diff --git a/hive-ag3nt/src/paths.rs b/hive-ag3nt/src/paths.rs
index edc7bad3..21e4aa1c 100644
--- a/hive-ag3nt/src/paths.rs
+++ b/hive-ag3nt/src/paths.rs
@@ -23,6 +23,22 @@ pub fn state_dir() -> PathBuf {
     PathBuf::from(format!("/agents/{label}/state"))
 }
 
+/// Per-turn config dir for the regenerated claude-{mcp-config,settings,
+/// system-prompt} files the harness drops before each turn. Set by
+/// systemd via `RuntimeDirectory = "hive-config"` (#658 fixup): a
+/// per-service runtime dir owned by the agent unix user, auto-cleared
+/// on stop. Kept separate from `/run/hive` (the host-owned mcp.sock
+/// bind) so the harness owns its own write surface and we don't have
+/// to chown a bind-mounted dir. Overridable via `HYPERHIVE_CONFIG_DIR`
+/// for dev / test scenarios.
+#[must_use]
+pub fn config_dir() -> PathBuf {
+    if let Some(p) = std::env::var_os("HYPERHIVE_CONFIG_DIR") {
+        return PathBuf::from(p);
+    }
+    PathBuf::from("/run/hive-config")
+}
+
 /// Claude credentials directory for the current agent. `$HOME/.claude`
 /// matches what the `claude` CLI reads at runtime — both binaries see
 /// the same `$HOME` set by the per-service systemd `environment`
diff --git a/hive-ag3nt/src/prompt.rs b/hive-ag3nt/src/prompt.rs
index 6178e015..9b6ff5e1 100644
--- a/hive-ag3nt/src/prompt.rs
+++ b/hive-ag3nt/src/prompt.rs
@@ -126,9 +126,9 @@ fn parse_close_marker(line: &str) -> Option<&str> {
 /// # Errors
 ///
 /// Returns an error if the system prompt file cannot be written.
-pub async fn write_system_prompt(socket: &Path, label: &str, flavor: Flavor) -> Result<PathBuf> {
-    let parent = socket.parent().unwrap_or_else(|| Path::new("/run/hive"));
-    tokio::fs::create_dir_all(parent).await.ok();
+pub async fn write_system_prompt(_socket: &Path, label: &str, flavor: Flavor) -> Result<PathBuf> {
+    let parent = crate::paths::config_dir();
+    tokio::fs::create_dir_all(&parent).await.ok();
     let pronouns = std::env::var("HIVE_OPERATOR_PRONOUNS").unwrap_or_else(|_| "she/her".to_owned());
     let template_path = hive_sh4re::assets::prompt_template();
     let template = tokio::fs::read_to_string(&template_path)
diff --git a/hive-ag3nt/src/turn.rs b/hive-ag3nt/src/turn.rs
index 885b5a99..95c9f0d8 100644
--- a/hive-ag3nt/src/turn.rs
+++ b/hive-ag3nt/src/turn.rs
@@ -136,8 +136,8 @@ impl TurnFiles {
 ///
 /// Returns an error if the config file cannot be written.
 pub async fn write_mcp_config(socket: &Path) -> Result<PathBuf> {
-    let parent = socket.parent().unwrap_or_else(|| Path::new("/run/hive"));
-    tokio::fs::create_dir_all(parent).await.ok();
+    let parent = crate::paths::config_dir();
+    tokio::fs::create_dir_all(&parent).await.ok();
     let path = parent.join("claude-mcp-config.json");
     let exe = std::env::current_exe()
         .ok()
@@ -155,9 +155,9 @@ pub async fn write_mcp_config(socket: &Path) -> Result<PathBuf> {
 /// # Errors
 ///
 /// Returns an error if the settings file cannot be written.
-pub async fn write_settings(socket: &Path) -> Result<PathBuf> {
-    let parent = socket.parent().unwrap_or_else(|| Path::new("/run/hive"));
-    tokio::fs::create_dir_all(parent).await.ok();
+pub async fn write_settings(_socket: &Path) -> Result<PathBuf> {
+    let parent = crate::paths::config_dir();
+    tokio::fs::create_dir_all(&parent).await.ok();
     let path = parent.join("claude-settings.json");
     // #555: source-of-truth is `$HIVE_ASSETS_DIR/prompts/claude-settings.json`;
     // copy through the per-agent runtime dir so claude reads it from the
diff --git a/nix/templates/agent-base.nix b/nix/templates/agent-base.nix
index ffbc826b..01fceb1a 100644
--- a/nix/templates/agent-base.nix
+++ b/nix/templates/agent-base.nix
@@ -38,14 +38,14 @@ in
       ExecStart = "${pkgs.hyperhive}/bin/hive-ag3nt serve";
       Restart = "on-failure";
       RestartSec = 2;
-      # `/run/hive` is bind-mounted from the host root-owned 0755
-      # (hive-c0re's `set_nspawn_flags`). Post-#658 the harness
-      # runs as the per-agent user and needs to drop mcp.sock +
-      # claude-{mcp-config,settings,system-prompt} files there.
