diff --git a/esphome/espidf/size_summary.py b/esphome/espidf/size_summary.py
index 2be3634c69..572e2b0eff 100644
--- a/esphome/espidf/size_summary.py
+++ b/esphome/espidf/size_summary.py
@@ -73,15 +73,16 @@ def print_summary(size_json: Path, partitions_csv: Path | None) -> None:
     """Print PlatformIO-shaped RAM and Flash one-liners.
 
     Failures are non-fatal: the build has already succeeded, we just couldn't
-    summarize. Logs the cause at debug level.
+    summarize. Logs the cause at warning level, so a missing RAM/Flash line
+    (which CI's memory-impact extraction greps for) is diagnosable.
     """
     if not size_json.is_file():
-        _LOGGER.debug("Skipping size summary: %s not found", size_json)
+        _LOGGER.warning("Skipping size summary: %s not found", size_json)
         return
     try:
         data = json.loads(size_json.read_text(encoding="utf-8"))
     except (OSError, json.JSONDecodeError) as e:
-        _LOGGER.debug("Skipping size summary: %s", e)
+        _LOGGER.warning("Skipping size summary: %s", e)
         return
 
     memory_types = data.get("memory_types", {})
@@ -90,6 +91,8 @@ def print_summary(size_json: Path, partitions_csv: Path | None) -> None:
     ram_total = ram_region.get("size")
     if ram_total and ram_used is not None:
         print_size_line("RAM", ram_used, ram_total)
+    else:
+        _LOGGER.warning("Skipping RAM summary: no DRAM/DIRAM region in %s", size_json)
 
     image_size = data.get("image_size")
     if image_size is None or partitions_csv is None:
@@ -97,6 +100,6 @@ def print_summary(size_json: Path, partitions_csv: Path | None) -> None:
     try:
         app_size = _find_app_partition_size(partitions_csv)
     except ValueError as e:
-        _LOGGER.debug("Skipping Flash summary: %s", e)
+        _LOGGER.warning("Skipping Flash summary: %s", e)
         return
     print_size_line("Flash", image_size, app_size)
diff --git a/esphome/platformio/extra_script.py b/esphome/platformio/extra_script.py
index ef75421671..6b21100031 100644
--- a/esphome/platformio/extra_script.py
+++ b/esphome/platformio/extra_script.py
@@ -173,9 +173,9 @@ def run_extra_script(
     process CWD so relative-path lookups (``join``, ``realpath``,
     ``open``) resolve against the library tree.
 
-    On any exception inside the script we log at debug level and return
-    an empty result — extra-scripts are best-effort, and an unsupported
-    script shouldn't block the build.
+    On any exception inside the script we warn and return whatever the
+    script captured before failing — extra-scripts are best-effort, and an
+    unsupported script shouldn't block the build.
     """
     env = _FakeSConsEnv(
         board_mcu=board_mcu,
@@ -196,8 +196,15 @@ def run_extra_script(
             },
         )
     except Exception as e:  # noqa: BLE001  # pylint: disable=broad-exception-caught
-        _LOGGER.warning("PIO extra-script %s raised %s; skipping", script_path, e)
-        return ExtraScriptResult()
+        # Keep what the script captured before failing: dropping flags it
+        # already appended would fail later at link time, far from the cause
+        _LOGGER.warning(
+            "PIO extra-script %s (in %s) raised %s; keeping the partial capture",
+            script_path,
+            library_dir.name,
+            e,
+        )
+        return env.result
     finally:
         os.chdir(old_cwd)
     return env.result
diff --git a/esphome/platformio/library.py b/esphome/platformio/library.py
index 22da9cfc87..e347e1a901 100644
--- a/esphome/platformio/library.py
+++ b/esphome/platformio/library.py
@@ -564,7 +564,9 @@ def split_flag_entry(entry: str, owner: str) -> list[str]:
     """``shlex.split`` with a clean error naming the offending flags entry."""
     try:
         return shlex.split(entry)
-    except ValueError as err:
+    except (ValueError, AttributeError, TypeError) as err:
+        # AttributeError/TypeError: a dict or number from a third-party
+        # manifest; name the entry instead of an opaque shlex traceback
         raise EsphomeError(f"Malformed build flag {entry!r} in {owner}: {err}") from err
 
