diff --git a/src-rust/crates/core/src/coven_daemon.rs b/src-rust/crates/core/src/coven_daemon.rs
index 6eef4f6..494c881 100644
--- a/src-rust/crates/core/src/coven_daemon.rs
+++ b/src-rust/crates/core/src/coven_daemon.rs
@@ -106,6 +106,8 @@ pub struct RegisterExternalSession {
     pub harness: String,
     pub title: String,
     pub transcript_path: Option<String>,
+    #[serde(skip_serializing_if = "Vec::is_empty")]
+    pub labels: Vec<String>,
 }
 
 // ---------------------------------------------------------------------------
@@ -1140,26 +1142,36 @@ mod tests {
             harness: "coven-code".to_string(),
             title: "My session".to_string(),
             transcript_path: Some("/home/user/.coven-code/sessions/sess-1.jsonl".to_string()),
+            labels: vec!["source:psyche-build".to_string()],
         };
-        let json = serde_json::to_string(&req).unwrap();
-        assert!(
-            json.contains("\"projectRoot\""),
-            "expected camelCase projectRoot, got: {json}"
-        );
-        assert!(
-            json.contains("\"transcriptPath\""),
-            "expected camelCase transcriptPath, got: {json}"
-        );
-        assert!(
-            !json.contains("\"project_root\""),
-            "snake_case leaked: {json}"
-        );
-        assert!(
-            !json.contains("\"transcript_path\""),
-            "snake_case leaked: {json}"
+        let json = serde_json::to_value(&req).unwrap();
+        assert_eq!(
+            json,
+            serde_json::json!({
+                "id": "sess-1",
+                "projectRoot": "/home/user/repo",
+                "harness": "coven-code",
+                "title": "My session",
+                "transcriptPath": "/home/user/.coven-code/sessions/sess-1.jsonl",
+                "labels": ["source:psyche-build"],
+            })
         );
     }
 
+    #[test]
+    fn register_external_session_omits_empty_labels() {
+        let req = RegisterExternalSession {
+            id: "sess-1".to_string(),
+            project_root: "/home/user/repo".to_string(),
+            harness: "coven-code".to_string(),
+            title: "My session".to_string(),
+            transcript_path: None,
+            labels: Vec::new(),
+        };
+        let json = serde_json::to_value(&req).unwrap();
+        assert_eq!(json.get("labels"), None);
+    }
+
     #[test]
     fn complete_session_body_serializes_exit_code() {
         // Verify the exitCode key (camelCase) is what the daemon expects.
diff --git a/src-rust/crates/core/src/coven_ledger.rs b/src-rust/crates/core/src/coven_ledger.rs
index 5958419..8ff033b 100644
--- a/src-rust/crates/core/src/coven_ledger.rs
+++ b/src-rust/crates/core/src/coven_ledger.rs
@@ -3,6 +3,16 @@
 //! Every failure is swallowed to a debug log — a dead or absent daemon must
 //! never affect the TUI.
 
+const COVEN_SESSION_SOURCE: &str = "COVEN_SESSION_SOURCE";
+const PSYCHE_SESSION_SOURCE: &str = "psyche-build";
+
+fn registration_labels(source: Option<&str>) -> Vec<String> {
+    match source {
+        Some(PSYCHE_SESSION_SOURCE) => vec![format!("source:{PSYCHE_SESSION_SOURCE}")],
+        _ => Vec::new(),
+    }
+}
+
 #[cfg(unix)]
 pub fn notify_session_start(id: &str, project_root: &std::path::Path, title: &str) {
     let Some(client) = crate::coven_daemon::DaemonClient::new() else {
@@ -17,6 +27,7 @@ pub fn notify_session_start(id: &str, project_root: &std::path::Path, title: &st
         harness: "coven-code".to_string(),
         title: title.to_string(),
         transcript_path,
+        labels: registration_labels(std::env::var(COVEN_SESSION_SOURCE).ok().as_deref()),
     };
     if let Err(e) = client.register_external_session(&req) {
         tracing::debug!("coven ledger register failed (ignored): {e}");
@@ -38,3 +49,29 @@ pub fn notify_session_start(_id: &str, _project_root: &std::path::Path, _title:
 
 #[cfg(not(unix))]
 pub fn notify_session_complete(_id: &str, _exit_code: Option<i32>) {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn maps_only_the_exact_psyche_source() {
+        assert_eq!(
+            registration_labels(Some(PSYCHE_SESSION_SOURCE)),
+            vec![format!("source:{PSYCHE_SESSION_SOURCE}")]
+        );
+
+        for source in [
+            None,
+            Some(""),
+            Some("Psyche-Build"),
+            Some("foreign"),
+            Some("psyche-build-extra"),
+        ] {
+            assert!(
+                registration_labels(source).is_empty(),
+                "unexpected label for {source:?}"
+            );
+        }
+    }
+}