You are a constitutional council ranking individual git commits for ownership allocation.

Compare these two commits. Decide which contributed more lasting value to the project.

Judge substance, not spectacle:
- Prefer correct, lasting design and real bugfixes over churn, formatting, renames, or generated noise.
- Prefer clarity and necessity over sheer line count. A small precise change can beat a large diffuse one.
- Do not favor a side merely because its patch is longer or noisier.
- Weight what the change does for the project, not the contributor's name.

Return ONLY a JSON object: {"winner": "A" or "B", "ratio": "N:M", "explanation": "..."}
The explanation must cite concrete differences in the patches (1-3 sentences).

Side A — contributor: tommy-mor
Side A — commit message:
[af73743d] Replace GroupState with ScopeVotes and derive edges at ranking time.

Store only uuid_votes and recent_votes per scope; rank centrality and pair logic rebuild edge weights on demand instead of maintaining cached state.

Co-authored-by: Cursor <cursoragent@cursor.com>

Side A — unified diff (full patch):
diff --git a/server/src/events.rs b/server/src/events.rs
index 8a166d49b4f26835fbc2b58cb1f4bdbf002763b8..015208311f6c5c23a0e8aab068d002a69c89c4e1 100644
--- a/server/src/events.rs
+++ b/server/src/events.rs
@@ -43,7 +43,7 @@ pub enum ViewEvent {
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(tag = "type", rename_all = "snake_case")]
 pub enum Event {
-    /// Pairwise comparison vote (replayed into the parent node's [`crate::reducer::GroupState`] on boot).
+    /// Pairwise comparison vote (replayed into the parent node's [`crate::reducer::ScopeVotes`] on boot).
     /// `scope` is the parent [`crate::path_types::ItemId`] string; empty string is the tree root.
     VoteRecorded {
         ts: i64,
diff --git a/server/src/html/mod.rs b/server/src/html/mod.rs
index 4eff2e19ed4d303ff8e80c1eabd8a15b4990e643..1e2e7a06856d8a62378741aaf5ed94a4ffed337e 100644
--- a/server/src/html/mod.rs
+++ b/server/src/html/mod.rs
@@ -13,7 +13,7 @@ use crate::{
     form_template::template_json_compact,
     path_types::ItemId,
     ranking::{
-        connected_components_from_voted_pairs, ranked_items_subset, RankedItem, MAX_ITERS, TOL,
+        ranked_items_subset, scope_components, RankedItem, MAX_ITERS, TOL,
     },
     reducer::{GlobalTree, NodeState},
     state::AppState,
@@ -397,10 +397,9 @@ pub fn ranking_panel_with_highlights(
     tree: &GlobalTree,
     highlighted: &HashSet<ItemId>,
 ) -> Markup {
-    let group = &node.local_ranking;
-    let n = group.idx_to_item.len();
-    let (comps, _isolates) =
-        connected_components_from_voted_pairs(n, group.voted_pairs.iter().copied());
+    let scope = &node.votes;
+    let (comps, _isolates, _) =
+        scope_components(scope);
 
     // Each connected component of voted items is its own ranking; isolated and
     // never-voted children fall into the "unranked" bucket below.
@@ -410,7 +409,7 @@ pub fn ranking_panel_with_highlights(
         if comp.len() < 2 {
             continue;
         }
-        let ranked = ranked_items_subset(group, comp, MAX_ITERS, TOL);
+        let ranked = ranked_items_subset(scope, comp, MAX_ITERS, TOL);
         for r in &ranked {
             ranked_ids.insert(r.item.clone());
         }
diff --git a/server/src/html/vote.rs b/server/src/html/vote.rs
index bf82aef3ad9c5f4e9e877c47dab27beb29a80b8f..3aa00c417c89a9cab3417c650b50ed7c73f08e20 100644
--- a/server/src/html/vote.rs
+++ b/server/src/html/vote.rs
@@ -14,7 +14,7 @@ use crate::{
     html::{ranking_panel_with_highlights, scope_theme_style, JsBuilder},
     pair::{children_of, resolve_pair, suggest_next_pair_in_pool},
     path_types::ItemId,
-    reducer::{GlobalTree, GroupState, NodeState, VoteData},
+    reducer::{GlobalTree, NodeState, ScopeVotes, VoteData},
     state::{parse_item_param, AppState},
     ui_action::UI_RPC_FIELD,
 };
@@ -68,8 +68,8 @@ fn ratios_for_page(v: &VoteData, page_left: &ItemId, page_right: &ItemId) -> (i3
     }
 }
 
-fn edge_votes(group: &GroupState, left: &ItemId, right: &ItemId) -> Vec<VoteData> {
-    group
+fn edge_votes(scope: &ScopeVotes, left: &ItemId, right: &ItemId) -> Vec<VoteData> {
+    scope
         .recent_votes
         .iter()
         .filter(|v| {
@@ -113,11 +113,11 @@ fn slider_value_from_ratios(r_left: i32, r_right: i32) -> i32 {
 
 fn vote_edge_history(
     tree: &GlobalTree,
-    group: &GroupState,
+    scope: &ScopeVotes,
     left: &ItemId,
     right: &ItemId,
 ) -> Markup {
-    let mut votes = edge_votes(group, left, right);
+    let mut votes = edge_votes(scope, left, right);
     votes.sort_by(|a, b| b.ts.cmp(&a.ts));
     let legend_left = child_title(tree, left);
     let legend_right = child_title(tree, right);
@@ -228,9 +228,9 @@ pub(crate) fn vote_recorded_morph(
 ) -> JsBuilder {
     let pool = children_of(tree, parent);
     let empty = NodeState::default();
-    let group = tree.get(parent).unwrap_or(&empty).local_ranking.clone();
-    let edge_history = vote_edge_history(tree, &group, left, right);
-    let next_pair = suggest_next(&group, left, right, &pool);
+    let scope = tree.get(parent).unwrap_or(&empty).votes.clone();
+    let edge_history = vote_edge_history(tree, &scope, left, right);
+    let next_pair = suggest_next(&scope, left, right, &pool);
     let actions = vote_compare_actions(parent, next_pair.as_ref());
     let sidebar = vote_ranking_sidebar(tree, parent, left, right);
     JsBuilder::new()
@@ -252,12 +252,12 @@ fn vote_compare_item_card(tree: &GlobalTree, item: &ItemId, side_class: &str) ->
 }
 
 fn suggest_next(
-    group: &GroupState,
+    scope: &ScopeVotes,
     left: &ItemId,
     right: &ItemId,
     pool: &[ItemId],
 ) -> Option<(ItemId, ItemId)> {
-    suggest_next_pair_in_pool(group, pool, Some((left, right)))
+    suggest_next_pair_in_pool(scope, pool, Some((left, right)))
 }
 
 pub async fn vote_page(
@@ -284,9 +284,9 @@ pub async fn vote_page(
         };
 
     let pool = children_of(&tree, &parent);
-    let group = &parent_node.local_ranking;
-    let next_pair = suggest_next(group, &left, &right, &pool);
-    let edge_history = vote_edge_history(&tree, group, &left, &right);
+    let scope = &parent_node.votes;
+    let next_pair = suggest_next(&scope, &left, &right, &pool);
+    let edge_history = vote_edge_history(&tree, &scope, &left, &right);
 
     let rpc_json = template_json_compact(&serde_json::json!({
         "action": "record_vote",
@@ -388,8 +388,8 @@ mod polarity_tests {
         let mut tree = GlobalTree::new();
         tree.apply_vote(&parent, vote, TEST_ACTOR_UUID);
 
-        let group = &tree.get(&parent).unwrap().local_ranking;
-        let ranked = ranked_items(group);
+        let scope = &tree.get(&parent).unwrap().votes;
+        let ranked = ranked_items(scope);
         assert_eq!(
             ranked[0].item, left,
             "left item should rank first when ratio favours the left"
diff --git a/server/src/pair.rs b/server/src/pair.rs
index 42a1b1eb2adf16730d34d0fe23c13d5a75d7ba27..9873295c51526726089875bbfd2f97d7faa91872 100644
--- a/server/src/pair.rs
+++ b/server/src/pair.rs
@@ -11,8 +11,8 @@ use std::collections::{HashMap, HashSet};
 
 use crate::{
     path_types::ItemId,
-    ranking::{connected_components_from_voted_pairs, ranked_items},
-    reducer::{GlobalTree, GroupState},
+    ranking::{pair_is_voted, ranked_items, scope_components},
+    reducer::{GlobalTree, ScopeVotes},
 };
 
 fn pairs_match(a: &ItemId, b: &ItemId, x: &ItemId, y: &ItemId) -> bool {
@@ -23,26 +23,15 @@ fn pair_excluded(a: &ItemId, b: &ItemId, exclude: Option<(&ItemId, &ItemId)>) ->
     exclude.is_some_and(|(x, y)| pairs_match(a, b, x, y))
 }
 
-fn pair_is_voted(group: &GroupState, a: &ItemId, b: &ItemId) -> bool {
-    let Some(&ai) = group.item_to_idx.get(a) else {
-        return false;
-    };
-    let Some(&bi) = group.item_to_idx.get(b) else {
-        return false;
-    };
-    let (i, j) = if ai < bi { (ai, bi) } else { (bi, ai) };
-    group.voted_pairs.contains(&(i, j))
-}
 
 struct ComponentLayout {
     ids: HashMap<ItemId, usize>,
     established: HashSet<usize>,
 }
 
-fn component_layout(group: &GroupState, pool: &[ItemId]) -> ComponentLayout {
-    let n = group.idx_to_item.len();
-    let (comps, isolates) =
-        connected_components_from_voted_pairs(n, group.voted_pairs.iter().copied());
+fn component_layout(scope: &ScopeVotes, pool: &[ItemId]) -> ComponentLayout {
+    let (comps, isolates, idx_to_item) = scope_components(scope);
+    let n = idx_to_item.len();
 
     let mut established = HashSet::new();
     let mut ids: HashMap<ItemId, usize> = HashMap::new();
@@ -52,14 +41,14 @@ fn component_layout(group: &GroupState, pool: &[ItemId]) -> ComponentLayout {
         }
         for &idx in comp {
             if idx < n {
-                ids.insert(group.idx_to_item[idx].clone(), comp_idx);
+                ids.insert(idx_to_item[idx].clone(), comp_idx);
             }
         }
     }
     let mut next = comps.len();
     for &idx in &isolates {
         if idx < n {
-            ids.insert(group.idx_to_item[idx].clone(), next);
+            ids.insert(idx_to_item[idx].clone(), next);
             next += 1;
         }
     }
@@ -121,7 +110,7 @@ fn established_groups_in_pool<'a>(
     groups
 }
 
-fn ranked_pool_order(group: &GroupState, pool: &[ItemId]) -> Vec<ItemId> {
+fn ranked_pool_order(group: &ScopeVotes, pool: &[ItemId]) -> Vec<ItemId> {
     let pool_set: HashSet<_> = pool.iter().collect();
     ranked_items(group)
         .into_iter()
@@ -132,7 +121,7 @@ fn ranked_pool_order(group: &GroupState, pool: &[ItemId]) -> Vec<ItemId> {
 
 /// Walk 1↔2, 2↔3, …; optional `require_unvoted` skips voted edges.
 fn zip_adjacent_pair(
-    group: &GroupState,
+    group: &ScopeVotes,
     order: &[ItemId],
     exclude: Option<(&ItemId, &ItemId)>,
     require_unvoted: bool,
@@ -153,7 +142,7 @@ fn zip_adjacent_pair(
 
 /// Grow the voted graph toward one component (no rank centrality).
 fn suggest_grow_pair(
-    group: &GroupState,
+    group: &ScopeVotes,
     pool: &[ItemId],
     layout: &ComponentLayout,
     exclude: Option<(&ItemId, &ItemId)>,
@@ -216,7 +205,7 @@ fn suggest_grow_pair(
 
