diff --git a/hermes_cli/config.py b/hermes_cli/config.py
index a981b1bbb..80dce6c04 100644
--- a/hermes_cli/config.py
+++ b/hermes_cli/config.py
@@ -197,14 +197,44 @@ def _ensure_default_soul_md(home: Path) -> None:
 
 
 def ensure_hermes_home():
-    """Ensure ~/.hermes directory structure exists with secure permissions."""
+    """Ensure ~/.hermes directory structure exists with secure permissions.
+
+    In managed mode (NixOS), dirs are created by the activation script with
+    setgid + group-writable (2770). We skip mkdir and set umask(0o007) so
+    any files created (e.g. SOUL.md) are group-writable (0660).
+    """
     home = get_hermes_home()
-    home.mkdir(parents=True, exist_ok=True)
-    _secure_dir(home)
+    if is_managed():
+        old_umask = os.umask(0o007)
+        try:
+            _ensure_hermes_home_managed(home)
+        finally:
+            os.umask(old_umask)
+    else:
+        home.mkdir(parents=True, exist_ok=True)
+        _secure_dir(home)
+        for subdir in ("cron", "sessions", "logs", "memories"):
+            d = home / subdir
+            d.mkdir(parents=True, exist_ok=True)
+            _secure_dir(d)
+        _ensure_default_soul_md(home)
+
+
+def _ensure_hermes_home_managed(home: Path):
+    """Managed-mode variant: verify dirs exist (activation creates them), seed SOUL.md."""
+    if not home.is_dir():
+        raise RuntimeError(
+            f"HERMES_HOME {home} does not exist. "
+            "Run 'sudo nixos-rebuild switch' first."
+        )
     for subdir in ("cron", "sessions", "logs", "memories"):
         d = home / subdir
-        d.mkdir(parents=True, exist_ok=True)
-        _secure_dir(d)
+        if not d.is_dir():
+            raise RuntimeError(
+                f"{d} does not exist. "
+                "Run 'sudo nixos-rebuild switch' first."
+            )
+    # Inside umask(0o007) scope — SOUL.md will be created as 0660
     _ensure_default_soul_md(home)
 
 
diff --git a/hermes_logging.py b/hermes_logging.py
index 6d8f4fa7b..5d71590c3 100644
--- a/hermes_logging.py
+++ b/hermes_logging.py
@@ -13,6 +13,7 @@ secrets are never written to disk.
 """
 
 import logging
+import os
 from logging.handlers import RotatingFileHandler
 from pathlib import Path
 from typing import Optional
@@ -177,6 +178,38 @@ def setup_verbose_logging() -> None:
 # Internal helpers
 # ---------------------------------------------------------------------------
 
+class _ManagedRotatingFileHandler(RotatingFileHandler):
+    """RotatingFileHandler that ensures group-writable perms in managed mode.
+
+    In managed mode (NixOS), the stateDir uses setgid (2770) so new files
+    inherit the hermes group. However, both _open() (initial creation) and
+    doRollover() create files via open(), which uses the process umask —
+    typically 0022, producing 0644. This subclass applies chmod 0660 after
+    both operations so the gateway and interactive users can share log files.
+    """
+
+    def __init__(self, *args, **kwargs):
+        from hermes_cli.config import is_managed
+        self._managed = is_managed()
+        super().__init__(*args, **kwargs)
+
+    def _chmod_if_managed(self):
+        if self._managed:
+            try:
+                os.chmod(self.baseFilename, 0o660)
+            except OSError:
+                pass
+
+    def _open(self):
+        stream = super()._open()
+        self._chmod_if_managed()
+        return stream
+
+    def doRollover(self):
+        super().doRollover()
+        self._chmod_if_managed()
+
+
 def _add_rotating_handler(
     logger: logging.Logger,
     path: Path,
@@ -198,7 +231,7 @@ def _add_rotating_handler(
             return  # already attached
 
     path.parent.mkdir(parents=True, exist_ok=True)
-    handler = RotatingFileHandler(
+    handler = _ManagedRotatingFileHandler(
         str(path), maxBytes=max_bytes, backupCount=backup_count,
     )
     handler.setLevel(level)
diff --git a/nix/nixosModules.nix b/nix/nixosModules.nix
index 948f7df8c..b1be031df 100644
--- a/nix/nixosModules.nix
+++ b/nix/nixosModules.nix
@@ -560,10 +560,14 @@
       # ── Directories ───────────────────────────────────────────────────
       {
         systemd.tmpfiles.rules = [
-          "d ${cfg.stateDir}                0750 ${cfg.user} ${cfg.group} - -"
-          "d ${cfg.stateDir}/.hermes        0750 ${cfg.user} ${cfg.group} - -"
+          "d ${cfg.stateDir}                2770 ${cfg.user} ${cfg.group} - -"
+          "d ${cfg.stateDir}/.hermes        2770 ${cfg.user} ${cfg.group} - -"
+          "d ${cfg.stateDir}/.hermes/cron   2770 ${cfg.user} ${cfg.group} - -"
+          "d ${cfg.stateDir}/.hermes/sessions 2770 ${cfg.user} ${cfg.group} - -"
+          "d ${cfg.stateDir}/.hermes/logs   2770 ${cfg.user} ${cfg.group} - -"
+          "d ${cfg.stateDir}/.hermes/memories 2770 ${cfg.user} ${cfg.group} - -"
           "d ${cfg.stateDir}/home           0750 ${cfg.user} ${cfg.group} - -"
-          "d ${cfg.workingDirectory}         0750 ${cfg.user} ${cfg.group} - -"
+          "d ${cfg.workingDirectory}         2770 ${cfg.user} ${cfg.group} - -"
         ];
       }
 
