{"messages":[{"content":"You are a constitutional council ranking individual git commits for ownership allocation.\n\nCompare these two commits. Decide which contributed more lasting value to the project.\n\nJudge substance, not spectacle:\n- Prefer correct, lasting design and real bugfixes over churn, formatting, renames, or generated noise.\n- Prefer clarity and necessity over sheer line count. A small precise change can beat a large diffuse one.\n- Do not favor a side merely because its patch is longer or noisier.\n- Weight what the change does for the project, not the contributor's name.\n\nReturn ONLY a JSON object: {\"winner\": \"A\" or \"B\", \"ratio\": \"N:M\", \"explanation\": \"...\"}\nThe explanation must cite concrete differences in the patches (1-3 sentences).\n\nSide A — contributor: tommy-mor\nSide A — commit message:\n[07715165] nice\n\nSide A — unified diff (full patch):\ndiff --git a/server/src/api/ui_html.rs b/server/src/api/ui_html.rs\nindex c3c62a76f424010d77a6090c84dd0b82098f573e..da2536112faea313352624cf2ce0ddd0ab3377c1 100644\n--- a/server/src/api/ui_html.rs\n+++ b/server/src/api/ui_html.rs\n@@ -6,7 +6,7 @@ use axum::{\n use std::collections::HashMap;\n \n use crate::{\n-    html::{demo_counter_panel, js_string_literal, ranking_panel, JsBuilder},\n+    html::{js_string_literal, ranking_panel, JsBuilder},\n     parser::parse_reddit_url,\n     parser_render::parser_panel_morph,\n     state::AppState,\n@@ -35,13 +35,6 @@ pub async fn post_ui_html(\n     };\n \n     match action {\n-        HtmlUiAction::BumpDemoCounter => {\n-            let count = state.bump_demo_counter().await;\n-            let panel = demo_counter_panel(count, state.event_log.path().to_string_lossy().as_ref());\n-            JsBuilder::new()\n-                .morph_selector(\"#demo-counter-panel\", panel)\n-                .into_response()\n-        }\n         HtmlUiAction::RecordVote {\n             a,\n             b,\n@@ -54,8 +47,8 @@ pub async fn post_ui_html(\n             {\n                 return ui_js_warn(&e).into_response();\n             }\n-            let mut group = state.group.write().await;\n-            let panel = ranking_panel(&mut group);\n+            let group = state.group.read().await;\n+            let panel = ranking_panel(&group);\n             JsBuilder::new()\n                 .morph_selector(\"#ranking-panel\", panel)\n                 .into_response()\n@@ -87,20 +80,6 @@ mod tests {\n         assert!(matches!(err, HtmlUiParseError::MissingRpc));\n     }\n \n-    #[test]\n-    fn bump_action_deserializes() {\n-        let template = serde_json::json!({ \"action\": \"bump_demo_counter\" });\n-        let mut form = HashMap::new();\n-        form.insert(\n-            UI_RPC_FIELD.to_string(),\n-            serde_json::to_string(&template).unwrap(),\n-        );\n-        assert_eq!(\n-            parse_html_ui_from_form(&form).unwrap(),\n-            HtmlUiAction::BumpDemoCounter\n-        );\n-    }\n-\n     #[test]\n     fn record_vote_action_deserializes() {\n         let template = serde_json::json!({\ndiff --git a/server/src/events.rs b/server/src/events.rs\nindex b969242534e184d4f0a689543a479670b08a18df..eff80aef0257f706d2341f666e63d6a3d921bf6e 100644\n--- a/server/src/events.rs\n+++ b/server/src/events.rs\n@@ -5,8 +5,6 @@ use serde::{Deserialize, Serialize};\n pub enum Event {\n     /// Page view recorded (path → counter in views.json).\n     ViewRecorded { path: String, ts: i64 },\n-    /// Demo counter bump from `POST /ui` (persisted in the single JSONL log).\n-    DemoCounterBumped { ts: i64, value: u64 },\n     /// Pairwise comparison vote (replayed into [`crate::reducer::GroupState`] on boot).\n     VoteRecorded {\n         ts: i64,\ndiff --git a/server/src/html/mod.rs b/server/src/html/mod.rs\nindex 5b1d0b5a887d89e7e80796aa7a6c8ed5baaf2782..d69ed962b5c8625bc83c933b1825f2cc1d0868e2 100644\n--- a/server/src/html/mod.rs\n+++ b/server/src/html/mod.rs\n@@ -13,7 +13,7 @@ use crate::{\n     form_template::template_json_compact,\n     parser_action::ParserAction,\n     parser_render::parser_panel,\n-    ranking::ranked_items,\n+    ranking::ranked_items_cached,\n     reducer::GroupState,\n     state::AppState,\n     ui_action::UI_RPC_FIELD,\n@@ -199,10 +199,8 @@ fn layout(title: &str, body: Markup, views: u64, theme: &str, theme_next: &str)\n     }\n }\n \n-pub fn ranking_panel(group: &mut GroupState) -> Markup {\n-    const MAX_ITERS: usize = 10_000;\n-    const TOL: f64 = 1e-8;\n-    let items = ranked_items(group, MAX_ITERS, TOL);\n+pub fn ranking_panel(group: &GroupState) -> Markup {\n+    let items = ranked_items_cached(group);\n     html! {\n         section id=\"ranking-panel\" class=\"demo-panel\" {\n             h2 { \"Ranking\" }\n@@ -260,35 +258,6 @@ pub fn vote_panel() -> Markup {\n }\n \n \n-pub fn demo_counter_panel(count: u64, event_log_path: &str) -> Markup {\n-    let rpc = template_json_compact(&serde_json::json!({ \"action\": \"bump_demo_counter\" }))\n-        .expect(\"rpc json\");\n-    html! {\n-        section id=\"demo-counter-panel\" class=\"demo-panel\" {\n-            h1 { \"sorter2\" }\n-            p class=\"muted\" {\n-                \"Pairwise ranking scaffold — votes persist to JSONL and replay on boot.\"\n-            }\n-            p class=\"demo-count\" {\n-                strong { \"Counter: \" }\n-                span id=\"demo-count-value\" { (count) }\n-            }\n-            p class=\"muted small\" {\n-                \"Event log: \" code { (event_log_path) }\n-            }\n-            form method=\"post\" action=\"/ui\" id=\"demo-bump-form\" {\n-                input type=\"hidden\" name=(UI_RPC_FIELD) value=(rpc);\n-                button type=\"submit\" class=\"btn-primary\" { \"Bump (POST /ui → eval JS)\" }\n-            }\n-            p class=\"muted small\" {\n-                \"Uses hidden \"\n-                code { \"__rpc__\" }\n-                \" JSON + Idiomorph morph — no full page reload.\"\n-            }\n-        }\n-    }\n-}\n-\n pub async fn home(\n     State(state): State<AppState>,\n     jar: CookieJar,\n@@ -297,16 +266,15 @@ pub async fn home(\n     let path = uri.path().to_string();\n     state.views.increment(path.clone());\n     let views = state.views.get_views(&path);\n-    let count = *state.demo_counter.read().await;\n     let theme = theme_from_jar(&jar);\n     let theme_next = theme_next_from_uri(&uri);\n-    let mut group = state.group.write().await;\n+    let group = state.group.read().await;\n     let empty_action = ParserAction::suggest(String::new(), None);\n     let body = html! {\n+        h1 { \"sorter2\" }\n         (parser_panel(\"\", &empty_action))\n         (vote_panel())\n-        (ranking_panel(&mut group))\n-        (demo_counter_panel(count, state.event_log.path().to_string_lossy().as_ref()))\n+        (ranking_panel(&group))\n     };\n     layout(\"sorter2\", body, views, theme, &theme_next)\n }\ndiff --git a/server/src/lib.rs b/server/src/lib.rs\nindex 6716c5b282e7980a7a0f03d63ad8b25eda61cc55..fa423640d598f4ba97a5885d228e78d7b97f7a22 100644\n--- a/server/src/lib.rs\n+++ b/server/src/lib.rs\n@@ -9,6 +9,7 @@ pub mod parser_render;\n pub mod path_types;\n pub mod ranking;\n pub mod reducer;\n+pub mod settlement;\n pub mod state;\n pub mod ui_action;\n pub mod views;\ndiff --git a/server/src/ranking.rs b/server/src/ranking.rs\nindex 89d3280126a8d8f841721ce8cb63ff735d68752a..2d706762792ba9239bb3f1c2e4974a2fde908013 100644\n--- a/server/src/ranking.rs\n+++ b/server/src/ranking.rs\n@@ -91,6 +91,11 @@ pub fn compute_group_ranking(group: &mut GroupState, max_iters: usize, tol: f64)\n \n pub fn ranked_items(group: &mut GroupState, max_iters: usize, tol: f64) -> Vec<RankedItem> {\n     compute_group_ranking(group, max_iters, tol);\n+    ranked_items_cached(group)\n+}\n+\n+/// Read cached scores without recomputing (HTTP fast path).