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:
[239c074b] url schema stuff

Side B — unified diff (full patch):
diff --git a/AGENTS.md b/AGENTS.md
index 426a88e7c1da54fe0a28c5c76fa4e1f1bc117fcf..e60b9ba6012593361ef10e8fdd9439cd9932e09b 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -58,3 +58,4 @@ Use **tmux** for `cargo run --package sorter2-server` (dev server). Rebuild afte
 
 - First `cargo test` / `cargo build --release` is slow; Clojure smoke test always does a release build.
 - `legacy/` and `ideas/` are not part of the workspace build.
+- **ItemId** for web URLs is a canonical full URL (`https://reddit.com/r/rust`). Rules live in [`server/src/url_rules/`](server/src/url_rules/) (composable Rust, not a config DSL). After changing canonicalization rules, rebuild the projection: `cargo run --package sorter2-server -- replay-index`.
diff --git a/Cargo.lock b/Cargo.lock
index 0dd4fce5fb6400ae153cca4e3dbf5a5158e6d8b4..49a908ef935c430dbe63c6a28d8a24e38b489486 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1951,6 +1951,7 @@ dependencies = [
  "tower-http 0.5.2",
  "tracing",
  "tracing-subscriber",
+ "url",
  "urlencoding",
 ]
 
diff --git a/REPLAY.sh b/REPLAY.sh
new file mode 100755
index 0000000000000000000000000000000000000000..f2dbd8aea60c02d2feef74805f7ef5c2b7022537
--- /dev/null
+++ b/REPLAY.sh
@@ -0,0 +1,2 @@
+cargo run --package sorter2-server -- replay-index
+
diff --git a/server/Cargo.toml b/server/Cargo.toml
index 27f552c20b97ef28cdde4cb6b1a4980375135111..ad4912791aff59fb1d3293f66ad381ae618cd60b 100644
--- a/server/Cargo.toml
+++ b/server/Cargo.toml
@@ -24,6 +24,7 @@ async-stream = "0.3"
 futures-util = { version = "0.3", default-features = false, features = ["std"] }
 rand = "0.8"
 urlencoding = "2"
+url = "2"
 durable = { path = "../durable" }
 
 [dev-dependencies]
diff --git a/server/src/entity_store.rs b/server/src/entity_store.rs
index d5d17c3676e4a8ddec998e9f5a9dbafe9c2d9d0e..d29f39aecca6f12cdcf263cf77c3654eb4ee6cfa 100644
--- a/server/src/entity_store.rs
+++ b/server/src/entity_store.rs
@@ -124,7 +124,7 @@ mod tests {
     fn round_trip_payload() {
         let tmp = tempfile::tempdir().unwrap();
         let store = EntityStore::open(tmp.path()).unwrap();
-        let id = ItemId::parse("reddit.com/r/rust").unwrap();
+        let id = ItemId::from_url("https://reddit.com/r/rust").unwrap();
         let payload = json!({"kind": "t5", "data": {"display_name": "rust"}});
 
         store.put(&id, &payload).unwrap();
diff --git a/server/src/event_log.rs b/server/src/event_log.rs
index 36f5b406084065b608735987cdb483c236e03081..2c9290b6fdbf2c2ad1c0f1ffd7374b2d9cc97f36 100644
--- a/server/src/event_log.rs
+++ b/server/src/event_log.rs
@@ -199,7 +199,7 @@ mod tests {
         log.append(&sample_record(
             1,
             Event::NodeEnsured {
-                id: "reddit.com/r/rust".into(),
+                id: "https://reddit.com/r/rust".into(),
             },
         ))
         .await
@@ -237,7 +237,7 @@ mod tests {
         let path = tmp.path().join("events.jsonl");
         let log = EventLog::new(&path);
         let event = Event::NodeEnsured {
-            id: "reddit.com/r/rust".into(),
+            id: "https://reddit.com/r/rust".into(),
         };
         log.append(&sample_record(1, event)).await.unwrap();
 
@@ -255,7 +255,7 @@ mod tests {
         let path = tmp.path().join("events.jsonl");
         std::fs::write(
             &path,
-            r#"{"type":"node_ensured","id":"reddit.com/r/rust"}
+            r#"{"type":"node_ensured","id":"https://reddit.com/r/rust"}
 {"schema":1,"seq":1,"ts":1,"event":{"type":"vote_recorded","ts":1,"a":"a","b":"b","ratio_left":2,"ratio_right":1,"scope":""}}
 "#,
         )
@@ -295,7 +295,7 @@ mod tests {
         log.append(&sample_record(
             1,
             Event::NodeEnsured {
-                id: "reddit.com/r/rust".into(),
+                id: "https://reddit.com/r/rust".into(),
             },
         ))
         .await
@@ -303,7 +303,7 @@ mod tests {
         log.append(&sample_record(
             3,
             Event::NodeEnsured {
-                id: "reddit.com/r/python".into(),
+                id: "https://reddit.com/r/python".into(),
             },
         ))
         .await
diff --git a/server/src/journal.rs b/server/src/journal.rs
index 521a108019de1ea870d14c4fafbfe572c20ce0de..50bc89f976edb82b7b0e49e954a8eccbbe82bf87 100644
--- a/server/src/journal.rs
+++ b/server/src/journal.rs
@@ -141,10 +141,10 @@ mod tests {
         let j2 = journal.clone();
         let (r1, r2) = tokio::join!(
             j1.append(Event::NodeEnsured {
-                id: "reddit.com/r/rust".into(),
+                id: "https://reddit.com/r/rust".into(),
             }),
             j2.append(Event::NodeEnsured {
-                id: "reddit.com/r/python".into(),
+                id: "https://reddit.com/r/python".into(),
             }),
         );
         r1.unwrap();
@@ -153,10 +153,10 @@ mod tests {
         assert_eq!(projection_store.last_applied_event_count().unwrap(), 2);
         let tree = projection_store.load_tree().unwrap();
         assert!(tree
-            .get(&ItemId::parse("reddit.com/r/rust").unwrap())
+            .get(&ItemId::parse("https://reddit.com/r/rust").unwrap())
             .is_some());
         assert!(tree
-            .get(&ItemId::parse("reddit.com/r/python").unwrap())
+            .get(&ItemId::parse("https://reddit.com/r/python").unwrap())
             .is_some());
     }
 
@@ -170,7 +170,7 @@ mod tests {
                 1,
                 1,
                 Event::NodeEnsured {
-                    id: "reddit.com/r/rust".into(),
+                    id: "https://reddit.com/r/rust".into(),
                 },
             ))
             .await
@@ -186,7 +186,7 @@ mod tests {
                 1,
                 1,
                 Event::NodeEnsured {
-                    id: "reddit.com/r/rust".into(),
+                    id: "https://reddit.com/r/rust".into(),
                 },
             )],
         )
@@ -202,7 +202,7 @@ mod tests {
         );
         journal
             .append(Event::NodeEnsured {
-                id: "reddit.com/r/python".into(),
+                id: "https://reddit.com/r/python".into(),
             })
             .await
             .unwrap();
@@ -227,13 +227,13 @@ mod tests {
         journal
             .append_many(vec![
                 Event::NodeEnsured {
-                    id: "reddit.com/r/rust".into(),
+                    id: "https://reddit.com/r/rust".into(),
                 },
                 Event::NodeEnsured {
-                    id: "reddit.com/r/python".into(),
+                    id: "https://reddit.com/r/python".into(),
                 },
                 Event::NodeEnsured {
-                    id: "reddit.com/r/clojure".into(),
+                    id: "https://reddit.com/r/clojure".into(),
                 },
             ])
             .await
@@ -245,7 +245,7 @@ mod tests {
         assert_eq!(projection_store.last_applied_event_count().unwrap(), 3);
         let tree = projection_store.load_tree().unwrap();
         assert!(tree
-            .get(&ItemId::parse("reddit.com/r/clojure").unwrap())
+            .get(&ItemId::parse("https://reddit.com/r/clojure").unwrap())
             .is_some());
     }
 }
diff --git a/server/src/lib.rs b/server/src/lib.rs
index 9bd5f76fd1406b9b1be4c272f4ba8647edde2678..5c02c8e704e4664453bad75d819df8a067668176 100644
--- a/server/src/lib.rs
+++ b/server/src/lib.rs
@@ -9,6 +9,7 @@ pub mod journal;
 pub mod pair;
 pub mod parser;
 pub mod path_types;
+pub mod url_rules;
 pub mod projection_apply;
 pub mod projection_store;
 pub mod ranking;
diff --git a/server/src/pair.rs b/server/src/pair.rs
index 43f780ba6ea6ce1cdc2e1f4cbb252ba8a10684b9..815a97b80e3e9f348e0937a4f147f2862018edb0 100644
--- a/server/src/pair.rs
+++ b/server/src/pair.rs
@@ -381,42 +381,42 @@ mod tests {
 
