feat(truth): add background truth scoring worker (#36)

src/db.rs

@@ -640,6 +640,52 @@ impl Database {
             coverage_pct,
         })
     }
+
+    /// Find memories related to the given embedding vector, excluding the source memory.
+    /// Used by the truth scoring worker for cross-referencing.
+    pub async fn find_related_memories(
+        &self,
+        candidate_embedding: &[f32],
+        exclude_id: Uuid,
+        limit: i64,
+    ) -> Result<Vec<RelatedMemoryRow>> {
+        let vector = pgvector::Vector::from(candidate_embedding.to_vec());
+        let client = self.pool.get().await?;
+        let rows = client
+            .query(
+                r#"
+                SELECT id, content, truth_value, truth_confidence,
+                       1 - (embedding <=> $1) AS similarity
+                FROM memories
+                WHERE id != $2
+                  AND (expires_at IS NULL OR expires_at > NOW())
+                ORDER BY embedding <=> $1
+                LIMIT $3
+                "#,
+                &[&vector, &exclude_id, &limit],
+            )
+            .await
+            .context("Failed to find related memories")?;
+
+        Ok(rows
+            .iter()
+            .map(|row| RelatedMemoryRow {
+                similarity: row.get("similarity"),
+                content: row.get("content"),
+                truth_value: row.get("truth_value"),
+                truth_confidence: row.get("truth_confidence"),
+            })
+            .collect())
+    }
+}
+
+/// A row returned from the related memories query.
+#[derive(Debug, Clone)]
+pub struct RelatedMemoryRow {
+    pub similarity: f64,
+    pub content: String,
+    pub truth_value: Option<f32>,
+    pub truth_confidence: Option<f32>,
 }
 
 /// Result for a single batch entry

src/lib.rs

@@ -143,6 +143,71 @@ pub async fn run_server(config: Config, db: Database) -> Result<()> {
         });
     }
 
+    // Spawn truth scoring background worker if enabled
+    if config.truth.enabled {
+        let truth_state = state.clone();
+        let truth_config = config.truth.clone();
+        let scoring_interval = config.truth.scoring_interval_seconds;
+        info!(
+            "Truth scoring enabled (interval={}s, batch={})",
+            scoring_interval, truth_config.batch_size
+        );
+        tokio::spawn(async move {
+            let mut interval = tokio::time::interval(
+                tokio::time::Duration::from_secs(scoring_interval),
+            );
+            interval.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Skip);
+
+            // Wait for the embedding engine to be ready before starting
+            loop {
+                let readiness = truth_state.readiness.read().await;
+                match &*readiness {
+                    ReadinessState::Ready => break,
+                    ReadinessState::Failed(_) => {
+                        error!("Embedding engine failed — truth scoring worker exiting");
+                        return;
+                    }
+                    _ => {
+                        drop(readiness);
+                        tokio::time::sleep(tokio::time::Duration::from_secs(2)).await;
+                    }
+                }
+            }
+            info!("Truth scoring worker started");
+
+            loop {
+                interval.tick().await;
+                // Acquire embedding reference for this cycle
+                let embedding_guard = truth_state.embedding.read().await;
+                let embedding = match &*embedding_guard {
+                    Some(e) => e.clone(),
+                    None => {
+                        warn!("Embedding engine not available — skipping truth scoring cycle");
+                        continue;
+                    }
+                };
+                drop(embedding_guard);
+
+                match truth::worker::run_scoring_cycle(
+                    &truth_state.db,
+                    &embedding,
+                    &truth_config,
+                )
+                .await
+                {
+                    Ok(scored) if scored > 0 => {
+                        info!("Truth scoring cycle complete: {} memories scored", scored);
+                    }
+                    Ok(_) => {}
+                    Err(err) => {
+                        error!("Truth scoring cycle failed: {:?}", err);
+                    }
+                }
+            }
+        });
+    }
+
+
     // Create MCP state for SSE transport
     let mcp_state = McpState::new(state.clone());
 

src/truth/mod.rs

@@ -10,7 +10,10 @@
 //!   truth values from evidence chains.
 //! - **ECAN** (Economic Attention Network): Manages short-term and long-term
 //!   importance of memories, enabling natural prioritization of verified knowledge.
+//! - **Scorer**: Orchestrates PLN and ECAN into a unified scoring pipeline.
+//! - **Worker**: Background daemon that periodically scores unscored and stale memories.
 
