feat(#792): agent restart tool — topology-checked restart of direct children

hive-ag3nt/prompts/system.md

@@ -42,6 +42,7 @@ Tools (hyperhive surface):
 - `mcp__hyperhive__get_agent_meta(name?)` — fetch identity + status metadata for an agent: canonical `name`, `role` (`agent` / `manager`), current `hyperhive_rev`, plus self-reported `status` text (set via `set_status`) and how long ago it was set. Also returns the hive + swarm display names (`hive_name`, `swarm_name`) when the operator has configured `services.hyperhive.{hiveName, swarmName}`; both lines omitted when unset. Pass `name` to query a peer (e.g. check whether iris is idle before pinging them). Omit `name` to get your own trustworthy identity stamp — useful for state files, commit messages, cross-agent attribution that won't drift across renames or session-continue boundaries where the system-prompt label could be stale.
 <!-- role:agent -->
 - `mcp__hyperhive__request_next_turn()` — ask the harness to start another turn immediately after this one ends, even if the inbox is empty. Use for multi-turn tasks (long builds, sequential steps) where you want to continue without waiting for an external message. The next turn starts with `from: "self"` and `body: "continue"`. No-op if new inbox messages arrive before this turn ends (the harness already loops immediately on pending messages). No args.
+- `mcp__hyperhive__restart(name)` — *(requires `lifecycle` tool group)* restart a direct child sub-agent (stop + start). The server enforces topology: the call is rejected unless `name` is a direct child of yours per `topology.json`. No approval required.
 
 Need new packages, env vars, or other NixOS config for yourself? You can't edit your own config directly — message the manager (recipient `root`) describing what you need + why. The manager evaluates the request (it doesn't rubber-stamp), edits `/agents/{label}/config/agent.nix` on your behalf, commits, and submits an approval that the operator can accept on the dashboard; on approve hive-c0re rebuilds your container with the new config.
 

hive-ag3nt/src/mcp.rs

@@ -895,6 +895,29 @@ impl AgentServer {
         .await
     }
 
+    // IMPORTANT: this tool is only available when the `lifecycle` tool group
+    // is granted to this agent. hive-c0re enforces the topology check
+    // server-side: the call is rejected unless `name` is a direct child.
+    #[tool(
+        description = "Restart a direct child sub-agent container (stop + start). \
+            Only succeeds if `name` is a direct child of this agent in the topology \
+            tree — the server enforces this. No approval required."
+    )]
+    async fn restart(&self, Parameters(args): Parameters<RestartArgs>) -> String {
+        let log = format!("{args:?}");
+        let name = args.name.clone();
+        run_tool_envelope("restart", log, async move {
+            let (resp, retries) = self
+                .dispatch(hive_sh4re::AgentRequest::Restart { name: args.name })
+                .await;
+            annotate_retries(
+                format_ack(resp, "restart", format!("restarted {name}")),
+                retries,
+            )
+        })
+        .await
+    }
+
     // IMPORTANT: this tool is capability-gated (`read_host_journal`).
     // It is added to `--allowedTools` by `allowed_capability_tools` only
     // when `HIVE_CAPABILITIES` contains `read_host_journal`. hive-c0re

hive-c0re/src/agent_server.rs

@@ -361,6 +361,32 @@ async fn dispatch(req: &AgentRequest, agent: &str, coord: &Arc<Coordinator>) ->
                 Err(message) => AgentResponse::Err { message },
             }
         }
+        AgentRequest::Restart { name } => {
+            // Topology check: the caller must be the direct parent of the
+            // target. This is the only authorisation criterion — no
+            // capability flag needed; parenthood is sufficient privilege.
+            if !crate::topology::children_of(agent)
+                .iter()
+                .any(|c| c == name)
+            {
+                return AgentResponse::Err {
+                    message: format!(
+                        "agent `{agent}` cannot restart `{name}`: \
+                         not a direct child in the topology tree"
+                    ),
+                };
+            }
+            tracing::info!(%agent, %name, "agent: enqueue restart for child");
+            coord.rebuild_queue.enqueue(
+                crate::rebuild_queue::QueueKind::Restart,
+                name.to_owned(),
+                crate::rebuild_queue::QueueSource::Manual,
+                format!("agent `{agent}` restart tool"),
+                None,
+            );
+            coord.emit_rebuild_queue_snapshot();
+            AgentResponse::Ok
+        }
         // Manager-only variants are not valid on the agent socket.
         _ => AgentResponse::Err {
             message: "request not supported on agent socket".to_owned(),