diff --git a/crates/notgraph/src/analysis.rs b/crates/notgraph/src/analysis.rs
index 1e69a85..17a8451 100644
--- a/crates/notgraph/src/analysis.rs
+++ b/crates/notgraph/src/analysis.rs
@@ -22,9 +22,12 @@ pub fn detect_cycles(nodes: &[String], edges: &[(String, String)]) -> Vec<Vec<St
     let mut in_degree: HashMap<&str, usize> = nodes.iter().map(|n| (n.as_str(), 0)).collect();
     let mut adj: HashMap<&str, Vec<&str>> = nodes.iter().map(|n| (n.as_str(), vec![])).collect();
 
+    let node_set: std::collections::HashSet<&str> = nodes.iter().map(|n| n.as_str()).collect();
     for (from, to) in edges {
-        *in_degree.entry(to.as_str()).or_insert(0) += 1;
-        adj.entry(from.as_str()).or_default().push(to.as_str());
+        if node_set.contains(from.as_str()) && node_set.contains(to.as_str()) {
+            *in_degree.entry(to.as_str()).or_insert(0) += 1;
+            adj.entry(from.as_str()).or_default().push(to.as_str());
+        }
     }
 
     let mut queue: VecDeque<&str> = in_degree.iter()
diff --git a/crates/notgraph/src/module_graph.rs b/crates/notgraph/src/module_graph.rs
index 0d2c857..6001b8d 100644
--- a/crates/notgraph/src/module_graph.rs
+++ b/crates/notgraph/src/module_graph.rs
@@ -33,20 +33,6 @@ impl<'ast> Visit<'ast> for ModCollector {
     }
 }
 
-fn path_to_mod(krate: &str, rel: &Path) -> ModPath {
-    let mut parts: Vec<String> = vec![krate.to_string()];
-    for component in rel.components() {
-        let s = component.as_os_str().to_string_lossy();
-        if s == "lib.rs" || s == "main.rs" {
-            break;
-        }
-        let s = s.trim_end_matches(".rs").to_string();
-        if s != "mod" {
-            parts.push(s);
-        }
-    }
-    parts.join("::")
-}
 
 pub fn build(krate: CrateName, src_dir: &Path) -> Result<ModuleGraph> {
     let mut all_nodes: Vec<ModPath> = Vec::new();
@@ -61,7 +47,7 @@ pub fn build(krate: CrateName, src_dir: &Path) -> Result<ModuleGraph> {
         let content = std::fs::read_to_string(path)?;
         let file = syn::parse_file(&content)?;
         let rel = path.strip_prefix(src_dir)?;
-        let mod_path = path_to_mod(&krate, rel);
+        let mod_path = crate::types::path_to_mod(&krate, rel);
 
         let mut collector = ModCollector::new(mod_path);
         collector.visit_file(&file);
diff --git a/crates/notgraph/src/symbols.rs b/crates/notgraph/src/symbols.rs
index 7e6a833..f1b6d80 100644
--- a/crates/notgraph/src/symbols.rs
+++ b/crates/notgraph/src/symbols.rs
@@ -42,22 +42,14 @@ impl<'ast> Visit<'ast> for SymbolCollector {
     fn visit_item_const(&mut self, node: &'ast syn::ItemConst) {
         self.push(SymbolKind::Const, node.ident.to_string(), Self::is_pub(&node.vis));
     }
+    fn visit_item_mod(&mut self, node: &'ast syn::ItemMod) {
+        let child_path = format!("{}::{}", self.mod_path, node.ident);
+        let parent = std::mem::replace(&mut self.mod_path, child_path);
+        syn::visit::visit_item_mod(self, node);
+        self.mod_path = parent;
+    }
 }
 
-fn path_to_mod(krate: &str, rel: &Path) -> ModPath {
-    let mut parts: Vec<String> = vec![krate.to_string()];
-    for component in rel.components() {
-        let s = component.as_os_str().to_string_lossy();
-        if s == "lib.rs" || s == "main.rs" {
-            break;
-        }
-        let s = s.trim_end_matches(".rs").to_string();
-        if s != "mod" {
-            parts.push(s);
-        }
-    }
-    parts.join("::")
-}
 
 pub fn build(krate: CrateName, src_dir: &Path) -> Result<SymbolTable> {
     let mut symbols: Vec<Symbol> = Vec::new();
@@ -70,7 +62,7 @@ pub fn build(krate: CrateName, src_dir: &Path) -> Result<SymbolTable> {
         let content = std::fs::read_to_string(path)?;
         let file = syn::parse_file(&content)?;
         let rel = path.strip_prefix(src_dir)?;
-        let mod_path = path_to_mod(&krate, rel);
+        let mod_path = crate::types::path_to_mod(&krate, rel);
         let mut collector = SymbolCollector::new(mod_path);
         collector.visit_file(&file);
         symbols.extend(collector.symbols);
diff --git a/crates/notgraph/src/types.rs b/crates/notgraph/src/types.rs
index 1aec755..e8e4cda 100644
--- a/crates/notgraph/src/types.rs
+++ b/crates/notgraph/src/types.rs
@@ -96,3 +96,19 @@ pub struct GraphStats {
     pub hotspots:      Vec<Hotspot>,
     pub cycles:        Vec<Vec<ModPath>>,
 }
+
+/// Convert a source file path (relative to src/) to a Rust module path like `crate::foo::bar`.
+pub fn path_to_mod(krate: &str, rel: &std::path::Path) -> ModPath {
+    let mut parts: Vec<String> = vec![krate.to_string()];
+    for component in rel.components() {
+        let s = component.as_os_str().to_string_lossy();
+        if s == "lib.rs" || s == "main.rs" {
+            break;
+        }
+        let s = s.trim_end_matches(".rs").to_string();
+        if s != "mod" {
+            parts.push(s);
+        }
+    }
+    parts.join("::")
+}