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:
[075d4d37] Fix OAuth test mocks so Clojure E2E auth flows work again.

HttpServer handlers were crashing on query parsing and token POSTs, which broke Playwright login; also read alias/history via real CSS selectors.

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

Side A — unified diff (full patch):
diff --git a/test/auth_login.clj b/test/auth_login.clj
index 6f2f00d7aa7340e63d1ac465b0a2234cec7a983f..aa63b66ccb2471b710ba3d168d0461252b39fc10 100644
--- a/test/auth_login.clj
+++ b/test/auth_login.clj
@@ -14,27 +14,27 @@
 (defn- type-alias! [pg text]
   (page/evaluate pg
                  (.replace
-                  "(() => { const i = document.getElementById('alias-input'); const f = document.getElementById('alias-check-form'); if (!i || !f) return;
+                  "(() => { const i = document.getElementById('alias-input'); const f = document.getElementById('alias-check-form'); if (!i || !f) return Promise.resolve('missing-form');
                     i.value = __TEXT__;
                     const cf = document.getElementById('alias-claim-field'); if (cf) cf.value = i.value;
                     return fetch(f.action, { method: 'POST', credentials: 'same-origin',
                       headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
                       body: new URLSearchParams(new FormData(f)).toString() })
                       .then(function (r) { return r.text(); })
-                      .then(function (t) { eval(t); }); })()"
+                      .then(function (t) { eval(t); return document.getElementById('alias-status')?.textContent || ''; }); })()"
                   "__TEXT__"
-                  (pr-str text)))
-  (Thread/sleep 400))
+                  (pr-str text))))
 
-(defn- element-text [pg test-id]
+(defn- element-text [pg selector]
   (let [raw (page/evaluate pg
-                           (str "document.querySelector('[data-testid=\"" test-id "\"]')?.textContent || ''"))]
+                           (str "document.querySelector(" (pr-str selector) ")?.textContent || ''"))]
     (when (string? raw) (str/trim raw))))
 
 (defn- wait-for-text [pg test-id text timeout-ms]
-  (let [deadline (+ (System/currentTimeMillis) timeout-ms)]
+  (let [deadline (+ (System/currentTimeMillis) timeout-ms)
+        selector (str "[data-testid=\"" test-id "\"]")]
     (loop []
-      (let [got (or (element-text pg test-id) "")]
+      (let [got (or (element-text pg selector) "")]
         (cond
           (= got text) got
           (< (System/currentTimeMillis) deadline) (do (Thread/sleep 200) (recur))
diff --git a/test/support/mock_oauth.clj b/test/support/mock_oauth.clj
index 5ba7e9be3cf6d2226648e9609a09ed45f306930f..333fe08d56cb06bac2a338cad1c73894d54c4495 100644
--- a/test/support/mock_oauth.clj
+++ b/test/support/mock_oauth.clj
@@ -7,7 +7,7 @@
 (defn- query-param [query key]
   (when query
     (some (fn [pair]
-            (let [[k v] (str/split pair "=" 2)]
+            (let [[k v] (str/split pair #"=" 2)]
               (when (= k key)
                 (URLDecoder/decode (or v "") "UTF-8"))))
           (str/split query #"&"))))
@@ -31,11 +31,11 @@
 
 (defn- send-redirect [^HttpExchange ex location]
   (.set (.getResponseHeaders ex) "Location" location)
-  (.sendResponseHeaders ex 302 -1)
+  (.sendResponseHeaders ex 302 0)
   (.close (.getResponseBody ex)))
 
 (defn- read-form [^HttpExchange ex]
-  (let [body (slurp (.getInputStream ex))]
+  (let [body (slurp (.getRequestBody ex))]
     {:code (query-param body "code")
      :grant (query-param body "grant_type")}))
 
@@ -45,7 +45,7 @@
           (str/replace #"^[Bb]earer " "")))
 
 (defn- parse-token-user [token]
-  (when (str/starts-with? token "mock:")
+  (when (and token (str/starts-with? token "mock:"))
     (parse-mock-user (subs token 5))))
 
 (defn- authorize-redirect [exchange query]
@@ -55,7 +55,7 @@
         user (parse-mock-user mock-user)
         code (str "mock:" (:id user) ":" (:login user))
         loc (str redirect-uri "?code=" (java.net.URLEncoder/encode code "UTF-8")
-                 "&state=" (java.net.URLEncoder/encode state "UTF-8"))]
+                 "&state=" (java.net.URLEncoder/encode (or state "") "UTF-8"))]
     (send-redirect exchange loc)))
 
 (defn start-mock-oauth
@@ -65,49 +65,56 @@
         handler
         (proxy [HttpHandler] []
           (handle [^HttpExchange exchange]
-            (let [uri (.getRequestURI exchange)
-                  path (.getPath uri)
-                  query (.getQuery uri)
-                  method (.getRequestMethod exchange)]
-              (cond
-                ;; GitHub authorize
-                (str/ends-with? path "/login/oauth/authorize")
-                (authorize-redirect exchange query)
+            (try
+              (let [uri (.getRequestURI exchange)
+                    path (.getPath uri)
+                    query (.getQuery uri)
+                    method (.getRequestMethod exchange)]
+                (cond
+                  ;; GitHub authorize
+                  (str/ends-with? path "/login/oauth/authorize")
+                  (authorize-redirect exchange query)
 
-                ;; Reddit authorize
-                (str/ends-with? path "/api/v1/authorize")
-                (authorize-redirect exchange query)
+                  ;; Reddit authorize
+                  (str/ends-with? path "/api/v1/authorize")
+                  (authorize-redirect exchange query)
 
-                ;; GitHub token
-                (and (= method "POST") (str/ends-with? path "/login/oauth/access_token"))
-                (let [code (or (:code (read-form exchange)) "mock:1002:newbie")]
-                  (send-json exchange 200 (str "{\"access_token\":\"" code "\",\"token_type\":\"bearer\"}")))
+                  ;; GitHub token
+                  (and (= method "POST") (str/ends-with? path "/login/oauth/access_token"))
+                  (let [code (or (:code (read-form exchange)) "mock:1002:newbie")]
+                    (send-json exchange 200 (str "{\"access_token\":\"" code "\",\"token_type\":\"bearer\"}")))
 
