You are ranking individual git commits to an open source project.
Compare these two commits. Decide which commit contributed more.
Return ONLY a JSON object: {"winner": "A" or "B", "ratio": "N:M", "explanation": "..."}

Side A — contributor: tommy-mor
Side A — commit message:
[047b82bd] Remove redundant zero-ratio guard from reducer.

Zeros are already rejected at the DSL parser and browser handler;
the guard in apply_vote was dead code. The negative clamping stays
since add_edge_weight already skips weight-0 edges correctly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Side A — unified diff (full patch):
diff --git a/server/src/reducer.rs b/server/src/reducer.rs
index 0e36979abe0f051493038ff7e652efc7f7a0ac80..efbf7f67ff24c7a2989102fe62879b2794a27c5f 100644
--- a/server/src/reducer.rs
+++ b/server/src/reducer.rs
@@ -112,11 +112,6 @@ impl GroupState {
         if vote.ratio_right < 0 {
             vote.ratio_right = 0;
         }
-        if vote.ratio_left == 0 || vote.ratio_right == 0 {
-            // Zero on either side produces no valid edge; drop before registering items or pair.
-            return;
-        }
-
         let a_idx = self.ensure_item(&vote.a);
         let b_idx = self.ensure_item(&vote.b);
 
diff --git a/server/tests/basic.rs b/server/tests/basic.rs
index 08159f4a7f0850fd165817a4a1af4f31ced2ad76..1748769ccf7196b2d81cf556d5368c7e723f6a4e 100644
--- a/server/tests/basic.rs
+++ b/server/tests/basic.rs
@@ -533,7 +533,7 @@ fn dsl_parse_rejects_zero_zero_vote_ratio() {
 #[test]
 fn reducer_negative_ratio_clamped_to_zero() {
     let _state = ReducerState::default();
-    // GroupState::apply_vote clamps negatives to 0; when either side is 0 the vote is dropped.
+    // apply_vote clamps negatives to 0; add_edge_weight skips zero-weight edges.
     let mut group = GroupState::new();
     group.apply_vote(slugsocial_server::reducer::VoteData {
         ts: 1,
@@ -546,10 +546,9 @@ fn reducer_negative_ratio_clamped_to_zero() {
         delegate: Some("00000000-0000-0000-0000-000000000000:test:local/test".to_string()),
         thread_tag: "t".to_string(),
     });
-    // Nothing registered: zero-clamped vote is dropped before ensure_item.
-    assert!(group.idx_to_item.is_empty());
+    // Items and pair are registered; edges are absent because weight 0 is skipped.
+    assert_eq!(group.idx_to_item.len(), 2);
     assert!(group.edges.is_empty());
-    assert!(group.voted_pairs.is_empty());
 }
 
 


Side B — contributor: tommy-mor
Side B — commit message:
[04b81f91] Fix vote compare highlighting

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

Side B — unified diff (full patch):
diff --git a/server/src/html/mod.rs b/server/src/html/mod.rs
index 588cf62bcea608ed4ede363810f022a67b43b960..e180a0ca542a33e2300c0a4809e6b9cfee07ecfe 100644
--- a/server/src/html/mod.rs
+++ b/server/src/html/mod.rs
@@ -291,18 +291,17 @@ fn rank_list(
     label: &str,
     items: &[RankedItem],
     start_rank: usize,
-    total_ranked: usize,
-    ordinal_offset: usize,
     highlighted: &HashSet<ItemId>,
     tree: &GlobalTree,
 ) -> Markup {
+    let group_len = items.len();
     html! {
         @if !items.is_empty() {
             h3 class="rank-heading muted small" { (label) }
             ol class="rank-list" {
                 @for (i, r) in items.iter().enumerate() {
                     @let href = item_href(&r.item);
-                    @let style = rank_row_style(parent, ordinal_offset + i, total_ranked);
+                    @let style = rank_row_style(parent, i, group_len);
                     @let class = rank_row_class(&r.item, highlighted);
                     li class=(class)
                         data-rank-item=(r.item.as_str())
@@ -420,8 +419,6 @@ pub fn ranking_panel_with_highlights(
 