\n+pub fn ranked_items_cached(group: &GroupState) -> Vec<RankedItem> {\n     let mut items: Vec<RankedItem> = group\n         .idx_to_item\n         .iter()\n@@ -105,7 +110,12 @@ pub fn ranked_items(group: &mut GroupState, max_iters: usize, tol: f64) -> Vec<R\n     items\n }\n \n-fn compute_scores_from_edges(n: usize, edges: impl Iterator<Item = ((usize, usize), f64)>, max_iters: usize, tol: f64) -> Vec<f64> {\n+pub fn compute_scores_from_edges(\n+    n: usize,\n+    edges: impl Iterator<Item = ((usize, usize), f64)>,\n+    max_iters: usize,\n+    tol: f64,\n+) -> Vec<f64> {\n     if n == 0 {\n         return vec![];\n     }\ndiff --git a/server/src/settlement.rs b/server/src/settlement.rs\nnew file mode 100644\nindex 0000000000000000000000000000000000000000..1f722ceaea62cda22c28ab71551f259fbf049b81\n--- /dev/null\n+++ b/server/src/settlement.rs\n@@ -0,0 +1,114 @@\n+use std::sync::Arc;\n+\n+use tokio::sync::{mpsc, oneshot, RwLock};\n+\n+use crate::{\n+    event_log::EventLog,\n+    events::Event,\n+    ranking::compute_scores_from_edges,\n+    reducer::{GroupState, VoteData},\n+};\n+\n+const MAX_ITERS: usize = 10_000;\n+const TOL: f64 = 1e-8;\n+\n+pub struct SettlementCommand {\n+    pub vote: VoteData,\n+    pub event: Event,\n+    pub reply: oneshot::Sender<Result<(), String>>,\n+}\n+\n+#[derive(Clone)]\n+pub struct SettlementClient {\n+    tx: mpsc::Sender<SettlementCommand>,\n+}\n+\n+impl SettlementClient {\n+    pub fn spawn(group: Arc<RwLock<GroupState>>, event_log: Arc<EventLog>) -> Self {\n+        let (tx, rx) = mpsc::channel(64);\n+        tokio::spawn(settlement_worker(rx, group, event_log));\n+        Self { tx }\n+    }\n+\n+    pub async fn record_vote(&self, vote: VoteData, event: Event) -> Result<(), String> {\n+        let (reply, rx) = oneshot::channel();\n+        self.tx\n+            .send(SettlementCommand {\n+                vote,\n+                event,\n+                reply,\n+            })\n+            .await\n+            .map_err(|_| \"settlement worker stopped\".to_string())?;\n+        rx.await\n+            .map_err(|_| \"settlement worker stopped\".to_string())?\n+    }\n+}\n+\n+async fn settlement_worker(\n+    mut rx: mpsc::Receiver<SettlementCommand>,\n+    group: Arc<RwLock<GroupState>>,\n+    event_log: Arc<EventLog>,\n+) {\n+    while let Some(first) = rx.recv().await {\n+        let mut batch = vec![first];\n+        while let Ok(more) = rx.try_recv() {\n+            batch.push(more);\n+        }\n+\n+        let mut disk_err: Option<String> = None;\n+        for cmd in &batch {\n+            if let Err(e) = event_log.append(&cmd.event).await {\n+                disk_err = Some(e.to_string());\n+                break;\n+            }\n+        }\n+\n+        if let Some(err) = disk_err {\n+            for cmd in batch {\n+                let _ = cmd.reply.send(Err(err.clone()));\n+            }\n+            continue;\n+        }\n+\n+        let (edges, n) = {\n+            let mut w = group.write().await;\n+            for cmd in &batch {\n+                w.apply_vote(cmd.vote.clone());\n+            }\n+            (w.edges.clone(), w.idx_to_item.len())\n+        };\n+\n+        let new_scores = compute_scores_from_edges(\n+            n,\n+            edges.iter().map(|(&k, &v)| (k, v)),\n+            MAX_ITERS,\n+            TOL,\n+        );\n+\n+        {\n+            let mut w = group.write().await;\n+            w.cached_scores = new_scores;\n+            w.dirty = false;\n+        }\n+\n+        for cmd in batch {\n+            let _ = cmd.reply.send(Ok(()));\n+        }\n+    }\n+}\n+\n+/// Compute ranking cache from current in-memory edges (startup replay only).\n+pub fn warm_ranking_cache(group: &mut GroupState) {\n+    if !group.dirty {\n+        return;\n+    }\n+    let n = group.idx_to_item.len();\n+    group.cached_scores = compute_scores_from_edges(\n+        n,\n+        group.edges.iter().map(|(&k, &v)| (k, v)),\n+        MAX_ITERS,\n+        TOL,\n+    );\n+    group.dirty = false;\n+}\ndiff --git a/server/src/state.rs b/server/src/state.rs\nindex 8ec9902e2ecc31cf8208f7ad6365891dc5537eed..1922541a4064c2de1df2d993a461cae783320e05 100644\n--- a/server/src/state.rs\n+++ b/server/src/state.rs\n@@ -6,6 +6,7 @@ use crate::{\n     event_log::EventLog,\n     events::Event,\n     reducer::{GroupState, VoteData},\n+    settlement::{warm_ranking_cache, SettlementClient},\n     views::ViewStore,\n };\n \n@@ -38,8 +39,8 @@ pub struct AppState {\n     pub cfg: Arc<AppConfig>,\n     pub event_log: Arc<EventLog>,\n     pub views: ViewStore,\n-    pub demo_counter: Arc<RwLock<u64>>,\n     pub group: Arc<RwLock<GroupState>>,\n+    settlement: SettlementClient,\n }\n \n impl AppState {\n@@ -48,14 +49,10 @@ impl AppState {\n         let views_path = format!(\"{}/views.json\", cfg.data_dir);\n         let views = ViewStore::new(&views_path);\n \n-        let mut demo_counter: u64 = 0;\n         let mut group = GroupState::new();\n         if let Ok((events, _)) = event_log.load_all().await {\n             for ev in events {\n                 match ev {\n-                    Event::DemoCounterBumped { value, .. } => {\n-                        demo_counter = demo_counter.max(value);\n-                    }\n                     Event::VoteRecorded {\n                         ts,\n                         a,\n@@ -74,30 +71,20 @@ impl AppState {\n             }\n         }\n \n+        warm_ranking_cache(&mut group);\n+\n+        let group = Arc::new(RwLock::new(group));\n+        let settlement = SettlementClient::spawn(group.clone(), event_log.clone());\n+\n         Self {\n             cfg: Arc::new(cfg),\n             event_log,\n             views,\n-            demo_counter: Arc::new(RwLock::new(demo_counter)),\n-            group: Arc::new(RwLock::new(group)),\n+            group,\n+            settlement,\n         }\n     }\n \n-    pub async fn bump_demo_counter(&self) -> u64 {\n-        let mut guard = self.demo_counter.write().await;\n-        *guard += 1;\n-        let value = *guard;\n-        drop(guard);\n-\n-        let ts = crate::html::now_ms();\n-        let _ = self\n-            .event_log\n-            .append(&Event::DemoCounterBumped { ts, value })\n-            .await;\n-\n-        value\n-    }\n-\n     pub async fn record_vote(\n         &self,\n         a: &str,\n@@ -109,23 +96,14 @@ impl AppState {\n         let vote = VoteData::from_recorded(ts, a, b, ratio_left, ratio_right)\n             .ok_or_else(|| \"invalid vote: need two distinct non-empty items\".to_string())?;\n \n-        {\n-            let mut group = self.group.write().await;\n-            group.apply_vote(vote.clone());\n-        }\n-\n-        let _ = self\n-            .event_log\n-            .append(&Event::VoteRecorded {\n-                ts,\n-                a: vote.a.as_str().to_string(),\n-                b: vote.b.as_str().to_string(),\n-                ratio_left: vote.ratio_left,\n-                ratio_right: vote.ratio_right,\n-            })\n-            .await\n-            .map_err(|e| e.to_string())?;\n+        let event = Event::VoteRecorded {\n+            ts,\n+            a: vote.a.as_str().to_string(),\n+            b: vote.b.as_str().to_string(),\n+            ratio_left: vote.ratio_left,\n+            ratio_right: vote.ratio_right,\n+        };\n \n-        Ok(())\n+        self.settlement.record_vote(vote, event).await\n     }\n }\ndiff --git a/server/src/ui_action.rs b/server/src/ui_action.rs\nindex 1d488e1ad1d8fd81bd9d016d69255adfe9b22fc8..5d94c84113607b3bcd8d31d03ef5b8e1b87b67a7 100644\n--- a/server/src/ui_action.rs\n+++ b/server/src/ui_action.rs\n@@ -12,8 +12,6 @@ pub const UI_RPC_FIELD: &str = \"__rpc__\";\n #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]\n #[serde(tag = \"action\", rename_all = \"snake_case\")]\n pub enum HtmlUiAction {\n-    /// Demo: morph `#demo-counter-panel` after bumping the persisted counter.\n-    BumpDemoCounter,\n     /// Record a pairwise vote and morph `#ranking-panel`.\n     RecordVote {\n         a: String,\n@@ -52,18 +50,6 @@ pub fn parse_html_ui_from_form(\n mod tests {\n     use super::*;\n \n-    #[test]\n-    fn bump_demo_counter_round_trip() {\n-        let template = serde_json::json!({ \"action\": \"bump_demo_counter\" });\n-        let mut form = HashMap::new();\n-        form.insert(\n-            UI_RPC_FIELD.to_string(),\n-            serde_json::to_string(&template).unwrap(),\n-        );\n-        let a = parse_html_ui_from_form(&form).unwrap();\n-        assert_eq!