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:
[07715165] nice

Side A — unified diff (full patch):
diff --git a/server/src/api/ui_html.rs b/server/src/api/ui_html.rs
index c3c62a76f424010d77a6090c84dd0b82098f573e..da2536112faea313352624cf2ce0ddd0ab3377c1 100644
--- a/server/src/api/ui_html.rs
+++ b/server/src/api/ui_html.rs
@@ -6,7 +6,7 @@ use axum::{
 use std::collections::HashMap;
 
 use crate::{
-    html::{demo_counter_panel, js_string_literal, ranking_panel, JsBuilder},
+    html::{js_string_literal, ranking_panel, JsBuilder},
     parser::parse_reddit_url,
     parser_render::parser_panel_morph,
     state::AppState,
@@ -35,13 +35,6 @@ pub async fn post_ui_html(
     };
 
     match action {
-        HtmlUiAction::BumpDemoCounter => {
-            let count = state.bump_demo_counter().await;
-            let panel = demo_counter_panel(count, state.event_log.path().to_string_lossy().as_ref());
-            JsBuilder::new()
-                .morph_selector("#demo-counter-panel", panel)
-                .into_response()
-        }
         HtmlUiAction::RecordVote {
             a,
             b,
@@ -54,8 +47,8 @@ pub async fn post_ui_html(
             {
                 return ui_js_warn(&e).into_response();
             }
-            let mut group = state.group.write().await;
-            let panel = ranking_panel(&mut group);
+            let group = state.group.read().await;
+            let panel = ranking_panel(&group);
             JsBuilder::new()
                 .morph_selector("#ranking-panel", panel)
                 .into_response()
@@ -87,20 +80,6 @@ mod tests {
         assert!(matches!(err, HtmlUiParseError::MissingRpc));
     }
 
-    #[test]
-    fn bump_action_deserializes() {
-        let template = serde_json::json!({ "action": "bump_demo_counter" });
-        let mut form = HashMap::new();
-        form.insert(
-            UI_RPC_FIELD.to_string(),
-            serde_json::to_string(&template).unwrap(),
-        );
-        assert_eq!(
-            parse_html_ui_from_form(&form).unwrap(),
-            HtmlUiAction::BumpDemoCounter
-        );
-    }
-
     #[test]
     fn record_vote_action_deserializes() {
         let template = serde_json::json!({
diff --git a/server/src/events.rs b/server/src/events.rs
index b969242534e184d4f0a689543a479670b08a18df..eff80aef0257f706d2341f666e63d6a3d921bf6e 100644
--- a/server/src/events.rs
+++ b/server/src/events.rs
@@ -5,8 +5,6 @@ use serde::{Deserialize, Serialize};
 pub enum Event {
     /// Page view recorded (path → counter in views.json).
     ViewRecorded { path: String, ts: i64 },
-    /// Demo counter bump from `POST /ui` (persisted in the single JSONL log).
-    DemoCounterBumped { ts: i64, value: u64 },
     /// Pairwise comparison vote (replayed into [`crate::reducer::GroupState`] on boot).
     VoteRecorded {
         ts: i64,
diff --git a/server/src/html/mod.rs b/server/src/html/mod.rs
index 5b1d0b5a887d89e7e80796aa7a6c8ed5baaf2782..d69ed962b5c8625bc83c933b1825f2cc1d0868e2 100644
--- a/server/src/html/mod.rs
+++ b/server/src/html/mod.rs
@@ -13,7 +13,7 @@ use crate::{
     form_template::template_json_compact,
     parser_action::ParserAction,
     parser_render::parser_panel,
-    ranking::ranked_items,
+    ranking::ranked_items_cached,
     reducer::GroupState,
     state::AppState,
     ui_action::UI_RPC_FIELD,
@@ -199,10 +199,8 @@ fn layout(title: &str, body: Markup, views: u64, theme: &str, theme_next: &str)
     }
 }
 
-pub fn ranking_panel(group: &mut GroupState) -> Markup {
-    const MAX_ITERS: usize = 10_000;
-    const TOL: f64 = 1e-8;
-    let items = ranked_items(group, MAX_ITERS, TOL);
+pub fn ranking_panel(group: &GroupState) -> Markup {
+    let items = ranked_items_cached(group);
     html! {
         section id="ranking-panel" class="demo-panel" {
             h2 { "Ranking" }
@@ -260,35 +258,6 @@ pub fn vote_panel() -> Markup {
 }
 
 
-pub fn demo_counter_panel(count: u64, event_log_path: &str) -> Markup {
-    let rpc = template_json_compact(&serde_json::json!({ "action": "bump_demo_counter" }))
-        .expect("rpc json");
-    html! {
-        section id="demo-counter-panel" class="demo-panel" {
-            h1 { "sorter2" }
-            p class="muted" {
-                "Pairwise ranking scaffold — votes persist to JSONL and replay on boot."
-            }
-            p class="demo-count" {
-                strong { "Counter: " }
-                span id="demo-count-value" { (count) }
-            }
-            p class="muted small" {
-                "Event log: " code { (event_log_path) }
-            }
-            form method="post" action="/ui" id="demo-bump-form" {
-                input type="hidden" name=(UI_RPC_FIELD) value=(rpc);
-                button type="submit" class="btn-primary" { "Bump (POST /ui → eval JS)" }
-            }
-            p class="muted small" {
-                "Uses hidden "
-                code { "__rpc__" }
-                " JSON + Idiomorph morph — no full page reload."
-            }
-        }
-    }
-}
-
 pub async fn home(
     State(state): State<AppState>,
     jar: CookieJar,
@@ -297,16 +266,15 @@ pub async fn home(
     let path = uri.path().to_string();
     state.views.increment(path.clone());
     let views = state.views.get_views(&path);
-    let count = *state.demo_counter.read().await;
     let theme = theme_from_jar(&jar);
     let theme_next = theme_next_from_uri(&uri);
-    let mut group = state.group.write().await;
+    let group = state.group.read().await;
     let empty_action = ParserAction::suggest(String::new(), None);
     let body = html! {
+        h1 { "sorter2" }
         (parser_panel("", &empty_action))
         (vote_panel())
-        (ranking_panel(&mut group))
-        (demo_counter_panel(count, state.event_log.path().to_string_lossy().as_ref()))
+        (ranking_panel(&group))
     };
     layout("sorter2", body, views, theme, &theme_next)
 }
diff --git a/server/src/lib.rs b/server/src/lib.rs
index 6716c5b282e7980a7a0f03d63ad8b25eda61cc55..fa423640d598f4ba97a5885d228e78d7b97f7a22 100644
--- a/server/src/lib.rs
+++ b/server/src/lib.rs
@@ -9,6 +9,7 @@ pub mod parser_render;
 pub mod path_types;
 pub mod ranking;
 pub mod reducer;
+pub mod settlement;
 pub mod state;
 pub mod ui_action;
 pub mod views;
diff --git a/server/src/ranking.rs b/server/src/ranking.rs
index 89d3280126a8d8f841721ce8cb63ff735d68752a..2d706762792ba9239bb3f1c2e4974a2fde908013 100644
--- a/server/src/ranking.rs
+++ b/server/src/ranking.rs
@@ -91,6 +91,11 @@ pub fn compute_group_ranking(group: &mut GroupState, max_iters: usize, tol: f64)
 
 pub fn ranked_items(group: &mut GroupState, max_iters: usize, tol: f64) -> Vec<RankedItem> {
     compute_group_ranking(group, max_iters, tol);
+    ranked_items_cached(group)
+}
+
+/// Read cached scores without recomputing (HTTP fast path).
+pub fn ranked_items_cached(group: &GroupState) -> Vec<RankedItem> {
     let mut items: Vec<RankedItem> = group
         .idx_to_item
         .iter()
@@ -105,7 +110,12 @@ pub fn ranked_items(group: &mut GroupState, max_iters: usize, tol: f64) -> Vec<R
     items
 }
 