     #[test]
     fn suggest_prefers_unvoted_pair() {
-        let parent = ItemId::parse("reddit.com/r/rust").unwrap();
+        let parent = ItemId::parse("https://reddit.com/r/rust").unwrap();
         let mut tree = seed_children(
             &parent,
             &[
-                "reddit.com/r/rust/a",
-                "reddit.com/r/rust/b",
-                "reddit.com/r/rust/c",
+                "https://reddit.com/r/rust/a",
+                "https://reddit.com/r/rust/b",
+                "https://reddit.com/r/rust/c",
             ],
         );
         let vote =
-            VoteData::from_recorded(1, "reddit.com/r/rust/a", "reddit.com/r/rust/b", 2, 1).unwrap();
+            VoteData::from_recorded(1, "https://reddit.com/r/rust/a", "https://reddit.com/r/rust/b", 2, 1).unwrap();
         tree.apply_vote(&parent, vote);
         let group = tree.get(&parent).unwrap().local_ranking.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() == "reddit.com/r/rust/a" && r.as_str() == "reddit.com/r/rust/b")
-            || (l.as_str() == "reddit.com/r/rust/b" && r.as_str() == "reddit.com/r/rust/a");
+        let voted_ab = (l.as_str() == "https://reddit.com/r/rust/a" && r.as_str() == "https://reddit.com/r/rust/b")
+            || (l.as_str() == "https://reddit.com/r/rust/b" && r.as_str() == "https://reddit.com/r/rust/a");
         assert!(!voted_ab);
     }
 
     #[test]
     fn suggest_bridges_separate_components() {
-        let parent = ItemId::parse("reddit.com/r/rust").unwrap();
+        let parent = ItemId::parse("https://reddit.com/r/rust").unwrap();
         let mut tree = seed_children(
             &parent,
             &[
-                "reddit.com/r/rust/a",
-                "reddit.com/r/rust/b",
-                "reddit.com/r/rust/c",
-                "reddit.com/r/rust/d",
+                "https://reddit.com/r/rust/a",
+                "https://reddit.com/r/rust/b",
+                "https://reddit.com/r/rust/c",
+                "https://reddit.com/r/rust/d",
             ],
         );
         let ab =
-            VoteData::from_recorded(1, "reddit.com/r/rust/a", "reddit.com/r/rust/b", 2, 1).unwrap();
+            VoteData::from_recorded(1, "https://reddit.com/r/rust/a", "https://reddit.com/r/rust/b", 2, 1).unwrap();
         let cd =
-            VoteData::from_recorded(2, "reddit.com/r/rust/c", "reddit.com/r/rust/d", 2, 1).unwrap();
+            VoteData::from_recorded(2, "https://reddit.com/r/rust/c", "https://reddit.com/r/rust/d", 2, 1).unwrap();
         tree.apply_vote(&parent, ab);
         tree.apply_vote(&parent, cd);
         let group = tree.get(&parent).unwrap().local_ranking.clone();
@@ -424,37 +424,37 @@ mod tests {
         let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
         let chosen = pair_set(&pair);
         let from_ab =
-            chosen.contains("reddit.com/r/rust/a") || chosen.contains("reddit.com/r/rust/b");
+            chosen.contains("https://reddit.com/r/rust/a") || chosen.contains("https://reddit.com/r/rust/b");
         let from_cd =
-            chosen.contains("reddit.com/r/rust/c") || chosen.contains("reddit.com/r/rust/d");
+            chosen.contains("https://reddit.com/r/rust/c") || chosen.contains("https://reddit.com/r/rust/d");
         assert!(from_ab && from_cd, "expected bridge pair, got {:?}", chosen);
     }
 
     #[test]
     fn suggest_prefers_attach_over_isolate_pair_among_many_unranked() {
-        let parent = ItemId::parse("reddit.com/r/rust").unwrap();
+        let parent = ItemId::parse("https://reddit.com/r/rust").unwrap();
         let mut tree = seed_children(
             &parent,
             &[
-                "reddit.com/r/rust/a",
-                "reddit.com/r/rust/b",
-                "reddit.com/r/rust/c",
-                "reddit.com/r/rust/d",
-                "reddit.com/r/rust/e",
+                "https://reddit.com/r/rust/a",
+                "https://reddit.com/r/rust/b",
+                "https://reddit.com/r/rust/c",
+                "https://reddit.com/r/rust/d",
+                "https://reddit.com/r/rust/e",
             ],
         );
         let ab =
-            VoteData::from_recorded(1, "reddit.com/r/rust/a", "reddit.com/r/rust/b", 2, 1).unwrap();
+            VoteData::from_recorded(1, "https://reddit.com/r/rust/a", "https://reddit.com/r/rust/b", 2, 1).unwrap();
         tree.apply_vote(&parent, ab);
         let group = tree.get(&parent).unwrap().local_ranking.clone();
         let pool = children_of(&tree, &parent);
         let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
         let chosen = pair_set(&pair);
         let from_ab =
-            chosen.contains("reddit.com/r/rust/a") || chosen.contains("reddit.com/r/rust/b");
-        let from_cde = chosen.contains("reddit.com/r/rust/c")
-            || chosen.contains("reddit.com/r/rust/d")
-            || chosen.contains("reddit.com/r/rust/e");
+            chosen.contains("https://reddit.com/r/rust/a") || chosen.contains("https://reddit.com/r/rust/b");
+        let from_cde = chosen.contains("https://reddit.com/r/rust/c")
+            || chosen.contains("https://reddit.com/r/rust/d")
+            || chosen.contains("https://reddit.com/r/rust/e");
         assert!(
             from_ab && from_cde,
             "expected ranked+unranked attach, got {:?}",
@@ -464,40 +464,40 @@ mod tests {
 
     #[test]
     fn suggest_connects_isolate_to_existing_component() {
-        let parent = ItemId::parse("reddit.com/r/rust").unwrap();
+        let parent = ItemId::parse("https://reddit.com/r/rust").unwrap();
         let mut tree = seed_children(
             &parent,
             &[
-                "reddit.com/r/rust/a",
-                "reddit.com/r/rust/b",
-                "reddit.com/r/rust/c",
+                "https://reddit.com/r/rust/a",
+                "https://reddit.com/r/rust/b",
+                "https://reddit.com/r/rust/c",
             ],
         );
         let ab =
-            VoteData::from_recorded(1, "reddit.com/r/rust/a", "reddit.com/r/rust/b", 2, 1).unwrap();
+            VoteData::from_recorded(1, "https://reddit.com/r/rust/a", "https://reddit.com/r/rust/b", 2, 1).unwrap();
         tree.apply_vote(&parent, ab);
         let group = tree.get(&parent).unwrap().local_ranking.clone();
         let pool = children_of(&tree, &parent);
         let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
         let chosen = pair_set(&pair);
-        assert!(chosen.contains("reddit.com/r/rust/c"));
-        assert!(chosen.contains("reddit.com/r/rust/a") || chosen.contains("reddit.com/r/rust/b"));
+        assert!(chosen.contains("https://reddit.com/r/rust/c"));
+        assert!(chosen.contains("https://reddit.com/r/rust/a") || chosen.contains("https://reddit.com/r/rust/b"));
     }
 
     #[test]
     fn suggest_zips_adjacent_ranks_when_tree_complete() {
-        let parent = ItemId::parse("reddit.com/r/rust").unwrap();
+        let parent = ItemId::parse("https://reddit.com/r/rust").unwrap();
         let mut tree = seed_children(
             &parent,
             &[
-                "reddit.com/r/rust/a",
-                "reddit.com/r/rust/b",
-                "reddit.com/r/rust/c",
+                "https://reddit.com/r/rust/a",
+                "https://reddit.com/r/rust/b",
+                "https://reddit.com/r/rust/c",
             ],
         );
         for (a, b, l, r) in [
-            ("reddit.com/r/rust/a", "reddit.com/r/rust/b", 3, 1),
-            ("reddit.com/r/rust/a", "reddit.com/r/rust/c", 2, 1),
+            ("https://reddit.com/r/rust/a", "https://reddit.com/r/rust/b", 3, 1),
+            ("https://reddit.com/r/rust/a", "https://reddit.com/r/rust/c", 2, 1),
         ] {
             let v = VoteData::from_recorded(1, a, b, l, r).unwrap();
             tree.apply_vote(&parent, v);
@@ -506,26 +506,26 @@ mod tests {
         let pool = children_of(&tree, &parent);
         let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
         let chosen = pair_set(&pair);
-        assert!(chosen.contains("reddit.com/r/rust/b"));
-        assert!(chosen.contains("reddit.com/r/rust/c"));
+        assert!(chosen.contains("https://reddit.com/r/rust/b"));
+        assert!(chosen.contains("https://reddit.com/r/rust/c"));
     }
 
