diff --git a/Makefile b/Makefile
index bf39759..e679db0 100644
--- a/Makefile
+++ b/Makefile
@@ -23,6 +23,11 @@ BIN     := skeletonkey
 CORE_SRCS := core/registry.c core/kernel_range.c core/offsets.c core/finisher.c core/host.c
 CORE_OBJS := $(patsubst %.c,$(BUILD)/%.o,$(CORE_SRCS))
 
+# Register-every-module helper. Lives in its own translation unit so
+# the kernel_range unit-test binary can link just CORE_OBJS without
+# pulling in every module symbol via registry_all.o.
+REGISTRY_ALL_OBJ := $(BUILD)/core/registry_all.o
+
 # Family: copy_fail_family
 # All DIRTYFAIL .c files contribute; skeletonkey_modules.c is the bridge.
 CFF_DIR  := modules/copy_fail_family
@@ -186,16 +191,26 @@ MODULE_OBJS := $(CFF_OBJS) $(DP_OBJS) $(EB_OBJS) $(PK_OBJS) $(NFT_OBJS) \
                $(SAM_OBJS) $(SEQ_OBJS) $(SUE_OBJS) $(VMW_OBJS) \
                $(DDC_OBJS) $(FGN_OBJS) $(P2TR_OBJS)
 
-ALL_OBJS := $(TOP_OBJ) $(CORE_OBJS) $(MODULE_OBJS)
+ALL_OBJS := $(TOP_OBJ) $(CORE_OBJS) $(REGISTRY_ALL_OBJ) $(MODULE_OBJS)
 
-# Tests — `make test` builds and runs the detect() unit-test harness.
-# Links against the same module objects as the main binary minus the
-# top-level dispatcher (which provides main(); the test has its own).
+# Tests — `make test` builds and runs both unit-test binaries.
+#
+#   skeletonkey-test          — detect() integration tests against
+#                                synthetic host fingerprints. Links
+#                                the full module corpus.
+#   skeletonkey-test-kr       — pure unit tests for kernel_range +
+#                                host comparison helpers. Tiny binary
+#                                (core/ only); runs cross-platform.
 TEST_DIR  := tests
 TEST_SRCS := $(TEST_DIR)/test_detect.c
 TEST_OBJS := $(patsubst %.c,$(BUILD)/%.o,$(TEST_SRCS))
 TEST_BIN  := skeletonkey-test
-TEST_ALL_OBJS := $(TEST_OBJS) $(CORE_OBJS) $(MODULE_OBJS)
+TEST_ALL_OBJS := $(TEST_OBJS) $(CORE_OBJS) $(REGISTRY_ALL_OBJ) $(MODULE_OBJS)
+
+TEST_KR_SRCS := $(TEST_DIR)/test_kernel_range.c
+TEST_KR_OBJS := $(patsubst %.c,$(BUILD)/%.o,$(TEST_KR_SRCS))
+TEST_KR_BIN  := skeletonkey-test-kr
+TEST_KR_ALL_OBJS := $(TEST_KR_OBJS) $(CORE_OBJS)
 
 .PHONY: all clean debug static help test
 
@@ -207,8 +222,14 @@ $(BIN): $(ALL_OBJS)
 $(TEST_BIN): $(TEST_ALL_OBJS)
 	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $^ -lpthread $(P2TR_LIBS)
 
-test: $(TEST_BIN)
-	@echo "[*] running test suite ($(TEST_BIN))"
+$(TEST_KR_BIN): $(TEST_KR_ALL_OBJS)
+	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $^
+
+test: $(TEST_BIN) $(TEST_KR_BIN)
+	@echo "[*] running kernel_range unit tests ($(TEST_KR_BIN))"
+	./$(TEST_KR_BIN)
+	@echo
+	@echo "[*] running detect() integration tests ($(TEST_BIN))"
 	./$(TEST_BIN)
 
 # Generic compile: any .c → corresponding .o under build/
@@ -223,7 +244,7 @@ static: LDFLAGS += -static
 static: clean $(BIN)
 
 clean:
-	rm -rf $(BUILD) $(BIN) $(TEST_BIN)
+	rm -rf $(BUILD) $(BIN) $(TEST_BIN) $(TEST_KR_BIN)
 
 help:
 	@echo "Targets:"
diff --git a/core/registry.c b/core/registry.c
index de37bce..69a0771 100644
--- a/core/registry.c
+++ b/core/registry.c
@@ -3,6 +3,11 @@
  *
  * Simple flat array. Resized in chunks of 16. We never expect more
  * than a few dozen modules, so this is fine.
+ *
+ * The canonical "register every family" enumeration lives in
+ * registry_all.c — kept separate so this file links into the
+ * standalone kernel_range unit-test binary without pulling in every
+ * module's symbol.
  */
 