-fn compute_scores_from_edges(n: usize, edges: impl Iterator<Item = ((usize, usize), f64)>, max_iters: usize, tol: f64) -> Vec<f64> {
+pub fn compute_scores_from_edges(
+    n: usize,
+    edges: impl Iterator<Item = ((usize, usize), f64)>,
+    max_iters: usize,
+    tol: f64,
+) -> Vec<f64> {
     if n == 0 {
         return vec![];
     }
diff --git a/server/src/settlement.rs b/server/src/settlement.rs
new file mode 100644
index 0000000000000000000000000000000000000000..1f722ceaea62cda22c28ab71551f259fbf049b81
--- /dev/null
+++ b/server/src/settlement.rs
@@ -0,0 +1,114 @@
+use std::sync::Arc;
+
+use tokio::sync::{mpsc, oneshot, RwLock};
+
+use crate::{
+    event_log::EventLog,
+    events::Event,
+    ranking::compute_scores_from_edges,
+    reducer::{GroupState, VoteData},
+};
+
+const MAX_ITERS: usize = 10_000;
+const TOL: f64 = 1e-8;
+
+pub struct SettlementCommand {
+    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(group: Arc<RwLock<GroupState>>, event_log: Arc<EventLog>) -> Self {
+        let (tx, rx) = mpsc::channel(64);
+        tokio::spawn(settlement_worker(rx, group, event_log));
+        Self { tx }
+    }
+
+    pub async fn record_vote(&self, vote: VoteData, event: Event) -> Result<(), String> {
+        let (reply, rx) = oneshot::channel();
+        self.tx
+            .send(SettlementCommand {
+                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>,
+    group: Arc<RwLock<GroupState>>,
+    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 (edges, n) = {
+            let mut w = group.write().await;
+            for cmd in &batch {
+                w.apply_vote(cmd.vote.clone());
+            }
+            (w.edges.clone(), w.idx_to_item.len())
+        };
+
+        let new_scores = compute_scores_from_edges(
+            n,
+            edges.iter().map(|(&k, &v)| (k, v)),
+            MAX_ITERS,
+            TOL,
+        );
+
+        {
+            let mut w = group.write().await;
+            w.cached_scores = new_scores;
+            w.dirty = false;
+        }
+
+        for cmd in batch {
+            let _ = cmd.reply.send(Ok(()));
+        }
+    }
+}
+
+/// Compute ranking cache from current in-memory edges (startup replay only).
+pub fn warm_ranking_cache(group: &mut GroupState) {
+    if !group.dirty {
+        return;
+    }
+    let n = group.idx_to_item.len();
+    group.cached_scores = compute_scores_from_edges(
+        n,
+        group.edges.iter().map(|(&k, &v)| (k, v)),
+        MAX_ITERS,
+        TOL,
+    );
+    group.dirty = false;
+}
diff --git a/server/src/state.rs b/server/src/state.rs
index 8ec9902e2ecc31cf8208f7ad6365891dc5537eed..1922541a4064c2de1df2d993a461cae783320e05 100644
--- a/server/src/state.rs
+++ b/server/src/state.rs
@@ -6,6 +6,7 @@ use crate::{
     event_log::EventLog,
     events::Event,
     reducer::{GroupState, VoteData},
+    settlement::{warm_ranking_cache, SettlementClient},
     views::ViewStore,
 };
 
@@ -38,8 +39,8 @@ pub struct AppState {
     pub cfg: Arc<AppConfig>,
     pub event_log: Arc<EventLog>,
     pub views: ViewStore,
-    pub demo_counter: Arc<RwLock<u64>>,
     pub group: Arc<RwLock<GroupState>>,
+    settlement: SettlementClient,
 }
 
 impl AppState {
@@ -48,14 +49,10 @@ impl AppState {
         let views_path = format!("{}/views.json", cfg.data_dir);
         let views = ViewStore::new(&views_path);
 
-        let mut demo_counter: u64 = 0;
         let mut group = GroupState::new();
         if let Ok((events, _)) = event_log.load_all().await {
             for ev in events {
                 match ev {
-                    Event::DemoCounterBumped { value, .. } => {
-                        demo_counter = demo_counter.max(value);
-                    }
                     Event::VoteRecorded {
                         ts,
                         a,
@@ -74,30 +71,20 @@ impl AppState {
             }
         }
 
+        warm_ranking_cache(&mut group);
+
+        let group = Arc::new(RwLock::new(group));
+        let settlement = SettlementClient::spawn(group.clone(), event_log.clone());
+
         Self {
             cfg: Arc::new(cfg),
             event_log,
             views,
-            demo_counter: Arc::new(RwLock::new(demo_counter)),
-            group: Arc::new(RwLock::new(group)),
+            group,
+            settlement,
         }
     }
 
-    pub async fn bump_demo_counter(&self) -> u64 {
-        let mut guard = self.demo_counter.write().await;
-        *guard += 1;
-        let value = *guard;
-        drop(guard);
-
-        let ts = crate::html::now_ms();
-        let _ = self
-            .event_log
-            .append(&Event::DemoCounterBumped { ts, value })
-            .await;
-
-        value
-    }
-
     pub async fn record_vote(
         &self,
         a: &str,
@@ -109,23 +96,14 @@ 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 mut group = self.group.write().await;
-            group.apply_vote(vote.clone());
-        }
-
-        let _ = self
-            .event_log
-            .append(&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,
-            })
-            .await
-            .map_err(|e| e.to_string())?;
+        let event = Event::VoteRecorded {
+            ts,
+            a: vote.a.as_str().to_string(),
+            b: vote.b.as_str().to_string(),
+            ratio_left: vote.ratio_left,
+            ratio_right: vote.ratio_right,
+        };
 
-        Ok(())
+        self.settlement.record_vote(vote, event).await
     }
 }
diff --git a/server/src/ui_action.rs b/server/src/ui_action.rs
index 1d488e1ad1d8fd81bd9d016d69255adfe9b22fc8..5d94c84113607b3bcd8d31d03ef5b8e1b87b67a7 100644
--- a/server/src/ui_action.rs
+++ b/server/src/ui_action.rs
@@ -12,8 +12,6 @@ pub const UI_RPC_FIELD: &str = "__rpc__";
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
 #[serde(tag = "action", rename_all = "snake_case")]
 pub enum HtmlUiAction {
-    /// Demo: morph `#demo-counter-panel` after bumping the persisted counter.
-    BumpDemoCounter,
     /// Record a pairwise vote and morph `#ranking-panel`.
     RecordVote {
         a: String,
@@ -52,18 +50,6 @@ pub fn parse_html_ui_from_form(
 mod tests {
     use super::*;
 
-    #[test]
-    fn bump_demo_counter_round_trip() {
-        let template = serde_json::json!({ "action": "bump_demo_counter" });
-        let mut form = HashMap::new();
-        form.insert(
-            UI_RPC_FIELD.to_string(),
-            serde_json::to_string(&template).unwrap(),
-        );
-        let a = parse_html_ui_from_form(&form).unwrap();
-        assert_eq!(a, HtmlUiAction::BumpDemoCounter);
-    }
-
     #[test]
     fn record_vote_round_trip_with_form_holes() {
         let template = serde_json::json!({
diff --git a/server/tests/integration_health.rs b/server/tests/integration_health.rs
index 8a58bc14aac68c779e7ce4ffa57d27b3220e9953..1d816e008b9bf629967e3b3c786c41afefc284e3 100644
--- a/server/tests/integration_health.rs
+++ b/server/tests/integration_health.rs
@@ -38,7 +38,7 @@ async fn healthz_ok() {
 }
 
 #[tokio::test]
-async fn home_has_demo_panel() {
+async fn home_has_main_panels() {
     let (addr, _tmp) = start_test_server().await;
     let client = reqwest::Client::new();
     let html = client
diff --git a/server/tests/integration_ui.rs b/server/tests/integration_ui.rs
index bee79407dec120699a083f1a75adf9291e207fc7..7ede46d681fefbe25b1d98fc33520a185515eb1c 100644
--- a/server/tests/integration_ui.rs
+++ b/server/tests/integration_ui.rs
@@ -25,33 +25,6 @@ async fn start_test_server() -> (SocketAddr, TempDir) {
     (addr, tmp)
 }
 
-#[tokio::test]
-async fn post_ui_bump_returns_javascript_morph() {
-    let (addr, tmp) = start_test_server().await;
-    let rpc = serde_json::json!({ "action": "bump_demo_counter" }).to_string();
-    let mut form = HashMap::new();
-    form.insert(UI_RPC_FIELD.to_string(), rpc);
-
-    let client = reqwest::Client::new();
-    let body = client
-        .post(format!("http://{addr}/ui"))
-        .form(&form)
-        .send()
-        .await
-        .unwrap()
-        .text()
-        .await
-        .unwrap();
-
-    assert!(body.contains("Idiomorph.morph"));
-    assert!(body.contains("demo-counter-panel"));
-    assert!(body.contains("Counter:"));
-
-    let log_path = tmp.path().join("events.jsonl");
-    let log = std::fs::read_to_string(log_path).unwrap();
-    assert!(log.contains("demo_counter_bumped"));
-}
-
 #[tokio::test]
 async fn post_ui_record_vote_morphs_ranking_and_persists() {
     let (addr, tmp) = start_test_server().await;
@@ -90,8 +63,8 @@ async fn post_ui_record_vote_morphs_ranking_and_persists() {
         port: 0,
     };
     let state = create_app_state(cfg).await;
-    let mut group = state.group.write().await;
-    let ranked = sorter2_server::ranking::ranked_items(&mut group, 10_000, 1e-8);
+    let group = state.group.read().await;
+    let ranked = sorter2_server::ranking::ranked_items_cached(&group);
     assert_eq!(ranked.len(), 2);
     assert_eq!(ranked[0].item.as_str(), "alpha");
 }
diff --git a/test/smoke.clj b/test/smoke.clj
index b332324743b58baf3fe96d7477353749f137feae..11887c48282088e140d823a88ba616f6325835b3 100644
--- a/test/smoke.clj
+++ b/test/smoke.clj
@@ -26,7 +26,7 @@
             false))))))
 