     #[test]
     fn suggest_zip_prefers_1v2_before_2v3_when_both_unvoted() {
-        let parent = ItemId::parse("reddit.com/r/rust").unwrap();
+        let parent = ItemId::parse("https://reddit.com/r/rust").unwrap();
         let mut tree = seed_children(
             &parent,
             &[
-                "reddit.com/r/rust/a",
-                "reddit.com/r/rust/b",
-                "reddit.com/r/rust/c",
-                "reddit.com/r/rust/d",
+                "https://reddit.com/r/rust/a",
+                "https://reddit.com/r/rust/b",
+                "https://reddit.com/r/rust/c",
+                "https://reddit.com/r/rust/d",
             ],
         );
         for (a, b, l, r) in [
-            ("reddit.com/r/rust/c", "reddit.com/r/rust/d", 3, 1),
-            ("reddit.com/r/rust/b", "reddit.com/r/rust/c", 2, 1),
-            ("reddit.com/r/rust/a", "reddit.com/r/rust/c", 2, 1),
+            ("https://reddit.com/r/rust/c", "https://reddit.com/r/rust/d", 3, 1),
+            ("https://reddit.com/r/rust/b", "https://reddit.com/r/rust/c", 2, 1),
+            ("https://reddit.com/r/rust/a", "https://reddit.com/r/rust/c", 2, 1),
         ] {
             let v = VoteData::from_recorded(1, a, b, l, r).unwrap();
             tree.apply_vote(&parent, v);
@@ -534,16 +534,16 @@ mod tests {
         let pool = children_of(&tree, &parent);
         let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
         let chosen = pair_set(&pair);
-        assert!(chosen.contains("reddit.com/r/rust/a"));
-        assert!(chosen.contains("reddit.com/r/rust/b"));
+        assert!(chosen.contains("https://reddit.com/r/rust/a"));
+        assert!(chosen.contains("https://reddit.com/r/rust/b"));
     }
 
     #[test]
     fn resolve_pair_picks_from_pool() {
-        let parent = ItemId::parse("reddit.com/r/rust").unwrap();
-        let tree = seed_children(&parent, &["reddit.com/r/rust/a", "reddit.com/r/rust/b"]);
+        let parent = ItemId::parse("https://reddit.com/r/rust").unwrap();
+        let tree = seed_children(&parent, &["https://reddit.com/r/rust/a", "https://reddit.com/r/rust/b"]);
         let pair = resolve_pair(&tree, &parent, None, None).unwrap();
-        let pool: HashSet<_> = ["reddit.com/r/rust/a", "reddit.com/r/rust/b"]
+        let pool: HashSet<_> = ["https://reddit.com/r/rust/a", "https://reddit.com/r/rust/b"]
             .into_iter()
             .collect();
         assert!(pool.contains(pair.0.as_str()));
diff --git a/server/src/parser.rs b/server/src/parser.rs
index 9df2dcc9313f7fe250ce3b6aa167f6ec5d57951f..b2a963dd6cab415576c8d3a9a241966758565bb8 100644
--- a/server/src/parser.rs
+++ b/server/src/parser.rs
@@ -23,7 +23,7 @@ mod tests {
     fn parses_short_path() {
         assert_eq!(
             parse_reddit_url("r/rust").unwrap().as_str(),
-            "reddit.com/r/rust"
+            "https://reddit.com/r/rust"
         );
     }
 
@@ -33,7 +33,7 @@ mod tests {
             parse_reddit_url("https://www.reddit.com/r/programming/hot")
                 .unwrap()
                 .as_str(),
-            "reddit.com/r/programming"
+            "https://reddit.com/r/programming"
         );
     }
 
@@ -43,7 +43,10 @@ mod tests {
             "https://old.reddit.com/r/AmItheAsshole/comments/1trnvdl/aita_for_cancelling/",
         )
         .unwrap();
-        assert_eq!(id.as_str(), "reddit.com/r/amitheasshole/comments/1trnvdl");
+        assert_eq!(
+            id.as_str(),
+            "https://reddit.com/r/amitheasshole/comments/1trnvdl"
+        );
     }
 
     #[test]
diff --git a/server/src/path_types.rs b/server/src/path_types.rs
index fafd924452f6fd85e7a5b27ed2653a19581e6e56..71ffc01f35c5589686ff05dae3b5610fa01f30ce 100644
--- a/server/src/path_types.rs
+++ b/server/src/path_types.rs
@@ -1,13 +1,14 @@
 use serde::{Deserialize, Serialize};
 use std::fmt;
 
-/// Canonical hierarchical identity for any URL/path in the fractal tree.
+use crate::url_rules::{looks_like_url, navigable_breadcrumbs, parent_url, resolve_canonical};
+
+/// Canonical identity: a real URL (with scheme) or an opaque non-URL key.
 #[derive(Debug, Clone, Hash, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize, Default)]
 pub struct ItemId(String);
 
 impl ItemId {
-    /// Parse an already-canonical path (no URL normalization). Empty string is invalid here;
-    /// use [`Self::root`] for the tree root.
+    /// Parse an already-canonical id (no normalization). Empty string is invalid; use [`Self::root`].
     pub fn parse(s: &str) -> Option<Self> {
         let t = s.trim();
         if t.is_empty() {
@@ -16,12 +17,12 @@ impl ItemId {
         Some(Self(t.to_string()))
     }
 
-    /// Build an opaque item key (legacy demo votes, non-URL items).
+    /// Build an opaque item key (demo votes, non-URL items).
     pub fn opaque(s: impl Into<String>) -> Self {
         Self(s.into())
     }
 
-    /// Root of the internet tree (empty path).
+    /// Root of the internet tree.
     pub fn root() -> Self {
         Self(String::new())
     }
@@ -34,23 +35,18 @@ impl ItemId {
         &self.0
     }
 
-    /// Creates a canonical ID from a raw URL or path. Normalizes domains and
-    /// trims tracking query params.
+    /// Canonical URL from a raw pasted or fetched URL.
     pub fn from_url(raw_url: &str) -> Option<Self> {
-        Self::canonicalize(raw_url).map(Self)
+        resolve_canonical(raw_url).map(Self)
     }
 
-    /// Normalize strings from forms, events, and Reddit imports into the same
-    /// stored id shape (e.g. drop post title slug after comment id).
+    /// Normalize strings from forms, events, and imports into canonical identity.
     pub fn from_storage(s: &str) -> Option<Self> {
         let t = s.trim();
         if t.is_empty() {
             return None;
         }
-        if t.contains("://") || t.starts_with("r/") {
-            return Self::from_url(t).or_else(|| Self::parse(t));
-        }
-        if t.starts_with("reddit.com/") && t.contains("/comments/") {
+        if looks_like_url(t) {
             return Self::from_url(t).or_else(|| Self::parse(t));
         }
         Self::parse(t).or_else(|| Self::from_url(t))
@@ -62,35 +58,52 @@ impl ItemId {
         if s.is_empty() {
             return Self::root();
         }
-        Self(format!("reddit.com/r/{s}"))
+        if looks_like_url(s) || s.contains('/') {
+            Self::from_storage(s).unwrap_or_else(|| Self::opaque(s))
+        } else {
+            Self(format!("https://reddit.com/r/{s}"))
+        }
     }
 
-    /// Extract the parent, e.g. `reddit.com/r/aww/comments/1trnvdl` →
-    /// `reddit.com/r/aww`.
+    /// Immediate parent scope in the tree.
     pub fn parent(&self) -> Option<Self> {
-        if self.0.is_empty() {
+        if self.is_root() {
             return None;
         }
-
+        if looks_like_url(self.0.as_str()) {
+            return parent_url(self.0.as_str()).map(Self);
+        }
         let parts: Vec<&str> = self.0.trim_end_matches('/').split('/').collect();
         if parts.len() <= 1 {
             return None;
         }
-
-        if self.0.contains("/comments/") {
-            return Some(Self(parts[..parts.len().saturating_sub(2)].join("/")));
-        }
-
         Some(Self(parts[..parts.len() - 1].join("/")))
     }
 
     pub fn segments(&self) -> Vec<&str> {
+        if self.is_root() {
+            return vec![];
+        }
+        if let Some(rest) = self.0.strip_prefix("https://") {
+            return rest.split('/').filter(|s| !s.is_empty()).collect();
+        }
+        if let Some(rest) = self.0.strip_prefix("http://") {
+            return rest.split('/').filter(|s| !s.is_empty()).collect();
+        }
         self.0.split('/').filter(|s| !s.is_empty()).collect()
     }
 