 pub mod ecan;
 pub mod pln;
 pub mod scorer;
+pub mod worker;

src/truth/worker.rs

@@ -0,0 +1,112 @@
+//! Background truth scoring worker.
+//!
+//! Periodically fetches unscored and stale memories, runs them through
+//! the scoring pipeline (PLN + ECAN + cross-referencing), and writes
+//! truth scores back to the database.
+
+use std::sync::Arc;
+
+use anyhow::Result;
+use tracing::{debug, error, info, warn};
+
+use crate::config::TruthConfig;
+use crate::db::{Database, TruthScoreUpdate};
+use crate::embedding::EmbeddingEngine;
+use crate::truth::ecan::EcanParams;
+use crate::truth::scorer::{RelatedMemory, ScorerConfig, score_memory};
+
+/// Run a single scoring cycle: fetch candidates, score them, write results.
+///
+/// Returns the number of memories scored in this cycle.
+pub async fn run_scoring_cycle(
+    db: &Database,
+    _embedding: &Arc<EmbeddingEngine>,
+    config: &TruthConfig,
+) -> Result<usize> {
+    let scorer_config = ScorerConfig {
+        pln_base_confidence: config.pln_base_confidence,
+        contradiction_threshold: config.contradiction_threshold,
+        verification_threshold: config.verification_threshold,
+        ecan: EcanParams::new(config.ecan_decay_rate, config.ecan_spread_factor),
+    };
+
+    let batch_size = config.batch_size as i64;
+    let rescore_after = config.rescore_after_seconds as i64;
+    let cross_ref_limit = config.cross_ref_limit as i64;
+
+    // Fetch candidates: unscored first, then stale
+    let mut candidates = db.get_unscored_memories(batch_size).await?;
+    let unscored_count = candidates.len();
+
+    if candidates.len() < batch_size as usize {
+        let remaining = batch_size - candidates.len() as i64;
+        let stale = db.get_stale_memories(rescore_after, remaining).await?;
+        candidates.extend(stale);
+    }
+
+    if candidates.is_empty() {
+        debug!("No memories to score this cycle");
+        return Ok(0);
+    }
+
+    info!(
+        "Scoring {} memories ({} unscored, {} stale)",
+        candidates.len(),
+        unscored_count,
+        candidates.len() - unscored_count
+    );
+
+    let mut updates: Vec<TruthScoreUpdate> = Vec::with_capacity(candidates.len());
+
+    for candidate in &candidates {
+        // Cross-reference: find related memories using vector similarity
+        let related_rows = match db
+            .find_related_memories(&candidate.embedding, candidate.id, cross_ref_limit)
+            .await
+        {
+            Ok(r) => r,
+            Err(err) => {
+                warn!(
+                    "Failed to cross-reference memory {}: {:?}",
+                    candidate.id, err
+                );
+                Vec::new()
+            }
+        };
+
+        // Convert DB rows to scorer's RelatedMemory type
+        let related: Vec<RelatedMemory> = related_rows
+            .into_iter()
+            .map(|row| RelatedMemory {
+                similarity: row.similarity,
+                content: row.content,
+                truth_value: row.truth_value,
+                truth_confidence: row.truth_confidence,
+            })
+            .collect();
+
+        // Score the memory
+        let result = score_memory(
+            &scorer_config,
+            &candidate.content,
+            &related,
+            candidate.ecan_sti,
+            candidate.ecan_lti,
+        );
+
+        updates.push(TruthScoreUpdate {
+            id: candidate.id,
+            truth_value: result.truth_value,
+            truth_confidence: result.truth_confidence,
+            truth_category: result.category.to_string(),
+            ecan_sti: result.ecan_sti,
+            ecan_lti: result.ecan_lti,
+        });
+    }
+
+    // Batch write scores
+    let count = db.batch_update_truth_scores(&updates).await?;
+    info!("Updated truth scores for {} memories", count);
+
+    Ok(count)
+}