 (deftest http-smoke-against-running-server
-  (testing "build, start, healthz, home contains RPC demo"
+  (testing "build, start, healthz, home contains main panels"
     (let [root (repo-root)
           data-dir (.getAbsolutePath (doto (io/file (System/getProperty "java.io.tmpdir")
                                                    (str "sorter2-smoke-" (System/currentTimeMillis)))


Side B — contributor: tommy-mor
Side B — commit message:
[5ca518f6] url refactor

Side B — unified diff (full patch):
diff --git a/Cargo.lock b/Cargo.lock
index 67a09a3b54f778fa7e857fdd589c3ed9c92e1322..ad7e4fe6d4ba2f2b033916194c1ef1ed873f1d46 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1757,6 +1757,7 @@ name = "slug-types"
 version = "0.1.0"
 dependencies = [
  "serde",
+ "url",
 ]
 
 [[package]]
@@ -2272,6 +2273,7 @@ dependencies = [
  "idna",
  "percent-encoding",
  "serde",
+ "serde_derive",
 ]
 
 [[package]]
diff --git a/server/src/api/ui_html.rs b/server/src/api/ui_html.rs
index 606f7d6f97a4428efb90d1e0d544934c861fc4c5..cd3e0f0afd972d9ad9e7e4b92c5fa4c22bb8f620 100644
--- a/server/src/api/ui_html.rs
+++ b/server/src/api/ui_html.rs
@@ -270,10 +270,10 @@ fn post_redirect_location(room: &str, thread_tag: &str) -> String {
         format!("/t/{tag}")
     } else {
         let room = room.trim();
-        let Some((a, b)) = room.split_once('/') else {
+        let Some(seg) = slug_types::room_route_segment(room) else {
             return "/".to_string();
         };
-        format!("/r/{a}/{b}/t/{tag}")
+        format!("/r/{seg}/t/{tag}")
     }
 }
 
diff --git a/server/src/api/write_actor.rs b/server/src/api/write_actor.rs
index cb78d2f3f95b1bc163c1fb064d1d5f657e18000f..f9c3b8bd3fbf8fcb9c035e1a1572fef0b08fa8a9 100644
--- a/server/src/api/write_actor.rs
+++ b/server/src/api/write_actor.rs
@@ -19,13 +19,15 @@ use crate::{
 use super::auth::{issue_token_for_user, verify_token};
 use super::helpers::{now_ms, resolve_item};
 use super::validate::{normalize_room_and_thread, validate_ingest_document};
-use slug_types::RpcResult;
+use slug_types::{room_route_segment, RpcResult, ROOM_SHORT_ID_LEN};
 
 fn gen_short_id() -> String {
     use rand::Rng;
     const ALPHABET: &[u8] = b"0123456789abcdefghijklmnopqrstuvwxyz";
     let mut rng = rand::thread_rng();
-    (0..7).map(|_| ALPHABET[rng.gen_range(0..ALPHABET.len())] as char).collect()
+    (0..ROOM_SHORT_ID_LEN)
+        .map(|_| ALPHABET[rng.gen_range(0..ALPHABET.len())] as char)
+        .collect()
 }
 
 fn parse_capability(s: &str) -> Result<crate::events::ThreadCapability, String> {
@@ -55,8 +57,8 @@ async fn broadcast_web_refresh(state: &AppState, room_key: &str, thread_id: &str
     let feed_id = if room_key == "public" { "thread-feed" } else { "room-thread-feed" };
     let thread_url = if room_key == "public" {
         format!("/t/{thread_id}")
-    } else if let Some((short, slug)) = room_key.split_once('/') {
-        format!("/r/{short}/{slug}/t/{thread_id}")
+    } else if let Some(seg) = room_route_segment(room_key) {
+        format!("/r/{seg}/t/{thread_id}")
     } else {
         format!("/t/{thread_id}")
     };
@@ -78,8 +80,8 @@ async fn broadcast_web_refresh(state: &AppState, room_key: &str, thread_id: &str
     let js = builder.build();
     let mut path_prefixes = vec![if room_key == "public" {
         "/".to_string()
-    } else if let Some((short, slug)) = room_key.split_once('/') {
-        format!("/r/{short}/{slug}")
+    } else if let Some(seg) = room_route_segment(room_key) {
+        format!("/r/{seg}")
     } else {
         "/".to_string()
     }];
diff --git a/server/src/html/forum/nav.rs b/server/src/html/forum/nav.rs
index 0ee33d91160fc5542817b5e3e9ab4fee1d0e600f..48fe11e46731670874ff8b6b05baa6f09ae0b7e4 100644
--- a/server/src/html/forum/nav.rs
+++ b/server/src/html/forum/nav.rs
@@ -1,7 +1,8 @@
 use crate::canonical_path::canonicalize_item;
 use crate::reducer::ScopeId;
+use slug_types::room_route_segment;
 
-/// URL helpers for public `/t/…` and private room threads `/r/{short}/{slug}/t/…`.
+/// URL helpers for public `/t/…` and private room threads `/r/{short}{slug}/t/…`.
 #[derive(Clone)]
 pub struct ThreadNav {
     pub room_wire: String,
@@ -22,18 +23,15 @@ impl ThreadNav {
         }
     }
 
-    /// `room_id` wire form `shortid/slug`.
+    /// `room_id` wire form `shortid/slug` (HTTP uses [`slug_types::room_route_segment`]).
     pub(crate) fn from_room_id(room_id: &str) -> Option<Self> {
-        let (short, slug) = room_id.split_once('/')?;
-        if short.is_empty() || slug.is_empty() {
-            return None;
-        }
+        let room_seg = room_route_segment(room_id)?;
         Some(Self {
             room_wire: room_id.to_string(),
             scope: ScopeId::Room(room_id.to_string()),
-            room_path: format!("/r/{short}/{slug}"),
-            thread_path_prefix: format!("/r/{short}/{slug}/t"),
-            garden_path_prefix: format!("/r/{short}/{slug}/~"),
+            room_path: format!("/r/{room_seg}"),
+            thread_path_prefix: format!("/r/{room_seg}/t"),
+            garden_path_prefix: format!("/r/{room_seg}/~"),
         })
     }
 
diff --git a/server/src/html/forum/post_single.rs b/server/src/html/forum/post_single.rs
index c316f8f836df9d4ef9c05ebd9e54f699540e6d72..473747b3da3d4d7a54b5e0c63165d2533df643e1 100644
--- a/server/src/html/forum/post_single.rs
+++ b/server/src/html/forum/post_single.rs
@@ -93,12 +93,14 @@ pub async fn thread_post_view(
 
 pub async fn room_thread_post_view(
     State(state): State<AppState>,
-    Path((room_short, room_slug, tag, index_str)): Path<(String, String, String, String)>,
+    Path((room_key, tag, index_str)): Path<(String, String, String)>,
     headers: HeaderMap,
     jar: CookieJar,
     uri: Uri,
 ) -> impl IntoResponse {
-    let room_id = format!("{room_short}/{room_slug}");
+    let Some(room_id) = slug_types::room_id_from_route_segment(&room_key) else {
+        return (StatusCode::NOT_FOUND, "bad room path").into_response();
+    };
     let reduced = state.reduced.read().await;
     let user = optional_principal(&headers, &jar, &reduced);
     if !user_can_view_room(&reduced, &room_id, user.as_deref()) {
diff --git a/server/src/html/forum/views.rs b/server/src/html/forum/views.rs
index be5df1745ef580891a167c23c3dd6c06f804f295..1ec421f84335cbfe7f9db775b73a8ed24b197174 100644
--- a/server/src/html/forum/views.rs
+++ b/server/src/html/forum/views.rs
@@ -183,16 +183,18 @@ pub async fn thread_view(
     thread_view_inner(state, tag, q, ThreadNav::public(), headers, jar, uri).await
 }
 
-/// Room thread — `/r/:short/:slug/t/:tag`
+/// Room thread — `/r/:room_key/t/:tag` (`room_key` = `{short}{slug}`).
 pub async fn room_thread_view(
     State(state): State<AppState>,
-    Path((room_short, room_slug, tag)): Path<(String, String, String)>,
+    Path((room_key, tag)): Path<(String, String)>,
     Query(q): Query<ThreadViewQuery>,
     headers: HeaderMap,
     jar: CookieJar,
     uri: Uri,
 ) -> impl IntoResponse {
-    let room_id = format!("{room_short}/{room_slug}");
+    let Some(room_id) = slug_types::room_id_from_route_segment(&room_key) else {
+        return (StatusCode::NOT_FOUND, "bad room path").into_response();
+    };
     let reduced = state.reduced.read().await;
     let user = optional_principal(&headers, &jar, &reduced);
     if !user_can_view_room(&reduced, &room_id, user.as_deref()) {
@@ -226,15 +228,17 @@ pub(super) fn room_not_found_page(jar: &CookieJar, uri: &Uri) -> impl IntoRespon
     (StatusCode::NOT_FOUND, Html(page.into_string()))
 }
 
