feat(#2006): add services.hyperhive.manageRootAgent to opt out of root-agent auto-management

hive-c0re/src/auto_update.rs

@@ -164,12 +164,33 @@ pub async fn rebuild_agent(
     result
 }
 
+/// Whether hive-c0re auto-manages the root/manager agent — creating it on
+/// startup and restarting it when present-but-stopped. Controlled by the
+/// host option `services.hyperhive.manageRootAgent`, threaded in via the
+/// `HYPERHIVE_MANAGE_ROOT_AGENT` env var. Defaults to enabled when the
+/// var is unset (back-compat: the root agent was always managed before
+/// this opt-out existed); only an explicit `false` / `0` / `no` disables.
+fn manage_root_agent() -> bool {
+    match std::env::var("HYPERHIVE_MANAGE_ROOT_AGENT") {
+        Ok(v) => !matches!(v.trim().to_ascii_lowercase().as_str(), "false" | "0" | "no"),
+        Err(_) => true,
+    }
+}
+
 /// Auto-create the manager container on startup if it isn't already there.
 /// hive-c0re manages the manager end-to-end: operators no longer declare
 /// `containers.h-ruth` in their host NixOS config. Bypasses the approval
-/// queue — the root/manager is auto-managed by default (an operator opt-out
-/// is a separate host setting). Idempotent.
+/// queue — the root/manager is auto-managed by default. Operators who
+/// don't want a root agent at all set `services.hyperhive.manageRootAgent
+/// = false`, which short-circuits this whole function. Idempotent.
 pub async fn ensure_root_agent(coord: &Arc<Coordinator>) -> Result<()> {
+    if !manage_root_agent() {
+        tracing::info!(
+            "root-agent auto-management disabled (services.hyperhive.manageRootAgent = false) - \
+             skipping root agent create/start"
+        );
+        return Ok(());
+    }
     let existing = lifecycle::list().await.unwrap_or_default();
     let current_rev = current_flake_rev(&coord.hyperhive_flake);
     if existing
@@ -201,9 +222,10 @@ pub async fn ensure_root_agent(coord: &Arc<Coordinator>) -> Result<()> {
         // install) is brought back up here: the startup sweep's rebuild only
         // restarts a container that was already running, so without this it
         // stays down until a manual `nixos-container start`. The sub-agent
-        // `was_running` guard is intentionally left untouched. (An operator
-        // opt-out of this whole auto-management is tracked as a separate
-        // host setting.)
+        // `was_running` guard is intentionally left untouched. (Operators
+        // opt out of this whole auto-management with
+        // `services.hyperhive.manageRootAgent = false`, gated at the top of
+        // this function.)
         if !lifecycle::is_running(MANAGER_NAME).await {
             tracing::info!("manager container present but not running — starting");
             if let Err(e) = lifecycle::start(MANAGER_NAME).await {

nix/modules/hive-c0re.nix

@@ -187,6 +187,25 @@ in
     '';
   };
 
+  # Whether hive-c0re auto-manages the root/manager agent on startup
+  # (create it if missing, restart it if present-but-stopped). Some hives
+  # don't want a root agent auto-managed at all — see issue tracker
+  # "scope concept: special agents".
+  options.services.hyperhive.manageRootAgent = lib.mkOption {
+    type = lib.types.bool;
+    default = true;
+    example = false;
+    description = ''
+      Whether hive-c0re auto-manages the root (manager) agent on
+      startup: creating its container when missing and restarting it
+      when it's present but stopped. Defaults to `true` (the historical
+      behaviour — the root agent was treated as required infrastructure).
+      Set to `false` on hives that don't want a root agent at all;
+      hive-c0re then skips the root-agent create/start sweep entirely.
+      Exposed to hive-c0re as `HYPERHIVE_MANAGE_ROOT_AGENT`.
+    '';
+  };
+
   # Hive-wide OTEL stats export. Set ONCE here at host level; the
   # meta-flake renderer (`hive-c0re/src/meta.rs::otel_config`) reads the
   # HYPERHIVE_OTEL_* env exported below off hive-c0re's unit and injects
@@ -873,6 +892,10 @@ in
         # prompts). `hive_sh4re::assets::*` reads paths underneath.
         # `forge.rs` reads the avatar PNGs from here on startup.
         HIVE_ASSETS_DIR = "${cfg.assets}/share/hyperhive";
+        # Whether hive-c0re auto-manages the root/manager agent on
+        # startup (`auto_update::ensure_root_agent`). Default true =
+        # historical behaviour; false makes the root-agent sweep a no-op.
+        HYPERHIVE_MANAGE_ROOT_AGENT = lib.boolToString config.services.hyperhive.manageRootAgent;
       }
       // lib.optionalAttrs (config.services.hyperhive.domain != null) {
         # Identity env vars threaded into c0re's own service env and