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:
[15e1037a] url stuff

Side A — unified diff (full patch):
diff --git a/server/src/url_rules/graph.rs b/server/src/url_rules/graph.rs
new file mode 100644
index 0000000000000000000000000000000000000000..f7ac0f9a551a1727cb2f9294778c283b9885b147
--- /dev/null
+++ b/server/src/url_rules/graph.rs
@@ -0,0 +1,831 @@
+//! Semantic URL graph: DFA traversal on host + path, query in context, generic fallback.
+
+use std::collections::HashMap;
+use std::sync::OnceLock;
+
+use url::Url;
+
+use super::graph_builder::GraphBuilder;
+use super::parse::{normalize_match_host, strip_tracking_query, UrlParts};
+
+#[derive(Debug, Clone, Default)]
+pub struct Context {
+    pub vars: HashMap<String, String>,
+    pub query: HashMap<String, String>,
+}
+
+pub type CanonicalFn = fn(&Context) -> Option<String>;
+
+#[derive(Clone, Copy)]
+pub enum EdgePattern {
+    Literal(&'static str),
+    Variable(&'static str),
+    /// Absorb any trailing segment without leaving this node (e.g. post title slug).
+    AbsorbAny,
+    /// Absorb segment when `cond(seg)` (e.g. subreddit listing suffix).
+    AbsorbIf(fn(&str) -> bool),
+}
+
+pub struct Edge {
+    pub pattern: EdgePattern,
+    pub target: &'static str,
+}
+
+pub struct Node {
+    pub edges: Vec<Edge>,
+    pub canonical: CanonicalFn,
+    pub parent: Option<&'static str>,
+}
+
+impl Node {
+    pub(crate) fn empty() -> Self {
+        Self {
+            edges: Vec::new(),
+            canonical: |_| None,
+            parent: None,
+        }
+    }
+}
+
+pub struct Graph {
+    pub nodes: HashMap<&'static str, Node>,
+}
+
+static GRAPH: OnceLock<Graph> = OnceLock::new();
+
+pub fn graph() -> &'static Graph {
+    GRAPH.get_or_init(build_graph)
+}
+
+impl Graph {
+    pub fn resolve_canonical(&self, parts: &UrlParts) -> Option<String> {
+        let mut query = parts.query.clone();
+        strip_tracking_query(&mut query);
+        let mut ctx = Context {
+            vars: HashMap::new(),
+            query,
+        };
+
+        if let Some(node_id) = self.traverse(parts, &mut ctx) {
+            if let Some(canon) = (self.nodes.get(node_id)?.canonical)(&ctx) {
+                return Some(canon);
+            }
+        }
+        Some(generic_canonical(parts))
+    }
+
+    pub fn breadcrumbs(&self, parts: &UrlParts) -> Vec<String> {
+        let mut query = parts.query.clone();
+        strip_tracking_query(&mut query);
+        let mut ctx = Context {
+            vars: HashMap::new(),
+            query,
+        };
+
+        if let Some(mut node_id) = self.traverse(parts, &mut ctx) {
+            let mut paths = Vec::new();
+            loop {
+                let node = match self.nodes.get(node_id) {
+                    Some(n) => n,
+                    None => break,
+                };
+                if let Some(url) = (node.canonical)(&ctx) {
+                    if paths.last() != Some(&url) {
+                        paths.push(url);
+                    }
+                }
+                match node.parent {
+                    Some(p) => node_id = p,
+                    None => break,
+                }
+            }
+            paths.reverse();
+            if !paths.is_empty() {
+                return paths;
+            }
+        }
+        generic_breadcrumbs(parts)
+    }
+
+    fn traverse(&self, parts: &UrlParts, ctx: &mut Context) -> Option<&'static str> {
+        let host = parts.match_host();
+        let mut node_id = match host.as_str() {
+            "reddit.com" => "reddit_root",
+            "youtube.com" => "youtube_root",
+            "youtu.be" => "youtu_be_entry",
+            _ => return None,
+        };
+
+        let segs: Vec<&str> = parts.path_segments.iter().map(String::as_str).collect();
+        let mut i = 0;
+        while i < segs.len() {
+            let seg = segs[i];
+            match self.follow_edge(node_id, seg, ctx) {
+                Ok(next) => {
+                    node_id = next;
+                    i += 1;
+                }
+                Err(()) => {
+                    if self.try_absorb(node_id, seg) {
+                        i += 1;
+                        continue;
+                    }
+                    return None;
+                }
+            }
+        }
+        Some(node_id)
+    }
+
+    fn follow_edge(
+        &self,
+        node_id: &'static str,
+        seg: &str,
+        ctx: &mut Context,
+    ) -> Result<&'static str, ()> {
+        let node = self.nodes.get(node_id).ok_or(())?;
+        for edge in &node.edges {
+            match edge.pattern {
+                EdgePattern::Literal(lit) if lit == seg => return Ok(edge.target),
+                EdgePattern::Variable(name) => {
+                    ctx.vars.insert(name.to_string(), seg.to_string());
+                    return Ok(edge.target);
+                }
+                EdgePattern::AbsorbAny
+                | EdgePattern::AbsorbIf(_)
+                | EdgePattern::Literal(_)
+                | EdgePattern::Variable(_) => {}
+            }
+        }
+        Err(())
+    }
+
+    fn try_absorb(&self, node_id: &'static str, seg: &str) -> bool {
+        let node = match self.nodes.get(node_id) {
+            Some(n) => n,
+            None => return false,
+        };
+        for edge in &node.edges {
+            match edge.pattern {
+                EdgePattern::AbsorbAny => return true,
+                EdgePattern::AbsorbIf(cond) if cond(seg) => return true,
+                EdgePattern::AbsorbIf(_) | EdgePattern::Literal(_) | EdgePattern::Variable(_) => {}
+            }
+        }
+        false
+    }
+
+    /// Test hook: terminal graph node and captured context after traversal.