-                ;; Reddit token (client_credentials for import + authorization_code for login)
-                (and (= method "POST") (str/ends-with? path "/api/v1/access_token"))
-                (let [form (read-form exchange)
-                      grant (or (:grant form) "")
-                      code (or (:code form) "mock:t2_test:redditor")]
-                  (if (= grant "client_credentials")
-                    (send-json exchange 200 "{\"access_token\":\"app-token\",\"token_type\":\"bearer\",\"expires_in\":3600}")
-                    (send-json exchange 200 (str "{\"access_token\":\"" code "\",\"token_type\":\"bearer\",\"expires_in\":3600}"))))
+                  ;; Reddit token (client_credentials for import + authorization_code for login)
+                  (and (= method "POST") (str/ends-with? path "/api/v1/access_token"))
+                  (let [form (read-form exchange)
+                        grant (or (:grant form) "")
+                        code (or (:code form) "mock:t2_test:redditor")]
+                    (if (= grant "client_credentials")
+                      (send-json exchange 200 "{\"access_token\":\"app-token\",\"token_type\":\"bearer\",\"expires_in\":3600}")
+                      (send-json exchange 200 (str "{\"access_token\":\"" code "\",\"token_type\":\"bearer\",\"expires_in\":3600}"))))
 
-                ;; GitHub user
-                (= path "/user")
-                (let [token (bearer-token exchange)
-                      user (or (parse-token-user token) {:id "1002" :login "newbie" :numeric? true})]
-                  (send-json exchange 200
-                             (str "{\"id\":" (:id user) ",\"login\":\"" (:login user) "\"}")))
+                  ;; GitHub user
+                  (= path "/user")
+                  (let [token (bearer-token exchange)
+                        user (or (parse-token-user token) {:id "1002" :login "newbie" :numeric? true})]
+                    (send-json exchange 200
+                               (str "{\"id\":" (:id user) ",\"login\":\"" (:login user) "\"}")))
 
-                ;; Reddit /api/v1/me
-                (str/ends-with? path "/api/v1/me")
-                (let [token (bearer-token exchange)
-                      user (or (parse-token-user token) {:id "t2_test" :login "redditor"})]
-                  (send-json exchange 200
-                             (str "{\"id\":\"" (:id user) "\",\"name\":\"" (:login user) "\"}")))
+                  ;; Reddit /api/v1/me
+                  (str/ends-with? path "/api/v1/me")
+                  (let [token (bearer-token exchange)
+                        user (or (parse-token-user token) {:id "t2_test" :login "redditor"})]
+                    (send-json exchange 200
+                               (str "{\"id\":\"" (:id user) "\",\"name\":\"" (:login user) "\"}")))
 
-                :else
-                (send-json exchange 404 "{\"error\":\"not found\"}")))))]
+                  :else
+                  (send-json exchange 404 "{\"error\":\"not found\"}")))
+              (catch Throwable t
+                (binding [*out* *err*]
+                  (println "mock-oauth handler error:" t))
+                (try
+                  (send-json exchange 500 "{\"error\":\"mock-oauth internal\"}")
+                  (catch Throwable _))))))]
     (.createContext server "/" handler)
     (.setExecutor server nil)
     (.start server)
diff --git a/test/support/mock_reddit.clj b/test/support/mock_reddit.clj
index a630cf0938722193e9af88382d60e777ff371be4..faa27945b6394363914c853627a0bad1e819a5f9 100644
--- a/test/support/mock_reddit.clj
+++ b/test/support/mock_reddit.clj
@@ -12,7 +12,7 @@
 (defn- query-param [query key]
   (when query
     (some (fn [pair]
-            (let [[k v] (str/split pair "=" 2)]
+            (let [[k v] (str/split pair #"=" 2)]
               (when (= k key)
                 (URLDecoder/decode (or v "") "UTF-8"))))
           (str/split query #"&"))))
@@ -34,11 +34,11 @@
 
 (defn- send-redirect [^HttpExchange ex location]
   (.set (.getResponseHeaders ex) "Location" location)
-  (.sendResponseHeaders ex 302 -1)
+  (.sendResponseHeaders ex 302 0)
   (.close (.getResponseBody ex)))
 
 (defn- read-form [^HttpExchange ex]
-  (let [body (slurp (.getInputStream ex))]
+  (let [body (slurp (.getRequestBody ex))]
     {:code (query-param body "code")
      :grant (query-param body "grant_type")}))
 
@@ -48,7 +48,7 @@
           (str/replace #"^[Bb]earer " "")))
 
 (defn- parse-token-user [token]
-  (when (str/starts-with? token "mock:")
+  (when (and token (str/starts-with? token "mock:"))
     (parse-mock-user (subs token 5))))
 
 (defn start-mock-reddit
@@ -72,7 +72,7 @@
                        user (parse-mock-user (query-param query "mock_user"))
                        code (str "mock:" (:id user) ":" (:login user))
                        loc (str redirect-uri "?code=" (java.net.URLEncoder/encode code "UTF-8")
-                                "&state=" (java.net.URLEncoder/encode state "UTF-8"))]
+                                "&state=" (java.net.URLEncoder/encode (or state "") "UTF-8"))]
                    (send-redirect exchange loc))
 
                  (and (= method "POST") (str/ends-with? path "/api/v1/access_token"))


Side B — contributor: tommy-mor
Side B — commit message:
[88577c56] reconfigure

Side B — unified diff (full patch):
diff --git a/server/src/api/ui_html.rs b/server/src/api/ui_html.rs
index c4ab9d65c7b3cd42a5b4d093ba429993c101e9a8..82b2aa51d21ada1d0d849d3ddfc3a81e4241d861 100644
--- a/server/src/api/ui_html.rs
+++ b/server/src/api/ui_html.rs
@@ -9,7 +9,9 @@ use crate::{
     html::{js_string_literal, ranking_panel, JsBuilder},
     parser::parse_reddit_url,
     parser_render::navigate_panel,
-    state::AppState,
+    path_types::ItemId,
+    reddit::ensure_partial_tree,
+    state::{parse_item_param, AppState},
     ui_action::{parse_html_ui_from_form, HtmlUiAction},
 };
 