-/// Private room index — `/r/:short/:slug`
+/// Private room index — `/r/:room_key`
 pub async fn room_page(
     State(state): State<AppState>,
-    Path((room_short, room_slug)): Path<(String, String)>,
+    Path(room_key): Path<String>,
     headers: HeaderMap,
     jar: CookieJar,
     uri: Uri,
 ) -> impl IntoResponse {
-    let room_id = format!("{room_short}/{room_slug}");
+    let Some(room_id) = slug_types::room_id_from_route_segment(&room_key) else {
+        return (StatusCode::NOT_FOUND, "room not found").into_response();
+    };
     let now = now_ms();
     let reduced = state.reduced.read().await;
     if !reduced.rooms.contains(&room_id) {
@@ -266,7 +270,10 @@ pub async fn room_page(
     let audit_cli = format!("npx slugsocial private {room_id} audit");
     drop(reduced);
 
-    let slug_display = room_slug.as_str();
+    let slug_display = room_id
+        .split_once('/')
+        .map(|(_, slug)| slug)
+        .unwrap_or(room_id.as_str());
     let page = layout(
         &format!("room {slug_display} — slug.social"),
         "view-thread",
diff --git a/server/src/html/garden.rs b/server/src/html/garden.rs
index 423f23fd8c9ad7b7f454d6ea7a9a7607a4c9c5b9..e615dd356bcf634232d85610c0a26235ead125fd 100644
--- a/server/src/html/garden.rs
+++ b/server/src/html/garden.rs
@@ -309,12 +309,14 @@ pub async fn external_ontology_path(
 
 pub async fn room_garden_index(
     State(state): State<AppState>,
-    Path((room_short, room_slug)): Path<(String, String)>,
+    Path(room_key): Path<String>,
     headers: HeaderMap,
     jar: CookieJar,
     uri: Uri,
 ) -> impl IntoResponse {
-    let room_id = format!("{room_short}/{room_slug}");
+    let Some(room_id) = slug_types::room_id_from_route_segment(&room_key) else {
+        return (StatusCode::NOT_FOUND, "bad room path").into_response();
+    };
     let Some(nav) = ThreadNav::from_room_id(&room_id) else {
         return (StatusCode::NOT_FOUND, "bad room path").into_response();
     };
@@ -341,12 +343,14 @@ pub async fn room_garden_index(
 
 pub async fn room_external_garden_index(
     State(state): State<AppState>,
-    Path((room_short, room_slug)): Path<(String, String)>,
+    Path(room_key): Path<String>,
     headers: HeaderMap,
     jar: CookieJar,
     uri: Uri,
 ) -> impl IntoResponse {
-    let room_id = format!("{room_short}/{room_slug}");
+    let Some(room_id) = slug_types::room_id_from_route_segment(&room_key) else {
+        return (StatusCode::NOT_FOUND, "bad room path").into_response();
+    };
     let Some(nav) = ThreadNav::from_room_id(&room_id) else {
         return (StatusCode::NOT_FOUND, "bad room path").into_response();
     };
@@ -416,12 +420,14 @@ pub async fn room_external_garden_index(
 
 pub async fn room_external_ontology_path(
     State(state): State<AppState>,
-    Path((room_short, room_slug, path)): Path<(String, String, String)>,
+    Path((room_key, path)): Path<(String, String)>,
     headers: HeaderMap,
     jar: CookieJar,
     uri: Uri,
 ) -> impl IntoResponse {
-    let room_id = format!("{room_short}/{room_slug}");
+    let Some(room_id) = slug_types::room_id_from_route_segment(&room_key) else {
+        return (StatusCode::NOT_FOUND, "bad room path").into_response();
+    };
     let Some(nav) = ThreadNav::from_room_id(&room_id) else {
         return (StatusCode::NOT_FOUND, "bad room path").into_response();
     };
@@ -442,12 +448,14 @@ pub async fn room_external_ontology_path(
 
 pub async fn room_ontology_path(
     State(state): State<AppState>,
-    Path((room_short, room_slug, path)): Path<(String, String, String)>,
+    Path((room_key, path)): Path<(String, String)>,
     headers: HeaderMap,
     jar: CookieJar,
     uri: Uri,
 ) -> impl IntoResponse {
-    let room_id = format!("{room_short}/{room_slug}");
+    let Some(room_id) = slug_types::room_id_from_route_segment(&room_key) else {
+        return (StatusCode::NOT_FOUND, "bad room path").into_response();
+    };
     let Some(nav) = ThreadNav::from_room_id(&room_id) else {
         return (StatusCode::NOT_FOUND, "bad room path").into_response();
     };
diff --git a/server/src/html/search.rs b/server/src/html/search.rs
index 43e6ebf36cf0fe72c96f0f9d850bea51ac094c43..f01732f7edb32c68fcc10c39545c8f56476adb27 100644
--- a/server/src/html/search.rs
+++ b/server/src/html/search.rs
@@ -351,8 +351,8 @@ fn render_search_results(results: &SearchResults, query: &str) -> Markup {
                     ul class="search-posts" {
                         @for r in &results.posts {
                             @let (post_href, post_label) = if let Some((room, tag)) = r.thread.split_once("/#") {
-                                if let Some((short, slug)) = room.split_once('/') {
-                                    (format!("/r/{short}/{slug}/t/{tag}"), format!("{room}/#{tag}"))
+                                if let Some(seg) = slug_types::room_route_segment(room) {
+                                    (format!("/r/{seg}/t/{tag}"), format!("{room}/#{tag}"))
                                 } else {
                                     ("/".to_string(), r.thread.clone())
                                 }
diff --git a/server/src/lib.rs b/server/src/lib.rs
index 9e69c3f4a153527caa77b00ad101aca94b425995..71032f9a0b556097d90f3b403c677e0c86429ee4 100644
--- a/server/src/lib.rs
+++ b/server/src/lib.rs
@@ -79,30 +79,30 @@ pub fn create_app(state: AppState) -> Router {
         .route("/~/*path", get(crate::html::ontology_path))
         .route("/-", get(crate::html::external_garden_index))
         .route("/-/*path", get(crate::html::external_ontology_path))
-        .route("/r/:room_short/:room_slug/~", get(crate::html::room_garden_index))
+        .route("/r/:room_key/~", get(crate::html::room_garden_index))
         .route(
-            "/r/:room_short/:room_slug/~/*path",
+            "/r/:room_key/~/*path",
             get(crate::html::room_ontology_path),
         )
         .route(
-            "/r/:room_short/:room_slug/-",
+            "/r/:room_key/-",
             get(crate::html::room_external_garden_index),
         )
         .route(
-            "/r/:room_short/:room_slug/-/*path",
+            "/r/:room_key/-/*path",
             get(crate::html::room_external_ontology_path),
         )
         .route("/t/:tag/:index", get(crate::html::thread_post_view))
         .route("/t/:tag", get(crate::html::thread_view))
         .route(
-            "/r/:room_short/:room_slug/t/:thread_tag/:index",
+            "/r/:room_key/t/:thread_tag/:index",
             get(crate::html::room_thread_post_view),
         )
         .route(
-            "/r/:room_short/:room_slug/t/:thread_tag",
+            "/r/:room_key/t/:thread_tag",
             get(crate::html::room_thread_view),
         )
-        .route("/r/:room_short/:room_slug", get(crate::html::room_page))
+        .route("/r/:room_key", get(crate::html::room_page))
         .route("/join/:token", get(api::get_join_invite))
         .route("/auth/login", get(api::get_auth_login))
         .route("/auth/callback", get(api::get_auth_callback))
diff --git a/server/tests/integration.rs b/server/tests/integration.rs
index 515c691d04ef3f1f4bdfa8ee911360a43fd2b26e..feb73d475b3fc635d7f16c329d4600718c7472ba 100644
--- a/server/tests/integration.rs
+++ b/server/tests/integration.rs
@@ -1,4 +1,5 @@
 use sha2::{Digest, Sha256};
+use slug_types::room_route_segment;
 use slugsocial_server::{
     event_log::EventLog,
     events::{Event, TokenIssued, UserRegistered},
@@ -607,7 +608,7 @@ async fn test_private_room_thread_urls_use_t_segment() {
         .as_str()
         .unwrap()
         .to_string();
-    let (room_short, room_slug) = room_id.split_once('/').unwrap();
+    let room_seg = room_route_segment(&room_id).unwrap();
 