+    #[cfg(test)]
+    pub fn traverse_terminal(&self, parts: &UrlParts) -> Option<(&'static str, Context)> {
+        let mut query = parts.query.clone();
+        strip_tracking_query(&mut query);
+        let mut ctx = Context {
+            vars: HashMap::new(),
+            query,
+        };
+        let node = self.traverse(parts, &mut ctx)?;
+        Some((node, ctx))
+    }
+}
+
+fn is_reddit_listing_suffix(seg: &str) -> bool {
+    matches!(seg, "hot" | "top" | "new" | "rising" | "controversial")
+}
+
+/// Percent-encode a path or query fragment so `&`, `?`, etc. cannot break URL structure.
+fn enc(s: &str) -> String {
+    urlencoding::encode(s).into_owned()
+}
+
+// --- Canonical formatters ---
+
+fn canon_reddit_root(_: &Context) -> Option<String> {
+    Some("https://reddit.com".to_string())
+}
+
+fn canon_reddit_r_hub(_: &Context) -> Option<String> {
+    Some("https://reddit.com/r".to_string())
+}
+
+fn canon_reddit_subreddit(ctx: &Context) -> Option<String> {
+    let sub = ctx.vars.get("subreddit")?;
+    Some(format!(
+        "https://reddit.com/r/{}",
+        enc(&sub.to_ascii_lowercase())
+    ))
+}
+
+fn canon_reddit_post(ctx: &Context) -> Option<String> {
+    let sub = ctx.vars.get("subreddit")?.to_ascii_lowercase();
+    let id = ctx.vars.get("post_id")?;
+    Some(format!(
+        "https://reddit.com/r/{}/comments/{}",
+        enc(&sub),
+        enc(id)
+    ))
+}
+
+fn canon_youtube_root(_: &Context) -> Option<String> {
+    Some("https://youtube.com".to_string())
+}
+
+fn canon_youtube_watch(ctx: &Context) -> Option<String> {
+    let v = ctx
+        .query
+        .get("v")
+        .or_else(|| ctx.vars.get("video_id"))?;
+    Some(format!("https://youtube.com/watch?v={}", enc(v)))
+}
+
+fn canon_youtu_be(ctx: &Context) -> Option<String> {
+    let v = ctx.vars.get("vid_id")?;
+    Some(format!("https://youtube.com/watch?v={}", enc(v)))
+}
+
+pub fn build_graph() -> Graph {
+    GraphBuilder::new()
+        .node("reddit_root")
+        .canonical(canon_reddit_root)
+        .edge(EdgePattern::Literal("r"), "reddit_r_hub")
+        .node("reddit_r_hub")
+        .parent("reddit_root")
+        .canonical(canon_reddit_r_hub)
+        .edge(EdgePattern::Variable("subreddit"), "reddit_subreddit")
+        .node("reddit_subreddit")
+        .parent("reddit_r_hub")
+        .canonical(canon_reddit_subreddit)
+        .edge(
+            EdgePattern::AbsorbIf(is_reddit_listing_suffix),
+            "reddit_subreddit",
+        )
+        .edge(EdgePattern::Literal("comments"), "reddit_comments_gate")
+        .node("reddit_comments_gate")
+        .parent("reddit_subreddit")
+        .canonical(canon_reddit_subreddit)
+        .edge(EdgePattern::Variable("post_id"), "reddit_post")
+        .node("reddit_post")
+        .parent("reddit_subreddit")
+        .canonical(canon_reddit_post)
+        .edge(EdgePattern::AbsorbAny, "reddit_post")
+        .node("youtube_root")
+        .canonical(canon_youtube_root)
+        .edge(EdgePattern::Literal("watch"), "youtube_watch")
+        .edge(EdgePattern::Literal("shorts"), "youtube_shorts_gate")
+        .node("youtube_watch")
+        .parent("youtube_root")
+        .canonical(canon_youtube_watch)
+        .node("youtube_shorts_gate")
+        .parent("youtube_root")
+        .canonical(canon_youtube_root)
+        .edge(EdgePattern::Variable("video_id"), "youtube_watch")
+        .node("youtu_be_entry")
+        .canonical(canon_youtube_root)
+        .edge(EdgePattern::Variable("vid_id"), "youtu_be_video")
+        .node("youtu_be_video")
+        .parent("youtube_root")
+        .canonical(canon_youtu_be)
+        .build()
+}
+
+// --- Generic internet fallback ---
+
+pub fn generic_canonical(parts: &UrlParts) -> String {
+    let host = normalize_match_host(&parts.host);
+    let path_segments: Vec<String> = parts.path_segments.clone();
+    let mut query = parts.query.clone();
+    strip_tracking_query(&mut query);
+
+    let mut url = if path_segments.is_empty() {
+        Url::parse(&format!("https://{host}"))
+            .unwrap_or_else(|_| Url::parse("https://invalid").unwrap())
+    } else {
+        let path = format!("/{}", path_segments.join("/"));
+        Url::parse(&format!("https://{host}{path}"))
+            .unwrap_or_else(|_| Url::parse("https://invalid").unwrap())
+    };
+
+    if !query.is_empty() {
+        let mut pairs: Vec<_> = query.iter().collect();
+        pairs.sort_by(|a, b| a.0.cmp(b.0));
+        url.query_pairs_mut().clear();
+        for (k, v) in pairs {
+            url.query_pairs_mut().append_pair(k, v);
+        }
+    }
+
+    let mut s = url.to_string();
+    if path_segments.is_empty() {
+        s = s.trim_end_matches('/').to_string();
+    }
+    s
+}
+
+pub fn generic_breadcrumbs(parts: &UrlParts) -> Vec<String> {
+    let host = normalize_match_host(&parts.host);
+    let n = parts.path_segments.len();
+    let mut out = Vec::new();
+
+    let base = generic_canonical(&UrlParts {
+        scheme: "https".to_string(),
+        host: host.clone(),
+        path_segments: vec![],
+        query: HashMap::new(),
+    });
+    out.push(base);
+
+    for i in 0..n {
+        let segs: Vec<String> = parts.path_segments[..=i].to_vec();
+        let url = generic_canonical(&UrlParts {
+            scheme: "https".to_string(),
+            host: host.clone(),
+            path_segments: segs,
+            query: HashMap::new(),
+        });
+        if out.last() != Some(&url) {