@@ -25,6 +27,10 @@ fn ui_js_warn(msg: &str) -> Response {
         .unwrap()
 }
 
+fn parent_from_scope(scope: &str) -> ItemId {
+    parse_item_param(scope)
+}
+
 pub async fn post_ui_html(
     State(state): State<AppState>,
     Form(form): Form<HashMap<String, String>>,
@@ -42,24 +48,36 @@ pub async fn post_ui_html(
             ratio_right,
             scope,
         } => {
+            let parent = parent_from_scope(&scope);
             if let Err(e) = state
-                .record_vote(&scope, &a, &b, ratio_left, ratio_right)
+                .record_vote(&parent, &a, &b, ratio_left, ratio_right)
                 .await
             {
                 return ui_js_warn(&e).into_response();
             }
-            let scope = crate::state::normalize_scope(&scope);
-            let groups = state.groups.read().await;
+            let tree = state.tree.read().await;
             let empty = crate::reducer::GroupState::new();
-            let group = groups.get(&scope).unwrap_or(&empty);
-            let panel = ranking_panel(&scope, group);
+            let group = tree
+                .get(&parent)
+                .map(|n| &n.local_ranking)
+                .unwrap_or(&empty);
+            let panel = ranking_panel(&parent, group);
             JsBuilder::new()
                 .morph_selector("#ranking-panel", panel)
                 .into_response()
         }
         HtmlUiAction::ParseQuery { query } => match parse_reddit_url(&query) {
-            Ok(subreddit) => {
-                let dest = format!("/?sub={subreddit}");
+            Ok(item) => {
+                {
+                    let mut tree = state.tree.write().await;
+                    ensure_partial_tree(&mut tree, &item);
+                }
+                let _ = state.ensure_node(&item).await;
+                let dest = if item.is_root() {
+                    "/".to_string()
+                } else {
+                    format!("/?item={}", item.as_str())
+                };
                 JsBuilder::new()
                     .raw(&format!(
                         "window.location.href={};",
diff --git a/server/src/events.rs b/server/src/events.rs
index a862370fc840ffe02184a11c578e18239cc9474d..ed5be6b13b9d46e838831d6ce0f96f569b401730 100644
--- a/server/src/events.rs
+++ b/server/src/events.rs
@@ -5,8 +5,8 @@ use serde::{Deserialize, Serialize};
 pub enum Event {
     /// Page view recorded (path → counter in views.json).
     ViewRecorded { path: String, ts: i64 },
-    /// Pairwise comparison vote (replayed into the scope's [`crate::reducer::GroupState`] on boot).
-    /// `scope` is the ranking subject (e.g. a subreddit); empty string is the default/global scope.
+    /// Pairwise comparison vote (replayed into the parent node's [`crate::reducer::GroupState`] on boot).
+    /// `scope` is the parent [`crate::path_types::ItemId`] string; empty string is the tree root.
     VoteRecorded {
         ts: i64,
         a: String,
@@ -16,4 +16,6 @@ pub enum Event {
         #[serde(default)]
         scope: String,
     },
+    /// Register a node path in the fractal tree (no external fetch).
+    NodeEnsured { id: String },
 }
diff --git a/server/src/html/mod.rs b/server/src/html/mod.rs
index 9650d333d29c4ac94ceb407aee3ee00399c7f40b..c973cb718ac74b95570dabea76e24459417790b9 100644
--- a/server/src/html/mod.rs
+++ b/server/src/html/mod.rs
@@ -12,9 +12,10 @@ use serde::Deserialize;
 use crate::{
     form_template::template_json_compact,
     parser_render::navigate_panel,
+    path_types::ItemId,
     ranking::{top_bottom, RankedItem},
-    reducer::GroupState,
-    state::{normalize_scope, AppState},
+    reducer::{GroupState, NodeState},
+    state::{parse_item_param, AppState},
     ui_action::UI_RPC_FIELD,
 };
 
@@ -216,6 +217,48 @@ fn layout(title: &str, body: Markup, views: u64, theme: &str, theme_next: &str)
     }
 }
 
+fn item_href(id: &ItemId) -> String {
+    if id.is_root() {
+        "/".to_string()
+    } else {
+        format!("/?item={}", id.as_str())
+    }
+}
+
+fn segment_label(seg: &str) -> &str {
+    seg
+}
+
+/// Generic breadcrumb trail from an [`ItemId`] path.
+pub fn breadcrumb_path(item: &ItemId) -> Markup {
+    html! {
+        nav class="breadcrumbs" aria-label="Breadcrumb" {
+            a href="/" { "Internet" }
+            @for path in item.breadcrumb_paths() {
+                @let seg = path.segments().last().map_or("", |v| *v);
+                span class="separator" { " / " }
+                a href=(item_href(&path)) { (segment_label(seg)) }
+            }
+        }
+    }
+}
+
+fn entity_panel(node: &NodeState) -> Markup {
+    html! {
+        @if let Some(data) = &node.data {
+            section id="entity-panel" class="demo-panel entity-card" {
+                h2 { (data.title) }
+                @if let Some(author) = &data.author {
+                    p class="muted small" { "by " (author) }
+                }
+                @if let Some(body) = &data.body_html {
+                    div class="entity-body" { (maud::PreEscaped(body)) }
+                }
+            }
+        }
+    }
+}
+
 fn rank_list(label: &str, items: &[RankedItem], start_rank: usize) -> Markup {
     html! {
         @if !items.is_empty() {
@@ -224,7 +267,9 @@ fn rank_list(label: &str, items: &[RankedItem], start_rank: usize) -> Markup {
                 @for (i, r) in items.iter().enumerate() {
                     li {
                         span class="rank-num" { (start_rank + i) ". " }
-                        strong { (r.item.as_str()) }
+                        a href=(item_href(&r.item)) {
+                            strong { (display_label(&r.item)) }
+                        }
                         span class="muted" {
                             " — "
                             ({ format!("{:.1}%", r.score * 100.0) })
@@ -236,23 +281,30 @@ fn rank_list(label: &str, items: &[RankedItem], start_rank: usize) -> Markup {
     }
 }
 
