diff --git a/hermes_constants.py b/hermes_constants.py
index 3bc56d4f7874c..ddca5e78df79a 100644
--- a/hermes_constants.py
+++ b/hermes_constants.py
@@ -137,6 +137,83 @@ def get_subprocess_home() -> str | None:
     return None
 
 
+def is_profiled_mode() -> bool:
+    """Return True if the current process is running under a named profile.
+
+    In profile mode, ``HERMES_HOME`` is ``<root>/profiles/<name>`` and the
+    agent should be restricted to its own data directory to prevent
+    cross-profile data leakage (reading another profile's memory, sessions,
+    or config).
+
+    The default profile (``HERMES_HOME == ~/.hermes``) returns ``False``
+    because the default profile is the admin — it needs access to all
+    profiles for management tasks (``profile list``, skill syncing, etc.).
+    """
+    env_home = os.environ.get("HERMES_HOME", "")
+    if not env_home:
+        return False
+    env_path = Path(env_home)
+    # Check if HERMES_HOME is <something>/profiles/<name>
+    return env_path.parent.name == "profiles"
+
+
+def get_profile_boundary() -> Path | None:
+    """Return the allowed root path for file operations, or None if unrestricted.
+
+    - Default profile (admin): returns ``None`` — full filesystem access.
+    - Named profile: returns ``HERMES_HOME`` (e.g. ``~/.hermes/profiles/frog/``).
+    """
+    if is_profiled_mode():
+        return get_hermes_home()
+    return None
+
+
+def is_within_profile_boundary(path: str) -> tuple[bool, str]:
+    """Check whether *path* is within the current profile's boundary.
+
+    Returns ``(allowed, reason)``.  When *allowed* is ``False``, *reason*
+    explains why (for the tool's error response).
+
+    The policy is **cross-profile isolation only** — we block access to
+    *other profiles' data directories* but allow everything else (home
+    directory projects, /tmp, system paths, installed packages, etc.).
+
+    This is intentionally NOT a full sandbox.  Named profiles still need
+    to read/write project code, system configs, and installed tools.
+    The goal is solely to prevent one profile from reading another
+    profile's memory, sessions, or config.
+    """
+    boundary = get_profile_boundary()
+    if boundary is None:
+        return True, ""
+
+    try:
+        resolved = Path(path).expanduser().resolve()
+    except (OSError, ValueError):
+        return True, ""  # Unresolvable paths are not our concern
+
+    # Get the parent profiles root: ~/.hermes/profiles/
+    profiles_root = boundary.resolve().parent  # <root>/profiles/
+
+    # If the path is NOT under the profiles root at all, allow it freely.
+    # This covers /tmp, ~/projects, /usr, etc.
+    try:
+        resolved.relative_to(profiles_root)
+    except ValueError:
+        return True, ""
+
+    # Path IS under ~/.hermes/profiles/ — check it's within OUR profile
+    try:
+        resolved.relative_to(boundary.resolve())
+        return True, ""
+    except ValueError:
+        return False, (
+            f"Access denied: '{path}' is in another profile's data directory. "
+            f"This agent is restricted to {display_hermes_home()}/ to prevent "
+            f"cross-profile data leakage."
+        )
+
+
 VALID_REASONING_EFFORTS = ("minimal", "low", "medium", "high", "xhigh")
 
 
diff --git a/tests/test_profile_boundary.py b/tests/test_profile_boundary.py
new file mode 100644
index 0000000000000..eeb511cb2a429
--- /dev/null
+++ b/tests/test_profile_boundary.py
@@ -0,0 +1,247 @@
+"""Tests for profile boundary enforcement in hermes_constants.
+
+Covers: is_profiled_mode(), get_profile_boundary(), is_within_profile_boundary().
+These functions enforce cross-profile isolation — a named profile must not
+access another profile's data directory, but should still have full access
+to the filesystem for project work.
+"""
+
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+from hermes_constants import (
+    is_profiled_mode,
+    get_profile_boundary,
+    is_within_profile_boundary,
+)
+
+
+@pytest.fixture()
+def default_env(tmp_path, monkeypatch):
+    """Default profile (admin) — unrestricted, full filesystem access."""