+            out.push(url);
+        }
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::url_rules::parse::test_parts;
+
+    fn g() -> &'static Graph {
+        graph()
+    }
+
+    fn canon(parts: &UrlParts) -> String {
+        g().resolve_canonical(parts).unwrap()
+    }
+
+    fn crumbs(parts: &UrlParts) -> Vec<String> {
+        g().breadcrumbs(parts)
+    }
+
+    fn terminal(parts: &UrlParts) -> Option<&'static str> {
+        g().traverse_terminal(parts).map(|(n, _)| n)
+    }
+
+    fn vars(parts: &UrlParts) -> HashMap<String, String> {
+        g().traverse_terminal(parts)
+            .map(|(_, c)| c.vars)
+            .unwrap_or_default()
+    }
+
+    #[test]
+    fn youtu_be_malicious_segment_encoded_not_injected() {
+        let p = test_parts("youtu.be", &["abc&t=1"], &[]);
+        assert_eq!(canon(&p), "https://youtube.com/watch?v=abc%26t%3D1");
+        assert!(!canon(&p).contains("abc&t=1"));
+    }
+
+    #[test]
+    fn youtube_query_v_encoded() {
+        let p = test_parts("youtube.com", &["watch"], &[("v", "a&b=c")]);
+        assert_eq!(canon(&p), "https://youtube.com/watch?v=a%26b%3Dc");
+    }
+
+    #[test]
+    fn absorb_patterns_live_on_edges_not_in_engine() {
+        let g = build_graph();
+        let sub = g.nodes.get("reddit_subreddit").unwrap();
+        assert!(sub
+            .edges
+            .iter()
+            .any(|e| matches!(e.pattern, EdgePattern::AbsorbIf(_))));
+        let post = g.nodes.get("reddit_post").unwrap();
+        assert!(post
+            .edges
+            .iter()
+            .any(|e| matches!(e.pattern, EdgePattern::AbsorbAny)));
+    }
+
+    #[test]
+    fn builder_rejects_missing_parent() {
+        let result = std::panic::catch_unwind(|| {
+            GraphBuilder::new()
+                .node("orphan")
+                .parent("nonexistent_parent")
+                .build();
+        });
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn generic_canonical_forces_https_and_strips_www() {
+        let p = test_parts("www.example.com", &["blog", "post"], &[]);
+        assert_eq!(canon(&p), "https://example.com/blog/post");
+    }
+
+    #[test]
+    fn generic_canonical_sorts_query_keys() {
+        let p = test_parts("example.com", &["search"], &[("q", "rust"), ("page", "2")]);
+        assert_eq!(canon(&p), "https://example.com/search?page=2&q=rust");
+    }
+
+    #[test]
+    fn generic_canonical_strips_tracking_from_query() {
+        let p = test_parts(
+            "news.ycombinator.com",
+            &["item"],
+            &[("id", "1"), ("utm_medium", "social")],
+        );
+        assert_eq!(canon(&p), "https://news.ycombinator.com/item?id=1");
+    }
+
+    #[test]
+    fn generic_breadcrumbs_cumulative_path() {
+        let p = test_parts("paulgraham.com", &["articles", "lisp.html"], &[]);
+        assert_eq!(
+            crumbs(&p),
+            vec![
+                "https://paulgraham.com",
+                "https://paulgraham.com/articles",
+                "https://paulgraham.com/articles/lisp.html"
+            ]
+        );
+    }
+
+    #[test]
+    fn generic_breadcrumbs_domain_only() {
+        let p = test_parts("example.com", &[], &[]);
+        assert_eq!(crumbs(&p), vec!["https://example.com"]);
+    }
+
+    #[test]
+    fn unknown_host_uses_generic_not_graph() {
+        let p = test_parts("hackernews.com", &["item", "123"], &[]);
+        assert_eq!(terminal(&p), None);
+        assert_eq!(canon(&p), "https://hackernews.com/item/123");
+    }
+
+    #[test]
+    fn traverse_captures_subreddit_variable() {
+        let p = test_parts("reddit.com", &["r", "Rust"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_subreddit"));
+        assert_eq!(vars(&p).get("subreddit").map(String::as_str), Some("Rust"));
+    }
+
+    #[test]
+    fn traverse_captures_post_id() {
+        let p = test_parts("reddit.com", &["r", "aww", "comments", "abc123"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_post"));
+        assert_eq!(vars(&p).get("post_id").map(String::as_str), Some("abc123"));
+    }
+
+    #[test]
+    fn traverse_absorbs_listing_suffix_stays_on_subreddit() {
+        let p = test_parts("reddit.com", &["r", "rust", "hot"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_subreddit"));
+        assert_eq!(canon(&p), "https://reddit.com/r/rust");
+    }
+
+    #[test]
+    fn traverse_absorbs_all_listing_suffixes() {
+        for suffix in ["hot", "top", "new", "rising", "controversial"] {
+            let p = test_parts("reddit.com", &["r", "test", suffix], &[]);
+            assert_eq!(terminal(&p), Some("reddit_subreddit"), "suffix {suffix}");
+            assert_eq!(canon(&p), "https://reddit.com/r/test", "suffix {suffix}");
+        }
+    }
+
+    #[test]
+    fn traverse_absorbs_post_title_slug() {
+        let p = test_parts(
+            "reddit.com",
+            &["r", "rust", "comments", "aaa", "my_great_post_title"],
+            &[],
+        );
+        assert_eq!(terminal(&p), Some("reddit_post"));
+        assert_eq!(canon(&p), "https://reddit.com/r/rust/comments/aaa");
+    }
+
+    #[test]
+    fn traverse_unknown_segment_falls_back_to_generic() {
+        let p = test_parts("reddit.com", &["r", "rust", "wiki", "faq"], &[]);
+        assert_eq!(terminal(&p), None);
+        assert_eq!(canon(&p), "https://reddit.com/r/rust/wiki/faq");
+    }
+
+    #[test]
+    fn traverse_youtube_watch_requires_v_in_query() {
+        let p = test_parts("youtube.com", &["watch"], &[("v", "xyz")]);