@@ -575,7 +579,21 @@
           mkdir -p ${cfg.stateDir}/home
           mkdir -p ${cfg.workingDirectory}
           chown ${cfg.user}:${cfg.group} ${cfg.stateDir} ${cfg.stateDir}/.hermes ${cfg.stateDir}/home ${cfg.workingDirectory}
-          chmod 0750 ${cfg.stateDir} ${cfg.stateDir}/.hermes ${cfg.stateDir}/home ${cfg.workingDirectory}
+          chmod 2770 ${cfg.stateDir} ${cfg.stateDir}/.hermes ${cfg.workingDirectory}
+          chmod 0750 ${cfg.stateDir}/home
+
+          # Create subdirs, set setgid + group-writable, migrate existing files.
+          # Nix-managed files (config.yaml, .env, .managed) stay 0640/0644.
+          find ${cfg.stateDir}/.hermes -maxdepth 1 \
+            \( -name "*.db" -o -name "*.db-wal" -o -name "*.db-shm" -o -name "SOUL.md" \) \
+            -exec chmod g+rw {} + 2>/dev/null || true
+          for _subdir in cron sessions logs memories; do
+            mkdir -p "${cfg.stateDir}/.hermes/$_subdir"
+            chown ${cfg.user}:${cfg.group} "${cfg.stateDir}/.hermes/$_subdir"
+            chmod 2770 "${cfg.stateDir}/.hermes/$_subdir"
+            find "${cfg.stateDir}/.hermes/$_subdir" -type f \
+              -exec chmod g+rw {} + 2>/dev/null || true
+          done
 
           # Merge Nix settings into existing config.yaml.
           # Preserves user-added keys (skills, streaming, etc.); Nix keys win.
@@ -662,6 +680,10 @@ HERMES_NIX_ENV_EOF
             Restart = cfg.restart;
             RestartSec = cfg.restartSec;
 
+            # Shared-state: files created by the gateway should be group-writable
+            # so interactive users in the hermes group can read/write them.
+            UMask = "0007";
+
             # Hardening
             NoNewPrivileges = true;
             ProtectSystem = "strict";
diff --git a/tests/test_hermes_logging.py b/tests/test_hermes_logging.py
index 5b40e6323..80a23dc68 100644
--- a/tests/test_hermes_logging.py
+++ b/tests/test_hermes_logging.py
@@ -2,6 +2,7 @@
 
 import logging
 import os
+import stat
 from logging.handlers import RotatingFileHandler
 from pathlib import Path
 from unittest.mock import patch
@@ -300,6 +301,59 @@ class TestAddRotatingHandler:
                 logger.removeHandler(h)
                 h.close()
 
+    def test_managed_mode_initial_open_sets_group_writable(self, tmp_path):
+        log_path = tmp_path / "managed-open.log"
+        logger = logging.getLogger("_test_rotating_managed_open")
+        formatter = logging.Formatter("%(message)s")
+
+        old_umask = os.umask(0o022)
+        try:
+            with patch("hermes_cli.config.is_managed", return_value=True):
+                hermes_logging._add_rotating_handler(
+                    logger, log_path,
+                    level=logging.INFO, max_bytes=1024, backup_count=1,
+                    formatter=formatter,
+                )
+        finally:
+            os.umask(old_umask)
+
+        assert log_path.exists()
+        assert stat.S_IMODE(log_path.stat().st_mode) == 0o660
+
+        for h in list(logger.handlers):
+            if isinstance(h, RotatingFileHandler):
+                logger.removeHandler(h)
+                h.close()
+
+    def test_managed_mode_rollover_sets_group_writable(self, tmp_path):
+        log_path = tmp_path / "managed-rollover.log"
+        logger = logging.getLogger("_test_rotating_managed_rollover")
+        formatter = logging.Formatter("%(message)s")
+
+        old_umask = os.umask(0o022)
+        try:
+            with patch("hermes_cli.config.is_managed", return_value=True):
+                hermes_logging._add_rotating_handler(
+                    logger, log_path,
+                    level=logging.INFO, max_bytes=1, backup_count=1,
+                    formatter=formatter,
+                )
+                handler = next(
+                    h for h in logger.handlers if isinstance(h, RotatingFileHandler)
+                )
+                logger.info("a" * 256)
+                handler.flush()
+        finally:
+            os.umask(old_umask)
+
+        assert log_path.exists()
+        assert stat.S_IMODE(log_path.stat().st_mode) == 0o660
+
+        for h in list(logger.handlers):
+            if isinstance(h, RotatingFileHandler):
+                logger.removeHandler(h)
+                h.close()
+
 
 class TestReadLoggingConfig:
     """_read_logging_config() reads from config.yaml."""