-pub fn ranking_panel(scope: &str, group: &GroupState) -> Markup {
+fn display_label(id: &ItemId) -> String {
+    id.segments()
+        .last()
+        .map_or("Internet", |v| *v)
+        .to_string()
+}
+
+pub fn ranking_panel(item: &ItemId, group: &GroupState) -> Markup {
     let total = group.idx_to_item.len();
     let (top, bottom) = top_bottom(group, 8);
     html! {
         section id="ranking-panel" class="demo-panel" {
             h2 {
                 "Ranking"
-                @if !scope.is_empty() {
-                    " — " span class="scope-name" { "r/" (scope) }
+                @if !item.is_root() {
+                    " — " span class="scope-name" { (item.as_str()) }
                 }
             }
             @if total == 0 {
                 p class="muted" {
-                    @if scope.is_empty() {
+                    @if item.is_root() {
                         "No votes yet — compare two items below."
                     } @else {
-                        "No votes yet for r/" (scope) " — compare two items below to start the ranking."
+                        "No votes yet for " (item.as_str()) " — compare two items below to start the ranking."
                     }
                 }
             } @else {
@@ -266,7 +318,8 @@ pub fn ranking_panel(scope: &str, group: &GroupState) -> Markup {
     }
 }
 
-pub fn vote_panel(scope: &str) -> Markup {
+pub fn vote_panel(parent: &ItemId) -> Markup {
+    let parent_str = parent.as_str();
     let rpc = template_json_compact(&serde_json::json!({
         "action": "record_vote",
         "a": {"$form": "item_a"},
@@ -280,16 +333,17 @@ pub fn vote_panel(scope: &str) -> Markup {
         section id="vote-panel" class="demo-panel" {
             h2 { "Compare" }
             p class="muted small" {
-                @if scope.is_empty() {
+                @if parent.is_root() {
                     "Left item wins at 2:1. Votes append to the JSONL log and update rank centrality."
                 } @else {
-                    "Ranking " span class="scope-name" { "r/" (scope) }
+                    "Ranking children of "
+                    span class="scope-name" { (parent_str) }
                     ". Left item wins at 2:1; each vote updates this ranking."
                 }
             }
             form method="post" action="/ui" id="vote-form" {
                 input type="hidden" name=(UI_RPC_FIELD) value=(rpc);
-                input type="hidden" name="scope" value=(scope);
+                input type="hidden" name="scope" value=(parent_str);
                 div class="vote-fields" {
                     label {
                         "Left (wins) "
@@ -329,17 +383,30 @@ pub async fn home(
     let views = state.views.get_views(&path);
     let theme = theme_from_jar(&jar);
     let theme_next = theme_next_from_uri(&uri);
-    let scope = normalize_scope(&query_param(&uri, "sub").unwrap_or_default());
 
-    let groups = state.groups.read().await;
-    let empty = GroupState::new();
-    let group = groups.get(&scope).unwrap_or(&empty);
+    let item_raw = query_param(&uri, "item")
+        .or_else(|| query_param(&uri, "sub").map(|sub| {
+            if sub.is_empty() {
+                String::new()
+            } else {
+                format!("reddit.com/r/{sub}")
+            }
+        }))
+        .unwrap_or_default();
+    let item = parse_item_param(&item_raw);
+
+    let tree = state.tree.read().await;
+    let empty_node = NodeState::default();
+    let node = tree.get(&item).unwrap_or(&empty_node);
+    let group = &node.local_ranking;
 
     let body = html! {
         h1 { "sorter2" }
+        (breadcrumb_path(&item))
         (navigate_panel("", None))
-        (vote_panel(&scope))
-        (ranking_panel(&scope, group))
+        (entity_panel(node))
+        (vote_panel(&item))
+        (ranking_panel(&item, group))
     };
     layout("sorter2", body, views, theme, &theme_next)
 }
diff --git a/server/src/journal.rs b/server/src/journal.rs
new file mode 100644
index 0000000000000000000000000000000000000000..b02ca025683621470ffdf8cd85cf9b85c56d024d
--- /dev/null
+++ b/server/src/journal.rs
@@ -0,0 +1,89 @@
+use std::sync::Arc;
+
+use tokio::sync::{mpsc, oneshot, RwLock};
+
+use crate::{
+    event_log::EventLog,
+    events::Event,
+    path_types::ItemId,
+    reducer::{GlobalTree, VoteData},
+};
+
+pub struct JournalCommand {
+    pub parent: ItemId,
+    pub vote: VoteData,
+    pub event: Event,
+    pub reply: oneshot::Sender<Result<(), String>>,
+}
+
+#[derive(Clone)]
+pub struct JournalClient {
+    tx: mpsc::Sender<JournalCommand>,
+}
+
+impl JournalClient {
+    pub fn spawn(tree: Arc<RwLock<GlobalTree>>, event_log: Arc<EventLog>) -> Self {
+        let (tx, rx) = mpsc::channel(64);
+        tokio::spawn(journal_worker(rx, tree, event_log));
+        Self { tx }
+    }
+
+    pub async fn record_vote(
+        &self,
+        parent: ItemId,
+        vote: VoteData,
+        event: Event,
+    ) -> Result<(), String> {
+        let (reply, rx) = oneshot::channel();
+        self.tx
+            .send(JournalCommand {
+                parent,
+                vote,
+                event,
+                reply,
+            })
+            .await
+            .map_err(|_| "journal worker stopped".to_string())?;
+        rx.await
+            .map_err(|_| "journal worker stopped".to_string())?
+    }
+}
+
+async fn journal_worker(
+    mut rx: mpsc::Receiver<JournalCommand>,
+    tree: Arc<RwLock<GlobalTree>>,
+    event_log: Arc<EventLog>,
+) {
+    while let Some(first) = rx.recv().await {
+        let mut batch = vec![first];
+        while let Ok(more) = rx.try_recv() {
+            batch.push(more);
+        }
+
+        let mut disk_err: Option<String> = None;
+        for cmd in &batch {
+            if let Err(e) = event_log.append(&cmd.event).await {
+                disk_err = Some(e.to_string());
+                break;
+            }
+        }
+
+        if let Some(err) = disk_err {
+            for cmd in batch {
+                let _ = cmd.reply.send(Err(err.clone()));
+            }
+            continue;
+        }
+
+        {
+            let mut w = tree.write().await;
+            for cmd in &batch {
+                w.apply_vote(&cmd.parent, cmd.vote.clone());
+            }
+        }
+
+        for cmd in batch {
+            let _ = cmd.reply.send(Ok(()));
+        }
+    }
+}
diff --git a/server/src/lib.rs b/server/src/lib.rs
index de8bca48cbf689cad22337883e7791966e7c4919..14e7cfbc38feb5d07aff859b64bce6e2ec45cf91 100644
--- a/server/src/lib.rs
+++ b/server/src/lib.rs
@@ -7,8 +7,9 @@ pub mod parser;
 pub mod parser_render;
 pub mod path_types;
 pub mod ranking;
+pub mod reddit;
 pub mod reducer;
-pub mod settlement;
+pub mod journal;
 pub mod state;
 pub mod ui_action;
 pub mod views;
diff --git a/server/src/parser.rs b/server/src/parser.rs
index 50571a59f0d3ece1e2538f88e00ef46ec40ea545..51aa0e0f982546aab68bd5e1ca0cb726e88b3f50 100644
--- a/server/src/parser.rs
+++ b/server/src/parser.rs
@@ -1,47 +1,18 @@
-//! Extract a subreddit name from a pasted Reddit URL or path.
+//! Extract a canonical [`crate::path_types::ItemId`] from a pasted Reddit URL or path.
 