+    monkeypatch.setattr(Path, "home", lambda: tmp_path)
+    home = tmp_path / ".hermes"
+    home.mkdir()
+    monkeypatch.setenv("HERMES_HOME", str(home))
+    return home
+
+
+@pytest.fixture()
+def named_profile_env(tmp_path, monkeypatch):
+    """Named profile (e.g. 'frog') — restricted from other profiles."""
+    monkeypatch.setattr(Path, "home", lambda: tmp_path)
+    hermes_root = tmp_path / ".hermes"
+    hermes_root.mkdir()
+    profile_dir = hermes_root / "profiles" / "frog"
+    profile_dir.mkdir(parents=True)
+    monkeypatch.setenv("HERMES_HOME", str(profile_dir))
+    return profile_dir
+
+
+@pytest.fixture()
+def multi_profile_env(tmp_path, monkeypatch):
+    """Two named profiles to test cross-profile blocking."""
+    monkeypatch.setattr(Path, "home", lambda: tmp_path)
+    hermes_root = tmp_path / ".hermes"
+    hermes_root.mkdir()
+    frog_dir = hermes_root / "profiles" / "frog"
+    xiaoge_dir = hermes_root / "profiles" / "xiaoge"
+    frog_dir.mkdir(parents=True)
+    xiaoge_dir.mkdir(parents=True)
+    monkeypatch.setenv("HERMES_HOME", str(frog_dir))
+    return {
+        "root": hermes_root,
+        "frog": frog_dir,
+        "xiaoge": xiaoge_dir,
+    }
+
+
+# ===================================================================
+# is_profiled_mode
+# ===================================================================
+
+
+class TestIsProfiledMode:
+    def test_default_profile_returns_false(self, default_env):
+        assert is_profiled_mode() is False
+
+    def test_named_profile_returns_true(self, named_profile_env):
+        assert is_profiled_mode() is True
+
+    def test_no_hermes_home_returns_false(self, monkeypatch):
+        monkeypatch.delenv("HERMES_HOME", raising=False)
+        assert is_profiled_mode() is False
+
+    def test_custom_path_not_in_profiles_returns_false(self, tmp_path, monkeypatch):
+        """A custom HERMES_HOME like /opt/hermes is NOT a profile."""
+        custom = tmp_path / "opt" / "hermes"
+        custom.mkdir(parents=True)
+        monkeypatch.setenv("HERMES_HOME", str(custom))
+        assert is_profiled_mode() is False
+
+    def test_profiles_in_other_path_components(self, tmp_path, monkeypatch):
+        """HERMES_HOME=/tmp/profiles/work → profiled."""
+        p = tmp_path / "tmp" / "profiles" / "work"
+        p.mkdir(parents=True)
+        monkeypatch.setenv("HERMES_HOME", str(p))
+        assert is_profiled_mode() is True
+
+    def test_profiles_dir_name_but_not_structure(self, tmp_path, monkeypatch):
+        """HERMES_HOME=.../profiles → not profiled (parent is not 'profiles')."""
+        p = tmp_path / "profiles"
+        p.mkdir(parents=True)
+        monkeypatch.setenv("HERMES_HOME", str(p))
+        assert is_profiled_mode() is False
+
+
+# ===================================================================
+# get_profile_boundary
+# ===================================================================
+
+
+class TestGetProfileBoundary:
+    def test_default_profile_no_boundary(self, default_env):
+        assert get_profile_boundary() is None
+
+    def test_named_profile_returns_hermes_home(self, named_profile_env):
+        boundary = get_profile_boundary()
+        assert boundary is not None
+        assert boundary == named_profile_env
+
+    def test_no_hermes_home_no_boundary(self, monkeypatch):
+        monkeypatch.delenv("HERMES_HOME", raising=False)
+        assert get_profile_boundary() is None
+
+
+# ===================================================================
+# is_within_profile_boundary — DEFAULT profile (unrestricted)
+# ===================================================================
+
+
+class TestBoundaryDefaultProfile:
+    """Default profile should allow ALL paths."""
+
+    def test_allows_any_path(self, default_env):
+        for path in ["/etc/passwd", "/tmp/foo", "~/bar", "/any/thing"]:
+            ok, reason = is_within_profile_boundary(path)
+            assert ok is True, f"Should allow {path}, got: {reason}"
+
+    def test_allows_other_profiles(self, default_env, tmp_path):
+        """Admin profile can access other profiles' data."""