     let has_ranked = !ranked_groups.is_empty();
     let multi = ranked_groups.len() > 1;
-    let total_ranked: usize = ranked_groups.iter().map(|g| g.len()).sum();
-    let mut ordinal_offset = 0usize;
 
     html! {
         section id="ranking-panel" class="demo-panel" {
@@ -436,8 +433,7 @@ pub fn ranking_panel_with_highlights(
             } @else {
                 @for (gi, ranked) in ranked_groups.iter().enumerate() {
                     @let label = if multi { format!("Ranking group {}", gi + 1) } else { "Ranking".to_string() };
-                    (rank_list(item, &label, ranked, 1, total_ranked, ordinal_offset, highlighted, tree))
-                    @let _ = { ordinal_offset += ranked.len(); };
+                    (rank_list(item, &label, ranked, 1, highlighted, tree))
                 }
                 (unranked_list("Unranked", &unranked, highlighted, tree))
             }
@@ -520,7 +516,20 @@ pub async fn browse(State(state): State<AppState>, uri: Uri) -> impl IntoRespons
 
 #[cfg(test)]
 mod tests {
-    use super::SORTER_UI_JS;
+    use super::{rank_row_style, SORTER_UI_JS};
+    use crate::path_types::ItemId;
+
+    #[test]
+    fn rank_row_style_gradients_per_group_not_globally() {
+        let parent = ItemId::opaque("test-scope");
+        let first_in_four = rank_row_style(&parent, 0, 4);
+        let last_in_four = rank_row_style(&parent, 3, 4);
+        let first_in_two = rank_row_style(&parent, 0, 2);
+        let last_in_two = rank_row_style(&parent, 1, 2);
+        assert_eq!(first_in_four, first_in_two);
+        assert_eq!(last_in_four, last_in_two);
+        assert_ne!(first_in_four, last_in_four);
+    }
 
     #[test]
     fn vote_slider_left_position_favors_left_item() {
diff --git a/server/src/html/vote.rs b/server/src/html/vote.rs
index 483c7ff8cd35266744957cf0087f2b5f76f1a237..30dab303b9d1e763a5b9261dffff13a778e3e4e3 100644
--- a/server/src/html/vote.rs
+++ b/server/src/html/vote.rs
@@ -19,7 +19,7 @@ use crate::{
     ui_action::UI_RPC_FIELD,
 };
 
-use super::{breadcrumb_path, item_href, layout};
+use super::{breadcrumb_path, layout};
 
 #[derive(Debug, Deserialize)]
 pub struct VoteQuery {
@@ -59,17 +59,6 @@ fn child_title(tree: &GlobalTree, id: &ItemId) -> String {
         .unwrap_or_else(|| display_label(id))
 }
 
-fn ratio_pct(ratio_left: i32, ratio_right: i32) -> f64 {
-    let l = ratio_left.max(0) as f64;
-    let r = ratio_right.max(0) as f64;
-    let sum = l + r;
-    if sum <= 0.0 {
-        50.0
-    } else {
-        (l / sum) * 100.0
-    }
-}
-
 fn ratios_for_page(v: &VoteData, page_left: &ItemId, page_right: &ItemId) -> (i32, i32) {
     match (v.a.as_str(), v.b.as_str()) {
         (a, b) if a == page_left.as_str() && b == page_right.as_str() => {
@@ -94,6 +83,37 @@ fn edge_votes(group: &GroupState, left: &ItemId, right: &ItemId) -> Vec<VoteData
         .collect()
 }
 