-    /// Cumulative paths for breadcrumb rendering, e.g.
-    /// `reddit.com/r/movies` → `["reddit.com", "reddit.com/r", "reddit.com/r/movies"]`.
+    /// Cumulative navigable paths for breadcrumbs and tree wiring (includes self).
     pub fn breadcrumb_paths(&self) -> Vec<ItemId> {
+        if self.is_root() {
+            return vec![];
+        }
+        if looks_like_url(self.0.as_str()) {
+            return navigable_breadcrumbs(self.0.as_str())
+                .into_iter()
+                .map(ItemId)
+                .collect();
+        }
         let segs = self.segments();
         let mut paths = Vec::with_capacity(segs.len());
         let mut current = String::new();
@@ -111,13 +124,13 @@ impl ItemId {
         if self.is_root() {
             return String::new();
         }
-        if self.as_str().contains("://") {
-            return self.as_str().to_string();
+        if self.0.contains("://") {
+            return self.0.clone();
         }
         if self.segments().first().is_some_and(|s| s.contains('.')) {
-            format!("https://{}", self.as_str())
+            format!("https://{}", self.0)
         } else {
-            self.as_str().to_string()
+            self.0.clone()
         }
     }
 
@@ -144,70 +157,6 @@ impl ItemId {
     pub fn from_browse_uri(path: &str) -> Option<ItemId> {
         path.strip_prefix("/~/").map(ItemId::from_browse_tail)
     }
-
-    fn canonicalize(raw: &str) -> Option<String> {
-        let s = raw.trim();
-        if s.is_empty() {
-            return None;
-        }
-
-        let owned = if let Some(rest) = s.strip_prefix("r/") {
-            format!("reddit.com/r/{rest}")
-        } else if let Some(rest) = s.strip_prefix("/r/") {
-            format!("reddit.com/r/{rest}")
-        } else {
-            s.to_string()
-        };
-
-        let (host_path, _query) = split_query(&owned);
-        let host_path = host_path.trim_end_matches('/');
-
-        let path = if host_path.contains("://") {
-            parse_url_host_path(host_path)?
-        } else if host_path.starts_with("reddit.com") || host_path.starts_with("www.reddit.com") {
-            normalize_reddit_host_path(host_path)
-        } else if host_path.contains('/') {
-            host_path.to_string()
-        } else {
-            return None;
-        };
-
-        Some(normalize_reddit_path(&path))
-    }
-}
-
-fn split_query(s: &str) -> (&str, Option<&str>) {
-    if let Some((path, q)) = s.split_once('?') {
-        (path, Some(q))
-    } else {
-        (s, None)
-    }
-}
-
-fn parse_url_host_path(url: &str) -> Option<String> {
-    let rest = url
-        .strip_prefix("https://")
-        .or_else(|| url.strip_prefix("http://"))
-        .unwrap_or(url);
-    let (host, path) = rest.split_once('/').unwrap_or((rest, ""));
-    let host = normalize_host(host);
-    if path.is_empty() {
-        Some(host)
-    } else {
-        Some(format!("{host}/{path}"))
-    }
-}
-
-fn normalize_host(host: &str) -> String {
-    let h = host
-        .strip_prefix("www.")
-        .unwrap_or(host)
-        .to_ascii_lowercase();
-    if h == "old.reddit.com" || h == "new.reddit.com" || h == "reddit.com" {
-        "reddit.com".to_string()
-    } else {
-        h
-    }
 }
 
 fn normalize_browse_tail(tail: &str) -> String {
@@ -215,7 +164,6 @@ fn normalize_browse_tail(tail: &str) -> String {
     if t.is_empty() {
         return String::new();
     }
-    // Some HTTP stacks collapse `https://` → `https:/` inside a path segment.
     if t.starts_with("https:/") && !t.starts_with("https://") {
         return format!("https://{}", &t[7..]);
     }
@@ -225,33 +173,6 @@ fn normalize_browse_tail(tail: &str) -> String {
     t.to_string()
 }
 
-fn normalize_reddit_host_path(s: &str) -> String {
-    let (host, path) = s.split_once('/').unwrap_or((s, ""));
-    let host = normalize_host(host);
-    if path.is_empty() {
-        host
-    } else {
-        format!("{host}/{path}")
-    }
-}
-
-/// Lowercase subreddit segment, drop listing suffixes, drop title slug after post id.
-fn normalize_reddit_path(path: &str) -> String {
-    let mut parts: Vec<String> = path.split('/').map(str::to_string).collect();
-    if parts.len() >= 3 && parts[1] == "r" {
-        parts[2] = parts[2].to_ascii_lowercase();
-    }
-    if let Some(i) = parts.iter().position(|p| p == "comments") {
-        if parts.len() > i + 2 {
-            parts.truncate(i + 2);
-        }
-    } else if parts.len() > 3 && parts.get(1).map(|s| s.as_str()) == Some("r") {
-        // reddit.com/r/{sub}/hot → reddit.com/r/{sub}
-        parts.truncate(3);
-    }
-    parts.join("/")
-}
-
 impl fmt::Display for ItemId {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str(&self.0)
@@ -268,43 +189,59 @@ mod tests {
             "https://old.reddit.com/r/AmItheAsshole/comments/1trnvdl/aita_for_cancelling/",
         )
         .unwrap();
-        assert_eq!(id.as_str(), "reddit.com/r/amitheasshole/comments/1trnvdl");
+        assert_eq!(
+            id.as_str(),
+            "https://reddit.com/r/amitheasshole/comments/1trnvdl"
+        );
     }
 
     #[test]
     fn from_url_strips_query() {
         let id = ItemId::from_url("https://www.reddit.com/r/rust/?sort=top").unwrap();
-        assert_eq!(id.as_str(), "reddit.com/r/rust");
+        assert_eq!(id.as_str(), "https://reddit.com/r/rust");
     }
 
     #[test]
     fn from_url_short_path() {
         assert_eq!(
             ItemId::from_url("r/rust").unwrap().as_str(),
-            "reddit.com/r/rust"
+            "https://reddit.com/r/rust"
         );
     }
 
     #[test]
     fn parent_of_post_is_subreddit() {
-        let id = ItemId::parse("reddit.com/r/aww/comments/1trnvdl").unwrap();
-        assert_eq!(id.parent().unwrap().as_str(), "reddit.com/r/aww");
+        let id = ItemId::from_url("https://reddit.com/r/aww/comments/1trnvdl").unwrap();
+        assert_eq!(id.parent().unwrap().as_str(), "https://reddit.com/r/aww");
     }
 
     #[test]
     fn parent_of_subreddit_is_r_segment() {
-        let id = ItemId::parse("reddit.com/r/movies").unwrap();
-        assert_eq!(id.parent().unwrap().as_str(), "reddit.com/r");
+        let id = ItemId::from_url("https://reddit.com/r/movies").unwrap();
+        assert_eq!(id.parent().unwrap().as_str(), "https://reddit.com/r");
+    }
+
+    #[test]
+    fn breadcrumb_paths_skip_phantom_comments() {
+        let id = ItemId::from_url("https://reddit.com/r/aww/comments/1trnvdl").unwrap();
+        let crumbs = id.breadcrumb_paths();
+        let paths: Vec<_> = crumbs.iter().map(|p| p.as_str()).collect();
+        assert!(!paths.iter().any(|p| p.ends_with("/comments")));
+        assert!(paths.contains(&"https://reddit.com/r/aww"));
     }
 
     #[test]
-    fn breadcrumb_paths() {
-        let id = ItemId::parse("reddit.com/r/movies").unwrap();
+    fn breadcrumb_paths_subreddit() {
+        let id = ItemId::from_url("https://reddit.com/r/movies").unwrap();
         let crumbs = id.breadcrumb_paths();
         let paths: Vec<_> = crumbs.iter().map(|p| p.as_str()).collect();
         assert_eq!(
             paths,
-            vec!["reddit.com", "reddit.com/r", "reddit.com/r/movies"]
+            vec![
+                "https://reddit.com",
+                "https://reddit.com/r",
+                "https://reddit.com/r/movies"
+            ]
         );
     }
 