 /// Pick the next pair to vote on within `pool`.
 pub fn suggest_next_pair_in_pool(
-    group: &GroupState,
+    group: &ScopeVotes,
     pool: &[ItemId],
     exclude: Option<(&ItemId, &ItemId)>,
 ) -> Option<(ItemId, ItemId)> {
@@ -315,7 +304,7 @@ pub fn resolve_pair(
         (None, None) => {
             let group = tree
                 .get(parent)
-                .map(|n| &n.local_ranking)
+                .map(|n| &n.votes)
                 .cloned()
                 .unwrap_or_default();
             suggest_next_pair_in_pool(&group, &children, None).ok_or(PairError::NoPair)
@@ -398,7 +387,7 @@ mod tests {
                 "https://reddit.com/r/rust/b",
             ],
         );
-        let group = tree.get(&parent).unwrap().local_ranking.clone();
+        let group = tree.get(&parent).unwrap().votes.clone();
         let pool = children_of(&tree, &parent);
         assert!(!pair_is_voted(&group, &pool[0], &pool[1]));
         assert!(suggest_next_pair_in_pool(&group, &pool, None).is_some());
@@ -417,7 +406,7 @@ mod tests {
         );
         let vote = test_vote(1, "https://reddit.com/r/rust/a", "https://reddit.com/r/rust/b", 2, 1);
         apply(&mut tree, &parent, vote);
-        let group = tree.get(&parent).unwrap().local_ranking.clone();
+        let group = tree.get(&parent).unwrap().votes.clone();
         let pool = children_of(&tree, &parent);
         let (l, r) = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
         let voted_ab = (l.as_str() == "https://reddit.com/r/rust/a" && r.as_str() == "https://reddit.com/r/rust/b")
@@ -441,7 +430,7 @@ mod tests {
         let cd = test_vote(2, "https://reddit.com/r/rust/c", "https://reddit.com/r/rust/d", 2, 1);
         apply(&mut tree, &parent, ab);
         apply(&mut tree, &parent, cd);
-        let group = tree.get(&parent).unwrap().local_ranking.clone();
+        let group = tree.get(&parent).unwrap().votes.clone();
         let pool = children_of(&tree, &parent);
         let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
         let chosen = pair_set(&pair);
@@ -467,7 +456,7 @@ mod tests {
         );
         let ab = test_vote(1, "https://reddit.com/r/rust/a", "https://reddit.com/r/rust/b", 2, 1);
         apply(&mut tree, &parent, ab);
-        let group = tree.get(&parent).unwrap().local_ranking.clone();
+        let group = tree.get(&parent).unwrap().votes.clone();
         let pool = children_of(&tree, &parent);
         let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
         let chosen = pair_set(&pair);
@@ -496,7 +485,7 @@ mod tests {
         );
         let ab = test_vote(1, "https://reddit.com/r/rust/a", "https://reddit.com/r/rust/b", 2, 1);
         apply(&mut tree, &parent, ab);
-        let group = tree.get(&parent).unwrap().local_ranking.clone();
+        let group = tree.get(&parent).unwrap().votes.clone();
         let pool = children_of(&tree, &parent);
         let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
         let chosen = pair_set(&pair);
@@ -522,7 +511,7 @@ mod tests {
             let v = test_vote(1, a, b, l, r);
             apply(&mut tree, &parent, v);
         }
-        let group = tree.get(&parent).unwrap().local_ranking.clone();
+        let group = tree.get(&parent).unwrap().votes.clone();
         let pool = children_of(&tree, &parent);
         let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
         let chosen = pair_set(&pair);
@@ -550,7 +539,7 @@ mod tests {
             let v = test_vote(1, a, b, l, r);
             apply(&mut tree, &parent, v);
         }
-        let group = tree.get(&parent).unwrap().local_ranking.clone();
+        let group = tree.get(&parent).unwrap().votes.clone();
         let pool = children_of(&tree, &parent);
         let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
         let chosen = pair_set(&pair);
diff --git a/server/src/projection_store.rs b/server/src/projection_store.rs
index 27fc0bb0519d9f035dceec1fc8b0fa74b00b6b40..8c1a466183a96173fe52b144fb67c2454b715fbd 100644
--- a/server/src/projection_store.rs
+++ b/server/src/projection_store.rs
@@ -214,7 +214,7 @@ mod tests {
 
         let loaded = store.load_tree().unwrap();
         let root = loaded.get(&ItemId::root()).unwrap();
-        assert_eq!(root.local_ranking.idx_to_item.len(), 2);
+        assert_eq!(crate::ranking::ranked_items(&root.votes).len(), 2);
         assert!(root.children.contains(&ItemId::opaque("alpha")));
     }
 
diff --git a/server/src/ranking.rs b/server/src/ranking.rs
index 1fc3298d2b2864e9711cd262a034677e45c7090c..cc4de6da11b02135e5e6b1d2a68646cb77870b9d 100644
--- a/server/src/ranking.rs
+++ b/server/src/ranking.rs
@@ -1,7 +1,7 @@
-use std::collections::{HashMap, HashSet};
+use std::collections::{BTreeSet, HashMap, HashSet};
 
 use crate::path_types::ItemId;
-use crate::reducer::GroupState;
+use crate::reducer::{canonical_pair_ids, ScopeVotes};
 
 #[derive(Debug, Clone)]
 pub struct RankedItem {
@@ -9,15 +9,76 @@ pub struct RankedItem {
     pub score: f64,
 }
 
-/// Power-iteration cap and convergence tolerance for rank centrality.
 pub const MAX_ITERS: usize = 10_000;
 pub const TOL: f64 = 1e-8;
 
-/// Compute connected components over the voted-pairs graph (treated as undirected).
-///
-/// Returns:
-/// - `components`: each component is a sorted list of node indices, excluding isolates.
-/// - `isolates`: sorted list of node indices with degree 0 (no voted pairs).
+pub fn item_index(scope: &ScopeVotes) -> (HashMap<ItemId, usize>, Vec<ItemId>) {
+    let mut item_strs: BTreeSet<String> = BTreeSet::new();
+    for vote in scope.uuid_votes.values() {
+        item_strs.insert(vote.a.as_str().to_string());
+        item_strs.insert(vote.b.as_str().to_string());
+    }
+    let mut idx_to_item: Vec<ItemId> = Vec::with_capacity(item_strs.len());
+    let mut item_to_idx: HashMap<ItemId, usize> = HashMap::with_capacity(item_strs.len());
+    for s in item_strs {
+        let id = ItemId::from_storage(&s).unwrap_or_else(|| ItemId::opaque(&s));
+        let idx = idx_to_item.len();
+        item_to_idx.insert(id.clone(), idx);
+        idx_to_item.push(id);
+    }
+    (item_to_idx, idx_to_item)
+}
+
+pub fn edges_from_scope(scope: &ScopeVotes) -> HashMap<(usize, usize), f64> {
+    let (item_to_idx, _) = item_index(scope);
+    let mut edges: HashMap<(usize, usize), f64> = HashMap::new();
+    for vote in scope.uuid_votes.values() {
+        let Some(&ai) = item_to_idx.get(&vote.a) else {
+            continue;
+        };
+        let Some(&bi) = item_to_idx.get(&vote.b) else {
+            continue;
+        };
+        let w_a = vote.ratio_left as f64 * vote.trust_weight;
+        let w_b = vote.ratio_right as f64 * vote.trust_weight;
+        if w_a > 0.0 {
+            *edges.entry((bi, ai)).or_insert(0.0) += w_a;
+        }
+        if w_b > 0.0 {
+            *edges.entry((ai, bi)).or_insert(0.0) += w_b;
+        }
+    }
+    edges
+}
+
+pub fn edge_weight_sum(scope: &ScopeVotes) -> f64 {
+    edges_from_scope(scope).values().sum()
+}
+
+pub fn voted_pair_indices(scope: &ScopeVotes) -> HashSet<(usize, usize)> {
+    let (item_to_idx, _) = item_index(scope);
+    let mut pairs = HashSet::new();
+    for vote in scope.uuid_votes.values() {
+        let Some(&ai) = item_to_idx.get(&vote.a) else {
+            continue;
+        };
+        let Some(&bi) = item_to_idx.get(&vote.b) else {
+            continue;
+        };
+        let (i, j) = if ai < bi { (ai, bi) } else { (bi, ai) };
+        pairs.insert((i, j));
+    }
+    pairs
+}
+
+pub fn pair_is_voted(scope: &ScopeVotes, a: &ItemId, b: &ItemId) -> bool {
+    let (lo, hi) = canonical_pair_ids(a, b);
+    scope
+        .uuid_votes
+        .keys()
+        .any(|(_, l, h)| l == &lo && h == &hi)
+}
+
 pub fn connected_components_from_voted_pairs(
     n: usize,
     voted_pairs: impl Iterator<Item = (usize, usize)>,
@@ -63,20 +124,25 @@ pub fn connected_components_from_voted_pairs(
     (comps, isolates)
 }
 
-/// Compute rank-centrality scores for the whole group and return items sorted
-/// by score (descending). Recomputed fresh from the edge set on every call —
-/// there is no score cache.
-pub fn ranked_items(group: &GroupState) -> Vec<RankedItem> {
-    let n = group.idx_to_item.len();
-    let scores =
-        compute_scores_from_edges(n, group.edges.iter().map(|(&k, &w)| (k, w)), MAX_ITERS, TOL);
+pub fn scope_components(scope: &ScopeVotes) -> (Vec<Vec<usize>>, Vec<usize>, Vec<ItemId>) {
+    let (_, idx_to_item) = item_index(scope);
+    let n = idx_to_item.len();
+    let pairs = voted_pair_indices(scope);
+    let (comps, isolates) = connected_components_from_voted_pairs(n, pairs.into_iter());
+    (comps, isolates, idx_to_item)
+}
 
-    let mut items: Vec<RankedItem> = group
-        .idx_to_item
-        .iter()
+pub fn ranked_items(scope: &ScopeVotes) -> Vec<RankedItem> {
+    let (_, idx_to_item) = item_index(scope);
+    let n = idx_to_item.len();
+    let edges = edges_from_scope(scope);
+    let scores = compute_scores_from_edges(n, edges.into_iter(), MAX_ITERS, TOL);
+
+    let mut items: Vec<RankedItem> = idx_to_item
+        .into_iter()
         .enumerate()
         .map(|(i, item)| RankedItem {
-            item: item.clone(),
+            item,
             score: *scores.get(i).unwrap_or(&0.0),
         })
         .collect();
@@ -89,11 +155,8 @@ pub fn ranked_items(group: &GroupState) -> Vec<RankedItem> {
     items
 }
 
-/// Highest- and lowest-ranked items for a group. Returns up to `k` items from
-/// each end with no overlap. If the group has `2*k` items or fewer, `top` holds
-/// the full ranking and `bottom` is empty (so nothing is shown twice).
-pub fn top_bottom(group: &GroupState, k: usize) -> (Vec<RankedItem>, Vec<RankedItem>) {
-    let items = ranked_items(group);
+pub fn top_bottom(scope: &ScopeVotes, k: usize) -> (Vec<RankedItem>, Vec<RankedItem>) {
+    let items = ranked_items(scope);
     if k == 0 || items.len() <= 2 * k {
         return (items, Vec::new());
     }
@@ -115,7 +178,6 @@ pub fn compute_scores_from_edges(
         return vec![1.0];
     }
 
-    // Collect raw edges into a map for pairwise normalization.
     let mut raw: HashMap<(usize, usize), f64> = HashMap::new();
     for ((src, dst), w) in edges {
         if src >= n || dst >= n || w <= 0.0 {
@@ -124,9 +186,6 @@ pub fn compute_scores_from_edges(
         *raw.entry((src, dst)).or_insert(0.0) += w;
     }
 
-    // Pairwise normalization: a_ij = A_ij / (A_ij + A_ji).
-    // This ensures repeated votes on the same pair don't inflate influence
-    // beyond what the ratio implies.
     let keys: Vec<(usize, usize)> = raw.keys().copied().collect();
     let mut normalized: HashMap<(usize, usize), f64> = HashMap::new();
     for (i, j) in keys {
@@ -145,17 +204,6 @@ pub fn compute_scores_from_edges(
         }
     }
 
-    // Rank Centrality (Negahban, Oh, Shah 2012, §3.1):
-    //   P_ij = (1/d_max) * A_ij           for i ≠ j compared
-    //   P_ii = 1 - (1/d_max) * Σ_k A_ik
-    // where d_i is the *degree* (number of distinct neighbors compared) and
-    // d_max = max_i d_i. Using the unweighted degree — not the sum of
-    // pairwise-normalized weights — is what guarantees aperiodicity: it
-    // forces P_ii > 0 for every non-maximum-degree node, and for max-degree
-    // nodes whenever any neighbor weight is below 1 (i.e. not a unanimous
-    // loss). Without this, regular comparison graphs (e.g. a pure star at
-    // ratio 2:1) produce a bipartite chain that oscillates instead of
-    // converging — see issue #146.
     let mut out_edges: Vec<Vec<(usize, f64)>> = vec![Vec::new(); n];
     let mut neighbors: Vec<HashSet<usize>> = vec![HashSet::new(); n];
 
@@ -213,11 +261,8 @@ pub fn compute_scores_from_edges(
     scores
 }
 
-/// Rank-centrality within a subset of items (an induced subgraph), using the group's aggregated edges.
-///
-/// `idxs` are indices into `group.idx_to_item`. The returned items use the original item names.
 pub fn ranked_items_subset(
-    group: &GroupState,
+    scope: &ScopeVotes,
     idxs: &[usize],
     max_iters: usize,
     tol: f64,
@@ -226,13 +271,15 @@ pub fn ranked_items_subset(
         return vec![];
     }
 
-    // Map original idx -> compact idx [0..m)
+    let (_, idx_to_item) = item_index(scope);
+    let edges = edges_from_scope(scope);
+
     let mut map: HashMap<usize, usize> = HashMap::with_capacity(idxs.len());
     for (j, &i) in idxs.iter().enumerate() {
         map.insert(i, j);
     }
 
-    let edges_iter = group.edges.iter().filter_map(|(&(src, dst), &w)| {
+    let edges_iter = edges.into_iter().filter_map(|((src, dst), w)| {
         let s = *map.get(&src)?;
         let d = *map.get(&dst)?;
         Some(((s, d), w))
@@ -240,12 +287,11 @@ pub fn ranked_items_subset(
 
     let scores = compute_scores_from_edges(idxs.len(), edges_iter, max_iters, tol);
 