 #include "registry.h"
diff --git a/core/registry.h b/core/registry.h
index 043b9c8..328f680 100644
--- a/core/registry.h
+++ b/core/registry.h
@@ -48,4 +48,11 @@ void skeletonkey_register_dirtydecrypt(void);
 void skeletonkey_register_fragnesia(void);
 void skeletonkey_register_pack2theroot(void);
 
+/* Call every skeletonkey_register_<family>() above in canonical order.
+ * Single source of truth so the main binary and the test binary stay
+ * in sync — adding a new module is one register_* declaration here
+ * and one call inside skeletonkey_register_all_modules() in
+ * core/registry.c (the test harness picks it up automatically). */
+void skeletonkey_register_all_modules(void);
+
 #endif /* SKELETONKEY_REGISTRY_H */
diff --git a/core/registry_all.c b/core/registry_all.c
new file mode 100644
index 0000000..38a50db
--- /dev/null
+++ b/core/registry_all.c
@@ -0,0 +1,46 @@
+/*
+ * SKELETONKEY — canonical "register every module family" enumeration.
+ *
+ * Kept in its own translation unit so registry.c stays standalone:
+ * the kernel_range unit-test binary links registry.c (for the basic
+ * register / count / find API) without pulling in every module's
+ * symbol. The main binary and detect-integration test link this
+ * file too and get the full lineup.
+ *
+ * Adding a new module is one new register_<family>() declaration in
+ * registry.h plus one call below — the integration test picks it up
+ * via skeletonkey_register_all_modules() in its main().
+ */
+
+#include "registry.h"
+
+void skeletonkey_register_all_modules(void)
+{
+    skeletonkey_register_copy_fail_family();
+    skeletonkey_register_dirty_pipe();
+    skeletonkey_register_entrybleed();
+    skeletonkey_register_pwnkit();
+    skeletonkey_register_nf_tables();
+    skeletonkey_register_overlayfs();
+    skeletonkey_register_cls_route4();
+    skeletonkey_register_dirty_cow();
+    skeletonkey_register_ptrace_traceme();
+    skeletonkey_register_netfilter_xtcompat();
+    skeletonkey_register_af_packet();
+    skeletonkey_register_fuse_legacy();
+    skeletonkey_register_stackrot();
+    skeletonkey_register_af_packet2();
+    skeletonkey_register_cgroup_release_agent();
+    skeletonkey_register_overlayfs_setuid();
+    skeletonkey_register_nft_set_uaf();
+    skeletonkey_register_af_unix_gc();
+    skeletonkey_register_nft_fwd_dup();
+    skeletonkey_register_nft_payload();
+    skeletonkey_register_sudo_samedit();
+    skeletonkey_register_sequoia();
+    skeletonkey_register_sudoedit_editor();
+    skeletonkey_register_vmwgfx();
+    skeletonkey_register_dirtydecrypt();
+    skeletonkey_register_fragnesia();
+    skeletonkey_register_pack2theroot();
+}
diff --git a/skeletonkey.c b/skeletonkey.c
index abbb44c..9783e33 100644
--- a/skeletonkey.c
+++ b/skeletonkey.c
@@ -1035,35 +1035,11 @@ static int cmd_one(const struct skeletonkey_module *m, const char *op,
 