@@ -312,33 +249,33 @@ mod tests {
     fn legacy_scope_maps_to_reddit_sub() {
         assert_eq!(
             ItemId::from_legacy_scope("rust").as_str(),
-            "reddit.com/r/rust"
+            "https://reddit.com/r/rust"
         );
         assert!(ItemId::from_legacy_scope("").is_root());
     }
 
     #[test]
-    fn browse_href_wraps_canonical_path() {
-        let id = ItemId::parse("reddit.com/r/rust").unwrap();
+    fn browse_href_wraps_canonical_url() {
+        let id = ItemId::from_url("https://reddit.com/r/rust").unwrap();
         assert_eq!(id.browse_href(), "/~/https://reddit.com/r/rust");
     }
 
     #[test]
     fn from_browse_tail_parses_full_url() {
         let id = ItemId::from_browse_tail("https://reddit.com/r/AmITheAsshole");
-        assert_eq!(id.as_str(), "reddit.com/r/amitheasshole");
+        assert_eq!(id.as_str(), "https://reddit.com/r/amitheasshole");
     }
 
     #[test]
     fn from_storage_strips_post_title_slug() {
         let id =
             ItemId::from_storage("reddit.com/r/rust/comments/aaa/announcing_rust_199").unwrap();
-        assert_eq!(id.as_str(), "reddit.com/r/rust/comments/aaa");
+        assert_eq!(id.as_str(), "https://reddit.com/r/rust/comments/aaa");
     }
 
     #[test]
     fn from_browse_uri_strips_prefix() {
         let id = ItemId::from_browse_uri("/~/https://reddit.com/r/rust").unwrap();
-        assert_eq!(id.as_str(), "reddit.com/r/rust");
+        assert_eq!(id.as_str(), "https://reddit.com/r/rust");
     }
 }
diff --git a/server/src/projection_apply.rs b/server/src/projection_apply.rs
index ebe122e417bda1d9369a53443de93d28213c5a0d..5644557a41b3e9497c7421b444155ae629fa79f1 100644
--- a/server/src/projection_apply.rs
+++ b/server/src/projection_apply.rs
@@ -19,13 +19,21 @@ use crate::{
     storage_schema::{ensure_path_writes, entity_view_writes, vote_writes},
 };
 
-/// Legacy-compatible scope parsing for persisted vote events.
+fn parse_event_id(id: &str) -> Result<ItemId, EventLogError> {
+    ItemId::from_storage(id)
+        .or_else(|| ItemId::parse(id))
+        .ok_or_else(|| EventLogError::Apply(format!("invalid id: {id}")))
+}
+
+/// Scope key from a vote event (canonicalized at apply time).
 fn parent_from_event_scope(scope: &str) -> ItemId {
-    if scope.contains('/') {
-        ItemId::parse(scope).unwrap_or_else(|| ItemId::from_legacy_scope(scope))
-    } else {
-        ItemId::from_legacy_scope(scope)
+    let s = scope.trim();
+    if s.is_empty() {
+        return ItemId::root();
     }
+    ItemId::from_storage(s)
+        .or_else(|| ItemId::parse(s))
+        .unwrap_or_else(|| ItemId::from_legacy_scope(s))
 }
 
 pub fn apply_records(
@@ -68,15 +76,11 @@ pub fn apply_records(
                 vote_parents.insert(parent);
             }
             Event::NodeEnsured { id } => {
-                let parsed = ItemId::parse(id)
-                    .or_else(|| ItemId::from_url(id))
-                    .ok_or_else(|| EventLogError::Apply(format!("invalid node id: {id}")))?;
+                let parsed = parse_event_id(id)?;
                 ensure_path_writes(&mut batch, &parsed);
             }
             Event::EntityImported { id, payload, .. } => {
-                let parsed = ItemId::parse(id)
-                    .or_else(|| ItemId::from_url(id))
-                    .ok_or_else(|| EventLogError::Apply(format!("invalid entity id: {id}")))?;
+                let parsed = parse_event_id(id)?;
                 let view = entity_view_from_payload(&parsed, payload);
                 entity_view_writes(&mut batch, &parsed, view.as_ref());
                 entity_store
@@ -92,7 +96,6 @@ pub fn apply_records(
         .commit_with(durable::Durability::DisableWal)
         .map_err(|e| EventLogError::Apply(e.to_string()))?;
 
-    // Cap recent-vote windows (idempotent, blind; not part of the cursor batch).
     for parent in vote_parents {
         projection_store
             .trim_recent_votes(&parent)
diff --git a/server/src/reddit.rs b/server/src/reddit.rs
index 72caf7c33b9dd44ea15b62b59e91227cf96a3431..20b7f9e3f8be39268a1767d09f5cf81eaa6ae0df 100644
--- a/server/src/reddit.rs
+++ b/server/src/reddit.rs
@@ -183,7 +183,7 @@ pub fn entity_view_from_payload(
     id: &ItemId,
     payload: &Value,
 ) -> Option<crate::reducer::EntityData> {
-    if id.as_str().starts_with("reddit.com") {
+    if id.as_str().contains("reddit.com") {
         return parse_reddit_view(id, payload);
     }
     None
@@ -495,41 +495,59 @@ fn rate_limit_reset_secs(resp: &reqwest::Response) -> u64 {
         .unwrap_or(5)
 }
 
+fn reddit_path_segments(id: &ItemId) -> Option<Vec<String>> {
+    let s = id.as_str();
+    let rest = s
+        .strip_prefix("https://reddit.com/")
+        .or_else(|| s.strip_prefix("http://reddit.com/"))
+        .or_else(|| s.strip_prefix("reddit.com/"))?;
+    let segments: Vec<String> = rest
+        .split('/')
+        .filter(|p| !p.is_empty())
+        .map(str::to_string)
+        .collect();
+    Some(segments)
+}
+
 pub fn map_item_to_reddit_api(id: &ItemId, api_base: &str) -> String {
-    let path = id.as_str();
-    if !path.starts_with("reddit.com/") && path != "reddit.com" {
-        return String::new();
-    }
+    let segments = match reddit_path_segments(id) {
+        Some(s) => s,
+        None if matches!(
+            id.as_str(),
+            "https://reddit.com" | "http://reddit.com" | "reddit.com"
+        ) =>
+        {
+            return String::new();
+        }
+        None => return String::new(),
+    };
 
     let base = api_base.trim_end_matches('/');
 
-    let segments: Vec<&str> = path.split('/').collect();
-
-    if let Some(i) = segments.iter().position(|&p| p == "comments") {
+    if let Some(i) = segments.iter().position(|p| p == "comments") {
         if segments.len() > i + 1 {
-            let api_path = segments[1..=i + 1].join("/");
+            let api_path = segments[..=i + 1].join("/");
             return format!("{base}/{api_path}.json?raw_json=1");
         }
     }
 
-    if segments.len() == 3 && segments[1] == "r" {
-        return format!("{base}/r/{}/about.json?raw_json=1", segments[2]);
+    if segments.len() == 2 && segments[0] == "r" {
+        return format!("{base}/r/{}/about.json?raw_json=1", segments[1]);
     }
 
     String::new()
 }
 
 /// Listing URL for a node's children. Currently only subreddits
-/// (`reddit.com/r/<sub>` → `/r/<sub>.json`) expose a child listing.
+/// (`https://reddit.com/r/<sub>` → `/r/<sub>.json`) expose a child listing.
 pub fn map_children_url(id: &ItemId, api_base: &str) -> String {
-    let path = id.as_str();
-    if !path.starts_with("reddit.com/") {
-        return String::new();
-    }
+    let segments = match reddit_path_segments(id) {
+        Some(s) => s,
+        None => return String::new(),
+    };
     let base = api_base.trim_end_matches('/');
-    let segments: Vec<&str> = path.split('/').collect();
-    if segments.len() == 3 && segments[1] == "r" {
-        return format!("{base}/r/{}.json?raw_json=1&limit=25", segments[2]);
+    if segments.len() == 2 && segments[0] == "r" {
+        return format!("{base}/r/{}.json?raw_json=1&limit=25", segments[1]);
     }
     String::new()
 }
@@ -548,8 +566,8 @@ fn parse_children(_parent: &ItemId, payload: &Value) -> Vec<(ItemId, Value)> {
             Some(p) if !p.is_empty() => p,
             _ => continue,
         };
-        let path = format!("reddit.com{}", permalink.trim_end_matches('/'));
-        if let Some(id) = ItemId::from_storage(&path) {
+        let raw = format!("https://reddit.com{}", permalink.trim_end_matches('/'));
+        if let Some(id) = ItemId::from_url(&raw) {
             out.push((id, child.clone()));
         }
     }
@@ -683,7 +701,7 @@ mod tests {
 