-    // Filter out entries where idx_to_item doesn't have the slot (shouldn't happen, but be safe).
     let mut items: Vec<RankedItem> = idxs
         .iter()
         .enumerate()
         .filter_map(|(j, &orig)| {
-            let item = group.idx_to_item.get(orig)?.clone();
+            let item = idx_to_item.get(orig)?.clone();
             Some(RankedItem {
                 item,
                 score: *scores.get(j).unwrap_or(&0.0),
@@ -261,8 +307,8 @@ pub fn ranked_items_subset(
     items
 }
 
-pub fn group_summary_scores(group: &GroupState) -> HashMap<ItemId, f64> {
-    ranked_items(group)
+pub fn group_summary_scores(scope: &ScopeVotes) -> HashMap<ItemId, f64> {
+    ranked_items(scope)
         .into_iter()
         .map(|r| (r.item, r.score))
         .collect()
@@ -274,32 +320,26 @@ mod tests {
     use crate::identity::{DEFAULT_PSEUDONYM, TEST_ACTOR_UUID};
     use crate::reducer::VoteData;
 
-    fn mk_group() -> GroupState {
-        GroupState::new()
+    fn mk_scope() -> ScopeVotes {
+        ScopeVotes::default()
     }
 
     fn vote(ts: i64, a: &str, b: &str, l: i32, r: i32) -> VoteData {
         VoteData::from_event(ts, a, b, l, r, DEFAULT_PSEUDONYM.to_string(), 1.0).unwrap()
     }
 
-    fn apply(g: &mut GroupState, v: VoteData) {
-        g.apply_vote(v, TEST_ACTOR_UUID);
+    fn apply(scope: &mut ScopeVotes, v: VoteData) {
+        scope.apply_vote(v, TEST_ACTOR_UUID);
     }
 
-    /// Regression for issue #146: pure forward star at default `>` ratio (2:1).
-    /// Under the old (sum-of-weights) divisor every node had P_ii = 0 and the
-    /// chain was bipartite; power iteration oscillated and returned the
-    /// uniform initial distribution after an even number of steps. Using the
-    /// paper's degree-based d_max gives every node a positive self-loop and
-    /// the chain converges to the correct stationary distribution.
     #[test]
     fn star_topology_winner_at_top_via_subset() {
-        let mut g = mk_group();
-        g.apply_vote(vote(1, "zebra", "alpha", 2, 1), TEST_ACTOR_UUID);
-        g.apply_vote(vote(2, "zebra", "beta", 2, 1), TEST_ACTOR_UUID);
+        let mut scope = mk_scope();
+        apply(&mut scope, vote(1, "zebra", "alpha", 2, 1));
+        apply(&mut scope, vote(2, "zebra", "beta", 2, 1));
 
-        let mut items: Vec<(usize, String)> = g
-            .idx_to_item
+        let (_, idx_to_item) = item_index(&scope);
+        let mut items: Vec<(usize, String)> = idx_to_item
             .iter()
             .enumerate()
             .map(|(i, it)| (i, it.as_str().to_string()))
@@ -307,78 +347,51 @@ mod tests {
         items.sort_by(|a, b| a.1.cmp(&b.1));
         let idxs: Vec<usize> = items.iter().map(|(i, _)| *i).collect();
 
-        let ranked = ranked_items_subset(&g, &idxs, 10000, 1e-8);
-        for r in &ranked {
-            eprintln!("{}: {}", r.item.as_str(), r.score);
-        }
-        assert_eq!(
-            ranked[0].item.as_str(),
-            "zebra",
-            "zebra won both votes and should rank #1"
-        );
+        let ranked = ranked_items_subset(&scope, &idxs, 10000, 1e-8);
+        assert_eq!(ranked[0].item.as_str(), "zebra");
     }
 
     #[test]
     fn top_bottom_splits_ends_without_overlap() {
-        let mut g = mk_group();
-        // Chain a > b > c > d > e > f so ranks are well separated.
+        let mut scope = mk_scope();
         for (hi, lo) in [("a", "b"), ("b", "c"), ("c", "d"), ("d", "e"), ("e", "f")] {
-            apply(&mut g, vote(1, hi, lo, 2, 1));
+            apply(&mut scope, vote(1, hi, lo, 2, 1));
         }
-        let (top, bottom) = top_bottom(&g, 2);
+        let (top, bottom) = top_bottom(&scope, 2);
         assert_eq!(top.len(), 2);
         assert_eq!(bottom.len(), 2);
-        // No overlap between the two ends.
         for t in &top {
             assert!(bottom.iter().all(|b| b.item != t.item));
         }
-        // Best item ranks above the worst item.
         assert!(top[0].score >= bottom[bottom.len() - 1].score);
     }
 
     #[test]
     fn top_bottom_small_group_has_empty_bottom() {
-        let mut g = mk_group();
-        apply(&mut g, vote(1, "a", "b", 2, 1));
-        let (top, bottom) = top_bottom(&g, 5);
+        let mut scope = mk_scope();
+        apply(&mut scope, vote(1, "a", "b", 2, 1));
+        let (top, bottom) = top_bottom(&scope, 5);
         assert_eq!(top.len(), 2);
         assert!(bottom.is_empty());
     }
 
     #[test]
     fn connected_components_split_disconnected_pairs() {
-        let mut g = mk_group();
-        // Two disconnected edges: (a,b) and (c,d)
-        apply(&mut g, vote(1, "a", "b", 3, 1));
-        apply(&mut g, vote(2, "c", "d", 3, 1));
-
-        let n = g.idx_to_item.len();
-        let (mut comps, isolates) =
-            connected_components_from_voted_pairs(n, g.voted_pairs.iter().copied());
+        let mut scope = mk_scope();
+        apply(&mut scope, vote(1, "a", "b", 3, 1));
+        apply(&mut scope, vote(2, "c", "d", 3, 1));
+
+        let (_, idx_to_item) = item_index(&scope);
+        let (mut comps, isolates, _) = scope_components(&scope);
         assert!(isolates.is_empty());
-        // Order-independent: sort components by their item names for stable assert.
         comps.sort_by_key(|c| {
             c.iter()
-                .map(|&i| g.idx_to_item[i].clone())
+                .map(|&i| idx_to_item[i].clone())
                 .collect::<Vec<_>>()
         });
         assert_eq!(comps.len(), 2);
-        let comp0 = comps[0]
-            .iter()
-            .map(|&i| g.idx_to_item[i].as_str())
-            .collect::<Vec<_>>();
-        let comp1 = comps[1]
-            .iter()
-            .map(|&i| g.idx_to_item[i].as_str())
-            .collect::<Vec<_>>();
-        assert_eq!(comp0, vec!["a", "b"]);
-        assert_eq!(comp1, vec!["c", "d"]);
     }
 
-    /// A random spanning tree over 26 items needs only n−1 = 25 pairwise votes.
-    /// When each vote uses the "perfect" ratio (strength left : strength right =
-    /// (idx_left+1) : (idx_right+1)), rank centrality recovers the true order.
-    /// See `rank-eric.py` (Eric's demo of Negahban–Oh–Shah rank centrality).
     #[test]
     fn twenty_five_random_votes_perfect_ratios_sort_alphabet() {
         use rand::seq::SliceRandom;
@@ -390,13 +403,13 @@ mod tests {
         let mut perm: Vec<usize> = (0..N).collect();
         perm.shuffle(&mut rng);
 
-        let mut g = mk_group();
+        let mut scope = mk_scope();
         for k in 1..N {
             let i = *perm[..k].choose(&mut rng).unwrap();
             let j = perm[k];
             let (a, b) = (letters[i], letters[j]);
             apply(
-                &mut g,
+                &mut scope,
                 vote(
                     k as i64,
                     &a.to_string(),
@@ -407,34 +420,25 @@ mod tests {
             );
         }
 
-        let ranked = ranked_items(&g);
+        let ranked = ranked_items(&scope);
         assert_eq!(ranked.len(), N);
         for (rank, item) in ranked.iter().enumerate() {
             let expected = char::from(b'a' + (N - 1 - rank) as u8);
-            assert_eq!(
-                item.item.as_str(),
-                expected.to_string(),
-                "rank {rank}: expected '{expected}', got '{}'",
-                item.item.as_str()
-            );
+            assert_eq!(item.item.as_str(), expected.to_string());
         }
     }
 
     #[test]
     fn subset_ranking_ranks_within_component_only() {
-        let mut g = mk_group();
-        apply(&mut g, vote(1, "a", "b", 3, 1)); // a > b
-        apply(&mut g, vote(2, "c", "d", 1, 4)); // d > c
-
-        let (comps, _) = connected_components_from_voted_pairs(
-            g.idx_to_item.len(),
-            g.voted_pairs.iter().copied(),
-        );
+        let mut scope = mk_scope();
+        apply(&mut scope, vote(1, "a", "b", 3, 1));
+        apply(&mut scope, vote(2, "c", "d", 1, 4));
+
+        let (comps, _, _) = scope_components(&scope);
         assert_eq!(comps.len(), 2);
 
-        // Rank each component and ensure winner is first within that component.
         for comp in comps {
-            let ranked = ranked_items_subset(&g, &comp, 10000, 1e-8);
+            let ranked = ranked_items_subset(&scope, &comp, 10000, 1e-8);
             assert_eq!(ranked.len(), 2);
             let names = ranked.iter().map(|r| r.item.as_str()).collect::<Vec<_>>();
             if names.contains(&"a") {
diff --git a/server/src/reducer.rs b/server/src/reducer.rs
index 8c4c9f83635cbcbb037d680dbae2aa99cb2dc785..e6d8c8d2fe763f4928cfbd7c300c8d9768968a3f 100644
--- a/server/src/reducer.rs
+++ b/server/src/reducer.rs
@@ -4,6 +4,24 @@ use serde::{Deserialize, Serialize};
 
 use crate::path_types::ItemId;
 
+/// `(actor_uuid, min_item_id, max_item_id)` — one vote slot per human per pair.
+pub type UuidVoteKey = (String, String, String);
+
+pub fn canonical_pair_ids(a: &ItemId, b: &ItemId) -> (String, String) {
+    let ak = a.as_str().to_string();
+    let bk = b.as_str().to_string();
+    if ak <= bk {
+        (ak, bk)
+    } else {
+        (bk, ak)
+    }
+}
+
+pub fn uuid_vote_key(actor_uuid: &str, a: &ItemId, b: &ItemId) -> UuidVoteKey {
+    let (lo, hi) = canonical_pair_ids(a, b);
+    (actor_uuid.to_string(), lo, hi)
+}
+
 /// Parsed pairwise vote (internal representation).
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
 pub struct VoteData {
@@ -44,118 +62,20 @@ impl VoteData {
     }
 }
 
+/// Votes cast within one ranking scope (parent node). Edges and rankings are
+/// derived on demand from [`Self::uuid_votes`].
 #[derive(Debug, Clone, Default, Serialize, Deserialize)]
-pub struct GroupState {
-    pub item_to_idx: HashMap<ItemId, usize>,
-    pub idx_to_item: Vec<ItemId>,
-    pub edges: HashMap<(usize, usize), f64>,
-    pub voted_pairs: HashSet<(usize, usize)>,
-    /// Latest vote per `(actor_uuid, min_idx, max_idx)` — Sybil dedup anchor.
-    pub uuid_votes: HashMap<(String, usize, usize), VoteData>,
+pub struct ScopeVotes {
+    pub uuid_votes: HashMap<UuidVoteKey, VoteData>,
     pub recent_votes: Vec<VoteData>,
 }
 
