prefix bash-task invocations with set -o pipefail

hive-bash-mcp/src/runner.rs

@@ -601,6 +601,16 @@ async fn run_task(mut task: TaskFile, socket: &Path) {
 /// mode, which disables bashisms — arrays, `[[ … ]]`, `local`, process
 /// substitution), invoked via `/usr/bin/env bash`.
 ///
+/// The invocation is prefixed with `set -o pipefail` so a pipeline's exit
+/// status reflects its last *failing* stage, not just its last stage — a
+/// piped `cargo build 2>&1 | tail -40 && cargo test ...` chain silently
+/// reports success off `tail`'s exit code otherwise, masking a real build
+/// failure from every downstream `&&`/exit-code check. `-e`/`-u`/`-x` are
+/// deliberately NOT forced on: unlike `pipefail` (a pure exit-status
+/// reporting fix), each of those changes control flow or output volume in
+/// ways plenty of ad-hoc one-liners don't expect — an opt-in a task's own
+/// command string can request, not a safe default for every task.
+///
 /// The task is cancellable via `cancel` (set `force` first): on cancel the
 /// whole process group is signalled — `SIGKILL` if `force`, else `SIGINT` —
 /// so children of the shell die too, not just the shell. The timeout path
@@ -622,7 +632,7 @@ async fn exec_cmd(
     cmd_builder
         .arg("bash")
         .arg("-c")
-        .arg(cmd)
+        .arg(format!("set -o pipefail; {cmd}"))
         .stdout(std::process::Stdio::piped())
         .stderr(std::process::Stdio::piped());
     // SAFETY: `setpgid`/`nice` are async-signal-safe and only touch the