(a, HtmlUiAction::BumpDemoCounter);\n-    }\n-\n     #[test]\n     fn record_vote_round_trip_with_form_holes() {\n         let template = serde_json::json!({\ndiff --git a/server/tests/integration_health.rs b/server/tests/integration_health.rs\nindex 8a58bc14aac68c779e7ce4ffa57d27b3220e9953..1d816e008b9bf629967e3b3c786c41afefc284e3 100644\n--- a/server/tests/integration_health.rs\n+++ b/server/tests/integration_health.rs\n@@ -38,7 +38,7 @@ async fn healthz_ok() {\n }\n \n #[tokio::test]\n-async fn home_has_demo_panel() {\n+async fn home_has_main_panels() {\n     let (addr, _tmp) = start_test_server().await;\n     let client = reqwest::Client::new();\n     let html = client\ndiff --git a/server/tests/integration_ui.rs b/server/tests/integration_ui.rs\nindex bee79407dec120699a083f1a75adf9291e207fc7..7ede46d681fefbe25b1d98fc33520a185515eb1c 100644\n--- a/server/tests/integration_ui.rs\n+++ b/server/tests/integration_ui.rs\n@@ -25,33 +25,6 @@ async fn start_test_server() -> (SocketAddr, TempDir) {\n     (addr, tmp)\n }\n \n-#[tokio::test]\n-async fn post_ui_bump_returns_javascript_morph() {\n-    let (addr, tmp) = start_test_server().await;\n-    let rpc = serde_json::json!({ \"action\": \"bump_demo_counter\" }).to_string();\n-    let mut form = HashMap::new();\n-    form.insert(UI_RPC_FIELD.to_string(), rpc);\n-\n-    let client = reqwest::Client::new();\n-    let body = client\n-        .post(format!(\"http://{addr}/ui\"))\n-        .form(&form)\n-        .send()\n-        .await\n-        .unwrap()\n-        .text()\n-        .await\n-        .unwrap();\n-\n-    assert!(body.contains(\"Idiomorph.morph\"));\n-    assert!(body.contains(\"demo-counter-panel\"));\n-    assert!(body.contains(\"Counter:\"));\n-\n-    let log_path = tmp.path().join(\"events.jsonl\");\n-    let log = std::fs::read_to_string(log_path).unwrap();\n-    assert!(log.contains(\"demo_counter_bumped\"));\n-}\n-\n #[tokio::test]\n async fn post_ui_record_vote_morphs_ranking_and_persists() {\n     let (addr, tmp) = start_test_server().await;\n@@ -90,8 +63,8 @@ async fn post_ui_record_vote_morphs_ranking_and_persists() {\n         port: 0,\n     };\n     let state = create_app_state(cfg).await;\n-    let mut group = state.group.write().await;\n-    let ranked = sorter2_server::ranking::ranked_items(&mut group, 10_000, 1e-8);\n+    let group = state.group.read().await;\n+    let ranked = sorter2_server::ranking::ranked_items_cached(&group);\n     assert_eq!(ranked.len(), 2);\n     assert_eq!(ranked[0].item.as_str(), \"alpha\");\n }\ndiff --git a/test/smoke.clj b/test/smoke.clj\nindex b332324743b58baf3fe96d7477353749f137feae..11887c48282088e140d823a88ba616f6325835b3 100644\n--- a/test/smoke.clj\n+++ b/test/smoke.clj\n@@ -26,7 +26,7 @@\n             false))))))\n \n (deftest http-smoke-against-running-server\n-  (testing \"build, start, healthz, home contains RPC demo\"\n+  (testing \"build, start, healthz, home contains main panels\"\n     (let [root (repo-root)\n           data-dir (.getAbsolutePath (doto (io/file (System/getProperty \"java.io.tmpdir\")\n                                                    (str \"sorter2-smoke-\" (System/currentTimeMillis)))\n\n\nSide B — contributor: tommy-mor\nSide B — commit message:\n[2bc302c3] refactor\n\nSide B — unified diff (full patch):\ndiff --git a/server/src/api/ui_html.rs b/server/src/api/ui_html.rs\nindex 06001212820101e0cc953d3687dea64f85e60787..d2f9769108def7ca2c5857aec8b4319426188a66 100644\n--- a/server/src/api/ui_html.rs\n+++ b/server/src/api/ui_html.rs\n@@ -47,7 +47,7 @@ pub async fn post_ui_html(\n             ratio_left,\n             ratio_right,\n             scope,\n-            next,\n+            vote_compare,\n         } => {\n             let parent = parent_from_scope(&scope);\n             if let Err(e) = state\n@@ -57,14 +57,12 @@ pub async fn post_ui_html(\n                 return ui_js_warn(&e).into_response();\n             }\n             let tree = state.tree.read().await;\n-            if !next.trim().is_empty() {\n+            if vote_compare {\n+                let left = parse_item_param(&a);\n+                let right = parse_item_param(&b);\n+                let morph = crate::html::vote::vote_recorded_morph(&tree, &parent, &left, &right);\n                 drop(tree);\n-                return JsBuilder::new()\n-                    .raw(&format!(\n-                        \"window.location.href={};\",\n-                        js_string_literal(next.trim())\n-                    ))\n-                    .into_response();\n+                return morph.into_response();\n             }\n             let empty = crate::reducer::NodeState::default();\n             let node = tree.get(&parent).unwrap_or(&empty);\n@@ -137,7 +135,7 @@ mod tests {\n                 ratio_left: 3,\n                 ratio_right: 1,\n                 scope: String::new(),\n-                next: String::new(),\n+                vote_compare: false,\n             }\n         );\n     }\ndiff --git a/server/src/html/mod.rs b/server/src/html/mod.rs\nindex 61cdbc094819ddedb755572c59456ec0d6617619..cd578a5fea46a9a1d49e238d08a80c2caf18708d 100644\n--- a/server/src/html/mod.rs\n+++ b/server/src/html/mod.rs\n@@ -65,6 +65,15 @@ impl JsBuilder {\n         self\n     }\n \n+    pub(crate) fn morph_inner_selector(mut self, selector: &str, markup: Markup) -> Self {\n+        let html = js_string_literal(&markup.into_string());\n+        self.snippets.push(format!(\n+            \"var __el = document.querySelector({sel}); if (__el) {{ Idiomorph.morph(__el, {html}, {{ morphStyle: 'innerHTML' }}); }}\",\n+            sel = js_string_literal(selector),\n+        ));\n+        self\n+    }\n+\n     pub(crate) fn raw(mut self, js: &str) -> Self {\n         if !js.is_empty() {\n             self.snippets.push(js.to_string());\ndiff --git a/server/src/html/vote.rs b/server/src/html/vote.rs\nnew file mode 100644\nindex 0000000000000000000000000000000000000000..89ed621ad861214e147add2062224fc4137ff8ad\n--- /dev/null\n+++ b/server/src/html/vote.rs\n@@ -0,0 +1,306 @@\n+//! Pairwise vote UI — `/vote?parent=` with optional `left` / `right`.\n+\n+use axum::{\n+    extract::{Query, State},\n+    response::{Html, IntoResponse},\n+};\n+use maud::{html, Markup};\n+use serde::Deserialize;\n+\n+use crate::{\n+    form_template::template_json_compact,\n+    html::JsBuilder,\n+    pair::{children_of, resolve_pair, suggest_next_pair_in_pool},\n+    path_types::ItemId,\n+    reducer::{GlobalTree, GroupState, NodeState, VoteData},\n+    state::{parse_item_param, AppState},\n+    ui_action::UI_RPC_FIELD,\n+};\n+\n+use super::{breadcrumb_path, item_href, layout};\n+\n+#[derive(Debug, Deserialize)]\n+pub struct VoteQuery {\n+    pub parent: String,\n+    #[serde(default)]\n+    pub left: Option<String>,\n+    #[serde(default)]\n+    pub right: Option<String>,\n+}\n+\n+pub fn vote_href(parent: &ItemId) -> String {\n+    format!(\n+        \"/vote?parent={}\",\n+        urlencoding::encode(parent.as_str())\n+    )\n+}\n+\n+fn vote_compare_href(parent: &ItemId, left: &ItemId, right: &ItemId) -> String {\n+    format!