     let rpc = ui_post_ingest_rpc(&room_id, "main-thread", "private post via web");
     let post = client
@@ -626,7 +627,7 @@ async fn test_private_room_thread_urls_use_t_segment() {
         Some("text/javascript; charset=utf-8")
     );
     let post_js = post.text().await.unwrap();
-    let location = format!("/r/{room_short}/{room_slug}/t/main-thread");
+    let location = format!("/r/{room_seg}/t/main-thread");
     assert!(post_js.contains(&format!("window.location = {:?};", location)));
     assert!(post_js.contains("#room-thread-feed"));
     assert!(post_js.contains("#thread-feed-region"));
@@ -665,7 +666,7 @@ async fn test_private_room_post_links_use_private_garden_routes() {
         .as_str()
         .unwrap()
         .to_string();
-    let (room_short, room_slug) = room_id.split_once('/').unwrap();
+    let room_seg = room_route_segment(&room_id).unwrap();
 
     let rpc = ui_post_ingest_rpc(
         &room_id,
@@ -682,18 +683,18 @@ async fn test_private_room_post_links_use_private_garden_routes() {
     assert_eq!(post.status(), reqwest::StatusCode::OK);
 
     let thread_page = client
-        .get(format!("http://{addr}/r/{room_short}/{room_slug}/t/garden-thread"))
+        .get(format!("http://{addr}/r/{room_seg}/t/garden-thread"))
         .header("Authorization", format!("Bearer {bearer}"))
         .send()
         .await
         .unwrap();
     assert!(thread_page.status().is_success());
     let body = thread_page.text().await.unwrap();
-    assert!(body.contains(&format!("/r/{room_short}/{room_slug}/~/secret/item")));
+    assert!(body.contains(&format!("/r/{room_seg}/~/secret/item")));
     assert!(!body.contains("href=\"/~/secret/item\""));
 
     let garden_page = client
-        .get(format!("http://{addr}/r/{room_short}/{room_slug}/~/secret/item"))
+        .get(format!("http://{addr}/r/{room_seg}/~/secret/item"))
         .header("Authorization", format!("Bearer {bearer}"))
         .send()
         .await
@@ -701,7 +702,7 @@ async fn test_private_room_post_links_use_private_garden_routes() {
     assert!(garden_page.status().is_success());
     let garden_body = garden_page.text().await.unwrap();
     assert!(garden_body.contains("classified"));
-    assert!(garden_body.contains(&format!("/r/{room_short}/{room_slug}/t/garden-thread")));
+    assert!(garden_body.contains(&format!("/r/{room_seg}/t/garden-thread")));
 }
 
 #[tokio::test]
@@ -726,7 +727,7 @@ async fn test_private_room_garden_root_lists_top_level_tilde_children() {
         .as_str()
         .unwrap()
         .to_string();
-    let (room_short, room_slug) = room_id.split_once('/').unwrap();
+    let room_seg = room_route_segment(&room_id).unwrap();
 
     let rpc = ui_post_ingest_rpc(
         &room_id,
@@ -743,7 +744,7 @@ async fn test_private_room_garden_root_lists_top_level_tilde_children() {
     assert_eq!(post.status(), reqwest::StatusCode::OK);
 
     let root_page = client
-        .get(format!("http://{addr}/r/{room_short}/{room_slug}/~"))
+        .get(format!("http://{addr}/r/{room_seg}/~"))
         .header("Authorization", format!("Bearer {bearer}"))
         .send()
         .await
@@ -782,10 +783,10 @@ async fn test_empty_private_room_garden_returns_404() {
         .as_str()
         .unwrap()
         .to_string();
-    let (room_short, room_slug) = room_id.split_once('/').unwrap();
+    let room_seg = room_route_segment(&room_id).unwrap();
 
     let root = client
-        .get(format!("http://{addr}/r/{room_short}/{room_slug}/~"))
+        .get(format!("http://{addr}/r/{room_seg}/~"))
         .header("Authorization", format!("Bearer {bearer}"))
         .send()
         .await
@@ -896,8 +897,8 @@ async fn test_sse_stream_emits_evalable_js_after_post() {
         .as_str()
         .unwrap()
         .to_string();
-    let (room_short, room_slug) = room_id.split_once('/').unwrap();
-    let room_path = format!("/r/{room_short}/{room_slug}");
+    let room_seg = room_route_segment(&room_id).unwrap();
+    let room_path = format!("/r/{room_seg}");
 
     let sse_resp = client
         .get(format!("http://{addr}/sse?path={}", urlencoding::encode(&room_path)))
diff --git a/test/browser_room_delete.clj b/test/browser_room_delete.clj
index 833e3f8aa7f850b60ee59742736143cbf101a07d..764ecaa674798a61c1ffca3859f2a56a91a0e97e 100644
--- a/test/browser_room_delete.clj
+++ b/test/browser_room_delete.clj
@@ -54,7 +54,7 @@
            room-id (get-in create-json ["results" 0 "result" "RoomCreated" "room_id"])
            _ (is (string? room-id) "room id present")
            [room-short room-slug] (str/split room-id #"/" 2)
-           room-path (str "/r/" room-short "/" room-slug)]
+           room-path (str "/r/" room-short room-slug)]
        (core/with-playwright [pw]
          (core/with-browser [browser (core/launch-chromium pw {:headless true :channel "chrome"})]
            (core/with-context [ctx (core/new-context browser)]
diff --git a/test/browser_sse.clj b/test/browser_sse.clj
index 8bb064dbc2dc0feb6caaa67f520a461645958277..678399b79f78ff48b5e77342fa21e69992393834 100644
--- a/test/browser_sse.clj
+++ b/test/browser_sse.clj
@@ -77,7 +77,7 @@
                   (login-user! bob-pg base-url "bob")
 
                    (let [[room-short room-slug] (str/split room-id #"/" 2)
-                         room-url (str base-url "/r/" room-short "/" room-slug)
+                         room-url (str base-url "/r/" room-short room-slug)
                          thread-url (str room-url "/t/sse-thread")]
                     ;; Object under test: slug_ui.js intercepts POST /ui, evals JS, morphs
                     ;; #new-thread-ui-slot (expand compose), then post_ingest redirects to thread.
diff --git a/test/walkthrough_fixture.clj b/test/walkthrough_fixture.clj
index a487ff1ef8548580577914fb33f321586859c9af..f7eb1cacca0317129e9baf68fa4f4e33356ad70f 100644
--- a/test/walkthrough_fixture.clj
+++ b/test/walkthrough_fixture.clj
@@ -88,9 +88,9 @@
      :room {:id room-id
             :short room-short
             :slug room-slug
-            :url (str base-url "/r/" room-short "/" room-slug)
-            :thread_url (str base-url "/r/" room-short "/" room-slug "/t/walkthrough-thread")
-            :garden_url (str base-url "/r/" room-short "/" room-slug "/~/secret/item")}}))
+            :url (str base-url "/r/" room-short room-slug)
+            :thread_url (str base-url "/r/" room-short room-slug "/t/walkthrough-thread")
+            :garden_url (str base-url "/r/" room-short room-slug "/~/secret/item")}}))
 
 (defn- rebase-fixture-summary [saved current-base-url current-google-url current-data-dir]
   (let [inner (:summary saved)
@@ -103,9 +103,9 @@
            :data_dir (str current-data-dir)
            :summary (assoc inner
                            :room (assoc room
-                                         :url (str current-base-url "/r/" rs "/" lg)
-                                         :thread_url (str current-base-url "/r/" rs "/" lg "/t/walkthrough-thread")
-                                         :garden_url (str current-base-url "/r/" rs "/" lg "/~/secret/item"))))))
+                                         :url (str current-base-url "/r/" rs lg)
+                                         :thread_url (str current-base-url "/r/" rs lg "/t/walkthrough-thread")
+                                         :garden_url (str current-base-url "/r/" rs lg "/~/secret/item"))))))
 
 (defn- fixture-log-present? [data-dir]
   (let [p (fs/path data-dir "events.jsonl")]
diff --git a/types/Cargo.toml b/types/Cargo.toml
index 1ed06d483ac7c126516bce27f90e7639c2dfe370..5dc3becf238f23243313dff0484c682a7b225737 100644
--- a/types/Cargo.toml
+++ b/types/Cargo.toml
@@ -5,3 +5,4 @@ edition = "2021"
 
 [dependencies]
 serde = { version = "1.0", features = ["derive"] }
+url = { version = "2.5", features = ["serde"] }
diff --git a/types/src/lib.rs b/types/src/lib.rs
index fce1b5fa5e259a4b86a11cb4d4f7cc9bec3a0aa1..516cf935f15fca97081b39b988da5be894c67725 100644
--- a/types/src/lib.rs
+++ b/types/src/lib.rs
@@ -1,5 +1,7 @@
 use serde::{Deserialize, Serialize};
 