+        assert_eq!(terminal(&p), Some("youtube_watch"));
+    }
+
+    #[test]
+    fn traverse_youtu_be_captures_vid_id() {
+        let p = test_parts("youtu.be", &["dQw4w9WgXcQ"], &[]);
+        assert_eq!(terminal(&p), Some("youtu_be_video"));
+        assert_eq!(vars(&p).get("vid_id").map(String::as_str), Some("dQw4w9WgXcQ"));
+    }
+
+    #[test]
+    fn traverse_shorts_sets_video_id_var() {
+        let p = test_parts("youtube.com", &["shorts", "abc99"], &[]);
+        assert_eq!(terminal(&p), Some("youtube_watch"));
+        assert_eq!(vars(&p).get("video_id").map(String::as_str), Some("abc99"));
+    }
+
+    #[test]
+    fn reddit_domain_canonical() {
+        let p = test_parts("reddit.com", &[], &[]);
+        assert_eq!(canon(&p), "https://reddit.com");
+    }
+
+    #[test]
+    fn reddit_r_hub_canonical() {
+        let p = test_parts("reddit.com", &["r"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_r_hub"));
+        assert_eq!(canon(&p), "https://reddit.com/r");
+    }
+
+    #[test]
+    fn reddit_subreddit_lowercases_name() {
+        let p = test_parts("reddit.com", &["r", "AmITheAsshole"], &[]);
+        assert_eq!(canon(&p), "https://reddit.com/r/amitheasshole");
+    }
+
+    #[test]
+    fn reddit_host_aliases_old_new_www() {
+        for host in ["old.reddit.com", "new.reddit.com", "www.reddit.com"] {
+            let p = test_parts(host, &["r", "rust"], &[]);
+            assert_eq!(canon(&p), "https://reddit.com/r/rust", "host {host}");
+        }
+    }
+
+    #[test]
+    fn reddit_post_strips_slug_and_query() {
+        let p = test_parts(
+            "old.reddit.com",
+            &["r", "Rust", "comments", "1abc", "title_slug_here"],
+            &[("sort", "new")],
+        );
+        assert_eq!(canon(&p), "https://reddit.com/r/rust/comments/1abc");
+    }
+
+    #[test]
+    fn reddit_post_multiple_slugs_absorbed() {
+        let p = test_parts(
+            "reddit.com",
+            &["r", "x", "comments", "id1", "slug1", "extra"],
+            &[],
+        );
+        assert_eq!(canon(&p), "https://reddit.com/r/x/comments/id1");
+    }
+
+    #[test]
+    fn reddit_listing_with_query_only() {
+        let p = test_parts("www.reddit.com", &["r", "programming"], &[("sort", "top")]);
+        assert_eq!(canon(&p), "https://reddit.com/r/programming");
+    }
+
+    #[test]
+    fn reddit_subreddit_breadcrumbs_include_r_hub() {
+        let p = test_parts("reddit.com", &["r", "movies"], &[]);
+        assert_eq!(
+            crumbs(&p),
+            vec![
+                "https://reddit.com",
+                "https://reddit.com/r",
+                "https://reddit.com/r/movies"
+            ]
+        );
+    }
+
+    #[test]
+    fn reddit_post_breadcrumbs_skip_comments_node() {
+        let p = test_parts("reddit.com", &["r", "aww", "comments", "1trnvdl"], &[]);
+        let c = crumbs(&p);
+        assert!(!c.iter().any(|u| u.ends_with("/comments")));
+        assert_eq!(
+            c.last().map(String::as_str),
+            Some("https://reddit.com/r/aww/comments/1trnvdl")
+        );
+        assert!(c.contains(&"https://reddit.com/r/aww".to_string()));
+    }
+
+    #[test]
+    fn reddit_post_parent_is_subreddit_not_comments() {
+        let p = test_parts("reddit.com", &["r", "aww", "comments", "1trnvdl"], &[]);
+        let c = crumbs(&p);
+        let parent = c.get(c.len() - 2).unwrap();
+        assert_eq!(parent, "https://reddit.com/r/aww");
+    }
+
+    #[test]
+    fn reddit_domain_parent_is_none_in_breadcrumb_chain() {
+        let p = test_parts("reddit.com", &[], &[]);
+        assert_eq!(crumbs(&p), vec!["https://reddit.com"]);
+    }
+
+    #[test]
+    fn youtube_watch_canonical_uses_v_only() {
+        let p = test_parts("youtube.com", &["watch"], &[("v", "abc"), ("t", "99")]);
+        assert_eq!(canon(&p), "https://youtube.com/watch?v=abc");
+    }
+
+    #[test]
+    fn youtube_query_order_independent() {
+        let a = test_parts("youtube.com", &["watch"], &[("v", "abc"), ("t", "4")]);
+        let b = test_parts("youtube.com", &["watch"], &[("t", "4"), ("v", "abc")]);
+        assert_eq!(canon(&a), canon(&b));
+    }
+
+    #[test]
+    fn youtube_host_aliases() {
+        for host in ["www.youtube.com", "m.youtube.com"] {
+            let p = test_parts(host, &["watch"], &[("v", "x")]);
+            assert_eq!(canon(&p), "https://youtube.com/watch?v=x", "host {host}");
+        }
+    }
+
+    #[test]
+    fn youtube_shorts_canonical_matches_watch() {
+        let shorts = test_parts("youtube.com", &["shorts", "vid123"], &[]);
+        let watch = test_parts("youtube.com", &["watch"], &[("v", "vid123")]);
+        assert_eq!(canon(&shorts), canon(&watch));
+        assert_eq!(canon(&shorts), "https://youtube.com/watch?v=vid123");
+    }
+
+    #[test]
+    fn youtu_be_matches_youtube_watch() {
+        let be = test_parts("youtu.be", &["dQw4w9WgXcQ"], &[]);
+        let watch = test_parts("youtube.com", &["watch"], &[("v", "dQw4w9WgXcQ")]);
+        assert_eq!(canon(&be), canon(&watch));
+    }
+
+    #[test]
+    fn youtube_breadcrumbs_domain_then_watch() {
+        let p = test_parts("youtube.com", &["watch"], &[("v", "abc")]);
+        assert_eq!(
+            crumbs(&p),
+            vec!["https://youtube.com", "https://youtube.com/watch?v=abc"]
+        );
+    }
+
+    #[test]
+    fn youtu_be_breadcrumbs_include_youtube_domain() {
+        let p = test_parts("youtu.be", &["abc"], &[]);