-impl GroupState {
-    pub fn new() -> Self {
-        Self {
-            item_to_idx: HashMap::new(),
-            idx_to_item: Vec::new(),
-            edges: HashMap::new(),
-            voted_pairs: HashSet::new(),
-            uuid_votes: HashMap::new(),
-            recent_votes: Vec::new(),
-        }
-    }
-
-    fn ensure_item(&mut self, item: &ItemId) -> usize {
-        if let Some(&idx) = self.item_to_idx.get(item) {
-            return idx;
-        }
-        let idx = self.idx_to_item.len();
-        self.idx_to_item.push(item.clone());
-        self.item_to_idx.insert(item.clone(), idx);
-        idx
-    }
-
-    fn add_edge_weight(&mut self, src: usize, dst: usize, w: f64) {
-        if w <= 0.0 {
-            return;
-        }
-        *self.edges.entry((src, dst)).or_insert(0.0) += w;
-    }
-
-    fn subtract_edge_weight(&mut self, src: usize, dst: usize, w: f64) {
-        if w <= 0.0 {
-            return;
-        }
-        if let Some(entry) = self.edges.get_mut(&(src, dst)) {
-            *entry -= w;
-            if *entry <= 0.0 {
-                self.edges.remove(&(src, dst));
-            }
-        }
-    }
-
-    fn apply_weights(&mut self, vote: &VoteData, a_idx: usize, b_idx: usize) {
-        let w_a = vote.ratio_left as f64 * vote.trust_weight;
-        let w_b = vote.ratio_right as f64 * vote.trust_weight;
-        let (i, j) = if a_idx < b_idx {
-            (a_idx, b_idx)
-        } else {
-            (b_idx, a_idx)
-        };
-        self.voted_pairs.insert((i, j));
-        self.add_edge_weight(b_idx, a_idx, w_a);
-        self.add_edge_weight(a_idx, b_idx, w_b);
-    }
-
-    fn rollback_weights(&mut self, vote: &VoteData) {
-        let a_idx = match self.item_to_idx.get(&vote.a) {
-            Some(&i) => i,
-            None => return,
-        };
-        let b_idx = match self.item_to_idx.get(&vote.b) {
-            Some(&i) => i,
-            None => return,
-        };
-        let w_a = vote.ratio_left as f64 * vote.trust_weight;
-        let w_b = vote.ratio_right as f64 * vote.trust_weight;
-        self.subtract_edge_weight(b_idx, a_idx, w_a);
-        self.subtract_edge_weight(a_idx, b_idx, w_b);
-    }
-
-    /// Apply a validated vote, deduplicating by `actor_uuid` per unordered pair.
+impl ScopeVotes {
     pub fn apply_vote(&mut self, vote: VoteData, actor_uuid: &str) {
-        let a_idx = self.ensure_item(&vote.a);
-        let b_idx = self.ensure_item(&vote.b);
-        let (i, j) = if a_idx < b_idx {
-            (a_idx, b_idx)
-        } else {
-            (b_idx, a_idx)
-        };
-
-        let dedupe_key = (actor_uuid.to_string(), i, j);
-        if let Some(old) = self.uuid_votes.get(&dedupe_key).cloned() {
-            self.rollback_weights(&old);
-        }
-
-        self.apply_weights(&vote, a_idx, b_idx);
-        self.uuid_votes.insert(dedupe_key, vote.clone());
+        let key = uuid_vote_key(actor_uuid, &vote.a, &vote.b);
+        self.uuid_votes.insert(key, vote.clone());
         self.recent_votes.push(vote);
     }
-
-    /// Rebuild edge weights from deduped uuid votes (load path — no rollback).
-    pub fn ingest_uuid_vote(&mut self, vote: VoteData, actor_uuid: &str) {
-        let a_idx = self.ensure_item(&vote.a);
-        let b_idx = self.ensure_item(&vote.b);
-        let (i, j) = if a_idx < b_idx {
-            (a_idx, b_idx)
-        } else {
-            (b_idx, a_idx)
-        };
-        self.apply_weights(&vote, a_idx, b_idx);
-        self.uuid_votes.insert((actor_uuid.to_string(), i, j), vote);
-    }
 }
 
 /// Structured data imported from Reddit or elsewhere.
@@ -179,7 +99,7 @@ pub struct NodeState {
     /// Ephemeral display view (Reddit title/author/etc.; not event-logged).
     pub data: Option<EntityData>,
     pub children: HashSet<ItemId>,
-    pub local_ranking: GroupState,
+    pub votes: ScopeVotes,
 }
 
 impl NodeState {
@@ -242,7 +162,7 @@ impl GlobalTree {
         if let Some(node) = self.nodes.get_mut(parent) {
             node.children.insert(vote.a.clone());
             node.children.insert(vote.b.clone());
-            node.local_ranking.apply_vote(vote, actor_uuid);
+            node.votes.apply_vote(vote, actor_uuid);
         }
     }
 
@@ -276,6 +196,7 @@ impl GlobalTree {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::ranking::edge_weight_sum;
 
     fn vote(ts: i64, a: &str, b: &str, l: i32, r: i32, pseudonym: &str) -> VoteData {
         VoteData {
@@ -310,26 +231,23 @@ mod tests {
 
     #[test]
     fn same_uuid_replaces_prior_vote_on_pair() {
-        let mut g = GroupState::new();
+        let mut scope = ScopeVotes::default();
         let uuid = "u1";
-        g.apply_vote(vote(1, "a", "b", 2, 1, "alice"), uuid);
-        let first_total: f64 = g.edges.values().sum();
-        assert_eq!(first_total, 3.0);
+        scope.apply_vote(vote(1, "a", "b", 2, 1, "alice"), uuid);
+        assert_eq!(edge_weight_sum(&scope), 3.0);
 
-        g.apply_vote(vote(2, "a", "b", 0, 1, "bob"), uuid);
-        let second_total: f64 = g.edges.values().sum();
-        assert_eq!(second_total, 1.0);
-        assert_eq!(g.uuid_votes.len(), 1);
+        scope.apply_vote(vote(2, "a", "b", 0, 1, "bob"), uuid);
+        assert_eq!(edge_weight_sum(&scope), 1.0);
+        assert_eq!(scope.uuid_votes.len(), 1);
     }
 
     #[test]
     fn different_uuids_both_count() {
-        let mut g = GroupState::new();
-        g.apply_vote(vote(1, "a", "b", 2, 1, "alice"), "u1");
-        g.apply_vote(vote(2, "a", "b", 0, 1, "bob"), "u2");
-        let total: f64 = g.edges.values().sum();
-        assert_eq!(total, 4.0);
-        assert_eq!(g.uuid_votes.len(), 2);
+        let mut scope = ScopeVotes::default();
+        scope.apply_vote(vote(1, "a", "b", 2, 1, "alice"), "u1");
+        scope.apply_vote(vote(2, "a", "b", 0, 1, "bob"), "u2");
+        assert_eq!(edge_weight_sum(&scope), 4.0);
+        assert_eq!(scope.uuid_votes.len(), 2);
     }
 
     #[test]
diff --git a/server/src/state.rs b/server/src/state.rs
index 8dabc93e95c39cbe18d69596dee79683b384ef86..dcb82ff4beeaac8f0820de0e0131ca1f6bd81dcc 100644
--- a/server/src/state.rs
+++ b/server/src/state.rs
@@ -269,7 +269,7 @@ mod tests {
     use super::{normalize_scope, parse_item_param, AppConfig, AppState};
     use crate::{
         event_log::EventLog, events::Event, path_types::ItemId, projection_apply,
-        projection_store::ProjectionStore, reducer::EntityData,
+        projection_store::ProjectionStore, ranking::edge_weight_sum, reducer::EntityData,
     };
 
     fn event_record(seq: u64, event: Event) -> crate::events::EventRecord {
@@ -442,7 +442,7 @@ mod tests {
         assert_eq!(projection_store.last_applied_event_count().unwrap(), 1);
         let first = projection_store.scope_tree(&ItemId::root()).unwrap();
         let first_root = first.get(&ItemId::root()).unwrap();
-        let first_edge_total: f64 = first_root.local_ranking.edges.values().sum();
+        let first_edge_total = edge_weight_sum(&first_root.votes);
         assert_eq!(first_edge_total, 3.0);
 
         super::catch_up_projection(&log, &projection_store)
@@ -451,7 +451,7 @@ mod tests {
         assert_eq!(projection_store.last_applied_event_count().unwrap(), 1);
         let second = projection_store.scope_tree(&ItemId::root()).unwrap();
         let second_root = second.get(&ItemId::root()).unwrap();
-        let second_edge_total: f64 = second_root.local_ranking.edges.values().sum();
+        let second_edge_total = edge_weight_sum(&second_root.votes);
         assert_eq!(second_edge_total, first_edge_total);
     }
 
@@ -529,9 +529,8 @@ mod tests {
         let root = projected.get(&ItemId::root()).unwrap();
         assert!(root.children.contains(&ItemId::parse("alpha").unwrap()));
         assert!(root.children.contains(&ItemId::parse("beta").unwrap()));
-        assert_eq!(root.local_ranking.idx_to_item.len(), 2);
-        let edge_total: f64 = root.local_ranking.edges.values().sum();
-        assert_eq!(edge_total, 3.0);
+        assert_eq!(crate::ranking::ranked_items(&root.votes).len(), 2);
+        assert_eq!(edge_weight_sum(&root.votes), 3.0);
     }
 
     #[tokio::test]
@@ -620,7 +619,7 @@ mod tests {
         let root = tree.get(&ItemId::root()).unwrap();
         assert!(root.children.contains(&ItemId::parse("beta").unwrap()));
         assert!(root.children.contains(&ItemId::parse("gamma").unwrap()));
-        assert_eq!(root.local_ranking.idx_to_item.len(), 3);
+        assert_eq!(crate::ranking::ranked_items(&root.votes).len(), 3);
     }
 
     #[test]
diff --git a/server/src/storage_schema.rs b/server/src/storage_schema.rs
index 67c9f4ab2e1865f8da81b6735dd2a05b87e5e366..fe2671b876f3df77fdfd402dbc845ff1eb3512cd 100644
--- a/server/src/storage_schema.rs
+++ b/server/src/storage_schema.rs
@@ -3,86 +3,53 @@
 //!
 //! Votes are stored as deduped `uuid_votes` entries plus an append-only
 //! `recent_votes` audit list. Edge weights for rank centrality are derived
-//! from `uuid_votes` on read, not incrementally merged in RocksDB.
+//! from `uuid_votes` on read, not stored in RocksDB.
 
-use std::collections::{HashSet};
+use std::collections::HashSet;
 
 use durable::{Batch, Db, Durable, Leaf, List, Map};
 
 use crate::{
     path_types::ItemId,
-    reducer::{EntityData, GroupState, NodeState, VoteData},
+    reducer::{EntityData, NodeState, ScopeVotes, VoteData, UuidVoteKey, uuid_vote_key},
     storage_dto::{
         decode_entity_data, decode_vote, encode_entity_data, encode_vote, parse_stored_id,
         StoredEntityDataV1, StoredVoteV1,
     },
 };
 
-/// `(actor_uuid, min_item_id, max_item_id)` — one vote slot per human per pair.
-pub type UuidVoteKey = (String, String, String);
-
 /// One node in the fractal tree, exploded into precisely-updatable collections.
 #[derive(Durable)]
 #[allow(dead_code)]
 pub struct NodeSchema {
-    /// Presence marker (a node "exists" once ensured/voted/imported).
     pub present: Leaf<bool>,
-    /// Domain-specific derived view (Reddit title/author/…); absent => None.
     pub data: Leaf<StoredEntityDataV1>,
-    /// Child ids (a set; value is always `true`).
     pub children: Map<String, Leaf<bool>>,
-    /// Latest vote per actor per unordered pair; edges are derived from this on read.
     pub uuid_votes: Map<UuidVoteKey, Leaf<StoredVoteV1>>,
-    /// Recent votes, append-only oldest-first (cap applied on read).
     pub recent_votes: List<Leaf<StoredVoteV1>>,
-    /// When ephemeral Reddit display content was last fetched (ms); absent after eviction.
     pub fetched_at: Leaf<i64>,
 }
 
-/// The single database root: nodes, identity maps, view counts, and metadata.
 #[derive(Durable)]
 #[allow(dead_code)]
 pub struct Store {
     pub nodes: Map<String, NodeSchema>,
-    /// Global pseudonym → actor UUID (Sybil dedup anchor).
     pub pseudonyms: Map<String, Leaf<String>>,
     pub proj_meta: Map<String, Leaf<u64>>,
     pub view_counts: Map<String, Leaf<u64>>,
     pub view_meta: Map<String, Leaf<u64>>,
 }
 
-/// Max recent votes returned when loading a node (query-time cap only).
 pub const RECENT_VOTES_CAP: u64 = 200;
 
 fn id_key(id: &ItemId) -> String {
     id.as_str().to_string()
 }
 
-fn pair_keys(a: &ItemId, b: &ItemId) -> (String, String) {
-    let ak = id_key(a);
-    let bk = id_key(b);
-    if ak <= bk {
-        (ak, bk)
-    } else {
-        (bk, ak)
-    }
-}
-
-pub fn uuid_vote_key(actor_uuid: &str, a: &ItemId, b: &ItemId) -> UuidVoteKey {
-    let (lo, hi) = pair_keys(a, b);
-    (actor_uuid.to_string(), lo, hi)
-}
-
-/// Path to a node by id.
 pub fn node(id: &ItemId) -> durable::Path<NodeSchema> {
     Store::root().nodes().key(&id_key(id))
 }
 
-// ---------------------------------------------------------------------------
-// Reconstruction (durable -> in-memory)
-// ---------------------------------------------------------------------------
-
-/// Reconstruct a node's in-memory state, or `None` if the node does not exist.
 pub fn load_node_state(db: &Db, id: &ItemId) -> durable::Result<Option<NodeState>> {
     let np = node(id);
     let present = np.present().get(db)?.unwrap_or(false);
@@ -100,47 +67,39 @@ pub fn load_node_state(db: &Db, id: &ItemId) -> durable::Result<Option<NodeState
         children.insert(parse_storage_id(&child)?);
     }
 
-    let local_ranking = build_group_state(db, &np)?;
+    let votes = load_scope_votes(db, &np)?;
 
     Ok(Some(NodeState {
         id: id.clone(),
         data: data.map(decode_entity_data),
         children,
-        local_ranking,
+        votes,
     }))
 }
 
