diff --git a/crates/hiroz-union/src/core/logger.rs b/crates/hiroz-union/src/core/logger.rs
index 909b4bfcb..ac1df70b7 100644
--- a/crates/hiroz-union/src/core/logger.rs
+++ b/crates/hiroz-union/src/core/logger.rs
@@ -1,14 +1,24 @@
 use tracing_subscriber::{EnvFilter, fmt};
 
+/// Default filter directives when `RUST_LOG` is unset.
+///
+/// `hu` must be listed explicitly: the binary target is named `hu`
+/// (`[[bin]] name = "hu"`), so every `tracing::` call in this crate emits under
+/// the `hu` target. A filter naming only `hiroz` and `zenoh` drops all of them,
+/// which is why the host's schema-discovery and decode warnings were emitted and
+/// then discarded before reaching a terminal.
+pub(crate) fn default_filter(debug: bool) -> &'static str {
+    if debug {
+        "hu=debug,hiroz=debug,zenoh=debug"
+    } else {
+        "hu=info,hiroz=info,zenoh=warn"
+    }
+}
+
 pub fn init_logger(json_mode: bool, debug: bool) {
     // Build filter from RUST_LOG environment variable or default
-    let filter = EnvFilter::try_from_default_env().unwrap_or_else(|_| {
-        if debug {
-            EnvFilter::new("hiroz=debug,zenoh=debug")
-        } else {
-            EnvFilter::new("hiroz=info,zenoh=warn")
-        }
-    });
+    let filter =
+        EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new(default_filter(debug)));
 
     if json_mode {
         // Structured JSON logs to stderr (for real-time visibility)
@@ -30,3 +40,24 @@ pub fn init_logger(json_mode: bool, debug: bool) {
             .init();
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::default_filter;
+    use tracing_subscriber::EnvFilter;
+
+    // The whole of the `hu` target fix is one string literal, and it is exactly
+    // the kind of line a later edit drops without noticing.
+    #[test]
+    fn defaults_name_the_hu_target_and_parse() {
+        for debug in [false, true] {
+            let directives = default_filter(debug);
+            assert!(
+                directives.contains("hu="),
+                "default filter for debug={debug} does not name the `hu` target: {directives}"
+            );
+            EnvFilter::try_new(directives)
+                .unwrap_or_else(|e| panic!("default filter {directives:?} does not parse: {e}"));
+        }
+    }
+}