for low-confidence agents

**File Pointer:** `crates/stemedb-gardener/src/trustrank.rs` (planned, Phase 4)

## How It Works

### Validation Loop (Gardener)

```
Every N hours:
1. Find "Settled Facts" (>99% consensus over T time)
2. For each settled fact:
   - Reward agents who claimed it early (+R)
   - Punish agents who claimed opposite (-R)
3. Update A:{AgentId} scores
4. Back-propagate: high-R agents boost sources they cite
```

### Usage in Authority Lens

```rust
impl Lens for AuthorityLens {
    fn resolve(&self, candidates: &[Assertion], ctx: &QueryContext) -> LensResult {
        // Weight by agent reputation
        let weighted: Vec<_> = candidates.iter()
            .map(|a| {
                let rep = ctx.get_reputation(&a.agent);
                (a, rep)
            })
            .collect();

        // Return highest weighted assertion
        weighted.into_iter()
            .max_by_key(|(_, rep)| *rep)
            .map(|(a, _)| a.clone())
    }
}
```

## Reputation Score Range

| Score | Meaning |
|-------|---------|
| 0-300 | Unreliable (spam, noise) |
| 300-600 | Neutral (unproven) |
| 600-900 | Reliable (track record) |
| 900-1000 | Authoritative (expert) |

## Related Topics

- [Lens](../services/lens.md)
- [Roadmap Phase 4](../../../roadmap.md)