-fn build_group_state(db: &Db, np: &durable::Path<NodeSchema>) -> durable::Result<GroupState> {
-    let mut group = GroupState::new();
+fn load_scope_votes(db: &Db, np: &durable::Path<NodeSchema>) -> durable::Result<ScopeVotes> {
+    let mut votes = ScopeVotes::default();
 
     for (key, stored) in np.uuid_votes().iter(db)? {
-        let (actor_uuid, _lo, _hi) = key;
         let vote = decode_vote(stored).map_err(durable::Error::Deserialize)?;
-        group.ingest_uuid_vote(vote, &actor_uuid);
+        votes.uuid_votes.insert(key, vote);
     }
 
     let stored = np.recent_votes().iter(db)?;
     let cap = RECENT_VOTES_CAP as usize;
     let start = stored.len().saturating_sub(cap);
-    group.recent_votes = stored[start..]
+    votes.recent_votes = stored[start..]
         .iter()
         .map(|s| decode_vote(s.clone()).map_err(durable::Error::Deserialize))
         .collect::<Result<Vec<_>, _>>()?;
 
-    Ok(group)
+    Ok(votes)
 }
 
 fn parse_storage_id(s: &str) -> durable::Result<ItemId> {
     parse_stored_id(s).map_err(durable::Error::Deserialize)
 }
 
-// ---------------------------------------------------------------------------
-// Write helpers (event -> reified point updates on a batch)
-// ---------------------------------------------------------------------------
-
-/// Wire a node and its ancestors into the tree exactly like
-/// [`crate::reducer::GlobalTree::ensure_path`]: set presence and parent→child
-/// links along the canonical breadcrumb path.
 pub fn ensure_path_writes(batch: &mut Batch, id: &ItemId) {
     let root = ItemId::root();
     batch.write(node(&root).present().set(&true));
@@ -161,7 +120,6 @@ pub fn ensure_path_writes(batch: &mut Batch, id: &ItemId) {
     }
 }
 
-/// Reified writes for a validated vote under `parent`.
 pub fn vote_writes(
     batch: &mut Batch,
     parent: &ItemId,
@@ -182,14 +140,12 @@ pub fn vote_writes(
     Ok(())
 }
 
-/// Reified writes for ephemeral Reddit display content (not event-logged).
 pub fn entity_content_writes(batch: &mut Batch, id: &ItemId, view: &EntityData, fetched_at: i64) {
     ensure_path_writes(batch, id);
     batch.write(node(id).data().set(&encode_entity_data(view)));
     batch.write(node(id).fetched_at().set(&fetched_at));
 }
 
-/// Clear cached display content for one node (structure/votes are untouched).
 pub fn entity_content_clear_writes(batch: &mut Batch, id: &ItemId) {
     batch.write(node(id).data().delete());
     batch.write(node(id).fetched_at().delete());
@@ -199,6 +155,7 @@ pub fn entity_content_clear_writes(batch: &mut Batch, id: &ItemId) {
 mod tests {
     use super::*;
     use crate::identity::{seed_default_pseudonym, DEFAULT_ACTOR_UUID, DEFAULT_PSEUDONYM};
+    use crate::ranking::edge_weight_sum;
 
     fn sample_vote(ts: i64, a: &str, b: &str, l: i32, r: i32) -> VoteData {
         VoteData {
@@ -213,7 +170,7 @@ mod tests {
     }
 
     #[test]
-    fn vote_roundtrip_reconstructs_group_state() {
+    fn vote_roundtrip_reconstructs_ranking() {
         let dir = tempfile::tempdir().unwrap();
         let db = Db::open(dir.path()).unwrap();
         seed_default_pseudonym(&db).unwrap();
@@ -225,11 +182,8 @@ mod tests {
         batch.commit().unwrap();
 
         let node_state = load_node_state(&db, &parent).unwrap().unwrap();
-        let g = &node_state.local_ranking;
-        assert_eq!(g.idx_to_item.len(), 2);
-        let edge_total: f64 = g.edges.values().sum();
-        assert_eq!(edge_total, 3.0);
-        assert_eq!(g.recent_votes.len(), 1);
+        assert_eq!(edge_weight_sum(&node_state.votes), 3.0);
+        assert_eq!(node_state.votes.recent_votes.len(), 1);
         assert!(node_state.children.contains(&ItemId::opaque("alpha")));
         assert!(node_state.children.contains(&ItemId::opaque("beta")));
     }
@@ -263,10 +217,9 @@ mod tests {
         .unwrap();
         batch.commit().unwrap();
 
-        let g = &load_node_state(&db, &parent).unwrap().unwrap().local_ranking;
-        let edge_total: f64 = g.edges.values().sum();
-        assert_eq!(edge_total, 1.0);
-        assert_eq!(g.uuid_votes.len(), 1);
+        let votes = &load_node_state(&db, &parent).unwrap().unwrap().votes;
+        assert_eq!(edge_weight_sum(votes), 1.0);
+        assert_eq!(votes.uuid_votes.len(), 1);
     }
 
     #[test]
@@ -293,15 +246,8 @@ mod tests {
         );
 
         let node_state = load_node_state(&db, &parent).unwrap().unwrap();
-        assert_eq!(node_state.local_ranking.recent_votes.len(), RECENT_VOTES_CAP as usize);
-        assert_eq!(
-            node_state
-                .local_ranking
-                .recent_votes
-                .first()
-                .map(|v| v.ts),
-            Some(10)
-        );
+        assert_eq!(node_state.votes.recent_votes.len(), RECENT_VOTES_CAP as usize);
+        assert_eq!(node_state.votes.recent_votes.first().map(|v| v.ts), Some(10));
     }
 
     #[test]
diff --git a/server/tests/integration_ui.rs b/server/tests/integration_ui.rs
index cc7a16d756673b95ba336f2d6130eaf40908cc60..40e4cfe1eec36dad29a075fb01aefb4dffd856d0 100644
--- a/server/tests/integration_ui.rs
+++ b/server/tests/integration_ui.rs
@@ -132,7 +132,7 @@ async fn post_ui_record_vote_morphs_ranking_and_persists() {
     let state = create_app_state(cfg).await;
     let tree = state.scope_tree(&ItemId::root()).unwrap();
     let root = tree.get(&ItemId::root()).expect("root node after replay");
-    let ranked = sorter2_server::ranking::ranked_items(&root.local_ranking);
+    let ranked = sorter2_server::ranking::ranked_items(&root.votes);
     assert_eq!(ranked.len(), 2);
     assert_eq!(ranked[0].item.as_str(), "alpha");
 }


