diff --git a/nix/agent-modules/mcp.nix b/nix/agent-modules/mcp.nix
index 094ec4ec..83ab96b9 100644
--- a/nix/agent-modules/mcp.nix
+++ b/nix/agent-modules/mcp.nix
@@ -408,6 +408,15 @@ in
         # HYPERHIVE_HARNESS_DIR / HYPERHIVE_STATE_DIR: see
         # `hive-bash-daemon`'s own comment above — same global injection,
         # same reasoning.
+        # A subagent's backgrounded bash child is reaped with the rest of
+        # its process tree at turn end, which orphans anything still
+        # running past the CLI's default 2-minute timeout with a silent
+        # truncated/empty log rather than a reported failure. Raising the
+        # default here (not in managed-settings, which the main agent's
+        # session also reads) scopes the longer timeout to subagent turns
+        # only — the operator's ruling was explicit that the main agent's
+        # environment stays as is.
+        BASH_DEFAULT_TIMEOUT_MS = "1800000"; # 30 minutes
       };
       serviceConfig = {
         ExecStart = "${config.services.hyperhive.agent.packages.hive-subagent-daemon}/bin/hive-subagent-daemon --http 127.0.0.1:${toString config.services.hyperhive.agent.mcp.subagentHttpPort}";