-pub fn parse_reddit_url(query: &str) -> Result<String, String> {
+use crate::path_types::ItemId;
+
+pub fn parse_reddit_url(query: &str) -> Result<ItemId, String> {
     let q = query.trim();
     if q.is_empty() {
         return Err("Paste a Reddit URL or r/subreddit path".into());
     }
 
-    if let Some(sub) = subreddit_after_prefix(q, "r/") {
-        return Ok(sub);
-    }
-
-    if let Some(sub) = subreddit_from_path_segment(q, "/r/") {
-        return Ok(sub);
+    if let Some(id) = ItemId::from_url(q) {
+        return Ok(id);
     }
 
-    Err("Could not find a subreddit in that URL".into())
-}
-
-fn subreddit_after_prefix(text: &str, prefix: &str) -> Option<String> {
-    let rest = text.strip_prefix(prefix)?;
-    let sub = rest.split(['/', '?', '#']).next()?.trim();
-    valid_subreddit(sub)
-}
-
-fn subreddit_from_path_segment(text: &str, needle: &str) -> Option<String> {
-    let idx = text.find(needle)?;
-    let rest = &text[idx + needle.len()..];
-    let sub = rest.split(['/', '?', '#']).next()?.trim();
-    valid_subreddit(sub)
-}
-
-fn valid_subreddit(name: &str) -> Option<String> {
-    if name.is_empty() {
-        return None;
-    }
-    if name
-        .chars()
-        .all(|c| c.is_ascii_alphanumeric() || c == '_')
-    {
-        Some(name.to_ascii_lowercase())
-    } else {
-        None
-    }
+    Err("Could not parse that Reddit URL".into())
 }
 
 #[cfg(test)]
@@ -50,34 +21,37 @@ mod tests {
 
     #[test]
     fn parses_short_path() {
-        assert_eq!(parse_reddit_url("r/rust").unwrap(), "rust");
-    }
-
-    #[test]
-    fn parses_path_with_trailing_slash() {
-        assert_eq!(parse_reddit_url("r/rust/").unwrap(), "rust");
+        assert_eq!(
+            parse_reddit_url("r/rust").unwrap().as_str(),
+            "reddit.com/r/rust"
+        );
     }
 
     #[test]
     fn parses_full_url() {
         assert_eq!(
-            parse_reddit_url("https://www.reddit.com/r/programming/hot").unwrap(),
-            "programming"
+            parse_reddit_url("https://www.reddit.com/r/programming/hot")
+                .unwrap()
+                .as_str(),
+            "reddit.com/r/programming"
         );
     }
 
     #[test]
-    fn parses_url_without_scheme() {
+    fn parses_post_url() {
+        let id = parse_reddit_url(
+            "https://old.reddit.com/r/AmItheAsshole/comments/1trnvdl/aita_for_cancelling/",
+        )
+        .unwrap();
         assert_eq!(
-            parse_reddit_url("reddit.com/r/AskReddit").unwrap(),
-            "askreddit"
+            id.as_str(),
+            "reddit.com/r/amitheasshole/comments/1trnvdl"
         );
     }
 
     #[test]
     fn rejects_empty() {
         assert!(parse_reddit_url("").is_err());
-        assert!(parse_reddit_url("   ").is_err());
     }
 
     #[test]
diff --git a/server/src/parser_render.rs b/server/src/parser_render.rs
index f2341afe21476b689a536137798d97277211a962..acf2e7403f4238291677ef0c79d5766302ea78cf 100644
--- a/server/src/parser_render.rs
+++ b/server/src/parser_render.rs
@@ -21,7 +21,7 @@ pub fn navigate_panel(query: &str, error: Option<&str>) -> Markup {
             p class="muted small" {
                 "Paste a Reddit URL or "
                 code { "r/subreddit" }
-                " path, then click Go to rank that subreddit."
+                " path. Breadcrumb links drill down the tree; rankings apply to each node's children."
             }
             form method="post" action="/ui" id="parser-form" {
                 textarea
diff --git a/server/src/path_types.rs b/server/src/path_types.rs
index 1cdc96a25b1954f11aaf955203e2b9907b578366..b5c41444f7bcd4d8d289ed3af464bc3f14d0df99 100644
--- a/server/src/path_types.rs
+++ b/server/src/path_types.rs
@@ -1,11 +1,13 @@
 use serde::{Deserialize, Serialize};
 use std::fmt;
 
-/// Stable item key for votes and rankings (opaque string for now).
-#[derive(Debug, Clone, Hash, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
+/// Canonical hierarchical identity for any URL/path in the fractal tree.
+#[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.
     pub fn parse(s: &str) -> Option<Self> {
         let t = s.trim();
         if t.is_empty() {
@@ -14,13 +16,170 @@ impl ItemId {
         Some(Self(t.to_string()))
     }
 
+    /// Build an opaque item key (legacy demo votes, non-URL items).
     pub fn opaque(s: impl Into<String>) -> Self {
         Self(s.into())
     }
 
