diff --git a/crates/hiroz-union/src/plugin/wasm/host/ros.rs b/crates/hiroz-union/src/plugin/wasm/host/ros.rs
index 04dc425f0..43907409e 100644
--- a/crates/hiroz-union/src/plugin/wasm/host/ros.rs
+++ b/crates/hiroz-union/src/plugin/wasm/host/ros.rs
@@ -389,8 +389,15 @@ impl hu::plugin::ros::Host for PluginState {
                 // bytes onto that endpoint's key — reject instead (same guard as
                 // the discovery branch below). An empty topic has no live type,
                 // so publishing to it still works, like `ros2 topic pub`.
+                // The graph reports a DDS-mangled name
+                // (`std_msgs::msg::dds_::String_`) while `--msg-type` is the ROS
+                // form (`std_msgs/msg/String`). Comparing them raw rejects a
+                // correct publish. This branch only became reachable once a
+                // schema could resolve without a live node, so nothing exercised
+                // it before: the one test that resolves from disk publishes to an
+                // *empty* topic, where there is no live type to compare against.
                 if let Some(live) = self.live_topic_type_info(&topic)
-                    && live.name != type_name
+                    && hiroz::dynamic::ros_type_name_from_dds(&live.name) != type_name
                 {
                     return Err(PluginError::Invalid(format!(
                         "topic {topic} carries {}, not the requested {type_name}",
diff --git a/crates/hiroz/build.rs b/crates/hiroz/build.rs
index 6d0bc02b7..bc2c4b35b 100644
--- a/crates/hiroz/build.rs
+++ b/crates/hiroz/build.rs
@@ -16,6 +16,8 @@ fn main() {
     println!("cargo:rerun-if-changed=src/config.rs");
     println!("cargo:rerun-if-env-changed=HIROZ_CONFIG_OUTPUT_DIR");
 
+    embed_bundled_msgs();
+
     // Generate C FFI header when ffi feature is enabled
     #[cfg(feature = "ffi")]
     {
@@ -118,3 +120,88 @@ fn main() {
         );
     }
 }
+
+/// Embed the bundled `.msg` definitions as source text, so a binary with no
+/// `HIROZ_MSG_PATH` and no live publisher can still resolve a schema.
+///
+/// Emits `$OUT_DIR/embedded_msgs.rs`: a sorted `&[(&str, &str)]` of
+/// `pkg/msg/Name` to the file's contents, via `include_str!` so the bytes are
+/// the ones on disk at build time and cannot drift from them.
+///
+/// The whole jazzy set is ~122 KB of text. Subsetting it would only trade a
+/// fraction of a percent of binary size for "why is my type missing?", so
+/// everything bundled is embedded.
+///
+/// Reads `../hiroz-codegen/assets/{distro}` directly rather than calling
+/// `hiroz_codegen::bundled_assets_dir`, which would make hiroz-codegen a
+/// build-dependency for a directory walk. If the directory is absent the table
+/// is empty and schema resolution behaves exactly as it did before.
+fn embed_bundled_msgs() {
+    use std::fmt::Write as _;
+
+    let manifest = std::path::PathBuf::from(std::env::var("CARGO_MANIFEST_DIR").unwrap());
+    let distro = if std::env::var_os("CARGO_FEATURE_HUMBLE").is_some() {
+        "humble"
+    } else {
+        "jazzy"
+    };
+    let assets = manifest
+        .join("..")
+        .join("hiroz-codegen")
+        .join("assets")
+        .join(distro);
+    println!("cargo:rerun-if-changed={}", assets.display());
+
+    let mut entries: Vec<(String, std::path::PathBuf)> = Vec::new();
+    if let Ok(packages) = std::fs::read_dir(&assets) {
+        for pkg in packages.flatten() {
+            let pkg_path = pkg.path();
+            if !pkg_path.is_dir() {
+                continue;
+            }
+            let Some(pkg_name) = pkg_path.file_name().and_then(|n| n.to_str()) else {
+                continue;
+            };
+            let msg_dir = pkg_path.join("msg");
+            let Ok(msgs) = std::fs::read_dir(&msg_dir) else {
+                continue;
+            };
+            for m in msgs.flatten() {
+                let path = m.path();
+                if path.extension().and_then(|e| e.to_str()) != Some("msg") {
+                    continue;
+                }
+                let Some(stem) = path.file_stem().and_then(|n| n.to_str()) else {
+                    continue;
+                };
+                entries.push((format!("{pkg_name}/msg/{stem}"), path));
+            }
+        }
+    } else {
+        println!(
+            "cargo:warning=bundled assets not found at {}; embedded schema fallback will be empty",
+            assets.display()
+        );
+    }
+
+    // Sorted, so the lookup can binary-search.