+/// HUD `data-winner` value: which side the ratio favours on this page.
+fn winner_side(r_left: i32, r_right: i32) -> &'static str {
+    if r_left > r_right {
+        "left"
+    } else if r_right > r_left {
+        "right"
+    } else {
+        "even"
+    }
+}
+
+fn winner_text(r_left: i32, r_right: i32) -> &'static str {
+    match winner_side(r_left, r_right) {
+        "left" => "left wins",
+        "right" => "right wins",
+        _ => "tie",
+    }
+}
+
+/// Map stored ratios to the live slider position (0 = full left, 100 = full right).
+/// Matches `sorter_ui.js`: `left = 100 - v`, `right = v`.
+fn slider_value_from_ratios(r_left: i32, r_right: i32) -> i32 {
+    let l = r_left.max(0) as f64;
+    let r = r_right.max(0) as f64;
+    let sum = l + r;
+    if sum <= 0.0 {
+        return 50;
+    }
+    ((r / sum) * 100.0).round().clamp(0.0, 100.0) as i32
+}
+
 fn vote_edge_history(tree: &GlobalTree, group: &GroupState, left: &ItemId, right: &ItemId) -> Markup {
     let mut votes = edge_votes(group, left, right);
     votes.sort_by(|a, b| b.ts.cmp(&a.ts));
@@ -106,17 +126,26 @@ fn vote_edge_history(tree: &GlobalTree, group: &GroupState, left: &ItemId, right
             h3 class="vote-edge-history-title" {
                 "votes on this pair"
             }
+            p class="muted small vote-edge-legend" {
+                (format!("left: {legend_left} — right: {legend_right}"))
+            }
             ul class="vote-edge-history" {
                 @for v in &votes {
                     @let (r_left, r_right) = ratios_for_page(v, left, right);
-                    @let pct = ratio_pct(r_left, r_right);
+                    @let slider_val = slider_value_from_ratios(r_left, r_right);
+                    @let side = winner_side(r_left, r_right);
+                    @let label = winner_text(r_left, r_right);
                     li class="vote-edge-history-row" {
                         div class="vote-edge-meta" {
                             span class="vote-edge-ratio" { (format!("{}:{}", r_left, r_right)) }
+                            span class="vote-edge-winner muted small" { " · " (label) }
                         }
-                        div class="ratio-bar vote-edge-bar" aria-hidden="true" {
-                            div class="ratio-left" style={(format!("width: {:.3}%;", pct))} {}
-                            div class="ratio-right" style={(format!("width: {:.3}%;", 100.0 - pct))} {}
+                        label class="vote-hud-slider vote-edge-slider" aria-hidden="true" {
+                            input type="range" class="vote-edge-range" min="0" max="100" value=(slider_val)
+                                data-winner=(side)
+                                style={(format!("--vote-slider-pct: {}%;", slider_val))}
+                                disabled
+                                tabindex="-1";
                         }
                     }
                 }
@@ -283,7 +312,6 @@ pub async fn vote_page(
                         span class="vote-compare-vs" { "vs" }
                         (vote_compare_item_card(&tree, &right, "vote-compare-right"))
                     }
-                    (vote_back_nav(&parent))
                     div id="vote-edge-history-region" {
                         (edge_history)
                     }
@@ -308,3 +336,66 @@ pub async fn vote_page(
     )
     .into_response()
 }
+
+#[cfg(test)]
+mod polarity_tests {
+    use super::*;
+    use crate::ranking::ranked_items;
+    use crate::reducer::GlobalTree;
+
+    fn id(s: &str) -> ItemId {
+        ItemId::parse(s).unwrap()
+    }
+
+    /// The page's left number must always equal the vote's weight for the
+    /// item shown on the left, regardless of which order the vote stored a/b.
+    #[test]
+    fn ratios_for_page_orients_to_page_left() {
+        let left = id("left_item");
+        let right = id("right_item");
+
+        // Stored a == page left: keep order.
+        let v1 = VoteData::from_recorded(1, left.as_str(), right.as_str(), 9, 1).unwrap();
+        assert_eq!(ratios_for_page(&v1, &left, &right), (9, 1));
+
+        // Stored a == page right: swap so left stays left.
+        let v2 = VoteData::from_recorded(2, right.as_str(), left.as_str(), 9, 1).unwrap();
+        assert_eq!(ratios_for_page(&v2, &left, &right), (1, 9));
+    }
+
+    #[test]
+    fn winner_side_follows_larger_ratio() {
+        assert_eq!(winner_side(9, 1), "left");
+        assert_eq!(winner_side(1, 9), "right");
+        assert_eq!(winner_side(1, 1), "even");
+    }
+
+    #[test]
+    fn slider_value_matches_hud_mapping() {
+        assert_eq!(slider_value_from_ratios(9, 1), 10);
+        assert_eq!(slider_value_from_ratios(1, 4), 80);
+        assert_eq!(slider_value_from_ratios(1, 1), 50);
+    }
+
+    /// End-to-end polarity invariant: a vote that favours the LEFT item (higher
+    /// `ratio_left`, recorded as the RPC's `a`) must make that item rank #1.
+    /// This is the property the UI must preserve: sliding left => left wins.
+    #[test]
+    fn sliding_left_makes_left_item_win_ranking() {
+        let parent = id("scope");
+        let left = id("left_item");
+        let right = id("right_item");
+
+        // Slider dragged left yields e.g. 9:1 with a = left item.
+        let vote = VoteData::from_recorded(1, left.as_str(), right.as_str(), 9, 1).unwrap();
+        let mut tree = GlobalTree::new();
+        tree.apply_vote(&parent, vote);
+
+        let group = &tree.get(&parent).unwrap().local_ranking;
+        let ranked = ranked_items(group);
+        assert_eq!(
+            ranked[0].item, left,
+            "left item should rank first when ratio favours the left"
+        );
+    }
+}
diff --git a/server/static/sorter.css b/server/static/sorter.css
index 5da967e8bfddc2bc34662fced841860f63f1ef36..bdd3d931365703705be08537a07f3ccaf975d3ea 100644
--- a/server/static/sorter.css
+++ b/server/static/sorter.css
@@ -124,7 +124,7 @@ code {
   z-index: 1;
   box-shadow:
     inset 0 0 0 3px var(--accent),
-    inset 0 0 0 5px color-mix(in oklch, var(--rank-fg) 70%, transparent);
+    inset 0 0 0 5px color-mix(in oklch, var(--rank-fg, var(--fg)) 70%, transparent);
   filter: saturate(1.15) brightness(1.04);
 }
 
