diff --git a/main.swift b/main.swift
index 2da6eb1..37e29aa 100644
--- a/main.swift
+++ b/main.swift
@@ -3,6 +3,15 @@ import ApplicationServices
 
 // MARK: - Model
 
+/// Claude Code names a project dir after its cwd with every non-alphanumeric
+/// character replaced by "-", so /Users/me/src/github.com/a_b becomes
+/// -Users-me-src-github-com-a-b. Replacing only "/" silently fails to match
+/// any path containing a dot or underscore.
+func encodedProjectDir(_ path: String) -> String {
+    // ASCII-only on purpose: a non-ASCII letter is not [a-zA-Z0-9] either.
+    String(path.map { $0.isASCII && ($0.isLetter || $0.isNumber) ? $0 : "-" })
+}
+
 enum AgentKind: String { case claude = "Claude Code", codex = "Codex" }
 
 struct AgentSession {
@@ -143,7 +152,7 @@ final class ProcessDiscovery {
         // a claude process can hold several project transcripts open; prefer
         // the one whose encoded project dir matches the process cwd
         if all.count > 1, let cwd {
-            let encoded = cwd.replacingOccurrences(of: "/", with: "-")
+            let encoded = encodedProjectDir(cwd)
             if let preferred = all.first(where: { $0.contains(encoded) }) { return preferred }
         }
         return all.first
@@ -1094,7 +1103,7 @@ final class AppDelegate: NSObject, NSApplicationDelegate {
                 if let path = snap.transcriptPath {
                     seen.insert(path)
                 } else if snap.kind == .claude, let cwd = snap.cwd {
-                    let encoded = cwd.replacingOccurrences(of: "/", with: "-")
+                    let encoded = encodedProjectDir(cwd)
                     let i = cwdIndex[encoded, default: 0]
                     cwdIndex[encoded] = i + 1
                     seen.insert("cwd#\(encoded)#\(i)")
@@ -1167,7 +1176,7 @@ if CommandLine.arguments.contains("--scan") {
     var cwdCounts: [String: Int] = [:]
     for s in snaps {
         if let p = s.transcriptPath { live.insert(p) }
-        else if s.kind == .claude, let c = s.cwd { cwdCounts[c.replacingOccurrences(of: "/", with: "-"), default: 0] += 1 }
+        else if s.kind == .claude, let c = s.cwd { cwdCounts[encodedProjectDir(c), default: 0] += 1 }
     }
     print("== sessions ==")
     for s in SessionScanner().scan(live: live, claudeCwdCounts: cwdCounts) {