diff --git a/esphome/build_helpers/tools_cache.py b/esphome/build_helpers/tools_cache.py
index f23c859b34..e7193a8e2a 100644
--- a/esphome/build_helpers/tools_cache.py
+++ b/esphome/build_helpers/tools_cache.py
@@ -16,7 +16,11 @@ def tools_cache_path(env_var: str, subdir: str) -> Path:
     from esphome.helpers import get_str_env
 
     if prefix := get_str_env(env_var, "").strip():
+        # resolve(): symlinked prefixes otherwise trip idf.py's
+        # venv-mismatch warning on every build
         return Path(prefix).expanduser().resolve()
+    # appauthor=False keeps the Windows path short (no vendor segment);
+    # deep IDF trees run into MAX_PATH otherwise
     return (
         Path(platformdirs.user_cache_dir("esphome", appauthor=False)) / subdir
     ).resolve()
diff --git a/esphome/helpers.py b/esphome/helpers.py
index fe3c383f59..b926979e04 100644
--- a/esphome/helpers.py
+++ b/esphome/helpers.py
@@ -31,8 +31,9 @@ SockAddr = IPv4SockAddr | IPv6SockAddr
 
 _LOGGER = logging.getLogger(__name__)
 
-# cv.boolean's closed spelling tables; shared so env-knob parsers cannot
-# drift from what configs accept
+# cv.boolean's closed spelling tables, shared with the strict env-knob
+# parser (build_helpers.ccache.parse_enable_env). The legacy get_bool_env
+# below keeps its own laxer table for backward compatibility.
 TRUTHY_BOOL_STRINGS = frozenset({"true", "yes", "on", "enable"})
 FALSY_BOOL_STRINGS = frozenset({"false", "no", "off", "disable"})
 
diff --git a/esphome/platformio/registry.py b/esphome/platformio/registry.py
index d7c9a92a2c..c4b79f5c8e 100644
--- a/esphome/platformio/registry.py
+++ b/esphome/platformio/registry.py
@@ -211,8 +211,14 @@ def prefetch_packages(
         [(entry[0], _fetch(entry)) for entry in pending],
     )
     for name, err in failures:
-        # install_package retries this one itself, with a visible bar
-        _LOGGER.debug("Prefetch of %s failed: %s", name, err)
+        if isinstance(err, (EsphomeError, OSError)):
+            # Expected download failures: install_package retries this one
+            # itself, with a visible bar
+            _LOGGER.debug("Prefetch of %s failed: %s", name, err)
+        else:
+            # Anything else is a programming error that would otherwise
+            # become a permanent silent no-op
+            _LOGGER.warning("Prefetch of %s failed: %r", name, err)
 
 
 def install_package(
diff --git a/tests/unit_tests/test_platformio_registry.py b/tests/unit_tests/test_platformio_registry.py
index 3f2b739ca9..46409ba62e 100644
--- a/tests/unit_tests/test_platformio_registry.py
+++ b/tests/unit_tests/test_platformio_registry.py
@@ -625,3 +625,26 @@ def test_prefetch_packages_download_failure_is_debug(
     assert mock_download.call_count == 2
     assert "Prefetch of a failed" in caplog.text
     assert "Prefetch of b failed" in caplog.text
+
+
+def test_prefetch_packages_unexpected_failure_warns(
+    tmp_path: Path, caplog: pytest.LogCaptureFixture
+) -> None:
+    """A programming error (not a download failure) surfaces at WARNING
+    instead of becoming a permanent silent no-op."""
+    with (
+        patch.object(
+            registry, "download_with_resume", side_effect=TypeError("bad call")
+        ),
+        patch.object(
+            registry, "registry_download", side_effect=_resolve_for({"a": 10, "b": 20})
+        ),
+    ):
+        registry.prefetch_packages(
+            [
+                ("a", "1.0", tmp_path / "a", []),
+                ("b", "2.0", tmp_path / "b", []),
+            ],
+            tmp_path / "dl",
+        )
+    assert "TypeError" in caplog.text