+        other = tmp_path / ".hermes" / "profiles" / "other" / "secret.md"
+        ok, reason = is_within_profile_boundary(str(other))
+        assert ok is True
+
+
+# ===================================================================
+# is_within_profile_boundary — NAMED profile (cross-profile isolation)
+# ===================================================================
+
+
+class TestBoundaryNamedProfile:
+    """Named profile: block other profiles, allow everything else."""
+
+    def test_allows_own_profile_files(self, named_profile_env):
+        own_file = named_profile_env / "skills" / "test.md"
+        ok, reason = is_within_profile_boundary(str(own_file))
+        assert ok is True
+
+    def test_allows_own_profile_nested(self, named_profile_env):
+        deep = named_profile_env / "sessions" / "sub" / "dir" / "file.json"
+        ok, reason = is_within_profile_boundary(str(deep))
+        assert ok is True
+
+    def test_blocks_other_profile_file(self, multi_profile_env):
+        other = multi_profile_env["xiaoge"] / "memory.md"
+        ok, reason = is_within_profile_boundary(str(other))
+        assert ok is False
+        assert "other profile" in reason
+
+    def test_blocks_other_profile_nested(self, multi_profile_env):
+        other = multi_profile_env["xiaoge"] / "sessions" / "deep" / "data.json"
+        ok, reason = is_within_profile_boundary(str(other))
+        assert ok is False
+
+    def test_blocks_other_profile_root(self, multi_profile_env):
+        """Even listing the other profile's root dir should be blocked."""
+        ok, reason = is_within_profile_boundary(str(multi_profile_env["xiaoge"]))
+        assert ok is False
+
+    def test_allows_system_files(self, named_profile_env):
+        ok, reason = is_within_profile_boundary("/etc/passwd")
+        assert ok is True, reason
+
+    def test_allows_tmp(self, named_profile_env):
+        ok, reason = is_within_profile_boundary("/tmp/test.txt")
+        assert ok is True, reason
+
+    def test_allows_home_projects(self, named_profile_env, tmp_path):
+        project = tmp_path / "projects" / "my-app" / "main.py"
+        ok, reason = is_within_profile_boundary(str(project))
+        assert ok is True, reason
+
+    def test_allows_default_hermes_config(self, multi_profile_env):
+        """~/.hermes/config.yaml is outside profiles/, so it's allowed."""
+        config = multi_profile_env["root"] / "config.yaml"
+        ok, reason = is_within_profile_boundary(str(config))
+        assert ok is True, reason
+
+    def test_allows_path_outside_hermes_entirely(self, named_profile_env):
+        ok, reason = is_within_profile_boundary("/usr/lib/python3/site.py")
+        assert ok is True, reason
+
+    def test_tilde_expansion(self, named_profile_env, tmp_path, monkeypatch):
+        """~ should expand correctly."""
+        monkeypatch.setenv("HOME", str(tmp_path))
+        ok, reason = is_within_profile_boundary("~/file.txt")
+        # ~/file.txt is not under profiles/, so allowed
+        assert ok is True, reason
+
+    def test_symlink_inside_own_profile(self, named_profile_env):
+        """A symlink pointing inside the profile should be allowed."""
+        target = named_profile_env / "real_file.txt"
+        target.touch()
+        link = named_profile_env / "link.txt"
+        link.symlink_to(target)
+        ok, reason = is_within_profile_boundary(str(link))
+        assert ok is True, reason
+
+    def test_symlink_to_other_profile(self, multi_profile_env):
+        """A symlink pointing to another profile should be BLOCKED."""
+        target = multi_profile_env["xiaoge"] / "secret.txt"
+        target.touch()
+        link = multi_profile_env["frog"] / "sneaky_link.txt"
+        link.symlink_to(target)
+        ok, reason = is_within_profile_boundary(str(link))
+        # resolve() follows symlinks → ends up in xiaoge → blocked
+        assert ok is False, "Symlink to other profile should be blocked"
+
+    def test_nonexistent_path_outside_profiles(self, named_profile_env):
+        """Nonexistent paths outside profiles/ should be allowed."""