(\n+        \"/vote?parent={}&left={}&right={}\",\n+        urlencoding::encode(parent.as_str()),\n+        urlencoding::encode(left.as_str()),\n+        urlencoding::encode(right.as_str()),\n+    )\n+}\n+\n+fn display_label(id: &ItemId) -> String {\n+    id.segments()\n+        .last()\n+        .map_or(\"item\".into(), |v| v.to_string())\n+}\n+\n+fn child_title(tree: &GlobalTree, id: &ItemId) -> String {\n+    tree.get(id)\n+        .and_then(|n| n.data.as_ref())\n+        .map(|d| d.title.clone())\n+        .unwrap_or_else(|| display_label(id))\n+}\n+\n+fn ratio_pct(ratio_left: i32, ratio_right: i32) -> f64 {\n+    let l = ratio_left.max(0) as f64;\n+    let r = ratio_right.max(0) as f64;\n+    let sum = l + r;\n+    if sum <= 0.0 {\n+        50.0\n+    } else {\n+        (l / sum) * 100.0\n+    }\n+}\n+\n+fn ratios_for_page(v: &VoteData, page_left: &ItemId, page_right: &ItemId) -> (i32, i32) {\n+    match (v.a.as_str(), v.b.as_str()) {\n+        (a, b) if a == page_left.as_str() && b == page_right.as_str() => {\n+            (v.ratio_left, v.ratio_right)\n+        }\n+        (a, b) if a == page_right.as_str() && b == page_left.as_str() => {\n+            (v.ratio_right, v.ratio_left)\n+        }\n+        _ => (v.ratio_left, v.ratio_right),\n+    }\n+}\n+\n+fn edge_votes(group: &GroupState, left: &ItemId, right: &ItemId) -> Vec<VoteData> {\n+    group\n+        .recent_votes\n+        .iter()\n+        .filter(|v| {\n+            (v.a.as_str() == left.as_str() && v.b.as_str() == right.as_str())\n+                || (v.a.as_str() == right.as_str() && v.b.as_str() == left.as_str())\n+        })\n+        .cloned()\n+        .collect()\n+}\n+\n+fn vote_edge_history(tree: &GlobalTree, group: &GroupState, left: &ItemId, right: &ItemId) -> Markup {\n+    let mut votes = edge_votes(group, left, right);\n+    votes.sort_by(|a, b| b.ts.cmp(&a.ts));\n+    let legend_left = child_title(tree, left);\n+    let legend_right = child_title(tree, right);\n+    html! {\n+        @if votes.is_empty() {\n+            p class=\"muted vote-edge-empty\" { \"no votes on this pair yet\" }\n+        } @else {\n+            h3 class=\"vote-edge-history-title\" {\n+                \"votes on this pair\"\n+                span class=\"vote-edge-history-axis muted\" { \" · \" (legend_left) \" : \" (legend_right) }\n+            }\n+            ul class=\"vote-edge-history\" {\n+                @for v in &votes {\n+                    @let (r_left, r_right) = ratios_for_page(v, left, right);\n+                    @let pct = ratio_pct(r_left, r_right);\n+                    li class=\"vote-edge-history-row\" {\n+                        div class=\"vote-edge-meta\" {\n+                            span class=\"vote-edge-ratio\" { (format!(\"{}:{}\", r_left, r_right)) }\n+                        }\n+                        div class=\"ratio-bar vote-edge-bar\" aria-hidden=\"true\" {\n+                            div class=\"ratio-left\" style={(format!(\"width: {:.3}%;\", pct))} {}\n+                            div class=\"ratio-right\" style={(format!(\"width: {:.3}%;\", 100.0 - pct))} {}\n+                        }\n+                    }\n+                }\n+            }\n+        }\n+    }\n+}\n+\n+fn vote_back_nav(parent: &ItemId) -> Markup {\n+    html! {\n+        div class=\"vote-compare-nav\" {\n+            a class=\"vote-compare-back muted\" href=(item_href(parent)) { \"← back to \" (display_label(parent)) }\n+        }\n+    }\n+}\n+\n+fn vote_compare_actions(parent: &ItemId, next: Option<&(ItemId, ItemId)>) -> Markup {\n+    let next_href = next.map(|(l, r)| vote_compare_href(parent, l, r));\n+    html! {\n+        div id=\"vote-compare-actions\" class=\"vote-compare-actions\" {\n+            button type=\"submit\" class=\"btn-primary\" data-testid=\"vote-post\" { \"post vote\" }\n+            @if let Some(href) = &next_href {\n+                a class=\"btn-secondary vote-compare-next\" data-testid=\"vote-next-pair\" href=(href) { \"next pair\" }\n+            } @else {\n+                span class=\"btn-secondary vote-compare-next is-disabled\" { \"no next pair\" }\n+            }\n+        }\n+    }\n+}\n+\n+/// After recording a vote on the compare page: refresh edge history and next-pair link.\n+pub(crate) fn vote_recorded_morph(\n+    tree: &GlobalTree,\n+    parent: &ItemId,\n+    left: &ItemId,\n+    right: &ItemId,\n+) -> JsBuilder {\n+    let pool = children_of(tree, parent);\n+    let empty = NodeState::default();\n+    let group = tree\n+        .get(parent)\n+        .unwrap_or(&empty)\n+        .local_ranking\n+        .clone();\n+    let edge_history = vote_edge_history(tree, &group, left, right);\n+    let next_pair = suggest_next(&group, left, right, &pool);\n+    let actions = vote_compare_actions(parent, next_pair.as_ref());\n+    JsBuilder::new()\n+        .morph_inner_selector(\"#vote-edge-history-region\", edge_history)\n+        .morph_selector(\"#vote-compare-actions\", actions)\n+}\n+\n+fn vote_compare_item_card(tree: &GlobalTree, item: &ItemId, side_class: &str) -> Markup {\n+    let href = item_href(item);\n+    let title = child_title(tree, item);\n+    html! {\n+        div class=(format!(\"vote-compare-side {side_class}\")) {\n+            a class=(format!(\"vote-compare-item {side_class}\")) href=(href) {\n+                @if let Some(row) = crate::render::reddit::child_row_markup(tree, item, &href) {\n+                    (row)\n+                } @else {\n+                    strong { (title) }\n+                }\n+            }\n+            @if let Some(node) = tree.get(item) {\n+                @if crate::render::reddit::is_reddit_post(item) {\n+                    @if let Some(data) = &node.data {\n+                        @if let Some(src) = data.image_url.as_ref().or(data.thumb_url.as_ref()) {\n+                            figure class=\"vote-compare-figure\" {\n+                                img class=\"vote-compare-image\" src=(src) alt=\"\" loading=\"lazy\";\n+                            }\n+                        }\n+                        @if let Some(author) = &data.author {\n+                            p class=\"muted small\" { \"by \" (author) }\n+                        }\n+                    }\n+                } @else if let Some(data) = &node.data {\n+                    @if let Some(body) = &data.body_html {\n+                        div class=\"vote-compare-item-body\" {\n+                            (maud::PreEscaped(body))\n+                        }\n+                    }\n+                }\n+            }\n+        }\n+    }\n+}\n+\n+\n+fn suggest_next(group: &GroupState, left: &ItemId, right: &ItemId, pool: &[ItemId]) -> Option<(ItemId, ItemId)> {\n+    suggest_next_pair_in_pool(group, pool, Some((left, right)))\n+}\n+\n+pub async fn vote_page(\n+    State(state): State<AppState>,\n+    Query(q): Query<VoteQuery>,\n+) -> impl IntoResponse {\n+    let parent = parse_item_param(&q.parent);\n+    let left_param = q.left.as_deref().map(parse_item_param);\n+    let right_param = q.right.as_deref().map(parse_item_param);\n+\n+    let tree = state.tree.read().await;\n+    let empty = NodeState::default();\n+    let parent_node = tree.get(&parent).unwrap_or(&empty);\n+\n+    let (left, right) = match resolve_pair(\n+        &tree,\n+        &parent,\n+        left_param.as_ref(),\n+        right_param.as_ref(),\n+    ) {\n+        Ok(p) => p,\n+        Err(e) => {\n+            let (msg, status) = e.status_message();\n+            return (status, msg).into_response();\n+        }\n+    };\n+\n+    let pool = children_of(&tree, &parent);\n+    let group = &parent_node.local_ranking;\n+    let next_pair = suggest_next(group, &left, &right, &pool);\n+    let edge_history = vote_edge_history(&tree, group, &left, &right);\n+\n+    let rpc_json = template_json_compact(&serde_json::json!({\n+        \"action\": \"record_vote\",\n+        \"a\": left.as_str(),\n+        \"b\": right.as_str(),\n+        \"ratio_left\": {\"$form:i32\": \"ratio_left\"},\n+        \"ratio_right\": {\"$form:i32\": \"ratio_right\"},\n+        \"scope\": parent.as_str(),\n+        \"vote_compare\": true,\n+    }))\n+    .expect(\"vote rpc json\");\n+\n+    let title = format!(\n+        \"vote — {} vs {}\",\n+        child_title(&tree, &left),\n+        child_title(&tree, &right)\n+    );\n+\n+    let body = html! {\n+        section class=\"vote-compare-shell\" {\n+            h1 { \"compare\" }\n+            (breadcrumb_path(&parent))\n+            p class=\"muted vote-compare-scope\" {\n+                \"ranking children of \"\n+                a href=(item_href(&parent)) { (child_title(&tree, &parent)) }\n+            }\n+            div class=\"vote-compare-pair\" {\n+                (vote_compare_item_card(&tree, &left, \"vote-compare-left\"))\n+                span class=\"vote-compare-vs\" { \"vs\" }\n+                (vote_compare_item_card(&tree, &right, \"vote-compare-right\"))\n+            }\n+            (vote_back_nav(&parent))\n+            div id=\"vote-edge-history-region\" {\n+                (edge_history)\n+            }\n+            form id=\"vote-compare-form\" method=\"POST\" action=\"/ui\" {\n+                input type=\"hidden\" name=(UI_RPC_FIELD) value=(rpc_json);\n+                input type=\"hidden\" name=\"ratio_left\" id=\"vote-ratio-left\" value=\"50\";\n+                input type=\"hidden\" name=\"ratio_right\" id=\"vote-ratio-right\" value=\"50\";\n+                label class=\"vote-compare-slider-label\" {\n+                    span id=\"vote-slider-left-label\" { (child_title(&tree, &left)) }\n+                    input type=\"range\" id=\"vote-preference-slider\" min=\"0\" max=\"100\" value=\"50\"\n+                        aria-valuemin=\"0\" aria-valuemax=\"100\";\n+                    span id=\"vote-slider-right-label\" { (child_title(&tree, &right)) }\n+                }\n+                (vote_compare_actions(&parent, next_pair.as_ref()))\n+            }\n+        }\n+    };\n+\n+    drop(tree);\n+\n+    let path = format!