+    /// Root of the internet tree (empty path).
+    pub fn root() -> Self {
+        Self(String::new())
+    }
+
+    pub fn is_root(&self) -> bool {
+        self.0.is_empty()
+    }
+
     pub fn as_str(&self) -> &str {
         &self.0
     }
+
+    /// Creates a canonical ID from a raw URL or path. Normalizes domains and
+    /// trims tracking query params.
+    pub fn from_url(raw_url: &str) -> Option<Self> {
+        Self::canonicalize(raw_url).map(Self)
+    }
+
+    /// Map legacy scope keys (`""`, `"rust"`) to fractal parent nodes.
+    pub fn from_legacy_scope(raw: &str) -> Self {
+        let s = raw.trim();
+        if s.is_empty() {
+            return Self::root();
+        }
+        Self(format!("reddit.com/r/{s}"))
+    }
+
+    /// Extract the parent, e.g. `reddit.com/r/aww/comments/1trnvdl` →
+    /// `reddit.com/r/aww`.
+    pub fn parent(&self) -> Option<Self> {
+        if self.0.is_empty() {
+            return None;
+        }
+
+        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> {
+        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"]`.
+    pub fn breadcrumb_paths(&self) -> Vec<ItemId> {
+        let segs = self.segments();
+        let mut paths = Vec::with_capacity(segs.len());
+        let mut current = String::new();
+        for seg in segs {
+            if current.is_empty() {
+                current = seg.to_string();
+            } else {
+                current.push('/');
+                current.push_str(seg);
+            }
+            paths.push(ItemId(current.clone()));
+        }
+        paths
+    }
+
+    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_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 {
@@ -28,3 +187,69 @@ impl fmt::Display for ItemId {
         f.write_str(&self.0)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn from_url_normalizes_reddit_domains() {
+        let id = ItemId::from_url(
+            "https://old.reddit.com/r/AmItheAsshole/comments/1trnvdl/aita_for_cancelling/",
+        )
+        .unwrap();
+        assert_eq!(
+            id.as_str(),
+            "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");
+    }
+
+    #[test]
+    fn from_url_short_path() {
+        assert_eq!(
+            ItemId::from_url("r/rust").unwrap().as_str(),
+            "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"
+        );
+    }
+
+    #[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");
+    }
+
+    #[test]
+    fn breadcrumb_paths() {
+        let id = ItemId::parse("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"]
+        );
+    }
+
+    #[test]
+    fn legacy_scope_maps_to_reddit_sub() {
+        assert_eq!(
+            ItemId::from_legacy_scope("rust").as_str(),
+            "reddit.com/r/rust"
+        );
+        assert!(ItemId::from_legacy_scope("").is_root());
+    }
+}
diff --git a/server/src/reddit.rs b/server/src/reddit.rs
new file mode 100644
index 0000000000000000000000000000000000000000..d203dca09245daf869b3aa942898447700ae69fb
--- /dev/null
+++ b/server/src/reddit.rs
@@ -0,0 +1,21 @@
+//! Reddit API import (async, decoupled from UI request path).
+
+use crate::{
+    path_types::ItemId,
+    reducer::{EntityData, GlobalTree},
+};
+
+/// Bootstrap blank nodes along a URL path so breadcrumbs and voting work before fetch.
+pub fn ensure_partial_tree(tree: &mut GlobalTree, id: &ItemId) {
+    tree.ensure_path(id);
+}
+
+/// Placeholder for Reddit JSON import. Returns entity data when implemented.
+pub async fn fetch_reddit_entity(_id: &ItemId) -> Option<EntityData> {
+    None
+}
+
+/// Apply fetched entity data to a node (called from async worker).
+pub fn apply_entity(tree: &mut GlobalTree, id: &ItemId, data: EntityData) {
+    tree.set_entity_data(id, data);
+}
diff --git a/server/src/reducer.rs b/server/src/reducer.rs
index 8d28353e1f2a67e71b7d17a2041a0988150f3245..077f700bf00ddefe18ffd004bb5288bdc7c4adaf 100644
--- a/server/src/reducer.rs
+++ b/server/src/reducer.rs
@@ -115,6 +115,96 @@ impl GroupState {
     }
 }
 
+/// Structured data imported from Reddit or elsewhere.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct EntityData {
+    pub title: String,
+    pub author: Option<String>,
+    pub body_html: Option<String>,
+    pub thumb_url: Option<String>,
+}
+
+/// One node in the fractal tree: entity + ranked children.
+#[derive(Debug, Clone, Default)]
+pub struct NodeState {
+    pub id: ItemId,
+    pub data: Option<EntityData>,
+    pub children: HashSet<ItemId>,
+    pub local_ranking: GroupState,
+}
+
+impl NodeState {
+    fn new(id: ItemId) -> Self {
+        Self {
+            id,
+            ..Default::default()
+        }
+    }
+}
+
+/// Global fractal graph: every URL is both an item and a ranking scope for its children.
+#[derive(Default)]
+pub struct GlobalTree {
+    pub nodes: HashMap<ItemId, NodeState>,
+}
+
+impl GlobalTree {
+    pub fn new() -> Self {
+        let mut tree = Self::default();
+        tree.ensure_node(&ItemId::root());
+        tree
+    }
+
+    pub fn ensure_node(&mut self, id: &ItemId) -> &mut NodeState {
+        if !self.nodes.contains_key(id) {
+            self.nodes.insert(id.clone(), NodeState::new(id.clone()));
+        }
+        self.nodes.get_mut(id).expect("node just inserted")
+    }
+
+    /// Register a node and wire parent→child links along the canonical path.
+    pub fn ensure_path(&mut self, id: &ItemId) {
+        if id.is_root() {
+            self.ensure_node(id);
+            return;
+        }
+        self.ensure_node(&ItemId::root());
+        for path in id.breadcrumb_paths() {
+            self.ensure_node(&path);
+            if let Some(parent) = path.parent() {
+                self.ensure_node(&parent);
+                if let Some(p) = self.nodes.get_mut(&parent) {
+                    p.children.insert(path.clone());
+                }
+            } else if let Some(r) = self.nodes.get_mut(&ItemId::root()) {
+                r.children.insert(path.clone());
+            }
+        }
+    }
+
+    pub fn get(&self, id: &ItemId) -> Option<&NodeState> {
+        self.nodes.get(id)
+    }
+
+    pub fn apply_vote(&mut self, parent: &ItemId, vote: VoteData) {
+        self.ensure_path(parent);
+        self.ensure_path(&vote.a);
+        self.ensure_path(&vote.b);
+        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);
+        }
+    }
+
+    pub fn set_entity_data(&mut self, id: &ItemId, data: EntityData) {
+        self.ensure_path(id);
+        if let Some(node) = self.nodes.get_mut(id) {
+            node.data = Some(data);
+        }
+    }
+}
+
 #[cfg(test)]
 mod from_recorded_tests {
     use super::*;
@@ -125,7 +215,20 @@ mod from_recorded_tests {
     }
 
