diff --git a/src/ClawdDotNet.Core/Sandbox/BwrapSandbox.cs b/src/ClawdDotNet.Core/Sandbox/BwrapSandbox.cs
index 3f5898f..b695344 100644
--- a/src/ClawdDotNet.Core/Sandbox/BwrapSandbox.cs
+++ b/src/ClawdDotNet.Core/Sandbox/BwrapSandbox.cs
@@ -186,8 +186,9 @@ public sealed class BwrapSandbox : ISandboxRunner
 
         args.AddRange(["--seccomp", "3", "--"]);
 
-        // Inner: the process limit, set inside the sandbox's own user namespace.
-        args.AddRange([Shell, "-c", """ulimit -u "$1" || exit 126; shift; exec "$@" """, "sh",
+        // Inner: the process limit, set inside the sandbox's own user namespace. bash calls it
+        // -u, dash (Debian's and Ubuntu's sh) -p; if neither takes, nothing runs.
+        args.AddRange([Shell, "-c", """ulimit -u "$1" 2>/dev/null || ulimit -p "$1" || exit 126; shift; exec "$@" """, "sh",
             limits.MaxProcesses.ToString(CultureInfo.InvariantCulture), request.Executable]);
         args.AddRange(request.Arguments);
         return args;