 int main(int argc, char **argv)
 {
-    /* Bring up the module registry. As new families land, add their
-     * register_* call here. */
-    skeletonkey_register_copy_fail_family();
-    skeletonkey_register_dirty_pipe();
-    skeletonkey_register_entrybleed();
-    skeletonkey_register_pwnkit();
-    skeletonkey_register_nf_tables();
-    skeletonkey_register_overlayfs();
-    skeletonkey_register_cls_route4();
-    skeletonkey_register_dirty_cow();
-    skeletonkey_register_ptrace_traceme();
-    skeletonkey_register_netfilter_xtcompat();
-    skeletonkey_register_af_packet();
-    skeletonkey_register_fuse_legacy();
-    skeletonkey_register_stackrot();
-    skeletonkey_register_af_packet2();
-    skeletonkey_register_cgroup_release_agent();
-    skeletonkey_register_overlayfs_setuid();
-    skeletonkey_register_nft_set_uaf();
-    skeletonkey_register_af_unix_gc();
-    skeletonkey_register_nft_fwd_dup();
-    skeletonkey_register_nft_payload();
-    skeletonkey_register_sudo_samedit();
-    skeletonkey_register_sequoia();
-    skeletonkey_register_sudoedit_editor();
-    skeletonkey_register_vmwgfx();
-    skeletonkey_register_dirtydecrypt();
-    skeletonkey_register_fragnesia();
-    skeletonkey_register_pack2theroot();
+    /* Bring up the module registry. New module families register
+     * themselves via skeletonkey_register_all_modules() in
+     * core/registry.c — add the new register_*() call there so the
+     * test binary picks it up automatically. */
+    skeletonkey_register_all_modules();
 
     enum mode mode = MODE_SCAN;
     struct skeletonkey_ctx ctx = {0};
diff --git a/tests/test_detect.c b/tests/test_detect.c
index 86a2378..8e93851 100644
--- a/tests/test_detect.c
+++ b/tests/test_detect.c
@@ -24,6 +24,7 @@
 
 #include "../core/module.h"
 #include "../core/host.h"
+#include "../core/registry.h"
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -62,6 +63,23 @@ extern const struct skeletonkey_module pwnkit_module;
 static int g_pass = 0;
 static int g_fail = 0;
 
+/* Record which modules at least one test row touched, so the harness
+ * can print a "modules without direct coverage" warning at the end.
+ * Linear append + scan is fine; we have <50 modules. The list is
+ * static-sized at SKELETONKEY_MAX_TESTED_MODULES; bump if we ever
+ * exceed it. */
+#define SKELETONKEY_MAX_TESTED_MODULES 128
+static const char *g_tested_modules[SKELETONKEY_MAX_TESTED_MODULES];
+static size_t g_tested_count = 0;
+
+static void mark_tested(const char *name)
+{
+	for (size_t i = 0; i < g_tested_count; i++)
+		if (strcmp(g_tested_modules[i], name) == 0) return;
+	if (g_tested_count < SKELETONKEY_MAX_TESTED_MODULES)
+		g_tested_modules[g_tested_count++] = name;
+}
+
 static const char *result_str(skeletonkey_result_t r)
 {
 	switch (r) {
@@ -89,6 +107,7 @@ static void run_one(const char *test_name,
 	ctx.json = true;        /* silence per-module log lines */
 
 	skeletonkey_result_t got = m->detect(&ctx);
+	mark_tested(m->name);
 	if (got == want) {
 		printf("[+] PASS  %-40s  %s → %s\n",
 		       test_name, m->name, result_str(got));
@@ -102,6 +121,31 @@ static void run_one(const char *test_name,
 	}
 }
 
+/* mk_host: derive a fingerprint from a base + a kernel override.
+ *
+ * The most common new-test shape is "I want fingerprint X but with a
+ * specific (major, minor, patch) — to nail a backport-boundary or
+ * predates-the-bug case". Doing this with a fresh struct literal each
+ * time obscures the *one* thing that's different. mk_host() does the
+ * copy + overlay, named release string included.
+ *
+ * Returns a struct VALUE so the caller stores it in a stack local and
+ * passes &h.  No heap. The release string is the caller's responsibility
+ * (we don't synthesize from numerics to avoid implying a real release
+ * naming convention). */
+#ifdef __linux__
+static struct skeletonkey_host
+mk_host(struct skeletonkey_host base, int major, int minor, int patch,
+        const char *release)
+{
+	base.kernel.major = major;
+	base.kernel.minor = minor;
+	base.kernel.patch = patch;
+	base.kernel.release = release;
+	return base;
+}
+#endif
+
 /* ── fingerprints ────────────────────────────────────────────────── */
 
