diff --git a/test/backend/unit/test_espidf_core_first.py b/test/backend/unit/test_espidf_core_first.py
index 74f70bfe..10630528 100644
--- a/test/backend/unit/test_espidf_core_first.py
+++ b/test/backend/unit/test_espidf_core_first.py
@@ -67,12 +67,27 @@ class TestCoreFirstResolution(unittest.TestCase):
         self.assertIn("DHT.cpp", copied)
         self.assertEqual(hdr2comp.get("DHT.h"), "user_libs_all")
 
-    def test_arch_excluded_lib_skipped(self):
+    def test_arch_excluded_lib_two_tier_guard(self):
+        """Issue #257: the architecture guard is two-tier. A DIRECT sketch
+        include of an arch-excluded lib merges anyway (user intent; many
+        avr-declared libs are pure Wire code — a real compile error beats
+        'No such file'). A TRANSITIVE pull of an arch-excluded lib is still
+        skipped (the Adafruit_ZeroDMA poison path). And 'all' counts as
+        wildcard (LiquidCrystal_I2C 2.0.0 declares architectures=all)."""
         ulibs = self.tmp / "Arduino" / "libraries"
         _mk(ulibs / "AvrOnlyLib" / "library.properties",
             "name=AvrOnlyLib\narchitectures=avr\n")
         _mk(ulibs / "AvrOnlyLib" / "Foo.h")
         _mk(ulibs / "AvrOnlyLib" / "Foo.cpp")
+        # An 'all'-declared lib whose header pulls the avr-only one
+        # transitively: Bar.h -> #include <Foo2.h>.
+        _mk(ulibs / "AllArchLib" / "library.properties",
+            "name=AllArchLib\narchitectures=all\n")
+        _mk(ulibs / "AllArchLib" / "Bar.h", '#include <Foo2.h>\n')
+        _mk(ulibs / "AllArchLib" / "Bar.cpp")
+        _mk(ulibs / "AvrOnlyLib2" / "library.properties",
+            "name=AvrOnlyLib2\narchitectures=avr\n")
+        _mk(ulibs / "AvrOnlyLib2" / "Foo2.h")
 
         c = ESPIDFCompiler()
         c.arduino_path = ""           # no core path -> static fallback set
@@ -81,11 +96,16 @@ class TestCoreFirstResolution(unittest.TestCase):
         out.mkdir(parents=True)
 
         names, hdr2comp = c._resolve_library_components(
-            ["Foo.h"],
+            ["Foo.h", "Bar.h"],
             arduino_libs=ulibs, esp32_libs=None,
             arduino_comp_name="arduino-esp32", user_libs_dir=out,
         )
-        self.assertNotIn("Foo.h", hdr2comp)
+        # Direct include of the avr-only lib: merged anyway.
+        self.assertEqual(hdr2comp.get("Foo.h"), "user_libs_all")
+        # 'all' wildcard lib: merged.
+        self.assertEqual(hdr2comp.get("Bar.h"), "user_libs_all")
+        # Transitive pull (Foo2.h via Bar.h) of an avr-only lib: skipped.
+        self.assertNotIn("Foo2.h", hdr2comp)
 
 
 class TestManifestScope(unittest.TestCase):