 
diff --git a/tests/unit_tests/test_platformio_extra_script.py b/tests/unit_tests/test_platformio_extra_script.py
index 1cc9413679..ec62b67f08 100644
--- a/tests/unit_tests/test_platformio_extra_script.py
+++ b/tests/unit_tests/test_platformio_extra_script.py
@@ -224,7 +224,7 @@ def test_apply_extra_script_swallows_script_errors(tmp_path, caplog) -> None:
     c.data = {"build": {"extraScript": "extra.py"}}
     apply_extra_script(c, board_mcu=lambda: "esp8266", pio_platform="espressif8266")
     assert "flags" not in c.data["build"]
-    assert "skipping" in caplog.text
+    assert "keeping the partial capture" in caplog.text
 
 
 def test_apply_extra_script_pio_platform(tmp_path) -> None:
@@ -250,3 +250,16 @@ def test_apply_extra_script_missing_script_logged(tmp_path, caplog) -> None:
     c.data = {"build": {"extraScript": "nope.py"}}
     apply_extra_script(c, board_mcu=lambda: "esp8266", pio_platform="espressif8266")
     assert "not found" in caplog.text
+
+
+def test_run_extra_script_keeps_partial_capture(tmp_path, caplog) -> None:
+    """Flags appended before a script fails are kept, not dropped."""
+    from esphome.platformio.extra_script import run_extra_script
+
+    script = tmp_path / "extra.py"
+    script.write_text("env.Append(LIBS=['algobsec'])\nraise RuntimeError('boom')\n")
+    result = run_extra_script(
+        script, library_dir=tmp_path, board_mcu="esp32", pio_platform="espressif32"
+    )
+    assert result.libs == ["algobsec"]
+    assert "keeping the partial capture" in caplog.text
diff --git a/tests/unit_tests/test_platformio_library.py b/tests/unit_tests/test_platformio_library.py
index c8f994bb04..670f676902 100644
--- a/tests/unit_tests/test_platformio_library.py
+++ b/tests/unit_tests/test_platformio_library.py
@@ -564,3 +564,16 @@ def test_lex_build_flags_dangling_flag_does_not_cross_entries(
 
     assert lex_build_flags(["-Wall -I", "-DFOO=1"], "lib x") == ["-Wall", "-DFOO=1"]
     assert "Ignoring trailing '-I'" in caplog.text
+
+
+def test_split_flag_entry_non_string_is_clean(  # type: ignore[no-untyped-def]
+) -> None:
+    """A dict or number from a third-party manifest fails naming the entry,
+    not with an opaque shlex traceback."""
+    from esphome.core import EsphomeError
+    from esphome.platformio.library import split_flag_entry
+
+    with pytest.raises(EsphomeError, match="Malformed build flag"):
+        split_flag_entry({"esp32": ["-DX"]}, "lib x")
+    with pytest.raises(EsphomeError, match="Malformed build flag 5"):
+        split_flag_entry(5, "lib x")
diff --git a/tests/unit_tests/test_size_summary.py b/tests/unit_tests/test_size_summary.py
index 816e65be18..dc937147ad 100644
--- a/tests/unit_tests/test_size_summary.py
+++ b/tests/unit_tests/test_size_summary.py
@@ -149,3 +149,32 @@ def test_print_summary_flash_line(
     out = capsys.readouterr().out
     assert "RAM:   [=====     ]  50.0% (used 100 bytes from 200 bytes)" in out
     assert "Flash: [          ]   0.0% (used 500 bytes from 1048576 bytes)" in out
+
+
+def test_print_summary_missing_ram_region_warns(
+    tmp_path: Path, caplog: pytest.LogCaptureFixture
+) -> None:
+    """A missing RAM line is diagnosable, not a silently absent CI metric."""
+    size_json = _write_size_json(tmp_path, {"memory_types": {}, "image_size": 100})
+    print_summary(size_json, partitions_csv=None)
+    assert "Skipping RAM summary" in caplog.text
+
+
+def test_print_summary_bad_partitions_warns(
+    tmp_path: Path, caplog: pytest.LogCaptureFixture
+) -> None:
+    """An unparseable partition table skips the Flash line with a warning."""
+    size_json = _write_size_json(tmp_path, _esp32_size_data())
+    partitions = tmp_path / "partitions.csv"
+    partitions.write_text("not,a,valid,partition,table\n")
+    print_summary(size_json, partitions_csv=partitions)
+    assert "Skipping Flash summary" in caplog.text
+
+
+def test_print_summary_corrupt_json_warns(
+    tmp_path: Path, caplog: pytest.LogCaptureFixture
+) -> None:
+    size_json = tmp_path / "size.json"
+    size_json.write_text("{not json")
+    print_summary(size_json, partitions_csv=None)
+    assert "Skipping size summary" in caplog.text