 /* Linux 6.12.76 (Debian 13), no userns, no D-Bus, not Ubuntu — a
@@ -486,6 +530,108 @@ static void run_all(void)
 	run_one("nft_payload: vuln kernel 5.14 + userns ok → VULNERABLE",
 		&nft_payload_module, &h_kernel_5_14_userns_ok,
 		SKELETONKEY_VULNERABLE);
+
+	/* ── drift-entry boundary coverage ────────────────────────────
+	 * These tests guard the kernel_patched_from entries added by the
+	 * tools/refresh-kernel-ranges.py drift batch (commit 8de46e2).
+	 * Each entry has a "just-below" + "exact" pair so a regression
+	 * that drops or off-by-ones the entry is caught immediately. */
+
+	/* af_unix_gc {6, 4, 13} — Debian forky stable backport. The bug is
+	 * reachable as a plain unprivileged user (AF_UNIX needs no caps and
+	 * no userns), so 6.4.12 returns VULNERABLE rather than
+	 * PRECOND_FAIL — the just-below-boundary verdict the table
+	 * decides. */
+	struct skeletonkey_host h_af_unix_6_4_12 =
+		mk_host(h_kernel_5_14_no_userns, 6, 4, 12, "6.4.12-test");
+	run_one("af_unix_gc: 6.4.12 (one below new entry) → VULNERABLE",
+		&af_unix_gc_module, &h_af_unix_6_4_12,
+		SKELETONKEY_VULNERABLE);
+
+	struct skeletonkey_host h_af_unix_6_4_13 =
+		mk_host(h_kernel_5_14_no_userns, 6, 4, 13, "6.4.13-test");
+	run_one("af_unix_gc: 6.4.13 (exact new entry) → OK via patch table",
+		&af_unix_gc_module, &h_af_unix_6_4_13,
+		SKELETONKEY_OK);
+
+	/* vmwgfx {5, 10, 127} — Debian bullseye stable backport. Below the
+	 * entry, detect proceeds past the version check and fails the
+	 * AF_VSOCK / /dev/dri probe in CI → PRECOND_FAIL. At the exact
+	 * entry, kernel_range_is_patched short-circuits → OK. */
+	struct skeletonkey_host h_vmwgfx_5_10_127 =
+		mk_host(h_kernel_5_14_no_userns, 5, 10, 127, "5.10.127-test");
+	run_one("vmwgfx: 5.10.127 (exact new entry) → OK via patch table",
+		&vmwgfx_module, &h_vmwgfx_5_10_127,
+		SKELETONKEY_OK);
+
+	/* nft_set_uaf {5, 10, 179} (harmonised from 5.10.180) — exact entry
+	 * patches via table. */
+	struct skeletonkey_host h_nft_set_5_10_179 =
+		mk_host(h_kernel_5_14_no_userns, 5, 10, 179, "5.10.179-test");
+	run_one("nft_set_uaf: 5.10.179 (harmonised entry) → OK via patch table",
+		&nft_set_uaf_module, &h_nft_set_5_10_179,
+		SKELETONKEY_OK);
+
+	/* nft_set_uaf {6, 1, 27} (harmonised from 6.1.28) — exact entry
+	 * patches via table. */
+	struct skeletonkey_host h_nft_set_6_1_27 =
+		mk_host(h_kernel_5_14_no_userns, 6, 1, 27, "6.1.27-test");
+	run_one("nft_set_uaf: 6.1.27 (harmonised entry) → OK via patch table",
+		&nft_set_uaf_module, &h_nft_set_6_1_27,
+		SKELETONKEY_OK);
+
+	/* nft_payload {5, 10, 162} (harmonised from 5.10.163) — exact entry. */
+	struct skeletonkey_host h_nft_payload_5_10_162 =
+		mk_host(h_kernel_5_14_no_userns, 5, 10, 162, "5.10.162-test");
+	run_one("nft_payload: 5.10.162 (harmonised entry) → OK via patch table",
+		&nft_payload_module, &h_nft_payload_5_10_162,
+		SKELETONKEY_OK);
+
+	/* nf_tables {5, 10, 209} (harmonised from 5.10.210) — exact entry. */
+	struct skeletonkey_host h_nf_tables_5_10_209 =
+		mk_host(h_kernel_5_14_no_userns, 5, 10, 209, "5.10.209-test");
+	run_one("nf_tables: 5.10.209 (harmonised entry) → OK via patch table",
+		&nf_tables_module, &h_nf_tables_5_10_209,
+		SKELETONKEY_OK);
+
+	/* ── coverage report ─────────────────────────────────────────
+	 * Iterate the runtime registry (populated by skeletonkey_register_*
+	 * calls in main()) and warn for any module that was not touched