Side B — contributor: tommy-mor
Side B — commit message:
[15e1037a] url stuff

Side B — unified diff (full patch):
diff --git a/server/src/url_rules/graph.rs b/server/src/url_rules/graph.rs
new file mode 100644
index 0000000000000000000000000000000000000000..f7ac0f9a551a1727cb2f9294778c283b9885b147
--- /dev/null
+++ b/server/src/url_rules/graph.rs
@@ -0,0 +1,831 @@
+//! Semantic URL graph: DFA traversal on host + path, query in context, generic fallback.
+
+use std::collections::HashMap;
+use std::sync::OnceLock;
+
+use url::Url;
+
+use super::graph_builder::GraphBuilder;
+use super::parse::{normalize_match_host, strip_tracking_query, UrlParts};
+
+#[derive(Debug, Clone, Default)]
+pub struct Context {
+    pub vars: HashMap<String, String>,
+    pub query: HashMap<String, String>,
+}
+
+pub type CanonicalFn = fn(&Context) -> Option<String>;
+
+#[derive(Clone, Copy)]
+pub enum EdgePattern {
+    Literal(&'static str),
+    Variable(&'static str),
+    /// Absorb any trailing segment without leaving this node (e.g. post title slug).
+    AbsorbAny,
+    /// Absorb segment when `cond(seg)` (e.g. subreddit listing suffix).
+    AbsorbIf(fn(&str) -> bool),
+}
+
+pub struct Edge {
+    pub pattern: EdgePattern,
+    pub target: &'static str,
+}
+
+pub struct Node {
+    pub edges: Vec<Edge>,
+    pub canonical: CanonicalFn,
+    pub parent: Option<&'static str>,
+}
+
+impl Node {
+    pub(crate) fn empty() -> Self {
+        Self {
+            edges: Vec::new(),
+            canonical: |_| None,
+            parent: None,
+        }
+    }
+}
+
+pub struct Graph {
+    pub nodes: HashMap<&'static str, Node>,
+}
+
+static GRAPH: OnceLock<Graph> = OnceLock::new();
+
+pub fn graph() -> &'static Graph {
+    GRAPH.get_or_init(build_graph)
+}
+
+impl Graph {
+    pub fn resolve_canonical(&self, parts: &UrlParts) -> Option<String> {
+        let mut query = parts.query.clone();
+        strip_tracking_query(&mut query);
+        let mut ctx = Context {
+            vars: HashMap::new(),
+            query,
+        };
+
+        if let Some(node_id) = self.traverse(parts, &mut ctx) {
+            if let Some(canon) = (self.nodes.get(node_id)?.canonical)(&ctx) {
+                return Some(canon);
+            }
+        }
+        Some(generic_canonical(parts))
+    }
+
+    pub fn breadcrumbs(&self, parts: &UrlParts) -> Vec<String> {
+        let mut query = parts.query.clone();
+        strip_tracking_query(&mut query);
+        let mut ctx = Context {
+            vars: HashMap::new(),
+            query,
+        };
+
+        if let Some(mut node_id) = self.traverse(parts, &mut ctx) {
+            let mut paths = Vec::new();
+            loop {
+                let node = match self.nodes.get(node_id) {
+                    Some(n) => n,
+                    None => break,
+                };
+                if let Some(url) = (node.canonical)(&ctx) {
+                    if paths.last() != Some(&url) {
+                        paths.push(url);
+                    }
+                }
+                match node.parent {
+                    Some(p) => node_id = p,
+                    None => break,
+                }
+            }
+            paths.reverse();
+            if !paths.is_empty() {
+                return paths;
+            }
+        }
+        generic_breadcrumbs(parts)
+    }
+
+    fn traverse(&self, parts: &UrlParts, ctx: &mut Context) -> Option<&'static str> {
+        let host = parts.match_host();
+        let mut node_id = match host.as_str() {
+            "reddit.com" => "reddit_root",
+            "youtube.com" => "youtube_root",
+            "youtu.be" => "youtu_be_entry",
+            _ => return None,
+        };
+
+        let segs: Vec<&str> = parts.path_segments.iter().map(String::as_str).collect();
+        let mut i = 0;
+        while i < segs.len() {
+            let seg = segs[i];
+            match self.follow_edge(node_id, seg, ctx) {
+                Ok(next) => {
+                    node_id = next;
+                    i += 1;
+                }
+                Err(()) => {
+                    if self.try_absorb(node_id, seg) {
+                        i += 1;
+                        continue;
+                    }
+                    return None;
+                }
+            }
+        }
+        Some(node_id)
+    }
+
+    fn follow_edge(
+        &self,
+        node_id: &'static str,
+        seg: &str,
+        ctx: &mut Context,
+    ) -> Result<&'static str, ()> {
+        let node = self.nodes.get(node_id).ok_or(())?;
+        for edge in &node.edges {
+            match edge.pattern {
+                EdgePattern::Literal(lit) if lit == seg => return Ok(edge.target),
+                EdgePattern::Variable(name) => {
+                    ctx.vars.insert(name.to_string(), seg.to_string());
+                    return Ok(edge.target);
+                }
+                EdgePattern::AbsorbAny
+                | EdgePattern::AbsorbIf(_)
+                | EdgePattern::Literal(_)
+                | EdgePattern::Variable(_) => {}
+            }
+        }
+        Err(())
+    }
+
+    fn try_absorb(&self, node_id: &'static str, seg: &str) -> bool {
+        let node = match self.nodes.get(node_id) {
+            Some(n) => n,
+            None => return false,
+        };
+        for edge in &node.edges {
+            match edge.pattern {
+                EdgePattern::AbsorbAny => return true,
+                EdgePattern::AbsorbIf(cond) if cond(seg) => return true,
+                EdgePattern::AbsorbIf(_) | EdgePattern::Literal(_) | EdgePattern::Variable(_) => {}
+            }
+        }
+        false
+    }
+
+    /// Test hook: terminal graph node and captured context after traversal.
+    #[cfg(test)]
+    pub fn traverse_terminal(&self, parts: &UrlParts) -> Option<(&'static str, Context)> {
+        let mut query = parts.query.clone();
+        strip_tracking_query(&mut query);
+        let mut ctx = Context {
+            vars: HashMap::new(),
+            query,
+        };
+        let node = self.traverse(parts, &mut ctx)?;
+        Some((node, ctx))
+    }
+}
+
+fn is_reddit_listing_suffix(seg: &str) -> bool {
+    matches!(seg, "hot" | "top" | "new" | "rising" | "controversial")
+}
+
+/// Percent-encode a path or query fragment so `&`, `?`, etc. cannot break URL structure.
+fn enc(s: &str) -> String {
+    urlencoding::encode(s).into_owned()
+}
+
+// --- Canonical formatters ---
+
+fn canon_reddit_root(_: &Context) -> Option<String> {
+    Some("https://reddit.com".to_string())
+}
+
+fn canon_reddit_r_hub(_: &Context) -> Option<String> {
+    Some("https://reddit.com/r".to_string())
+}
+
+fn canon_reddit_subreddit(ctx: &Context) -> Option<String> {
+    let sub = ctx.vars.get("subreddit")?;
+    Some(format!(
+        "https://reddit.com/r/{}",
+        enc(&sub.to_ascii_lowercase())
+    ))
+}
+
+fn canon_reddit_post(ctx: &Context) -> Option<String> {
+    let sub = ctx.vars.get("subreddit")?.to_ascii_lowercase();
+    let id = ctx.vars.get("post_id")?;
+    Some(format!(
+        "https://reddit.com/r/{}/comments/{}",
+        enc(&sub),
+        enc(id)
+    ))
+}
+
+fn canon_youtube_root(_: &Context) -> Option<String> {
+    Some("https://youtube.com".to_string())
+}
+
+fn canon_youtube_watch(ctx: &Context) -> Option<String> {
+    let v = ctx
+        .query
+        .get("v")
+        .or_else(|| ctx.vars.get("video_id"))?;
+    Some(format!("https://youtube.com/watch?v={}", enc(v)))
+}
+
+fn canon_youtu_be(ctx: &Context) -> Option<String> {
+    let v = ctx.vars.get("vid_id")?;
+    Some(format!("https://youtube.com/watch?v={}", enc(v)))
+}
+
+pub fn build_graph() -> Graph {
+    GraphBuilder::new()
+        .node("reddit_root")
+        .canonical(canon_reddit_root)
+        .edge(EdgePattern::Literal("r"), "reddit_r_hub")
+        .node("reddit_r_hub")
+        .parent("reddit_root")
+        .canonical(canon_reddit_r_hub)
+        .edge(EdgePattern::Variable("subreddit"), "reddit_subreddit")
+        .node("reddit_subreddit")
+        .parent("reddit_r_hub")
+        .canonical(canon_reddit_subreddit)
+        .edge(
+            EdgePattern::AbsorbIf(is_reddit_listing_suffix),
+            "reddit_subreddit",
+        )
+        .edge(EdgePattern::Literal("comments"), "reddit_comments_gate")
+        .node("reddit_comments_gate")
+        .parent("reddit_subreddit")
+        .canonical(canon_reddit_subreddit)
+        .edge(EdgePattern::Variable("post_id"), "reddit_post")
+        .node("reddit_post")
+        .parent("reddit_subreddit")
+        .canonical(canon_reddit_post)
+        .edge(EdgePattern::AbsorbAny, "reddit_post")
+        .node("youtube_root")
+        .canonical(canon_youtube_root)
+        .edge(EdgePattern::Literal("watch"), "youtube_watch")
+        .edge(EdgePattern::Literal("shorts"), "youtube_shorts_gate")
+        .node("youtube_watch")
+        .parent("youtube_root")
+        .canonical(canon_youtube_watch)
+        .node("youtube_shorts_gate")
+        .parent("youtube_root")
+        .canonical(canon_youtube_root)
+        .edge(EdgePattern::Variable("video_id"), "youtube_watch")
+        .node("youtu_be_entry")
+        .canonical(canon_youtube_root)
+        .edge(EdgePattern::Variable("vid_id"), "youtu_be_video")
+        .node("youtu_be_video")
+        .parent("youtube_root")
+        .canonical(canon_youtu_be)
+        .build()
+}
+
+// --- Generic internet fallback ---
+
+pub fn generic_canonical(parts: &UrlParts) -> String {
+    let host = normalize_match_host(&parts.host);
+    let path_segments: Vec<String> = parts.path_segments.clone();
+    let mut query = parts.query.clone();
+    strip_tracking_query(&mut query);
+
+    let mut url = if path_segments.is_empty() {
+        Url::parse(&format!("https://{host}"))
+            .unwrap_or_else(|_| Url::parse("https://invalid").unwrap())
+    } else {
+        let path = format!("/{}", path_segments.join("/"));
+        Url::parse(&format!("https://{host}{path}"))
+            .unwrap_or_else(|_| Url::parse("https://invalid").unwrap())
+    };
+
+    if !query.is_empty() {
+        let mut pairs: Vec<_> = query.iter().collect();
+        pairs.sort_by(|a, b| a.0.cmp(b.0));
+        url.query_pairs_mut().clear();
+        for (k, v) in pairs {
+            url.query_pairs_mut().append_pair(k, v);
+        }
+    }
+
+    let mut s = url.to_string();
+    if path_segments.is_empty() {
+        s = s.trim_end_matches('/').to_string();
+    }
+    s
+}
+
+pub fn generic_breadcrumbs(parts: &UrlParts) -> Vec<String> {
+    let host = normalize_match_host(&parts.host);
+    let n = parts.path_segments.len();
+    let mut out = Vec::new();
+
+    let base = generic_canonical(&UrlParts {
+        scheme: "https".to_string(),
+        host: host.clone(),
+        path_segments: vec![],
+        query: HashMap::new(),
+    });
+    out.push(base);
+
+    for i in 0..n {
+        let segs: Vec<String> = parts.path_segments[..=i].to_vec();
+        let url = generic_canonical(&UrlParts {
+            scheme: "https".to_string(),
+            host: host.clone(),
+            path_segments: segs,
+            query: HashMap::new(),
+        });
+        if out.last() != Some(&url) {
+            out.push(url);
+        }
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::url_rules::parse::test_parts;
+
+    fn g() -> &'static Graph {
+        graph()
+    }
+
+    fn canon(parts: &UrlParts) -> String {
+        g().resolve_canonical(parts).unwrap()
+    }
+
+    fn crumbs(parts: &UrlParts) -> Vec<String> {
+        g().breadcrumbs(parts)
+    }
+
+    fn terminal(parts: &UrlParts) -> Option<&'static str> {
+        g().traverse_terminal(parts).map(|(n, _)| n)
+    }
+
+    fn vars(parts: &UrlParts) -> HashMap<String, String> {
+        g().traverse_terminal(parts)
+            .map(|(_, c)| c.vars)
+            .unwrap_or_default()
+    }
+
+    #[test]
+    fn youtu_be_malicious_segment_encoded_not_injected() {
+        let p = test_parts("youtu.be", &["abc&t=1"], &[]);
+        assert_eq!(canon(&p), "https://youtube.com/watch?v=abc%26t%3D1");
+        assert!(!canon(&p).contains("abc&t=1"));
+    }
+
+    #[test]
+    fn youtube_query_v_encoded() {
+        let p = test_parts("youtube.com", &["watch"], &[("v", "a&b=c")]);
+        assert_eq!(canon(&p), "https://youtube.com/watch?v=a%26b%3Dc");
+    }
+
+    #[test]
+    fn absorb_patterns_live_on_edges_not_in_engine() {
+        let g = build_graph();
+        let sub = g.nodes.get("reddit_subreddit").unwrap();
+        assert!(sub
+            .edges
+            .iter()
+            .any(|e| matches!(e.pattern, EdgePattern::AbsorbIf(_))));
+        let post = g.nodes.get("reddit_post").unwrap();
+        assert!(post
+            .edges
+            .iter()
+            .any(|e| matches!(e.pattern, EdgePattern::AbsorbAny)));
+    }
+
+    #[test]
+    fn builder_rejects_missing_parent() {
+        let result = std::panic::catch_unwind(|| {
+            GraphBuilder::new()
+                .node("orphan")
+                .parent("nonexistent_parent")
+                .build();
+        });
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn generic_canonical_forces_https_and_strips_www() {
+        let p = test_parts("www.example.com", &["blog", "post"], &[]);
+        assert_eq!(canon(&p), "https://example.com/blog/post");
+    }
+
+    #[test]
+    fn generic_canonical_sorts_query_keys() {
+        let p = test_parts("example.com", &["search"], &[("q", "rust"), ("page", "2")]);
+        assert_eq!(canon(&p), "https://example.com/search?page=2&q=rust");
+    }
+
+    #[test]
+    fn generic_canonical_strips_tracking_from_query() {
+        let p = test_parts(
+            "news.ycombinator.com",
+            &["item"],
+            &[("id", "1"), ("utm_medium", "social")],
+        );
+        assert_eq!(canon(&p), "https://news.ycombinator.com/item?id=1");
+    }
+
+    #[test]
+    fn generic_breadcrumbs_cumulative_path() {
+        let p = test_parts("paulgraham.com", &["articles", "lisp.html"], &[]);
+        assert_eq!(
+            crumbs(&p),
+            vec![
+                "https://paulgraham.com",
+                "https://paulgraham.com/articles",
+                "https://paulgraham.com/articles/lisp.html"
+            ]
+        );
+    }
+
+    #[test]
+    fn generic_breadcrumbs_domain_only() {
+        let p = test_parts("example.com", &[], &[]);
+        assert_eq!(crumbs(&p), vec!["https://example.com"]);
+    }
+
+    #[test]
+    fn unknown_host_uses_generic_not_graph() {
+        let p = test_parts("hackernews.com", &["item", "123"], &[]);
+        assert_eq!(terminal(&p), None);
+        assert_eq!(canon(&p), "https://hackernews.com/item/123");
+    }
+
+    #[test]
+    fn traverse_captures_subreddit_variable() {
+        let p = test_parts("reddit.com", &["r", "Rust"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_subreddit"));
+        assert_eq!(vars(&p).get("subreddit").map(String::as_str), Some("Rust"));
+    }
+
+    #[test]
+    fn traverse_captures_post_id() {