+    entries.sort_by(|a, b| a.0.cmp(&b.0));
+
+    let mut out = String::from(
+        "// @generated by build.rs - do not edit\npub static EMBEDDED_MSGS: &[(&str, &str)] = &[\n",
+    );
+    for (type_name, path) in &entries {
+        writeln!(
+            out,
+            "    ({type_name:?}, include_str!({:?})),",
+            path.display().to_string()
+        )
+        .unwrap();
+    }
+    out.push_str("];\n");
+
+    let dest = std::path::PathBuf::from(std::env::var("OUT_DIR").unwrap()).join("embedded_msgs.rs");
+    if let Err(e) = std::fs::write(&dest, out) {
+        println!("cargo:warning=failed to write {}: {e}", dest.display());
+    }
+}
diff --git a/crates/hiroz/src/dynamic/registry.rs b/crates/hiroz/src/dynamic/registry.rs
index 050563367..0489aa0dc 100644
--- a/crates/hiroz/src/dynamic/registry.rs
+++ b/crates/hiroz/src/dynamic/registry.rs
@@ -220,15 +220,30 @@ fn load_schema_inner(
     // File not on disk is a legitimate "try the next source" (live discovery),
     // so return None quietly. Errors *after* a file is found are logged below,
     // since a broken `.msg` masquerading as "not found" would be misleading.
-    let path = find_msg_file(&package, &name)?;
+    // Disk first, so a user pointing HIROZ_MSG_PATH at their own definitions
+    // always wins over what this binary happens to have been built with.
+    let source = match find_msg_file(&package, &name) {
+        Some(path) => MsgSource::File(path),
+        None => MsgSource::Embedded(embedded_msg_source(&package, &name)?),
+    };
     if !in_progress.borrow_mut().insert(type_name.to_string()) {
         tracing::warn!("cyclic .msg definition for {type_name}; skipping schema load");
         return None;
     }
-    let mut parsed = match hiroz_codegen::parser::msg::parse_msg_file(&path, &package) {
+    let parse_result = match &source {
+        MsgSource::File(path) => hiroz_codegen::parser::msg::parse_msg_file(path, &package),
+        // The path argument is only used for diagnostics; the bytes come from
+        // the embedded table.
+        MsgSource::Embedded(text) => hiroz_codegen::parser::msg::parse_msg_string(
+            text,
+            &package,
+            std::path::Path::new(&format!("<embedded>/{package}/msg/{name}.msg")),
+        ),
+    };
+    let mut parsed = match parse_result {
         Ok(parsed) => parsed,
         Err(e) => {
-            tracing::warn!("failed to parse .msg file {}: {e}", path.display());
+            tracing::warn!("failed to parse .msg for {type_name} from {source}: {e}");
             in_progress.borrow_mut().remove(type_name);
             return None;
         }
@@ -261,6 +276,49 @@ fn load_schema_inner(
     Some(register_schema(schema))
 }
 
+/// Where a `.msg` definition came from, for diagnostics.
+#[cfg(feature = "dynamic-schema-loader")]
+enum MsgSource {
+    File(std::path::PathBuf),
+    Embedded(&'static str),
+}
+
+#[cfg(feature = "dynamic-schema-loader")]
+impl std::fmt::Display for MsgSource {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            MsgSource::File(p) => write!(f, "{}", p.display()),
+            MsgSource::Embedded(_) => write!(f, "the definitions built into this binary"),
+        }
+    }
+}
+
+/// The bundled `.msg` definitions, embedded as source text at build time.
+///
+/// Sorted by `pkg/msg/Name`, so the lookup below can binary-search.
+#[cfg(feature = "dynamic-schema-loader")]
+mod embedded {
+    include!(concat!(env!("OUT_DIR"), "/embedded_msgs.rs"));
+}
+
+/// Look up `<pkg>/msg/<Name>` among the definitions built into this binary.
+///
+/// This is what lets a downloaded `hu` decode a topic with no `HIROZ_MSG_PATH`
+/// set and no reachable type-description service — the case where discovery
+/// yields a type name and the disk has nothing to resolve it with.