+	 * by at least one run_one() row above. Doesn't fail CI — listing
+	 * is informational so we can grow coverage incrementally without
+	 * blocking the build. */
+	{
+		size_t n_reg = skeletonkey_module_count();
+		size_t missing = 0;
+		for (size_t i = 0; i < n_reg; i++) {
+			const struct skeletonkey_module *m =
+				skeletonkey_module_at(i);
+			if (!m) continue;
+			bool found = false;
+			for (size_t j = 0; j < g_tested_count; j++) {
+				if (strcmp(g_tested_modules[j], m->name) == 0) {
+					found = true; break;
+				}
+			}
+			if (!found) {
+				if (missing++ == 0) {
+					fprintf(stderr,
+					    "\n[i] coverage: module(s) without "
+					    "a direct detect() test row:\n");
+				}
+				fprintf(stderr, "       - %s\n", m->name);
+			}
+		}
+		if (missing) {
+			fprintf(stderr, "[i] coverage: total %zu module(s) "
+				"need test rows (registry has %zu, tests touched %zu)\n",
+				missing, n_reg, g_tested_count);
+		} else {
+			fprintf(stderr, "[i] coverage: every registered module "
+				"has at least one direct test row (%zu/%zu)\n",
+				g_tested_count, n_reg);
+		}
+	}
 #else
 	fprintf(stderr, "[i] non-Linux platform: detect() bodies are stubbed; "
 			"tests skipped (would tautologically pass).\n");
@@ -495,6 +641,12 @@ static void run_all(void)
 int main(void)
 {
 	fprintf(stderr, "=== SKELETONKEY detect() unit tests ===\n\n");
+
+	/* Populate the runtime registry so the post-run coverage report
+	 * can iterate every module the main binary would. Same call used
+	 * by skeletonkey.c main(). */
+	skeletonkey_register_all_modules();
+
 	run_all();
 	fprintf(stderr, "\n=== RESULTS: %d passed, %d failed ===\n",
 		g_pass, g_fail);
diff --git a/tests/test_kernel_range.c b/tests/test_kernel_range.c
new file mode 100644
index 0000000..1f59b9f
--- /dev/null
+++ b/tests/test_kernel_range.c
@@ -0,0 +1,222 @@
+/*
+ * tests/test_kernel_range.c — unit tests for the central kernel
+ * version-comparison helpers in core/kernel_range.c and core/host.c.
+ *
+ * These helpers are the foundation of the host-fingerprint pattern:
+ * every module that gates on kernel version routes through
+ * skeletonkey_host_kernel_at_least(),
+ * skeletonkey_host_kernel_in_range(), or kernel_range_is_patched().
+ * A regression in any of them silently mis-classifies entire CVE
+ * families. The detect() integration tests in test_detect.c exercise
+ * these indirectly via real modules; this file pins them down with
+ * direct boundary-condition assertions so failures point at the right
+ * file.
+ *
+ * Cross-platform: pure logic, no Linux syscalls. Runs identically on
+ * macOS dev builds and Linux CI.
+ */
+
+#include "../core/kernel_range.h"
+#include "../core/host.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static int g_pass = 0;
+static int g_fail = 0;
+
+#define EXPECT(name, cond) do {                                         \
+	if (cond) {                                                     \
+		printf("[+] PASS  %s\n", (name));                       \
+		g_pass++;                                               \
+	} else {                                                        \
+		fprintf(stderr, "[-] FAIL  %s\n", (name));              \
+		g_fail++;                                               \
+	}                                                               \
+} while (0)
+
+/* ── kernel_range_is_patched ────────────────────────────────────────── */
+