+pub mod room_route;
+pub mod url_normalize;
 pub mod paths;
 pub mod timeago;
 
@@ -8,6 +10,8 @@ pub use paths::{
     CanonicalItemUrl, ForumThreadUrl, GardenItemUrl, RelativePath, SLUG_TILDE_ONTOLOGY_ROOT,
     TildeHttpPathTail, TildeOntologyPath, TildePath, tilde_http_path_to_canonical,
 };
+pub use room_route::{room_id_from_route_segment, room_route_segment, ROOM_SHORT_ID_LEN};
+pub use url_normalize::normalize_http_identity_url;
 
 /// Max characters returned for a garden item body unless `full=true` / `--full` (API + CLI).
 pub const MAX_ITEM_BODY_PREVIEW_CHARS: usize = 100_000;
@@ -657,3 +661,6 @@ pub struct VoteResponse {
     pub ranking: Vec<RankRow>,
     pub next: NextMoves,
 }
+
+#[cfg(test)]
+mod url_identity_tests;
diff --git a/types/src/paths.rs b/types/src/paths.rs
index 8971f599a7ebcf399f60c306d35ee28d0f581194..98787a5fb481a1599556564bbbbd1d54dc693fc3 100644
--- a/types/src/paths.rs
+++ b/types/src/paths.rs
@@ -5,7 +5,7 @@
 //!
 //! - **[`canonicalize_item`] / [`CanonicalItemUrl`]** — graph storage key and DSL form; tilde
 //!   ontology root is always [`SLUG_TILDE_ONTOLOGY_ROOT`] (no `…/~/` trailing slash only).
-//! - **[`TildeHttpPathTail`]** — capture from `GET /~/*path` or `…/r/…/~/…` (the `*path` segment).
+//! - **[`TildeHttpPathTail`]** — capture from `GET /~/*path` or `…/r/{short}{slug}/~/…` (the `*path` segment).
 //! - **`-/…` wire form** — external items; see [`canonicalize_item`] dash branch.
 //! - **[`GardenItemUrl`], [`ForumThreadUrl`]** — JSON / browser href surfaces.
 
@@ -15,6 +15,9 @@ use std::ops::Deref;
 
 use serde::{Deserialize, Serialize};
 
+use crate::room_route::room_route_segment;
+use crate::url_normalize::{host_preserves_dash_path_case, normalize_http_identity_url};
+
 // ---------------------------------------------------------------------------
 // Slug tilde ontology (single storage form for `~/`)
 // ---------------------------------------------------------------------------
@@ -41,6 +44,29 @@ pub fn canonicalize_tag(input: &str) -> String {
     input.trim().trim_start_matches('#').to_lowercase()
 }
 
+fn finalize_external_identity_url(s: String) -> String {
+    if s.starts_with("https://slug.social/") {
+        return s;
+    }
+    let normalized = normalize_http_identity_url(&s).unwrap_or_else(|| s.clone());
+    strip_redundant_root_slash(&normalized).unwrap_or(normalized)
+}
+
+/// `url::Url` serializes bare hosts with a `/` path; we keep host-only items slash-free for stable
+/// keys matching the pre-normalizer spellings.
+fn strip_redundant_root_slash(s: &str) -> Option<String> {
+    let u = url::Url::parse(s).ok()?;
+    if u.path() == "/" && u.query().is_none() && u.fragment().is_none() {
+        let scheme = u.scheme();
+        let host = u.host_str()?;
+        return Some(match u.port() {
+            Some(p) => format!("{scheme}://{host}:{p}"),
+            None => format!("{scheme}://{host}"),
+        });
+    }
+    None
+}
+
 /// Ontology item reference → canonical absolute URL on the slug host.
 pub fn canonicalize_item(input: &str) -> String {
     let s = input.trim();
@@ -57,8 +83,9 @@ pub fn canonicalize_item(input: &str) -> String {
         if host.is_empty() {
             return String::new();
         }
+        let preserve_case = host_preserves_dash_path_case(&host);
         return if tail.is_empty() {
-            format!("https://{}", host)
+            finalize_external_identity_url(format!("https://{}", host))
         } else {
             let path = tail
                 .trim_start_matches('/')
@@ -68,33 +95,35 @@ pub fn canonicalize_item(input: &str) -> String {
                     let t = seg.trim();
                     if t.is_empty() {
                         None
+                    } else if preserve_case {
+                        Some(t.to_string())
                     } else {
                         Some(t.to_lowercase())
                     }
                 })
                 .collect::<Vec<_>>()
                 .join("/");
-            format!("https://{}/{}", host, path)
+            finalize_external_identity_url(format!("https://{}/{}", host, path))
         };
     }
 
     if let Some(rest) = s.strip_prefix("https://") {
         let (host, tail) = rest.split_once('/').map_or((rest, ""), |(h, t)| (h, t));
         let host = host.trim().to_lowercase();
-        if tail.is_empty() {
-            return format!("https://{}", host);
+        return finalize_external_identity_url(if tail.is_empty() {
+            format!("https://{}", host)
         } else {
-            return format!("https://{}/{}", host, tail);
-        }
+            format!("https://{}/{}", host, tail)
+        });
     }
     if let Some(rest) = s.strip_prefix("http://") {
         let (host, tail) = rest.split_once('/').map_or((rest, ""), |(h, t)| (h, t));
         let host = host.trim().to_lowercase();
-        if tail.is_empty() {
-            return format!("http://{}", host);
+        return finalize_external_identity_url(if tail.is_empty() {
+            format!("http://{}", host)
         } else {
-            return format!("http://{}/{}", host, tail);
-        }
+            format!("http://{}/{}", host, tail)
+        });
     }
 
     let is_tilde = s.starts_with("~/");
@@ -319,7 +348,7 @@ impl CanonicalItemUrl {
     }
 }
 
-/// HTTP route capture: path segment after `~/` in `GET /~/*path` or `…/r/…/~/…` (empty = ontology root).
+/// HTTP route capture: path segment after `~/` in `GET /~/*path` or `…/r/{short}{slug}/~/…` (empty = ontology root).
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct TildeHttpPathTail(pub String);
 
@@ -506,12 +535,9 @@ fn garden_href_string(item: &str, room_wire: &str) -> String {
     if room.is_empty() || room == "public" {
         return api_path_or_url(item);
     }
-    let Some((short, slug)) = room.split_once('/') else {
+    let Some(room_seg) = room_route_segment(room) else {
         return api_path_or_url(item);
     };
-    if short.is_empty() || slug.is_empty() {
-        return api_path_or_url(item);
-    }
     let Some(c) = CanonicalItemUrl::parse(item) else {
         return api_path_or_url(item);
     };
@@ -520,19 +546,19 @@ fn garden_href_string(item: &str, room_wire: &str) -> String {
     let root_norm = root.as_str().trim_end_matches('/');
     if let Some(tail) = c.tilde_tail() {
         return if tail.is_empty() {
-            format!("https://slug.social/r/{short}/{slug}/~")
+            format!("https://slug.social/r/{room_seg}/~")
         } else {
-            format!("https://slug.social/r/{short}/{slug}/~/{}", tail)
+            format!("https://slug.social/r/{room_seg}/~/{}", tail)
         };
     }
     if item_norm == root_norm {
-        return format!("https://slug.social/r/{short}/{slug}/~");
+        return format!("https://slug.social/r/{room_seg}/~");
     }
     // External http(s) items use the same `/-/…` namespace under the room garden.
     if c.as_str().starts_with("https://") || c.as_str().starts_with("http://") {
         let tail = c.display_path();
         let tail = tail.strip_prefix("-/").unwrap_or(tail.as_str());
-        return format!("https://slug.social/r/{short}/{slug}/-/{tail}");
+        return format!("https://slug.social/r/{room_seg}/-/{tail}");
     }
     api_path_or_url(item)
 }
@@ -556,12 +582,8 @@ impl ForumThreadUrl {
         let tag = thread_tag.trim().trim_start_matches('#');
         Self(if room.is_empty() || room == "public" {
             format!("https://slug.social/t/{tag}")
-        } else if let Some((short, slug)) = room.split_once('/') {
-            if short.is_empty() || slug.is_empty() {
-                format!("https://slug.social/t/{tag}")
-            } else {
-                format!("https://slug.social/r/{short}/{slug}/t/{tag}")
-            }
+        } else if let Some(room_seg) = room_route_segment(room) {
+            format!("https://slug.social/r/{room_seg}/t/{tag}")
         } else {
             format!("https://slug.social/t/{tag}")
         })
@@ -706,7 +728,7 @@ mod tests {
     fn garden_private_room_prefixes_ontology() {
         assert_eq!(
             GardenItemUrl::from_storage_str("https://slug.social/~/topic/x", "9ab12cd/my-room").as_str(),
-            "https://slug.social/r/9ab12cd/my-room/~/topic/x"
+            "https://slug.social/r/9ab12cdmy-room/~/topic/x"
         );
     }
 
