query: generalized composite sort for tunable agent priorities

Add sort:field*weight+field*weight+... syntax for weighted multi-field
sorting. Each field computes a 0-1 score, multiplied by weight, summed.

Available score fields:
  isolation   — community isolation ratio (1.0 = fully isolated)
  degree      — graph degree (normalized to max)
  weight      — node weight
  content-len — content size (normalized to max)
  priority    — consolidation priority score
  recency(X)  — time since agent X last visited (sigmoid decay)

Example: sort:isolation*0.7+recency(linker)*0.3
  Linker agents prioritize isolated communities that haven't been
  visited recently.

Scores are pre-computed per sort (CompositeCache) to avoid redundant
graph traversals inside the sort comparator.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

poc-memory/src/query/engine.rs

@@ -168,6 +168,20 @@ pub enum SortField {
     Degree,
     Weight,
     Isolation,
+    Composite(Vec<(ScoreField, f64)>),
+}
+
+/// Individual scoring dimensions for composite sorts.
+/// Each computes a 0.0-1.0 score per node.
+#[derive(Clone, Debug)]
+pub enum ScoreField {
+    Isolation,
+    Degree,
+    Weight,
+    ContentLen,
+    Priority,
+    /// Time since last visit by named agent. 1.0 = never visited, decays toward 0.
+    Recency(String),
 }
 
 /// Numeric comparison operator.
@@ -229,6 +243,111 @@ fn parse_duration_or_number(s: &str) -> Result<f64, String> {
     }
 }
 
+/// Parse composite sort: "isolation*0.7+recency(linker)*0.3"
+/// Each term is field or field(arg), optionally *weight (default 1.0).
+fn parse_composite_sort(s: &str) -> Result<Vec<(ScoreField, f64)>, String> {
+    let mut terms = Vec::new();
+    for term in s.split('+') {
+        let term = term.trim();
+        let (field_part, weight) = if let Some((f, w)) = term.rsplit_once('*') {
+            (f, w.parse::<f64>().map_err(|_| format!("bad weight: {}", w))?)
+        } else {
+            (term, 1.0)
+        };
+
+        // Parse field, possibly with (arg)
+        let field = if let Some((name, arg)) = field_part.split_once('(') {
+            let arg = arg.strip_suffix(')').ok_or("missing ) in sort field")?;
+            match name {
+                "recency" => ScoreField::Recency(arg.to_string()),
+                _ => return Err(format!("unknown parameterized sort field: {}", name)),
+            }
+        } else {
+            match field_part {
+                "isolation" => ScoreField::Isolation,
+                "degree"    => ScoreField::Degree,
+                "weight"    => ScoreField::Weight,
+                "content-len" => ScoreField::ContentLen,
+                "priority"  => ScoreField::Priority,
+                _ => return Err(format!("unknown sort field: {}", field_part)),
+            }
+        };
+        terms.push((field, weight));
+    }
+    if terms.is_empty() {
+        return Err("empty composite sort".into());
+    }
+    Ok(terms)
+}
+
+/// Compute a 0-1 score for a node on a single dimension.
+fn score_field(
+    field: &ScoreField,
+    key: &str,
+    store: &Store,
+    graph: &Graph,
+    precomputed: &CompositeCache,
+) -> f64 {
+    match field {
+        ScoreField::Isolation => {
+            let comm = graph.communities().get(key).copied().unwrap_or(0);
+            precomputed.isolation.get(&comm).copied().unwrap_or(1.0) as f64
+        }
+        ScoreField::Degree => {
+            let d = graph.degree(key) as f64;
+            let max = precomputed.max_degree.max(1.0);
+            (d / max).min(1.0)
+        }
+        ScoreField::Weight => {
+            store.nodes.get(key).map(|n| n.weight as f64).unwrap_or(0.0)
+        }
+        ScoreField::ContentLen => {
+            let len = store.nodes.get(key).map(|n| n.content.len()).unwrap_or(0) as f64;
+            let max = precomputed.max_content_len.max(1.0);
+            (len / max).min(1.0)
+        }
+        ScoreField::Priority => {
+            let p = crate::neuro::consolidation_priority(store, key, graph, None);
+            // Priority is already roughly 0-1 from the scoring function
+            p.min(1.0)
+        }
+        ScoreField::Recency(agent) => {
+            let last = store.last_visited(key, agent);
+            if last == 0 {
+                1.0 // never visited = highest recency score
+            } else {
+                let age = (crate::store::now_epoch() - last) as f64;
+                // Sigmoid decay: 1.0 at 7+ days, ~0.5 at 1 day, ~0.1 at 1 hour
+                let hours = age / 3600.0;
+                1.0 - (-0.03 * hours).exp()
+            }
+        }
+    }
+}
+
+/// Cached values for composite scoring (computed once per sort).
+struct CompositeCache {
+    isolation: HashMap<u32, f32>,
+    max_degree: f64,
+    max_content_len: f64,
+}
+
+impl CompositeCache {
+    fn build(items: &[(String, f64)], store: &Store, graph: &Graph) -> Self {
+        let max_degree = items.iter()
+            .map(|(k, _)| graph.degree(k) as f64)
+            .fold(0.0f64, f64::max);
+        let max_content_len = items.iter()
+            .map(|(k, _)| store.nodes.get(k).map(|n| n.content.len()).unwrap_or(0) as f64)
+            .fold(0.0f64, f64::max);
+        Self {
+            isolation: graph.community_isolation(),
+            max_degree,
+            max_content_len,
+        }
+    }
+}
+
 /// Parse a NodeType from a label.
 fn parse_node_type(s: &str) -> Result<NodeType, String> {
     match s {
@@ -302,7 +421,11 @@ impl Stage {
                 agent: value.to_string(),
             }),
             "sort" => {
-                let field = match value {
+                // Check for composite sort: field*weight+field*weight+...
+                let field = if value.contains('+') || value.contains('*') {
+                    SortField::Composite(parse_composite_sort(value)?)
+                } else {
+                    match value {
                         "priority"    => SortField::Priority,
                         "timestamp"   => SortField::Timestamp,
                         "content-len" => SortField::ContentLen,
@@ -310,6 +433,7 @@ impl Stage {
                         "weight"      => SortField::Weight,
                         "isolation"   => SortField::Isolation,
                         _ => return Err(format!("unknown sort field: {}", value)),
+                    }
                 };
                 Stage::Transform(Transform::Sort(field))
             }
@@ -579,6 +703,22 @@ pub fn run_transform(
                         pb.total_cmp(&pa) // desc
                     });
                 }
+                SortField::Composite(terms) => {
+                    let cache = CompositeCache::build(&items, store, graph);
+                    let scores: HashMap<String, f64> = items.iter()
+                        .map(|(key, _)| {
+                            let s: f64 = terms.iter()
+                                .map(|(field, w)| score_field(field, key, store, graph, &cache) * w)
+                                .sum();
+                            (key.clone(), s)
+                        })
+                        .collect();
+                    items.sort_by(|a, b| {
+                        let sa = scores.get(&a.0).copied().unwrap_or(0.0);
+                        let sb = scores.get(&b.0).copied().unwrap_or(0.0);
+                        sb.total_cmp(&sa) // highest composite score first
+                    });
+                }
             }
             items
         }