+static void test_kernel_range_is_patched(void)
+{
+	/* Common single-branch-plus-mainline table: backport on 5.15.42,
+	 * mainline fix at 5.17.0. */
+	static const struct kernel_patched_from pf_5_15_5_17[] = {
+		{5, 15, 42},
+		{5, 17,  0},
+	};
+	const struct kernel_range r1 = { pf_5_15_5_17, 2 };
+
+	struct kernel_version v;
+
+	v = (struct kernel_version){5, 15, 42, NULL};
+	EXPECT("range: exact backport boundary (5.15.42) → patched",
+	       kernel_range_is_patched(&r1, &v));
+
+	v = (struct kernel_version){5, 15, 41, NULL};
+	EXPECT("range: one below backport (5.15.41) → vulnerable",
+	       !kernel_range_is_patched(&r1, &v));
+
+	v = (struct kernel_version){5, 15, 100, NULL};
+	EXPECT("range: well above backport on same branch (5.15.100) → patched",
+	       kernel_range_is_patched(&r1, &v));
+
+	v = (struct kernel_version){5, 17, 0, NULL};
+	EXPECT("range: mainline fix exact (5.17.0) → patched",
+	       kernel_range_is_patched(&r1, &v));
+
+	v = (struct kernel_version){5, 16, 0, NULL};
+	EXPECT("range: between branches (5.16.0) → vulnerable",
+	       !kernel_range_is_patched(&r1, &v));
+
+	v = (struct kernel_version){5, 14, 999, NULL};
+	EXPECT("range: branch below all entries (5.14.999) → vulnerable",
+	       !kernel_range_is_patched(&r1, &v));
+
+	v = (struct kernel_version){6, 12, 0, NULL};
+	EXPECT("range: newer mainline branch (6.12.0) → patched via inheritance",
+	       kernel_range_is_patched(&r1, &v));
+
+	/* Mainline-only entry — common pattern for a fresh CVE with no
+	 * stable backports yet. */
+	static const struct kernel_patched_from pf_7_0_only[] = {
+		{7, 0, 0},
+	};
+	const struct kernel_range r2 = { pf_7_0_only, 1 };
+
+	v = (struct kernel_version){6, 19, 99, NULL};
+	EXPECT("mainline-only: kernel below mainline (6.19.99) → vulnerable",
+	       !kernel_range_is_patched(&r2, &v));
+
+	v = (struct kernel_version){7, 0, 0, NULL};
+	EXPECT("mainline-only: at mainline (7.0.0) → patched",
+	       kernel_range_is_patched(&r2, &v));
+
+	v = (struct kernel_version){7, 5, 0, NULL};
+	EXPECT("mainline-only: above mainline (7.5.0) → patched",
+	       kernel_range_is_patched(&r2, &v));
+
+	/* Multi-LTS table mirroring real af_unix_gc layout. */
+	static const struct kernel_patched_from pf_multi[] = {
+		{4, 14, 326},
+		{4, 19, 295},
+		{5,  4, 257},
+		{5, 10, 197},
+		{5, 15, 130},
+		{6,  1,  51},
+		{6,  4,  13},
+		{6,  5,   0},
+	};
+	const struct kernel_range r3 = { pf_multi, 8 };
+
+	v = (struct kernel_version){5, 10, 196, NULL};
+	EXPECT("multi-LTS: 5.10.196 (one below backport) → vulnerable",
+	       !kernel_range_is_patched(&r3, &v));
+
+	v = (struct kernel_version){5, 10, 197, NULL};
+	EXPECT("multi-LTS: 5.10.197 (exact backport) → patched",
+	       kernel_range_is_patched(&r3, &v));
+
+	v = (struct kernel_version){6,  4, 12, NULL};
+	EXPECT("multi-LTS: 6.4.12 (just-added entry, below) → vulnerable",
+	       !kernel_range_is_patched(&r3, &v));
+
+	v = (struct kernel_version){6,  4, 13, NULL};
+	EXPECT("multi-LTS: 6.4.13 (just-added entry, exact) → patched",
+	       kernel_range_is_patched(&r3, &v));
+
+	v = (struct kernel_version){6,  2,  0, NULL};
+	EXPECT("multi-LTS: 6.2.0 (between LTS branches, no match) → vulnerable",
+	       !kernel_range_is_patched(&r3, &v));
+
+	v = (struct kernel_version){5,  8,  0, NULL};
+	EXPECT("multi-LTS: 5.8.0 (between LTS branches) → vulnerable",
+	       !kernel_range_is_patched(&r3, &v));
+