-      # `+` runs ExecStartPre as root (before the User= drop) so
-      # we can chown the bind onto the agent user every start —
-      # robust against activation-script timing on first boot.
-      ExecStartPre = "+${pkgs.coreutils}/bin/chown -R ${userName}:${userName} /run/hive";
+      # `/run/hive-config/` is a per-service runtime dir owned by
+      # the agent user (`User=` below), auto-cleared by systemd on
+      # stop. The harness writes its regenerated
+      # claude-{mcp-config,settings,system-prompt} files there
+      # (see `paths::config_dir`). Kept separate from `/run/hive`
+      # — that bind comes in root-owned from the host and holds
+      # hive-c0re's `mcp.sock` we only connect to (#658 fixup).
+      RuntimeDirectory = "hive-config";
       # Run the harness as the per-agent user (#658). claude itself
       # spawned by the harness then runs as that user too — drops
       # root inside the container while sudo (`NOPASSWD: ALL` by
diff --git a/nix/templates/harness-base.nix b/nix/templates/harness-base.nix
index 6b9331f1..cc4b0bbb 100644
--- a/nix/templates/harness-base.nix
+++ b/nix/templates/harness-base.nix
@@ -687,6 +687,18 @@ in
         [ -d "$stateDir" ] || continue
         chown -hR "$userName:$userName" "$stateDir" 2>/dev/null || true
       done
+      # Same treatment for the bind-mounted `~/.claude/` dir. Pre-#658
+      # the harness ran as root and `claude` wrote `.credentials.json`
+      # there 0600 root:root; post-#658 the harness reads
+      # `~/.claude/` as the agent user to decide Online vs
+      # NeedsLogin (`login::has_session`), and the host-side bind
+      # source is still root-owned 0700 from those legacy writes.
+      # Chown recursively so the existing credentials are readable
+      # under the new identity instead of getting silently treated
+      # as "no session" and re-prompting login every boot.
+      if [ -d "$homeDir/.claude" ]; then
+        chown -hR "$userName:$userName" "$homeDir/.claude" 2>/dev/null || true
+      fi
     '';
 
     # Auto-inject the matrix MCP entry when matrix is enabled (#548
diff --git a/nix/templates/manager.nix b/nix/templates/manager.nix
index 394ab374..66e9035d 100644
--- a/nix/templates/manager.nix
+++ b/nix/templates/manager.nix
@@ -48,14 +48,14 @@ in
       ExecStart = "${pkgs.hyperhive}/bin/hive-m1nd serve";
       Restart = "on-failure";
       RestartSec = 2;
-      # `/run/hive` is bind-mounted from the host root-owned 0755
-      # (hive-c0re's `set_nspawn_flags`). Post-#658 the harness
-      # runs as the per-agent user and needs to drop mcp.sock +
-      # claude-{mcp-config,settings,system-prompt} files there.
-      # `+` runs ExecStartPre as root (before the User= drop) so
-      # we can chown the bind onto the agent user every start —
-      # robust against activation-script timing on first boot.
-      ExecStartPre = "+${pkgs.coreutils}/bin/chown -R ${userName}:${userName} /run/hive";
+      # `/run/hive-config/` is a per-service runtime dir owned by
+      # the agent user (`User=` below), auto-cleared by systemd on
+      # stop. The harness writes its regenerated
+      # claude-{mcp-config,settings,system-prompt} files there
+      # (see `paths::config_dir`). Kept separate from `/run/hive`
+      # — that bind comes in root-owned from the host and holds
+      # hive-c0re's `mcp.sock` we only connect to (#658 fixup).
+      RuntimeDirectory = "hive-config";
       # Same drop-from-root as agent-base.nix (#658). Manager
       # interactions with the host (rebuild approvals, config
       # writes) still happen via the dedicated unix sockets