fix(#2018): surface permission error in hivectl agent lookup instead of misleading 'no such agent'

hive-c0re/src/bin/hivectl.rs

@@ -933,8 +933,26 @@ fn human_bytes(n: u64) -> String {
 /// state dir (not the live container list) so kept-state tombstones
 /// still resolve as agents — re-provisioning a destroyed-but-kept agent
 /// should still drop its token in the existing state tree.
-fn is_agent(name: &str) -> bool {
+///
-    Coordinator::agent_state_root(name).exists()
+/// Uses `try_exists()` rather than `Path::exists()` so a permission
+/// error reaching the agents root is surfaced, not collapsed into
+/// `false`. The agents root is `0700 hive-core`, so running hivectl
+/// without root yields EACCES on traversal — `Path::exists()` would
+/// silently report `false`, which callers turn into a misleading "no
+/// such agent" (or, for the create-user paths, a silent misclassify of
+/// a real agent as a non-agent account). Mapping EACCES to an explicit
+/// "needs root" error fixes that first-run footgun (#2018).
+fn agent_exists(name: &str) -> Result<bool> {
+    let root = Coordinator::agent_state_root(name);
+    match root.try_exists() {
+        Ok(found) => Ok(found),
+        Err(e) if e.kind() == std::io::ErrorKind::PermissionDenied => bail!(
+            "cannot read the agents root {} (permission denied) - this command needs root; \
+             re-run with sudo",
+            root.parent().unwrap_or(&root).display()
+        ),
+        Err(e) => Err(e).with_context(|| format!("check agent state dir {}", root.display())),
+    }
 }
 
 /// Drop into an interactive Claude session in the agent container.
@@ -973,7 +991,7 @@ fn is_agent(name: &str) -> bool {
 /// `machinectl shell` inherits the caller's PTY, so the session is
 /// fully interactive. Requires root and a running container.
 fn choom(name: &str, fresh: bool) -> Result<()> {
-    if !is_agent(name) {
+    if !agent_exists(name)? {
         bail!("no such agent: '{name}' (no state dir under /var/lib/hyperhive/agents/)");
     }
     let container = hive_c0re::lifecycle::container_name(name);
@@ -1023,7 +1041,7 @@ async fn forge_create_user(name: &str, password: Option<&str>, password_stdin: b
         );
     }
     let user_password = resolve_password(password, password_stdin)?;
-    if is_agent(name) {
+    if agent_exists(name)? {
         if user_password.is_some() {
             bail!(
                 "forge create-user: --password / --password-stdin is for non-agent (operator) accounts only; '{name}' is an agent which authenticates via API token"
@@ -1095,7 +1113,7 @@ async fn matrix_create_user(
         .build()
         .context("build reqwest client")?;
     let user_password = resolve_password(password, password_stdin)?;
-    if is_agent(name) {
+    if agent_exists(name)? {
         if user_password.is_some() {
             // The boot-sweep / approval-time agent provisioning path
             // doesn't accept a password — agents auth by access_token,
@@ -1421,7 +1439,7 @@ fn single_agent_scope(name: &str) -> hive_sh4re::LifecycleScope {
 /// regardless of the migration outcome so a failed migration never leaves
 /// the agent down; the migration error (if any) is surfaced afterwards.
 async fn subvol_upgrade(socket: &Path, name: &str, yes: bool) -> Result<()> {
-    if !is_agent(name) {
+    if !agent_exists(name)? {
         bail!("no agent named {name:?} (no state dir under the agents root)");
     }
     if !yes {