(\"/vote?parent={}\", urlencoding::encode(parent.as_str()));\n+    state.views.increment(path.clone());\n+    let views = state.views.get_views(&path);\n+\n+    Html(\n+        layout(\n+            &title,\n+            body,\n+            views,\n+        )\n+        .into_string(),\n+    )\n+    .into_response()\n+}\ndiff --git a/server/src/pair.rs b/server/src/pair.rs\nnew file mode 100644\nindex 0000000000000000000000000000000000000000..606ffa51038a57ffacf335aa48bdb1185f8483fb\n--- /dev/null\n+++ b/server/src/pair.rs\n@@ -0,0 +1,340 @@\n+//! Pick two children of a parent scope for pairwise voting.\n+//!\n+//! Pair selection prefers **bridge** votes — comparisons between items in\n+//! different connected components of the voted-pairs graph — so the pool\n+//! merges into one ranking group before refining within it.\n+\n+use rand::seq::SliceRandom;\n+use std::collections::{HashMap, HashSet};\n+\n+use crate::{\n+    path_types::ItemId,\n+    ranking::connected_components_from_voted_pairs,\n+    reducer::{GlobalTree, GroupState},\n+};\n+\n+fn pairs_match(a: &ItemId, b: &ItemId, x: &ItemId, y: &ItemId) -> bool {\n+    (a == x && b == y) || (a == y && b == x)\n+}\n+\n+fn pair_is_voted(group: &GroupState, a: &ItemId, b: &ItemId) -> bool {\n+    let Some(&ai) = group.item_to_idx.get(a) else {\n+        return false;\n+    };\n+    let Some(&bi) = group.item_to_idx.get(b) else {\n+        return false;\n+    };\n+    let (i, j) = if ai < bi { (ai, bi) } else { (bi, ai) };\n+    group.voted_pairs.contains(&(i, j))\n+}\n+\n+/// Component id per pool item: voted-pairs graph components plus one id per\n+/// never-voted child.\n+fn component_ids(group: &GroupState, pool: &[ItemId]) -> HashMap<ItemId, usize> {\n+    let n = group.idx_to_item.len();\n+    let (comps, isolates) =\n+        connected_components_from_voted_pairs(n, group.voted_pairs.iter().copied());\n+\n+    let mut out: HashMap<ItemId, usize> = HashMap::new();\n+    for (comp_idx, comp) in comps.iter().enumerate() {\n+        for &idx in comp {\n+            if idx < n {\n+                out.insert(group.idx_to_item[idx].clone(), comp_idx);\n+            }\n+        }\n+    }\n+    let mut next = comps.len();\n+    for &idx in &isolates {\n+        if idx < n {\n+            out.insert(group.idx_to_item[idx].clone(), next);\n+            next += 1;\n+        }\n+    }\n+    for item in pool {\n+        out.entry(item.clone()).or_insert_with(|| {\n+            let id = next;\n+            next += 1;\n+            id\n+        });\n+    }\n+    out\n+}\n+\n+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]\n+enum PairPriority {\n+    /// Unvoted edge between two components — grows the ranking group.\n+    BridgeUnvoted = 0,\n+    /// Unvoted edge inside one component — refines order.\n+    WithinUnvoted = 1,\n+    /// Re-vote across components (rare once merged).\n+    BridgeVoted = 2,\n+    /// Re-vote within a component.\n+    WithinVoted = 3,\n+}\n+\n+fn pair_priority(\n+    group: &GroupState,\n+    components: &HashMap<ItemId, usize>,\n+    a: &ItemId,\n+    b: &ItemId,\n+) -> PairPriority {\n+    let voted = pair_is_voted(group, a, b);\n+    let bridge = components.get(a) != components.get(b);\n+    match (bridge, voted) {\n+        (true, false) => PairPriority::BridgeUnvoted,\n+        (false, false) => PairPriority::WithinUnvoted,\n+        (true, true) => PairPriority::BridgeVoted,\n+        (false, true) => PairPriority::WithinVoted,\n+    }\n+}\n+\n+/// All unordered pairs from `pool`, optionally skipping `exclude`.\n+fn candidate_pairs(\n+    pool: &[ItemId],\n+    exclude: Option<(&ItemId, &ItemId)>,\n+) -> Vec<(ItemId, ItemId)> {\n+    let mut out = Vec::new();\n+    for i in 0..pool.len() {\n+        for j in (i + 1)..pool.len() {\n+            let a = &pool[i];\n+            let b = &pool[j];\n+            if a == b {\n+                continue;\n+            }\n+            if exclude.is_some_and(|(x, y)| pairs_match(a, b, x, y)) {\n+                continue;\n+            }\n+            out.push((a.clone(), b.clone()));\n+        }\n+    }\n+    out\n+}\n+\n+/// Pick the next pair to vote on within `pool`.\n+///\n+/// 1. Prefer unvoted **bridge** pairs (connect separate ranking components).\n+/// 2. Then unvoted within-component pairs (refinement).\n+/// 3. Then already-voted pairs (re-compare).\n+pub fn suggest_next_pair_in_pool(\n+    group: &GroupState,\n+    pool: &[ItemId],\n+    exclude: Option<(&ItemId, &ItemId)>,\n+) -> Option<(ItemId, ItemId)> {\n+    let candidates = candidate_pairs(pool, exclude);\n+    if candidates.is_empty() {\n+        return None;\n+    }\n+    let components = component_ids(group, pool);\n+    let best = candidates\n+        .iter()\n+        .map(|(a, b)| (pair_priority(group, &components, a, b), (a, b)))\n+        .min_by_key(|(p, _)| *p)?\n+        .0;\n+    let best_pairs: Vec<(ItemId, ItemId)> = candidates\n+        .into_iter()\n+        .filter(|(a, b)| pair_priority(group, &components, a, b) == best)\n+        .collect();\n+    best_pairs.choose(&mut rand::thread_rng()).cloned()\n+}\n+\n+/// Random distinct pair from `children` (legacy pair.rs behavior).\n+pub fn random_pair(children: &[ItemId]) -> Option<(ItemId, ItemId)> {\n+    if children.len() < 2 {\n+        return None;\n+    }\n+    let left = children.choose(&mut rand::thread_rng())?;\n+    let mut right = children.choose(&mut rand::thread_rng())?;\n+    let mut guard = 0;\n+    while left == right && guard < 32 {\n+        right = children.choose(&mut rand::thread_rng())?;\n+        guard += 1;\n+    }\n+    if left == right {\n+        return None;\n+    }\n+    Some((left.clone(), right.clone()))\n+}\n+\n+/// Sorted children of `parent` from the global tree.\n+pub fn children_of(tree: &GlobalTree, parent: &ItemId) -> Vec<ItemId> {\n+    let Some(node) = tree.get(parent) else {\n+        return Vec::new();\n+    };\n+    let mut children: Vec<ItemId> = node.children.iter().cloned().collect();\n+    children.sort_by(|a, b| a.as_str().cmp(b.as_str()));\n+    children\n+}\n+\n+/// Resolve a pair to compare under `parent`.\n+pub fn resolve_pair(\n+    tree: &GlobalTree,\n+    parent: &ItemId,\n+    left: Option<&ItemId>,\n+    right: Option<&ItemId>,\n+) -> Result<(ItemId, ItemId), PairError> {\n+    let children = children_of(tree, parent);\n+    if children.len() < 2 {\n+        return Err(PairError::TooFewChildren);\n+    }\n+    let child_set: HashSet<_> = children.iter().collect();\n+\n+    match (left, right) {\n+        (Some(l), Some(r)) => {\n+            if l == r {\n+                return Err(PairError::SameItem);\n+            }\n+            if !child_set.contains(l) || !child_set.contains(r) {\n+                return Err(PairError::NotChild);\n+            }\n+            Ok((l.clone(), r.clone()))\n+        }\n+        (None, None) => {\n+            let group = tree\n+                .get(parent)\n+                .map(|n| &n.local_ranking)\n+                .cloned()\n+                .unwrap_or_default();\n+            suggest_next_pair_in_pool(&group, &children, None).ok_or(PairError::NoPair)\n+        }\n+        _ => Err(PairError::IncompletePair),\n+    }\n+}\n+\n+#[derive(Debug, Clone, PartialEq, Eq)]\n+pub enum PairError {\n+    TooFewChildren,\n+    SameItem,\n+    NotChild,\n+    IncompletePair,\n+    NoPair,\n+}\n+\n+impl PairError {\n+    pub fn status_message(&self) -> (&'static str, axum::http::StatusCode) {\n+        match self {\n+            Self::TooFewChildren => (\n+                \"parent needs