     #[test]
     fn map_subreddit_about_url() {
-        let id = ItemId::parse("reddit.com/r/rust").unwrap();
+        let id = ItemId::from_url("https://reddit.com/r/rust").unwrap();
         assert_eq!(
             map_item_to_reddit_api(&id, "https://www.reddit.com"),
             "https://www.reddit.com/r/rust/about.json?raw_json=1"
@@ -699,7 +717,8 @@ mod tests {
         let json = include_str!("../../test/fixtures/reddit/r_rust_about.json");
         let v: Value = serde_json::from_str(json).unwrap();
         let entity =
-            entity_view_from_payload(&ItemId::parse("reddit.com/r/rust").unwrap(), &v).unwrap();
+            entity_view_from_payload(&ItemId::from_url("https://reddit.com/r/rust").unwrap(), &v)
+                .unwrap();
         assert_eq!(entity.title, "The Rust Programming Language");
     }
 
@@ -707,7 +726,8 @@ mod tests {
     fn parse_post_listing_extracts_thumb_and_full_preview() {
         let json = include_str!("../../test/fixtures/reddit/post_preview.json");
         let v: Value = serde_json::from_str(json).unwrap();
-        let id = ItemId::parse("reddit.com/r/nsfw/comments/1tpy6a1/angel_eyes").unwrap();
+        let id =
+            ItemId::from_url("https://reddit.com/r/nsfw/comments/1tpy6a1/angel_eyes").unwrap();
         let entity = entity_view_from_payload(&id, &v).unwrap();
         assert_eq!(entity.title, "Angel Eyes");
         assert!(entity.thumb_url.as_ref().unwrap().contains("width=140"));
diff --git a/server/src/reducer.rs b/server/src/reducer.rs
index 6578f64a41726845517cdbf59a359c69e0aa56db..5179ddeca7a7cb0fb92dfc4aa9d5a80bd9125611 100644
--- a/server/src/reducer.rs
+++ b/server/src/reducer.rs
@@ -248,16 +248,18 @@ mod from_recorded_tests {
     #[test]
     fn ensure_path_wires_children() {
         let mut tree = GlobalTree::new();
-        let id = ItemId::parse("reddit.com/r/rust").unwrap();
+        let id = ItemId::from_url("https://reddit.com/r/rust").unwrap();
         tree.ensure_path(&id);
         let root = tree.get(&ItemId::root()).unwrap();
         assert!(root
             .children
-            .contains(&ItemId::parse("reddit.com").unwrap()));
-        let reddit = tree.get(&ItemId::parse("reddit.com").unwrap()).unwrap();
+            .contains(&ItemId::from_url("https://reddit.com").unwrap()));
+        let reddit = tree
+            .get(&ItemId::from_url("https://reddit.com").unwrap())
+            .unwrap();
         assert!(reddit
             .children
-            .contains(&ItemId::parse("reddit.com/r").unwrap()));
+            .contains(&ItemId::from_url("https://reddit.com/r").unwrap()));
         let sub = tree.get(&id).unwrap();
         assert_eq!(sub.id, id);
     }
diff --git a/server/src/render/reddit.rs b/server/src/render/reddit.rs
index 7f840aa33b734a31d8cf3341a0581c8bcb9bbcf3..595e202436040b0bfc419e68f083f94757ba5d0c 100644
--- a/server/src/render/reddit.rs
+++ b/server/src/render/reddit.rs
@@ -9,7 +9,7 @@ use crate::{
 };
 
 pub fn is_reddit_post(id: &ItemId) -> bool {
-    id.as_str().starts_with("reddit.com/") && id.as_str().contains("/comments/")
+    id.as_str().contains("reddit.com/") && id.as_str().contains("/comments/")
 }
 
 /// Post detail card (inside [`crate::fetch::html::entity_panel`]).
diff --git a/server/src/state.rs b/server/src/state.rs
index 78126f08d90f8069a586279d79258c27a9f9f7a4..513b329ef45fc332e63b3f8ed8498a1f59feb07c 100644
--- a/server/src/state.rs
+++ b/server/src/state.rs
@@ -217,15 +217,21 @@ impl AppState {
         ratio_right: i32,
     ) -> Result<(), String> {
         let ts = crate::html::now_ms();
-        let vote = VoteData::from_recorded(ts, a, b, ratio_left, ratio_right)
-            .ok_or_else(|| "invalid vote: need two distinct non-empty items".to_string())?;
+        let a_raw = a.trim();
+        let b_raw = b.trim();
+        if a_raw.is_empty() || b_raw.is_empty() || a_raw == b_raw {
+            return Err("invalid vote: need two distinct non-empty items".to_string());
+        }
+        // Validate items canonicalize (or are opaque keys) before append.
+        let _ = VoteData::from_recorded(ts, a_raw, b_raw, ratio_left, ratio_right)
+            .ok_or_else(|| "invalid vote: need two distinct parseable items".to_string())?;
 
         let event = Event::VoteRecorded {
             ts,
-            a: vote.a.as_str().to_string(),
-            b: vote.b.as_str().to_string(),
-            ratio_left: vote.ratio_left,
-            ratio_right: vote.ratio_right,
+            a: a_raw.to_string(),
+            b: b_raw.to_string(),
+            ratio_left,
+            ratio_right,
             scope: parent.as_str().to_string(),
         };
 
@@ -253,7 +259,7 @@ mod tests {
         let log = EventLog::new(log_path.to_string_lossy().into_owned());
         let payload = json!({"kind":"t5","data":{"title":"Rust","display_name":"rust"}});
         let event = Event::EntityImported {
-            id: "reddit.com/r/rust".into(),
+            id: "https://reddit.com/r/rust".into(),
             ts: 1,
             payload: payload.clone(),
         };
@@ -266,14 +272,14 @@ mod tests {
             .await
             .unwrap();
         let tree = projection_store
-            .scope_tree(&ItemId::parse("reddit.com/r/rust").unwrap())
+            .scope_tree(&ItemId::parse("https://reddit.com/r/rust").unwrap())
             .unwrap();
         let node = tree
-            .get(&ItemId::parse("reddit.com/r/rust").unwrap())
+            .get(&ItemId::parse("https://reddit.com/r/rust").unwrap())
             .unwrap();
         assert_eq!(node.data.as_ref().unwrap().title, "Rust");
         let stored = entity_store
-            .get(&ItemId::parse("reddit.com/r/rust").unwrap())
+            .get(&ItemId::parse("https://reddit.com/r/rust").unwrap())
             .unwrap()
             .unwrap();
         assert_eq!(stored["data"]["display_name"], "rust");
@@ -289,13 +295,13 @@ mod tests {
             event_record(
                 1,
                 Event::NodeEnsured {
-                    id: "reddit.com/r/rust".into(),
+                    id: "https://reddit.com/r/rust".into(),
                 },
             ),
             event_record(
                 2,
                 Event::EntityImported {
-                    id: "reddit.com/r/rust".into(),
+                    id: "https://reddit.com/r/rust".into(),
                     ts: 2,
                     payload: payload.clone(),
                 },
@@ -325,7 +331,7 @@ mod tests {
                 &[event_record(
                     1,
                     Event::NodeEnsured {
-                        id: "reddit.com/r/stale".into(),
+                        id: "https://reddit.com/r/stale".into(),
                     },
                 )],
             )
@@ -352,11 +358,11 @@ mod tests {
         let root = tree.get(&ItemId::root()).unwrap();
         assert!(root.children.contains(&ItemId::parse("alpha").unwrap()));
         assert!(projection_store
-            .load_node(&ItemId::parse("reddit.com/r/stale").unwrap())
+            .load_node(&ItemId::parse("https://reddit.com/r/stale").unwrap())
             .unwrap()
             .is_none());
         let stored = entity_store
-            .get(&ItemId::parse("reddit.com/r/rust").unwrap())
+            .get(&ItemId::parse("https://reddit.com/r/rust").unwrap())
             .unwrap()
             .unwrap();
         assert_eq!(stored["data"]["display_name"], "rust");
@@ -370,7 +376,7 @@ mod tests {
         log.append(&event_record(
             1,
             Event::NodeEnsured {
-                id: "reddit.com/r/rust".into(),
+                id: "https://reddit.com/r/rust".into(),
             },
         ))
         .await
@@ -387,7 +393,7 @@ mod tests {
                 &[event_record(
                     2,
                     Event::NodeEnsured {
-                        id: "reddit.com/r/rust".into(),
+                        id: "https://reddit.com/r/rust".into(),
                     },
                 )],
             )
@@ -454,7 +460,7 @@ mod tests {
             port: 0,
         })
         .await;
-        let id = ItemId::parse("reddit.com/r/rust").unwrap();
+        let id = ItemId::parse("https://reddit.com/r/rust").unwrap();
 
         state.ensure_node(&id).await.unwrap();
 