@@ -320,7 +320,7 @@ h1 {
   grid-template-columns: var(--vote-ratio-col) minmax(0, 1fr) var(--vote-actions-col);
   gap: 0.5rem 0.65rem;
   align-items: center;
-  --vote-ratio-col: 3.25rem;
+  --vote-ratio-col: 12.5rem;
   --vote-actions-col: 11.5rem;
 }
 
@@ -332,7 +332,7 @@ h1 {
   margin: 0;
   width: var(--vote-ratio-col);
   min-width: var(--vote-ratio-col);
-  text-align: center;
+  text-align: right;
   white-space: nowrap;
 }
 
@@ -474,6 +474,16 @@ h1 {
   --vote-track-muted: color-mix(in oklch, var(--muted) 55%, var(--bg));
 }
 
+/* Center-anchored fill: the accent grows from the midpoint toward the thumb,
+   so the highlighted mass always sits on the *winning* side (the side the
+   thumb was dragged toward). Left winning => accent on the left half. */
+.vote-hud-slider input[type="range"][data-winner="even"]::-webkit-slider-runnable-track {
+  height: 0.65rem;
+  border-radius: 0;
+  border: 2px solid var(--border);
+  background: var(--vote-track-muted);
+}
+
 .vote-hud-slider input[type="range"][data-winner="left"]::-webkit-slider-runnable-track {
   height: 0.65rem;
   border-radius: 0;
@@ -483,7 +493,9 @@ h1 {
     var(--vote-track-muted) 0%,
     var(--vote-track-muted) var(--vote-slider-pct, 50%),
     var(--accent) var(--vote-slider-pct, 50%),
-    var(--accent) 100%
+    var(--accent) 50%,
+    var(--vote-track-muted) 50%,
+    var(--vote-track-muted) 100%
   );
 }
 
@@ -493,7 +505,9 @@ h1 {
   border: 2px solid var(--border);
   background: linear-gradient(
     to right,
-    var(--accent) 0%,
+    var(--vote-track-muted) 0%,
+    var(--vote-track-muted) 50%,
+    var(--accent) 50%,
     var(--accent) var(--vote-slider-pct, 50%),
     var(--vote-track-muted) var(--vote-slider-pct, 50%),
     var(--vote-track-muted) 100%
@@ -513,26 +527,35 @@ h1 {
 }
 