+        let c = crumbs(&p);
+        assert_eq!(c.first().map(String::as_str), Some("https://youtube.com"));
+        assert_eq!(
+            c.last().map(String::as_str),
+            Some("https://youtube.com/watch?v=abc")
+        );
+    }
+
+    #[test]
+    fn parsed_urls_match_hand_built_parts() {
+        let raw = "https://www.reddit.com/r/rust/comments/aaa/title/?utm=x";
+        let parsed = UrlParts::parse(raw).unwrap();
+        let hand = test_parts(
+            "www.reddit.com",
+            &["r", "rust", "comments", "aaa", "title"],
+            &[("utm", "x")],
+        );
+        assert_eq!(canon(&parsed), canon(&hand));
+    }
+
+    #[test]
+    fn equivalence_cluster_youtube_formats() {
+        let urls = [
+            "https://youtu.be/abc123",
+            "https://www.youtube.com/watch?v=abc123",
+            "https://youtube.com/watch?v=abc123&t=1",
+            "https://m.youtube.com/watch?t=1&v=abc123",
+        ];
+        let canonical: Vec<_> = urls
+            .iter()
+            .map(|u| canon(&UrlParts::parse(u).unwrap()))
+            .collect();
+        assert!(canonical.iter().all(|c| *c == "https://youtube.com/watch?v=abc123"));
+    }
+
+    #[test]
+    fn equivalence_cluster_reddit_post_formats() {
+        let urls = [
+            "https://old.reddit.com/r/Rust/comments/aaa/slug/",
+            "reddit.com/r/rust/comments/aaa/other_slug",
+            "https://reddit.com/r/RUST/comments/aaa",
+        ];
+        let canonical: Vec<_> = urls
+            .iter()
+            .map(|u| canon(&UrlParts::parse(u).unwrap()))
+            .collect();
+        assert!(
+            canonical
+                .iter()
+                .all(|c| *c == "https://reddit.com/r/rust/comments/aaa")
+        );
+    }
+
+    #[test]
+    fn graph_nodes_all_have_valid_parent_links() {
+        let g = build_graph();
+        for (id, node) in &g.nodes {
+            if let Some(parent) = node.parent {
+                assert!(g.nodes.contains_key(parent), "node {id} parent {parent}");
+            }
+        }
+    }
+
+    #[test]
+    fn graph_terminal_canonical_always_succeeds_for_reddit_paths() {
+        let cases: &[(&[&str], &str)] = &[
+            (&["r", "rust"], "https://reddit.com/r/rust"),
+            (
+                &["r", "rust", "comments", "x"],
+                "https://reddit.com/r/rust/comments/x",
+            ),
+        ];
+        for (segs, want) in cases {
+            let p = test_parts("reddit.com", segs, &[]);
+            assert_eq!(canon(&p), *want);
+        }
+    }
+
+    #[test]
+    fn breadcrumb_parent_walk_matches_parent_url_semantics() {
+        let p = test_parts("reddit.com", &["r", "aww", "comments", "id1"], &[]);
+        let c = crumbs(&p);
+        assert_eq!(c.len(), 4);
+        assert_eq!(
+            c.get(c.len() - 2).map(String::as_str),
+            Some("https://reddit.com/r/aww")
+        );
+    }
+
+    #[test]
+    fn youtube_watch_without_v_falls_back_to_generic() {
+        let p = test_parts("youtube.com", &["watch"], &[]);
+        assert_eq!(terminal(&p), Some("youtube_watch"));
+        assert_eq!(canon(&p), "https://youtube.com/watch");
+    }
+
+    #[test]
+    fn reddit_only_comments_path_stops_at_gate() {
+        let p = test_parts("reddit.com", &["r", "rust", "comments"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_comments_gate"));
+        assert_eq!(canon(&p), "https://reddit.com/r/rust");
+    }
+
+    #[test]
+    fn generic_deep_path_many_segments() {
+        let segs: Vec<&str> = (0..10)
+            .map(|i| match i {
+                0 => "a",
+                1 => "b",
+                2 => "c",
+                3 => "d",
+                4 => "e",
+                5 => "f",
+                6 => "g",
+                7 => "h",
+                8 => "i",
+                _ => "j",
+            })
+            .collect();
+        let p = test_parts("site.com", &segs, &[]);
+        assert_eq!(crumbs(&p).len(), 11);
+    }
+
+    #[test]
+    fn traverse_literal_r_required_for_subreddit() {
+        let p = test_parts("reddit.com", &["rust"], &[]);
+        assert_eq!(terminal(&p), None);
+    }
+
+    #[test]
+    fn http_scheme_upgraded_via_generic_fallback_host() {
+        let parsed = UrlParts::parse("http://example.com/page").unwrap();
+        assert_eq!(canon(&parsed), "https://example.com/page");
+    }
+
+    #[test]
+    fn each_graph_node_canonical_is_invokable() {
+        let g = build_graph();
+        let empty = Context::default();
+        for (id, node) in &g.nodes {
+            let _ = (node.canonical)(&empty);
+            let _ = id;
+        }
+    }
+
+    #[test]
+    fn reddit_double_listing_suffix_both_absorbed() {
+        let p = test_parts("reddit.com", &["r", "rust", "hot", "new"], &[]);
+        assert_eq!(terminal(&p), Some("reddit_subreddit"));
+        assert_eq!(canon(&p), "https://reddit.com/r/rust");
+    }
+
+    #[test]
+    fn youtu_be_empty_path_stays_at_entry() {
+        let p = test_parts("youtu.be", &[], &[]);
+        assert_eq!(terminal(&p), Some("youtu_be_entry"));
+    }
+}
diff --git a/server/src/url_rules/graph_builder.rs b/server/src/url_rules/graph_builder.rs
new file mode 100644
index 0000000000000000000000000000000000000000..243204ad5ca514fff459057956080cacb5bf38e2
--- /dev/null
+++ b/server/src/url_rules/graph_builder.rs
@@ -0,0 +1,73 @@
+//! Declarative construction of the URL graph with build-time link validation.
