diff --git a/src/schedTest.c b/src/schedTest.c
index 09ed3a1..5e6053e 100644
--- a/src/schedTest.c
+++ b/src/schedTest.c
@@ -1570,3 +1570,86 @@ KTEST(currentThreadEnvEntryExposesRawStorageForListing)
     KT_NULL(t, currentThreadEnvEntry(2));
     KT_NULL(t, currentThreadEnvEntry(-1));
 
+    threadAt(0)->envCount = 0;
+}
+
+/* currentThreadUnsetEnv (sched.h) -- real unsetenv(3): a no-op success on a
+   missing name, a real compacting removal on a present one (never just a
+   tombstone, since currentThreadEnvEntry's own index space must stay dense
+   for shell.c's `env` listing to keep working after a removal in the
+   middle). */
+KTEST(currentThreadUnsetEnvOnMissingNameIsNoOpSuccess)
+{
+    threadAt(0)->envCount = 0;
+
+    KT_TRUE(t, currentThreadSetEnv("FOO", "bar"));
+    KT_FALSE(t, currentThreadUnsetEnv("MISSING"));
+    KT_EQ(t, currentThreadEnvCount(), 1);
+    KT_STREQ(t, currentThreadGetEnv("FOO"), "bar");
+
+    threadAt(0)->envCount = 0;
+}
+
+KTEST(currentThreadUnsetEnvRemovesLastEntry)
+{
+    threadAt(0)->envCount = 0;
+
+    KT_TRUE(t, currentThreadSetEnv("A", "1"));
+    KT_TRUE(t, currentThreadSetEnv("B", "2"));
+    KT_TRUE(t, currentThreadUnsetEnv("B"));
+    KT_EQ(t, currentThreadEnvCount(), 1);
+    KT_STREQ(t, currentThreadGetEnv("A"), "1");
+    KT_NULL(t, currentThreadGetEnv("B"));
+
+    threadAt(0)->envCount = 0;
+}
+
+KTEST(currentThreadUnsetEnvCompactsMiddleEntryDown)
+{
+    threadAt(0)->envCount = 0;
+
+    /* Removing the MIDDLE of three entries must shift every LATER entry
+       down by one slot (memmove, not just marking a hole) -- otherwise
+       currentThreadEnvEntry(1) after this removal would either still show
+       the removed "B=2" or skip straight to garbage past envCount. */
+    KT_TRUE(t, currentThreadSetEnv("A", "1"));
+    KT_TRUE(t, currentThreadSetEnv("B", "2"));
+    KT_TRUE(t, currentThreadSetEnv("C", "3"));
+    KT_TRUE(t, currentThreadUnsetEnv("B"));
+
+    KT_EQ(t, currentThreadEnvCount(), 2);
+    KT_STREQ(t, currentThreadEnvEntry(0), "A=1");
+    KT_STREQ(t, currentThreadEnvEntry(1), "C=3");
+    KT_NULL(t, currentThreadEnvEntry(2));
+    KT_NULL(t, currentThreadGetEnv("B"));
+    KT_STREQ(t, currentThreadGetEnv("A"), "1");
+    KT_STREQ(t, currentThreadGetEnv("C"), "3");
+
+    threadAt(0)->envCount = 0;
+}
+
+KTEST(currentThreadUnsetEnvActuallyFreesSlotForReuse)
+{
+    threadAt(0)->envCount = 0;
+
+    /* Fill the table completely, remove one, then prove a genuinely NEW
+       name can now be set -- if unset only tombstoned the slot instead of
+       compacting envCount back down, this set would still see a "full"
+       table and fail. */
+    for (int i = 0; i < envMaxVars; i++) {
+        char name[8];
+        snprintf(name, sizeof(name), "V%d", i);
+        KT_TRUE(t, currentThreadSetEnv(name, "x"));
+    }
+    KT_EQ(t, currentThreadEnvCount(), envMaxVars);
+
+    KT_TRUE(t, currentThreadUnsetEnv("V0"));
+    KT_EQ(t, currentThreadEnvCount(), envMaxVars - 1);
+
+    KT_TRUE(t, currentThreadSetEnv("FRESH", "new"));
+    KT_EQ(t, currentThreadEnvCount(), envMaxVars);
+    KT_STREQ(t, currentThreadGetEnv("FRESH"), "new");
+    KT_NULL(t, currentThreadGetEnv("V0"));
+
+    threadAt(0)->envCount = 0;
+}