 .vote-hud-slider input[type="range"][data-winner="left"]::-moz-range-track,
-.vote-hud-slider input[type="range"][data-winner="right"]::-moz-range-track {
+.vote-hud-slider input[type="range"][data-winner="right"]::-moz-range-track,
+.vote-hud-slider input[type="range"][data-winner="even"]::-moz-range-track {
   height: 0.65rem;
   border-radius: 0;
   border: 2px solid var(--border);
 }
 
+.vote-hud-slider input[type="range"][data-winner="even"]::-moz-range-track {
+  background: var(--vote-track-muted);
+}
+
 .vote-hud-slider input[type="range"][data-winner="left"]::-moz-range-track {
   background: linear-gradient(
     to right,
     var(--vote-track-muted) 0%,
     var(--vote-track-muted) var(--vote-slider-pct, 50%),
     var(--accent) var(--vote-slider-pct, 50%),
-    var(--accent) 100%
+    var(--accent) 50%,
+    var(--vote-track-muted) 50%,
+    var(--vote-track-muted) 100%
   );
 }
 
 .vote-hud-slider input[type="range"][data-winner="right"]::-moz-range-track {
   background: linear-gradient(
     to right,
-    var(--accent) 0%,
+    var(--vote-track-muted) 0%,
+    var(--vote-track-muted) 50%,
+    var(--accent) 50%,
     var(--accent) var(--vote-slider-pct, 50%),
     var(--vote-track-muted) var(--vote-slider-pct, 50%),
     var(--vote-track-muted) 100%
@@ -573,20 +596,23 @@ h1 {
   margin-bottom: 0.25rem;
 }
 
-.ratio-bar {
-  display: flex;
-  height: 8px;
-  border-radius: 0;
-  overflow: hidden;
-  background: var(--border);
+/* Read-only sliders in vote history — same track/thumb styling as the HUD. */
+.vote-edge-slider {
+  display: block;
+  margin-top: 0.15rem;
 }
 
-.ratio-left {
-  background: var(--accent);
+.vote-edge-slider input[type="range"] {
+  pointer-events: none;
+  cursor: default;
+}
+
+.vote-edge-slider input[type="range"]:disabled {
+  opacity: 1;
 }
 
-.ratio-right {
-  background: var(--muted);
+.vote-edge-legend {
+  margin: 0 0 0.5rem;
 }
 
 @media (max-width: 900px) {
diff --git a/server/static/sorter_ui.js b/server/static/sorter_ui.js
index f665b45f4fd4771427dc4c37e563e4976873beee..5d6d765f69f301722e59248c76e919043559fb78 100644
--- a/server/static/sorter_ui.js
+++ b/server/static/sorter_ui.js
@@ -138,6 +138,10 @@
     function update() {
       var v = parseInt(slider.value, 10);
       if (!Number.isFinite(v)) v = 50;
+      // Slider position drives the colored fill (a center-anchored bar that
+      // grows toward whichever side is winning — see sorter.css). Sliding the
+      // thumb left raises the left number; left winning keeps the accent mass
+      // on the left, matching the "votes on this pair" history bars.
       slider.style.setProperty('--vote-slider-pct', v + '%');
       slider.setAttribute('aria-valuenow', String(v));
       var left = Math.max(1, 100 - v);
@@ -147,8 +151,12 @@
       right = right / divisor;
       if (leftInput) leftInput.value = String(left);
       if (rightInput) rightInput.value = String(right);
-      if (ratioDisplay) ratioDisplay.textContent = left + ':' + right;
-      slider.dataset.winner = left >= right ? 'left' : 'right';
+      var winner = left > right ? 'left' : (right > left ? 'right' : 'even');
+      slider.dataset.winner = winner;
+      if (ratioDisplay) {
+        var label = winner === 'even' ? 'tie' : (winner + ' wins');
+        ratioDisplay.textContent = left + ':' + right + ' \u00b7 ' + label;
+      }
     }
     slider.addEventListener('input', update);
     update();