diff --git a/esphome/components/zephyr/library.py b/esphome/components/zephyr/library.py
index b339ae45b0..d09f0afedb 100644
--- a/esphome/components/zephyr/library.py
+++ b/esphome/components/zephyr/library.py
@@ -39,11 +39,13 @@ ZEPHYR_FRAMEWORK = "zephyr"
 
 
 def _escape(p: PathType) -> str:
-    # In CMakeLists.txt, backslashes need to be escaped (mirrors the ESP-IDF
-    # backend's escape_entry). Doubling -- rather than rewriting '\' -> '/' --
-    # preserves content, so it's safe for arbitrary build flags (e.g. a -D value
-    # containing a backslash) as well as Windows paths.
-    return f'"{str(p)}"'.replace("\\", "\\\\")
+    # In CMakeLists.txt, backslashes and embedded quotes need escaping
+    # (mirrors the ESP-IDF backend's escape_entry; the lex round-trip makes
+    # a literal quote in a -D value reachable). Doubling backslashes --
+    # rather than rewriting '\' -> '/' -- preserves content, so it's safe
+    # for arbitrary build flags as well as Windows paths.
+    escaped = str(p).replace("\\", "\\\\").replace('"', '\\"')
+    return f'"{escaped}"'
 
 
 def generate_module_yml(component: ConvertedLibrary) -> str:
diff --git a/esphome/platformio/library.py b/esphome/platformio/library.py
index 521337ff84..6c36abcb49 100644
--- a/esphome/platformio/library.py
+++ b/esphome/platformio/library.py
@@ -714,6 +714,10 @@ def normalize_dependencies(
     list, and a plain (possibly comma-separated) string; normalize them all
     so callers see a uniform list. ``manifest_name`` names the manifest in the
     warning for entries that cannot be normalized.
+
+    Bare-name spellings carry no version; the dependency walk later drops
+    version-less entries at DEBUG, since they are usually names of bundled
+    framework libraries (Wire, SPI) that need no registry install.
     """
     if dependencies is None:
         return []
@@ -1133,15 +1137,25 @@ def convert_libraries(
             malformed = not isinstance(component.data, dict)
             if not malformed:
                 build = component.data.get("build", {})
+                esphome_data = component.data.get(ESPHOME_DATA_KEY, {})
                 malformed = (
                     not isinstance(build, dict)
-                    or not isinstance(component.data.get(ESPHOME_DATA_KEY, {}), dict)
+                    or not isinstance(esphome_data, dict)
+                    or not isinstance(
+                        esphome_data.get(ESPHOME_DATA_LINK_FLAGS_KEY, []), list
+                    )
                     or not isinstance(build.get("srcDir", ""), str)
                     or not isinstance(build.get("includeDir", ""), str)
                     or not isinstance(build.get("srcFilter", ""), (str, list))
                 )
             if malformed:
-                raise EsphomeError(f"Library {key} has a malformed manifest")
+                # Fail fast only for a library the user asked for; a defect
+                # in an unrequested corner of the graph must not block the
+                # build
+                if key in top_level_keys:
+                    raise EsphomeError(f"Library {key} has a malformed manifest")
+                _LOGGER.warning("Skipping dependency %s: malformed manifest", key)
+                continue
             warn_properties_depends(component.name, component.data)
 
             try:
diff --git a/tests/unit_tests/test_platformio_library.py b/tests/unit_tests/test_platformio_library.py
index a565229bb1..ef24f99953 100644
--- a/tests/unit_tests/test_platformio_library.py
+++ b/tests/unit_tests/test_platformio_library.py
@@ -826,6 +826,7 @@ def test_normalize_dependencies_forms(caplog) -> None:
         {"name": "A", "build": {"srcDir": 123}},
         {"name": "A", "build": {"includeDir": ["inc"]}},
         {"name": "A", "build": {"srcFilter": {"+": "src"}}},
+        {"name": "A", "ESPHOME": {"LINK_FLAGS": "-Wl,-x"}},
     ],
 )
 def test_convert_libraries_malformed_manifest_raises(
@@ -838,6 +839,29 @@ def test_convert_libraries_malformed_manifest_raises(
         convert_libraries([Library("esphome/A", None, None)], _backend())
 
 
+def test_convert_libraries_malformed_transitive_dep_skips(
+    tmp_path, monkeypatch, caplog: pytest.LogCaptureFixture
+) -> None:
+    """A malformed manifest on a dependency the user never asked for warns
+    and skips; only a top-level library fails the build."""
+    _patch_download_with_manifests(
+        monkeypatch,
+        tmp_path,
+        {
+            "esphome/A": {
+                "name": "A",
+                "dependencies": [{"name": "B", "owner": "esphome", "version": "1.0"}],
+            },
+            "esphome/B": {"name": "B", "build": {"srcDir": 123}},
+        },
+    )
+    components = convert_libraries([Library("esphome/A", None, None)], _backend())
+    names = [c.name for c in components]
+    assert "esphome/A" in names
+    assert "esphome/B" not in names
+    assert "Skipping dependency esphome/B: malformed manifest" in caplog.text
+
+
 def test_walk_warns_for_properties_only_depends(
     tmp_path, monkeypatch, caplog: pytest.LogCaptureFixture
 ) -> None:
diff --git a/tests/unit_tests/test_zephyr_library.py b/tests/unit_tests/test_zephyr_library.py
index 0d899ec91d..765e505c38 100644
--- a/tests/unit_tests/test_zephyr_library.py
+++ b/tests/unit_tests/test_zephyr_library.py
@@ -66,6 +66,18 @@ def test_generate_cmakelists_txt_flags_and_includes(tmp_path):
     assert "-lm" in out
 
 
+def test_generate_cmakelists_txt_escapes_embedded_quotes(tmp_path):
+    """A define value carrying a literal quote (reachable via the lex
+    round-trip) survives as an escaped quote, not a broken CMake string."""
+    c = _make_component(tmp_path)
+    (tmp_path / "src").mkdir()
+    (tmp_path / "src" / "a.c").write_text("")
+    c.data = {"build": {"flags": ['-DMSG=\\"hi\\"']}}
+
+    out = generate_cmakelists_txt(c)
+    assert '"-DMSG=\\"hi\\""' in out
+
+
 def test_generate_cmakelists_txt_lexes_spaced_flags(tmp_path):
     """A spaced -I entry routes to include dirs instead of landing verbatim
     in compile options; same shared lexer as the espidf emitter."""