+
+use std::collections::HashMap;
+
+use super::graph::{CanonicalFn, Edge, EdgePattern, Graph, Node};
+
+pub struct GraphBuilder {
+    nodes: HashMap<&'static str, Node>,
+    current: Option<&'static str>,
+}
+
+impl GraphBuilder {
+    pub fn new() -> Self {
+        Self {
+            nodes: HashMap::new(),
+            current: None,
+        }
+    }
+
+    pub fn node(mut self, id: &'static str) -> Self {
+        self.nodes.entry(id).or_insert_with(Node::empty);
+        self.current = Some(id);
+        self
+    }
+
+    pub fn canonical(mut self, f: CanonicalFn) -> Self {
+        let id = self.current.expect("canonical() without node()");
+        self.nodes.get_mut(id).expect("node missing").canonical = f;
+        self
+    }
+
+    pub fn parent(mut self, parent_id: &'static str) -> Self {
+        let id = self.current.expect("parent() without node()");
+        self.nodes.get_mut(id).expect("node missing").parent = Some(parent_id);
+        self
+    }
+
+    pub fn edge(mut self, pattern: EdgePattern, target: &'static str) -> Self {
+        let id = self.current.expect("edge() without node()");
+        self.nodes
+            .get_mut(id)
+            .expect("node missing")
+            .edges
+            .push(Edge { pattern, target });
+        self
+    }
+
+    pub fn build(self) -> Graph {
+        for (id, node) in &self.nodes {
+            if let Some(parent) = node.parent {
+                assert!(
+                    self.nodes.contains_key(parent),
+                    "node {id}: parent {parent} does not exist"
+                );
+            }
+            for edge in &node.edges {
+                if !matches!(
+                    edge.pattern,
+                    EdgePattern::AbsorbAny | EdgePattern::AbsorbIf(_)
+                ) {
+                    assert!(
+                        self.nodes.contains_key(edge.target),
+                        "node {id}: edge target {} does not exist",
+                        edge.target
+                    );
+                }
+            }
+        }
+        Graph {
+            nodes: self.nodes,
+        }
+    }
+}
diff --git a/server/src/url_rules/mod.rs b/server/src/url_rules/mod.rs
index 9e1445346ce77a49dd6a7e7713bf9c57aef353cc..ba4ac662acc7bd4d50ee34613eb7eb6fccbfb17b 100644
--- a/server/src/url_rules/mod.rs
+++ b/server/src/url_rules/mod.rs
@@ -1,6 +1,7 @@
 //! URL canonicalization and hierarchy via a semantic graph (DFA + generic fallback).
 
 mod graph;
+mod graph_builder;
 mod parse;
 mod registry;
 
diff --git a/server/src/url_rules/parse.rs b/server/src/url_rules/parse.rs
new file mode 100644
index 0000000000000000000000000000000000000000..19d0c82feb718817168b8b445fcbfa39cf6aa6ba
--- /dev/null
+++ b/server/src/url_rules/parse.rs
@@ -0,0 +1,169 @@
+//! Parse raw strings into host, path segments, and query (order-independent).
+
+use std::collections::HashMap;
+
+use url::Url;
+
+#[derive(Debug, Clone)]
+pub struct UrlParts {
+    pub scheme: String,
+    pub host: String,
+    pub path_segments: Vec<String>,
+    pub query: HashMap<String, String>,
+}
+
+impl UrlParts {
+    pub fn parse(raw: &str) -> Option<Self> {
+        let trimmed = raw.trim();
+        if trimmed.is_empty() {
+            return None;
+        }
+
+        let with_scheme = if trimmed.contains("://") {
+            trimmed.to_string()
+        } else if trimmed.starts_with("r/") || trimmed.starts_with("/r/") {
+            let rest = trimmed.trim_start_matches('/').trim_start_matches("r/");
+            format!("https://reddit.com/r/{rest}")
+        } else if trimmed.contains('.') && !trimmed.starts_with('/') {
+            format!("https://{trimmed}")
+        } else {
+            trimmed.to_string()
+        };
+
+        let url = Url::parse(&with_scheme).ok()?;
+        let host = url.host_str()?.to_string();
+        let path_segments: Vec<String> = url
+            .path_segments()
+            .map(|segs| segs.filter(|s| !s.is_empty()).map(str::to_string).collect())
+            .unwrap_or_default();
+
+        let mut query = HashMap::new();
+        for (k, v) in url.query_pairs() {
+            query.insert(k.into_owned(), v.into_owned());
+        }
+
+        Some(Self {
+            scheme: url.scheme().to_string(),
+            path_segments,
+            query,
+            host,
+        })
+    }
+
+    /// Host normalized for graph entry matching (lowercase, aliases).
