diff --git a/hermes_cli/_subprocess_compat.py b/hermes_cli/_subprocess_compat.py
index 3813bfaab8..66f0d90a0b 100644
--- a/hermes_cli/_subprocess_compat.py
+++ b/hermes_cli/_subprocess_compat.py
@@ -50,6 +50,9 @@ __all__ = [
 
 IS_WINDOWS = sys.platform == "win32"
 
+# Private launcher-to-child metadata. This is diagnostic state, not user config.
+_WINDOWS_GATEWAY_BREAKAWAY_ENV = "_HERMES_GATEWAY_BREAKAWAY"
+
 
 def split_command_line(line: str) -> list[str]:
     """Split a user-supplied command line into tokens, Windows-safely.
diff --git a/hermes_cli/gateway.py b/hermes_cli/gateway.py
index 614d44b86d..11eca304ec 100644
--- a/hermes_cli/gateway.py
+++ b/hermes_cli/gateway.py
@@ -68,9 +68,6 @@ from hermes_cli.colors import Colors, color
 
 logger = logging.getLogger(__name__)
 
-# Private launcher-to-child metadata. This is diagnostic state, not user config.
-_WINDOWS_GATEWAY_BREAKAWAY_ENV = "_HERMES_GATEWAY_BREAKAWAY"
-
 # =============================================================================
 # Process Management (for manual gateway runs)
 # =============================================================================
@@ -2070,6 +2067,8 @@ def _windows_gateway_breakaway_state() -> bool | None:
     """Consume private spawn metadata without guessing for older launchers."""
     if not is_windows():
         return None
+    from hermes_cli._subprocess_compat import _WINDOWS_GATEWAY_BREAKAWAY_ENV
+
     value = os.environ.pop(_WINDOWS_GATEWAY_BREAKAWAY_ENV, None)
     if value == "1":
         return True
diff --git a/hermes_cli/gateway_windows.py b/hermes_cli/gateway_windows.py
index d31a70d8e2..59a1d28542 100644
--- a/hermes_cli/gateway_windows.py
+++ b/hermes_cli/gateway_windows.py
@@ -41,6 +41,7 @@ from pathlib import Path
 from xml.sax.saxutils import escape
 
 from hermes_cli._subprocess_compat import (
+    _WINDOWS_GATEWAY_BREAKAWAY_ENV,
     windows_detach_flags,
     windows_detach_flags_without_breakaway,
     windows_hide_flags,
@@ -48,9 +49,6 @@ from hermes_cli._subprocess_compat import (
 
 logger = logging.getLogger(__name__)
 
-# Private launcher-to-child metadata. This is diagnostic state, not user config.
-_GATEWAY_BREAKAWAY_ENV = "_HERMES_GATEWAY_BREAKAWAY"
-
 # Short timeouts: schtasks occasionally wedges and we don't want to hang forever.
 _SCHTASKS_TIMEOUT_S = 15
 _SCHTASKS_NO_OUTPUT_TIMEOUT_S = 30
@@ -919,7 +917,7 @@ def _spawn_detached(script_path: Path | None = None) -> int:
 
     # Inherit PATH etc. from the current env, overlay our required vars.
     env = {**os.environ, **env_overlay}
-    primary_env = {**env, _GATEWAY_BREAKAWAY_ENV: "1"}
+    primary_env = {**env, _WINDOWS_GATEWAY_BREAKAWAY_ENV: "1"}
 
     # CREATE_NEW_PROCESS_GROUP 0x00000200 — child gets its own group, won't
     #                                       receive Ctrl+C from our group
@@ -971,7 +969,7 @@ def _spawn_detached(script_path: Path | None = None) -> int:
             error_code,
         )
         flags_no_breakaway = windows_detach_flags_without_breakaway()
-        fallback_env = {**env, _GATEWAY_BREAKAWAY_ENV: "0"}
+        fallback_env = {**env, _WINDOWS_GATEWAY_BREAKAWAY_ENV: "0"}
         with open(stray_log, "ab", buffering=0) as log_fh:
             proc = subprocess.Popen(
                 argv,