@@ -714,11 +736,11 @@ mod tests {
     fn garden_private_room_ontology_root() {
         assert_eq!(
             GardenItemUrl::from_storage_str("https://slug.social/~", "9ab12cd/my-room").as_str(),
-            "https://slug.social/r/9ab12cd/my-room/~"
+            "https://slug.social/r/9ab12cdmy-room/~"
         );
         assert_eq!(
             GardenItemUrl::from_storage_str("https://slug.social/~/", "9ab12cd/my-room").as_str(),
-            "https://slug.social/r/9ab12cd/my-room/~"
+            "https://slug.social/r/9ab12cdmy-room/~"
         );
     }
 
@@ -727,7 +749,7 @@ mod tests {
         let u = "https://example.com/z";
         assert_eq!(
             GardenItemUrl::from_storage_str(u, "9ab12cd/my-room").as_str(),
-            "https://slug.social/r/9ab12cd/my-room/-/example.com/z"
+            "https://slug.social/r/9ab12cdmy-room/-/example.com/z"
         );
     }
 
@@ -739,7 +761,19 @@ mod tests {
         );
         assert_eq!(
             ForumThreadUrl::from_room_tag("9ab12cd/my-room", "#debate").as_str(),
-            "https://slug.social/r/9ab12cd/my-room/t/debate"
+            "https://slug.social/r/9ab12cdmy-room/t/debate"
+        );
+    }
+
+    #[test]
+    fn canonicalize_youtube_short_links() {
+        assert_eq!(
+            canonicalize_item("https://youtu.be/dQw4w9WgXcQ"),
+            "https://www.youtube.com/watch?v=dQw4w9WgXcQ"
+        );
+        assert_eq!(
+            canonicalize_item("-/youtu.be/dQw4w9WgXcQ"),
+            "https://www.youtube.com/watch?v=dQw4w9WgXcQ"
         );
     }
 