at least 2 children to vote\",\n+                axum::http::StatusCode::BAD_REQUEST,\n+            ),\n+            Self::SameItem => (\n+                \"left and right must differ\",\n+                axum::http::StatusCode::BAD_REQUEST,\n+            ),\n+            Self::NotChild => (\n+                \"left and right must be children of parent\",\n+                axum::http::StatusCode::BAD_REQUEST,\n+            ),\n+            Self::IncompletePair => (\n+                \"provide both left and right, or neither\",\n+                axum::http::StatusCode::BAD_REQUEST,\n+            ),\n+            Self::NoPair => (\n+                \"no pair available\",\n+                axum::http::StatusCode::BAD_REQUEST,\n+            ),\n+        }\n+    }\n+}\n+\n+#[cfg(test)]\n+mod tests {\n+    use super::*;\n+    use crate::reducer::{GlobalTree, VoteData};\n+\n+    fn seed_children(parent: &ItemId, ids: &[&str]) -> GlobalTree {\n+        let mut tree = GlobalTree::new();\n+        tree.ensure_path(parent);\n+        for id in ids {\n+            let child = ItemId::parse(id).unwrap();\n+            tree.ensure_path(&child);\n+            if let Some(p) = tree.nodes.get_mut(parent) {\n+                p.children.insert(child);\n+            }\n+        }\n+        tree\n+    }\n+\n+    fn pair_set(pair: &(ItemId, ItemId)) -> HashSet<&str> {\n+        [pair.0.as_str(), pair.1.as_str()].into_iter().collect()\n+    }\n+\n+    #[test]\n+    fn suggest_prefers_unvoted_pair() {\n+        let parent = ItemId::parse(\"reddit.com/r/rust\").unwrap();\n+        let mut tree = seed_children(\n+            &parent,\n+            &[\n+                \"reddit.com/r/rust/a\",\n+                \"reddit.com/r/rust/b\",\n+                \"reddit.com/r/rust/c\",\n+            ],\n+        );\n+        let vote =\n+            VoteData::from_recorded(1, \"reddit.com/r/rust/a\", \"reddit.com/r/rust/b\", 2, 1).unwrap();\n+        tree.apply_vote(&parent, vote);\n+        let group = tree.get(&parent).unwrap().local_ranking.clone();\n+        let pool = children_of(&tree, &parent);\n+        let (l, r) = suggest_next_pair_in_pool(&group, &pool, None).unwrap();\n+        let voted_ab = (l.as_str() == \"reddit.com/r/rust/a\" && r.as_str() == \"reddit.com/r/rust/b\")\n+            || (l.as_str() == \"reddit.com/r/rust/b\" && r.as_str() == \"reddit.com/r/rust/a\");\n+        assert!(!voted_ab);\n+    }\n+\n+    #[test]\n+    fn suggest_bridges_separate_components() {\n+        let parent = ItemId::parse(\"reddit.com/r/rust\").unwrap();\n+        let mut tree = seed_children(\n+            &parent,\n+            &[\n+                \"reddit.com/r/rust/a\",\n+                \"reddit.com/r/rust/b\",\n+                \"reddit.com/r/rust/c\",\n+                \"reddit.com/r/rust/d\",\n+            ],\n+        );\n+        let ab = VoteData::from_recorded(1, \"reddit.com/r/rust/a\", \"reddit.com/r/rust/b\", 2, 1).unwrap();\n+        let cd = VoteData::from_recorded(2, \"reddit.com/r/rust/c\", \"reddit.com/r/rust/d\", 2, 1).unwrap();\n+        tree.apply_vote(&parent, ab);\n+        tree.apply_vote(&parent, cd);\n+        let group = tree.get(&parent).unwrap().local_ranking.clone();\n+        let pool = children_of(&tree, &parent);\n+        let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();\n+        let chosen = pair_set(&pair);\n+        let from_ab = chosen.contains(\"reddit.com/r/rust/a\") || chosen.contains(\"reddit.com/r/rust/b\");\n+        let from_cd = chosen.contains(\"reddit.com/r/rust/c\") || chosen.contains(\"reddit.com/r/rust/d\");\n+        assert!(from_ab && from_cd, \"expected bridge pair, got {:?}\", chosen);\n+    }\n+\n+    #[test]\n+    fn suggest_connects_isolate_to_existing_component() {\n+        let parent = ItemId::parse(\"reddit.com/r/rust\").unwrap();\n+        let mut tree = seed_children(\n+            &parent,\n+            &[\n+                \"reddit.com/r/rust/a\",\n+                \"reddit.com/r/rust/b\",\n+                \"reddit.com/r/rust/c\",\n+            ],\n+        );\n+        let ab = VoteData::from_recorded(1, \"reddit.com/r/rust/a\", \"reddit.com/r/rust/b\", 2, 1).unwrap();\n+        tree.apply_vote(&parent, ab);\n+        let group = tree.get(&parent).unwrap().local_ranking.clone();\n+        let pool = children_of(&tree, &parent);\n+        let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();\n+        let chosen = pair_set(&pair);\n+        assert!(chosen.contains(\"reddit.com/r/rust/c\"));\n+        assert!(chosen.contains(\"reddit.com/r/rust/a\") || chosen.contains(\"reddit.com/r/rust/b\"));\n+    }\n+\n+    #[test]\n+    fn resolve_pair_picks_from_pool() {\n+        let parent = ItemId::parse(\"reddit.com/r/rust\").unwrap();\n+        let tree = seed_children(&parent, &[\"reddit.com/r/rust/a\", \"reddit.com/r/rust/b\"]);\n+        let pair = resolve_pair(&tree, &parent, None, None).unwrap();\n+        let pool: HashSet<_> = [\"reddit.com/r/rust/a\", \"reddit.com/r/rust/b\"]\n+            .into_iter()\n+            .collect();\n+        assert!(pool.contains(pair.0.as_str()));\n+        assert!(pool.contains(pair.1.as_str()));\n+    }\n+}\ndiff --git a/server/src/path_types.rs b/server/src/path_types.rs\nindex 12dce9888f5cd4e1a0974d12d6468368d0f775b9..a0d1a028b8bd3c5d1c714dea3ec597d1ac39e1bc 100644\n--- a/server/src/path_types.rs\n+++ b/server/src/path_types.rs\n@@ -40,6 +40,22 @@ impl ItemId {\n         Self::canonicalize(raw_url).map(Self)\n     }\n \n+    /// Normalize strings from forms, events, and Reddit imports into the same\n+    /// stored id shape (e.g. drop post title slug after comment id).\n+    pub fn from_storage(s: &str) -> Option<Self> {\n+        let t = s.trim();\n+        if t.is_empty() {\n+            return None;\n+        }\n+        if t.contains(\"://\") || t.starts_with(\"r/\") {\n+            return Self::from_url(t).or_else(|| Self::parse(t));\n+        }\n+        if t.starts_with(\"reddit.com/\") && t.contains(\"/comments/\") {\n+            return Self::from_url(t).or_else(|| Self::parse(t));\n+        }\n+        Self::parse(t).or_else(|| Self::from_url(t))\n+    }\n+\n     /// Map legacy scope keys (`\"\"`, `\"rust\"`) to fractal parent nodes.\n     pub fn from_legacy_scope(raw: &str) -> Self {\n         let s = raw.trim();\n@@ -324,6 +340,12 @@ mod tests {\n         assert_eq!(id.as_str(), \"reddit.com/r/amitheasshole\");\n     }\n \n+    #[test]\n+    fn from_storage_strips_post_title_slug() {\n+        let id = ItemId::from_storage(\"reddit.com/r/rust/comments/aaa/announcing_rust_199\").unwrap();\n+        assert_eq!(id.as_str(), \"reddit.com/r/rust/comments/aaa\");\n+    }\n+\n     #[test]\n     fn from_browse_uri_strips_prefix() {\n         let id = ItemId::from_browse_uri(\"/~/https://reddit.com/r/rust\").unwrap();\ndiff --git a/server/src/reddit.rs b/server/src/reddit.rs\nindex 1168ec2afc77c092514eec91b513bac301cbe225..626454e5a2f638734193b5190a2beea286af85b6 100644\n--- a/server/src/reddit.rs\n+++ b/server/src/reddit.rs\n@@ -567,7 +567,7 @@ fn parse_children(_parent: &ItemId, payload: &Value) -> Vec<(ItemId, Value)> {\n             _ => continue,\n         };\n         let path = format!(\"reddit.com{}\", permalink.trim_end_matches('/'));\n-        if let Some(id) = ItemId::parse(&path) {\n+        if let Some(id) = ItemId::from_storage(&path) {\n             out.push((id, child.clone()));\n         }\n     }\ndiff --git a/server/src/reducer.rs b/server/src/reducer.rs\nindex 336e78b77d3ab59361b89af5c9868e13da4ac962..fc23f41137d7df33997afe19c533505c250cc305 100644\n--- a/server/src/reducer.rs\n+++ b/server/src/reducer.rs\n@@ -28,8 +28,8 @@ impl VoteData {\n         ratio_left: i32,\n         ratio_right: i32,\n     ) -> Option<Self> {\n-        let a = ItemId::parse(a)?;\n-        let b = ItemId::parse(b)?;\n+        let a = ItemId::from_storage(a)?;\n+        let b = ItemId::from_storage(b)?;\n         if a == b {\n             return None;\n         }\n@@ -85,8 +85,8 @@ impl GroupState {\n     }\n \n     pub fn apply_vote(&mut self, mut vote: VoteData) {\n-        vote.a = ItemId::parse(vote.a.as_str()).unwrap_or_else(|| vote.a.clone());\n-        vote.b = ItemId::parse(vote.b.as_str()).unwrap_or_else(|| vote.b.clone());\n+        vote.a = ItemId::from_storage(vote.a.as_str()).unwrap_or(vote.a.clone());\n+        vote.b = ItemId::from_storage(vote.b.as_str()).unwrap_or(vote.b.clone());\n         if vote.ratio_left < 0 {\n             vote.ratio_left = 0;\n         }\ndiff --git a/server/src/state.rs b/server/src/state.rs\nindex d238701208a1c708b94a778a6a2e1891a678ecbc..4c3008e73cc74d8483a2064a0a280e73d82a01ec 100644\n--- a/server/src/state.rs\n+++ b/server/src/state.rs\n@@ -18,7 +18,7 @@ pub fn parse_item_param(raw: &str) -> ItemId {\n     if s.is_empty() {\n         return ItemId::root();\n     }\n-    ItemId::from_url(s).or_else(|| ItemId::parse(s)).unwrap_or_else(|| ItemId::opaque(s))\n+    ItemId::from_storage(s).unwrap_or_else(|| ItemId::opaque(s))\n }\n \n /// Legacy: normalize raw ranking subject into a scope key for old event replay.