diff --git a/hermes_cli/main.py b/hermes_cli/main.py
index f728159da32..2e3ae37bb2f 100644
--- a/hermes_cli/main.py
+++ b/hermes_cli/main.py
@@ -144,11 +144,19 @@ def _apply_profile_override() -> None:
             profile_name = None
             consume = 0
 
-    # 1.5 If HERMES_HOME is already set and no explicit flag was given, trust it.
-    # This lets child processes (relaunch, subprocess) inherit the parent's
-    # profile choice without having to pass --profile again.
-    if profile_name is None and os.environ.get("HERMES_HOME"):
-        return
+    # 1.5 If HERMES_HOME is already set and no explicit flag was given, trust it
+    # only when it already points to a specific profile directory.  The
+    # distinguishing heuristic: a profile path has "profiles" as its immediate
+    # parent directory name (e.g. ~/.hermes/profiles/coder or
+    # /opt/data/profiles/coder).  If HERMES_HOME points to the hermes root
+    # instead (e.g. systemd hardcodes HERMES_HOME=/root/.hermes), we must
+    # still read active_profile — the user may have switched profiles via
+    # `hermes profile use` and the gateway should honour that choice.
+    # See issue #22502.
+    hermes_home_env = os.environ.get("HERMES_HOME", "")
+    if profile_name is None and hermes_home_env:
+        if Path(hermes_home_env).parent.name == "profiles":
+            return
 
     # 2. If no flag, check active_profile in the hermes root
     if profile_name is None:
diff --git a/tests/hermes_cli/test_apply_profile_override.py b/tests/hermes_cli/test_apply_profile_override.py
new file mode 100644
index 00000000000..c17c10c439f
--- /dev/null
+++ b/tests/hermes_cli/test_apply_profile_override.py
@@ -0,0 +1,141 @@
+"""Regression tests for _apply_profile_override HERMES_HOME guard (issue #22502).
+
+When HERMES_HOME is set to the hermes root (e.g. systemd hardcodes
+HERMES_HOME=/root/.hermes), _apply_profile_override must still read
+active_profile and update HERMES_HOME to the profile directory.
+
+When HERMES_HOME is already a profile directory (.../profiles/<name>),
+_apply_profile_override must trust it and return without re-reading
+active_profile (child-process inheritance contract).
+"""
+
+from __future__ import annotations
+
+import os
+import sys
+from pathlib import Path
+
+import pytest
+
+
+def _run_apply_profile_override(
+    tmp_path, monkeypatch, *, hermes_home: str | None, active_profile: str | None,
+    argv: list[str] | None = None,
+):
+    """Run _apply_profile_override in isolation.
+
+    Returns the value of os.environ["HERMES_HOME"] after the call,
+    or None if unset.
+    """
+    hermes_root = tmp_path / ".hermes"
+    hermes_root.mkdir(parents=True, exist_ok=True)
+
+    if active_profile is not None:
+        (hermes_root / "active_profile").write_text(active_profile)
+
+    if active_profile and active_profile != "default":
+        (hermes_root / "profiles" / active_profile).mkdir(parents=True, exist_ok=True)
+
+    monkeypatch.setattr(Path, "home", lambda: tmp_path)
+    if hermes_home is not None:
+        monkeypatch.setenv("HERMES_HOME", hermes_home)
+    else:
+        monkeypatch.delenv("HERMES_HOME", raising=False)
+
+    monkeypatch.setattr(sys, "argv", argv or ["hermes", "gateway", "start"])
+
+    from hermes_cli.main import _apply_profile_override
+    _apply_profile_override()
+
+    return os.environ.get("HERMES_HOME")
+
+
+class TestApplyProfileOverrideHermesHomeGuard:
+    """Regression guard for issue #22502.
+
+    Verifies that HERMES_HOME pointing to the hermes root does NOT suppress
+    the active_profile check, while HERMES_HOME already pointing to a
+    profile directory IS trusted as-is.
+    """
+
+    def test_hermes_home_at_root_with_active_profile_is_redirected(
+        self, tmp_path, monkeypatch
+    ):
+        """HERMES_HOME=/root/.hermes + active_profile=coder must redirect
+        HERMES_HOME to .../profiles/coder.
+
+        Bug scenario from #22502: systemd sets HERMES_HOME to the hermes root
+        and the user switches to a profile via `hermes profile use`.
+        Before the fix, the guard returned early and active_profile was ignored.
+        """
+        hermes_root = tmp_path / ".hermes"
+        hermes_root.mkdir(parents=True, exist_ok=True)
+
+        result = _run_apply_profile_override(
+            tmp_path,
+            monkeypatch,
+            hermes_home=str(hermes_root),
+            active_profile="coder",
+        )
+
+        assert result is not None, "HERMES_HOME must be set after profile redirect"
+        assert "profiles" in result, (
+            f"Expected HERMES_HOME to point into profiles/ dir, got: {result!r}"
+        )
+        assert result.endswith("coder"), (
+            f"Expected HERMES_HOME to end with 'coder', got: {result!r}"
+        )
+
+    def test_hermes_home_already_profile_dir_is_trusted(self, tmp_path, monkeypatch):
+        """HERMES_HOME=.../profiles/coder must not be overridden even when
+        active_profile says something different.
+
+        Preserves the child-process inheritance contract: a subprocess spawned
+        with HERMES_HOME already set to a specific profile must stay in that
+        profile.
+        """
+        hermes_root = tmp_path / ".hermes"
+        profile_dir = hermes_root / "profiles" / "coder"
+        profile_dir.mkdir(parents=True, exist_ok=True)
+
+        (hermes_root / "active_profile").write_text("other")
+
+        monkeypatch.setattr(Path, "home", lambda: tmp_path)
+        monkeypatch.setenv("HERMES_HOME", str(profile_dir))
+        monkeypatch.setattr(sys, "argv", ["hermes", "gateway", "start"])
+
+        from hermes_cli.main import _apply_profile_override
+        _apply_profile_override()
+
+        assert os.environ.get("HERMES_HOME") == str(profile_dir), (
+            "HERMES_HOME must remain unchanged when already pointing to a profile dir"
+        )
+
+    def test_hermes_home_unset_reads_active_profile(self, tmp_path, monkeypatch):
+        """Classic case: HERMES_HOME unset + active_profile=coder must set
+        HERMES_HOME to the profile directory (existing behaviour must not regress).
+        """
+        result = _run_apply_profile_override(
+            tmp_path,
+            monkeypatch,
+            hermes_home=None,
+            active_profile="coder",
+        )
+
+        assert result is not None
+        assert "coder" in result
+
+    def test_hermes_home_unset_default_profile_no_redirect(self, tmp_path, monkeypatch):
+        """active_profile=default must not redirect HERMES_HOME."""
+        hermes_root = tmp_path / ".hermes"
+        hermes_root.mkdir(parents=True, exist_ok=True)
+
+        monkeypatch.setattr(Path, "home", lambda: tmp_path)
+        monkeypatch.delenv("HERMES_HOME", raising=False)
+        monkeypatch.setattr(sys, "argv", ["hermes", "gateway", "start"])
+        (hermes_root / "active_profile").write_text("default")
+
+        from hermes_cli.main import _apply_profile_override
+        _apply_profile_override()
+
+        assert os.environ.get("HERMES_HOME") is None