diff --git a/src/core/builder/common.rs b/src/core/builder/common.rs
index 527cc9c..7527748 100644
--- a/src/core/builder/common.rs
+++ b/src/core/builder/common.rs
@@ -37,9 +37,6 @@ pub fn collect_sources(
         collect_sources_rec(root, extensions, &mut sources, exclude_dirs, include_paths)?;
     }
     sources.sort();
-    if sources.is_empty() {
-        return Err(format!("No source files found in {}", format_roots(roots)));
-    }
     Ok(sources)
 }
 
@@ -89,17 +86,6 @@ fn collect_sources_rec(
     Ok(())
 }
 
-fn format_roots(roots: &[PathBuf]) -> String {
-    if roots.is_empty() {
-        return "<none>".to_string();
-    }
-    let mut out = Vec::new();
-    for root in roots {
-        out.push(root.to_string_lossy().to_string());
-    }
-    out.join(", ")
-}
-
 pub fn is_excluded(path: &Path, exclude_dirs: &[PathBuf], include_paths: &[String]) -> bool {
     if matches_patterns(path, include_paths, true) {
         return false;
@@ -624,7 +610,8 @@ mod tests {
         let result = collect_sources(&roots, &["c"], &[], &include);
         std::env::set_current_dir(prev).unwrap();
 
-        assert!(result.is_err(), "empty src should return error");
+        let sources = result.expect("empty src should return Ok");
+        assert!(sources.is_empty(), "empty src should return empty vec");
     }
 
     #[test]
diff --git a/src/core/config.rs b/src/core/config.rs
index 4d76099..adcff55 100644
--- a/src/core/config.rs
+++ b/src/core/config.rs
@@ -27,7 +27,15 @@ const DEFAULT_LANGUAGE: &str = "c";
 const DEFAULT_STANDARD: &str = "c11";
 const DEFAULT_COMPILER: &str = "clang";
 const DEFAULT_KIND: &str = "bin";
-const VALID_KINDS: &[&str] = &["bin", "staticlib", "sharedlib", "efi", "elf"];
+const VALID_KINDS: &[&str] = &[
+    "bin",
+    "staticlib",
+    "sharedlib",
+    "efi",
+    "elf",
+    "none",
+    "custom",
+];
 
 #[derive(Debug)]
 pub enum ConfigError {
@@ -101,7 +109,8 @@ pub struct PackageConfig {
 #[derive(Debug, Clone, Deserialize)]
 pub struct BuildConfig {
     pub language: LanguageConfig,
-    pub standard: String,
+    #[serde(default)]
+    pub standard: Option<String>,
     #[serde(default)]
     pub cxx_standard: Option<String>,
     pub compiler: String,
@@ -353,7 +362,14 @@ impl Config {
         }
 
         validate_language_config(&build.language, "build.language")?;
-        if build.standard.trim().is_empty() {
+        let lang_is_asm = match &build.language {
+            LanguageConfig::One(s) => s.trim().eq_ignore_ascii_case("asm"),
+            LanguageConfig::Many(v) => v.len() == 1 && v[0].trim().eq_ignore_ascii_case("asm"),
+        };
+        if let Some(ref std) = build.standard
+            && std.trim().is_empty()
+            && !lang_is_asm
+        {
             return Err(ConfigError::Invalid("build.standard is empty".into()));
         }
         if build.compiler.trim().is_empty() {
@@ -754,7 +770,9 @@ fn format_toml(value: &Value) -> Result<String, ConfigError> {
     } else {
         out.push_str(&format!("language = \"{language}\"\n"));
     }
-    out.push_str(&format!("standard = \"{standard}\"\n"));
+    if !standard.is_empty() {
+        out.push_str(&format!("standard = \"{standard}\"\n"));
+    }
     out.push_str(&format!("compiler = \"{compiler}\"\n"));
     let kind = build
         .get("kind")