@@ -465,11 +471,11 @@ mod tests {
         let projected = state.projection_store.load_tree().unwrap();
         assert!(projected.get(&id).is_some());
         let reddit = projected
-            .get(&ItemId::parse("reddit.com").unwrap())
+            .get(&ItemId::from_url("https://reddit.com").unwrap())
             .unwrap();
         assert!(reddit
             .children
-            .contains(&ItemId::parse("reddit.com/r").unwrap()));
+            .contains(&ItemId::from_url("https://reddit.com/r").unwrap()));
     }
 
     #[tokio::test]
@@ -510,7 +516,7 @@ mod tests {
         log.append(&event_record(
             1,
             Event::NodeEnsured {
-                id: "reddit.com/r/rust".into(),
+                id: "https://reddit.com/r/rust".into(),
             },
         ))
         .await
@@ -518,7 +524,7 @@ mod tests {
         log.append(&event_record(
             2,
             Event::NodeEnsured {
-                id: "reddit.com/r/python".into(),
+                id: "https://reddit.com/r/python".into(),
             },
         ))
         .await
@@ -544,13 +550,13 @@ mod tests {
             2
         );
         let tree = second
-            .scope_tree(&ItemId::parse("reddit.com/r/rust").unwrap())
+            .scope_tree(&ItemId::parse("https://reddit.com/r/rust").unwrap())
             .unwrap();
         assert!(tree
-            .get(&ItemId::parse("reddit.com/r/rust").unwrap())
+            .get(&ItemId::parse("https://reddit.com/r/rust").unwrap())
             .is_some());
         assert!(tree
-            .get(&ItemId::parse("reddit.com/r/python").unwrap())
+            .get(&ItemId::parse("https://reddit.com/r/python").unwrap())
             .is_none());
     }
 
@@ -611,7 +617,7 @@ mod tests {
     #[test]
     fn parse_item_param_from_url() {
         let id = parse_item_param("https://reddit.com/r/rust");
-        assert_eq!(id.as_str(), "reddit.com/r/rust");
+        assert_eq!(id.as_str(), "https://reddit.com/r/rust");
     }
 
