diff --git a/tests/test_smoke.py b/tests/test_smoke.py
index 66ceb97..d9f550a 100644
--- a/tests/test_smoke.py
+++ b/tests/test_smoke.py
@@ -50,6 +50,18 @@ XR = os.path.join(ROOT, "build", "xreqs")
 LOG = "/tmp/tabtest.log"
 _log_seq = [0]
 
+# Nested compositors must boot nested even when the ambient environment
+# leaks mode-forcing variables (a WLR_BACKENDS=drm,libinput left over from
+# VT standalone experiments, or KICK_MODE): the leak flips the spawned
+# compositor to standalone, its DRM backend fails on the busy seat, and the
+# test dies at boot ("startup tab never mapped") for reasons unrelated to
+# what it asserts.  Strip just those two; the host connection
+# (WAYLAND_DISPLAY) and socket dir (XDG_RUNTIME_DIR) must pass through, so
+# `env -i` (as standalone_session uses) is wrong here.  Precedent: the
+# kick-in-kick spawn already pops both via an env dict, and KICK_LIBDECOR
+# passes through only when set.
+_NESTED_ENV_STRIP = ["-u", "WLR_BACKENDS", "-u", "KICK_MODE"]
+
 
 def _fresh_log():
     """A unique per-spawn log path.
@@ -683,7 +695,8 @@ def session():
     dump_dir = _mk_dump_dir()
 
     proc = subprocess.Popen(
-        ["env", "KICK_LOG=2", "KICK_SYNTH_INPUT=1",
+        ["env"] + _NESTED_ENV_STRIP + [
+         "KICK_LOG=2", "KICK_SYNTH_INPUT=1",
          "KICK_DUMP_DIR=" + dump_dir,
          "KICK_REPEAT_DELAY_MS=" + KICK_REPEAT_TEST_DELAY, "stdbuf", "-oL",
          BIN, f"{WL} '{RED}'", f"{WL} '{BLUE}'"],
@@ -2996,7 +3009,8 @@ def _nested_session(*tabs, extra_args=(), repeat_off=True):
         # KICK_LIBDECOR passes through only when set: an empty value would
         # force the libdecor path (any non-"0" value does), so default runs
         # must not see the variable at all.
-        cmd = ["env", "KICK_LOG=2", "KICK_SYNTH_INPUT=1",
+        cmd = ["env"] + _NESTED_ENV_STRIP + [
+               "KICK_LOG=2", "KICK_SYNTH_INPUT=1",
                "KICK_DUMP_DIR=" + dump_dir,
                "KICK_REPEAT_DELAY_MS=" + (KICK_REPEAT_TEST_DELAY if repeat_off
                                           else KICK_REPEAT_DEFAULT)]
@@ -3724,7 +3738,8 @@ def test_no_args_opens_terminal():
         log = _fresh_log()
         dump_dir = _mk_dump_dir()
         proc = subprocess.Popen(
-            ["env", "KICK_LOG=2", "KICK_SYNTH_INPUT=1",
+            ["env"] + _NESTED_ENV_STRIP + [
+             "KICK_LOG=2", "KICK_SYNTH_INPUT=1",
              f"TERMINAL={WL} '{RED}'", "KICK_DUMP_DIR=" + dump_dir,
              "KICK_REPEAT_DELAY_MS=" + KICK_REPEAT_TEST_DELAY,
              "stdbuf", "-oL", BIN],