+    pub fn match_host(&self) -> String {
+        normalize_match_host(&self.host)
+    }
+}
+
+pub fn normalize_match_host(host: &str) -> String {
+    let h = host
+        .strip_prefix("www.")
+        .unwrap_or(host)
+        .to_ascii_lowercase();
+    match h.as_str() {
+        "old.reddit.com" | "new.reddit.com" => "reddit.com".to_string(),
+        "m.youtube.com" => "youtube.com".to_string(),
+        _ => h,
+    }
+}
+
+pub fn strip_tracking_query(query: &mut HashMap<String, String>) {
+    query.retain(|k, _| {
+        let lower = k.to_ascii_lowercase();
+        !(lower.starts_with("utm_")
+            || matches!(
+                lower.as_str(),
+                "fbclid" | "gclid" | "ref" | "ref_src" | "ref_source" | "mc_cid" | "mc_eid"
+            ))
+    });
+}
+
+#[cfg(test)]
+pub(crate) fn test_parts(host: &str, segs: &[&str], query: &[(&str, &str)]) -> UrlParts {
+    UrlParts {
+        scheme: "https".to_string(),
+        host: host.to_string(),
+        path_segments: segs.iter().map(|s| (*s).to_string()).collect(),
+        query: query
+            .iter()
+            .map(|(k, v)| (k.to_string(), v.to_string()))
+            .collect(),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_full_url_splits_host_path_query() {
+        let p = UrlParts::parse("https://www.youtube.com/watch?v=abc&t=4").unwrap();
+        assert_eq!(p.host, "www.youtube.com");
+        assert_eq!(p.path_segments, vec!["watch"]);
+        assert_eq!(p.query.get("v").map(String::as_str), Some("abc"));
+        assert_eq!(p.query.get("t").map(String::as_str), Some("4"));
+    }
+
+    #[test]
+    fn parse_r_shortcut_expands_to_reddit() {
+        let p = UrlParts::parse("r/rust").unwrap();
+        assert_eq!(p.match_host(), "reddit.com");
+        assert_eq!(p.path_segments, vec!["r", "rust"]);
+    }
+
+    #[test]
+    fn parse_slash_r_shortcut() {
+        let p = UrlParts::parse("/r/aww").unwrap();
+        assert_eq!(p.path_segments, vec!["r", "aww"]);
+    }
+
+    #[test]
+    fn parse_schemeless_host_path() {
+        let p = UrlParts::parse("reddit.com/r/rust/comments/aaa/slug").unwrap();
+        assert_eq!(p.match_host(), "reddit.com");
+        assert_eq!(
+            p.path_segments,
+            vec!["r", "rust", "comments", "aaa", "slug"]
+        );
+    }
+
+    #[test]
+    fn parse_empty_returns_none() {
+        assert!(UrlParts::parse("").is_none());
+        assert!(UrlParts::parse("   ").is_none());
+    }
+
+    #[test]
+    fn normalize_match_host_reddit_aliases() {
+        assert_eq!(normalize_match_host("old.reddit.com"), "reddit.com");
+        assert_eq!(normalize_match_host("NEW.reddit.com"), "reddit.com");
+        assert_eq!(normalize_match_host("www.reddit.com"), "reddit.com");
+    }
+
+    #[test]
+    fn normalize_match_host_youtube_aliases() {
+        assert_eq!(normalize_match_host("m.youtube.com"), "youtube.com");
+        assert_eq!(normalize_match_host("www.youtube.com"), "youtube.com");
+    }
+
+    #[test]
+    fn strip_tracking_query_removes_known_params() {
+        let mut q = HashMap::from([
+            ("v".into(), "1".into()),
+            ("utm_source".into(), "x".into()),
+            ("fbclid".into(), "y".into()),
+            ("ref".into(), "z".into()),
+        ]);
+        strip_tracking_query(&mut q);
+        assert_eq!(q.len(), 1);
+        assert_eq!(q.get("v").map(String::as_str), Some("1"));
+    }
+
+    #[test]
+    fn strip_tracking_query_utm_prefix() {
+        let mut q = HashMap::from([("utm_campaign".into(), "email".into())]);
+        strip_tracking_query(&mut q);
+        assert!(q.is_empty());
+    }
+}
diff --git a/server/src/url_rules/registry_tests.rs b/server/src/url_rules/registry_tests.rs
new file mode 100644
index 0000000000000000000000000000000000000000..7b76b550f808f590e011469fdae02adf603b43d2
--- /dev/null
+++ b/server/src/url_rules/registry_tests.rs
@@ -0,0 +1,195 @@
+//! End-to-end tests for the public registry API (`canonicalize_raw`, breadcrumbs, parent).