     #[test]
diff --git a/server/src/url_rules/engine.rs b/server/src/url_rules/engine.rs
new file mode 100644
index 0000000000000000000000000000000000000000..e29b6b48c08deb7bffe031b1e542b1e25a7bef15
--- /dev/null
+++ b/server/src/url_rules/engine.rs
@@ -0,0 +1,187 @@
+//! Composable URL normalization primitives.
+
+use std::collections::HashMap;
+
+use url::Url;
+
+/// Mutable URL view used by rule combinators before serializing to a canonical string.
+#[derive(Debug, Clone)]
+pub struct ParsedUrl {
+    pub scheme: String,
+    pub host: String,
+    pub path_segments: Vec<String>,
+    pub query: HashMap<String, String>,
+    pub fragment: Option<String>,
+}
+
+impl ParsedUrl {
+    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,
+            fragment: url.fragment().map(str::to_string),
+            host,
+        })
+    }
+
+    pub fn with_path_segments(&self, segments: &[String]) -> Self {
+        let mut u = self.clone();
+        u.path_segments = segments.to_vec();
+        u
+    }
+
+    pub fn to_url(&self) -> Option<Url> {
+        let mut url = if self.path_segments.is_empty() {
+            Url::parse(&format!("{}://{}", self.scheme, self.host)).ok()?
+        } else {
+            let path = format!("/{}", self.path_segments.join("/"));
+            Url::parse(&format!("{}://{}{}", self.scheme, self.host, path)).ok()?
+        };
+        if !self.query.is_empty() {
+            let mut pairs: Vec<_> = self.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);
+            }
+        }
+        if let Some(ref frag) = self.fragment {
+            url.set_fragment(Some(frag));
+        }
+        Some(url)
+    }
+
+    pub fn canonical_string(&self) -> Option<String> {
+        let url = self.to_url()?;
+        let mut s = url.to_string();
+        if self.path_segments.is_empty() {
+            s = s.trim_end_matches('/').to_string();
+        }
+        Some(s)
+    }
+}
+
+pub fn force_https(u: &mut ParsedUrl) {
+    if u.scheme == "http" {
+        u.scheme = "https".to_string();
+    }
+}
+
+pub fn drop_fragment(u: &mut ParsedUrl) {
+    u.fragment = None;
+}
+
+pub fn strip_www(u: &mut ParsedUrl) {
+    if u.host.starts_with("www.") {
+        u.host = u.host[4..].to_string();
+    }
+}
+
+pub fn lowercase_host(u: &mut ParsedUrl) {
+    u.host = u.host.to_ascii_lowercase();
+}
+
+pub fn lowercase_path(u: &mut ParsedUrl) {
+    for seg in &mut u.path_segments {
+        *seg = seg.to_ascii_lowercase();
+    }
+}
+
+pub fn clear_query(u: &mut ParsedUrl) {
+    u.query.clear();
+}
+
+pub fn keep_only_query(u: &mut ParsedUrl, keys: &[&str]) {
+    u.query
+        .retain(|k, _| keys.iter().any(|want| want == &k.as_str()));
+}
+
+pub fn strip_tracking_params(u: &mut ParsedUrl) {
+    u.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"
+            ))
+    });
+}
+
+pub fn truncate_after_segment(u: &mut ParsedUrl, name: &str, keep: usize) {
+    if let Some(i) = u.path_segments.iter().position(|s| s == name) {
+        let end = (i + 1 + keep).min(u.path_segments.len());
+        u.path_segments.truncate(end);
+    }
+}
+
+pub fn drop_listing_suffix(u: &mut ParsedUrl, suffixes: &[&str]) {
+    if u.path_segments.len() >= 3 && u.path_segments.first().map(String::as_str) == Some("r") {
+        if let Some(last) = u.path_segments.last() {
+            if suffixes.iter().any(|s| *s == last.as_str()) {
+                u.path_segments.pop();
+            }
+        }
+    }
+}
+
+pub fn normalize_reddit_host(u: &mut ParsedUrl) {
+    if matches!(
+        u.host.as_str(),
+        "old.reddit.com" | "new.reddit.com" | "www.reddit.com"
+    ) {
+        u.host = "reddit.com".to_string();
+    }
+}
+
+pub fn rewrite_youtu_be(u: &mut ParsedUrl) {
+    if u.host == "youtu.be" && u.path_segments.len() == 1 {
+        let id = u.path_segments[0].clone();
+        u.host = "youtube.com".to_string();
+        u.path_segments = vec!["watch".to_string()];
+        u.query.insert("v".to_string(), id);
+    }
+}
+
+pub fn rewrite_youtube_shorts(u: &mut ParsedUrl) {
+    if u.host == "youtube.com" && u.path_segments.first().map(String::as_str) == Some("shorts") {
+        if let Some(id) = u.path_segments.get(1).cloned() {
+            u.path_segments = vec!["watch".to_string()];
+            u.query.insert("v".to_string(), id);
+        }
+    }
+}
+
+pub fn normalize_youtube_host(u: &mut ParsedUrl) {
+    if matches!(u.host.as_str(), "m.youtube.com" | "www.youtube.com") {
+        u.host = "youtube.com".to_string();
+    }
+}
diff --git a/server/src/url_rules/mod.rs b/server/src/url_rules/mod.rs
new file mode 100644
index 0000000000000000000000000000000000000000..03d53bd3e82d704a01ba3fd8dd02b7d31422c0de
--- /dev/null
+++ b/server/src/url_rules/mod.rs
@@ -0,0 +1,13 @@
+//! URL canonicalization and hierarchy rules for [`crate::path_types::ItemId`].
+
+mod engine;
+mod registry;
+
+pub use registry::{
+    canonicalize_raw, looks_like_url, navigable_breadcrumbs, parent_url, resolve_id, CanonicalResult,
+};
+
+/// Resolve raw input to canonical URL.
+pub fn resolve_canonical(raw: &str) -> Option<String> {
+    canonicalize_raw(raw.trim()).map(|r| r.canonical)
+}
diff --git a/server/src/url_rules/registry.rs b/server/src/url_rules/registry.rs
new file mode 100644
index 0000000000000000000000000000000000000000..14514e9af8385fb2b9b2f35eb9ee14d453d4b97c
--- /dev/null
+++ b/server/src/url_rules/registry.rs
@@ -0,0 +1,235 @@
+//! Per-domain canonicalization and hierarchy rules.
+
+use std::collections::HashSet;
+
+use super::engine::{
+    clear_query, drop_fragment, drop_listing_suffix, force_https, keep_only_query, lowercase_host,
+    lowercase_path, normalize_reddit_host, normalize_youtube_host, rewrite_youtu_be,
+    rewrite_youtube_shorts, strip_tracking_params, strip_www, truncate_after_segment, ParsedUrl,
+};
+
+/// Result of canonicalizing a raw URL string.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct CanonicalResult {
+    pub canonical: String,
+    /// When the input normalizes to a different string, the original is an alias.
+    pub alias_of: Option<String>,
+}
+
+fn apply_global(u: &mut ParsedUrl) {
+    force_https(u);
+    drop_fragment(u);
+    strip_www(u);
+    lowercase_host(u);
+    strip_tracking_params(u);
+}
+
+fn normalize_reddit(u: &mut ParsedUrl) {
+    normalize_reddit_host(u);
+    lowercase_path(u);
+    truncate_after_segment(u, "comments", 1);
+    drop_listing_suffix(u, &["hot", "top", "new", "rising", "controversial"]);
+    clear_query(u);
+}
+
+fn normalize_youtube(u: &mut ParsedUrl) {
+    rewrite_youtu_be(u);
+    normalize_youtube_host(u);
+    rewrite_youtube_shorts(u);
+    keep_only_query(u, &["v", "list"]);
+}
+
+fn normalize_default(_u: &mut ParsedUrl) {
+    // Global rules only.
+}
+
+fn domain_key(host: &str) -> &'static str {
+    if host == "reddit.com" || host.ends_with(".reddit.com") {
+        "reddit.com"
+    } else if host == "youtube.com" || host == "youtu.be" {
+        "youtube.com"
+    } else {
+        "default"
+    }
+}
+
+fn normalize_for_host(u: &mut ParsedUrl) {
+    apply_global(u);
+    match domain_key(&u.host) {
+        "reddit.com" => normalize_reddit(u),
+        "youtube.com" => normalize_youtube(u),
+        _ => normalize_default(u),
+    }
+}
+
+/// Structural path segments that must not become standalone tree nodes when more path follows.
+fn structural_trailing(host: &str) -> &'static [&'static str] {
+    match domain_key(host) {
+        "reddit.com" => &["comments"],
+        _ => &[],
+    }
+}
+
+/// Canonicalize a raw URL. Returns `None` if the input is not URL-like.
+pub fn canonicalize_raw(raw: &str) -> Option<CanonicalResult> {
+    let trimmed = raw.trim();
+    if trimmed.is_empty() {
+        return None;
+    }
+    let mut u = ParsedUrl::parse(trimmed)?;
+    let input_snapshot = u.canonical_string()?;
+    normalize_for_host(&mut u);
+    let canonical = u.canonical_string()?;
+    let alias_of = if input_snapshot != canonical {
+        Some(trimmed.to_string())
+    } else {
+        None
+    };
+    Some(CanonicalResult {
+        canonical,
+        alias_of,
+    })
+}
+
+/// Resolve a stored or event id string to its canonical URL identity.
+pub fn resolve_id(raw: &str) -> Option<String> {
+    canonicalize_raw(raw).map(|r| r.canonical)
+}
+
+/// Navigable ancestor URLs from domain root up to and including `canonical` (full URLs).
+pub fn navigable_breadcrumbs(canonical: &str) -> Vec<String> {
+    let Some(u) = ParsedUrl::parse(canonical) else {
+        return vec![canonical.to_string()];
+    };
+    let structural: HashSet<&str> = structural_trailing(&u.host).iter().copied().collect();
+    let n = u.path_segments.len();
+    let mut out = Vec::new();
+
+    // Domain root (no path segments).
+    if let Some(base) = u.with_path_segments(&[]).canonical_string() {
+        out.push(base);
+    }
+
+    for i in 0..n {
+        let segs: Vec<String> = u.path_segments[..=i].to_vec();
+        let is_last = i == n - 1;
+        let seg = u.path_segments[i].as_str();
+        if structural.contains(seg) && !is_last {
+            continue;
+        }
+        if let Some(url) = u.with_path_segments(&segs).canonical_string() {
+            if out.last() != Some(&url) {
+                out.push(url);
+            }
+        }
+    }
+    out
+}
+
+/// Immediate parent scope URL, or `None` for tree root / opaque single-segment ids.
+pub fn parent_url(canonical: &str) -> Option<String> {
+    let crumbs = navigable_breadcrumbs(canonical);
+    if crumbs.len() <= 1 {
+        None
+    } else {
+        crumbs.get(crumbs.len() - 2).cloned()
+    }
+}
+
+/// True when `raw` looks like a URL (has scheme or host-like shape).
+pub fn looks_like_url(raw: &str) -> bool {
+    let t = raw.trim();
+    t.contains("://")
+        || t.starts_with("r/")
+        || t.starts_with("/r/")
+        || (t.contains('.') && t.contains('/'))
+        || t.starts_with("reddit.com")
+        || t.starts_with("www.")
+        || t.starts_with("youtu.be/")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn reddit_post_drops_slug_and_normalizes_host() {
+        let r = canonicalize_raw(
+            "https://old.reddit.com/r/AmItheAsshole/comments/1trnvdl/aita_for_cancelling/",
+        )
+        .unwrap();
+        assert_eq!(
+            r.canonical,
+            "https://reddit.com/r/amitheasshole/comments/1trnvdl"
+        );
+    }
+
+    #[test]
+    fn reddit_strips_query_and_listing() {
+        assert_eq!(
+            canonicalize_raw("https://www.reddit.com/r/rust/?sort=top")
+                .unwrap()
+                .canonical,
+            "https://reddit.com/r/rust"
+        );
+        assert_eq!(
+            canonicalize_raw("https://www.reddit.com/r/programming/hot")
+                .unwrap()
+                .canonical,
+            "https://reddit.com/r/programming"
+        );
+    }
+
+    #[test]
+    fn reddit_short_path() {
+        assert_eq!(
+            canonicalize_raw("r/rust").unwrap().canonical,
+            "https://reddit.com/r/rust"
+        );
+    }
+
+    #[test]
+    fn reddit_breadcrumbs_skip_phantom_comments() {
+        let post = "https://reddit.com/r/aww/comments/1trnvdl";
+        let crumbs = navigable_breadcrumbs(post);
+        assert!(!crumbs.iter().any(|c| c.ends_with("/comments")));
+        assert_eq!(
+            crumbs.last().map(String::as_str),
+            Some(post)
+        );
+        assert!(crumbs.contains(&"https://reddit.com/r/aww".to_string()));
+    }
+
+    #[test]
+    fn reddit_parent_of_post_is_subreddit() {
+        assert_eq!(
+            parent_url("https://reddit.com/r/aww/comments/1trnvdl").as_deref(),
+            Some("https://reddit.com/r/aww")
+        );
+    }
+
+    #[test]
+    fn youtube_youtu_be_and_watch_same_canonical() {
+        let a = canonicalize_raw("https://youtu.be/dQw4w9WgXcQ").unwrap().canonical;
+        let b = canonicalize_raw("https://www.youtube.com/watch?v=dQw4w9WgXcQ&t=10").unwrap();
+        assert_eq!(a, b.canonical);
+        assert_eq!(a, "https://youtube.com/watch?v=dQw4w9WgXcQ");
+    }
+
+    #[test]
+    fn legacy_schemeless_upgrades() {
+        assert_eq!(
+            canonicalize_raw("reddit.com/r/rust/comments/aaa/announcing_rust_199")
+                .unwrap()
+                .canonical,
+            "https://reddit.com/r/rust/comments/aaa"
+        );
+    }
+
+    #[test]
+    fn alias_recorded_when_input_differs() {
+        let r = canonicalize_raw("https://youtu.be/abc123").unwrap();
+        assert_eq!(r.canonical, "https://youtube.com/watch?v=abc123");
+        assert!(r.alias_of.is_some());
+    }
+}