+///
+/// Consulted **after** `HIROZ_MSG_PATH`, never before: a user who points that
+/// variable at their own definitions means it, and a stale embedded copy must
+/// not silently win over the messages their publisher was actually built from.
+#[cfg(feature = "dynamic-schema-loader")]
+fn embedded_msg_source(package: &str, name: &str) -> Option<&'static str> {
+    let key = format!("{package}/msg/{name}");
+    embedded::EMBEDDED_MSGS
+        .binary_search_by(|(k, _)| (*k).cmp(key.as_str()))
+        .ok()
+        .map(|i| embedded::EMBEDDED_MSGS[i].1)
+}
+
 /// Split `pkg/msg/Name` (or the shorthand `pkg/Name`) into `(package, name)`.
 #[cfg(feature = "dynamic-schema-loader")]
 fn split_msg_type(type_name: &str) -> Option<(String, String)> {
@@ -304,3 +362,81 @@ fn find_msg_file(package: &str, name: &str) -> Option<std::path::PathBuf> {
     }
     None
 }
+
+#[cfg(all(test, feature = "dynamic-schema-loader"))]
+mod embedded_tests {
+    use super::*;
+
+    /// The table is what makes a downloaded `hu` able to decode anything, so an
+    /// empty one is a silent regression: every lookup would simply miss and the
+    /// behaviour would fall back to today's "no .msg found".
+    #[test]
+    fn the_embedded_table_is_not_empty_and_is_sorted() {
+        assert!(
+            !embedded::EMBEDDED_MSGS.is_empty(),
+            "no bundled .msg definitions were embedded; \
+             the build script found no assets directory"
+        );
+        assert!(
+            embedded::EMBEDDED_MSGS.windows(2).all(|w| w[0].0 < w[1].0),
+            "the embedded table must be sorted and duplicate-free: binary_search relies on it"
+        );
+    }
+
+    /// std_msgs/msg/String is the type the documented quick start echoes, and
+    /// the one the G2 measurement showed failing on a default install.
+    #[test]
+    fn a_common_type_resolves_from_the_embedded_definitions() {
+        let src = embedded_msg_source("std_msgs", "String")
+            .expect("std_msgs/msg/String must be embedded");
+        assert!(
+            src.contains("string data"),
+            "embedded source does not look like the real definition: {src:?}"
+        );
+    }
+
+    #[test]
+    fn an_unknown_type_is_a_miss_not_a_panic() {
+        assert!(embedded_msg_source("no_such_pkg", "Nope").is_none());
+    }
+
+    /// Disk must win over the embedded copy. A user who sets HIROZ_MSG_PATH
+    /// means it, and their publisher may have been built from definitions that
+    /// differ from the ones this binary was compiled with.
+    #[test]
+    #[serial_test::serial]
+    fn a_definition_on_disk_wins_over_the_embedded_one() {
+        let dir = std::env::temp_dir().join(format!("hiroz-embed-{}", std::process::id()));
+        let msg_dir = dir.join("std_msgs").join("msg");
+        std::fs::create_dir_all(&msg_dir).unwrap();
+        // Deliberately NOT the real definition, so resolving it proves the disk
+        // copy was used rather than the embedded one.
+        std::fs::write(
+            msg_dir.join("String.msg"),
+            "string data\nint32 sentinel_field\n",
+        )
+        .unwrap();
+
+        let found = find_msg_file("std_msgs", "String");
+        let restore = std::env::var("HIROZ_MSG_PATH").ok();
+        assert!(
+            found.is_none() || restore.is_some(),
+            "test environment already has HIROZ_MSG_PATH pointing somewhere"
+        );
+
+        unsafe { std::env::set_var("HIROZ_MSG_PATH", &dir) };
+        let path = find_msg_file("std_msgs", "String")
+            .expect("the on-disk definition must be found first");
+        let text = std::fs::read_to_string(&path).unwrap();
+        assert!(
+            text.contains("sentinel_field"),
+            "HIROZ_MSG_PATH did not take precedence over the embedded table"
+        );
+
+        match restore {
+            Some(v) => unsafe { std::env::set_var("HIROZ_MSG_PATH", v) },
+            None => unsafe { std::env::remove_var("HIROZ_MSG_PATH") },
+        }
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+}