+
+use super::registry::{
+    canonicalize_raw, looks_like_url, navigable_breadcrumbs, parent_url, resolve_id,
+};
+
+fn canon(raw: &str) -> String {
+    canonicalize_raw(raw).unwrap().canonical
+}
+
+#[test]
+fn looks_like_url_positive_cases() {
+    for raw in [
+        "https://reddit.com/r/rust",
+        "r/rust",
+        "/r/aww",
+        "reddit.com/r/x",
+        "www.example.com/path",
+        "youtu.be/abc",
+    ] {
+        assert!(looks_like_url(raw), "{raw}");
+    }
+}
+
+#[test]
+fn looks_like_url_negative_cases() {
+    for raw in ["alpha", "beta", "", "hello world", "no-dots"] {
+        assert!(!looks_like_url(raw), "{raw}");
+    }
+}
+
+#[test]
+fn resolve_id_matches_canonicalize_raw() {
+    let raw = "https://youtu.be/xyz";
+    assert_eq!(
+        resolve_id(raw).as_deref(),
+        Some(canon(raw).as_str())
+    );
+}
+
+#[test]
+fn canonicalize_empty_returns_none() {
+    assert!(canonicalize_raw("").is_none());
+}
+
+#[test]
+fn alias_when_slug_stripped() {
+    let r = canonicalize_raw(
+        "https://reddit.com/r/rust/comments/aaa/very_long_title_slug",
+    )
+    .unwrap();
+    assert_eq!(r.canonical, "https://reddit.com/r/rust/comments/aaa");
+    assert!(r.alias_of.is_some());
+}
+
+#[test]
+fn alias_none_when_already_canonical() {
+    let raw = "https://reddit.com/r/rust";
+    let r = canonicalize_raw(raw).unwrap();
+    assert_eq!(r.canonical, raw);
+    assert!(r.alias_of.is_none());
+}
+
+#[test]
+fn parent_url_subreddit_under_r_hub() {
+    assert_eq!(
+        parent_url("https://reddit.com/r/movies").as_deref(),
+        Some("https://reddit.com/r")
+    );
+}
+
+#[test]
+fn parent_url_domain_has_none() {
+    assert_eq!(parent_url("https://reddit.com").as_deref(), None);
+}
+
+#[test]
+fn parent_url_generic_site() {
+    assert_eq!(
+        parent_url("https://example.com/a/b").as_deref(),
+        Some("https://example.com/a")
+    );
+}
+
+#[test]
+fn breadcrumbs_from_canonical_string_roundtrip() {
+    let id = "https://reddit.com/r/golang/comments/abc123";
+    let crumbs = navigable_breadcrumbs(id);
+    assert_eq!(crumbs.last().map(String::as_str), Some(id));
+}
+
+// --- Table: Reddit raw URLs → canonical ---
+
+#[test]
+fn reddit_canonical_matrix() {
+    let cases: &[(&str, &str)] = &[
+        ("r/rust", "https://reddit.com/r/rust"),
+        ("/r/aww", "https://reddit.com/r/aww"),
+        ("https://reddit.com/r/rust", "https://reddit.com/r/rust"),
+        (
+            "https://www.reddit.com/r/programming/new",
+            "https://reddit.com/r/programming",
+        ),
+        (
+            "https://old.reddit.com/r/test/comments/xyz/slug/",
+            "https://reddit.com/r/test/comments/xyz",
+        ),
+        (
+            "reddit.com/r/Movies/comments/abc/Title_Case_Slug",
+            "https://reddit.com/r/movies/comments/abc",
+        ),
+    ];
+    for (raw, want) in cases {
+        assert_eq!(canon(raw), *want, "raw={raw}");
+    }
+}
+
+// --- Table: YouTube raw URLs → canonical ---
+
+#[test]
+fn youtube_canonical_matrix() {
+    let cases: &[(&str, &str)] = &[
+        (
+            "https://youtube.com/watch?v=abc",
+            "https://youtube.com/watch?v=abc",
+        ),
+        (
+            "https://www.youtube.com/watch?v=abc&t=1&feature=share",
+            "https://youtube.com/watch?v=abc",
+        ),
+        ("https://youtu.be/abc", "https://youtube.com/watch?v=abc"),
+        (
+            "https://youtube.com/shorts/abc",
+            "https://youtube.com/watch?v=abc",
+        ),
+    ];
+    for (raw, want) in cases {
+        assert_eq!(canon(raw), *want, "raw={raw}");
+    }
+}
+
+// --- Table: generic sites ---
+
+#[test]
+fn generic_canonical_matrix() {
+    let cases: &[(&str, &str)] = &[
+        (
+            "https://news.ycombinator.com/item?id=38472",
+            "https://news.ycombinator.com/item?id=38472",
+        ),
+        (
+            "https://www.github.com/rust-lang/rust/issues/1?utm_source=x",
+            "https://github.com/rust-lang/rust/issues/1",
+        ),
+        ("https://example.com", "https://example.com"),
+    ];
+    for (raw, want) in cases {
+        assert_eq!(canon(raw), *want, "raw={raw}");
+    }
+}
+
+// --- Phantom /comments/ regression (sorter2-specific) ---
+
+#[test]
+fn phantom_comments_not_in_breadcrumbs_for_post() {
+    let crumbs = navigable_breadcrumbs("https://reddit.com/r/rust/comments/aaa");
+    assert!(!crumbs.iter().any(|c| c.ends_with("/comments")));
+}
+
+#[test]
+fn phantom_comments_not_sibling_of_subreddit_in_breadcrumb_chain() {
+    let crumbs = navigable_breadcrumbs("https://reddit.com/r/rust/comments/aaa");
+    let subs: Vec<_> = crumbs
+        .iter()
+        .filter(|c| c.contains("/r/rust") && !c.contains("/comments/"))
+        .collect();
+    assert_eq!(subs, vec!["https://reddit.com/r/rust"]);
+}
+
+// --- Distinct items must stay distinct ---
+
+#[test]
+fn different_posts_different_canonical() {
+    let a = canon("https://reddit.com/r/rust/comments/aaa");
+    let b = canon("https://reddit.com/r/rust/comments/bbb");
+    assert_ne!(a, b);
+}
+
+#[test]
+fn different_subreddits_different_canonical() {
+    assert_ne!(
+        canon("https://reddit.com/r/rust"),
+        canon("https://reddit.com/r/golang")
+    );
+}


Side B — contributor: tommy-mor
Side B — commit message:
[239c074b] url schema stuff

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