     #[test]
-    fn rejects_empty() {
+    fn rejects_empty_pair() {
         assert!(VoteData::from_recorded(1, "", "b", 2, 1).is_none());
     }
+
+    #[test]
+    fn ensure_path_wires_children() {
+        let mut tree = GlobalTree::new();
+        let id = ItemId::parse("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();
+        assert!(reddit.children.contains(&ItemId::parse("reddit.com/r").unwrap()));
+        let sub = tree.get(&id).unwrap();
+        assert_eq!(sub.id, id);
+    }
 }
diff --git a/server/src/settlement.rs b/server/src/settlement.rs
deleted file mode 100644
index 7a44495512b7f788239b8aeefbbd0a83656eeac6..0000000000000000000000000000000000000000
--- a/server/src/settlement.rs
+++ /dev/null
@@ -1,94 +0,0 @@
-use std::collections::HashMap;
-use std::sync::Arc;
-
-use tokio::sync::{mpsc, oneshot, RwLock};
-
-use crate::{
-    event_log::EventLog,
-    events::Event,
-    reducer::{GroupState, VoteData},
-};
-
-/// Per-scope ranking state, keyed by scope (e.g. subreddit; "" is the default scope).
-pub type GroupMap = HashMap<String, GroupState>;
-
-pub struct SettlementCommand {
-    pub scope: String,
-    pub vote: VoteData,
-    pub event: Event,
-    pub reply: oneshot::Sender<Result<(), String>>,
-}
-
-#[derive(Clone)]
-pub struct SettlementClient {
-    tx: mpsc::Sender<SettlementCommand>,
-}
-
-impl SettlementClient {
-    pub fn spawn(groups: Arc<RwLock<GroupMap>>, event_log: Arc<EventLog>) -> Self {
-        let (tx, rx) = mpsc::channel(64);
-        tokio::spawn(settlement_worker(rx, groups, event_log));
-        Self { tx }
-    }
-
-    pub async fn record_vote(
-        &self,
-        scope: String,
-        vote: VoteData,
-        event: Event,
-    ) -> Result<(), String> {
-        let (reply, rx) = oneshot::channel();
-        self.tx
-            .send(SettlementCommand {
-                scope,
-                vote,
-                event,
-                reply,
-            })
-            .await
-            .map_err(|_| "settlement worker stopped".to_string())?;
-        rx.await
-            .map_err(|_| "settlement worker stopped".to_string())?
-    }
-}
-
-async fn settlement_worker(
-    mut rx: mpsc::Receiver<SettlementCommand>,
-    groups: Arc<RwLock<GroupMap>>,
-    event_log: Arc<EventLog>,
-) {
-    while let Some(first) = rx.recv().await {
-        let mut batch = vec![first];
-        while let Ok(more) = rx.try_recv() {
-            batch.push(more);
-        }
-
-        let mut disk_err: Option<String> = None;
-        for cmd in &batch {
-            if let Err(e) = event_log.append(&cmd.event).await {
-                disk_err = Some(e.to_string());
-                break;
-            }
-        }
-
-        if let Some(err) = disk_err {
-            for cmd in batch {
-                let _ = cmd.reply.send(Err(err.clone()));
-            }
-            continue;
-        }
-
-        {
-            let mut w = groups.write().await;
-            for cmd in &batch {
-                w.entry(cmd.scope.clone())
-                    .or_default()
-                    .apply_vote(cmd.vote.clone());
-            }
-        }
-
-        for cmd in batch {
-            let _ = cmd.reply.send(Ok(()));
-        }
-    }
-}
diff --git a/server/src/state.rs b/server/src/state.rs
index 2d9e5226057f8615897aac48bce947643a230fb4..cc1722f5a5bf4d415f2327ea585c488a15a75592 100644
--- a/server/src/state.rs
+++ b/server/src/state.rs
@@ -1,4 +1,3 @@
-use std::collections::HashMap;
 use std::sync::Arc;
 
 use tokio::sync::RwLock;
@@ -6,14 +5,22 @@ use tokio::sync::RwLock;
 use crate::{
     event_log::EventLog,
     events::Event,
-    reducer::VoteData,
-    settlement::{GroupMap, SettlementClient},
+    path_types::ItemId,
+    reducer::{GlobalTree, VoteData},
+    journal::JournalClient,
     views::ViewStore,
 };
 
-/// Normalize a raw ranking subject into a scope key: strip an optional `r/`
-/// prefix, keep only `[a-z0-9_]`, lowercase, and cap the length. Empty string
-/// is the default/global scope.
+/// Parse `?item=` query value into a canonical node id.
+pub fn parse_item_param(raw: &str) -> ItemId {
+    let s = raw.trim();
+    if s.is_empty() {
+        return ItemId::root();
+    }
+    ItemId::from_url(s).or_else(|| ItemId::parse(s)).unwrap_or_else(|| ItemId::opaque(s))
+}
+
+/// Legacy: normalize raw ranking subject into a scope key for old event replay.
 pub fn normalize_scope(raw: &str) -> String {
     let s = raw.trim();
     let s = s
@@ -27,6 +34,14 @@ pub fn normalize_scope(raw: &str) -> String {
         .collect()
 }
 
+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)
+    }
+}
+
 #[derive(Clone)]
 pub struct AppConfig {
     pub data_dir: String,
@@ -56,8 +71,8 @@ pub struct AppState {
     pub cfg: Arc<AppConfig>,
     pub event_log: Arc<EventLog>,
     pub views: ViewStore,
-    pub groups: Arc<RwLock<GroupMap>>,
-    settlement: SettlementClient,
+    pub tree: Arc<RwLock<GlobalTree>>,
+    journal: JournalClient,
 }
 
 impl AppState {
@@ -66,7 +81,7 @@ impl AppState {
         let views_path = format!("{}/views.json", cfg.data_dir);
         let views = ViewStore::new(&views_path);
 