\ndiff --git a/server/src/ui_action.rs b/server/src/ui_action.rs\nindex 53581e1362bfcc5dfb4ae3069c41ea6f7be41437..237411a689fb10ad1b7022ea66aee1969c7507ec 100644\n--- a/server/src/ui_action.rs\n+++ b/server/src/ui_action.rs\n@@ -31,9 +31,9 @@ pub enum HtmlUiAction {\n         /// Parent node [`ItemId`] string; empty = tree root.\n         #[serde(default)]\n         scope: String,\n-        /// After vote, navigate here (vote compare page).\n+        /// Posted from `/vote` compare UI — morph edge history in place.\n         #[serde(default)]\n-        next: String,\n+        vote_compare: bool,\n     },\n     /// Parse pasted Reddit URL/path; redirect to subreddit ranking on success.\n     ParseQuery {\n@@ -98,7 +98,7 @@ mod tests {\n                 ratio_left: 60,\n                 ratio_right: 40,\n                 scope: \"parent\".into(),\n-                next: String::new(),\n+                vote_compare: false,\n             }\n         );\n     }\n@@ -129,7 +129,7 @@ mod tests {\n                 ratio_left: 2,\n                 ratio_right: 1,\n                 scope: \"amitheasshole\".into(),\n-                next: String::new(),\n+                vote_compare: false,\n             }\n         );\n     }\n@@ -156,7 +156,7 @@ mod tests {\n                 ratio_left: 2,\n                 ratio_right: 1,\n                 scope: String::new(),\n-                next: String::new(),\n+                vote_compare: false,\n             }\n         );\n     }\ndiff --git a/server/static/sorter.css b/server/static/sorter.css\nindex 3c2cec5cb5094013387147c621d75bd341bc06cc..b95718ce463b200a5667d3014dac2119836a0bef 100644\n--- a/server/static/sorter.css\n+++ b/server/static/sorter.css\n@@ -289,11 +289,27 @@ h1 {\n }\n \n .vote-compare-nav {\n+  margin: 1rem 0 0.5rem;\n+}\n+\n+.vote-compare-actions {\n   display: flex;\n-  justify-content: space-between;\n+  flex-wrap: wrap;\n   align-items: center;\n-  gap: 1rem;\n-  margin: 1rem 0;\n+  gap: 0.75rem;\n+  margin-top: 0.5rem;\n+}\n+\n+.vote-compare-actions .btn-secondary {\n+  margin-top: 0;\n+  display: inline-block;\n+  text-decoration: none;\n+  line-height: 1.4;\n+}\n+\n+.vote-compare-actions .vote-compare-next.is-disabled {\n+  opacity: 0.6;\n+  cursor: default;\n }\n \n .vote-compare-next {\ndiff --git a/server/static/sorter_ui.js b/server/static/sorter_ui.js\nindex c8d7c3ef2413399ced7898a7edb3e7a2c8e16163..ab15d27f508cc6f5fbca9d8926fd0ca26d64857b 100644\n--- a/server/static/sorter_ui.js\n+++ b/server/static/sorter_ui.js\n@@ -104,11 +104,10 @@\n       if (f.getAttribute('data-navigate') === 'full') return;\n       e.preventDefault();\n       await postUiForm(f);\n-      if (f.id === 'vote-form' || f.id === 'vote-compare-form') {\n+      if (f.id === 'vote-form') {\n         f.reset();\n-        var slider = f.querySelector('#vote-preference-slider');\n-        if (slider) slider.value = '50';\n-        initVoteSlider();\n+        var firstField = f.querySelector('input[type=\"text\"]');\n+        if (firstField) firstField.focus();\n       }\n     });\n   }\ndiff --git a/server/tests/integration_ui.rs b/server/tests/integration_ui.rs\nindex df7d9ab357531c5146d0b326c149fdaa6b531a4a..56d2db313b313ffce07eff38a8ccdaa2fbb9498f 100644\n--- a/server/tests/integration_ui.rs\n+++ b/server/tests/integration_ui.rs\n@@ -25,6 +25,53 @@ async fn start_test_server() -> (SocketAddr, TempDir) {\n     (addr, tmp)\n }\n \n+#[tokio::test]\n+async fn post_ui_vote_compare_morphs_edge_history() {\n+    let (addr, _tmp) = start_test_server().await;\n+    let parent = \"reddit.com/r/rust\";\n+    let a = \"reddit.com/r/rust/comments/aaa/announcing_rust_199\";\n+    let b = \"reddit.com/r/rust/comments/bbb/what_are_you_working_on\";\n+\n+    let rpc = serde_json::json!({\n+        \"action\": \"record_vote\",\n+        \"a\": a,\n+        \"b\": b,\n+        \"ratio_left\": {\"$form:i32\": \"ratio_left\"},\n+        \"ratio_right\": {\"$form:i32\": \"ratio_right\"},\n+        \"scope\": parent,\n+        \"vote_compare\": true,\n+    })\n+    .to_string();\n+    let mut form = HashMap::new();\n+    form.insert(UI_RPC_FIELD.to_string(), rpc);\n+    form.insert(\"ratio_left\".into(), \"70\".into());\n+    form.insert(\"ratio_right\".into(), \"30\".into());\n+\n+    let client = reqwest::Client::new();\n+    let body = client\n+        .post(format!(\"http://{addr}/ui\"))\n+        .form(&form)\n+        .send()\n+        .await\n+        .unwrap()\n+        .text()\n+        .await\n+        .unwrap();\n+\n+    assert!(\n+        body.contains(\"vote-edge-history\"),\n+        \"expected edge history morph, got: {body}\"\n+    );\n+    assert!(\n+        body.contains(\"70:30\"),\n+        \"expected recorded ratio in morph, got: {body}\"\n+    );\n+    assert!(\n+        !body.contains(\"no votes on this pair yet\"),\n+        \"should not show empty edge history after vote, got: {body}\"\n+    );\n+}\n+\n #[tokio::test]\n async fn post_ui_record_vote_morphs_ranking_and_persists() {\n     let (addr, tmp) = start_test_server().await;\ndiff --git a/test/reddit_import.clj b/test/reddit_import.clj\nindex 45a2a19f20799d77e84d8aa64735ab5e7e45f97c..b476488526252c13fd73bdda76e5201678e4a714 100644\n--- a/test/reddit_import.clj\n+++ b/test/reddit_import.clj\n@@ -2,9 +2,8 @@\n   (:require [babashka.process :as process]\n             [clojure.java.io :as io]\n             [clojure.string :as str]\n-            [clojure.test :refer [deftest is testing]])\n-  (:import [com.sun.net.httpserver HttpServer HttpHandler HttpExchange]\n-           [java.net InetSocketAddress]))\n+            [clojure.test :refer [deftest is testing]]\n+            [test.support.mock-reddit :as mock-reddit]))\n \n (defn- repo-root []\n   (.getCanonicalPath (io/file (System/getProperty \"user.dir\"))))\n@@ -13,29 +12,6 @@\n   (with-open [s (java.net.ServerSocket. 0)]\n     (.getLocalPort s)))\n \n-(defn- start-mock-reddit [port fixtures-dir]\n-  (let [about (.getBytes (slurp (io/file fixtures-dir \"r_rust_about.json\")) \"UTF-8\")\n-        listing (.getBytes (slurp (io/file fixtures-dir \"r_rust_listing.json\")) \"UTF-8\")\n-        server (HttpServer/create (InetSocketAddress. \"127.0.0.1\" port) 0)\n-        handler\n-        (proxy [HttpHandler] []\n-          (handle [^HttpExchange exchange]\n-            ;; Route by path: `/r/<sub>/about.json` is the subreddit entity,\n-            ;; `/r/<sub>.json` is the children listing.