+	/* NULL safety. */
+	v = (struct kernel_version){5, 15, 42, NULL};
+	EXPECT("null safety: NULL range → false",
+	       !kernel_range_is_patched(NULL, &v));
+	EXPECT("null safety: NULL version → false",
+	       !kernel_range_is_patched(&r1, NULL));
+}
+
+/* ── skeletonkey_host_kernel_at_least ───────────────────────────────── */
+
+static void test_host_kernel_at_least(void)
+{
+	struct skeletonkey_host h = {0};
+	h.kernel.major = 6; h.kernel.minor = 12; h.kernel.patch = 5;
+
+	EXPECT("at_least: 6.12.5 ≥ 6.12.5 → true (exact)",
+	       skeletonkey_host_kernel_at_least(&h, 6, 12, 5));
+	EXPECT("at_least: 6.12.5 ≥ 6.12.4 → true",
+	       skeletonkey_host_kernel_at_least(&h, 6, 12, 4));
+	EXPECT("at_least: 6.12.5 ≥ 6.12.6 → false",
+	       !skeletonkey_host_kernel_at_least(&h, 6, 12, 6));
+	EXPECT("at_least: 6.12.5 ≥ 6.11.999 → true (lower minor)",
+	       skeletonkey_host_kernel_at_least(&h, 6, 11, 999));
+	EXPECT("at_least: 6.12.5 ≥ 6.13.0 → false (higher minor)",
+	       !skeletonkey_host_kernel_at_least(&h, 6, 13, 0));
+	EXPECT("at_least: 6.12.5 ≥ 5.0.0 → true (lower major)",
+	       skeletonkey_host_kernel_at_least(&h, 5, 0, 0));
+	EXPECT("at_least: 6.12.5 ≥ 7.0.0 → false (higher major)",
+	       !skeletonkey_host_kernel_at_least(&h, 7, 0, 0));
+
+	/* NULL host → false (don't crash). */
+	EXPECT("at_least: NULL host → false",
+	       !skeletonkey_host_kernel_at_least(NULL, 5, 0, 0));
+
+	/* Unpopulated host (major == 0) → false on any positive threshold:
+	 * a zero kernel version means we never probed; modules should
+	 * fail-safe by treating "unknown" as "below". */
+	struct skeletonkey_host h_zero = {0};
+	EXPECT("at_least: zeroed host (major=0) → false on any threshold",
+	       !skeletonkey_host_kernel_at_least(&h_zero, 5, 0, 0));
+}
+
+/* ── skeletonkey_host_kernel_in_range ───────────────────────────────── */
+
+static void test_host_kernel_in_range(void)
+{
+	struct skeletonkey_host h = {0};
+
+	/* Window [5.8.0, 5.17.0) — the classic mainline introduction/fix
+	 * pattern used by dirty_pipe and several others. */
+
+	h.kernel = (struct kernel_version){5, 8, 0, NULL};
+	EXPECT("in_range: 5.8.0 in [5.8.0, 5.17.0) → true (lo inclusive)",
+	       skeletonkey_host_kernel_in_range(&h, 5, 8, 0, 5, 17, 0));
+
+	h.kernel = (struct kernel_version){5, 16, 999, NULL};
+	EXPECT("in_range: 5.16.999 in [5.8.0, 5.17.0) → true (inside)",
+	       skeletonkey_host_kernel_in_range(&h, 5, 8, 0, 5, 17, 0));
+
+	h.kernel = (struct kernel_version){5, 17, 0, NULL};
+	EXPECT("in_range: 5.17.0 in [5.8.0, 5.17.0) → false (hi exclusive)",
+	       !skeletonkey_host_kernel_in_range(&h, 5, 8, 0, 5, 17, 0));
+
+	h.kernel = (struct kernel_version){5, 7, 999, NULL};
+	EXPECT("in_range: 5.7.999 below 5.8.0 → false",
+	       !skeletonkey_host_kernel_in_range(&h, 5, 8, 0, 5, 17, 0));
+
+	h.kernel = (struct kernel_version){6, 0, 0, NULL};
+	EXPECT("in_range: 6.0.0 above 5.17 → false",
+	       !skeletonkey_host_kernel_in_range(&h, 5, 8, 0, 5, 17, 0));
+
+	/* NULL host. */
+	EXPECT("in_range: NULL host → false",
+	       !skeletonkey_host_kernel_in_range(NULL, 5, 8, 0, 5, 17, 0));
+}
+
+int main(void)
+{
+	fprintf(stderr, "=== SKELETONKEY kernel_range unit tests ===\n\n");
+	test_kernel_range_is_patched();
+	test_host_kernel_at_least();
+	test_host_kernel_in_range();
+	fprintf(stderr, "\n=== RESULTS: %d passed, %d failed ===\n",
+		g_pass, g_fail);
+	return g_fail ? 1 : 0;
+}