diff --git a/crates/tui/src/command_safety.rs b/crates/tui/src/command_safety.rs
index 5bdebafd..93a0a643 100644
--- a/crates/tui/src/command_safety.rs
+++ b/crates/tui/src/command_safety.rs
@@ -582,6 +582,14 @@ pub fn analyze_command(command: &str) -> SafetyAnalysis {
         );
     }
 
+    if command.contains('\0') {
+        return SafetyAnalysis::dangerous(
+            command,
+            vec!["Command contains a null byte".to_string()],
+            vec!["Strip embedded null bytes before retrying".to_string()],
+        );
+    }
+
     if command.contains("&&") || command.contains("||") || command.contains(';') {
         // Chains of known-safe commands (cargo/git/zig/npm/etc.) are
         // routine for build+test workflows. Instead of hard-blocking,
@@ -947,6 +955,39 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_null_byte_is_blocked() {
+        assert_eq!(
+            analyze_command("ls\0 -la").level,
+            SafetyLevel::Dangerous,
+            "embedded NUL byte must be rejected as dangerous"
+        );
+        assert_eq!(
+            analyze_command("echo hello\0world").level,
+            SafetyLevel::Dangerous
+        );
+    }
+
+    #[test]
+    fn test_eval_substring_is_not_misclassified() {
+        // Words like `evaluate` / `evaluation` / `cargo run -- eval`
+        // contain the substring "eval" but are not eval invocations.
+        // Guard against the naive `command.contains("eval")` regression
+        // — these should stay safe / workspace-safe, never Dangerous.
+        let evaluate_safe = analyze_command("cargo run --bin deepseek -- eval").level;
+        assert_ne!(
+            evaluate_safe,
+            SafetyLevel::Dangerous,
+            "running the eval harness should not be classified as dangerous"
+        );
+        let evaluator = analyze_command("python evaluator.py --suite default").level;
+        assert_ne!(
+            evaluator,
+            SafetyLevel::Dangerous,
+            "running an evaluator script should not be classified as dangerous"
+        );
+    }
+
     #[test]
     fn test_privileged_commands() {
         assert_eq!(