\n-            (let [path (.getPath (.getRequestURI exchange))\n-                  body (if (str/includes? path \"/about\")\n-                         about\n-                         listing)]\n-              (.sendResponseHeaders exchange 200 (alength body))\n-              (let [out (.getResponseBody exchange)]\n-                (.write out body)\n-                (.close out)))))]\n-    (.createContext server \"/\" handler)\n-    (.setExecutor server nil)\n-    (.start server)\n-    (fn stop []\n-      (.stop server 0))))\n-\n (defn- wait-health [base-url ms]\n   (let [deadline (+ (System/currentTimeMillis) ms)\n         url (str base-url \"/healthz\")]\n@@ -100,7 +76,7 @@\n (deftest reddit-fetch-via-mock-api\n   (testing \"Fetch more queues import; event log stores full payload; page shows title\"\n     (let [root (repo-root)\n-          fixtures (str root \"/test/fixtures/reddit\")\n+          fixtures (mock-reddit/fixtures-dir root)\n           data-dir (.getAbsolutePath\n                     (doto (io/file (System/getProperty \"java.io.tmpdir\")\n                                    (str \"sorter2-reddit-\" (System/currentTimeMillis)))\n@@ -110,7 +86,7 @@\n           reddit-base (str \"http://127.0.0.1:\" reddit-port)\n           app-base (str \"http://127.0.0.1:\" app-port)\n           bin (str root \"/target/release/sorter2-server\")\n-          stop-mock (start-mock-reddit reddit-port fixtures)]\n+          stop-mock (mock-reddit/start-mock-reddit reddit-port fixtures)]\n       (try\n         (is (zero? (:exit (process/shell {:dir root}\n                                          \"cargo\" \"build\" \"--release\" \"--package\" \"sorter2-server\")))\ndiff --git a/test/support/mock_reddit.clj b/test/support/mock_reddit.clj\nnew file mode 100644\nindex 0000000000000000000000000000000000000000..5efa92db3e1f79b8f423a2f1adcbda959123c1ad\n--- /dev/null\n+++ b/test/support/mock_reddit.clj\n@@ -0,0 +1,35 @@\n+(ns test.support.mock-reddit\n+  \"In-process HTTP stub for Reddit API fixtures (`test/fixtures/reddit/`).\"\n+  (:require [clojure.java.io :as io]\n+            [clojure.string :as str])\n+  (:import [com.sun.net.httpserver HttpServer HttpHandler HttpExchange]\n+           [java.net InetSocketAddress]))\n+\n+(defn fixtures-dir\n+  ([] (fixtures-dir (System/getProperty \"user.dir\")))\n+  ([root] (str root \"/test/fixtures/reddit\")))\n+\n+(defn start-mock-reddit\n+  \"Start a mock Reddit API on `port`. Returns a zero-arg `stop` function.\"\n+  ([port] (start-mock-reddit port (fixtures-dir)))\n+  ([port dir]\n+   (let [about (.getBytes (slurp (io/file dir \"r_rust_about.json\")) \"UTF-8\")\n+         listing (.getBytes (slurp (io/file dir \"r_rust_listing.json\")) \"UTF-8\")\n+         server (HttpServer/create (InetSocketAddress. \"127.0.0.1\" port) 0)\n+         handler\n+         (proxy [HttpHandler] []\n+           (handle [^HttpExchange exchange]\n+             ;; `/r/<sub>/about.json` → subreddit entity; `/r/<sub>.json` → listing.\n+             (let [path (.getPath (.getRequestURI exchange))\n+                   body (if (str/includes? path \"/about\")\n+                          about\n+                          listing)]\n+               (.sendResponseHeaders exchange 200 (alength body))\n+               (let [out (.getResponseBody exchange)]\n+                 (.write out body)\n+                 (.close out)))))]\n+     (.createContext server \"/\" handler)\n+     (.setExecutor server nil)\n+     (.start server)\n+     (fn stop []\n+       (.stop server 0)))))\ndiff --git a/test/vote_compare.clj b/test/vote_compare.clj\nnew file mode 100644\nindex 0000000000000000000000000000000000000000..fbc00281e466a1ba0833193c7b96fa30aeb45a5c\n--- /dev/null\n+++ b/test/vote_compare.clj\n@@ -0,0 +1,101 @@\n+(ns test.vote-compare\n+  (:require [babashka.process :as process]\n+            [clojure.java.io :as io]\n+            [clojure.string :as str]\n+            [clojure.test :refer [deftest is testing]]\n+            [com.blockether.spel.core :as core]\n+            [com.blockether.spel.locator :as loc]\n+            [com.blockether.spel.page :as page]\n+            [test.support.mock-reddit :as mock-reddit])\n+  (:import [java.net URLEncoder]))\n+\n+(defn- repo-root []\n+  (.getCanonicalPath (io/file (System/getProperty \"user.dir\"))))\n+\n+(defn- pick-port []\n+  (with-open [s (java.net.ServerSocket. 0)]\n+    (.getLocalPort s)))\n+\n+(defn- wait-health [base-url ms]\n+  (let [deadline (+ (System/currentTimeMillis) ms)\n+        url (str base-url \"/healthz\")]\n+    (loop []\n+      (let [resp (try\n+                   (process/shell {:out :string :err :string}\n+                                  \"curl\" \"-sf\" url)\n+                   (catch Exception _ nil))]\n+        (if (and resp (zero? (:exit resp)) (= \"ok\" (str/trim (:out resp \"\"))))\n+          true\n+          (if (< (System/currentTimeMillis) deadline)\n+            (do (Thread/sleep 200) (recur))\n+            false))))))\n+\n+(defn- curl-fetch-children [base item]\n+  (process/shell {:out :string :err :string}\n+                 \"curl\" \"-sfN\" \"--max-time\" \"20\"\n+                 \"-X\" \"POST\" (str base \"/ui\")\n+                 \"--data-urlencode\"\n+                 (str \"__rpc__={\\\"action\\\":\\\"fetch_entity\\\",\\\"item\\\":\\\"\" item\n+                      \"\\\",\\\"kind\\\":\\\"children\\\"}\")))\n+\n+(defn- vote-page-url [base parent]\n+  (str base \"/vote?parent=\"\n+       (URLEncoder/encode parent \"UTF-8\")))\n+\n+(deftest vote-compare-shows-recorded-vote-after-post\n+  (testing \"post vote on /vote morphs edge history (mock Reddit children seeded)\"\n+    (let [root (repo-root)\n+          fixtures (mock-reddit/fixtures-dir root)\n+          data-dir (.getAbsolutePath\n+                    (doto (io/file (System/getProperty \"java.io.tmpdir\")\n+                                   (str \"sorter2-vote-\" (System/currentTimeMillis)))\n+                      (.mkdirs)))\n+          reddit-port (pick-port)\n+          app-port (pick-port)\n+          reddit-base (str \"http://127.0.0.1:\" reddit-port)\n+          app-base (str \"http://127.0.0.1:\" app-port)\n+          bin (str root \"/target/release/sorter2-server\")\n+          stop-mock (mock-reddit/start-mock-reddit reddit-port fixtures)]\n+      (try\n+        (is (zero? (:exit (process/shell {:dir root}\n+                                         \"cargo\" \"build\" \"--release\" \"--package\" \"sorter2-server\")))\n+            \"release build succeeds\")\n+        (let [proc (process/process {:dir root\n+                                     :env (into (into {} (System/getenv))\n+                                                {\"SORTER2_SKIP_DOTENV\" \"1\"\n+                                                 \"SORTER2_DATA_DIR\" data-dir\n+                                                 \"SORTER2_EVENT_LOG\" (str data-dir \"/events.jsonl\")\n+                                                 \"PORT\" (str app-port)\n+                                                 \"REDDIT_API_BASE\" reddit-base\n+                                                 \"REDDIT_OAUTH_BASE\" reddit-base\n+                                                 \"REDDIT_CLIENT_ID\" \"\"\n+                                                 \"REDDIT_CLIENT_SECRET\" \"\"\n+                                                 \"REDDIT_APP_ID\" \"\"\n+                                                 \"REDDIT_APP_SECRET\" \"\"})\n+                                     :out :string\n+                                     :err :string}\n+                                    bin)]\n+          (try\n+            (is (wait-health app-base 20000) \"app healthz\")\n+            (let [fetch (curl-fetch-children app-base \"reddit.com/r/rust\")]\n+              (is (zero? (:exit fetch)) \"fetch posts via mock Reddit\")\n+              (is (str/includes? (:out fetch) \"Idiomorph.morph\")))\n+            (core/with-testing-page [pg]\n+              (page/navigate pg (vote-page-url app-base \"reddit.com/r/rust\"))\n+              (page/wait-for-selector pg \"#vote-compare-form\")\n+              (let [before (loc/text-content (page/locator pg \"#vote-edge-history-region\"))]\n+                (is (str/includes? before \"no votes on this pair yet\")\n+                    \"empty edge history before first vote\"))\n+              (loc/click (page/get-by-test-id pg \"vote-post\"))\n+              (page/wait-for-selector pg \".vote-edge-history-title\")\n+              (let [after (loc/text-content (page/locator pg \"#vote-edge-history-region\"))]\n+                (is (str/includes? after \"votes on this pair\")\n+                    \"shows edge history title after vote\")\n+                (is (str/includes? after \"50:50\")\n+                    \"shows submitted ratio after vote\")\n+                (is (not (str/includes? after \"no votes on this pair yet\"))\n+                    \"does not revert to empty edge history\")))\n+            (finally\n+              (process/destroy proc))))\n+        (finally\n+          (stop-mock))))))\n","role":"user"}],"model":"~anthropic/claude-sonnet-latest"}