+        ok, reason = is_within_profile_boundary("/nonexistent/path/file.txt")
+        assert ok is True, reason
+
+    def test_nonexistent_path_in_other_profile(self, multi_profile_env):
+        """Nonexistent paths in other profiles should still be blocked."""
+        other = multi_profile_env["xiaoge"] / "does_not_exist" / "file.txt"
+        ok, reason = is_within_profile_boundary(str(other))
+        assert ok is False
+
+    def test_error_message_mentions_profile_name(self, multi_profile_env):
+        other = multi_profile_env["xiaoge"] / "secret.md"
+        _, reason = is_within_profile_boundary(str(other))
+        # Should mention "frog" (current profile) in the message
+        assert "frog" in reason
+
+    def test_blocks_sibling_profile_same_depth(self, multi_profile_env):
+        """A file at the same nesting level but in another profile."""
+        frog_file = multi_profile_env["frog"] / "data.json"
+        xiaoge_file = multi_profile_env["xiaoge"] / "data.json"
+        # Make sure frog_file is allowed
+        ok, _ = is_within_profile_boundary(str(frog_file))
+        assert ok is True
+        # But xiaoge_file is blocked
+        ok, reason = is_within_profile_boundary(str(xiaoge_file))
+        assert ok is False
diff --git a/tools/file_tools.py b/tools/file_tools.py
index ca2118c33e296..1b1c9e58fb237 100644
--- a/tools/file_tools.py
+++ b/tools/file_tools.py
@@ -10,6 +10,7 @@
 from tools.binary_extensions import has_binary_extension
 from tools.file_operations import ShellFileOperations
 from agent.redact import redact_sensitive_text
+from hermes_constants import is_within_profile_boundary
 
 logger = logging.getLogger(__name__)
 
@@ -281,6 +282,11 @@ def clear_file_ops_cache(task_id: str = None):
 
 def read_file_tool(path: str, offset: int = 1, limit: int = 500, task_id: str = "default") -> str:
     """Read a file with pagination and line numbers."""
+    # ── Profile boundary guard ────────────────────────────────────
+    allowed, reason = is_within_profile_boundary(path)
+    if not allowed:
+        return json.dumps({"error": reason})
+
     try:
         # ── Device path guard ─────────────────────────────────────────
         # Block paths that would hang the process (infinite output,
@@ -540,6 +546,11 @@ def _check_file_staleness(filepath: str, task_id: str) -> str | None:
 
 def write_file_tool(path: str, content: str, task_id: str = "default") -> str:
     """Write content to a file."""
+    # ── Profile boundary guard ────────────────────────────────────
+    allowed, reason = is_within_profile_boundary(path)
+    if not allowed:
+        return json.dumps({"error": reason})
+
     sensitive_err = _check_sensitive_path(path)
     if sensitive_err:
         return tool_error(sensitive_err)
@@ -566,6 +577,16 @@ def patch_tool(mode: str = "replace", path: str = None, old_string: str = None,
                new_string: str = None, replace_all: bool = False, patch: str = None,
                task_id: str = "default") -> str:
     """Patch a file using replace mode or V4A patch format."""
+    # ── Profile boundary guard ────────────────────────────────────
+    # Check explicit path first, then extract paths from V4A patch content
+    _paths_to_check = []
+    if path:
+        _paths_to_check.append(path)
+    for _p in _paths_to_check:
+        allowed, reason = is_within_profile_boundary(_p)
+        if not allowed:
+            return json.dumps({"error": reason})
+
     # Check sensitive paths for both replace (explicit path) and V4A patch (extract paths)
     _paths_to_check = []
     if path:
@@ -624,6 +645,11 @@ def search_tool(pattern: str, target: str = "content", path: str = ".",
                 output_mode: str = "content", context: int = 0,
                 task_id: str = "default") -> str:
     """Search for content or files."""
+    # ── Profile boundary guard ────────────────────────────────────
+    allowed, reason = is_within_profile_boundary(path)
+    if not allowed:
+        return json.dumps({"error": reason})
+
     try:
         # Track searches to detect *consecutive* repeated search loops.
         # Include pagination args so users can page through truncated