diff --git a/types/src/room_route.rs b/types/src/room_route.rs
new file mode 100644
index 0000000000000000000000000000000000000000..4f4780c88e30f2b28e2cfcd7aee713d39dbd1c66
--- /dev/null
+++ b/types/src/room_route.rs
@@ -0,0 +1,56 @@
+//! HTTP path encoding for private rooms: `/r/{short}{slug}` (short is fixed width).
+
+/// Byte length of the random `short` segment in `short/slug` room ids.
+/// Must match room creation (`gen_short_id`) and [`super::paths`][] URL builders.
+pub const ROOM_SHORT_ID_LEN: usize = 7;
+
+/// `ab12cde/my-room` → `ab12cdemy-room` for a single `/r/…` path segment.
+pub fn room_route_segment(room_id: &str) -> Option<String> {
+    let (short, slug) = room_id.split_once('/')?;
+    if short.len() != ROOM_SHORT_ID_LEN || short.is_empty() || slug.is_empty() {
+        return None;
+    }
+    if !short
+        .bytes()
+        .all(|b| matches!(b, b'0'..=b'9' | b'a'..=b'z'))
+    {
+        return None;
+    }
+    Some(format!("{short}{slug}"))
+}
+
+/// `/r/{short}{slug}` path segment → `short/slug` wire id (inverse of [`room_route_segment`]).
+pub fn room_id_from_route_segment(seg: &str) -> Option<String> {
+    if seg.len() <= ROOM_SHORT_ID_LEN {
+        return None;
+    }
+    let (short, slug) = seg.split_at(ROOM_SHORT_ID_LEN);
+    if short.is_empty() || slug.is_empty() {
+        return None;
+    }
+    if !short
+        .bytes()
+        .all(|b| matches!(b, b'0'..=b'9' | b'a'..=b'z'))
+    {
+        return None;
+    }
+    Some(format!("{short}/{slug}"))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn round_trip_room_segment() {
+        let id = "9ab12cd/my-room";
+        let seg = room_route_segment(id).unwrap();
+        assert_eq!(seg, "9ab12cdmy-room");
+        assert_eq!(room_id_from_route_segment(&seg).as_deref(), Some(id));
+    }
+
+    #[test]
+    fn too_short_segment_rejected() {
+        assert!(room_id_from_route_segment("9ab12cd").is_none());
+    }
+}
diff --git a/types/src/url_identity_tests.rs b/types/src/url_identity_tests.rs
new file mode 100644
index 0000000000000000000000000000000000000000..e2ff0a9a64a88049e31f20979c703777df6a9b65
--- /dev/null
+++ b/types/src/url_identity_tests.rs
@@ -0,0 +1,126 @@
+//! How `url::Url` behaves as `HashMap` keys (`Eq` + `Hash`).
+//!
+//! If `ItemId::External` stores `Url`, these tests are the contract you are buying into
+//! (or the baseline before you add a custom normalization layer).
+
+use std::collections::HashMap;
+use std::hash::{Hash, Hasher};
+use url::Url;
+
+fn hash_one(url: &Url) -> u64 {
+    let mut h = std::collections::hash_map::DefaultHasher::new();
+    url.hash(&mut h);
+    h.finish()
+}
+
+#[test]
+fn identical_parse_strings_are_eq_and_share_hash_bucket() {
+    let a = Url::parse("https://example.com/path").unwrap();
+    let b = Url::parse("https://example.com/path").unwrap();
+    assert_eq!(a, b);
+    assert_eq!(hash_one(&a), hash_one(&b));
+
+    let mut m: HashMap<Url, u32> = HashMap::new();
+    m.insert(a, 1);
+    *m.entry(b).or_default() += 10;
+    assert_eq!(m.len(), 1);
+    assert_eq!(m[&Url::parse("https://example.com/path").unwrap()], 11);
+}
+
+#[test]
+fn host_is_ascii_lowercase_in_eq() {
+    let lower = Url::parse("https://examplE.com/").unwrap();
+    let upper = Url::parse("https://EXAMPLE.com/").unwrap();
+    assert_eq!(lower, upper);
+    assert_eq!(hash_one(&lower), hash_one(&upper));
+}
+
+#[test]
+fn path_space_normalizes_to_percent_encoding_so_forms_merge() {
+    let encoded = Url::parse("https://example.com/a%20b").unwrap();
+    let decoded = Url::parse("https://example.com/a b").unwrap();
+    // Parser normalizes both to the same internal path (`/a%20b`).
+    assert_eq!(encoded, decoded);
+    assert_eq!(hash_one(&encoded), hash_one(&decoded));
+
+    let mut m: HashMap<Url, &str> = HashMap::new();
+    m.insert(encoded, "first");
+    assert_eq!(m.insert(decoded, "second"), Some("first"));
+    assert_eq!(m.len(), 1);
+    assert_eq!(m.values().next().copied(), Some("second"));
+}
+
+#[test]
+fn encoded_slash_in_segment_stays_distinct_from_real_path_separator() {
+    let encoded = Url::parse("https://example.com/a%2Fb").unwrap();
+    let real_slash = Url::parse("https://example.com/a/b").unwrap();
+    assert_ne!(encoded, real_slash);
+    assert_ne!(hash_one(&encoded), hash_one(&real_slash));
+}
+
+#[test]
+fn trailing_slash_on_path_is_significant_for_eq() {
+    let with_slash = Url::parse("https://example.com/foo/").unwrap();
+    let no_slash = Url::parse("https://example.com/foo").unwrap();
+    assert_ne!(with_slash, no_slash);
+    assert_ne!(hash_one(&with_slash), hash_one(&no_slash));
+}
+
+#[test]
+fn default_http_port_80_is_normalized_in_representation() {
+    let explicit = Url::parse("http://example.com:80/").unwrap();
+    let implicit = Url::parse("http://example.com/").unwrap();
+    assert_eq!(explicit, implicit);
+    assert_eq!(hash_one(&explicit), hash_one(&implicit));
+}
+
+#[test]
+fn default_https_port_443_is_normalized() {
+    let explicit = Url::parse("https://example.com:443/foo").unwrap();
+    let implicit = Url::parse("https://example.com/foo").unwrap();
+    assert_eq!(explicit, implicit);
+}
+
+#[test]
+fn non_default_port_is_part_of_identity() {
+    let a = Url::parse("https://example.com:444/").unwrap();
+    let b = Url::parse("https://example.com:445/").unwrap();
+    assert_ne!(a, b);
+}
+
+#[test]
+fn empty_path_vs_slash_only_path_may_differ() {
+    let root = Url::parse("https://example.com").unwrap();
+    let slash = Url::parse("https://example.com/").unwrap();
+    // Both serialize to `https://example.com/` in practice for this crate — verify.
+    assert_eq!(root, slash, "document: root and trailing-slash-only merge for this parser");
+}
+
+#[test]
+fn scheme_case_is_normalized_to_lowercase() {
+    let lower = Url::parse("https://example.com/").unwrap();
+    let upper = Url::parse("HTTPS://example.com/").unwrap();
+    assert_eq!(lower, upper);
+}
+
+#[test]
+fn fragment_is_part_of_eq_and_hash() {
+    let no_frag = Url::parse("https://example.com/a").unwrap();
+    let frag = Url::parse("https://example.com/a#section").unwrap();
+    assert_ne!(
+        no_frag, frag,
+        "#fragment is included in PartialEq — anchors are different HashMap keys"
+    );
+    assert_ne!(hash_one(&no_frag), hash_one(&frag));
+}
+
+#[test]
+fn query_order_and_encoding_can_split_identity() {
+    let a = Url::parse("https://example.com/?b=2&a=1").unwrap();
+    let b = Url::parse("https://example.com/?a=1&b=2").unwrap();
+    assert_ne!(a, b, "query pairs order is preserved in serialization");
+
+    let plus = Url::parse("https://example.com/?q=a+b").unwrap();
+    let encoded = Url::parse("https://example.com/?q=a%20b").unwrap();
+    assert_ne!(plus, encoded, "space as + vs %20 — different keys unless normalized");
+}
diff --git a/types/src/url_normalize.rs b/types/src/url_normalize.rs
new file mode 100644
index 0000000000000000000000000000000000000000..d5bc913f33ad29cd0cd1c7158e28e4fefdbf5f5d
--- /dev/null
+++ b/types/src/url_normalize.rs
@@ -0,0 +1,234 @@
+//! Normalization for external `http(s)://` item identity (not slug tilde ontology).
+//!
+//! Policy (intentional, extend here as new domains need treatment):
+//! - Query pairs sorted lexicographically by **lowercased** key, then value.
+//! - YouTube family → stable `www.youtube.com` shapes where possible.
+
+use url::Url;
+
+/// Whether `-/` → `https://…` path segments should keep original casing (YouTube video IDs are
+/// case-sensitive).
+pub(crate) fn host_preserves_dash_path_case(host: &str) -> bool {
+    let h = host.trim().to_ascii_lowercase();
+    let h = h.strip_prefix("www.").unwrap_or(h.as_str());
+    matches!(
+        h,
+        "youtu.be" | "youtube.com" | "m.youtube.com" | "music.youtube.com"
+    )
+}
+
+/// Normalize external http(s) URLs for stable [`super::paths::canonicalize_item`] output.
+pub fn normalize_http_identity_url(s: &str) -> Option<String> {
+    let mut u = Url::parse(s).ok()?;
+    if !matches!(u.scheme(), "http" | "https") {
+        return None;
+    }
+    rewrite_youtube(&mut u);
+    sort_query_pairs(&mut u);
+    Some(u.to_string())
+}
+
+fn base_host(host: &str) -> String {
+    let lower = host.to_ascii_lowercase();
+    lower
+        .strip_prefix("www.")
+        .unwrap_or(lower.as_str())
+        .to_string()
+}
+
+fn rewrite_youtube(u: &mut Url) {
+    let Some(host_raw) = u.host_str() else {
+        return;
+    };
+    let base = base_host(host_raw);
+    let path = u.path().to_string();
+
+    match base.as_str() {
+        "youtu.be" => {
+            let id = path.trim_start_matches('/').split('/').next().unwrap_or("").to_string();
+            if id.is_empty() {
+                return;
+            }
+            let saved: Vec<(String, String)> = u.query_pairs().into_owned().collect();
+            let Ok(mut out) = Url::parse(&format!("https://www.youtube.com/watch?v={id}")) else {
+                return;
+            };
+            {
+                let mut q = out.query_pairs_mut();
+                for (k, v) in saved {
+                    if k.eq_ignore_ascii_case("v") {
+                        continue;
+                    }
+                    q.append_pair(&k, &v);
+                }
+            }
+            *u = out;
+        }
+        "youtube.com" | "m.youtube.com" => {
+            if base == "m.youtube.com" {
+                let _ = u.set_host(Some("www.youtube.com"));
+            }
+            if path.starts_with("/embed/") {
+                let id = path
+                    .strip_prefix("/embed/")
+                    .unwrap_or("")
+                    .trim_matches('/')
+                    .split('/')
+                    .next()
+                    .unwrap_or("")
+                    .to_string();
+                if id.is_empty() {
+                    return;
+                }
+                let saved: Vec<(String, String)> = u.query_pairs().into_owned().collect();
+                let Ok(mut out) = Url::parse(&format!("https://www.youtube.com/watch?v={id}"))
+                else {
+                    return;
+                };
+                {
+                    let mut q = out.query_pairs_mut();
+                    for (k, v) in saved {
+                        if k.eq_ignore_ascii_case("v") {
+                            continue;
+                        }
+                        q.append_pair(&k, &v);
+                    }
+                }
+                *u = out;
+                return;
+            }
+            if path.starts_with("/v/") {
+                let id = path
+                    .strip_prefix("/v/")
+                    .unwrap_or("")
+                    .trim_matches('/')
+                    .split('/')
+                    .next()
+                    .unwrap_or("")
+                    .to_string();
+                if id.is_empty() {
+                    return;
+                }
+                let saved: Vec<(String, String)> = u.query_pairs().into_owned().collect();
+                let Ok(mut out) = Url::parse(&format!("https://www.youtube.com/watch?v={id}"))
+                else {
+                    return;
+                };
+                {
+                    let mut q = out.query_pairs_mut();
+                    for (k, v) in saved {
+                        if k.eq_ignore_ascii_case("v") {
+                            continue;
+                        }
+                        q.append_pair(&k, &v);
+                    }
+                }
+                *u = out;
+                return;
+            }
+            if path.starts_with("/watch") {
+                let _ = u.set_host(Some("www.youtube.com"));
+                return;
+            }
+            if path.starts_with("/shorts/") {
+                let id = path
+                    .strip_prefix("/shorts/")
+                    .unwrap_or("")
+                    .trim_matches('/')
+                    .split('/')
+                    .next()
+                    .unwrap_or("")
+                    .to_string();
+                if id.is_empty() {
+                    return;
+                }
+                let saved: Vec<(String, String)> = u.query_pairs().into_owned().collect();
+                let Ok(mut out) = Url::parse(&format!("https://www.youtube.com/shorts/{id}"))
+                else {
+                    return;
+                };
+                {
+                    let mut q = out.query_pairs_mut();
+                    for (k, v) in saved {
+                        q.append_pair(&k, &v);
+                    }
+                }
+                *u = out;
+                return;
+            }
+            let _ = u.set_host(Some("www.youtube.com"));
+        }
+        "music.youtube.com" => {}
+        _ => {}
+    }
+}
+
+fn sort_query_pairs(u: &mut Url) {
+    let pairs: Vec<(String, String)> = u.query_pairs().into_owned().collect();
+    if pairs.is_empty() {
+        u.set_query(None);
+        return;
+    }
+    let mut pairs = pairs;
+    pairs.sort_by(|a, b| {
+        a.0.to_ascii_lowercase()
+            .cmp(&b.0.to_ascii_lowercase())
+            .then_with(|| a.1.cmp(&b.1))
+    });
+    u.set_query(None);
+    {
+        let mut q = u.query_pairs_mut();
+        for (k, v) in pairs {
+            q.append_pair(&k, &v);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn youtube_youtu_be_to_watch() {
+        assert_eq!(
+            normalize_http_identity_url("https://youtu.be/dQw4w9WgXcQ").as_deref(),
+            Some("https://www.youtube.com/watch?v=dQw4w9WgXcQ")
+        );
+    }
+
+    #[test]
+    fn youtube_watch_query_sorted() {
+        assert_eq!(
+            normalize_http_identity_url("https://youtube.com/watch?v=Z&a=1&b=2").as_deref(),
+            Some("https://www.youtube.com/watch?a=1&b=2&v=Z")
+        );
+        assert_eq!(
+            normalize_http_identity_url("https://youtube.com/watch?b=2&a=1&v=Z").as_deref(),
+            Some("https://www.youtube.com/watch?a=1&b=2&v=Z")
+        );
+    }
+
+    #[test]
+    fn youtube_embed_to_watch() {
+        assert_eq!(
+            normalize_http_identity_url("https://www.youtube.com/embed/dQw4w9WgXcQ").as_deref(),
+            Some("https://www.youtube.com/watch?v=dQw4w9WgXcQ")
+        );
+    }
+
+    #[test]
+    fn youtube_shorts_host() {
+        assert_eq!(
+            normalize_http_identity_url("https://youtube.com/shorts/AbCdEfGhIjK").as_deref(),
+            Some("https://www.youtube.com/shorts/AbCdEfGhIjK")
+        );
+    }
+
+    #[test]
+    fn arbitrary_query_sorted() {
+        assert_eq!(
+            normalize_http_identity_url("https://example.com/x?z=1&a=2").as_deref(),
+            Some("https://example.com/x?a=2&z=1")
+        );
+    }
+}