diff --git a/hive-bash-mcp/src/mcp.rs b/hive-bash-mcp/src/mcp.rs
index fdd75f44..774a0d10 100644
--- a/hive-bash-mcp/src/mcp.rs
+++ b/hive-bash-mcp/src/mcp.rs
@@ -256,7 +256,8 @@ impl BashMcp {
         let (killed, was_running) = runner::kill_task(&args.id, args.force);
         if !killed {
             return format!(
-                "no running or pending task with id `{}` (already finished or unknown)",
+                "no running or pending task with id `{}` could be killed (already finished, unknown, \
+                 or its pending file could not be updated — see the daemon log)",
                 args.id
             );
         }
diff --git a/hive-bash-mcp/src/runner.rs b/hive-bash-mcp/src/runner.rs
index 02f52a2b..232233c5 100644
--- a/hive-bash-mcp/src/runner.rs
+++ b/hive-bash-mcp/src/runner.rs
@@ -416,7 +416,10 @@ pub fn kill_task(id: &str, force: bool) -> (bool, bool) {
     {
         task.status = TaskStatus::Killed;
         task.completed_at = Some(chrono::Utc::now());
-        let _ = write_task(&task);
+        if let Err(e) = write_task(&task) {
+            tracing::warn!(id, error = ?e, "kill: could not mark pending task killed");
+            return (false, false);
+        }
         // A Pending task never reached Running, so it has no keyed "active"
         // todo to clear and (like the old code) fires no completion signal —
         // the caller that killed it already knows.
@@ -1174,4 +1177,35 @@ mod tests {
             .join("never-created-subdir");
         assert_eq!(sweep_old_tasks(&missing, SystemTime::now()), 0);
     }
+
+    #[test]
+    fn kill_pending_reports_failure_when_the_write_fails() {
+        use super::{kill_task, read_task, write_task};
+        use crate::protocol::{TaskFile, TaskStatus};
+        with_harness_dir(|| {
+            let harness = tempfile::tempdir().unwrap();
+            // SAFETY: serialised by the lock in `with_harness_dir`, which
+            // restores the previous value when the closure returns.
+            unsafe { std::env::set_var("HYPERHIVE_HARNESS_DIR", harness.path()) };
+            std::fs::create_dir_all(crate::paths::tasks_dir()).unwrap();
+            let task = TaskFile {
+                id: "t1".to_owned(),
+                cmd: "echo hi".to_owned(),
+                timeout_secs: None,
+                status: TaskStatus::Pending,
+                created_at: chrono::Utc::now(),
+                started_at: None,
+                completed_at: None,
+                exit_code: None,
+                stdout_tail: None,
+                stderr_tail: None,
+            };
+            write_task(&task).unwrap();
+            // A directory at the temp path makes `write_task` fail even as root.
+            std::fs::create_dir(crate::paths::task_json("t1").with_extension("json.tmp")).unwrap();
+
+            assert_eq!(kill_task("t1", false), (false, false));
+            assert_eq!(read_task("t1").unwrap().status, TaskStatus::Pending);
+        });
+    }
 }