-        let mut groups: GroupMap = HashMap::new();
+        let mut tree = GlobalTree::new();
         if let Ok((events, _)) = event_log.load_all().await {
             for ev in events {
                 match ev {
@@ -81,29 +96,45 @@ impl AppState {
                         if let Some(vote) =
                             VoteData::from_recorded(ts, &a, &b, ratio_left, ratio_right)
                         {
-                            groups.entry(scope).or_default().apply_vote(vote);
+                            let parent = parent_from_event_scope(&scope);
+                            tree.apply_vote(&parent, vote);
                         }
                     }
                     Event::ViewRecorded { .. } => {}
+                    Event::NodeEnsured { id } => {
+                        if let Some(parsed) = ItemId::parse(&id).or_else(|| ItemId::from_url(&id)) {
+                            tree.ensure_path(&parsed);
+                        }
+                    }
                 }
             }
         }
 
-        let groups = Arc::new(RwLock::new(groups));
-        let settlement = SettlementClient::spawn(groups.clone(), event_log.clone());
+        let tree = Arc::new(RwLock::new(tree));
+        let journal = JournalClient::spawn(tree.clone(), event_log.clone());
 
         Self {
             cfg: Arc::new(cfg),
             event_log,
             views,
-            groups,
-            settlement,
+            tree,
+            journal,
         }
     }
 
+    pub async fn ensure_node(&self, id: &ItemId) -> Result<(), String> {
+        let event = Event::NodeEnsured {
+            id: id.as_str().to_string(),
+        };
+        self.event_log.append(&event).await.map_err(|e| e.to_string())?;
+        let mut w = self.tree.write().await;
+        w.ensure_path(id);
+        Ok(())
+    }
+
     pub async fn record_vote(
         &self,
-        scope: &str,
+        parent: &ItemId,
         a: &str,
         b: &str,
         ratio_left: i32,
@@ -113,23 +144,24 @@ impl AppState {
         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 scope = normalize_scope(scope);
         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,
-            scope: scope.clone(),
+            scope: parent.as_str().to_string(),
         };
 
-        self.settlement.record_vote(scope, vote, event).await
+        self.journal
+            .record_vote(parent.clone(), vote, event)
+            .await
     }
 }
 
 #[cfg(test)]
 mod tests {
-    use super::normalize_scope;
+    use super::{normalize_scope, parse_item_param};
 
     #[test]
     fn normalize_scope_strips_prefix_and_lowercases() {
@@ -138,4 +170,15 @@ mod tests {
         assert_eq!(normalize_scope("r/web_dev!!"), "web_dev");
         assert_eq!(normalize_scope(""), "");
     }
+
+    #[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");
+    }
+
+    #[test]
+    fn parse_item_param_empty_is_root() {
+        assert!(parse_item_param("").is_root());
+    }
 }
diff --git a/server/src/ui_action.rs b/server/src/ui_action.rs
index 0e030b3448b8e45acbe49d2de47ea26372445c54..d798874d1d94c0dfee59ec1ff703f9ee6ef432c0 100644
--- a/server/src/ui_action.rs
+++ b/server/src/ui_action.rs
@@ -18,7 +18,7 @@ pub enum HtmlUiAction {
         b: String,
         ratio_left: i32,
         ratio_right: i32,
-        /// Ranking subject (e.g. a subreddit). Empty string = default/global scope.
+        /// Parent node [`ItemId`] string; empty = tree root.
         #[serde(default)]
         scope: String,
     },
diff --git a/server/static/theme_default.css b/server/static/theme_default.css
index 6ad0ac712bbc840bedee60f613794de9385fbbd1..1bf8ac7a25207336c019f93cd4119bd0e06229f0 100644
--- a/server/static/theme_default.css
+++ b/server/static/theme_default.css
@@ -137,6 +137,38 @@ code {
   margin-top: 0.5rem;
 }
 
+.breadcrumbs {
+  font-size: 0.875rem;
+  margin-bottom: 1rem;
+  color: var(--muted);
+}
+
+.breadcrumbs a {
+  color: var(--accent);
+  text-decoration: none;
+}
+
+.breadcrumbs a:hover {
+  text-decoration: underline;
+}
+
+.breadcrumbs .separator {
+  color: var(--muted);
+}
+
+.rank-list a {
+  color: var(--accent);
+  text-decoration: none;
+}
+
+.rank-list a:hover {
+  text-decoration: underline;
+}
+
+.entity-card h2 {
+  margin-top: 0;
+}
+
 .scope-name {
   color: var(--accent);
   font-weight: 600;
diff --git a/server/tests/integration_ui.rs b/server/tests/integration_ui.rs
index afeeee24e32f2d7f1d852ca96ac799fac8bce665..f7ac9c26bf9f9277ad5f5708603224c095165fb8 100644
--- a/server/tests/integration_ui.rs
+++ b/server/tests/integration_ui.rs
@@ -2,7 +2,7 @@ use std::collections::HashMap;
 use std::net::SocketAddr;
 
 use axum::Router;
-use sorter2_server::{create_app, create_app_state, state::AppConfig, ui_action::UI_RPC_FIELD};
+use sorter2_server::{create_app, create_app_state, path_types::ItemId, state::AppConfig, ui_action::UI_RPC_FIELD};
 use tempfile::TempDir;
 use tokio::net::TcpListener;
 
@@ -63,9 +63,9 @@ async fn post_ui_record_vote_morphs_ranking_and_persists() {
         port: 0,
     };
     let state = create_app_state(cfg).await;
-    let groups = state.groups.read().await;
-    let group = groups.get("").expect("default scope group after replay");
-    let ranked = sorter2_server::ranking::ranked_items(group);
+    let tree = state.tree.read().await;
+    let root = tree.get(&ItemId::root()).expect("root node after replay");
+    let ranked = sorter2_server::ranking::ranked_items(&root.local_ranking);
     assert_eq!(ranked.len(), 2);
     assert_eq!(ranked[0].item.as_str(), "alpha");
 }
@@ -93,5 +93,5 @@ async fn post_ui_parse_query_redirects_to_subreddit() {
         .unwrap();
 
     assert!(body.contains("window.location.href"));
-    assert!(body.contains("/?sub=rust"));
+    assert!(body.contains("/?item=reddit.com/r/rust"));
 }