+        let p = test_parts("reddit.com", &["r", "aww", "comments", "abc123"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_post"));
+        assert_eq!(vars(&p).get("post_id").map(String::as_str), Some("abc123"));
+    }
+
+    #[test]
+    fn traverse_absorbs_listing_suffix_stays_on_subreddit() {
+        let p = test_parts("reddit.com", &["r", "rust", "hot"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_subreddit"));
+        assert_eq!(canon(&p), "https://reddit.com/r/rust");
+    }
+
+    #[test]
+    fn traverse_absorbs_all_listing_suffixes() {
+        for suffix in ["hot", "top", "new", "rising", "controversial"] {
+            let p = test_parts("reddit.com", &["r", "test", suffix], &[]);
+            assert_eq!(terminal(&p), Some("reddit_subreddit"), "suffix {suffix}");
+            assert_eq!(canon(&p), "https://reddit.com/r/test", "suffix {suffix}");
+        }
+    }
+
+    #[test]
+    fn traverse_absorbs_post_title_slug() {
+        let p = test_parts(
+            "reddit.com",
+            &["r", "rust", "comments", "aaa", "my_great_post_title"],
+            &[],
+        );
+        assert_eq!(terminal(&p), Some("reddit_post"));
+        assert_eq!(canon(&p), "https://reddit.com/r/rust/comments/aaa");
+    }
+
+    #[test]
+    fn traverse_unknown_segment_falls_back_to_generic() {
+        let p = test_parts("reddit.com", &["r", "rust", "wiki", "faq"], &[]);
+        assert_eq!(terminal(&p), None);
+        assert_eq!(canon(&p), "https://reddit.com/r/rust/wiki/faq");
+    }
+
+    #[test]
+    fn traverse_youtube_watch_requires_v_in_query() {
+        let p = test_parts("youtube.com", &["watch"], &[("v", "xyz")]);
+        assert_eq!(terminal(&p), Some("youtube_watch"));
+    }
+
+    #[test]
+    fn traverse_youtu_be_captures_vid_id() {
+        let p = test_parts("youtu.be", &["dQw4w9WgXcQ"], &[]);
+        assert_eq!(terminal(&p), Some("youtu_be_video"));
+        assert_eq!(vars(&p).get("vid_id").map(String::as_str), Some("dQw4w9WgXcQ"));
+    }
+
+    #[test]
+    fn traverse_shorts_sets_video_id_var() {
+        let p = test_parts("youtube.com", &["shorts", "abc99"], &[]);
+        assert_eq!(terminal(&p), Some("youtube_watch"));
+        assert_eq!(vars(&p).get("video_id").map(String::as_str), Some("abc99"));
+    }
+
+    #[test]
+    fn reddit_domain_canonical() {
+        let p = test_parts("reddit.com", &[], &[]);
+        assert_eq!(canon(&p), "https://reddit.com");
+    }
+
+    #[test]
+    fn reddit_r_hub_canonical() {
+        let p = test_parts("reddit.com", &["r"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_r_hub"));
+        assert_eq!(canon(&p), "https://reddit.com/r");
+    }
+
+    #[test]
+    fn reddit_subreddit_lowercases_name() {
+        let p = test_parts("reddit.com", &["r", "AmITheAsshole"], &[]);
+        assert_eq!(canon(&p), "https://reddit.com/r/amitheasshole");
+    }
+
+    #[test]
+    fn reddit_host_aliases_old_new_www() {
+        for host in ["old.reddit.com", "new.reddit.com", "www.reddit.com"] {
+            let p = test_parts(host, &["r", "rust"], &[]);
+            assert_eq!(canon(&p), "https://reddit.com/r/rust", "host {host}");
+        }
+    }
+
+    #[test]
+    fn reddit_post_strips_slug_and_query() {
+        let p = test_parts(
+            "old.reddit.com",
+            &["r", "Rust", "comments", "1abc", "title_slug_here"],
+            &[("sort", "new")],
+        );
+        assert_eq!(canon(&p), "https://reddit.com/r/rust/comments/1abc");
+    }
+
+    #[test]
+    fn reddit_post_multiple_slugs_absorbed() {
+        let p = test_parts(
+            "reddit.com",
+            &["r", "x", "comments", "id1", "slug1", "extra"],
+            &[],
+        );
+        assert_eq!(canon(&p), "https://reddit.com/r/x/comments/id1");
+    }
+
+    #[test]
+    fn reddit_listing_with_query_only() {
+        let p = test_parts("www.reddit.com", &["r", "programming"], &[("sort", "top")]);
+        assert_eq!(canon(&p), "https://reddit.com/r/programming");
+    }
+
+    #[test]
+    fn reddit_subreddit_breadcrumbs_include_r_hub() {
+        let p = test_parts("reddit.com", &["r", "movies"], &[]);
+        assert_eq!(
+            crumbs(&p),
+            vec![
+                "https://reddit.com",
+                "https://reddit.com/r",
+                "https://reddit.com/r/movies"
+            ]
+        );
+    }
+
+    #[test]
+    fn reddit_post_breadcrumbs_skip_comments_node() {
+        let p = test_parts("reddit.com", &["r", "aww", "comments", "1trnvdl"], &[]);
+        let c = crumbs(&p);
+        assert!(!c.iter().any(|u| u.ends_with("/comments")));
+        assert_eq!(
+            c.last().map(String::as_str),
+            Some("https://reddit.com/r/aww/comments/1trnvdl")
+        );
+        assert!(c.contains(&"https://reddit.com/r/aww".to_string()));
+    }
+
+    #[test]
+    fn reddit_post_parent_is_subreddit_not_comments() {
+        let p = test_parts("reddit.com", &["r", "aww", "comments", "1trnvdl"], &[]);
+        let c = crumbs(&p);
+        let parent = c.get(c.len() - 2).unwrap();
+        assert_eq!(parent, "https://reddit.com/r/aww");
+    }
+
+    #[test]
+    fn reddit_domain_parent_is_none_in_breadcrumb_chain() {
+        let p = test_parts("reddit.com", &[], &[]);
+        assert_eq!(crumbs(&p), vec!["https://reddit.com"]);
+    }
+
+    #[test]
+    fn youtube_watch_canonical_uses_v_only() {
+        let p = test_parts("youtube.com", &["watch"], &[("v", "abc"), ("t", "99")]);
+        assert_eq!(canon(&p), "https://youtube.com/watch?v=abc");
+    }
+
+    #[test]
+    fn youtube_query_order_independent() {
+        let a = test_parts("youtube.com", &["watch"], &[("v", "abc"), ("t", "4")]);
+        let b = test_parts("youtube.com", &["watch"], &[("t", "4"), ("v", "abc")]);
+        assert_eq!(canon(&a), canon(&b));
+    }
+
+    #[test]
+    fn youtube_host_aliases() {
+        for host in ["www.youtube.com", "m.youtube.com"] {
+            let p = test_parts(host, &["watch"], &[("v", "x")]);
+            assert_eq!(canon(&p), "https://youtube.com/watch?v=x", "host {host}");
+        }
+    }
+
+    #[test]
+    fn youtube_shorts_canonical_matches_watch() {
+        let shorts = test_parts("youtube.com", &["shorts", "vid123"], &[]);
+        let watch = test_parts("youtube.com", &["watch"], &[("v", "vid123")]);
+        assert_eq!(canon(&shorts), canon(&watch));
+        assert_eq!(canon(&shorts), "https://youtube.com/watch?v=vid123");
+    }
+
+    #[test]
+    fn youtu_be_matches_youtube_watch() {
+        let be = test_parts("youtu.be", &["dQw4w9WgXcQ"], &[]);
+        let watch = test_parts("youtube.com", &["watch"], &[("v", "dQw4w9WgXcQ")]);
+        assert_eq!(canon(&be), canon(&watch));
+    }
+
+    #[test]
+    fn youtube_breadcrumbs_domain_then_watch() {
+        let p = test_parts("youtube.com", &["watch"], &[("v", "abc")]);
+        assert_eq!(
+            crumbs(&p),
+            vec!["https://youtube.com", "https://youtube.com/watch?v=abc"]
+        );
+    }
+
+    #[test]
+    fn youtu_be_breadcrumbs_include_youtube_domain() {
+        let p = test_parts("youtu.be", &["abc"], &[]);
+        let c = crumbs(&p);
+        assert_eq!(c.first().map(String::as_str), Some("https://youtube.com"));
+        assert_eq!(
+            c.last().map(String::as_str),
+            Some("https://youtube.com/watch?v=abc")
+        );
+    }
+
+    #[test]
+    fn parsed_urls_match_hand_built_parts() {
+        let raw = "https://www.reddit.com/r/rust/comments/aaa/title/?utm=x";
+        let parsed = UrlParts::parse(raw).unwrap();
+        let hand = test_parts(
+            "www.reddit.com",
+            &["r", "rust", "comments", "aaa", "title"],
+            &[("utm", "x")],
+        );
+        assert_eq!(canon(&parsed), canon(&hand));
+    }
+
+    #[test]
+    fn equivalence_cluster_youtube_formats() {
+        let urls = [
+            "https://youtu.be/abc123",
+            "https://www.youtube.com/watch?v=abc123",
+            "https://youtube.com/watch?v=abc123&t=1",
+            "https://m.youtube.com/watch?t=1&v=abc123",
+        ];
+        let canonical: Vec<_> = urls
+            .iter()
+            .map(|u| canon(&UrlParts::parse(u).unwrap()))
+            .collect();
+        assert!(canonical.iter().all(|c| *c == "https://youtube.com/watch?v=abc123"));
+    }
+
+    #[test]
+    fn equivalence_cluster_reddit_post_formats() {
+        let urls = [
+            "https://old.reddit.com/r/Rust/comments/aaa/slug/",
+            "reddit.com/r/rust/comments/aaa/other_slug",
+            "https://reddit.com/r/RUST/comments/aaa",
+        ];
+        let canonical: Vec<_> = urls
+            .iter()
+            .map(|u| canon(&UrlParts::parse(u).unwrap()))
+            .collect();
+        assert!(
+            canonical
+                .iter()
+                .all(|c| *c == "https://reddit.com/r/rust/comments/aaa")
+        );
+    }
+
+    #[test]
+    fn graph_nodes_all_have_valid_parent_links() {
+        let g = build_graph();
+        for (id, node) in &g.nodes {
+            if let Some(parent) = node.parent {
+                assert!(g.nodes.contains_key(parent), "node {id} parent {parent}");
+            }
+        }
+    }
+
+    #[test]
+    fn graph_terminal_canonical_always_succeeds_for_reddit_paths() {
+        let cases: &[(&[&str], &str)] = &[
+            (&["r", "rust"], "https://reddit.com/r/rust"),
+            (
+                &["r", "rust", "comments", "x"],
+                "https://reddit.com/r/rust/comments/x",
+            ),
+        ];
+        for (segs, want) in cases {
+            let p = test_parts("reddit.com", segs, &[]);
+            assert_eq!(canon(&p), *want);
+        }
+    }
+
+    #[test]
+    fn breadcrumb_parent_walk_matches_parent_url_semantics() {
+        let p = test_parts("reddit.com", &["r", "aww", "comments", "id1"], &[]);
+        let c = crumbs(&p);
+        assert_eq!(c.len(), 4);
+        assert_eq!(
+            c.get(c.len() - 2).map(String::as_str),
+            Some("https://reddit.com/r/aww")
+        );
+    }
+
+    #[test]
+    fn youtube_watch_without_v_falls_back_to_generic() {
+        let p = test_parts("youtube.com", &["watch"], &[]);
+        assert_eq!(terminal(&p), Some("youtube_watch"));
+        assert_eq!(canon(&p), "https://youtube.com/watch");
+    }
+
+    #[test]
+    fn reddit_only_comments_path_stops_at_gate() {
+        let p = test_parts("reddit.com", &["r", "rust", "comments"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_comments_gate"));
+        assert_eq!(canon(&p), "https://reddit.com/r/rust");
+    }
+
+    #[test]
+    fn generic_deep_path_many_segments() {
+        let segs: Vec<&str> = (0..10)
+            .map(|i| match i {
+                0 => "a",
+                1 => "b",
+                2 => "c",
+                3 => "d",
+                4 => "e",
+                5 => "f",
+                6 => "g",
+                7 => "h",
+                8 => "i",
+                _ => "j",
+            })
+            .collect();
+        let p = test_parts("site.com", &segs, &[]);
+        assert_eq!(crumbs(&p).len(), 11);
+    }
+
+    #[test]
+    fn traverse_literal_r_required_for_subreddit() {
+        let p = test_parts("reddit.com", &["rust"], &[]);
+        assert_eq!(terminal(&p), None);
+    }
+
+    #[test]
+    fn http_scheme_upgraded_via_generic_fallback_host() {
+        let parsed = UrlParts::parse("http://example.com/page").unwrap();
+        assert_eq!(canon(&parsed), "https://example.com/page");
+    }
+
+    #[test]
+    fn each_graph_node_canonical_is_invokable() {
+        let g = build_graph();
+        let empty = Context::default();
+        for (id, node) in &g.nodes {
+            let _ = (node.canonical)(&empty);
+            let _ = id;
+        }
+    }
+
+    #[test]
+    fn reddit_double_listing_suffix_both_absorbed() {
+        let p = test_parts("reddit.com", &["r", "rust", "hot", "new"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_subreddit"));
+        assert_eq!(canon(&p), "https://reddit.com/r/rust");
+    }
+
+    #[test]
+    fn youtu_be_empty_path_stays_at_entry() {
+        let p = test_parts("youtu.be", &[], &[]);
+        assert_eq!(terminal(&p), Some("youtu_be_entry"));
+    }
+}
diff --git a/server/src/url_rules/graph_builder.rs b/server/src/url_rules/graph_builder.rs
new file mode 100644
index 0000000000000000000000000000000000000000..243204ad5ca514fff459057956080cacb5bf38e2
--- /dev/null
+++ b/server/src/url_rules/graph_builder.rs
@@ -0,0 +1,73 @@
+//! Declarative construction of the URL graph with build-time link validation.
+
+use std::collections::HashMap;
+
+use super::graph::{CanonicalFn, Edge, EdgePattern, Graph, Node};
+
+pub struct GraphBuilder {
+    nodes: HashMap<&'static str, Node>,
+    current: Option<&'static str>,
+}
+
+impl GraphBuilder {
+    pub fn new() -> Self {
+        Self {
+            nodes: HashMap::new(),
+            current: None,
+        }
+    }
+
+    pub fn node(mut self, id: &'static str) -> Self {
+        self.nodes.entry(id).or_insert_with(Node::empty);
+        self.current = Some(id);
+        self
+    }
+
+    pub fn canonical(mut self, f: CanonicalFn) -> Self {
+        let id = self.current.expect("canonical() without node()");
+        self.nodes.get_mut(id).expect("node missing").canonical = f;
+        self
+    }
+
+    pub fn parent(mut self, parent_id: &'static str) -> Self {
+        let id = self.current.expect("parent() without node()");
+        self.nodes.get_mut(id).expect("node missing").parent = Some(parent_id);
+        self
+    }
+
+    pub fn edge(mut self, pattern: EdgePattern, target: &'static str) -> Self {
+        let id = self.current.expect("edge() without node()");
+        self.nodes
+            .get_mut(id)
+            .expect("node missing")
+            .edges
+            .push(Edge { pattern, target });
+        self
+    }
+
+    pub fn build(self) -> Graph {
+        for (id, node) in &self.nodes {
+            if let Some(parent) = node.parent {
+                assert!(
+                    self.nodes.contains_key(parent),
+                    "node {id}: parent {parent} does not exist"
+                );
+            }
+            for edge in &node.edges {
+                if !matches!(
+                    edge.pattern,
+                    EdgePattern::AbsorbAny | EdgePattern::AbsorbIf(_)
+                ) {
+                    assert!(
+                        self.nodes.contains_key(edge.target),
+                        "node {id}: edge target {} does not exist",
+                        edge.target
+                    );
+                }
+            }
+        }
+        Graph {
+            nodes: self.nodes,
+        }
+    }
+}
diff --git a/server/src/url_rules/mod.rs b/server/src/url_rules/mod.rs
index 9e1445346ce77a49dd6a7e7713bf9c57aef353cc..ba4ac662acc7bd4d50ee34613eb7eb6fccbfb17b 100644
--- a/server/src/url_rules/mod.rs
+++ b/server/src/url_rules/mod.rs
@@ -1,6 +1,7 @@
 //! URL canonicalization and hierarchy via a semantic graph (DFA + generic fallback).
 
