diff --git a/packages/server/src/server/terminal-mcp/tmux.ts b/packages/server/src/server/terminal-mcp/tmux.ts
index f2d26ed64..532d6d3b7 100644
--- a/packages/server/src/server/terminal-mcp/tmux.ts
+++ b/packages/server/src/server/terminal-mcp/tmux.ts
@@ -591,7 +591,8 @@ export async function executeCommand({
         pane.id,
         "#{pane_dead_status}",
       ]);
-      exitCode = parseInt(exitCodeStr, 10);
+      const parsed = parseInt(exitCodeStr, 10);
+      exitCode = Number.isFinite(parsed) ? parsed : null;
       break;
     }