diff --git a/tests/conftest.py b/tests/conftest.py
index 4fc15fd1e00a..40feed643768 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -158,6 +158,32 @@ def _looks_like_credential(name: str) -> bool:
     return any(name.endswith(suf) for suf in _CREDENTIAL_SUFFIXES)
 
 
+# Kanban env pins are legitimate production/operator controls: the CLI uses
+# them for board selection, the dispatcher injects them into worker processes,
+# and the gateway honours the dispatcher toggle. They still must be scrubbed
+# from pytest's ambient process env because tests that need Kanban context set
+# it explicitly and default-board tests rely on no ambient board/path pin.
+#
+# Scope this set to HERMES_KANBAN_* variables. The dispatcher also injects
+# HERMES_PROFILE for worker author attribution, but that is a broader profile
+# selector rather than a Kanban-specific pin and is intentionally out of this
+# narrow regression fix.
+_HERMES_KANBAN_BEHAVIORAL_VARS = frozenset({
+    # Board and path resolution pins.
+    "HERMES_KANBAN_BOARD",
+    "HERMES_KANBAN_DB",
+    "HERMES_KANBAN_HOME",
+    "HERMES_KANBAN_WORKSPACES_ROOT",
+    # Dispatcher-spawned worker runtime pins.
+    "HERMES_KANBAN_TASK",
+    "HERMES_KANBAN_WORKSPACE",
+    "HERMES_KANBAN_RUN_ID",
+    "HERMES_KANBAN_CLAIM_LOCK",
+    # Gateway dispatcher escape hatch.
+    "HERMES_KANBAN_DISPATCH_IN_GATEWAY",
+})
+
+
 # HERMES_* vars that change test behavior by being set. Unset all of these
 # unconditionally — individual tests that need them set do so explicitly.
 _HERMES_BEHAVIORAL_VARS = frozenset({
@@ -188,6 +214,7 @@ def _looks_like_credential(name: str) -> bool:
     "HERMES_BACKGROUND_NOTIFICATIONS",
     "HERMES_EXEC_ASK",
     "HERMES_HOME_MODE",
+    *_HERMES_KANBAN_BEHAVIORAL_VARS,
     "TERMINAL_CWD",
     "TERMINAL_ENV",
     "TERMINAL_VERCEL_RUNTIME",
diff --git a/tests/test_hermetic_environment.py b/tests/test_hermetic_environment.py
new file mode 100644
index 000000000000..54434bdec2e2
--- /dev/null
+++ b/tests/test_hermetic_environment.py
@@ -0,0 +1,33 @@
+"""Regression coverage for process-level pytest environment isolation."""
+
+from __future__ import annotations
+
+import os
+
+import tests.conftest as hermes_conftest
+
+
+def test_kanban_env_pins_do_not_leak_from_pytest_process_env():
+    """Ambient Kanban pins must not be visible inside test bodies.
+
+    Hermes sessions and dispatcher workers legitimately export these variables,
+    so local developer shells can carry them into `pytest`. The global hermetic
+    fixture owns clearing them; individual Kanban tests opt back in with
+    `monkeypatch.setenv(...)` when a variable is part of the behavior under test.
+    """
+
+    leaked = {
+        name: os.environ[name]
+        for name in sorted(hermes_conftest._HERMES_KANBAN_BEHAVIORAL_VARS)
+        if name in os.environ
+    }
+
+    assert leaked == {}
+
+
+def test_tests_can_still_set_kanban_env_pins_explicitly(monkeypatch):
+    """The hermetic fixture clears ambient state, not test-local setup."""
+
+    monkeypatch.setenv("HERMES_KANBAN_BOARD", "explicit-test-board")
+
+    assert os.environ["HERMES_KANBAN_BOARD"] == "explicit-test-board"