 mod graph;
+mod graph_builder;
 mod parse;
 mod registry;
 
diff --git a/server/src/url_rules/parse.rs b/server/src/url_rules/parse.rs
new file mode 100644
index 0000000000000000000000000000000000000000..19d0c82feb718817168b8b445fcbfa39cf6aa6ba
--- /dev/null
+++ b/server/src/url_rules/parse.rs
@@ -0,0 +1,169 @@
+//! Parse raw strings into host, path segments, and query (order-independent).
+
+use std::collections::HashMap;
+
+use url::Url;
+
+#[derive(Debug, Clone)]
+pub struct UrlParts {
+    pub scheme: String,
+    pub host: String,
+    pub path_segments: Vec<String>,
+    pub query: HashMap<String, String>,
+}
+
+impl UrlParts {
+    pub fn parse(raw: &str) -> Option<Self> {
+        let trimmed = raw.trim();
+        if trimmed.is_empty() {
+            return None;
+        }
+
+        let with_scheme = if trimmed.contains("://") {
+            trimmed.to_string()
+        } else if trimmed.starts_with("r/") || trimmed.starts_with("/r/") {
+            let rest = trimmed.trim_start_matches('/').trim_start_matches("r/");
+            format!("https://reddit.com/r/{rest}")
+        } else if trimmed.contains('.') && !trimmed.starts_with('/') {
+            format!("https://{trimmed}")
+        } else {
+            trimmed.to_string()
+        };
+
+        let url = Url::parse(&with_scheme).ok()?;
+        let host = url.host_str()?.to_string();
+        let path_segments: Vec<String> = url
+            .path_segments()
+            .map(|segs| segs.filter(|s| !s.is_empty()).map(str::to_string).collect())
+            .unwrap_or_default();
+
+        let mut query = HashMap::new();
+        for (k, v) in url.query_pairs() {
+            query.insert(k.into_owned(), v.into_owned());
+        }
+
+        Some(Self {
+            scheme: url.scheme().to_string(),
+            path_segments,
+            query,
+            host,
+        })
+    }
+
+    /// Host normalized for graph entry matching (lowercase, aliases).
+    pub fn match_host(&self) -> String {
+        normalize_match_host(&self.host)
+    }
+}
+
+pub fn normalize_match_host(host: &str) -> String {
+    let h = host
+        .strip_prefix("www.")
+        .unwrap_or(host)
+        .to_ascii_lowercase();
+    match h.as_str() {
+        "old.reddit.com" | "new.reddit.com" => "reddit.com".to_string(),
+        "m.youtube.com" => "youtube.com".to_string(),
+        _ => h,
+    }
+}
+
+pub fn strip_tracking_query(query: &mut HashMap<String, String>) {
+    query.retain(|k, _| {
+        let lower = k.to_ascii_lowercase();
+        !(lower.starts_with("utm_")
+            || matches!(
+                lower.as_str(),
+                "fbclid" | "gclid" | "ref" | "ref_src" | "ref_source" | "mc_cid" | "mc_eid"
+            ))
+    });
+}
+
+#[cfg(test)]
+pub(crate) fn test_parts(host: &str, segs: &[&str], query: &[(&str, &str)]) -> UrlParts {
+    UrlParts {
+        scheme: "https".to_string(),
+        host: host.to_string(),
+        path_segments: segs.iter().map(|s| (*s).to_string()).collect(),
+        query: query
+            .iter()
+            .map(|(k, v)| (k.to_string(), v.to_string()))
+            .collect(),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_full_url_splits_host_path_query() {
+        let p = UrlParts::parse("https://www.youtube.com/watch?v=abc&t=4").unwrap();
+        assert_eq!(p.host, "www.youtube.com");
+        assert_eq!(p.path_segments, vec!["watch"]);
+        assert_eq!(p.query.get("v").map(String::as_str), Some("abc"));
+        assert_eq!(p.query.get("t").map(String::as_str), Some("4"));
+    }
+
+    #[test]
+    fn parse_r_shortcut_expands_to_reddit() {
+        let p = UrlParts::parse("r/rust").unwrap();
+        assert_eq!(p.match_host(), "reddit.com");
+        assert_eq!(p.path_segments, vec!["r", "rust"]);
+    }
+
+    #[test]
+    fn parse_slash_r_shortcut() {
+        let p = UrlParts::parse("/r/aww").unwrap();
+        assert_eq!(p.path_segments, vec!["r", "aww"]);
+    }
+
+    #[test]
+    fn parse_schemeless_host_path() {
+        let p = UrlParts::parse("reddit.com/r/rust/comments/aaa/slug").unwrap();
+        assert_eq!(p.match_host(), "reddit.com");
+        assert_eq!(
+            p.path_segments,
+            vec!["r", "rust", "comments", "aaa", "slug"]
+        );
+    }
+
+    #[test]
+    fn parse_empty_returns_none() {
+        assert!(UrlParts::parse("").is_none());
+        assert!(UrlParts::parse("   ").is_none());
+    }
+
+    #[test]
+    fn normalize_match_host_reddit_aliases() {
+        assert_eq!(normalize_match_host("old.reddit.com"), "reddit.com");
+        assert_eq!(normalize_match_host("NEW.reddit.com"), "reddit.com");
+        assert_eq!(normalize_match_host("www.reddit.com"), "reddit.com");
+    }
+
+    #[test]
+    fn normalize_match_host_youtube_aliases() {
+        assert_eq!(normalize_match_host("m.youtube.com"), "youtube.com");
+        assert_eq!(normalize_match_host("www.youtube.com"), "youtube.com");
+    }
+
+    #[test]
+    fn strip_tracking_query_removes_known_params() {
+        let mut q = HashMap::from([
+            ("v".into(), "1".into()),
+            ("utm_source".into(), "x".into()),
+            ("fbclid".into(), "y".into()),
+            ("ref".into(), "z".into()),
+        ]);
+        strip_tracking_query(&mut q);
+        assert_eq!(q.len(), 1);
+        assert_eq!(q.get("v").map(String::as_str), Some("1"));
+    }
+
+    #[test]
+    fn strip_tracking_query_utm_prefix() {
+        let mut q = HashMap::from([("utm_campaign".into(), "email".into())]);
+        strip_tracking_query(&mut q);
+        assert!(q.is_empty());
+    }
+}
diff --git a/server/src/url_rules/registry_tests.rs b/server/src/url_rules/registry_tests.rs
new file mode 100644
index 0000000000000000000000000000000000000000..7b76b550f808f590e011469fdae02adf603b43d2
--- /dev/null
+++ b/server/src/url_rules/registry_tests.rs
@@ -0,0 +1,195 @@
+//! End-to-end tests for the public registry API (`canonicalize_raw`, breadcrumbs, parent).
+
+use super::registry::{
+    canonicalize_raw, looks_like_url, navigable_breadcrumbs, parent_url, resolve_id,
+};
+
+fn canon(raw: &str) -> String {
+    canonicalize_raw(raw).unwrap().canonical
+}
+
+#[test]
+fn looks_like_url_positive_cases() {
+    for raw in [
+        "https://reddit.com/r/rust",
+        "r/rust",
+        "/r/aww",
+        "reddit.com/r/x",
+        "www.example.com/path",
+        "youtu.be/abc",
+    ] {
+        assert!(looks_like_url(raw), "{raw}");
+    }
+}
+
+#[test]
+fn looks_like_url_negative_cases() {
+    for raw in ["alpha", "beta", "", "hello world", "no-dots"] {
+        assert!(!looks_like_url(raw), "{raw}");
+    }
+}
+
+#[test]
+fn resolve_id_matches_canonicalize_raw() {
+    let raw = "https://youtu.be/xyz";
+    assert_eq!(
+        resolve_id(raw).as_deref(),
+        Some(canon(raw).as_str())
+    );
+}
+
+#[test]
+fn canonicalize_empty_returns_none() {
+    assert!(canonicalize_raw("").is_none());
+}
+
+#[test]
+fn alias_when_slug_stripped() {
+    let r = canonicalize_raw(
+        "https://reddit.com/r/rust/comments/aaa/very_long_title_slug",
+    )
+    .unwrap();
+    assert_eq!(r.canonical, "https://reddit.com/r/rust/comments/aaa");
+    assert!(r.alias_of.is_some());
+}
+
+#[test]
+fn alias_none_when_already_canonical() {
+    let raw = "https://reddit.com/r/rust";
+    let r = canonicalize_raw(raw).unwrap();
+    assert_eq!(r.canonical, raw);
+    assert!(r.alias_of.is_none());
+}
+
+#[test]
+fn parent_url_subreddit_under_r_hub() {
+    assert_eq!(
+        parent_url("https://reddit.com/r/movies").as_deref(),
+        Some("https://reddit.com/r")
+    );
+}
+
+#[test]
+fn parent_url_domain_has_none() {
+    assert_eq!(parent_url("https://reddit.com").as_deref(), None);
+}
+
+#[test]
+fn parent_url_generic_site() {
+    assert_eq!(
+        parent_url("https://example.com/a/b").as_deref(),
+        Some("https://example.com/a")
+    );
+}
+
+#[test]
+fn breadcrumbs_from_canonical_string_roundtrip() {
+    let id = "https://reddit.com/r/golang/comments/abc123";
+    let crumbs = navigable_breadcrumbs(id);
+    assert_eq!(crumbs.last().map(String::as_str), Some(id));
+}
+
+// --- Table: Reddit raw URLs → canonical ---
+
+#[test]
+fn reddit_canonical_matrix() {
+    let cases: &[(&str, &str)] = &[
+        ("r/rust", "https://reddit.com/r/rust"),
+        ("/r/aww", "https://reddit.com/r/aww"),
+        ("https://reddit.com/r/rust", "https://reddit.com/r/rust"),
+        (
+            "https://www.reddit.com/r/programming/new",
+            "https://reddit.com/r/programming",
+        ),
+        (
+            "https://old.reddit.com/r/test/comments/xyz/slug/",
+            "https://reddit.com/r/test/comments/xyz",
+        ),
+        (
+            "reddit.com/r/Movies/comments/abc/Title_Case_Slug",
+            "https://reddit.com/r/movies/comments/abc",
+        ),
+    ];
+    for (raw, want) in cases {
+        assert_eq!(canon(raw), *want, "raw={raw}");
+    }
+}
+
+// --- Table: YouTube raw URLs → canonical ---
+
+#[test]
+fn youtube_canonical_matrix() {
+    let cases: &[(&str, &str)] = &[
+        (
+            "https://youtube.com/watch?v=abc",
+            "https://youtube.com/watch?v=abc",
+        ),
+        (
+            "https://www.youtube.com/watch?v=abc&t=1&feature=share",
+            "https://youtube.com/watch?v=abc",
+        ),
+        ("https://youtu.be/abc", "https://youtube.com/watch?v=abc"),
+        (
+            "https://youtube.com/shorts/abc",
+            "https://youtube.com/watch?v=abc",
+        ),
+    ];
+    for (raw, want) in cases {
+        assert_eq!(canon(raw), *want, "raw={raw}");
+    }
+}
+
+// --- Table: generic sites ---
+
+#[test]
+fn generic_canonical_matrix() {
+    let cases: &[(&str, &str)] = &[
+        (
+            "https://news.ycombinator.com/item?id=38472",
+            "https://news.ycombinator.com/item?id=38472",
+        ),
+        (
+            "https://www.github.com/rust-lang/rust/issues/1?utm_source=x",
+            "https://github.com/rust-lang/rust/issues/1",
+        ),
+        ("https://example.com", "https://example.com"),
+    ];
+    for (raw, want) in cases {
+        assert_eq!(canon(raw), *want, "raw={raw}");
+    }
+}
+
+// --- Phantom /comments/ regression (sorter2-specific) ---
+
+#[test]
+fn phantom_comments_not_in_breadcrumbs_for_post() {
+    let crumbs = navigable_breadcrumbs("https://reddit.com/r/rust/comments/aaa");
+    assert!(!crumbs.iter().any(|c| c.ends_with("/comments")));
+}
+
+#[test]
+fn phantom_comments_not_sibling_of_subreddit_in_breadcrumb_chain() {
+    let crumbs = navigable_breadcrumbs("https://reddit.com/r/rust/comments/aaa");
+    let subs: Vec<_> = crumbs
+        .iter()
+        .filter(|c| c.contains("/r/rust") && !c.contains("/comments/"))
+        .collect();
+    assert_eq!(subs, vec!["https://reddit.com/r/rust"]);
+}
+
+// --- Distinct items must stay distinct ---
+
+#[test]
+fn different_posts_different_canonical() {
+    let a = canon("https://reddit.com/r/rust/comments/aaa");
+    let b = canon("https://reddit.com/r/rust/comments/bbb");
+    assert_ne!(a, b);
+}
+
+#[test]
+fn different_subreddits_different_canonical() {
+    assert_ne!(
+        canon("https://reddit.com/r/rust"),
+        canon("https://reddit.com/r/golang")
+    );
+}